U.S. Department of 

Transportation 

Technical Study

DOT/FRA/ORD-05/03 March 2006 

DOT-VNTSC-FRA-05-06 

This document is available to the 

U.S. public through the National 

Technical Information Service, 

Springfield, VA 22161 and at 

www.fra.dot.gov 

Office of Research 

and Development 

Washington, DC 20590 

Federal Railroad 

Administration 

Comparative Safety of the Transport 

of High-Level Radioactive Materials 

on Dedicated, Key, and Regular Trains
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1. AGENCY USE ONLY (Leave 

blank)

2. REPORT DATE 

March 2006

3. REPORT TYPE & DATES 

COVERED DRAFT

4. TITLE AND SUBTITLE 

Comparative Safety of the Transport of High-Level Radioactive Materials on Dedicated, Key, and 

Regular Trains

6. AUTHOR(S) 

Borener, Sherry; Baker, Gary; Hitz, John; Meltzer, Neil; Talamini, Brandon; Coltman, Michael (Volpe 

Center); Haines, Marsha (EG&G Technical Services)

5. FUNDING NUMBERS 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

U.S. Department of Transportation 

Research and Special Programs Administration 

John A. Volpe National Transportation Systems Center 

Accident Prevention Division (DTS-73) 

55 Broadway, Kendall Square 

Cambridge, MA 02142

8. PERFORMING 

 ORGANIZATION REPORT 

 NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

U.S. Department of Transportation 

Federal Railroad Administration 

Washington, DC 20005

10. SPONSORING OR 

MONITORING AGENCY 

REPORT NUMBER 

DOT/FRA/ORD-05/03

11. SUPPLEMENTARY NOTES: 

12a. DISTRIBUTION/AVAILABILITY 12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words) 

This study compares the risks in transporting spent nuclear fuel and high-level radioactive waste under three rail shipment alternatives: 1) regular train service, 

operating without restrictions with the exception of current hazardous materials regulations; 2) dedicated train service, operating with consist and operational 

restrictions; and 3) key train service, similar to regular train service with the additional speed limitation of 50 mph. Dedicated train shipments have a lower 

overall radioactivity exposure risk during incident-free transport than shipments by regular or key trains; the advantage is primarily derived from the differences 

in the duration and frequency of yard visits, which account for a significant portion of total exposure for impacted populations. Crew population doses, however, 

are higher for dedicated trains because of crews working closer to the cask. Estimated population group exposures are low and do not include any additional 

protective measures, which may be implemented to mitigate exposure. 

The accident analysis estimated the difference in accident probability between dedicated, regular, and key trains, and it identified two significant risks potentially 

impacting the cask—high-speed collisions and derailments, and long duration, high-temperature HAZMAT-involved fires. The analysis shows that speed 

restrictions reduce collision probability at high speeds and result in an overall reduction in the derailment rate. Dedicated trains reduce the likelihood of hightemperature fires due to lessened exposure to other hazardous material. The risk for loss of shielding accidents is shown to be lower for the shorter dedicated 

trains due to the decreased number of potentially derailed cars.

15. NUMBER OF PAGES

196 

14. SUBJECT TERMS 

Spent nuclear fuel, high-level radioactive waste, HAZMAT.

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ABSTRACT 

NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) 

Prescribed by ANSI Std. 239-18 

298-102

i 
ii 
Table of Contents 

List of Figures................................................................................................................................................... v 

List of Tables ....................................................................................................................................................vii 

Preface............................................................................................................................................................... ix 

Acknowledgements........................................................................................................................................... xi 

Executive Summary ........................................................................................................................................ 1 

1. Introduction..........................................................................................................................................17 

1.1 Purpose.................................................................................................................................................17 

1.2 Background..........................................................................................................................................17 

1.3 Definitions of Spent Nuclear Fuel and High Level Radioactive Waste...............................................18 

1.4 Past and Future SNF Shipments ..........................................................................................................20 

1.5 Previous Research................................................................................................................................26 

1.6 Methodology........................................................................................................................................30 

1.7 Report Overview..................................................................................................................................31 

2. Incident-Free Risk Analysis.................................................................................................................33 

2.1 Incident-Free Risk Methodology–Radiological Consequences and Risk Calculations.......................33 

2.2 Incident-Free Results ...........................................................................................................................44 

3 Accident Risk Analysis........................................................................................................................63 

3.1 Methodology........................................................................................................................................64 

3.2 Accident Severity Factors....................................................................................................................66 

3.3 Accident Severity and Probabilities.....................................................................................................78 

3.4 Modified Event Tree–Dedicated Trains...............................................................................................89 

3.5 Modified Event Tree for Dedicated Trains–Results ............................................................................98 

3.6 Effect of AAR Circular No. OT-55-D Recommended Railroad Operating Practices for 

Transportation of Hazardous Materials................................................................................................101 

3.7 Relative Accident Consequences.........................................................................................................104 

4 Conclusions........................................................................................................................................ 119 

4.1 Incident-Free Radiological Risk ........................................................................................................ 119 

4.2 Accident Analysis .............................................................................................................................. 119 

4.3 Summary............................................................................................................................................ 123 

iii 
Bibliography ................................................................................................................................................... 125 

Appendix A. AAR Circular OT-55-D–Recommended Practices for Transportation of Hazardous 

Materials ............................................................................................................................... A-1 

Appendix B. Dedicated Train Workshop Notes on Stakeholder Positions ............................................... B-1 

Appendix C. Reported Incidents Involving Spent Nuclear Fuel Shipments 1949 to 2002........................ C-1 

Appendix D. Route Specific Analysis........................................................................................................ D-1 

Appendix E. Rail Transport of High-Level Radioactive Material ..............................................................E-1 

Appendix F. Current and Planned High-Speed Rail Corridors and Power Plants......................................F-1 

Appendix G. Energy Absorption Analysis ................................................................................................ G-1 

Acronyms and Abbreviations ......................................................................................................................... 173 

Glossary .............................................................................................................................................. 175 

iv 
List of Figures 

Figure 1. Comparison of Incident-Free Exposure Rate versus Other Common Exposures ......................14 

Figure 2. Cask Systems–DOE Multi-Purpose Canister (MPC) and Mitsubishi Dual Purpose Cask ........19 

Figure 3. MPC and Overpack....................................................................................................................19 

Figure 4. SNF Shipment Locations ...........................................................................................................21 

Figure 5. Incident-Free Risk Calculation ..................................................................................................33 

Figure 6. Selected SNF Shipment Routes .................................................................................................35 

Figure 7. Train Consist ..............................................................................................................................36 

Figure 8. Population Density Selection .....................................................................................................38 

Figure 9. Population Distance from Source...............................................................................................40 

Figure 10. Passing Train Distance...............................................................................................................41 

Figure 11. Total Dose–All Populations by Route, Service Type, and Speed..............................................46 

Figure 12. General Population Dose............................................................................................................49 

Figure 13. Train Passenger On-Link Dose ..................................................................................................51 

Figure 14. Dose to All Vehicle Occupants at Grade Crossings by Route and Weighted Average Speed...53 

Figure 15. Inspector/Classification Yard Worker Dose ..............................................................................55 

Figure 16. General Rail Yard Worker (Non-Classification) Dose ..............................................................56 

Figure 17. Comparison of Incident-Free Exposure Rate versus Other Common Exposures ......................57 

Figure 18. Latent Cancer Fatalities by Route, Service Type, and Speed ....................................................60 

Figure 19. Comparison of Single and Double Cask Shipment Dose–Route 6 ............................................61 

Figure 20. Accident Risk Analysis Methodology Flow Diagram ...............................................................65 

Figure 21. Cask Design Tests......................................................................................................................66 

Figure 22. Conceptual Design of a Generic Steel-Lead-Steel Rail Cask ....................................................67 

Figure 23. Force Crush Characteristic of Generic Steel-Lead-Steel Rail Transport Cask for Three 

Impact Orientations at 30 mph into a Rigid Surface..................................................................68 

Figure 24. Schematic of Front End of Freight Locomotive.........................................................................69 

Figure 25. Force Crush Characteristic for Generic Freight Locomotive.....................................................70 

Figure 26. Comparison of Force Crush Characteristics: Generic Rail SNF Transport Cask and Typical 

Locomotive ................................................................................................................................71 

Figure 27. Collision Dynamics Model ........................................................................................................73 

Figure 28. Schematic of Head-On Collision Scenario Between SNF Cask and Freight Locomotive.........73 

Figure 29. Schematic of Rail-Rail Crossing Collision Scenario .................................................................75 

Figure 30. Schematic of Raking Collision Scenario....................................................................................76 

Figure 31. Main-Line Event Tree................................................................................................................83 

Figure 32. Yard Event Tree .........................................................................................................................84 

v 
Figure 33. Fire Event Tree...........................................................................................................................88 

Figure 34. Humboldt, CA, to Yucca, NV, Rail Route Illustrating Accident Locations (1988-1997) .........91 

Figure 35. Train Simulation of Railcar Forces Under Emergency Brake Application–50 mph (80.4 

km/hr).........................................................................................................................................93 

Figure 36. Fraction of Total Number of Cars in Consist Derailed in Derailment-Only Accidents (1988-

2001) ..........................................................................................................................................95 

Figure 37. Fraction of Total Number of Cars in Consist Derailed in Collision-Related Derailments 

(1988-2001)................................................................................................................................96 

Figure 38. Average Number of Cars Derailed in All Derailments by Train Length (1988-2001) 

(Derailment Only and Collision-Related Derailments)..............................................................96 

Figure 39. Average Number of Cars Derailed by Train Speed (1998-2001) (Derailment Only and 

Collision-Related Derailments)..................................................................................................97 

Figure 40. Modified Event Tree–Dedicated Trains on Mainline ................................................................100 

Figure 41. Loss of Shielding Dose to General Population–Category II and Category III Events...............112 

Figure 42. Total Dose for Category II and III LOS Events.........................................................................114 

Figure 43. Dose–10 Hour Delay..................................................................................................................115 

Figure 44. Total Dose for Category I, II, and III Events .............................................................................116 

Figure 45. Comparative Risk Per Million Train Miles of Regular, Dedicated, and Key Trains by 

Mainline and Yard Accident Rates ............................................................................................122

Figure 46. Comparative Risk Per Million Train Miles of Regular, Dedicated, and Key Trains by 

Accident Type............................................................................................................................122 

vi 
List of Tables 

Table 1. Routes Used in the Analysis..........................................................................................................8 

Table 2. Comparison of General Freight and Dedicated Train Service.......................................................29 

Table 3. Routes Used in the Analysis..........................................................................................................34 

Table 4. Impacted Population Groups .........................................................................................................37 

Table 5. Average Population Density..........................................................................................................38 

Table 6. Average Passenger Train Density .................................................................................................38 

Table 7. Values for Occupants at Grade Crossing Dose Calculation ..........................................................39 

Table 8. Distance and Average Weighted Speed by Route.........................................................................42 

Table 9. Number and Duration of Yard Entries ..........................................................................................43 

Table 10. Number of Non-Classification Stops.............................................................................................43 

Table 11. Shielding Factor (Attenuation)......................................................................................................44 

Table 12. In-Transit and Stop Doses (Person-Rem) for All Populations ......................................................45 

Table 13. In-Transit Dose by Population Type (Person-Rem)......................................................................47 

Table 14. Stop Dose by Population Type (Person-Rem)...............................................................................48 

Table 15. General Population Dose...............................................................................................................50 

Table 16. Train Passenger On-Link Dose .....................................................................................................52 

Table 17. Total Dose to Vehicle Occupants at Grade Crossings...................................................................53 

Table 18. In-Transit and Stop Dose to Train Crew and Escorts (Person-Rem).............................................54 

Table 19. Incident-Free Transportation LCFs ...............................................................................................59 

Table 20. Average LCFs–Single and Double Cask Movements–Route 6.....................................................61 

Table 21. Residual Speeds for Various Simplified Head-On Collision Scenarios........................................74 

Table 22. Residual Speeds for Various Simplified Rail-Rail Crossing Collision Scenarios.........................75 

Table 23. Residual Speeds for Various Simplified Raking/Corner Collision Scenarios...............................76 

Table 24. Impact Speeds (MPH) Onto Real Yielding Surfaces–Type B Steel-Lead-Steel Spent Fuel Rail 

Cask...............................................................................................................................................77 

Table 25. Reported Train Accidents 1988-2001 ...........................................................................................79 

Table 26. Reported Train Miles.....................................................................................................................80 

Table 27. Accident Scenarios and Equivalent Velocities for the NRC Compliance Test .............................80 

Table 28. Adjustments to Baseline Accident Rate for Dedicated Train Service...........................................90 

Table 29. Speed Distribution of Mainline Accidents (1988-2001) ...............................................................94

Table 30. Regular versus Dedicated Train Results–Probability per Train Mile............................................99 

Table 31. Assumptions for Service Type–Key Train....................................................................................102 

Table 32. Regular Train versus Key Train Results–Probability per Train Mile ...........................................103 

Table 33. Regular Train versus Dedicated versus Key Train Results–Probability per Train Mile ...............104 

vii 
Table 34. Average General Population Density for All Routes .................................................................. 106 

Table 35. General Population Densities for LOS Scenarios........................................................................ 107 

Table 36. LOS Emergency Response Personnel–Distance ......................................................................... 108 

Table 37. LOS Emergency Response Personnel–Duration ......................................................................... 109 

Table 38. LOS General Population–Density, Duration, Distance and Shielding........................................ 110 

Table 39. Range of Dose/LCF for General Population LOS Events........................................................... 111 

Table 40. Range of Dose for Rail Worker/Emergency Responder–Single Person Dose (Rem)–Category 

II LOS Event ............................................................................................................................... 113 

Table 41. LOS Incident Consequences for Hypothetical Category II and III Events ................................. 113 

Table 42. Summary of LCF Consequences–Delay/LOS Incidents ............................................................. 117 

Table 43. Comparison of Accident Rates for Regular, Dedicated, and Key Trains.................................... 121 

viii 
Preface 

This study was undertaken to fulfill the requirements of the Hazardous Materials Transportation Uniform 

Safety Act of 1990, which required a comparative analysis of the safety of using dedicated versus regular 

trains for the shipment of spent fuel. As directed by the Congress, the Federal Railroad Administration 

(FRA) consulted with its major stakeholders at the onset of this study; stakeholders’ concerns were 

included in the construction of the analytical framework employed in this study. This report documents 

the results of that study, conducted by the Volpe National Transportation Systems Center, for the FRA of 

the U.S. Department of Transportation (DOT). 

Several Federal agencies are involved in spent fuel transportation, most notably the U.S. Department of 

Energy, the U.S. Nuclear Regulatory Commission, and the DOT. These agencies have provided input 

into this analysis, including identifying probable shipment routes, published information on likely 

material characteristics and volumes, and scientific data on the behavior of the transportation cask. 

Sandia National Laboratories contributed assistance in the construction of simulations to estimate 

population effects of shipments using the RADTRAN software program. Other important contributions 

to the analysis were made by incorporating the results of ongoing safety analyses being conducted by 

FRA. This report therefore reflects very recent data and up-to-date analyses by FRA on the safety of 

spent fuel transportation by rail. 

This report provides a comprehensive assessment of the possible differences in transportation safety 

resulting from the use of regular, dedicated and key (as defined by the Association of American 

Railroads) trains for the shipment of high-level radioactive waste (HLRW) and spent nuclear fuel (SNF). 

Furthermore, this report provides both a framework and a comparative analysis of alternative shipment 

methods. The framework can be extended to further comparisons with regard to safety as future 

requirements emerge. FRA will maintain an ongoing review of safety and may again employ the 

techniques described in this report, when necessary. For example, this report provides the comparison of 

three shipment methods because key trains were offered as an alternative to either regular trains or 

dedicated trains in the intervening years since the study originated. 

The potential health hazards of SNF and HLRW are serious and are, therefore, addressed by current 

regulatory requirements. While these regulatory requirements provide a high level of safety for HLRW 

and SNF transportation, improvements in safety can still be gained. Due to its potential health hazard and 

the persistence of its effects, the transportation system does not treat radioactive material in the same way 

as other hazardous materials. The safety requirements for radioactive material transportation are 

generally more stringent. This is due to the actual risk posed by the material and society’s perception of 

that risk. Given the special nature of this material, it must be assumed that the public is concerned not 

only with the potential for catastrophic failures of the transportation cask, but also with any noncatastrophic accident (or other event) that would increase the radiation exposure of the crew, workers, 

emergency response personnel, or the public. For that reason, the potential for non-catastrophic accidents 

was also evaluated in this report, and a comparison of those risks was factored into the overall analysis 

and conclusions. 

ix 
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x 
Acknowledgements 

This study was conducted by the Volpe National Transportation Systems Center’s Office of Safety and 

Security for the Federal Railroad Administration (FRA), under the sponsorship of Claire Orth, Chief of 

the Office of Research and Development (RDV-32). FRA would like to acknowledge the contributions of 

the U.S. Department of Energy, U.S. Nuclear Regulatory Commission, and Sandia National Laboratories 

in the preparation of this report. 

xi 
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xii 
Executive Summary 

This report compares the relative safety of rail shipment alternatives for the transport of spent 

nuclear fuel (SNF) and high-level radioactive waste (HLRW). These alternatives involve the use 

of: (1) regular trains: operating without restrictions with the exception of current hazardous 

materials and rail safety regulations; (2) key trains: similar to regular trains but operating with a 

maximum speed limit of 50 miles per hour (mph) or 80.4 kilometers per hour (km/hr) and other 

handling restrictions; and (3) dedicated trains: operating with a maximum speed limit of 50 mph 

(80.4 km/hr) and additional operating restrictions. 

In preparation for this report, the U.S. Department of Transportation’s (DOT) Volpe National 

Transportation Systems Center (Volpe), a part of the DOT Research and Innovative Technologies 

Administration (RITA), in support of the DOT Federal Railroad Administration (FRA), 

performed a study to provide a safety analysis on whether FRA should require carriers to use 

dedicated trains for shipment of SNF and HLRW. 

The study was initiated once funding was appropriated for it in the spring of 1992. 

Representatives from the U.S. Department of Energy (DOE), the U.S. Nuclear Regulatory 

Commission (NRC), potentially affected States and Native American tribes, the railroad industry, 

and SNF/HLRW shippers were invited to attend and consult with FRA and the study contractor at 

a 2-day Dedicated Train Workshop held in Denver, CO, in September 1992. 

In preparing this report, FRA coordinated closely with the DOT Pipeline and Hazardous 

Materials Safety Administration (PHMSA), which also issues regulations governing 

transportation of hazardous materials in all modes,1

 and with the DOT Office of the Secretary. In 

addition, FRA consulted with DOE and NRC. Although comments from other governmental 

agencies were incorporated, this report is ultimately the responsibility of DOT. 

As more fully explained later in this report, the transportation of SNF/HLRW is thoroughly 

regulated, and several agencies of government play active, highly coordinated roles in 

endeavoring to ensure its safety. Over the past 45 years, approximately 600 train movements of 

these materials have occurred by rail without any incidents occurring that have affected the 

integrity of the shipping package. At the discretion of the shipper/carrier parties involved, the 

majority of these shipments were made using special or dedicated trains.2

 The responsible 

agencies work to continually verify the safety of packaging, rolling stock, procedures, and the 

training of personnel involved in transportation. The railroad industry also issued its own 

standard for movement of these commodities, which seeks to establish performance guidelines 

for a cask/car/train system transporting high-level radioactive material. These guidelines are 

 

1 FRA, in concert with the Research and Special Programs Administration (RSPA), develops hazardous 

materials regulations specifically applicable to the rail mode for issuance by RSPA. FRA enforces 

hazardous materials regulations applicable to transportation by rail. Both agencies act by delegation from 

the Secretary of Transportation. Actions referred to in this report where RSPA is referenced were taken by 

RSPA. The PHMSA, created by P.L. 108-427, is the successor organization to RSPA for DOT’s hazardous 

materials transportation and pipeline safety responsibilities and did not yet exist for purposes of this report.

2 As used in this report, a special or dedicated train is a train that consists only of equipment and lading 

associated with the transportation of SNF/HLRW. That is, the train consists only of necessary motive 

power, buffer cars, and cask car(s), together with a car for escort personnel. Such a train does not transport 

other rail rolling stock, other revenue, or company freight.

1 
designed to ensure safe transportation, minimize time in transit, and incorporate best available 

technology to minimize the potential for a rail accident.3

 This report addresses one additional 

means by which a greater level of safety might be achieved, the use of dedicated trains. 

The study analyzed both non-incident risk from radiation emitted from the cask during 

transportation and accident risk. Non-incident risk from the entire future shipping campaign is 

estimated to be on the order of approximately one latent cancer fatality (LCF) for every 40,000 

shipments in non-dedicated trains and approximately one LCF for every 50,000 shipments in 

dedicated trains. Using the number of rail shipments expected over the life of the shipping 

campaign, as stated in DOE’s Environmental Impact Statement on Yucca Mountain as a measure, 

the potential expected LCFs would be appreciably less than one. Therefore, regardless of the 

type of train, the potential exposures are essentially benign when compared to a lifetime of 

normal background radiation exposure from the sun or heightened radiation exposure from flying 

in a commercial airliner at 30,000 feet. The potential exposures are also benign when compared 

to radiation risks associated with smoking tobacco. Given public interest in the subject matter, 

however, the basis for these estimates is set forth below. As the results show, if a discernable 

difference in risk for affected populations exists, the risk is less using a dedicated train. 

With respect to accident risk, safeguards are already in place–principally NRC package 

certification requirements, railroad industry key train requirements, and FRA's focused inspection 

program–that have reduced the potential, to an extremely low probability, that a cask could be 

damaged in rail transportation to the extent it might release radioactive material into the 

environment. However, further reducing the possibility of a train accident involving a 

SNF/HLRW cask is highly desirable, despite the very low probability that the cask might be 

compromised. It is also recognized that any train accident involving a cask shipment would 

degrade public confidence in the ability to safely transport this material, and the presence of a 

cask would greatly complicate emergency response and wreck clearance operations, thus 

compounding costs to responders and the railroad. 

Importantly, the study results support the conclusion that use of dedicated trains would reduce 

both the probability of a SNF/HLRW cask being involved in a train accident and the possibility 

that other hazardous materials might be involved that could subject a cask to a fire environment 

with possible loss of shielding. Although the study intentionally uses worst-case assumptions 

(e.g., minimum compliance with NRC fire exposure criteria) and should not be taken as an 

absolute measure of risk, on a comparative basis, it is apparent that a dedicated train strategy 

should have a favorable impact on any residual risk. 

Background 

SNF is fuel that has been withdrawn from a nuclear reactor following irradiation and has 

undergone at least 1 year's decay since being used as a source of energy in a power reactor. 

Further, reprocessing has not separated the constituent elements of SNF. This fuel includes: (1) 

intact, non-defective fuel assemblies; (2) failed fuel assemblies in canisters; (3) fuel assemblies in 

canisters; (4) consolidated fuel rods in canisters; (5) nonfuel components inserted in pressurized 

water reactor fuel assemblies; (6) fuel channels attached to boiling water reactor fuel assemblies; 

and (7) non-fuel components and structural parts of assemblies in canisters [42 U.S.C. § 

10101(23), 40 CFR 191.02, and DOE Order 5820.2A]. 

 

3 Association of American Railroads (AAR) Standard S-2043: Performance Standard for Trains Used to 

Haul High Level Radioactive Material; AAR Circular Letter C-9619, dated April 29, 2003.

2 
HLRW results from the reprocessing of SNF in a commercial or defense facility. It includes 

liquid waste produced directly in reprocessing and any solid waste derived from the liquid that 

contains a combination of transuranic waste and fission products in concentrations requiring 

permanent isolation [42 U.S.C. § 10101(12), 10 CFR Part 72.3, and DOE Order 5820.2A]. 

HLRW meeting this definition has been shipped by modes other than rail. 

SNF and HLRW must be transported in casks constructed to NRC requirements. Casks are 

secured to specially constructed rail cars capable of transporting the heavy load.4

 This study 

assumes that the cask car(s) will be surrounded by two buffer cars and accompanied by an escort 

car. This complement of cars is referred to as the cask consist. A dedicated train is comprised of 

the cask consist and multiple locomotives. A regular or key train will include the cask consist, 

locomotive(s), along with any number of additional cars potentially containing other regulated 

hazardous materials, various other general cargo, and/or empty rail cars. 

Regular trains typically operate at allowable freight track speed, make numerous classification 

yard entries, and adhere to hazardous materials transportation regulations when transporting any 

regulated hazardous material, including SNF and HLRW. Since it was not possible to analyze all 

possible consist and operational arrangements of regular trains within the confines of this study, 

the model consisted of a generic regular train of 70 cars, with the cask consist in the middle of the 

train.5

In 2001, the AAR issued a Recommended Practice Circular defining any consist containing SNF 

or HLRW as a key train and routes with specified levels of hazardous materials including SNF 

and HLRW as key routes.6

 Key trains are similar to regular trains in length and general operating 

rules except for the following: 

• No consist restriction in excess of current regulatory requirements 

• Cask is placed on a flatcar between two buffer cars 

• Train has a railcar with escort personnel aboard who monitor/guard the shipment 

• A 50 mph (80.4 km/hr) speed restriction 

• Passing not restricted unless on lower than Class 2 Track 

• All cars in the consist are equipped with roller bearings with rules about alarms 

• Key routes have hot bearing detection equipment at minimum intervals and the 

 track must be inspected twice annually for internal flaws and geometry irregularities.

 

4 A typical cask assembly weighs about 250,000 pounds, and a loaded cask car weighs about 394,500 

pounds, in contrast to a typical rail load of 286,000 pounds. Like other cars constructed to carry heavy 

loads, cask cars use additional axles and span bolsters to distribute the weight over a larger portion of the 

track structure. Other special loads transported on the railroad include large transformers and specialized 

industrial equipment.

5 FRA does not mandate specific placement of loaded and empty cars in trains except in the case of 

placarded cars carrying regulated hazardous materials in accordance with 49 CFR 174.85. However, 

industry guidelines and carrier rules exist to address train make-up in light of joint industry-government 

research. From the point of view of train dynamics, a heavy vehicle such as a cask car would typically 

require placement in the first third of the train.

6 AAR Recommended Practice Circular OT-55D, Recommended Railroad Operating Practices for 

Transportation of Hazardous Materials, 2001. 

3 
In the study, by contrast, dedicated trains were assumed to operate according to the following: 

• Consist is restricted–no freight other than SNF and/or HLRW is carried. 

• Cask is placed on a specially designed and equipped flatcar between two buffer cars. 

• Multiple locomotives. 

• Train has a railcar with escort personnel aboard who monitor/guard the shipment. 

• A 50-mph (80.4 km/hr) speed restriction. For completeness a 35 mph (56.3 km/hr) speed 

restriction was also analyzed, although this restriction no longer applies since the 

publication of AAR circular OT-55-D. 

• Passing is restricted on all track classes. When a dedicated train is passed by another 

 train, one of the trains remains still while the other train passes at a speed less than or 

 equal to 50 mph (80.4 km/hr). Again, for completeness a 35-mph (56.3 km/hr) speed 

 was also analyzed.

Between 1979 and 1997, over 1,300 shipments of commercial SNF and HLRW were made 

totaling over 1,102 tons (1,000 metric tons). Although only about 11 percent of the shipments 

were by rail, these accounted for over 75 percent of the tonnage [NRC, 1998].7

 To date, 

approximately 800 shipments of naval SNF and HLRW have also been safely made in both 

regular trains and dedicated trains. In the future, DOE estimates that a total of between 11,000 

and 17,000 casks of SNF and HLRW will need to be shipped by rail [DOE, 2002b].8

 A shipment 

by rail can consist of a single movement of a single cask or a single movement of multiple casks 

with escort and buffer cars, as needed. 

Safety Compliance Oversight 

Regulations addressing hazard communication, training, security plans, packaging, and modal 

operational requirements for transporting regulated hazardous materials, which includes SNF and 

HLRW, exist in 49 CFR Parts 100-185 (Hazardous Materials Regulations). Rail safety 

regulations in 49 CFR Parts 200-244 address safety requirements for railroad operations, 

including: rail equipment, track, signal systems, communications, train crews, and grade 

crossings. These rail safety regulations apply regardless of whether any hazardous material is 

transported in a train. 

The Nation’s rail carriers conduct their own inspections in their efforts to ensure compliance with 

all applicable regulations. FRA and participating State agencies that have FRA-Certified State 

inspectors continually use the resources available to them to the extent possible to conduct 

inspections of the Nation’s rail carriers and to ensure that regulatory compliance is being 

achieved. 

In addition to these efforts, FRA developed and implemented the Safety Compliance Oversight 

Plan (SCOP),9

 a coordination and inspection plan specific to all known rail shipments of SNF and 

 

7 U.S. Nuclear Regulatory Commission. Public Information Circular for Shipments of Irradiated Reactor 

Fuel. Washington, DC: NUREG-0725 REV13. October 1998.

8 U.S. Department of Energy. Final Environmental Impact Statement for a Geological Repository for the 

Disposal of Spent Nuclear Fuel and High-Level Radioactive Waste at Yucca Mountain, Nye County, 

Nevada. Washington, DC: Office of Civilian Radioactive Waste Management, DOE/EIS-0250 Vol. I and 

II. February 2002.

9 FRA's SCOP, can be viewed and downloaded from FRA's Web site at 

4 
HLRW. Implementation of SCOP focuses available resources to ensure the safe and secure 

transportation of SNF and HLRW. The SCOP addresses what tasks FRA and its FRA-certified 

State inspection partners will perform for shipments of SNF and HLRW. The tasks cover all 

operational aspects of the rail transportation environment, as well as planning and coordination 

tasks with entities and agencies involved in the transportation of this material. 

To date, FRA has implemented the SCOP for each movement due to the infrequency of these 

shipments. However, FRA recognizes that as shipments ramp up, which could be as early as 

2007, it will be become increasingly difficult to implement the SCOP tasks in their entirety as 

they currently exist for every shipment. Congress has recognized the importance of ensuring that 

shipments of SNF and HLRW move safely and securely and has provided FRA with the ability to 

add inspection personnel via the budget process. Regardless of the type of train used for this 

function, FRA and participating State agencies will continue to facilitate the safest possible 

transportation of SNF/HLRW by enforcing the railroad safety laws and regulations, and the 

Hazardous Materials Regulations. It is evident, however, that FRA’s task in this regard is greatly 

simplified and the likelihood of success is enhanced, where dedicated equipment is employed and 

the route is as direct and well suited to the mission as possible. Concentrating on the safety of a 

discrete subset of locomotives and cars, and surveying a route that avoids congested yards will 

increase the likelihood that safety concerns are reliably identified and remedied before the 

railroad accepts the shipment. 

Comparative Risk Assessment 

The study assumed two basic types of risks involved with transporting SNF and HLRW: (1) 

incident-free risks and (2) accident-related risks. The incident-free risks associated with normal 

emissions of very low radiation doses from the cask involved absolute risks of appreciably less 

than one LCF for the entire exposed population for the highest risk case, the regular train, over an 

entire shipping campaign. Primarily because of the reduced time in transportation, incident-free 

risk was lowest for dedicated trains (again appreciably less than one LCF for the shipping 

campaign). These estimates are higher than would be realized in actuality, as they assume the 

maximum allowed emissions from the casks in non-exclusive use transportation rather than the 

generally lower emissions from actual shipments.10

Incident-free risks result from continuous emissions of low doses of radiation, which the cask 

shielding cannot totally contain. The emissions, however, can and are limited to acceptable safe 

levels (a maximum of 10 millirems per hour (mrem/hr) at 3.3 ft (1 m) from the surface of the 

package [49 CFR 173.441]). All individuals exposed to the radiation being emitted from the cask 

during transport, handling, loading, and unloading are exposed to very low doses of incident-free 

radiation. 

 

www.fra.gov/downloads/safety/scopfnl.pdf.

10 Before proffering a cask for shipment, the shipper must demonstrate compliance of the cask design with 

10 CFR Part 71, as promulgated by NRC. Experience has shown that radiation levels emitted by the 

package are generally below the maximum allowed by regulation for non-exclusive use shipments due to 

the shielding built into the packages and the efforts of the shipper to reduce the external radiation levels to 

be as low as possible. In addition, radiation levels are checked by State and Federal Government agencies 

before being offered into transportation and can also be monitored while in transportation. FRA recently 

secured additional staff to support this function.

5 
Accident-related risks result from the potential of exposure to radiation after an accident occurs. 

Radiological consequences were calculated for accidents where consequences vary with the use 

of a regular, key, or dedicated train service. For each accident type, incident durations from 3 to 

72 hours were analyzed to account for a range of severities, and three locations types, urban, 

suburban, and rural, were analyzed. For the purposes of this study, accidents were broken down 

into four severity categories: 

• Category I Delay event. Accident well within the Hypothetical Accident Conditions 

(HAC) modeled by the cask packaging test criteria of 10 CFR Part 71; dose 

rate assumed equivalent to the allowed non-exclusive use transport rate of 10 

mrem/hr at 3.3 feet (1 m) from the cask surface. Accidents in Category I 

could result in an increased duration of exposure to certain individuals (such 

as crew and nearby population) due to the extended time required to clear the 

wreck scene and resume transport. 

• Category II Serious accident. An accident close to the HAC, which could result in a 

hundredfold increase in radiation levels, but no release of radioactive material 

occurs. The dose rate is assumed equal to 1 rem/hr (1,000 mrem/hr) at 3.3 feet 

(1 m) from the cask surface. Accidents in Category II could expose 

populations to higher doses of radiation for extended time periods. 

• Category III Major accident. An accident that generates forces or temperatures that exceed 

the HAC. A greater loss of shielding or internal damage occurs but no release 

of radioactive material occurs. The dose rate is assumed to be equal to 4.3 

rem/hr (4,300 mrem/hr) at 3.3 feet (1 m) from the cask surface. Accidents in 

Category III could expose populations to higher doses of radiation for 

extended time periods. 

• Category IV Severe accident. An accident resulting in forces or temperatures well in 

excess of the HAC. A significant loss of shielding or cask damage resulting in 

the release of some radioactive material. This category was not analyzed as it 

was considered equally unlikely for any of the shipping options, and the 

consequences would not be substantially different. 

The consequences of any of these four types of accidents are determined by the environment in 

which the accident occurred; the potential for a second event, such as a fire following the initial 

impact, puncture, or fall; and the time required to respond to the accident. 

Incident-free and accident-related risks are analyzed for entire populations, and results are 

expressed as population doses (person-rem). These population doses are also converted into an 

estimate of health effects (i.e. LCFs). Doses for individuals (where applicable and possible) are 

expressed in units of mrem. 

The use of LCF as a metric of deleterious health effect is based upon the assumption that any 

amount of radiation exposure may pose some risk. This is the linear, no-threshold (LNT) model, in 

which any increase in dose has an incremental increase in the risk of occurrence of cancer. LNT is 

the accepted model used in the United States, as well as by international radiation protection 

bodies. The LCF rate for worker population is 0.0004 per person-rem, while the LCF rate for the 

general population is 0.0005 per person-rem [NCRP 1993].11 When the rates are applied to an 

 

11 National Council on Radiation Protection and Measurement (NCRP). Limitation of Exposure to Ionizing 

6 
individual, the units are for a lifetime probability of LCFs per rem (or 1,000 mrem) of radiation 

dose. When the rates are applied towards a population of individuals, the units are excess number 

of cancers per person-rem of radiation dose. The difference between the worker dose and the 

general public risk is attributable to the fact that the general population includes more individuals 

in sensitive age groups (that is, less than 18 years of age and over 65 years of age). 

Calculating Risk 

The total risk associated with transporting SNF and HLRW is the result of both incident-free risk 

and accident-related risk. The amount of the low-level exposure associated with incident-free 

transport depends on the details of the number of shipments, specific routes, and operating 

variations. Accident risks are associated with relatively low probability events. The accident 

probabilities are based on historical accident data independent of a specific route or location. 

Incident-free and accident-related risks of radiological exposure are calculated independently for 

regular, key, or dedicated train service. The results from these calculations are then compared 

against commonly accepted radiological exposures to put the calculated risk into perspective. 

Incident-Free Risk 

Incident-free risk involves calculating the total expected radiation dose to the public and other 

impacted populations for specific routes, assuming no accidents, and comparing that calculation 

to the incident-free risk for regular, key, and dedicated trains. A radiation level of 10 mrem per 

hour measured at 3.3 ft. (1 m) from the package surface was used to calculate population 

exposures; this is the maximum level for radioactive material packages in non-exclusive use 

service. The results are also compared to the radiation received by a passenger on a 4-hour airline 

flight. Regulations in 49 CFR 173.441 for exclusive-use shipments do allow for higher radiation 

levels to exist both at the package surface and at 1 m from the package, and yet still allow the 

package to be transported, but only if additional safety measures are implemented. Experience 

with shipments of SNF and HLRW to date have shown that the radiation levels are well within 

the prescribed lower regulatory limits for non-exclusive use shipments and therefore are the 

norm. 

Though SNF/HLRW casks are very well shielded by design, they continuously emit low levels of 

radiation throughout all phases of transportation. Hence, radiation exposure to crew, handlers, 

yard personnel, and the wayside population occurs even in the event that an accident does not 

occur. Therefore the probability of exposure is equal to one. The exposure of all affected 

populations during regular transport is defined as the incident-free risk. The radiological 

consequences of SNF/HLRW shipments are a function of the selected route, the cask design and 

material being transported, the size of the impacted populations, the population distance from the 

cask, the total exposure time, and the amount of shielding between the cask and the impacted 

populations. 

RADTRAN 5, a set of computer models for the analysis of the consequences and risks of 

radioactive material transport, was used to calculate the incident-free risk. The package dose rate 

and the package-specific characteristics are used to model the transport cask as a point source for 

extended distances. For shorter distances, within two characteristic lengths of the cask, the 

package is treated as a line source. The transportation system characteristics are incorporated into 

a rail-specific model, with input parameters for population along the route and at stops, which 

 

Radiation. Bethesda, MD: NCRP Report No. 116 1993.

7 
include vehicle velocity and stop duration. The population density is defined by the user along 

each route segment. Inputs include the specific characteristics of sub-populations like the number 

of passengers, crews, and rail workers. The general population is broken into three sub-groups: 

urban, suburban, and rural. 

The calculations were conducted for in-transit exposures (off-link and on-link) and exposures at 

stops. Off-link doses are defined as those received by persons on the ground within 875 yards 

(800 m) of a passing train. On-link doses are defined as doses received by persons on passing 

trains, as well as by the escorts and crews on board the cask-carrying train. Stop doses were 

calculated as doses received by persons on the ground as well as crew and escorts within 875 

yards (800 m) of the train during a stop. 

Six routes were chosen for analysis. These routes were chosen to cover a representative number 

of origination locations across the country with currently operating nuclear power plants or waste 

repositories that handle SNF or HLRW. The presumed destination point for all routes is Yucca 

Mountain in Nevada. Table 1 provides a breakdown of the length of each route, as well as the 

associated average population densities along each route broken down into urban, suburban, and 

rural sub-groups. The selected routes are likely candidates and are representative in terms of their 

geographic location and length. 

Many designs and sizes of casks exist for transporting SNF and HLRW. For purposes of this 

study, it is assumed that the cask will be a large 125-ton (113-metric ton) multi-purpose rail cask 

[DOE, 1993].12 The incident-free dose rate was taken as 10 mrem/hr at 3.3 feet (1 m). As 

described above, the transport cask emission rate was modeled as either a point source or a line 

source depending on the distance of the exposed population from the transport cask. 

Table 1. Routes Used in the Analysis 

Route 

Number 

Origin Length Average Population Density 

persons/sq mile (persons/sq km) 

Miles (km) Urban Suburban Rural 

1 Humboldt Nuclear Power 

Plant, CA 

1,090 

(1,754) 

6,237 

(2,408) 

1,164 

(449) 

26 

(10) 

2 Crystal River Nuclear Power 

Plant, FL 

2,988 

(4,809) 

5,641 

(2,178) 

976 

(377) 

38 

(15) 

3 Dresden Nuclear Power Plant 

Dock, IL 

1,920 

(3,090) 

5,169 

(1,996) 

1,006 

(389) 

26 

(10) 

4 River Bend Nuclear Power 

Plant, LA 

2,471 

(3,977) 

4,964 

(1,917) 

919 

(355) 

30 

(12) 

5 Seabrook Nuclear Power 

Plant, NH 

3,086 

(4,966) 

6,109 

(2,359) 

1,028 

(397) 

30 

(12) 

6 Hanford Repository, WA 1,226 

(1,973) 

4,744 

(1,832) 

1,307 

(505) 

17 

(7) 

Source: 2000 U.S. Census. 

The exposed populations were broken down into the following categories: 

• General population, which is individuals residing and working near rail lines (waysides) 

over which the cask passes as well as people who live near yards and sidings where the cask 

consist may stop temporarily 

 

12 U.S. Department of Energy. MPS Conceptual Design. Draft 1993. 

8 
• Persons on trains sharing the route of the shipment 

• Vehicle occupants at grade crossings along the shipment route 

• Train crew located in the lead locomotive on the train transporting the SNF/HLRW 

• Escorts on the train transporting the SNF/HLRW 

• Railroad personnel who work in close proximity to the cask in classification yards and 

inspect the train at various points 

• Other rail yard workers not in close proximity of the shipment

Each of the different groups experience different exposure levels and durations. Wayside 

populations and passengers on passing trains will be exposed as the shipment passes. Highresolution population data was used from the 2000 U.S. Census to allocate population density 

along the length of each route in a 1-mile wide corridor. Greater exposure will be calculated for 

longer routes that are highly populated. This is because exposure time is the determining factor 

in the amount of radiation members of a population group receive. Time spent near both moving 

and standing shipments affect exposure. Train operational restrictions, such as train speed and 

run-through operations, impact exposure time at stops and in transit. 

The train density and train occupancy data derived from the Rail Garrison13 network studies were 

used to assign the number of persons likely to be sharing the railway with the shipment. The 

average passenger train density was used for the three general population sub-groups: urban at 

0.4 trains/hr, suburban at 0.2 trains/hr, and rural at 0.14 trains/hr. The weighted average train 

speed for each type of train is the determining parameter for exposure. The faster the trains are 

allowed to travel, the shorter the exposure time. 

Vehicle occupants at grade crossings on each side of the railroad can be exposed to emissions 

from passing shipments. The exposure to this sub-population was split into two different 

calculations: one for the general sub-population and the second for cars within a prescribed 

distance to the passing shipment. For purposes of this study, it was assumed that five vehicles 

would be occupying either side of the track during the passing of a shipment. 

Members of the train crew and escorts are exposed for the full duration of the shipment and 

therefore experience the highest exposure levels of any sub-population. The exposures for these 

sub-populations are governed by distance from the source, length of route, and stops. Crew 

members on regular or key trains have the advantage of being further away from the cask consist 

than those on dedicated trains. The position of the escorts on any train type, however, is the 

same. 

During stops at yards or sidings, other railroad personnel will be exposed for the duration of the 

stop. Since train stops usually occur at rail yards, the population in and near a rail yard is 

modeled as a uniformly distributed population and the dose is integrated into this population. For 

rail stops, the public dose was calculated using the suburban population density. Greater 

exposure occurs for longer stop times and along routes that have more stops. 

 

13 Peacekeeper Rail Garrison Program, Rail Network Database developed by Earth Technology 

Corporation for the Department of The Air Force. Network not publicly available, but similar network data 

available from National 1:100,000 Scale Rail Network, distributed on the National Transportation Atlas 

Database produced by the Bureau of Transportation Statistics (BTS). 

9 
Exposure time for incident-free risk is determined by train speed, whether run-through operations 

are allowed, and the number of stops required at yards or sidings. The speed restrictions on key 

and dedicated trains increase in-transit exposure time when compared to regular trains. The 

difference, however, is greatly affected by such factors as the class of track over which the 

shipment traverses. Higher track classes allow for greater train speeds. 

The last critical factor associated with exposure is the type of shielding factor that is applied to 

the various sub-populations to determine gamma radiation attenuation (absorption by physical 

structures). For the general wayside population different shielding factors were applied 

depending on the population density. Rural populations were assigned a shielding value of 1.0, 

which corresponds to no shielding. Suburban populations were assigned a shielding factor of 

0.87 because of the presence of closely spaced structures generally constructed from wood and 

cinderblocks. The urban population had the highest shielding factor of 0.018 due to the 

concentration of buildings constructed from concrete and steel. Occupants at grade crossings, 

train passengers, escorts, and inspectors/handlers were assigned a shielding factor of 1.0 (no 

shielding). Crewmembers were assigned a shielding factor of 0.5 assuming that the intermediate 

locomotive(s) provides gamma radiation attenuation. General yard workers were assigned a 

shielding factor of 0.1 due to the mitigating effects of gamma radiation attenuation by rail cars 

and structures in the rail yard. The suburban shielding factor was used for the general population 

for all stops. 

Risk to all population groups is strictly a function of the period of exposure, distance from the 

cask, and the assumed level of shielding provided by intervening equipment or buildings. Transit 

time and time in yards becomes a major determinant when comparing service options. 

Accident-Related Risk 

Accident-related risk involves comparing the radiological exposure due to accidents with that for 

regular, key, and dedicated train service by using three components: accident involvement 

probability, accident severity probability, and expected consequences. 

Accident-related risk is the second form of risk associated with the transport of SNF and HLRW 

along the national rail corridors between originations and final destination. Aggregate accidentrelated exposure is not calculated; aggregate accident probabilities, not specific to routes, are 

calculated. Potential accident-related exposure is examined by predicting the accident likelihood 

for the three rail transport methods and then assigning radiological consequences, broken down 

into four severity categories. The baseline accident probability is calculated for regular train 

transport using historical accident data from 1988 to 2001. Dividing the total number of 

accidents by reported train miles for each year normalized these historical accident rates. The 

rates were then adjusted to reflect the special constraints associated with key and dedicated trains. 

Event schematic trees based on these probabilities were then constructed that show the 

probability of any mainline or yard accident for regular train service. During this 1988-2001 

period, the number of train miles varied from year to year but has generally risen. A long period 

was chosen to help determine the probability of extremely rare events, such as major fires or 

high-speed collisions. The variation in accident probability in terms of train miles is not expected 

to noticeably change with the addition of dedicated trains in the future. Changes in operating 

practices and improvements in equipment and infrastructure maintenance should reduce these 

rates. For this analysis, the accident probability is assumed to be constant, as reflected by the 

event trees. These trees were then modified to reflect the effect of key and dedicated trains on 

10 
accident probabilities. Aside from speed limits, the dedicated train modifications included 

operational restrictions, consist limits, and reduced visits to yards. 

Radiological-related risks from accidents are based upon the following factors: the design of the 

cask and its ability to withstand mechanical, thermal, and combined mechanical and thermal 

accident loads; the likely level of loss-of-shielding (LOS) resulting from accident loads; and the 

effect of that radiation on crews, escorts, emergency response personnel, and the general 

population surrounding an accident site. 

A key assumption in the analysis was the response of the generic cask design. Analysis results 

were taken from a Sandia National Laboratories study performed on a bare cask with no impact 

limiters, impacting surfaces with varying hardness, at a range of impact speeds, and in different 

orientations. Force-crush characteristics were taken from that study for the hypothetical 125-ton 

(113 metric ton) steel-lead-steel cask. These characteristics were then used as inputs into a 

simplified collision dynamics model to investigate residual cask impact speeds for secondary 

impacts. The conservative assumption was made that any impacts in the rail environment would 

be considered as impacts into a hard but not unyielding surface. The speed equivalent of the 

NRC-required package certification HAC drop test criteria in 10 CFR Part 71 onto an essentially 

unyielding planar surface has been determined to be 30 mph. 

Substantial kinetic energy is associated with a train in the event of a collision or derailment. This 

energy must be dissipated through various mechanisms before the train comes to a complete stop. 

Energy consumption through plastic deformations of colliding objects, plowing of rails and 

ballast, and emergency braking are only a few ways that the collision energy is absorbed. Of 

concern for this analysis is the consumption of energy through plastic deformations of rail 

equipment and the cask. Two collision types were studied: a primary impact against a heavy 

freight locomotive and a subsequent secondary impact against the surrounding infrastructure or 

environment. 

A transport cask impact with a heavy freight locomotive was chosen as a representative example 

of a worse case primary impact in the rail environment. Two impact load paths were assumed for 

crush of a generic freight locomotive. Using each crush trajectory, force-crush characteristics 

were developed based upon previous crashworthiness work. The force-crush characteristics of 

both the transport cask and the freight locomotive were used to establish LOS from a direct 

impact of the cask with a locomotive. LOS addresses the extent or degree that a SNF/HLRW 

cask may experience alteration of the radiation shielding component of the cask package, 

potentially resulting in increased radiation fields outside the cask package envelope. It was 

determined that cask damage could not occur for primary impacts with a heavy freight 

locomotive. 

The second collision type studied was secondary impact of bare transport casks, without force 

limiters with the surrounding rail environment. The cask residual speed after a primary impact at 

various cask orientations and speeds was calculated for the following classes of collisions: headon, rear-end, rail-rail crossings, and raking/corner impacts. Calculations were performed to 

determine scenarios where residual cask speeds exceeded the required NRC package certification 

drop test speed equivalent. This information was then used to estimate the accident consequences 

for the four severity categories. 

Three event trees were constructed for regular train service: one for mainline incidents, one for 

yard incidents, and one for fires. Fires are treated independently because they can be initiating 

events or a secondary event following one of the other accident scenarios. The distinction 

11 
between mainline and yard accidents is made to account for the significant difference in the 

number of yard entries made by a regular/key train versus a dedicated train. A significant 

decrease in accident probability results from this operational distinction. This information is used 

when modifying the accident rates for dedicated trains. 

Each event tree begins with the overall train accident rate per train mile based upon the historical 

accident review. Accidents are further subdivided into the following categories: collision, 

derailment, highway-rail grade crossing, fires/explosions, and miscellaneous. The probabilities 

for these sub-accident distinctions are reflected in the second level nodes on the event tree. These 

sub-accidents can result in a derailment, so the probability of a subsequent derailment is also 

calculated. Accident severity is calculated using the range of speeds that the derailment occurs at 

and is broken down into the four severity categories. The severity category is based upon the 

comparison of the final derailment speed to the required NRC package certification drop test 

speed equivalent. 

Study Results 

Incident-Free Risk 

The total exposure during incident-free transport of SNF and HLRW is extremely low for all train 

service types (regular, key, and dedicated). In all of the examined representative routes, the 

expected number of LCFs incurred by any type of train service is less than one for the total 

estimated number of shipments over the entire projected DOE shipping campaign. 

The magnitude of radiation dosage to any population in incident-free shipping of SNF and 

HLRW is dependent on the total exposure time and the distance from the shipping cask. 

Exposure time, therefore, is heavily influenced by the amount of stop time (mostly in rail yards) 

and the amount of time the shipment is in transit. 

Although all train service types have extremely low dose levels, measurable differences exist in 

radiological exposure due to the service type. Regular and key train service would result in higher potential doses to the general public, with estimates of 0.0235 person-rem to 0.0495 personrem per single cask shipment. This translates into LCF estimates of 1.17x10-5 to 2.48x10-5 per 

single cask shipment; in the worst case, this is roughly one LCF for every 40,000 shipments. 

DOE estimates that approximately 11,000 to 17,000 waste packages are to be shipped by rail 

over the entire campaign [DOE 2002b]. Dedicated trains reduce this exposure range to 0.0177 

person-rem to 0.0364 person-rem per shipment, or 8.85x10-6 to 1.82x10-5 LCF. The highest range 

of this estimate corresponds to approximately one LCF per 50,000 shipments. This reduction is 

primarily due to the fact that dedicated trains do not stop in yards for classification, reducing the 

total exposure time. 

The total radiation dose to a person standing 98.5 ft (30 m) from a train carrying a single 

SNF/HLRW car as it passes at 15 mph (24 km/hr) is calculated to be approximately 0.0004 mrem 

(this value is independent of train type). For comparison, the average dose received by a 

passenger on a 4-hour jet flight is roughly 3 mrem or 4 orders of magnitude greater than a cask 

shipment. 

Rail worker doses are lower for dedicated trains than for key and regular trains. The total 

radiation dose to all rail workers through regular or key trains for the examined routes ranges 

from 0.0988 person-rem to 0.1755 person-rem per shipment, or 3.95x10-5 to 7.02x10-5 LCF. The 

highest range of this estimate corresponds to approximately one LCF per 14,000 shipments. 

Dedicated train single shipment doses ranged from 0.0496 person-rem to 0.0987 person-rem, 

12 
which translates into 1.98x10-5 to 3.95x10-5 LCF. This small decrease in absolute dose value is 

primarily due to the reduced yard visits of dedicated trains. 

Train crew doses are actually higher for dedicated trains than for the other service types due to 

the proximity of the cask car to the locomotive in a dedicated train consist; however, in all cases 

the radiation exposure of the train crew from a single cask shipment is multiple orders of 

magnitude less than the annual limits prescribed by Federal regulations (10 CFR 20). The highest 

exposure estimate of a dedicated train crewmember is 0.808 mrem per single cask shipment. For 

comparison, the regulatory maximum annual dose for non-radiation workers is 100 mrem, or over 

100 single cask shipments in a year by the same crewperson for this worst-case dose estimate. 

The highest crewperson dose per single cask shipment for regular or key trains is less, 

approximately 0.016 mrem. 

Accident-Related Risk 

The assumptions used to analyze the accident consequences and probabilities make regular and 

key trains nearly identical in terms of risk. 

The historical accident probabilities were sorted by the resulting radiological severity category. 

The consequences of Category I, II, and III accidents are slight in terms of resulting LCF for all 

train service types. Analysis indicates that Category II and III accidents are very unlikely events, 

regardless of service type. 

The event trees constructed from historical accident data indicate that the most likely sources of 

Category II accidents are derailment accidents and yard accidents. The probability of an accident 

that is more severe than the NRC HAC package certification regulatory test requirements 

(Category III) is extremely low for all service types. Dedicated trains have the lowest accident 

probability due to the decreased stopping distance of the shorter consist, the fewer number of cars 

to derail, and fewer yard visits (decreasing yard accident probabilities). The probability of a fire 

engulfing the cask car is lower for dedicated trains because cars carrying hazardous materials are 

restricted from the consist. 

The predicted LCF consequences of Category I, II, and III accidents are multiple orders of 

magnitude less than one per incident, regardless of service type. As with incident-free transport, 

differences in service are delineated in the results of this study. Regular or key trains involved in 

a Category III accident are estimated to result in less than 0.03 LCF. The LCF prediction for 

dedicated trains involved in a Category III accident is considerably lower, less than 0.009 LCF. 

The differential is due to the fact that the greater number of cars in regular and key trains requires 

more rerailing time. The accident consequences of Category I and II accidents are substantially 

less severe, resulting in several orders of magnitude less than one LCF per incident. 

Significance of Findings 

The study concluded that the maximum individual radiological exposure resulting from an 

incident-free shipment of SNF or HLRW by regular, key, and dedicated trains is approximately 

equal to the exposure received in the first 2 seconds of a typical 4-hour airline journey. Figure 1 

compares incident-free exposure rate with other common exposures. 

13 
Figure 1. Comparison of Incident-Free Exposure 

Rate versus Other Common Exposures 

The dominant feature that differentiates the three types of service in the incident-free analysis is 

transit time. Although key and dedicated trains have a 50 mph operating speed limit, dedicated 

trains will have the shortest transit times because they would spend less time in yards. 

Dedicated trains would be expected to have lower collective population exposures because of the 

shorter transit times. Dedicated train crew exposures would be higher because of the cask being 

closer to the crew. The study did not take into account potential as low as reasonably achievable 

(ALARA) radiation controls that could be used by train crews to further limit their potential 

exposure. 

When considering the accident-related radiological risks, three relevant issues exist, which are: 

the likelihood of an accident, the severity of the accident, and the recovery time from the 

accident. When considering the accident risk, the likelihood of a category III accident, where 

cask damage exceeds regulatory limits but does not involve radioactive material release, 

dominates the analysis. For all types of service studied, the category III events are very rare. The 

resulting exposure would still result in a small fraction of one LCF. 

Dedicated trains, compared to regular and key trains, reduce the potential radiation exposure in 

any accident, as accident clearing can be expedited with shorter trains. In addition, since no other 

hazardous materials are in the consist, little chance of a fire would occur, which would prolong 

the response and accident clearing duration. 

Key trains, similar to dedicated trains, provide an increase in safety resulting from speed 

restrictions but are more similar to regular trains in terms of overall risk. Key trains have a risk of 

high-speed impacts equal to or slightly greater than that of dedicated trains, which could result in 

14 
cask damage that could potentially exceed the criteria to which it was certified. A severe fire 

involvement and yard accident probability of a key train is equal to the risk for regular trains. 

Given a derailment, the length of regular and key trains and the likely number of derailing cars 

will extend the time necessary to address an accident and increase the radiation dose to 

surrounding populations. 

Analysis of the location and pattern of accident occurrences indicates that route-specific factors, 

such as the number of yards encountered, can have a significant impact on risks. The use of 

dedicated trains will expedite shipments and will reduce the hazards associated with frequent yard 

visits, especially on long routes where multiple stops in yards are required. Use of dedicated 

trains also allows more flexibility to avoid higher risk locations and to impose restrictions such as 

lower operating speeds. 

In this study a consist of only one cask was assumed to be present in any of the transport options. 

Operating consists of multiple casks could be included in any of the trains, changing the 

cumulative exposures to crewmembers and the general public. Multiple cask consists would, in 

general, reduce the cumulative radiation exposure for the incident-free case but might slightly 

increase the probability of severe accidents due to a cask-to-cask collision. 

Total System Risk 

Some analyses of the merits of dedicated trains suggest that their use would increase train 

miles and, thus, overall increase risk in rail transportation. FRA appreciates this perspective but 

believes this consideration is not dispositive for the following reasons: 

• Any additional net increase in exposure is significantly less than that associated with the 

dedicated train. A conventional train would need to switch the shipping point, incurring risk 

similar to that incurred by the dedicated train. Depending upon the configuration of the rail 

facilities, including the industry track, additional risk might be introduced related to cars left 

on the main line (collision potential, roll-away potential) in the conventional train 

configuration. The same issues apply at destination. 

• As reflected in the Volpe study, the more direct route taken by the dedicated train reduces 

both non-incident and accident-related risks associated with this type of shipment. 

• Under the new AAR Standard, the likelihood of derailment associated with transportation of 

the overweight cask car will be further mitigated through use of a state-of-the-art consist. 

(Although defined in terms of key trains, this is actually a dedicated train concept and is 

wholly incompatible with a general manifest train.) 

• Use of Electronically Controlled Pneumatic (ECP) brakes by a dedicated train will reduce or 

greatly mitigate collision events, including highway-rail crossing collisions. 

• The principal element of exposure for all types of trains are highway-rail grade crossing 

accidents. This exposure, and it is the same for dedicated, key, and regular trains, is in 

decline due to improvements in engineering, education, and enforcement (when compared 

with the incident rate during earlier studies).14

As a society, some risks are tolerated more readily than others. Normal risks associated with rail 

transportation are more readily tolerated than the risk of a significant event involving a 

SNF/HLRW movement, in part because of limited public understanding regarding the safeguards 

 

14 Exposure related to trespassers on railroad property is a material issue, but it is by no means clear that the 

number of casualties varies by number of trains operated or by train miles. 

15 
provided. Where public tolerance is low, value (in the form of reduced anxiety and increased 

acceptance) exists in further reducing the already low risk that a serious event will occur. 

Summary and Conclusion 

The study indicates that risk to employees and the public from transportation of SNF/HLRW is 

low, but on a comparative basis dedicated trains appear to offer advantages over general consists. 

Several of these inherent advantages─avoiding yards, reducing derailment potential, and reducing 

the risk of involvement of other hazardous materials in an accident scenario─could be further 

exploited with careful attention to conditions of transportation. 

For instance, the recent AAR Standard S-2043,15 which was issued too late for formal 

consideration, calls for use of ECP brakes on trains carrying SNF/HLRW. ECP brakes have the 

capability of reducing stopping distances by 40-60 percent. Coupled with uniform composition 

of the consist, ECP brakes should significantly enhance the ability of the locomotive engineer to 

control in-train forces and mitigate the severity of collision with other trains and obstructions on 

the right-of-way, including vehicles at highway-rail crossings. In some cases, collisions may be 

avoided entirely. Use of the communications backbone provided by ECP brakes may also make 

possible the use of onboard sensors that can identify safety problems, such as overheated 

bearings, before they progress to failure. These kinds of engineering enhancements should be 

possible with equipment dedicated to these special trains. By contrast, such enhancements will 

not be implemented for some time on the general interchange fleet. 

FRA's SCOP efforts are also much more likely to be successful if dedicated equipment and 

special trains are employed. While inspection processes are a proven, essential element of quality 

control, they work best as part of a total system approach. Being able to examine dedicated 

equipment at regularly established shop locations and following the service history of the 

equipment to identify any propensities for wear or malfunction will increase the reliability of the 

inspection process both for the railroad and FRA. 

Historically, the principal objection to use of dedicated trains was cost to the shipper. FRA's 

preliminary analysis, however, indicates that use of dedicated trains should not result in 

significantly higher costs for these movements. Bypassing switching yards dramatically shortens 

transit times and lowers the cost of dedicated train operations. Dedicated trains comprised of 

state-of-the-art equipment maintained for this service and operated in small consists should incur 

many fewer mechanical malfunctions (e.g., broken coupler knuckles, unintended emergency 

brake applications) that could delay transportation and result in unexpected costs to shippers and 

the railroad. 

A cost comparison of the six routes used in the study indicates that the operational and escort 

labor costs of dedicated train shipments of at least three casks or more are approximately equal to 

or less than if shipped by a train which would require yard switching. Thus the inherent cost of a 

dedicated locomotive and crew can be offset by the shorter transit time. Public costs should also 

be lower, since SCOP inspections can focus on a smaller number of route miles and fewer units 

of rolling stock. 

 

15 AAR. Performance Standard for Trains Used to Haul High Level Radioactive Material. Washington, 

DC: AAR Circular Letter c-9619/AAR Standard S-2043. April 2003. 

16 
1. Introduction 

This report compares the relative safety for three rail shipment methods (regular, key, and dedicated 

trains) for the transport of SNF and HLRW. This analysis of the three rail shipment methods considers 

the safety impacts resulting from accidents, as well as from radioactive emissions, that occur continuously 

during incident-free shipments. 

1.1 Purpose 

This study compares the safety of using trains operated exclusively for transporting HLRW and SNF 

(hereafter referred to as dedicated trains) with the safety of using standard freight manifest trains. SNF is 

fuel that has been withdrawn from a nuclear reactor following irradiation, has undergone at least 1 year’s 

decay since being used as a source of energy in a power reactor, and the constituent elements of which 

have not separated by reprocessing. SNF includes (1) intact, non-defective fuel assemblies, (2) failed fuel 

assemblies in canisters, (3) fuel assemblies in canisters, (4) consolidated fuel rods in canisters, (5) nonfuel components inserted in pressurized water reactor fuel assemblies, (6) fuel channels attached to 

boiling water reactor fuel assemblies, and (7) non-fuel components and structural parts of assemblies in 

canisters (40 CFR 191.02 and DOE Order 5820.2A). HLRW is the waste material that results from the 

reprocessing of SNF in a commercial or defense facility, including liquid waste produced directly in 

reprocessing and any solid waste derived from the liquid that contains a combination of transuranic waste 

and fission products in concentrations requiring permanent isolation (10 CFR Part 72.3 and DOE Order 

5820.2A). 

1.2 Background 

This study was performed in response to the Congressional request to examine whether or not regulations 

from the DOT should be issued to all carriers of HLRW and SNF that shipments be moved by dedicated 

train. Specifically, Section 116 of the Hazardous Materials Transportation Uniform Safety Act 

(HMTUSA) of 1990 states: 

Transportation of Certain Highly Radioactive Materials 

(a) Railroad Transportation Study. The Secretary, in consultation with the Department of 

Energy, the Nuclear Regulatory Commission, potentially affected States and Indian Tribes, 

representatives of the railroad transportation industry and shippers of high-level radioactive 

waste and spent nuclear fuel, shall undertake a study comparing the safety of using trains 

operated exclusively for transporting high-level radioactive waste and spent nuclear fuel 

(hereinafter in this section referred to as ‘dedicated trains’) with the safety of using other 

methods of rail transportation for such purposes. The Secretary shall report the results of the 

study to Congress not later than one year after the date of enactment of this section. 

(b) Safe Rail Transport of Certain Radioactive Materials. Within 24 months after the date of 

enactment of this section, taking into consideration the findings of the study conducted 

pursuant to subsection (a), the Secretary shall amend existing regulations as the Secretary 

deems appropriate to provide for the safe transportation by rail of high-level radioactive waste 

and spent nuclear fuel by various methods of rail transportation, including by dedicated train.

FRA consulted with the DOE, NRC, affected States and Indian Tribes, representatives of the railroad 

industry, and other stakeholders on September 28 and 29, 1992, in Denver, CO (see stakeholder positions 

in Appendix B). The results of those consultations have provided useful information for the analyses 

17 
reported in this document. Ongoing analyses conducted by other concerned agencies, such as DOE and 

NRC, warranted modifications in analyses conducted by FRA. This report employs the most recently 

available data from all sources through 2001. 

For the purposes of this study, safety is defined in terms of the risk of the loss of human life. This 

analysis considers train crews, escorts, yard personnel, emergency responders, vehicle occupants at grade 

crossings, and wayside population. Loss of life of any of these individual counts are equal. 

1.3 Definitions of Spent Nuclear Fuel and high level Radioactive Waste 

SNF 

SNF is “fuel that has been withdrawn from a nuclear reactor following irradiation, the constituent 

elements of which have not been separated by reprocessing” [DOE, 2002a]. 

SNF comes from commercial nuclear power plants, research reactors, and nuclear powered U.S. Navy 

warships. SNF also results from the production activities of the DOE-owned reactors, reactor design 

testing, and energy research. Currently, most SNF assemblies are stored at the reactor site in pools of 

water, above-ground vaults, or concrete casks; some are shipped to another temporary storage site. 

HLRW 

HLRW is “(1) The highly radioactive material resulting from the reprocessing of spent nuclear fuel, 

including liquid waste produced directly in reprocessing and any solid material derived from such liquid 

waste that contains fission products in sufficient concentrations; and (2) Other highly radioactive material 

that the Commission, consistent with existing law, determines by rule requires permanent isolation” 

[DOE, 2002a]. 

HLRW is stored temporarily in underground tanks and vaults at Government sites. Four locations in the 

United States currently process and store the majority of HLRW: Hanford, Washington, the Idaho 

National Engineering and Environmental Laboratory, the Savannah River site in South Carolina, and the 

West Valley Demonstration Project in upstate New York. 

Shipment Assumptions 

Based upon the current plan presented by DOE in the “Final Environmental Impact Statement (FEIS) for 

a Geological Repository for the Disposal of Spent Nuclear Fuel and High-Level Radioactive Waste at 

Yucca Mountain” [DOE, 2002b], this report assumes the following: 

• Commercial Spent Fuel (CSF). By 2046 the projected total quantity of CSF to be shipped to the 

Yucca Mountain facility is 63,000 metric tons heavy metal (MTHM). CSF is shipped in fuel 

assemblies that are bundled together and shipped within a rail shipping cask. Shipments of CSF 

are assumed to contain a number of assemblies per large shipping container (see Figure and 

Figure ). 

• DOE SNF and HLRW. The FEIS shows that in the current plan the total volume of inventory 

DOE SNF to be shipped is 2,333 MTHM and 8,315 canisters of HLRW. The DOE SNF is 

placed within individual canisters (see Figure 2 and Figure 3), and five canisters are shipped in a 

rail cask. HLRW is assumed to be shipped in either small 1.5-ft (46-cm) or large 2-ft (61-cm) 

diameter canisters; DOE assumes that either nine small or four large canisters would be shipped 

per railcar cask shipment. 

18 
Figure 2. Cask Systems–DOE Multi-Purpose Canister (MPC) and Mitsubishi Dual Purpose Cask 

Figure 3. MPC and Overpack 

The total radioactivity of shipments of any of these three types of material depends upon the content of 

the material and the volume in the shipping container. CSF represents the bulk of material to be shipped, 

and the highest radioactivity of materials to be shipped per shipment. The analyses in this study, 

therefore, focus on the safety of shipment of typical CSF in terms of incident-free and accident-related 

radiation exposure. FRA assumes that these effects are an upper bound on the likely outcome of 

shipments of commercial SNF, DOE SNF, or HLRW. Aggregate risk projections reflect the frequency of 

all types of shipments. 

19 
1.4 Past, Current, and Future SNF Shipments 

SNF shipments in the United States have a long history of safe transport. This chapter will discuss past, 

current, and future SNF/HLRW rail shipment procedures and volumes. 

1.4.1 Experience and Technology for Safe Shipments 

More than 3,000 shipments of SNF were made between 1965 and 2001 by truck and rail. Since 1949, 

nine incidents involving the transportation of SNF and HLRW by rail have occurred. Six of the incidents 

were train accidents; however, none of the cases resulted in damage to the cask, release of material, 

deaths, or injuries. The three non-accident related incidents involved leakage of slight amounts of waste 

water or other material. It is important that the most recent accident occurred more than 15 years ago and 

that the most recent leakage occurred more than 25 years ago. This may be an indication that 

enhancements to cask design, material handling procedures, and other safety enhancements have had a 

positive effect in improving the safety of railroad shipments of nuclear materials. 

Between 1979-1997, there were 1,334 commercial SNF shipments totaling over 1,102 tons (1,000 metric 

tons). Most of these were relocations of SNF to facilities that could provide interim storage. Only 11.5 

percent of the shipments were by rail, but these accounted for 75.5 percent of the tonnage [NRC, 1998]. 

To date, over 700 shipments of naval SNF have also occurred, mostly to the Idaho National Engineering 

Laboratory. All of these shipments were by rail; more than half were moved in regular trains and the rest 

in dedicated trains. 

1.4.2 Future Shipments 

By the year 2046 DOE estimates that waste inventories will be between 63,000 and 105,000 MTHM for 

commercial SNF; 2,333 to 2,500 MTHM for DOE SNF; and 8,315 to 222,280 canisters of HLRW [DOE, 

2002b]. This material will be transported to the national repository either directly from 72 commercial 

and 5 DOE sites across the United States or indirectly via interim storage and consolidation facilities (see 

Figure 4). The number of rail shipments for SNF and HLRW over a 24-year campaign could range from 

300 to 18,300 depending on the mode emphasis of the shipping campaign. This traffic would at most 

average two shipments per day, depending primarily upon the presence and location of an interim facility 

(or facilities).16

1.4.3 Past Operational Restrictions 

Historically, SNF has been shipped by ordinary freight trains, freight trains operating under restrictions, 

and dedicated trains. Ordinary freight trains have ranged between 50 to over 100 cars in length, have 

traveled at or below maximum allowable speeds, and have operated under multiple methods of train 

control (including cab signals, wayside signals, track orders, and in dark territory). Traditionally, 

shipments of SNF by regular freight train were accomplished as with any other commodity. In some 

cases, SNF shippers required some modifications to the regular train. These modifications included 

requirements for buffer cars, speed restrictions, and some other operational restrictions, such as a 

requirement that only one train move when opposing or passing movements are made. 

 

16 Rail shipments to the proposed private fuel storage (PFS) facility in Utah will alter these numbers considerably since SNF 

would move there first and be moved again to the Yucca Mountain Repository when it opens. 

20 
Source: [DOE, 2002b], Figure 1-1 

Figure 4. SNF Shipment Locations 

Not all of the operational restrictions analyzed in this study have been typically employed in shipping 

SNF or HLRW. Since accident probabilities and consequences are inevitably based upon comparisons 

with the normal transportation scenario, however, it is worthwhile to describe transport by normal freight 

as well as by the method of shipment of SNF and HLRW as prescribed by DOE. SNF and HLRW have 

been shipped using diverse rail services (ranging from dedicated trains to regular freight) and under 

various operational restrictions. The regulatory and legal history of rail transport of SNF illustrates some 

of the issues raised to date. 

AAR Recommendations of 1974. Until the mid-1970s, rail shipments of radioactive material (RAM) were 

handled routinely in regular train service. In March 1974, the Board of Directors of AAR approved a 

recommended operating practice for the transportation of SNF, "Shipments of casks containing irradiated 

spent fuel cores should move in special trains containing no other freight, not faster than 35 mph (56.3 

km/hr). When a train handling these shipments meets, passes or is passed by another train, one train 

should stand while the other moves past not faster than 35 mph (56.3 km/hr)." Shortly thereafter, a 

number of railroads took actions, which had the effect of imposing both the use of dedicated trains and 

special train tariffs that were much higher than regular train rates. Some railroads sought to avoid 

handling these shipments altogether. These actions were challenged by the Energy Research and 

21 
Development Administration (one of DOE's forerunners), U.S. Department of Defense (DOD), NRC, 

numerous electric utilities, and other constituents of the nuclear power industry. 

Interstate Commerce Commission (ICC) Decision of 1977. A number of proceedings before the ICC17

and in the courts followed. The case that most directly and comprehensively addressed the question of 

the relative safety of regular and dedicated train service was ICC Investigation Docket No. 36325 

Radioactive Materials, Special Train Service, Nationwide. In August 1977, Administrative Law Judge 

Forrest Gordon issued a decision that found that: 

1. Respondents [rail carriers] have attempted to show that because of the unusual and highly 

dangerous nature of spent fuel and radioactive waste they are justified in requiring special train 

service... 

2. Respondents have not been persuasive that special trains are safer than regular trains... In support 

of that conclusion, the judge determined the following: 

a) Casks in regular train service would be afforded the special treatment due hazardous 

materials. 

b) Surveillance of a cask car placed at the end of a regular train could be just as effective as 

similar placement in a dedicated train. 

c) Benefits of a 35 mph (56.3 km/hr) speed limit, associated with special train service, are 

illusory because average speeds are only about 20 mph (32.3 km/hr) and the poor 

condition of the roadbed of many railroads...would not lend itself to speeds much in 

excess of 35 mph (56.3 km/hr). 

d) The purpose of the requirement that one train stop while the other passes is to guard 

against the possibility that the swaying of the train may cause the extra high or wide load 

to strike the train it is passing but casks and cask cars are of normal dimensions. 

3. The record fails to demonstrate that the transportation of radioactive materials in regular train 

service involves any greater risk than the transportation of other hazardous materials for which 

no special train service is required. 

4. Risks are so small in any event that no conceivable increment of safety could be worth the 

additional cost for special train service. 

5. The record will support a finding that special trains for the carriage of spent nuclear fuel is 

unnecessary and wasteful transportation... [ICC, 1978].

Further it was held that railroads may not require special trains as a safety measure in their tariffs for 

radioactive materials.18

In a later proceeding, ICC found that complainants, DOE and DOD, were entitled to recover damages 

amounting to the difference between the assessed special train charges and regular train rates after 

November 11, 1975 [ICC, 1992b]. A 1992 ICC proceeding [ICC, 1992a] determined that damages and 

 

17 The ICC’s jurisdiction in this area has been transferred to the Surface Transportation Board (STB). 

18 Special Trains Service Decision, Radioactive Materials, Special Trains Service, 359 ICC 70 (1978); Trainload Rates on 

Radioactive Materials, Eastern Railroads, 362 ICC756 (1980), aff'd. sub nom, Consolidated Rail Corp. v. ICC, 646 F.2d642 (DC 

Cir 1981), cert denied, 455 U.S. 1047 (1981). 

22 
interest totaling nearly $10 million should be paid to the complainants by 12 railroads for 187 of the total 

319 shipments handled by special train after that date. 

Transcontinental rail shipment, from east to west of the Mississippi River or lower Missouri River or Red 

River, would have required at least one change of carriers. This would have involved several operations, 

including origin pickup, inter-train classification, road haul, block exchange, interchange transfer, enroute 

inspections (and possibly repairs), and destination delivery. Compared with other hazardous materials, 

the shipping patterns for radioactive material (SNF and HLRW) are relatively simple because a limited 

number of origins and destinations exist. Commercial shipments of SNF principally originate at the 

nuclear power reactors operated by utilities; some shipments from university and other research reactors 

also occur. This means that the primary risks associated with transport could be evaluated by comparing 

representative routes and the effects of variation in train service (either regular or dedicated) along that 

route. 

Inherent risk components of shipment of SNF and HLRW by normal freight operations have included 

derailments, collisions, and grade crossing risks. These risk components have been influenced by track 

condition, length of train, consist arrangement, and speed. Derailments and collisions have had varying 

consequences for given levels of severity of crash forces and the duration of any ensuing events such as 

fires. For this reason, some limitations on shipment of SNF and HLRW by normal freight methods have 

been imposed. These limitations are meant to reduce risk to crew members due to radiation exposure 

and/or reduce risk of collisions and/or derailments. 

The “Restricted Normal Freight” transportation operation had its origins in the indemnity agreement 

entered into in 1959 between the Atomic Energy Commission (AEC) and the railroad industry that is still 

in effect. That agreement states that radioactive shipments will “require unusual transportation services 

and handling ... under circumstances and conditions prescribed by the Government.” It then provides 

that the railroads “are willing to cooperate in moving these commodities ... provided the Commission 

[AEC] will indemnify them.” 

Consistent with the 1959 agreement, one or more of the following restrictions were imposed: 

1. Do not exceed 35 mph (56.3 km/hr) maximum speed 

2. Do not hump cars in switching yards 

3. Do not switch with locomotive detached 

4. Place car(s) on rear of train next to caboose 

5. Place car(s) in clear of rail switch points when in a yard or siding 

6. Provide protection after classification 

Additional operational restrictions have since been imposed on SNF shipments, including the restriction 

that the cask car must be surrounded by buffer cars (one front and one rear) and accompanied by a car 

carrying safety and security personnel.19

 

19 A major consideration in the Government attaching any instructions to the bills of lading is that Navy SNF contains valuable 

scientific information. These Navy shipments are not the concern of this study. The instructions over the years helped ensure

that the contents were not jostled or damaged enroute and that the information they contained was not destroyed. At the same 

time, the instructions helped ensure that the shipping program was not disrupted. The 35-mph (56.3 km/hr) speed limit was 

solely a DOD requirement (no longer required by DOD). The DOE does not request any speed limit for any of its radioactive 

shipments [ICC, 1992]. 

23 
Operational restrictions have imposed a significant limitation on the method of shipment of SNF casks by 

normal freight operations, and, in some cases, they may have exacerbated certain kinds of accident 

probability. AAR contended that the placement of the cask car and its weight may have had potentially 

harmful effects on train-track dynamics and may inhibit the safe transport of SNF by rail. Therefore, 

AAR had originally recommended the use of dedicated trains for the movement of SNF. 

AAR recommended several technological and operational approaches to manage the risks of transporting 

SNF from civilian reactors. One of the primary recommended risk reduction measures was the use of a 

train “designed to minimize the possibility of accidents” [AAR, 1995]. These trains would be run in 

concert with hot box detectors and with the best possible braking systems. AAR recommended a short 

train, capable of stopping in a short distance and operations at timetable speed. Automatic car 

identification or satellite tracking technology was also recommended, as well as onboard defect detection 

systems to monitor the performance of the train during operation. 

Dedicated trains, as recommended by AAR in 1995, were to be operated with the following restrictions: 

1. No freight other than SNF or radioactive waste was to be carried. 

2. Cask had to be placed on a flatcar surrounded by two buffer cars. 

3. The train had to have a caboose with personnel aboard who monitor the shipment. 

4. Speeds were restricted to 35 mph (56.3 km/hr). 

5. When a special train carrying SNF or HLRW was passed by another train, one of the trains had to 

remain still while the other train passed at a speed less than or equal to 35 mph (56.3 km/hr). 

AAR identified specific factors that indicated that the movement of cask cars in normal freight service 

involved additional risk. One factor was that the weight of the large multi-purpose canister (MPC) 

transportation cask system presented concern to the industry in the areas of track and bridge strength and 

train operations. DOE had specified that the gross rail load (GRL) of a loaded MPC railcar would not 

exceed 394,500 lbs (178,942 kg). The AAR standards required that any four-axle car weighing in excess 

of 263,000 lbs (119,295 kg) and six-axle cars in excess of 394,500 lbs (178,942 kg), carrying a regulated 

material, must move under special exception. Due to track weight limits (on some lines 263,000 lbs 

(119,295 kg) GRL) and bridge restrictions, the car carrying the 125-ton (113 metric tons) MPC may have 

required more than the normal four axles to distribute the weight safely over its intended route. A normal 

89-ft (27-m) flat car capable of carrying 200,000 lbs (90,718 kg) weighs about 85,000 lbs (38,555 kg) 

empty, so that even if the 125-ton (113-metric ton) cask could be carried on a four-axle car, it would have 

exceeded the 263,000-lb (119,295 kg) weight restriction mentioned above. Furthermore, cars with more 

than four axles required special design and testing and may still have required speed restrictions to 

minimize derailment potential. AAR analyzed the FRA accident database and found that six-axle cars 

derailed at approximately twice the rate of four-axle cars [AAR, 1995]20. In 1998, FRA amended its 

inspection policy and directed FRA inspection for every railcar transporting SNF at the initial terminal 

before departure and at interim inspection points along the route to ensure that the cars are free from 

defects and safe to operate. 

 

20 For purposes of this study, it was assumed that special span-bolster, eight-axle cars would be used to transport the shipping 

cask. A higher derailment rate was not assumed for these cars because: (1) they would receive special maintenance and 

operational attention and (2) the relative results between regular, key, and dedicated trains would not be affected by the 

derailment rate. 

24 
AAR expressed additional concerns about the cask certification procedure and impact test standards, with 

respect to their applicability. AAR contended that the weight of rail vehicles has increased from the 

typical 70-ton (64-metric ton) load in the 1960s and 1970s, when NRC standards were developed, to 100-

125 tons (91-113 metric ton) today, while the impact standards were developed under the assumption of 

an impact with the lighter 70-ton (64-metric ton) car. 

Although not required by ICC findings, DOE publications (such as the final request for proposals for 

transportation of SNF and HLRW) have specified that the Regional Services Contractor (RSC) may 

include special train service: 

Appendix 8 to this Section C contains additional requirements related to a forthcoming 

document entitled ‘OCRWM Transportation Policy and Procedures’ which is to be used by 

the RSC in developing its Transportation Plan. This document will provide additional 

rationale and guidance relative to overall operational protocols and will be provided to the 

RSC (Regional Service Contractor) twelve months prior to the completion of Phase A. 

Any revisions to this document will be provided to the RSC. 

The RSC’s Transportation Plan shall at a minimum, provide for: 

1. The establishment and maintenance of communication capability with other RSCs, 

DOE, States, and Tribes 

2. Identification of participating organizations including their specific functions and 

responsibilities 

3. Maximum use of special train service and advanced rail equipment features where this 

type of service or equipment can be demonstrated to enhance operating efficiency, 

dependability, cost effectiveness or lessen the potential of adverse railroad equipment 

incidents 

4. Use of buffer cars and escort/security cars which are dynamically compatible with the 

train consist 

5. Proposed primary and alternate routes in accordance with applicable NRC and DOT 

regulations for all transportation modes selected; cask modal/intermodal determination 

and designation [DOE, 1998]. 

1.4.4 Current Operational Restrictions 

AAR updated the current recommended railroad operating practices for the transportation of radioactive 

and other hazardous materials in 2001 [AAR, 2001] (see Appendix A). AAR states that trains carrying 

one or more car loads of SNF or HLRW are classified as key trains. These key trains operate along AAR 

specified key routes throughout the country. These key trains traveling along key routes have the 

following restrictions placed on their operations: 

• A key train cannot operate above 50 mph (80.4 km/hr). 

• The key train will hold the main track at meeting or passing points unless the siding or auxiliary 

track meets FRA Class 2 standards. 

• All cars in a key train movement must be equipped with roller bearings.. 

25 
In addition, AAR has imposed several other safety requirements: 

• Bearing Defect Detection. When a defect in a key train bearing is reported by a wayside detector, 

a visual inspection is required. If no defect is found in the visual inspection, the consist is 

allowed to return to service but must not exceed the speed of 30 mph (48 km/hr) until it has 

passed over the next wayside detector. If the same car triggers the next detector or it is found to 

be defective, the car must be removed from the trainset. Wayside defective bearing detectors 

shall be placed at a minimum of 40 miles (64 km) apart on key routes. 

• Track Inspection. The main track on key routes must be inspected at least twice a year to check 

for rail defects and track geometry anomalies. 

• Yard Procedures. In operating yards loaded placarded cars shall not be coupled at a speed greater 

than 4 mph (6.4 km/hr).

1.5 Previous Research 

The risk of SNF transport by rail has been a topic of interest and contention since the 1970s. Since 1977, 

at least eight studies have attempted to address the safety of both dedicated trains and regular train service 

for SNF shipments. These reports provide some relevant insights into the potential risk and risk reduction 

associated with either method. 

1.5.1 1977-1978 ICC Investigation Studies 

During the 1977-1978 ICC investigation four studies were published, under Docket No. 36325 

Radioactive Materials, Special Train Service. These were: (1) Final Environmental Impact Statement–

Transportation of Radioactive Materials by Rail [NRC, 1977a]; (2) A Safety and Economic Study of 

Special Trains for the Shipment of SNF [Battelle, 1977]; (3) Final Environmental Statement on the 

Transportation of Radioactive Material by Air and Other Modes (NUREG-0170) [NRC, 1977b]; and (4) 

An Analysis of the Radiological Risks of Transporting SNF and Radioactive Wastes by Truck and 

Ordinary and Special Trains [DOT, 1978]. Each of these studies is summarized below:

(1) Final Environmental Impact Statement-Transportation of Radioactive Materials by Rail. ICC staff, 

with support from NRC and Sandia National Laboratories, documented their analysis in this report 

in August 1977. The study addresses movement of SNF from reactors to reprocessing facilities and 

HLRW from reprocessing facilities to storage. This and later studies all found that the dominant risk 

(99.8 percent in this case) was death due to non-radiological causes, such as grade crossing 

accidents, principally associated with the extra trains created to provide dedicated service. This 

assumes that non-radiological fatalities and injuries would result (in the aggregate) if the accident 

rate for dedicated and regular trains remains constant. The study found, among other conclusions, 

that incident-free radiological risk was higher for dedicated trains. The increased risk was 

attributable to the assumption that the duration of stops for dedicated trains would be nearly the same 

as for regular trains and the assumption that the five crew members on board are more than three 

times closer to the cask car on a dedicated train.

(2) A Safety and Economic Study of Special Trains for the Shipment of SNF (prepared by Battelle for DOE 

under contract E4-76-C-06-1830). In December 1977, Battelle published findings on the safety effects 

of each of three operational restrictions usually associated with dedicated trains: (1) excluding other 

freight, (2) limiting speed to 35 mph (56.3 km/hr), and (3) requiring one train to stop during a pass. 

Battelle’s examination of FRA accident data showed no indication that safety was improved by 

employing dedicated trains. The Battelle analysis determined that the likelihood of cask involvement in 

26 
a severe fire is virtually the same for regular and dedicated trains. This assumption may be faulty 

because the consist of a regular train could contain much more flammable material than that of a 

dedicated train and dedicated trains spend less time in yards than regular trains. The only flammable 

material carried on dedicated trains is the diesel fuel in the locomotive tanks (typically 2,500 gallons 

(9,463 liters)), located under the locomotive unit between the trucks. Regulations (49 CFR 174.85) 

require at least one non-placarded car (combustibles excepted) to be placed between the cask car and the 

locomotive. In contrast, a cask in a regular train may be placed a similar distance away from a loaded 

tank car containing ten times that amount of flammable material. In addition, it is possible that other 

cars in the train consist may legally carry other hazardous materials. The effect may, in fact, be an 

increase in the risk of cask car involvement in a severe fire in a regular train.

(3) Final Environmental Statement on the Transportation of Radioactive Material by Air and Other Modes 

[NUREG 0170]. The NRC published this study in December of 1977. The report addresses issues of 

alternative modes of rail shipment (dedicated and regular train service) noting that no data existed on the 

comparative safety of dedicated trains. The authors determine the maximum possible benefit from using 

dedicated trains by assuming that no radiation dosage would be associated with these trains and no 

accidents would occur while they were in use. The risk associated with transportation of SNF and waste 

by regular train for 1985 was calculated, and it was then assumed that dedicated trains would eliminate 

that risk entirely. The maximum reduction in risk amounted to 0.0365 LCFs per year–one LCF avoided 

every 30 years. Based upon this health effect benefit and an estimate of the additional costs, the authors 

concluded that the benefit/cost ratio for use of dedicated trains was approximately 1:19. 

(4) An Analysis of the Radiological Risks of Transporting SNF and Radioactive Wastes by Truck and 

Ordinary and Special Trains. In June 1978, SNL published the results of this study done for NRC. In 

what was essentially a refinement of the NUREG-0170 work, the authors estimated the change in 

radiological impacts due to substituting dedicated trains for regular trains in nuclear fuel cycle 

transportation for 100 light water reactors (LWRs). Dedicated (special) trains were assumed to travel at 

speeds less than 35 mph (56.3 km/hr), operate under a passing restriction that would hold other trains 

while the dedicated train moved, and carry a consist containing no freight other than SNF. The authors 

also assumed that collisions and derailments with impact speeds greater than 30 mph (48 km/hr) would 

be eliminated. Second, the passing restriction was assumed to completely eliminate the raking collision 

probability and derailment risk due to passing trains. Finally, the consist restriction was assumed to have 

no significant effect upon accident rates but have a possible effect on the likelihood that the cask might 

be involved in a fire. For the special train case, rail shipments account for 5 percent of the accident-free 

LCFs and 46 percent of the accident-related LCFs. Due to assumptions about crew proximity, 

protection, and the duration of their exposure during a dedicated train shipment, the study concluded that 

dedicated trains had lower accident risk but higher non-accident risk than regular trains.

1.5.2 1980s Studies 

Two relevant studies done in the mid-1980s are Are Special Trains Really Safer? [ADL, 1984] and A 

Revised Rail-Stop Exposure Model for Incident-Free Transport of Nuclear Waste [DOE, 1986]. The 

following summarizes these studies: 

(1) Are Special Trains Really Safer? [ADL, 1984]. FRA accident data for 1983 was used to estimate the 

accident frequency and spill size effects of using regular and dedicated trains for shipment of hazardous 

materials (of all kinds). These data examine tank car incidents, the effect of different shipment modes on 

the accident involvement, and release rates per million train miles for trains carrying these materials. 

Boghani concluded that dedicated trains are sometimes, but not always, safer. He further concluded that 

case-specific analyses should be conducted to determine which method of shipment was preferable for a 

specific shipment. 

27 
(2) A Revised Rail-Stop Exposure Model for Incident-Free Transport of Nuclear Waste [DOE, 1986]. SNL 

examined the effect of the assumptions describing stopped time on shipment duration and radiological 

exposure. As noted in the 1978 SNL study, the effect of crew exposure during shipments is one of the 

largest determinants of risk calculated by RADTRAN (the computer program developed by SNL). This 

report provides a description of the assumptions and algorithms now incorporated into the model, which 

operates as part of RADTRAN. Dedicated and regular trains were compared for radiological, incidentfree risk only. The assumed speeds for both types of trains were identical, but a considerable difference 

existed in both the fixed and distance-dependent stopped time. The close-proximity crew dose factor 

associated with handling and inspecting casks and cask cars in regular trains was estimated to be 16 times 

greater than for dedicated trains. Overall dose (stopped plus moving) for regular trains was found to be 

nearly four times that of dedicated trains. 

1.5.3 2000 to Present Studies 

In 2000 and 2001 revised studies of spent fuel transportation were conducted. Two of these studies, the Final 

Environmental Impact Statement for a Geologic Repository for the Disposal of Spent Nuclear Fuel and HighLevel Radioactive Waste at Yucca Mountain [DOE, 2002b] and Reexamination of Spent Fuel Shipment Risk 

Estimates, NUREG CR6672 [NRC, 2000], provided significant revisions to previous estimates of radiological 

risks from transportation of spent fuel and HLRW. The following summarizes these studies: 

(1) Final Environmental Impact Statement for a Geologic Repository for the Disposal of Spent Nuclear Fuel 

and High-Level Radioactive Waste at Yucca Mountain, Nye County, Nevada [DOE, 2002b]. DOE 

provided an up-to-date estimate of the number of shipments, type of fuels (high, medium, and low 

burnup), and the radiological and non-radiological risks resulting from transportation of this inventory of 

HLRW and SNF to Yucca Mountain by rail, truck, or a combination of the two. DOE evaluated the 

potential risk reduction from use of dedicated trains in a non-quantitative manner, comparing the hazards 

to crews, wayside population, and inspectors using either dedicated or regular trains. Table 2 illustrates 

the main areas of comparison between dedicated and regular train service evaluated by DOE. The 

basis of comparison between these two methods of service were accident rates, incident-free 

exposure, accident related exposure, security, and utilization of resources. While DOE found a slight 

(or greater) advantage for dedicated trains on nearly every one of the attributes, they concluded that 

the differences between the two types of service were not substantial enough to warrant requirement 

of dedicated trains. They stated that: 

... available information does not indicate a clear advantage for the use of either 

dedicated trains or general freight service. Thus, DOE has not determined the 

commercial arrangements it would request from railroads for shipment of spent nuclear 

fuel and high-level radioactive waste. Table 2 compares the dedicated and general freight 

modes. These comparisons are based on the findings of the U.S. Department of 

Transportation study and the Association of American Railroads.21

 

21 [DOE, 2002b], Appendix J page J-75. 

28 
Table 2. Comparison of General Freight and Dedicated Train Service 

Attribute General Freight Dedicated Train 

Overall accident rate for 

accidents that could damage 

shipping casks 

Same as mainline railroad accident rates. Expected to be lower than general freight 

service because of operating restrictions and 

use of the most up-to-date railroad 

technology. 

Grade crossing, trespasser, 

worker fatalities 

Same as mainline railroad rates for fatalities. Uncertain, greater number of trains could 

result in more fatalities in grade crossing 

accidents. Fewer stops in classification yards 

could reduce work related fatalities and 

trespasser fatalities.*

Security Security provided by escorts required by 

NRC regulations. 

Security provided by escorts required by 

NRC regulations; fewer stops in 

classification yards than general freight 

service. 

Incident-free dose to public Low, but more stops in classification yards 

than dedicated trains. Classification yards, 

however, would tend to be remote from 

populated areas. 

Lower than general freight service. 

Dedicated trains could be direct routed with 

fewer stops in classification yards for crew 

and equipment changes. 

Radiological risks from 

accidents 

Low, but greater than dedicated trains. Lower than general freight service because 

operating restrictions and equipment could 

contribute to lower accident rates and 

reduced likelihood of maximum severity 

accidents. 

Occupational dose Duration of travel influences dose to escorts. Shorter travel time would result in lower 

occupational dose to escorts. 

Utilization of resources Long cross-country transit times could result 

in least efficient use of expensive 

transportation cask resources; best use of 

railroad resources; least reliable delivery 

scheduling; most difficult to coordinate state 

notifications. 

Direct through travel with on-time deliveries 

would result in most efficient use of cask 

resources; least efficient use of railroad 

resources. Railroad resource demands from 

other shippers could lead to schedule and 

throughput conflicts. Easiest to coordinate 

notification of State officials. 

Source: Table J-25. Comparison of General Freight and Dedicated Train Service [DOE, 2002b]. 

* Trespasser fatalities on the mainline and in yards could be reduced by speed restrictions and fewer yard stops.

29 
(2) Reexamination of Spent Fuel Shipment Risk Estimates, Vols.1, 2 [NRC, 2000]. This is a comprehensive 

update to the original NUREG 0170, Final Environmental Impact Statement. The purpose of this study 

was to identify how the risk estimates constructed in NUREG 0170 [NRC, 1977b] may have varied over 

time, both due to improved understanding of cask performance and resulting from the application of very 

conservative assumptions in the original study. SNL provided substantial updates to the significant 

parameters that determine human health risks due to radiological exposure; these included source terms 

describing the level of radioactivity likely to be released given an accident, the likely effects of impacts 

and fires on cask integrity, and the probability of the events resulting in high-velocity impacts (over 60 

mph (96.4 km/hr) onto an unyielding surface) or high-temperature (1,832° F (1,000° C)), long duration 

(30 minutes or more) fires. Cask response to external loads was modeled using finite element methods, 

and thermal responses were modeled in terms of the time required to fail the seal on the cask. The 

duration of fires, temperatures, and transfer of heat from the external source to the internal contents were 

detailed in SNL’s model. Based upon their analyses, SNL concluded that accident dose risks are 

“negligible when compared with incident-free dose risks.”22 SNL’s conclusions in this report are 

different from NUREG 0170 and the Modal Study. Based upon SNL’s calculations for rail transport, 

NUREG-0170 Model I accident population dose risks are approximately 10 times larger than the rail 

accident risks estimated using Modal Study rail accident source terms, which are approximately 4 

times larger than the risks estimated using NUREG-0170 Model II source terms, which are 

approximately 50 times larger than the risks estimated using the rail accident source terms developed 

by this study.23 The significance of these new conclusions with respect to dedicated train is evident 

in the overall effect of dedicated service on the duration of point-to-point service. Longer shipment 

duration requirements (in regular train service) expose wayside populations, crews, and others to 

higher cumulative doses since the dominant exposure results from incident-free exposures. Shipment 

methods that reduce overall shipment duration reduce risk. 

1.6 Methodology 

These studies include an assessment of normal incident-free train operations, as well as select accident 

conditions. The operational definition of safety for this study has been to determine the total risk incurred 

by all people involved in SNF and HLRW transportation and to quantitatively measure the difference in 

this risk when either a regular or dedicated train is employed. Safety risks (specifically latent cancer 

fatalities) were considered for the train while moving and while at rest, including the effects of 

radioactive materials transport on anyone exposed during the transportation process, such as the general 

population, train crews, railroad yard employees, and security escorts.

Unlike most hazardous materials, SNF and HLRW shipments pose a small risk at all times during 

transport. This is because even the most resilient shipment cask will allow some amount of radioactivity 

to be emitted. While well within regulatory limits of 10 mrem/hr at 3.3 ft (1 m), this very low level of 

radioactivity may pose a small health risk. Potential casualties from accidents involving SNF or HLRW 

shipments could pose larger risks, such as exposure to elevated radiation doses due to damage to the 

container or to the container contents or, less likely, direct exposure to SNF or HLRW materials due to 

failure of a cask. 

 

22 NUREG CR6672, page 9-2. 

23 ibid, page 9-3. 

30 
To compare the relative risk between dedicated and regular train service, the total expected radiation dose 

to the public (assuming no accident) has been calculated for shipments of SNF by dedicated or regular 

train, and the consequences have been compared. Accident probabilities for all types and severities of 

train accidents are calculated, and the consequences of typical events of the severity of these scenarios are 

calculated. The likelihood of having an accident of a given severity and consequence is then compared 

for regular and dedicated trains. 

1.7 Report Overview 

This chapter provides a brief characterization of the original requirement for this study and the 

circumstances under which SNF and HLRW shipments were to be made. This chapter presents 

definitions of the important components of the study, including the characteristics of dedicated and 

regular trains and their derivation. In addition, definitions of the characteristics of comparison (LCFs, 

injuries, and fatalities due to accidents) were provided and their derivation explained. 

Chapter 2 provides a description of the calculation of comparative safety of dedicated, regular, and key 

train transport of SNF and HLRW, under the assumption that no accident occurs during transport. 

RADTRAN, a computer model, was used to calculate the consequences based on inputs from the Volpe 

Center, SNL, industry standards, historical data, government databases, and expert opinions [SNL, 1998]. 

The methodology of calculation, including the computer program used to calculate population exposure, 

is described. This chapter also includes input parameters and assumptions for the calculation. Other 

radiological and non-radiological consequences, such as environmental damage and property damage, 

were not considered. 

Chapter 3 provides an analysis of accidents and their likely effect on SNF containers. In this chapter an 

analytical method is used to describe expected forces from collisions, falls from bridges, derailments 

resulting in impacts on the cask, and fires. The analytical method employed in this chapter determines 

which objects and velocities or heights pose a threat to SNF container integrity. 

The probability that these events might occur is then estimated using event trees, based upon historical 

accident records, and railroad bridge characteristics provided for the State of California. These 

probability values are specific to shipment methods and are, therefore, segregated to event trees that 

represent either dedicated or regular train shipments. These event trees reflect the cumulative probability 

that a severe accident (one that results in forces in excess of the compliance test regulatory limit) occurs. 

In incident-free transport, the duration and number of stops during shipment and placement of the cask in 

the train have a significant bearing on the total population dose. In accident scenarios, the consequences 

of failure are invariant with respect to the type of service since the same population exposure will ensue 

from a cask release. The accident analysis, therefore, focused on comparing the likelihood of severe 

accidents under the three methods of shipment and not on their aggregate consequences. Examples of 

each type of accident are characterized in terms of radiation dose (person-rem) and LCF; however, the 

total accident-related LCF for all routes were not calculated. 

31 
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32 
2. Incident-Free Risk Analysis 

2.1 Incident-Free RISK Methodology–Radiological Consequences and Risk Calculations 

This analysis estimates radiological risks associated with incident-free transportation of SNF by rail. The 

consequences of incident-free transportation are the estimated population radiation doses for the various 

population groups surrounding the cask being analyzed. As shown in Figure 5, the radiological 

consequence of an SNF shipment is a function of the selected routes, the cask design, and the package 

dose rate (cask emission), the size of impacted populations (number of persons exposed), the population 

distance from the cask, the total exposure time, and the amount of shielding between the cask and 

exposed populations. 

Package Dose Rate 

(Section 2.1.3)

Impacted Populations 

(Section 2.1.4)

Consequences– 

Radiological Health 

Impact (person-rem)

Exposure Time 

(Train Speed/Stop Duration) 

(Section 2.1.6)

Incident-Free 

Radiological Risk–

Number of LCFs

Shielding Factors

(Section 2.1.7)

Selected Routes 

(Section 2.1.1) 

Cask and Cask Material 

(Section 2.1.2)

Figure 5. Incident-Free Risk Calculation 

Though very well shielded, SNF casks continuously emit low levels of radiation throughout all phases of 

transportation. Radiation exposure to crew, handlers, yard personnel, and wayside population will occur 

in all SNF movements under all service types even under those circumstances where no accident has 

occurred. Since a cask will always have some level of emission, for incident-free transportation, the 

exposure probability is assumed to be 1. Incident-free transportation consequences and risk are thus 

indistinguishable. 

Incident-free risk was calculated using RADTRAN 5, a set of models developed by SNL for the analysis 

of the consequences and risks of radioactive material transportation by highway, rail, air, and waterborne 

modes. RADTRAN was first developed by SNL in 1977 in conjunction with NUREG-0170, Final 

Environmental Statement on the Transportation of Radioactive Material by Air and Other Modes [NRC, 

1977b; DOE 1982]. RADTRAN combines user-determined demographic, transportation, packaging, and 

material data with health physics data to calculate the expected radiological consequences of transporting 

radioactive materials. The incident-free RADTRAN calculations produce expected values of population 

dose with the package, population distribution, and transportation models. For analysis of incident-free 

conditions in RADTRAN, the package dose rate and packaging-specific characteristics are used to model 

33
a package (or shipment) of radioactive material as a modified point source and, for receptor distances less 

than two characteristic package dimensions from large packages, as a line source. Transportation system 

characteristics are incorporated into a rail mode-specific model, which uses a set of input parameters to 

describe the population along the route and at stops, and other mode-dependent characteristics, such as 

vehicle velocity and stop duration. Population densities for each route segment must be defined by the 

user, in addition to the characteristics each sub-population (e.g., passenger, crew, rail workers, general 

population) that receive radiation doses. The magnitudes of the calculated doses depend on variables, 

such as population density, distance traveled, and vehicle speed. The values describing these potentially 

exposed subgroups may be varied by population-density zone (urban, suburban, and rural). The user is 

given considerable latitude in adjusting parameters for analysis, but the quality and quantity of the 

available data limits the accuracy of the results. Details of RADTRAN calculations can be found in the 

RADTRAN 5 User Manual [SNL, 1998]. Several factors were input into the RADTRAN model. The 

following sections describe the values used and the source for each. 

Results are provided for in-transit (off-link and on-link) radiation doses as well as for radiation doses for 

stops. Off-link doses are those received by persons on the ground who are within 875 yds (800 m) of a 

passing train. On-link doses are those received by passengers on trains which pass the SNF cask carrying 

train and those received by the crew and escorts on board the SNF cask carrying train. Stop doses are 

those received by persons on the ground or by crew and escorts who are within 875 yds (800 m) of the 

SNF carrying train while the train is at rest. 

2.1.1 Selected Routes 

More than 20 percent of the Nation’s electricity is produced by more than 100 nuclear power plants 

located around the country. Because commercial spent fuel is currently stored in nearly every region of 

the United States, most states have potential transportation routes to Yucca Mountain. For this analysis, 

six routes were chosen to be representative of overall SNF transport (see Table 3). All six of the selected 

route origin points are locations of nuclear power plants or waste repositories with existing commercial 

SNF or DOD HLRW (see Figure 6). The destination point for each of the selected routes was Yucca 

Mountain. 

Table 3. Routes Used in the Analysis 

Route Number Origin Destination 

1 Humboldt Nuclear Power Plant, CA Yucca Mountain, NV 

2 Crystal River Nuclear Power Plant, FL Yucca Mountain, NV 

3 Dresden Nuclear Power Plant Dock, IL Yucca Mountain, NV 

4 River Bend Nuclear Power Plant, LA Yucca Mountain, NV 

5 Seabrook Nuclear Power Plant, NH Yucca Mountain, NV 

6 Hanford Repository, WA Yucca Mountain, NV 

Although at this time no preferred routes have been selected by DOE for spent fuel shipments to Yucca 

Mountain, major east-west rail links can be identified as likely candidates. The links from each origin 

and destination pair were determined using Oak Ridge National Lab’s (ORNL) Interline model.24 The 

selected routes are the most likely traveled routes and are representative in terms of their geographic 

location and length of route. 

 

24 Interline is an interactive tool for simulating routing practices on the U.S. rail system. Oak Ridge National Laboratory developed this 

routing model. 

34
Figure 6. Selected SNF Shipment Routes 

2.1.2 Cask and Cask Material 

Cask Description 

Spent fuel packages provide the bulk of the insurance against radioactivity release. Irradiated or spent 

fuel is moved in shielded containers referred to as casks. They are Type B [49 CFR 173.413/10 CFR 71] 

packaging and must be certified by either NRC [49 CFR 173.471] or DOE. These casks are authorized 

for shipment under DOT regulations. For this analysis, a 125-ton (113-metric ton) MPC system was 

used. 

Consist Description 

Three types of trains are considered in the analysis: regular, key, and dedicated trains (see Figure 7). 

This report assumes that the cask car(s) will be surrounded by two buffer cars and accompanied by an 

escort car. This complement of cars, referred to as the cask consist, in addition to the locomotive(s), 

comprises a dedicated train. A regular or key train will include the cask consist, locomotive(s), and any 

number of additional cars. 

35
 locomotives other consist cars buffer car cask car buffer car escort car other consist cars

62 m 15 m 2 m 10.3 m

Dedicated Train

Regular or Key Train

Figure 7. Train Consist 

2.1.3 Package Dose Rate (Source Strength) 

NRC and DOT regulate packaging, transport, and disposal of radioactive materials by all modes of 

transportation in the United States. Regulations promulgated by NRC are contained in 10 CFR 71-73; 

regulations promulgated by DOT are primarily contained in 49 CFR 171-178. These regulations establish 

maximum permissible package dose rates and maximum permissible dose rates to vehicle crew members. 

Characteristics of radioactive material that affect incident-free transportation are the package dose rate 

and the fractions of gamma and neutron radiation. The package dose rate is expressed as a transportation 

index (TI) for certain package types. TI is defined as the highest radiation dose rate in millirem per hour 

(mrem/hr) from all penetrating radiation at 3.3 ft (1 m) from any accessible external surface of the 

package, rounded to the highest tenth (49 CFR 173.403). For the purposes of this analysis, it was 

conservatively assumed that the dose rate is the regulatory limit of 10 mrem/hr at 3.3 ft (1 m). The 

estimated dose rate for the MPC cask selected for this analysis is below this regulatory limit. 

2.1.3.1 Package Dose Rate Estimations for Affected Populations 

The package dose rate and packaging-specific characteristics are used to model a shipment of radioactive 

material as a modified point source for distant receptors and as a line source for close proximity receptors. 

Exposed persons at stops are modeled as being located at a given distance from a stationary source for a 

specified amount of time (point source model). Crew members, classification workers, and inspectors 

work in close proximity to a package, so the dose for these groups is calculated with a line-source model. 

Point Source Model. The formulation for estimating an incident-free population dose from radioactive 

materials in most cases is based on an expression for dose rate as a function of distance from a point 

source (radiation in all directions with equal magnitude). For such a source, dose rate is inversely 

proportional to the square of the distance from the source. 

Line Source Model. For exposure groups such as classification workers and inspectors who work in 

close-proximity (within 10 m) to the cask, a line-source approximation model is used. A line source is 

defined as a one-dimensional source that emits radiation normally along its entire length. A line source 

model gives a conservative approximation of actual dose rate measured at distances of less than twice the 

characteristic package dimension (length). 

The implementation of these models in RADTRAN is available in the user manual [SNL, 1998]. 

2.1.4 Impacted Populations 

While moving and at rest, cask emissions can potentially impact various groups of people to varying 

degrees. The populations considered in this analysis are: 

36
• General population, including individuals residing and working near the rail lines (wayside) over 

which the cask passes and people who live near yards and sidings where the cask stops 

temporarily. 

• Persons on trains sharing the route with the SNF shipment. 

• Vehicle occupants at railroad grade crossings along the shipment route. 

• Train crew located in the lead locomotive on the train containing the SNF shipment. 

• Escorts on the train containing the SNF shipment; experts and/or guards who monitor the cask 

from the nearby personnel car. 

• Railroad personnel who work in close proximity to the cask in classification yards and inspect the 

train at various points. 

• Other rail yard workers, including rail workers other than classification personnel and inspectors 

working in rail yards where the train stops but not in close contact with the shipment. 

Each of these groups can be impacted by emissions from SNF casks on standing or moving trains, and 

each group has different exposure levels and durations (see Table 4). Members of train crews or escorts 

will be exposed to any external radiation field around a cask for the duration of a trip. The cask may be 

inspected and classified during transport by inspectors or rail yard workers. Populations beside the rail 

route and passengers on passing trains will be exposed as the train passes. The dose to each of these 

population subgroups was calculated. 

Table 4. Impacted Population Groups 

Incident-Free 

Impacted Population Group 

In-Transit 

(Moving) Dose Stop Dose 

General (Wayside) Population Along Route25 

General (Wayside) Population Near Stops 

Train Passengers Sharing Route 

Vehicle Occupants at Grade Crossings 

Train Crew  

Shipment Escorts  

Handlers/Inspectors 

Other Rail Yard Workers  

2.1.4.1 Impacted Population Number Determination 

Population numbers or population densities were defined for each route segment, along with the 

characteristics of each of the sub-populations that receive doses while the cask is stopped or in-transit. 

The following describes the values used for the general population. 

Wayside Population. High resolution population data from the 2000 U.S. Census was used to determine 

wayside population densities. For the general population along the route, an average population density 

 

25 Although in reality the transportation of a radioactive material will involve passage through variable population densities, RADTRAN 

is given three population density zones (rural, suburban, and urban) aggregate all route segments. The total population dose resulting 

from the trip is made up of the sum of the doses received in each population-density zone or route segment. 

37
within a 1-mi (1.6 km) bandwidth of the selected rail line was used for each route segment. Population 

densities were calculated by selecting census blocks through which the rail route passes and assuming an 

even density distribution (see Figure 8). 

0.5 mile 

Census 

Block 1 

Census 

Block 2 0.5 mile 

(0.8 km) 

Figure 8. Population Density Selection 

Table 5 shows the census-based population density values used for each of the six routes. 

Table 5. Average Population Density 

 persons/sq mi (persons / km2) 

Route Urban Suburban Rural 

1 6,237 (2,408) 1,164 (449) 26 (10) 

2 5,641 (2,178) 976 (377) 38 (15) 

3 5,169 (1,996) 1,006 (389) 26 (10) 

4 4,964 (1,917) 919 (355) 30 (12) 

5 6,109 (2,359) 1,028 (397) 28 (11) 

6 4,744 (1,832) 1,307 (505) 17 (7) 

Source: Census 2000. 

If the transport vehicle stops for crew change, freight transfer, refueling, or inspection, persons in the 

vicinity of the stop point can be exposed. Since rail stops usually occur in rail yards, the population in 

and near a rail yard are modeled as uniform populations distributed around the rail shipment, and dose is 

integrated over this population. For rail stops, public dose is estimated using the suburban population 

density for the route because most rail yards are located in less densely populated areas. 

Train Passengers Sharing Route. Train density and train occupancy data from the 1996 Rail Garrison data 

were used to determine the number of persons likely to be sharing the railway with the SNF shipment. 

Table 6 shows data for average train density rates. 

Table 6. Average Passenger Train Density 

Urban Suburban Rural

Average Train Density* 0.4 trains/hr 0.2 trains/hr 0.14 trains/hr 

* Source: Rail Garrison Data 1996. 

Vehicle Occupants at Grade Crossings. Vehicle occupants on each side of the railroad link, especially at 

highly trafficked crossings, could be exposed to a passing SNF train during the time the crossing gates are 

down. The Railroad/Highway Grade-Crossing Inventory estimates an average of greater than 2,000 

vehicles per day traversing each public crossing. 

38
The top 33 percent of crossings (by volume) handle 5,700 vehicles per day or almost 60 per average 15-

minute period. Crossings in the bottom 67 percent (by volume) average 500 vehicles per day, about 5 per 

15-minute interval. This possibility is less likely for highly congested urban crossings. While this could 

be considered the maximum vehicle exposure for a passing cask-carrying train, a maximum of only ten 

vehicles (five vehicles on each side of the crossing) would be within a 98.4 ft (30 m) limit, which would 

need to be analyzed separately; the rest would be assimilated in the general urban population (off-link) 

dose. 

To calculate the maximum dose at urban grade crossings for each route and for trains of each speed 

restriction, RADTRAN’s maximum individual dose rate routine was utilized (see Table 7). The 

individual maximum dose was multiplied by the number of expected vehicle occupants at the urban grade 

crossings on the route-run. The total dose was calculated as the number of urban crossings on the route 

times the number of vehicles at each crossing (10), times the vehicle occupancy (1.63 persons per 

vehicle). The number of crossings equals the total length of railroad segments passing through urban 

areas multiplied by 4.41 crossings per mile (2.74 per km), a typical value for an urban freight corridor 

[ADL, 1999]. 

Table 7. Values for Occupants at Grade Crossing Dose Calculation 

Weighted Average Speed 

–Urban 

mph 

 (km/hr) 

Max Individual Dose at 

49 ft (15 m) 

mrem 

(rem) 

Total Dose to Vehicle 

Occupants at Grade 

Crossings (person-rem) 

Route 

35 mph 

(56.3 km/hr) 

50 mph 

(80.4 km/hr) 

35 mph 

(56.3 km/hr) 

50 mph 

(80.4 km/hr)

Urban Route 

Length 

miles (km) 

Crossings per 

Mile (per km) 

Vehicles per 

Crossing 

Occupants per 

Vehicle* 

35 mph 

(56.3 km/hr)

50 mph 

(80.4 km/hr)

1 

29.28 

(47.12) 

34.84 

 (56.07) 

4.74×10-04

(4.74×10-07) 

3.98×10-04

(3.98×10-07)

59.84 

(96.31) 

4.41 

(2.74)

10 1.63 2.04×10-03 1.71×10-03

2 

29.08 

 (46.80) 

33.42 

 (53.78) 

4.85×10-04

(4.85×10-07) 

4.21×10-04

(4.21×10-07)

18.94 

(30.48) 

4.41 

(2.74)

10 1.63 6.60×10-04 5.73×10-04

3 

30.00 

 (48.28) 

35.96 

 (57.87) 

4.64×10-04

(4.64×10-07) 

3.91×10-04

(3.91×10-07)

7.82 

(12.58) 

4.41 

(2.74)

10 1.63 2.61×10-04 2.20×10-04

4 

30.00 

 (48.28) 

35.00 

 (56.33) 

4.64×10-04

(4.64×10-07) 

3.98×10-04

(3.98×10-07)

4.03 

(6.48) 

4.41 

(2.74)

10 1.63 1.34×10-04 1.15×10-04

5 

29.48 

 (47.45) 

34.63 

 (55.73) 

4.74×10-04

(4.74×10-07) 

4.05×10-04

(4.05×10-07)

59.91 

(96.42) 

4.41 

(2.74)

10 1.63 2.04×10-03 1.74×10-03

6 

21.05 

 (33.88) 

22.22 

 (35.76) 

6.75×10-04

(6.75×10-07) 

6.37×10-04

(6.37×10-07)

1.86 

(3.00) 

4.41 

(2.74)

10 1.63 9.06×10-05 8.55×10-05

Note: Doses for individuals are expressed in units of mrem (1 mrem = 1/1,000 rem). Population doses (sum of the 

individual doses) are expressed in units of person-rem. 

*2001 National Household Travel Survey (NHTS)–all trips. 

Train Crew. Train crews are estimated at two per train for the dedicated, regular, and key trains. 

Shipment Escorts. Four escorts per train are assumed for dedicated, regular, and key trains. 

Inspectors/Classification Yard Workers. Railroad employees that classify or inspect the rail casks cars 

during stops are likely to receive close proximity exposures. Functions performed at stops include 

marshalling of cars, arrival and departure train inspections, and repair of damaged railcars. A 

determination of exact numbers of close-in rail yard workers was not established. Instead, doses for this 

39
population were estimated based on the total person-hour/meter estimate used by RADTRAN [DOE, 

1986]. 

Other Rail Yard Workers. An average of 125 workers within a 0.2-mi2

 (0.5-km2) area at each yard is 

assumed based on estimates provided by consulted railroads. This gives a yard worker population density 

of 625 workers per mi2

 (250 workers per km2). 

2.1.5 Distances from the Source 

The distance from the source is a determining factor in the amount of radiation dose members of a 

population group receive. Distance is important because the radiation level varies with the inverse square 

of the distance from the cask. 

The various impacted populations are at different distances from the source. Figure 9 the distances 

assumed in this analysis. The figure also shows the model used (line source or point source) for each of 

the impacted populations. 

Train Crew. Train crew distances from the cask vary depending on the shipment service selected. The 

cask car(s) was assumed to be buffered front and rear. A 49.2 ft (15-m) car length and 6.6 ft (2 m) 

between cars was assumed. For regular and key train service, it was assumed that the cask car was car 

number 35 in a 70 car train. For dedicated service, it was assumed that the train consisted of two 

locomotives (with crew in first unit), buffer car, cask car, buffer car, and escort car (see Figure 7). Crew 

distances were thus 2,140 ft (652.3 m) and 300 ft (91.3 m) for regular/key and dedicated service, 

respectively. 

 

Stops In-Transit

Train Crew 

300 ft (91.3 meters) - Dedicated

2,140 ft (652.3 meters) - Regular/Key

Point Source

Escorts 

96 ft (29.29 meters)

Point Source

Wayside Population 

98.4-2,624.7 ft (30-800 meters)

Point Source

Train Passengers 

14 ft (4.3 meters)

Point Source

 Vehicle Occupants at 

 Grade Crossings 

49.2 ft (15 meters)

Point Source

Train Crew 

300 ft (91.3 meters) - Dedicated

2,140 ft (652.3 meters) - Regular/Key

Point Source

Escorts 

96 ft (29.3 meters)

Point Source

Wayside Population 

1,312.3-2,624.7 ft (400-800 meters) - Yard Entries

98.4-2,624.7 ft (30-800 meters) - Other Stops

Point Source

Classification Yard 

Workers, Repairmen and 

0-32.8 ft (0-10 meters)

Line Source

Rail Yard Workers 

32.8-1,312.3 ft (10-400 meters)

Point Source

Emergency Responders 

32.8-2,624.7 ft (10-800 meters) Point Source

Figure 9. Population Distance from Source 

Shipment Escorts. For all service cases it was assumed that the escort distance from the cask was 96 ft 

(29.3 m). The cask was assumed to be buffered front and rear, with escorts in a car following the rear 

buffer car. Although the position of the escort railcar could differ for regular and key train service, 

placement used for this analysis results in the most conservative estimate. 

40
Passengers in Passing Trains. The centerline distance between passing trains was assumed to be 14 ft 

(4.26 m) (see Figure 10). No exposure estimations were made for passengers of trains moving in the 

same direction as the train carrying the cask. 

14 ft 

(4.26 m)

Figure 10. Passing Train Distance 

Vehicle Occupants at Grade Crossing. Since vehicle occupants who are 98.4 ft (30 m) from the source 

and beyond are included in the general population off-link dose discussed above, only vehicle occupants 

between 32.8 ft and 98.4 ft (10 m and 30 m) from the source were considered here. For the purposes of 

isolating and analyzing the dose of vehicle occupants closer than the 98.4 ft (30 m), it was assumed that 

on average each occupant was 49.2 ft (15 m) from the source. This is an approximation, since doses to 

persons further than the mean distance would be reduced by the distance squared, and persons closer than 

the 49.2 ft (15 m) would be higher. 

2.1.6 Exposure Time 

Exposure time is a determining factor in the amount of radiation members of a population group receive. 

In determining the total exposure durations of populations, time spent near moving and standing trains is 

considered. Train operational restrictions, such as train speed and run-through operations, impact 

exposure time during stops and when en-route. 

Train Speed. Train speed impacts the duration of exposure while the train is moving. The greater the 

train speed, the lower the in-transit exposure to the general population. Route segments of similar 

characteristics were grouped into categories by population density and speed. Speeds for each category of 

route segment were derived by weighting the individual segment speeds by their distance then averaging 

them. This average distance weighted speed was calculated for the 35 mph and 50 mph cases. If the 

distance weighted average speed exceeded the 35 or 50 mph case, the speed was limited to the case mph 

limit. Table 8 shows the average weighted speeds for the six routes used for this analysis. 

41
Table 8. Distance and Average Weighted Speed by Route 

Route Length 

miles (km) 

Average Weighted Speed over Entire Routemph (km/hr)

Route Total Rural Suburban Urban 35 mph (56.3 km/hr) Case 50 mph (80.4 km/hr) Case 

1 1,090.36 

(1,754.76) 

655.61 

(1,055.10) 

374.90 

(603.35) 

59.84 

(96.31) 

26.27 

(42.28) 

31.30 

(50.22) 

2 2,988.02 

(4,808.76) 

2210.98 

(3,558.23) 

758.10 

(1,220.04) 

18.94 

(30.48) 

29.08 

(46.80) 

34.38 

(55.33) 

3 1,919.56 

(3,089.23) 

1,555.11 

(2,502.71) 

356.63 

(573.94) 

7.82 

(12.58) 

29.86 

(48.06) 

35.46 

(57.07) 

4 2,470.58 

(3,976.02) 

2,023.04 

(3,255.77) 

443.52 

(713.77) 

4.03 

(6.48) 

29.05 

(46.75) 

34.39 

(55.35) 

5 3,085.59 

(4,965.77) 

2,017.06 

(3,246.15) 

1,008.62 

(1,623.21) 

59.91 

(96.42) 

29.05 

(46.75) 

34.64 

(55.75) 

6 1,226.03 

(1,973.11) 

1,046.23 

(1,683.75) 

177.94 

(286.36) 

1.86 

(3.00) 

28.27 

(45.50) 

33.03 

(53.16) 

Run-Through Operations. Time spent in classification yards can more than double transit time, especially 

for shorter shipment distances. Reducing this time significantly reduces the radiological risk for both 

onboard and yard personnel and people in the vicinity of yards or other locations where a car might await 

a connecting train. 

A fixed consist that bypasses classification yards en route cuts transit time. This reduces exposure of 

onboard personnel and populace near yards in which it would have stopped. It also avoids the relatively 

high accident potential of yard operations. 

For Moving Train. Exposure time for moving trains is dependent on the train speed and route length (see 

Table 8). Speeds of 35 mph (56.3 km/hr) and 50 mph (80.4 km/hr) were used for this analysis. For crews 

and escorts, transit time was calculated for each route by multiplying the average speed by the route 

length. 

For vehicle occupants at grade crossings, exposure time is the duration of the SNF shipment pass-by. The 

determining factor of this exposure is the train speed. The train’s speed was set at the distance-weighted 

average speed for all urban links on the route for each service type. 

For Standing Train. Two types of stops were assumed for each route: yard stops (classification, 

switching, and inspection) and non-yard or siding stops (interchange and crew change). Each type has a 

different stop duration. Stop times for regular and dedicated trains differ since handling, inspections, 

routes, crew changes, and many other variables affect the time. Stop durations were estimated based on 

Burlington Northern Santa Fe (BNSF) logistical planning model data, which were used to estimate the 

amount of time a train would likely be stopped along each of the routes. The model results used in this 

analysis are BNSF estimates meant to represent a likely scenario for comparison and may be different for 

operations by other railroads. In general, regular and key trains stop in every yard; dedicated trains stop 

for crew changes (driven by hours-of-service limits) and when entering territory of a different railroad 

and changing locomotives (about every 350 miles (563 km)). Trains also could be stopped for 

inspections (the assumption for this analysis is that these inspections are done at the nearest siding/yard 

stop). Tables 9 and 10 show the estimated number and duration of stops used in this analysis. 

42
Table 9. Number and Duration of Yard Entries 

Regular/Key Trains Dedicated Trains

Route 

Number 

of Yard 

Entries Duration of Yard Stops

Number 

of Yard 

Entries Duration of Yard Stops

Origin–20 Hours Origin–20 Hours 

1 4 Intermediate (2)–17 and 36 Hours

Destination–20 Hours

2 

Destination–20 Hours

Origin–20 Hours Origin–20 Hours 

2 5 Intermediate (3)–5, 17 and 24 Hours

Destination–20 Hours

2 

Destination–20 Hours

Origin–20 Hours Origin–20 Hours 

3 5 Intermediate (3)–12, 17 and 24 Hours

Destination–20 Hours

2 

Destination–20 Hours

Origin–20 Hours Origin–20 Hours 

4 5 Intermediate (3)–5, 17 and 24 Hours

Destination–20 Hours

2 

Destination–20 Hours

Origin–20 Hours Origin–20 Hours 

5 5 Intermediate (3)–12, 17 and 24 Hours

Destination–20 Hours

2 

Destination–20 Hours

Origin–20 Hours Origin–20 Hours 

6 5 Intermediate (3)–12, 12 and 17 Hours

Destination–20 Hours

2 

Destination–20 Hours

Total 29 

Origin–120 Hours

Intermediate–292 Hours 

Destination–120 Hours

12 

Origin–120 Hours 

Destination–120 Hours

Assumes 70-112 cars for regular/key trains; 6 car train length for dedicated train. 

Source: BNSF. 

For the general population, stop time is equal to the duration of the stop event. Crew and escort in-transit 

exposure was calculated as a stop with a duration equal to the total travel time for the trip. Actual stop 

time for the crew is equal to the total travel time, plus 2 hours for each yard stop, excluding origin and 

destination (O-D), plus non-classification stop time. Escort stop time is equal to the total travel time, plus 

the full yard entry times including O-D (it is assumed escorts never leave the shipment), plus nonclassification (interchange, crew change, refueling, inspection) stop times. The number of nonclassification stops for regular and key trains are fewer than for dedicated trains because some crew 

changes are assumed to occur in conjunction with classification stops. 

Table 10. Number of Non-Classification Stops 

(approx. 1 per 350 miles (563 km)) 

Duration = 1 hour per stop 

Route Regular/Key Dedicated

1 1 3 

2 6 9 

3 3 6 

4 4 7 

5 6 9 

6 1 4 

Source: BNSF. 

2.1.7 Shielding Factors 

The amount of shielding between the source and the affected population impacts the received dose rate. 

Table 11 shows the shielding factors used for impacted populations (RADTRAN defaults). 

43
Table 11. Shielding Factor (Attenuation) 

Population 

Receptor 

Shielding 

Factor Construction Type 

Rural 1.0* No shielding 

Suburban 0.87* 

Wood frame construction 45-ft sq (13.7-m sq) 

buildings; 100 ft (30.5 m) between buildings; 6-in 

(15.2-cm) thick walls General Wayside 

Population 

Urban 0.018* 

Concrete block walls 1-ft (30.5-cm) thick; 1 central 

wall/ building. Buildings are contiguous in blocks 

200-ft (61-m) long, 60-ft (18.3-m) wide streets 

Vehicle Occupants at Rail Crossings 1.0 No shielding 

Train Passengers 1.0 No shielding 

Crew 0.5 Reflects gamma radiation attenuation by locomotives 

Escorts 1.0 No shielding 

Inspectors/Handlers 1.0 No shielding 

General Yard Workers 0.1 Reflects gamma radiation attenuation by other 

railcars and structures in the rail yard 

* Source: Madsen, Wilmot, and Taylor, 1986. 

Note: The suburban shielding factor was used for general population for all stops. 

2.2 Incident-Free Results 

The following section presents the radiological consequences of incident-free transportation of HLRW 

and SNF by the regular train, key train, and dedicated train service modes for the 35 mph (56.3 km/hr) 

and 50 mph (80.4 km/hr) speeds. The results are presented by route, service/speed, population type, and 

in-transit versus stops. The intent of the incident-free analysis was to provide a general estimate of the 

differences between the alternate service modes and speeds. Simulations of the alternatives were 

conducted comparing service types for the same sets of routes. The results of these estimates are included 

as an example of the likely differences in exposure because of changes in service characteristics. All 

incident-free radiological impact results are given for a single shipment (i.e., a single movement of a 

single cask). 

In general, these results show that dedicated trains expose populations to a lesser radiological dose than 

regular and key trains at all speeds and that stop time risk dominates total exposure for regular and key 

trains. 

The results are expressed primarily as population doses (person-rem) that are converted into an estimate 

of health effects (i.e., LCFs). 

All incident-free doses calculated in RADTRAN 5 are prompt doses (i.e., doses from short exposures) 

and are expressed in effective dose equivalents (EDEs). Doses for individuals are expressed in units of 

mrem. Population doses (sum of the doses for all individuals in the population group) are expressed in 

units of person-rem. 

2.2.1 Results by Route 

This section details the total dose of all population groups from incident-free transportation operations for 

a single movement over each of the six routes. Looking by route, it is evident that route length and 

percent of distance within heavily populated areas are determining factors. Table 12 and Figure 11 show 

in-transit and stop dose results for all populations. 

44
Table 12. In-Transit and Stop Doses (person-rem) for All Populations 

Route Service/Speed In-Transit Stop Total 

Key 50 mph 0.0303 0.1013 0.1316 

Regular 50 mph 0.0303 0.1013 0.1316 

Regular 35 mph 0.0365 0.1013 0.1378 

Dedicated 50 mph 0.0306 0.0413 0.0720 

Route 1 

Dedicated 35 mph 0.0371 0.0413 0.0784 

Key 50 mph 0.0627 0.1323 0.1949 

Regular 50 mph 0.0627 0.1323 0.1949 

Regular 35 mph 0.0758 0.1323 0.2081 

Dedicated 50 mph 0.0638 0.0543 0.1181 

Route 2 

Dedicated 35 mph 0.0772 0.0543 0.1315 

Key 50 mph 0.0359 0.1169 0.1528 

Regular 50 mph 0.0359 0.1169 0.1528 

Regular 35 mph 0.0442 0.1169 0.1611 

Dedicated 50 mph 0.0366 0.0472 0.0838 

Route 3 

Dedicated 35 mph 0.0451 0.0472 0.0922 

Key 50 mph 0.0478 0.1206 0.1684 

Regular 50 mph 0.0478 0.1206 0.1684 

Regular 35 mph 0.0578 0.1206 0.1784 

Dedicated 50 mph 0.0487 0.0493 0.0980 

Route 4 

Dedicated 35 mph 0.0590 0.0493 0.1083 

Key 50 mph 0.0683 0.1402 0.2094 

Regular 50 mph 0.0683 0.1402 0.2094 

Regular 35 mph 0.0848 0.1402 0.2250 

Dedicated 50 mph 0.0704 0.0554 0.1258 

Route 5 

Dedicated 35 mph 0.0862 0.0554 0.1416 

Key 50 mph 0.0245 0.0978 0.1223 

Regular 50 mph 0.0245 0.0978 0.1223 

Regular 35 mph 0.0294 0.0978 0.1272 

Dedicated 50 mph 0.0250 0.0451 0.0700 

Route 6 

Dedicated 35 mph 0.0300 0.0451 0.0750 

45
0.000

0.050

0.100

0.150

0.200

0.250

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

 mph

Route 1 Route 2 Route 3 Route 4 Route 5 Route 6

Route, Service Type, and Speed

Dose (person-rem)

Stops

In-Transit

0.132

0.132

0.138

0.072

0.078

0.195

0.195

0.208

0.118

0.132

0.153

0.153

0.161

0.084

0.092

0.1680.168

0.178

0.098

0.108

0.2090.209

0.225

0.126

0.122

0.122

0.127

0.070

0.075

0.142

Figure 11. Total Dose–All Populations by Route, Service Type, and Speed 

2.2.2 Population Group Exposure by Route, Service Type, and Speed 

This analysis of exposures resulting from routine (non-accident or incident-free) transportation focuses on 

radiation doses received by each of the population groups discussed in Section 2.1.4. 

Incident-free exposure comes from the radiation dose received while the train is moving along the tracks 

(in-transit) and while it is at rest in yards or sidings (stops). Tables 13 and 14 show the total in-transit and 

stop incident-free doses for all populations. 

This analysis deals with the movement of a single train carrying a single SNF cask. The consequences of 

an extended shipment program would need to consider the cumulative annual doses for potentially 

extended (10- to 30-year) periods. Values for multiple low-level exposures per year can be estimated by 

multiplying the single movement person-rem dose by the anticipated number of movements. 

46
Table 13. In-Transit Dose by Population Type (person-rem) 

Route Service/Speed 

General 

Population 

Vehicle 

Occupants at 

Grade 

Crossings 

Passing Train 

Passengers Crew Escorts Total 

Key 50 mph 0.0087 1.71×10-03 1.49×10-03 9.26 ×10-06 0.0184 0.0303 

Regular 50 mph 0.0087 1.71×10-03 1.49×10-03 9.26 ×10-06 0.0184 0.0303 

Regular 35 mph 0.0109 2.04×10-03 1.80 ×10-03 1.10 ×10-05 0.0218 0.0365 

Dedicated 50 mph 0.0087 1.71×10-03 1.49 ×10-03 3.01×10-04 0.0184 0.0306 

Route 1 

Dedicated 35 mph 0.0109 2.04×10-03 1.80 ×10-03 5.62×10-04 0.0218 0.0371 

Key 50 mph 0.0151 5.73×10-04 1.26 ×10-03 2.31 ×10-05 0.0457 0.0627 

Regular 50 mph 0.0151 5.73×10-04 1.26 ×10-03 2.31 ×10-05 0.0457 0.0627 

Regular 35 mph 0.0188 6.60×10-04 2.21 ×10-03 2.73 ×10-05 0.0541 0.0758 

Dedicated 50 mph 0.0151 5.73×10-04 1.26 ×10-03 1.18 ×10-03 0.0457 0.0638 

Route 2 

Dedicated 35 mph 0.0188 6.60×10-04 2.21 ×10-03 1.39 ×10-03 0.0541 0.0772 

Key 50 mph 0.0064 2.20×10-04 7.47×10-04 1.44 ×10-05 0.0285 0.0359 

Regular 50 mph 0.0064 2.20×10-04 7.47×10-04 1.44 ×10-05 0.0285 0.0359 

Regular 35 mph 0.0086 2.61×10-04 1.41 ×10-03 1.71 ×10-05 0.0339 0.0442 

Dedicated 50 mph 0.0064 2.20×10-04 7.47×10-04 7.33×10-04 0.0285 0.0366 

Route 3 

Dedicated 35 mph 0.0086 2.61×10-04 1.41 ×10-03 8.71×10-04 0.0339 0.0451 

Key 50 mph 0.0088 1.15×10-04 1.04 ×10-03 1.91 ×10-05 0.0378 0.0478 

Regular 50 mph 0.0088 1.15×10-04 1.04 ×10-03 1.91 ×10-05 0.0378 0.0478 

Regular 35 mph 0.0111 1.34×10-04 1.87 ×10-03 2.26 ×10-05 0.0447 0.0578 

Dedicated 50 mph 0.0088 1.15×10-04 1.04 ×10-03 9.73×10-04 0.0378 0.0487 

Route 4 

Dedicated 35 mph 0.0111 1.34×10-04 1.87 ×10-03 1.15 ×10-03 0.0447 0.0590 

Key 50 mph 0.0193 1.74×10-03 1.29 ×10-03 2.36 ×10-05 0.0469 0.0693 

Regular 50 mph 0.0193 1.74×10-03 1.29 ×10-03 2.36 ×10-05 0.0469 0.0693 

Regular 35 mph 0.0246 2.04×10-03 2.25 ×10-03 2.82 ×10-05 0.0559 0.0848 

Dedicated 50 mph 0.0193 1.74×10-03 1.29 ×10-03 1.21 ×10-03 0.0469 0.0704 

Route 5 

Dedicated 35 mph 0.0246 2.04×10-03 2.25 ×10-03 1.44 ×10-03 0.0559 0.0862 

Key 50 mph 0.0043 8.55×10-05 6.44×10-04 9.85 ×10-06 0.0195 0.0245 

Regular 50 mph 0.0043 8.55×10-05 6.44×10-04 9.85 ×10-06 0.0195 0.0245 

Regular 35 mph 0.0055 9.06×10-05 1.00 ×10-03 1.15 ×10-05 0.0228 0.0294 

Dedicated 50 mph 0.0043 8.55×10-05 6.44×10-04 5.03×10-04 0.0195 0.0250 

Route 6 

Dedicated 35 mph 0.0055 9.06×10-05 1.00 ×10-03 5.88×10-04 0.0228 0.0300 

47
Table 14. Stop Dose by Population Type (person-rem) 

Route Service/Speed 

General 

Population 

(Yard Stops) 

General 

Population 

(Interchange 

Stops) 

General 

Yard 

Workers 

Classification 

Yard Workers Crew Escorts Total 

Key 50 mph 0.0179 0.0009 0.0061 0.0269 2.39×10-06 0.0495 0.1013 

Regular 50 mph 0.0179 0.0009 0.0061 0.0269 2.39 ×10-06 0.0495 0.1013 

Regular 35 mph 0.0179 0.0009 0.0061 0.0269 2.39 ×10-06 0.0495 0.1013 

Dedicated 50 mph 0.0077 0.0027 0.0026 0.0056 9.48 ×10-05 0.0226 0.0413 

Route 1 

Dedicated 35 mph 0.0077 0.0027 0.0026 0.0056 9.48 ×10-05 0.0226 0.0413 

Key 50 mph 0.0139 0.0046 0.0056 0.0598 4.25 ×10-06 0.0484 0.1323 

Regular 50 mph 0.0139 0.0046 0.0056 0.0598 4.25 ×10-06 0.0484 0.1323 

Regular 35 mph 0.0139 0.0046 0.0056 0.0598 4.25 ×10-06 0.0484 0.1323 

Dedicated 50 mph 0.0064 0.0069 0.0026 0.0124 1.76 ×10-04 0.0258 0.0543 

Route 2 

Dedicated 35 mph 0.0064 0.0069 0.0026 0.0124 1.76 ×10-04 0.0258 0.0543 

Key 50 mph 0.0155 0.0024 0.0061 0.0425 3.45 ×10-06 0.0505 0.1169 

Regular 50 mph 0.0155 0.0024 0.0061 0.0425 3.45 ×10-06 0.0505 0.1169 

Regular 35 mph 0.0155 0.0024 0.0061 0.0425 3.45 ×10-06 0.0505 0.1169 

Dedicated 50 mph 0.0066 0.0047 0.0026 0.0088 1.35 ×10-04 0.0242 0.0472 

Route 3 

Dedicated 35 mph 0.0066 0.0047 0.0026 0.0088 1.35 ×10-04 0.0242 0.0472 

Key 50 mph 0.0131 0.0029 0.0056 0.0516 3.72 ×10-06 0.0474 0.1206 

Regular 50 mph 0.0131 0.0029 0.0056 0.0516 3.72 ×10-06 0.0474 0.1206 

Regular 35 mph 0.0131 0.0029 0.0056 0.0516 3.72 ×10-06 0.0474 0.1206 

Dedicated 50 mph 0.0061 0.0050 0.0026 0.0107 1.49 ×10-04 0.0247 0.0493 

Route 4 

Dedicated 35 mph 0.0061 0.0050 0.0026 0.0107 1.49 ×10-04 0.0247 0.0493 

Key 50 mph 0.0158 0.0048 0.0061 0.0613 4.25 ×10-06 0.0521 0.1402 

Regular 50 mph 0.0158 0.0048 0.0061 0.0613 4.25 ×10-06 0.0521 0.1402 

Regular 35 mph 0.0158 0.0048 0.0061 0.0613 4.25 ×10-06 0.0521 0.1402 

Dedicated 50 mph 0.0068 0.0072 0.0026 0.0127 1.76 ×10-04 0.0258 0.0554 

Route 5 

Dedicated 35 mph 0.0068 0.0072 0.0026 0.0127 1.76 ×10-04 0.0258 0.0554 

Key 50 mph 0.0175 0.0010 0.0053 0.0308 2.92 ×10-06 0.0432 0.0978 

Regular 50 mph 0.0175 0.0010 0.0053 0.0308 2.92 ×10-06 0.0432 0.0978 

Regular 35 mph 0.0175 0.0010 0.0053 0.0308 2.92 ×10-06 0.0432 0.0978 

Dedicated 50 mph 0.0086 0.0041 0.0026 0.0064 1.08 ×10-04 0.0232 0.0451 

Route 6 

Dedicated 35 mph 0.0086 0.0041 0.0026 0.0064 1.08 ×10-04 0.0232 0.0451 

2.2.3 Results for Individual Populations 

General Wayside Population 

Persons who are located near rail routes could receive very low-level exposures when shipments 

containing HLRW and SNF casks move past. These doses are referred to as in-transit off-link doses. The 

total general population dose for all route/service type/speed combinations evaluated ranged from 0.0170 

to 0.0452 person-rem. In-transit doses are speed dependent (see Figure 12 and Table 15). For both speed 

cases, dedicated train service doses were lower than for regular or key train service. In addition to the intransit dose, general population doses are derived from stops. The total dose for all stops (yard and 

interchange) for regular and key service are higher than for dedicated due to increased number of stops 

and longer stop durations. 

48
0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

0.050

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Route 1 Route 2 Route 3 Route 4 Route 5 Route 6

Route / Service Type / Speed

Dose (person-rem)

General Population In-transit General Population Yard Stops General Population Interchange Stops

Figure 12. General Population Dose 

RADTRAN calculates an individual in-transit dose received by a person standing 98.5 ft (30 m) from a 

train as it passes at 15 mph (24 km/hr). This dose, calculated to represent a maximum dose to a single 

person in the general population, is calculated to be 4.32×10-04 mrem (4.32×10-07 rem). At this rate, a 

single individual would have to be exposed to over 6,000 cask shipments for the individual to receive a 

dose equivalent to the total received during a typical 4-hour jet flight. 

49
Table 15. General Population Dose 

General Population Dose (person-rem) 

Route Service 

General 

Population 

In-Transit 

General 

Population Yard 

Stops 

General 

Population 

Interchange 

Stops Total 

Key 50 mph 0.0087 0.0179 0.0009 0.0275 

Regular 50 mph 0.0087 0.0179 0.0009 0.0275 

Regular 35 mph 0.0109 0.0179 0.0009 0.0297 

Dedicated 50 mph 0.0087 0.0077 0.0027 0.0192 

Route 1 

Dedicated 35 mph 0.0109 0.0077 0.0027 0.0213 

Key 50 mph 0.0151 0.0139 0.0046 0.0335 

Regular 50 mph 0.0151 0.0139 0.0046 0.0335 

Regular 35 mph 0.0188 0.0139 0.0046 0.0372 

Dedicated 50 mph 0.0151 0.0064 0.0069 0.0284 

Route 2 

Dedicated 35 mph 0.0188 0.0064 0.0069 0.0321 

Key 50 mph 0.0064 0.0155 0.0024 0.0242 

Regular 50 mph 0.0064 0.0155 0.0024 0.0242 

Regular 35 mph 0.0086 0.0155 0.0024 0.0265 

Dedicated 50 mph 0.0064 0.0066 0.0047 0.0178 

Route 3 

Dedicated 35 mph 0.0086 0.0066 0.0047 0.0200 

Key 50 mph 0.0088 0.0131 0.0029 0.0247 

Regular 50 mph 0.0088 0.0131 0.0029 0.0247 

Regular 35 mph 0.0111 0.0131 0.0029 0.0270 

Dedicated 50 mph 0.0088 0.0061 0.0050 0.0199 

Route 4 

Dedicated 35 mph 0.0111 0.0061 0.0050 0.0222 

Key 50 mph 0.0193 0.0158 0.0048 0.0399 

Regular 50 mph 0.0193 0.0158 0.0048 0.0399 

Regular 35 mph 0.0246 0.0158 0.0048 0.0452 

Dedicated 50 mph 0.0193 0.0068 0.0072 0.0333 

Route 5 

Dedicated 35 mph 0.0246 0.0068 0.0072 0.0386 

Key 50 mph 0.0043 0.0175 0.0010 0.0228 

Regular 50 mph 0.0043 0.0175 0.0010 0.0228 

Regular 35 mph 0.0055 0.0175 0.0010 0.0240 

Dedicated 50 mph 0.0043 0.0086 0.0041 0.0170 

Route 6 

Dedicated 35 mph 0.0055 0.0086 0.0041 0.0182 

Passing Train Passengers 

Passengers on passing trains receive very low-level in-transit exposures (these are referred to as on-link 

doses). Doses for the total passenger population range from 6.44×10-04 to 2.25×10-03 person-rem per 

shipment. On-link dose levels are speed sensitive and vary by route depending on the amount of train 

traffic (see Figure 13 and Table 16). 

50
0.00104

0.00187

0.00104

0.00187

0.001290.00129

0.00225

0.00129

0.00225

0.00064

0.00064

0.00100

0.00064

0.00100

0.00104

0.00141

0.00075

0.00141

0.00075

0.00075

0.00221

0.00126

0.00221

0.001260.00126

0.00180

0.00149

0.00180

0.00149

0.00149

0.000

0.001

0.001

0.002

0.002

0.003

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Route 1 Route 2 Route 3 Route 4 Route 5 Route 6

Route / Service Type / Speed

Dose (person-rem)

Figure 13. Train Passenger On-Link Dose 

51
Table 16. Train Passenger On-Link Dose 

Route Service 

On-Link Dose 

(person-rem)

Key 50 mph 1.49×10-03

Regular 50 mph 1.49×10-03

Regular 35 mph 1.80×10-03

Dedicated 50 mph 1.49×10-03

Route 1 

Dedicated 35 mph 1.80×10-03

Key 50 mph 1.26×10-03

Regular 50 mph 1.26×10-03

Regular 35 mph 2.21×10-03

Dedicated 50 mph 1.26×10-03

Route 2 

Dedicated 35 mph 2.21×10-03

Key 50 mph 7.47×10-04

Regular 50 mph 7.47×10-04

Regular 35 mph 1.41×10-03

Dedicated 50 mph 7.47×10-04

Route 3 

Dedicated 35 mph 1.41×10-03

Key 50 mph 1.04×10-03

Regular 50 mph 1.04×10-03

Regular 35 mph 1.87×10-03

Dedicated 50 mph 1.04×10-03

Route 4 

Dedicated 35 mph 1.87×10-03

Key 50 mph 1.29×10-03

Regular 50 mph 1.29×10-03

Regular 35 mph 2.25×10-03

Dedicated 50 mph 1.29×10-03

Route 5 

Dedicated 35 mph 2.25×10-03

Key 50 mph 6.44×10-04

Regular 50 mph 6.44×10-04

Regular 35 mph 1.00×10-03

Dedicated 50 mph 6.44×10-04

Route 6 

Dedicated 35 mph 1.00×10-03

Vehicle Occupants at Grade Crossings 

Occupants in automobiles at grade crossings were evaluated in this analysis as a distinct population since 

they would be adjacent to passing trains carrying HLRW and SNF. This analysis considered only urban 

crossings, where the highest traffic volumes are experienced and where off-peak scheduling would be 

unlikely. Since the FRA Highway-Railway Crossing Inventory estimates that an average of greater than 

2,000 vehicles per day traverse each urban public crossing, it was assumed that vehicles would be queued 

at each urban crossing. As discussed in Section 2.1.5, cars within 98.5 ft (30 m) of the track centerline 

were considered. A queue of five 14-foot-long cars on each side of the track was assumed to be the 

maximum possible within the 98.5-ft (30-m) distance. This results in a total of 10 cars per crossing 

considered in estimating the dose to vehicle occupants. The number of crossings per route was estimated 

by multiplying the total urban distance for each route by 4.42 crossings per mi (2.74/km), a typical value 

for urban freight corridors [ADL, 1999]. To calculate the maximum dose at these urban grade crossings 

for each route and for each speed restriction, the train speed used was the distance-weighted average 

speed for all urban links on each route. It was assumed that at any point in time 10 vehicles would be at 

each crossing at the time the cask passes, as well as an average vehicle occupancy of 1.63 persons per 

vehicle. Figure 14 and in Table 17 show the calculated dose results. The dose to vehicle occupants at 

grade crossings is train-speed specific and is not impacted by the type of train service. 

52
0.0000

0.0002

0.0004

0.0006

0.0008

0.0010

0.0012

0.0014

0.0016

0.0018

0.0020

0.0022

123456

Route

Dose (person-rem)

35 mph (56.3 km/hr) 50 mph (80.4 km/hr)

Figure 14. Dose to All Vehicle Occupants at Grade Crossings by Route and WeightedAverage Speed 

Table 17. Total Dose to Vehicle Occupants at Grade Crossings 

(person-rem) 

Route 

35 mph 

(56.3 km/hr) 

50 mph 

(80.4 km/hr) 

1 2.04×10-03 1.71×10-03

2 6.60×10-04 5.73×10-04

3 2.61×10-04 2.20×10-04

4 1.34×10-04 1.15×10-04

5 2.04×10-03 1.74×10-03

6 9.06×10-05 8.55×10-05

Train Crew and Escorts 

For train crews, dedicated train doses are higher than for the regular and key trains (assuming no special 

shielding provisions), primarily because of the closer proximity of the crew to the cask in the dedicated 

train. In-transit results are also speed dependent, with higher train speeds generating lower doses. Train 

crews could receive between a 1.17×10-05 and 1.62×10-03 person-rem dose per shipment (see Table 18). 

For shipment escorts, dedicated train case doses are lower than regular and key train cases for both speed 

scenarios because of the shorter stop durations. Stop doses are higher than the in-transit doses for regular 

and key train cases. Escorts could receive between a 0.108 and 0.041 person-rem dose per shipment (see 

Table 18). 

53
Table 18. In-Transit and Stop Dose to Train Crew and Escorts (person-rem) 

Crew Escorts Route Service 

In-Transit Stops Total In-Transit Stops Total 

Key 50 mph 9.26 ×10-06 2.39 ×10-06 1.17×10-05 0.0184 0.0495 0.0679 

Regular 50 mph 9.26 ×10-06 2.39 ×10-06 1.17×10-05 0.0184 0.0495 0.0679 

Regular 35 mph 1.10 ×10-05 2.39 ×10-06 1.34×10-05 0.0218 0.0495 0.0713 

Dedicated 50 mph 3.01 ×10-04 9.48 ×10-05 3.96×10-04 0.0184 0.0226 0.0410 

Route 1 

Dedicated 35 mph 5.62 ×10-04 9.48 ×10-05 6.57×10-04 0.0218 0.0226 0.0444 

Key 50 mph 2.31 ×10-05 4.25 ×10-06 2.74×10-05 0.0457 0.0484 0.0941 

Regular 50 mph 2.31 ×10-05 4.25 ×10-06 2.74×10-05 0.0457 0.0484 0.0941 

Regular 35 mph 2.73 ×10-05 4.25 ×10-06 3.16×10-05 0.0541 0.0484 0.1025 

Dedicated 50 mph 1.18 ×10-03 1.76 ×10-04 1.36×10-03 0.0457 0.0258 0.0715 

Route 2 

Dedicated 35 mph 1.39 ×10-03 1.76 ×10-04 1.57×10-03 0.0541 0.0258 0.0799 

Key 50 mph 1.44 ×10-05 3.45 ×10-06 1.79×10-05 0.0285 0.0505 0.0790 

Regular 50 mph 1.44 ×10-05 3.45 ×10-06 1.79×10-05 0.0285 0.0505 0.0790 

Regular 35 mph 1.71 ×10-05 3.45 ×10-06 2.06×10-05 0.0339 0.0505 0.0844 

Dedicated 50 mph 7.33 ×10-04 1.35 ×10-04 8.68×10-04 0.0285 0.0242 0.0527 

Route 3 

Dedicated 35 mph 8.71 ×10-04 1.35 ×10-04 1.01×10-03 0.0339 0.0242 0.0581 

Key 50 mph 1.91 ×10-05 3.72 ×10-06 2.28×10-05 0.0378 0.0474 0.0852 

Regular 50 mph 1.91 ×10-05 3.72 ×10-06 2.28×10-05 0.0378 0.0474 0.0852 

Regular 35 mph 2.26 ×10-05 3.72 ×10-06 2.63×10-05 0.0447 0.0474 0.0921 

Dedicated 50 mph 9.73 ×10-04 1.49 ×10-04 1.12×10-03 0.0378 0.0247 0.0625 

Route 4 

Dedicated 35 mph 1.15 ×10-03 1.49 ×10-04 1.30×10-03 0.0447 0.0247 0.0694 

Key 50 mph 2.36 ×10-05 4.25 ×10-06 2.79×10-05 0.0469 0.0521 0.0990 

Regular 50 mph 2.36 ×10-05 4.25 ×10-06 2.79×10-05 0.0469 0.0521 0.0990 

Regular 35 mph 2.82 ×10-05 4.25 ×10-06 3.25×10-05 0.0559 0.0521 0.1080 

Dedicated 50 mph 1.21 ×10-03 1.76 ×10-04 1.39×10-03 0.0469 0.0258 0.0727 

Route 5 

Dedicated 35 mph 1.44 ×10-03 1.76 ×10-04 1.62×10-03 0.0559 0.0258 0.0817 

Key 50 mph 9.85 ×10-06 2.92 ×10-06 1.28×10-05 0.0195 0.0432 0.0627 

Regular 50 mph 9.85 ×10-06 2.92 ×10-06 1.28×10-05 0.0195 0.0432 0.0627 

Regular 35 mph 1.15 ×10-05 2.92 ×10-06 1.44×10-05 0.0228 0.0432 0.0660 

Dedicated 50 mph 5.03 ×10-04 1.08 ×10-04 6.11×10-04 0.0195 0.0232 0.0427 

Route 6 

Dedicated 35 mph 5.88 ×10-04 1.08 ×10-04 6.96×10-04 0.0228 0.0232 0.0460 

Car Inspectors and Close Proximity Yard Workers 

Car inspectors/classification workers could receive stop doses between 0.0056 and 0.0613 person-rem per 

shipment. Since the exposures to this population group are for stops only (no in-transit), results are not 

speed dependent but are driven by the number and duration of stops, which are route-specific. In all 

cases, doses for dedicated trains are less than for regular and key trains (see Figure 15). 

54
0.0000

0.0100

0.0200

0.0300

0.0400

0.0500

0.0600

0.0700

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Route 1 Route 2 Route 3 Route 4 Route 5 Route 6

Service / Speed

Dose (person-rem)

Figure 15. Inspector/Classification Yard Worker Dose 

Rail Yard Workers 

Rail yard workers (other than classification workers) could receive stop doses between 2.62×10-03 and 

6.09×10-03 person-rem per shipment. Since the exposure for this population is for stops only (excludes intransit), results are driven by the number and duration of stops that are route-specific. In all cases, doses 

for the dedicated train cases are less than the regular and key train cases (see Figure 16). 

55
Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Route 1 Route 2 Route 3 Route 4 Route 5 Route 6

Route / Service Type / Speed

Dose (person-rem )

7.00×10-03

6.00×10-03

5.00×10-03

4.00×10-03

3.00×10-03

2.00×10-03

1.00×10-03

0.00×10 +00

Figure 16. General Rail Yard Worker (Non-Classification) Dose 

As reported earlier, the maximum individual dose for a single SNF cask shipment is 4.32×10-04 mrem 

(4.32×10-07 rem). This value is compared to exposures from other sources in Figure 17. 

56
0.0004 1 3 3.6

60

0

10

20

30

40

50

60

70

Near Cask

Movement

24 Hr of

Background

Radiation*

4 Hr Jet Flight** Smoking (two

packs)**

Medical X-ray**

Radiation Dose (mrem)

Source:

* www.ocrwm.doe.gov

** National Council on Radiation Protection (NCRP)

Figure 17. Comparison of Incident-Free Exposure Rate Versus Other Common 

Exposures 

2.2.4 Relationship Between Incident-Free Transportation Dosage and the Resulting Health Impacts 

(LCFs) 

According to NCRP [NCRP, 1993], the average annual natural background exposure in the United States 

is 360 mrem (0.36 rem) per year per person. 

The radiological impacts are first expressed as the total calculated exposure for the effected population. 

The total calculated exposure is then used to estimate the hypothetical health effects, expressed in terms 

of estimated LCFs. The dose-to-risk conversion factors used in this analysis to relate radiation exposures 

to LCFs are based on the recommendations of NCRP [NCRP, 1993]. These conversion factors are 

consistent with those used by NRC [56 CFR 233.63 (CFR 1991a)]. The factor used to convert a radiation 

dose to its effect is 0.0004 LCFs per person-rem for workers and 0.0005 latent cancer fatalities per 

person-rem for individuals among the general population. The latter factor is slightly higher because 

there are individuals in the general public, such as the children and elderly (less than 18 and greater than 

65 years of age), who may be more sensitive to radiation than workers. 

The health effects are determined by multiplying the population dose (person-rem) by the appropriate 

conversion factor. Although conversion factors exist which relate population dose cancer incidence and 

genetic effects, this assessment considered only cancer fatalities. 

57
The numbers of fatalities calculated were for single movements with a single cask per movement. For the 

general population, impacts of multiple cask movements can be estimated by multiplying the single cask 

dose times the number of casks in the movement. 

The number of individuals exposed, the duration of their exposure and the resulting LCF was estimated 

for each service type. The exposure level differs for each service type since many variables, such as train 

speed and stop time, vary between the two (see Table 19 and Figure 18). 

58
Table 19. Incident-Free Transportation LCFs 

Total Dose (person-rem) LCFs 

Route Service/Speed Workers Public Total Worker Public Total 

Key 50 mph 0.1009 0.0307 0.1316 4.04 ×10-05 1.54 ×10-05 5.57 ×10-05

Regular 50 mph 0.1009 0.0307 0.1316 4.04 ×10-05 1.54 ×10-05 5.57 ×10-05

Regular 35 mph 0.1043 0.0335 0.1378 4.17 ×10-05 1.68 ×10-05 5.85 ×10-05

Dedicated 50 mph 0.0496 0.0224 0.0720 1.98 ×10-05 1.12 ×10-05 3.10 ×10-05

Route 1 

Dedicated 35 mph 0.0533 0.0252 0.0784 2.13 ×10-05 1.26 ×10-05 3.39 ×10-05

Key 50 mph 0.1596 0.0354 0.1949 6.38 ×10-05 1.77 ×10-05 8.15 ×10-05

Regular 50 mph 0.1596 0.0354 0.1949 6.38 ×10-05 1.77 ×10-05 8.15 ×10-05

Regular 35 mph 0.1680 0.0401 0.2081 6.72 ×10-05 2.01 ×10-05 8.72 ×10-05

Dedicated 50 mph 0.0879 0.0302 0.1181 3.52 ×10-05 1.51 ×10-05 5.03 ×10-05

Route 2 

Dedicated 35 mph 0.0965 0.0350 0.1315 3.86 ×10-05 1.75 ×10-05 5.61 ×10-05

Key 50 mph 0.1276 0.0252 0.1528 5.10 ×10-05 1.26 ×10-05 6.36 ×10-05

Regular 50 mph 0.1276 0.0252 0.1528 5.10 ×10-05 1.26 ×10-05 6.36 ×10-05

Regular 35 mph 0.1330 0.0281 0.1611 5.32 ×10-05 1.41 ×10-05 6.73 ×10-05

Dedicated 50 mph 0.0650 0.0187 0.0838 2.60 ×10-05 9.36 ×10-06 3.54 ×10-05

Route 3 

Dedicated 35 mph 0.0706 0.0217 0.0922 2.82 ×10-05 1.08 ×10-05 3.91 ×10-05

Key 50 mph 0.1425 0.0259 0.1684 5.70 ×10-05 1.30 ×10-05 7.00 ×10-05

Regular 50 mph 0.1425 0.0259 0.1684 5.70 ×10-05 1.30 ×10-05 7.00 ×10-05

Regular 35 mph 0.1494 0.0290 0.1784 5.98 ×10-05 1.45 ×10-05 7.43 ×10-05

Dedicated 50 mph 0.0770 0.0211 0.0980 3.08 ×10-05 1.05 ×10-05 4.13 ×10-05

Route 4 

Dedicated 35 mph 0.0840 0.0242 0.1083 3.36 ×10-05 1.21 ×10-05 4.57 ×10-05

Key 50 mph 0.1665 0.0430 0.2094 6.66 ×10-05 2.15 ×10-05 8.81 ×10-05

Regular 50 mph 0.1665 0.0430 0.2094 6.66 ×10-05 2.15 ×10-05 8.81 ×10-05

Regular 35 mph 0.1755 0.0495 0.2250 7.02 ×10-05 2.48 ×10-05 9.49 ×10-05

Dedicated 50 mph 0.0894 0.0364 0.1258 3.58 ×10-05 1.82 ×10-05 5.40 ×10-05

Route 5 

Dedicated 35 mph 0.0987 0.0429 0.1416 3.95 ×10-05 2.15 ×10-05 6.09 ×10-05

Key 50 mph 0.0988 0.0235 0.1223 3.95 ×10-05 1.17 ×10-05 5.13 ×10-05

Regular 50 mph 0.0988 0.0235 0.1223 3.95 ×10-05 1.17 ×10-05 5.13 ×10-05

Regular 35 mph 0.1021 0.0251 0.1272 4.08 ×10-05 1.25 ×10-05 5.34 ×10-05

Dedicated 50 mph 0.0523 0.0177 0.0700 2.09 ×10-05 8.85 ×10-06 2.98 ×10-05

Route 6 

Dedicated 35 mph 0.0557 0.0193 0.0750 2.23 ×10-05 9.66 ×10-06 3.19 ×10-05

Note: LCF rates for worker population: 0.0004; for general population: 0.0005 (source: NCRP 1993). 

When applied to an individual, units are lifetime probability of LCFs per rem (or 1,000 mrem) of radiation dose. When applied to a 

population of individuals, units are excess number of cancers per person-rem of radiation dose. 

The difference between the worker risk and the general public risk is attributable to the fact that the general population includes more 

individuals in sensitive age groups (that is, less than 18 years of age and over 65 years of age).

59
0.00000

0.00001

0.00002

0.00003

0.00004

0.00005

0.00006

0.00007

0.00008

0.00009

0.00010

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Key 50 mph

Regular 50 mphRegular 35 mph

Dedicated 50 mphDedicated 35 mph

Route 1 Route 2 Route 3 Route 4 Route 5 Route 6

Route / Service / Speed

LCF's

Latent Cancer Fatalities (LCF's) Worker

Latent Cancer Fatalities (LCF's) Public

Latent Cancer Fatalities (LCF's) Total

Figure 18. Latent Cancer Fatalities by Route, Service Type, and Speed 

The in-transit results presented above relate to the movement of a single train with a single SNF cask. 

The DOE plans for SNF movements to Yucca Mountain may include movements of multiple casks on a 

single train. As an example of the impact multiple casks have on radiation dose, Figure compares the 

total dose to the general public and to rail workers for both a single cask and double cask movement for 

Route 6. The general public dose for a double-cask movement is two times that of a single-cask 

movement. The total rail worker dose, however, does not double due primarily to the more distant 

position of the crew and escorts relative to the second cask. Table 20 shows the resulting LCFs calculated 

from the doses shown in Figure 19. 

60
0.00

0.05

0.10

0.15

0.20

0.25

Single CaskDedicated 50 mph 

 (80.4 km/hr)

Single CaskRegular 50 mph 

 (80.4 km/hr)

Double CaskDedicated 50 mph 

 (80.4 km/hr)

Double CaskRegular 50 mph 

 (80.4 km/hr)

Service Type / Speed

Dose (person-rem)

Sum of Public

Sum of Worker

Figure 19. Comparison of Single- and Double-Cask Shipment Dose–Route 6 

Table 20. Average LCFs– 

Single and Double Cask Movements–Route 6 

Route 6 

Service Type/Speed LCFs 

Worker Public Total 

Dedicated 50 mph (80.4 km/hr) 2.09 ×10-05 8.85 ×10-06 2.98 ×10-05 Single Cask 

Movement Regular/Key 50 mph (80.4 km/hr) 3.95 ×10-05 1.17 ×10-05 5.13 ×10-05

Dedicated 50 mph (80.4 km/hr) 2.92 ×10-05 1.77 ×10-05 4.68 ×10 Double -05

Cask 

Movement Regular/Key 50 mph (80.4 km/hr) 6.05 ×10-05 2.34 ×10-05 8.40 ×10-05

Note: LCF rates for worker population: 0.0004; for general population: 0.0005 (source: NCRP 1993). 

61
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62
3. Accident Risk Analysis 

In the previous chapter, the difference in population exposure to radiation due to transportation of SNF or 

HLRW by dedicated, key, or regular train service was calculated. It was assumed, in that chapter, that no 

accidents occurred during shipment. This chapter examines the possibility of accident-related exposure 

by describing the likelihood of accidents involving trains carrying SNF or HLRW and the typical 

magnitude of radiological consequences for those accidents. The baseline accident probability is 

calculated for unrestricted regular train service and adjusted to reflect the special constraints of key and 

dedicated train service. 

In the previous chapter, complete characterizations of radiological exposure for populations along six 

typical rail shipping routes were calculated. A calculation of aggregate radiological exposure under 

incident-free conditions was necessary to make a comparison between dedicated, key, and regular train 

service in that case, since no specific event, such as an accident, was involved in the shipment. 

In this chapter, aggregate accident-related radiation exposures are not calculated. Instead, aggregate 

accident probabilities (not specific to routes) are calculated, and the typical radiological consequences of 

those accidents are characterized. This is because this chapter addresses the difference in accident 

involvement and severity for the three types of service independent of the route along which the 

transportation will take place. 

For the purposes of this report, accidents have been classified into four categories with respect to severity 

and potential for content release: 

• Category I Delay event–accident well within the HAC modeled by the cask packaging test criteria 

of 10 CFR Part 71; dose rate assumed equivalent to the non-exclusive use transport 

rate of 10 mrem/hr at 3.3 feet (1 m) from the cask surface. Accidents in Category I 

could result in an increased duration of exposure to certain individuals (such as crew 

and nearby population) due to the extended time required to clear the wreck scene and 

resume transport. 

• Category II Serious accident–an accident close to the HAC, which could result in a hundredfold 

increase in radiation levels, but no release of radioactive material occurs. The surface 

dose rate is assumed equal to 1 rem/hr (1,000 mrem/hr) at 3.3 feet (1 m) from the cask 

surface. 

• Category III Major accident–an accident that exceeds the HAC. A greater loss of shielding occurs, 

but no release of radioactive material occurs. The surface dose rate is assumed equal 

to 4.3 rem/hr (4,300 mrem/hr) at 3.3 feet (1 m) from the cask surface. Accidents in 

Category III could expose populations to higher doses of radiation for extended time 

periods. 

• Category IV Severe accident–an accident well in excess of the HAC. A significant loss of shielding 

with the release of some radioactive material occurs. 

The consequences of any of these four types of accidents are determined by two factors: the environment 

in which the accident occurred, including bystander and general population, and the potential for a second 

event, such as a fire, puncture, or fall following the impact that constituted the initial accident. 

The time required to respond to the accident, implying the time spent onsite by emergency responders and 

crew, results in longer duration and possibly higher intensity exposure. 

63
The radiological consequences of Category I, II, and III accidents are examined here. Category IV 

accidents are not described in detail in this report because the consequences of these accidents would not 

vary by type of service. The probability of involvement in such an event is the only variable. 

The potential population radiation exposure due to accidents involving the cask are characterized for 

cases where consequences vary with the type of train service. Differences in the position of the crew with 

respect to the cask, the duration of the response to the accident (such as time needed to re-rail a derailed 

car), and the accident forces that might impact the cask have effects on the total radiation doses that 

people will experience in accidents. The resulting emission rates for an accident of a given severity are 

the same for either service. The duration of the incident and the probability of occurrence are different. 

3.1 Methodology 

The methodology employed in comparing the relative safety of dedicated train service to regular and key 

train service for the transport of SNF and HLRW included the following salient features: 

• Historical accident data are employed for structuring the event trees for each type of service. 

• Regular trains are assumed to operate at allowable track speed with no restrictions with respect to 

consist, content, or passing rules. This report assumes that regular trains are 70 cars in length, 

and the cask consist is positioned in the middle of the train. 

• Dedicated trains are assumed to operate with several restrictions, including a no-passing rule, a 

speed limit of 50 mph (80.4 km/hr), and a limited frequency of visits to classification yards. 

Dedicated trains are assumed to be six cars in length, including up to two locomotives, two buffer 

cars, the cask car, and an escort car. Key train restrictions (per AAR recommendations) suspend 

the no-passing rule but do impose a speed limit of 50 mph (80.4 km/hr) for the train carrying 

spent fuel. No limits on the frequency of visits to classification yards are imposed. 

• Modifications to operational constraints, suggested by AAR in their recommended practice, are 

compared to the effects of the most restrictive operational constraints. 

• Accident consequences are derived from cask emission rate levels, duration of exposure, and 

number of persons exposed. Typical consequences for accidents of given severity are calculated, 

and the probabilities for such are given for each type of service. 

• The cask used in the analysis is a prototype 125-ton (113-metric ton) steel-lead-steel cask being 

considered for certification by NRC. The performance of this cask is specified by several specific 

tests defined by NRC, and the performance is further extrapolated by NRC and SNL analyses. 

The potential radiological risks from accidents are based upon several factors: the design of the cask and 

its ability to withstand various impact forces or fires; the likely level of radiation resulting from these 

impacts or fires; and the effect of that radiation on crews, escorts, emergency response personnel, and the 

general population surrounding an accident site. Figure 20 illustrates the components of the analysis, 

which are described below: 

• NRC Cask Certification Criteria: NRC criteria for cask certification establish the required 

functional strength of the cask. To meet these requirements, specific cask designs have been 

proposed (and built). 

• Kinetic Model of Crush Force Mitigation: Most accidents involve a collision with a piece of 

railroad equipment; the initial impact velocity is therefore mitigated by the equipment first 

impacted. The degree to which accident forces are mitigated are described in this model. 

• Finite Element Model: Cask designs were used by NRC and SNL to create finite element 

models. These models describe likely deformations in casks resulting from impacts. The 

64
resulting force-crush characteristics are employed in this analysis to assess the likely results of 

collisions between the cask and other rail equipment. 

• Equivalent Impact Velocities for Different Surface Hardness: SNL defined an array of impact 

velocities that are the equivalent of NRC’s compliance tests and velocities that would cause cask 

damage for a given surface hardness. The residual speed at which a cask might impact the 

wayside surface after the initial collision, which is mitigated due to equipment (locomotive) 

crush, is compared with the SNL impact velocity. These speeds were employed in the 

construction of the event tree. 

• Accident Scenarios and Damage: Given the information above, scenarios that result in incidents 

that exceed NRC’s drop-test compliance speed of 30 mph (48.2 km/hr) were constructed. 

NRC Cask 

Certification 

Criteria

Cask/Locomotive 

Strength Comparison

Determination of 

Residual Speeds

Equivalent Impact 

Velocities for 

Different Surface 

Hardness

Model Cask 

Strength Accident Scenarios 

and Damage

F (Velocity) 

Accident 

Consequences 

(Any Train Type)

Historical Probabilities 

Accident Scenario

 Dedicated Train and Key Train

Operational and Speed Restrictions

Eliminate Historical Accidents from 

Event Tree If Preventable

Regular Train 

Event Tree

Dedicated Train 

Event Tree

Key Train 

Effects

Reduced Accident Scenarios and Damage 

F (Velocity, Surface Hardness)

Figure 20. Accident Risk Analysis Methodology Flow Diagram 

• Accident Consequences (dedicated, key, and regular trains): Accident consequences, described in 

terms of cask damage and resulting radiation exposure, were divided into four severity categories. 

Total radiation emissions were estimated for Category I, II, and III accidents. 

• Historical Accident Probabilities Accident Scenarios: Given the conditions required to incur 

damage (as described in Accident Consequences), historical accident data were sorted into bins 

based upon the category of the accident severity that were likely to result. 

• Regular Train Event Tree: A regular train event tree was constructed for trains operating without 

operational restrictions. This event tree provides a baseline probability that a regular train would 

be involved in an accident at or above a velocity required to damage the cask. 

65
• Dedicated Train Operational and Speed Restrictions: Analyses of the effect on the historical 

accident probability of train accidents defined on the regular train event tree were conducted to 

estimate how operational and speed restrictions for dedicated trains would have affected those 

probabilities. 

• Modify Baseline Event Tree to Define Dedicated Train Event Tree: Some accidents were 

determined to have been preventable (such as raking collisions) if operational restrictions had 

been imposed. These were therefore removed from the regular train event space for purposes of 

defining the dedicated train event tree. Some accidents were not thought to have been completely 

preventable, but accident severity would have been reduced if speed had been restricted. Those 

accidents could not be removed from the event tree (thereby reducing probability). The 

probability of an accident in the higher speed range was instead reduced, and the lower speed 

range probabilities increased. 

• Evaluation of key train movements (as recommended by AAR) were conducted to compare safety 

effects with dedicated and regular trains. 

3.2 Accident Severity Factors 

3.2.1 NRC Cask Certification Criteria 

Accident scenarios were selected for investigation based primarily on the design specifications and 

compliance tests specified by the NRC. NRC identifies four tests: a drop test, a puncture test, an 

immersion test, and a fire test. Each of these tests results in a minimum design criterion for cask 

performance. Figure 21 illustrates the four cask performance tests required by NRC regulations. NRC is 

responsible for describing the robustness of the cask through design standards and physical testing. These 

design criteria and results of physical tests and simulations have been used to determine the level of 

resilience of the cask to various events. 

Survival, according to NRC regulations, as defined in 10 CFR Part 71, requires that after the test the cask 

(1) not release its contents and (2) the emission rate at 3.3 ft (1 m) from the cask is no more than 1,000 

mrem/hr [NRC, 1980]. 

Source: “An Updated View of Spent Fuel Transportation Risk” a Summary Paper for Public Meetings” Office 

of Nuclear Material Safety and Safeguards, NRC. 

Figure 21. Cask Design Tests 

The ability of a cask design to withstand the structural and thermal requirements of these performance 

tests has been demonstrated by engineering analyses, scale-model, or (in some cases) full-scale testing. 

Manufacturers and NRC are responsible for verifying that the proposed designs will satisfy the 

performance test criteria. A hypothetical 125-ton (113-metric ton) steel-lead-steel cask being considered 

for certification by NRC is assumed for purposes of this study. A description of the design of the cask 

66
appears in Chapter 1. Sections 3.2.2 and 3.2.3 describe the structured and thermal characteristics, 

respectively of the assumed cask in response to various collision scenarios. 

3.2.2 Cask Structural Characteristics in Collision Scenarios 

The cask used in the analysis is a hypothetical 125-ton (113-metric ton) steel-lead-steel cask being 

considered for certification by NRC. The performance of this cask is specified by several specific tests 

defined by NRC, and the performance is further extrapolated by NRC and SNL analyses. SNL defined a 

generic steel-lead-steel rail cask design after conducting a survey of existing and proposed SNF rail 

transport cask designs [NRC, 2000]. 

The actual weight of the generic cask is 225,000 lbs (102,058 kg), and it is constructed using stainless 

steel for the inner and outer shell linings and lead as the gamma shielding layer. There are 24 closure 

bolts, each 1.75 inches (4.5 cm) in diameter. The wall thickness variations are a 1.0-inch (2.54-cm) inner 

shell lining, 4.5 inches (11.4 cm) of lead, and a 2.0-inch (5.08-cm) outer shell lining. The overall outside 

diameter of the cask is 80 inches (203 cm), and the cavity diameter is 65 inches (165 cm). The cask 

length is 200 inches (5.08 m). This particular cask design uses an elastomeric seal material. Figure 22 

shows a schematic of the cask design envisioned. 

Source: NUREG/CR-6672, Vols. 1,2, SAND2000-0234, Figure 4.3 on page 4-4 of Volume 1 

Figure 22. Conceptual Design of a Generic Steel-Lead-Steel Rail Cask 

SNL analyzed a generic rail transport cask without the impact limiters in NUREG/CR-6672, and the 

results from a set of those analyses are used in this report. The results used for this report are for various 

impact orientations into a rigid surface at 30 mph (48.2 km/hr), equivalent to a 30-foot (9.1 m) drop. SNL 

noted that the impact limiters are typically designed to absorb the full energy associated with a regulatory 

drop height and hence an equivalent speed for a SNF cask, including the impact limiter of 42 mph (67.2 

km/hr). To cover the full range of possible impact orientations, the following procedure was used. For 

impact angles between 5 degrees and vertical the end-on analysis results are used; for impact angles 

between 5 degrees and 70 degrees the center of gravity (CG) over the corner results are used; and for 

angles between 70 degrees from vertical to horizontal the side-on impact results are used. The key results 

obtained from the large deformation non-linear finite element analyses are the modes of deformation and 

the force crush characteristics. Figure 23 shows the resulting force crush characteristics, which SNL 

developed in support of NUREG/CR-6672. These graphical results, however, were not presented in 

NUREG/CR-6672; instead they were obtained through a private correspondence with SNL.

67
-5.000E+06

0.000E+00

5.000E+06

1.000E+07

1.500E+07

2.000E+07

2.500E+07

3.000E+07

3.500E+07

4.000E+07

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Crush (feet)

Contact Force (lbs)

End Side Corner

Figure 23. Force Crush Characteristic of Generic Steel-Lead-Steel Rail Transport 

Cask for Three Impact Orientations at 30 mph (48.2 km/hr) into a Rigid Surface 

For the end loading condition into a rigid surface, the peak load experienced by the cask is 38 million lbs 

(170 MN) at 0.24 in (0.61 cm) of deformation. After the initial peak load, the force required to continue 

crushing the cask lowers. Between 0.1 and 0.5 ft (3 and 15.2 cm) of deformation, the average force is 

approximately 8 million lbs (36 MN). The final deformation experienced is 0.6 ft (18.3 cm) of crush. 

Although 0.6 ft (18.3 cm) of deformation might seem significant, it represents an aggregate accumulation 

of small strains over the entire 200-in (5 m) length of the cask. No failure of the cask lining at this level 

of deformation occurs; the cask might experience some bulging near the point of impact. The total 

reduction in length of the cask is approximately 3.6 percent. The SNL study indicated no failure of the 

closure bolts under these conditions; however, the minor damage incurred to the cask could result in a 

small increase in emissions that is still within the allowable regulatory limit of 1,000 mrem/hr at 3.3 ft (1 

m). 

The side loading condition into a rigid surface initially exhibits a less stiff response with the initial peak 

load just over 11 million lbs (50 MN), then a stepped force plateau region between 0.1 and 0.22 ft (3 and 

6.7 cm) of crush at approximately 11 million lbs (50 MN), and between 0.22 and 0.5 ft (6.7 and 15.2 cm) 

of crush at approximately 13.5 million lbs (60 MN). Again no failure of the cask occurs. The cask does 

experience permanent deformations with a number of plastic ripples forming; the reduction in the cask’s 

height in the sidewise position is approximately 7.5 percent. Similar to the end loading condition, the 

SNL study indicated no failure of the closure bolts under these conditions; however, the minor damage 

incurred to the cask could result in a small increase in emissions that is still within the allowable 

regulatory limit of 1,000 mrem/hr at 3.3 ft (1 m). 

The least stiff orientation is that for the corner impact loading condition into a rigid surface. A much 

lower initial slope exists between the point of contact and the first initial peak load of 12 million lbs (53 

MN). The force plateaus at approximately 12 million lbs (53 MN) between approximately 0.55 and 0.8 ft 

(16.8 and 24.4 cm) of deformation with a final crush distance of 0.9 ft (27.4 cm). The deformation of the 

cask in this loading condition is greater than that of the longitudinal loading condition because the cask 

68
impact area is more localized. Even so, the final reduction in length on one side of the cask is 

approximately 5.4 percent, which does not cause a breach to form. Again, the SNL study indicated no 

failure of the closure bolts under these conditions; however, the minor damage incurred to the cask could 

result in a small increase in emissions that is still within the allowable regulatory limit of 1,000 mrem/hr 

at 3.3 ft (1 m). 

In summary, substantial kinetic energy is associated with SNF casks and the rest of the train consist 

during transport. If an accident occurs, SNF casks could be subjected to impacts against a variety of 

objects and in various orientations. For the purpose of this analysis, it is assumed that an SNF cask 

involved in an accident could be subjected to the following two types of collisions: 

1. A primary impact against other freight equipment. 

2. A secondary impact against the surrounding infrastructure or environment. 

Sections 3.2.2.1 and 3.2.2.2 discuss the analyses conducted to determine any potential damage to the cask, 

under various operating conditions, for these two collision scenarios, respectively. 

3.2.2.1 Primary Collisions with Rail Equipment 

Freight locomotives are the stiffest freight or passenger rail equipment that a rail transport SNF cask 

would typically encounter. In general, freight locomotives are constructed with a heavy platform 

underframe. A lighter superstructure is mounted to the underframe, along with the engine and other 

equipment. The underframe is designed to withstand the large buff and draft loads the vehicle is 

subjected to during regular operation, so it is very stiff. The heaviest six-axle locomotives weigh between 

415,000 lbs (1850 kN) and 440,000 lbs (1,960 kN). The force-crush behavior for one of these vehicles is 

highly dependent on the manner in which it is loaded during a collision [FRA, 1995]. 

Figure 24 is a schematic of the key structural elements on a typical road locomotive. The coupler is 

attached to the draft gear support structure. During a head-on collision, these items are loaded before any 

other key structural elements on the locomotive. Above the coupler and striker plate is the anti-climber. 

The purpose of this element is to prevent material from climbing above the underframe where it could 

penetrate the short hood structure. 

Figure 24. Schematic of Front End of Freight Locomotive 

69
The two key structural elements above the underframe that act in concert with the short hood to resist 

penetration of foreign objects into the cab area of the locomotive are the collision posts. Once an object 

has cleared the collision posts and entered into the cab area, a relatively low uniform load level is required 

to clear the deck of the locomotive. 

A number of calculations have been conducted on the crush characteristic of each specific member shown 

in Figure 24, and composite force crush curves were developed. The force crush curve is dependent on 

the load path during crush. Since every event is slightly different, a pair of representative crush paths 

were chosen and used to develop a set of composite force crush curves. The first curve presented in 

Figure 25, Loading A, is associated with the central longitudinal loading of the underframe at the level of 

the neutral axis. The second curve developed, Loading B, accounts for crush of the coupler and draft gear 

support structure, followed by hinge formation in the underframe with subsequent failure of the short 

hood and collision posts with full penetration above the deck. Both curves exhibit an initial high peak 

load followed by softened behavior. The results presented show crush to be between 17 to 80 in (43 to 

200 cm) of longitudinal deformation. To date, no analyses or tests have been conducted that provide 

information on the crush strength for larger crush distances. For the purposes of this report, therefore, the 

force level experienced in the plateau region is extrapolated out at the same level for very large crush 

distances. The uncertainty associated with the shape of the curve does not affect the final qualitative 

comparison of risk because the same curves are applied to both types of consists. 

Figure 25. Force Crush Characteristic for Generic Freight Locomotive 

Figure 23 and Figure 25 depict the force crush characteristics for the generic rail steel-lead-steel transport 

cask (analyzed by SNL in NUREG/CR 6672) and a typical locomotive. The crush characteristics for the 

cask are developed for three loading orientations: end-on, side-wise, and the cask CG over the corner. 

The locomotive force crush characteristics are for head-on type loading conditions either at the level of 

the underframe neutral axis or for a climbing contact condition with initial contact occurring at the striker 

plate. Figure 26 shows a plot of these characteristics. 

70
A one-dimensional collision dynamics model, discussed further in Section 3.2.2.2 and Appendix G, was 

developed to analyze SNF cask deformations resulting from collisions with a generic freight locomotive 

for several different cask orientations. The end-on loading condition for the transport cask is significantly 

stiffer than that of the locomotive in either Loading A or Loading B. For a collision between a rail SNF 

cask and a locomotive in a head-on collision, the locomotive will deform and be unable to generate 

sufficiently high forces to cause significant deformation to the rail SNF cask. 

The side-wise and corner loading conditions for the cask, compared to the loading of the locomotive at 

the underframe level, suggests that some shared crush would exist between the cask and the locomotive. 

For the side-wise loading case, 0.1 ft (3 cm) of cask deformation is predicted; for the corner loading 

condition, 0.45 ft (13.7 cm) of cask deformation is predicted. For the climb loading condition of the 

locomotive, cask deformations on the order of 0.1 ft (3 cm) are predicted only for the cask corner over the 

CG loading case. Based on the results of SNL tests and analyses, none of these loading conditions would 

breach the cask or cause a seal failure. There is the possibility of lead slump, and hence, a loss of 

shielding, which would result in a small increase in emissions still within the regulatory limit of 1,000 

mrem/hr at 3.3 ft (1 m). 

-5000000

0

5000000

10000000

15000000

20000000

25000000

30000000

35000000

40000000

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Crush (ft)

Contact Force (lbs)

Cask End-On

Cask Side-Wise

Cask Corner-over-CG

Locomotive Underframe

Locomotive (Climb)

Figure 26. Comparison of Force Crush Characteristics: Generic Rail SNF Transport Cask 

and Typical Locomotive 

3.2.2.2 Secondary Collisions with Surrounding Infrastructure or Environment 

This section discusses a procedure about how to obtain an estimate of the residual speed that an SNF cask 

is traveling at after a primary collision with a freight locomotive. The residual speed is the metric used to 

compare a collision scenario result to the regulatory drop height requirement to determine whether the 

potential damage to the cask exceeds regulatory limits. Four scenarios are discussed: head-on and rearend collisions between a rail SNF cask and a locomotive, a side impact collision at a rail-rail crossing, and 

a raking collision where the rail SNF cask is overhanging a second track and fouls the oncoming 

locomotive’s rail right-of-way (ROW). 

In the event of a collision between two trains or a train and an object fouling the ROW, kinetic energy is 

consumed in a variety of ways. A significant energy absorption mechanism is plastic deformations of the 

71
striking vehicle and whatever is struck. Momentum is conserved, and some energy is absorbed in the 

speeding up/slowing down of the struck object. Additional energy is absorbed by the compression of 

draft gears along the length of the consist. If cars derail, additional kinetic energy is consumed as the cars 

tear up the track and slide along ballasted surfaces. The amount of kinetic energy that is absorbed is 

extremely dependent on the specifics of the event. 

The approach taken is to account for some energy absorption in the event of a collision between a 

locomotive and a rail SNF cask through the application of a simplified one-dimensional collision 

dynamics model. A collision dynamics model is used to calculate the transfer of momentum of two 

objects striking each other at prescribed speeds, as well as the energy consumed due to plastic 

deformations. The requisite information to exercise the model is a description of the force displacement 

behavior of the cask and of the object that the cask strikes. 

The key assumptions of this approach include the following: 

• The cask is bare (the force limiters have been removed, consistent with analyses conducted by 

SNL in NUREG/CR 6672). 

• The cask has been released from the transport car (hence no additional energy absorption due to 

the rail transport car crush or breaking of the tie-downs) and is traveling at the speed of the SNF 

consist at the time of the accident. 

• The rail SNF cask strikes a generic freight locomotive head-on, is struck side-wise by the freight 

locomotive, or is involved in a raking collision. 

• Two load paths are investigated for the locomotive to ascertain sensitivity of residual speeds or 

cask damage. 

• Depending on the collision scenario, separate force crush responses are used for the rail SNF cask 

(end-wise, side-wise, and corner over the cask CG). 

• Both the cask and the locomotive remain in-line during the complete event (enforces the onedimensional response). 

• The final speed at which the cask is traveling is called the cask residual speed. 

This approach, using these assumptions, provides a reasonable manner to estimate the energy absorption 

and final cask residual speed for the three collision scenarios developed. The scenarios developed are 

then mapped into the cask response in the accident severity and probabilities section of the report. The 

different consist types and operating rules will determine the likelihood of the scenario. The behavior of 

the cask in the scenario analyzed is independent of the type of consist involved in the accident. 

The following steps were used to develop the required input for the collision dynamics model: 

• Estimate force crush characteristic of a generic rail SNF cask in the appropriate orientation. 

• Estimate force crush characteristic of a generic freight locomotive. 

• Develop a one-dimensional collision dynamics model. 

• Define initial collision scenarios of concern. 

The previous sections described the force crush characteristics for both the generic rail steel-lead-steel rail 

SNF cask and a typical locomotive. A one-dimensional collision dynamics model is used to calculate the 

exchange of linear momentum and the absorption of energy due to plastic deformations occurring in 

either the rail SNF cask or the generic freight locomotive. This is a lumped mass modeling approach 

72
where the non-linear spring characteristics are the force crush characteristics developed for either the rail 

SNF cask or the locomotive. Figure 27 shows a schematic of the one-dimensional lumped mass system. 

The system equations of motion are developed and solved in a MathCAD worksheet using the RungeKutta differential equation solver. Using the information obtained in the previous sections along with the 

model developed, a series of collision conditions are modeled and scenarios of concern are reported (see 

Appendix G for a more detailed discussion of these analyses). 

Cask Loco 

x1 x3 x2

Cask Locomotive

x1 x3 x2

Figure 27. Collision Dynamics Model 

Head-On Collisions 

The first category of collision scenarios analyzed using a collision dynamics lumped parameter approach 

was that of a head-on collision. In any real head-on collision, most of the energy absorbed would be in 

the crushing of the leading locomotive. It is assumed that the rail SNF cask becomes free due to breakage 

of the tie-down straps or the car derailing. As a worst-case scenario, the cask is free to strike a 

locomotive. In this scenario, the rail SNF cask travels at 50 mph (80.4 km/hr), the original speed of the 

SNF consist, and then strikes a freight locomotive traveling in the opposite direction (see Figure 28). The 

analysis investigates this scenario for different locomotive speeds between 30 mph and 70 mph (48.2 and 

112.6 km/hr) to bound a range of typical track speeds. Although cask speeds of 50 mph (80.4 km/hr) 

were investigated in the current analyses, the 30 mph (48.2 km/hr) force deflection diagrams were used. 

Use of the 30 mph (48.2 km/hr) diagrams was assumed reasonable because they provided a more 

conservative result (i.e., the 30 mph (48.2 km/hr) diagrams predict failure of the cask at slightly lower 

impact speeds than the 50 mph (80.4 km/hr) diagrams). 

Figure 28. Schematic of Head-On Collision Scenario Between SNF Cask and Freight 

Locomotive 

The force crush characteristics used for the cask are those determined by SNL for an end-on impact into a 

rigid barrier at 30 mph (48.2 km/hr). Both force crush characteristics presented earlier for the locomotive 

were used to test the sensitivity of the final residual speed to changes in the locomotive force crush 

73
characteristics. Table 21 presents the scenarios investigated. The first two columns in the table show the 

initial speeds at which the cask and locomotives are traveling. The second two columns are the calculated 

residual speed that the cask is moving at after the primary collision with the locomotive. These results 

show that the cask shears completely through the locomotive and continues to travel at the residual speed 

indicated for all scenarios except the first one (locomotive speed 30 mph (48.2 km/hr), Loading A), where 

it becomes embedded in the locomotive. This residual speed is the speed that the rail SNF cask can strike 

the surrounding rail environment, as is compared against the regulatory impact speed, 30 mph (48.2 

km/hr). These results indicate that the predicted energy absorbed during the primary collision will slow 

the cask sufficiently so that a secondary collision could not result in damage to the cask that results in 

emissions that exceeds the regulatory limit of 1,000 mrem/hr at 3.3 ft (1 m). 

Table 21. Residual Speeds for Various Simplified Head-On Collision Scenarios 

Initial Cask Speed 

mph (km/hr) 

Initial Locomotive Speed 

(in opposite direction) 

mph (km/hr) 

Loading A: Force Crush 

Cask Residual Speed 

mph (km/hr) 

Loading B: Force Crush 

Cask Residual Speed 

mph (km/hr) 

50 (80.4) 30 (48.2) 0 (0) 3 (4.8) 

50 (80.4) 40 (64.4) 6 (9.7) 12 (19.3) 

50 (80.4) 50 (80.4) 12 (19.3) 20 (32.3) 

50 (80.4) 60 (96.4) 19 (30.6) 25 (40.2) 

50 (80.4) 70 (122.6) 23 (37) 28 (45.1) 

If the amount of energy actually consumed during the collision is less than predicted because the cask is 

ejected from the consist, the residual speed could be greater than that quoted in the table, but it would still 

be less than the initial cask speed. 

Rear-End Collisions 

The same analysis procedure used for head-on collisions can be used for rear-end collisions, but, in 

general, the rear-end collision scenario is more benign when the two consists are moving in the same 

direction because the amount of energy to be dissipated is related to the closing speed at impact. For the 

case where the cask is not moving and is struck by the locomotive from behind, however, the loading is 

similar to that of the rail-rail crossing collision described in the next section. As will be discussed below, 

scenarios exist where the residual speed could lead to possible secondary impacts that are in excess of 30 

mph (48.2 km/hr) with resulting damage to the cask that potentially exceeds regulatory limits. These 

scenarios include rear impacts by the locomotive with the cask at speeds in excess of 50 mph (80.4 

km/hr). For these cases, the cask becomes embedded in the locomotive, and they travel down the track at 

the same residual speed.

Rail-Rail Crossing Collisions 

The second collision scenario occurs at rail-rail 90o

 crossings where the locomotive is traveling at some 

speed and impacts the side of the rail SNF cask sitting at the crossing (see Figure 29). The rail transport 

cask’s initial speed is zero, and the locomotive is traveling at a variety of track speeds. In this case, the 

cask is accelerated from rest as the locomotive is crushed and slows down. The force crush curve used to 

describe the rail transport cask is the side-wise impact into a rigid surface at 30 mph (48.2 km/hr), 

developed by SNL in NUREG/CR 6672. Both force crush characteristics presented earlier for the 

locomotive were used to test the sensitivity of the final residual speed to changes in the locomotive force 

crush characteristics. Table 22 presents the scenarios investigated. 

74
Figure 29. Schematic of the Rail-Rail Crossing Collision Scenario 

The first two columns in the table show the initial speeds at which the cask and locomotives are traveling. 

The second two columns are the calculated residual speed that the cask is moving at after the primary 

collision with the locomotive. This residual speed is the speed that the rail SNF cask can strike the 

surrounding rail environment, which is compared against the regulatory impact speed, 30 mph (48.2 

km/hr). The slight differences in the residual speeds predicted for the two different force crush curves 

result from the differences in total energy consumed during crush of the locomotive as momentum is 

exchanged. A number of scenarios are presented in the shaded cells of Table 22, which are of concern in 

terms of possible secondary impacts of the cask with the surrounding rail environment at speeds greater 

than 30 mph (48.2 km/hr) with resulting damage that potentially exceeds regulatory emissions limits of 

1,000 mrem/hr at 3.3 ft (1 m). For all scenarios analyzed, the cask becomes embedded in the locomotive. 

Only one locomotive is included in this analysis. If a train backed up the impacting locomotive, the 

residual speeds for the rail SNF cask would be even higher. 

Table 22. Residual Speeds for Various Simplified Rail-Rail Crossing Collision Scenarios 

Initial Cask Speed 

mph (km/hr) 

Initial Locomotive Speed 

mph (km/hr) 

Loading A: Force Crush 

Cask Residual Speed 

mph (km/hr) 

Loading B: Force Crush 

Cask Residual Speed 

mph (km/hr) 

0 (0) 40 (64.4) 26 (41.8) 26 (41.8) 

0 (0) 50 (80.4) 33 (53.1) 32 (51.5) 

0 (0) 60 (96.4) 39 (62.8) 38 (61.2) 

0 (0) 70 (122.6) 44 (70.8) 46 (74) 

Raking/Corner Impacts 

The final impact scenario studied was that of an overhanging rail SNF cask traveling at 50 mph (80.4 

km/hr) that was struck on the corner by a passing locomotive going in the opposite direction at a variety 

of speeds (see Figure 30). The force crush characteristic used for the rail transport cask is that associated 

with a corner impact into a rigid surface at 30 mph (48.2 km/hr) generated by SNL and presented in 

Figure 26. Both force crush characteristics presented earlier for the locomotive were used to test the 

sensitivity of the final residual speed to changes in locomotive force crush characteristics. 

75
Freight car

Locomotive

Figure 30. Schematic of Raking Collision Scenario 

Table 23 presents the scenarios investigated. The first two columns in the table show the initial speeds at 

which the cask and locomotives are traveling. The second two columns are the calculated residual speed 

that the cask is moving at after the primary collision with the locomotive. This is the speed at which it 

can now strike the surrounding rail environment, which is compared against the regulatory impact speed, 

30 mph (48.2 km/hr). If the amount of energy absorbed in this simple scenario occurs for an actual 

accident, it will not be more severe than a Category II. For raking or cornering collisions where the 

amount of energy consumed in plastic deformations is less than that calculated, the final cask residual 

speeds will be higher than those presented. 

Table 23. Residual Speeds for Various Simplified Raking/Corner Collision Scenarios 

Initial Cask Speed 

mph (km/hr) 

Initial Locomotive Speed 

mph (km/hr) 

Loading A: Force Crush 

Cask Residual Speed 

mph (km/hr) 

Loading B: Force Crush 

Cask Residual Speed 

mph (km/hr) 

50 (80.4) 30 (48.2) 0 (0) 1 (1.6) 

50 (80.4) 40 (64.4) 6 (9.7) 12 (19.3) 

50 (80.4) 50 (80.4) 8 (12.9) 20 (32.3) 

50 (80.4) 60 (96.4) 16 (25.7) 25 (40.2) 

50 (80.4) 70 (122.6) 20 (32.3) 28 (45.1) 

3.2.2.3 Equivalent Impact Velocities for Different Surface Hardness 

Impact velocity and surface hardness are critical determinants of the resulting damage from any accident 

involving the spent fuel cask. The effect of a 30-ft (9.1 m) drop onto an unyielding surface is not the 

equivalent of the same drop onto yielding (soft) surfaces. Table 24 provides an example of this type of 

trade off for the generic steel-lead-steel rail cask analyzed by SNL in NUREG/CR 6672. It also illustrates 

that the translation from impact velocity and surface hardness to damage is not linear; damage depends 

upon the orientation of the impact and the type of surface that the cask hits. The equivalent impact 

velocities shown in Table 24 assume that the impact limiter normally attached to the cask during transport 

is not on the cask at the time of impact. For the purposes of this study, only the values reported for a 30-

mph (48.2-km/hr) impact speed into a rigid surface are used. The 60, 90, and 120 mph (96.4, 144, and 

192 km/hr) speeds (shaded columns) are not used as they represent cases that exceed the regulatory 

compliance limits. When reviewing Table 24, results in the shaded columns for yielding surfaces while 

based on results in the 30 mph (48.2 km/hr) column, necessitated using a slightly different set of 

assumptions regarding the properties of the yielding surfaces. [NRC, 2000]. 

76
Table 24. Impact Speeds onto Real Yielding Surfaces–Type B Steel-Lead-Steel Spent Fuel Rail Cask 

Impact Speed (mph) Impact Surface Impact 

Orientation 30 60 90 120 

End 30 60 90 120 

Hard Rock Corner 30 60 90 120 

Side 30 60 90 120 

End 38 319 391 509 

Corner 35 640 990 >990 

Soft Rock/Hard 

Soil/Concrete Slab 

(abutment) Side 32 207 289 >289 

End 84 >386 >480 >635 

Clay/Silt Corner 58 >133 >208 >223 

Side 32 >180 >256 >262 

End 38 386 480 635 

Railbed/Roadbed Corner 35 133 208 >223 

Side 32 180 256 >262 

End 78 ∞ ∞ ∞

Water Corner 150 ∞ ∞ ∞

Side 42 ∞ ∞ ∞

Source: Table 7.23 Impact Speeds (mph) onto Real Yielding Surfaces that are Equivalent to 30-, 60-, 90-, and 120-

mph (48.2-, 96.4-, 144-, and 192-km/hr) Impacts onto an Unyielding Surface. Type B Steel-Lead-Steel Spent Fuel 

Rail Cask (p 7-59), [NRC, 2000]. 

3.2.2.4 Summary of Cask Structural Characteristics 

The analyses in this section led to the identification of potential final impact velocities for several 

simplified generic collision scenarios using force crush characteristics for a generic steel-lead-steel rail 

SNF cask and for two different locomotive crush paths. The results indicate that the residual speeds for 

head-on and raking collisions for the scenarios studied are less than 30 mph (48.2 km/hr) and will not 

result in accidents more severe than Category II. For the rail-rail crossing scenario, however, possible 

speed combinations are predicted to allow a secondary impact velocity greater than the regulatory allowed 

speed of 30 mph (48.2 km/hr), resulting in a Category III accident. Any collision where the locomotive 

strikes the rail SNF cask from the side at a speed in excess of 50 mph (80.4 km/hr) will result in residual 

speeds greater than 30 mph (48.2 km/hr) and damage to the cask that potentially results in a Category III 

accident. In no event is a Category IV accident expected, provided the striking locomotive initial speed is 

less than 70 mph (112.6 km/hr). This is based upon the results presented in NUREG/CR 6672; results of 

this study indicate that the highest residual speeds calculated are between 44 and 46 mph (70.8 and 74 

km/hr). 

Several caveats exist: 

• For all the scenarios studied, it is possible that either a greater or lesser amount of energy will 

actually be consumed during a collision depending on very event-specific variables. 

• The actual bounds of possible secondary impact speeds that a cask may experience lie between 

zero and the initial speed of the cask or locomotive. 

Using the force crush characteristics presented, a generic steel-lead-steel rail transport cask is sufficiently 

stiff such that direct collisions with a locomotive, for the speeds investigated, will not result in Category 

III accidents. The analyses presented by SNL in NUREG/CR 6672 also show that the bare cask will 

survive even higher impact speeds into a rigid planar surface without causing a breach or seal failure. 

Additional energy consumption mechanisms exist if the force limiters remain attached during the 

collision, as they are designed to absorb the complete energy from a 30-ft drop (9.1-m). 

77
3.2.3 Cask Thermal Characteristics in Collision Scenarios 

The 1987 Modal Study [NRC, 1987a],26 conducted for NRC by Lawrence Livermore National 

Laboratory, established baseline parameters for estimating risk of cask failure under varying 

transportation accident scenarios. Response to severe thermal loads was identified as an important 

component of such an estimate. It has been recognized in research [NRC, 2000] and certification 

standards for hypothetical accident conditions (in Subpart F, 10 CFR Section 71.73) that cask immersion 

in fires of over 1,475° F (800° C) for times in excess of the NRC compliance test parameters can melt 

lead shielding, thermally degrade and fail elastomeric seals, and burst-rupture spent fuel rods–resulting in 

elevated source emission levels, secondary vapor leaks, and dangerous releases of dispersing radioactive 

materials. 

The Modal Study focused on modeling the physical cask response to thermal loads, to evaluate impacts 

on cask structural integrity in various fires. It did not go so far as to predict associated radioactive levels 

and releases. In its most recent analysis NUREG CR-6672 [NRC, 2000], SNL established that lead slump 

(occurring due to impacts or melting of lead used as an interior cask layer) could significantly reduce the 

shielding provided by the cask and result in elevated surface emission levels. SNL’s analytical discussion 

concluded that at 662° F (350° C) the elastomeric seals of the steel-lead-steel rail cask would begin to 

fail.27 SNL calculated that it would take 1.06 hours for this temperature to be reached in an optically 

dense, fully engulfing fire at 1,475° F (800° C) [NRC, 2000].28 SNL further assumed that at 1,382° F 

(750° C) the spent fuel rods could fail by burst rupture. The time required for this event in the same type 

of fire was calculated to be 2.91 hours [NRC, 2000]. 

3.3 Accident Severity and Probabilities 

3.3.1 Accidents of Interest 

Train accident scenarios were analyzed to identify the possible scenarios involving a spent fuel cask that 

could result in an impact, a fire, or both. These accident scenarios were assigned probabilities based upon 

whether the accident would happen at impact velocities that could exceed an equivalent compliance test 

impact velocity for a hard surface. The probability of each of the accident scenarios was estimated for a 

regular train with no operational restrictions. Once a complete accident event tree was calculated, 

accidents that would be reduced or eliminated due to speed restrictions, train consist limits, or other 

operational restrictions (such as a no-passing rule or reduction of yard entries) were also reduced or 

eliminated from the event tree. 

 

26 NRC is currently revisiting part of this study and is presently in Phase 2 of a four-phase study known as the Package 

Performance Study (PPS). 27 “7.2.5.2 Thermal Failure of Cask Seals and Spent Fuel Rods. During normal transport under ambient conditions, the peak 

temperature of spent fuel in a Type B spent fuel cask is about 572° F (300°C) [7-22]. Because the average temperature of 

free burning hydrocarbon fuel fires is about 1,832° F (1,000° C) [7-23], elastomeric cask seals and spent fuel rods can both 

fail if the cask that contains them is heated long enough by a hot fire. ...Nevertheless, it is here assumed that elastomeric cask 

seals begin to leak when heated to 662° F (350° C).” When heated to elevated temperatures, spent fuel rods fail by burst 

rupture. During the experiments of Lorenz, et al. [7-26], sections of spent fuel rods that had been heated to 1,652° F (900° C) 

failed by burst rupture when rod pressures reached 275 psig.” 28 Ibid., Chapter 6, pp 6-7. 

78
3.3.2 Historical Accident Probabilities 

The likelihood of accidents during future spent fuel shipments in the United States can be estimated based 

upon the past experiences in shipments of many types of goods. Some peculiarities about the shipment of 

spent fuel, most especially shipments of large casks (the 125-ton (113-metric ton) MPC), may increase 

additional accident probability. 

Accident probabilities were based upon 14 years of accident data from the Railroad Accident/Incident 

Reporting System (RAIRS) database, from 1988 to 2001 (see Table 25). This extended time period 

provides an ample basis to assess accident probabilities and account for any short-term fluctuations in 

accident rates. Normalized accident rates were calculated by dividing total accidents by reported train 

miles for each year using the data that appear in Table 26. 

3.3.3 Accident Speed Evaluations 

Each accident type has been examined to identify the potential hazard to the cask in the event of that 

accident. Casks may be damaged due to impacts with surrounding surfaces (the ground, railbed), or other 

rail equipment (car-couplers, pieces of rail equipment), or cars themselves, such as in collisions with 

locomotives. In each scenario, the potential harm to the cask is the crucial element in defining the event 

tree. Potential impact velocities with the cask and whatever it encounters is, at its maximum, defined in 

terms of the speed of the train carrying the cask. In some accident scenarios, however, the cask velocity 

may be reduced by intermediate, but non-damaging, collisions with rail equipment before encountering a 

potentially damaging final collision. The initial velocity for each of the accident types, defined in Table 

27 is used to estimate the final cask impact velocity for that scenario. Estimated damage, given these 

initial velocities, is defined only in terms of whether the final impact velocity is less than, equal to or 

greater than NRC’s compliance value. Table 27 describes the definitions of these accident types and the 

method of selecting the initial impact velocity of concern. 

Table 25. Reported Train Accidents 1988-2001 

Total Main and Yard Main Only Yard Only RAIRS Accidents 

1988-2001 Accident 

Count Probability Accident 

Count Probability Accident 

Count Probability 

Derailment 23,219 0.6634 10,672 0.6681 12,547 0.6594 

Head-On Collision 246 0.007 149 0.0093 97 0.0051 

Rear-End Collision 312 0.0089 237 0.0148 75 0.0039 

Side Collision 1,889 0.054 219 0.0137 1,670 0.0878 

Raking Collision 510 0.0146 163 0.0102 347 0.0182 

Broken Train Collision 84 0.0024 45 0.0028 39 0.002 

Highway-Rail Crossing* 2,393 0.0684 2,365 0.1481 28 0.0015 

Rail-Rail Crossing 16 0.0005 14 0.0009 2 0.0001 

Obstruction 763 0.0218 605 0.0379 158 0.0083 

Explosive 9 0.0003 2 0.0001 7 0.0004 

Fire/Violent Explosion 337 0.0096 245 0.0153 92 0.0048 

Other Impacts** 4,388 0.1254 880 0.0551 3,508 0.1844 

Other in Narrative 834 0.0238 377 0.0236 457 0.024 

Total 35,000 15,973 19,027 

* RAIRS data contains only a portion of highway-rail crossing accidents. 

** Other: Acts of God, or other events involving the operation of on-track equipment (standing or moving) that result in 

reportable casualty/damages (e.g., humping accidents, switch damage). 

Source: RAIRS. 

79
Table 26. Reported Train Miles 

Year Total Train Miles Mainline Train Miles Yard Train Miles 

1988 609,334,435 504,008,966 105,325,469 

1989 620,598,940 516,268,837 104,330,103 

1990 608,837,284 510,685,897 98,151,387 

1991 576,834,890 488,315,540 88,519,350 

1992 593,703,777 509,274,174 84,429,603 

1993 613,973,971 526,852,215 87,121,756 

1994 655,083,056 565,307,012 89,776,044 

1995 669,823,264 579,931,398 89,891,866 

1996 670,923,960 583,100,706 87,823,254 

1997 676,716,407 591,842,608 84,873,799 

1998 682,894,841 599,202,777 83,692,064 

1999 712,452,725 624,993,727 87,458,998 

2000 722,876,632 633,957,546 88,919,086 

2001 709,758,198 624,198,248 85,559,950 

Total 9,123,812,380 7,857,939,651 1,265,872,729 

Source: RAIRS. 

Table 27. Accident Scenarios and Equivalent Velocities for the NRC Compliance Test 

Accident Type Equivalent Velocity 

For train derailments where the cask car does not derail (assigned an 80 percent probability), it is assumed that the cask may impact 

other rail equipment. The resulting damage from such an impact is assumed not to exceed the regulatory limit of 30 mph (48.2 

km/hr), which corresponds to a Category I/II event. For train derailments where the cask car does derail (assigned a 20 percent 

probability), it is assumed that the cask impacts a hard object in the surrounding environment. Any train speed in excess of 30 mph 

(48.2 km/hr) will result in damage to the cask that exceeds regulatory limits. Refer to Table 24 for velocity equivalents. This 

corresponds to a Category III event. 

Derailment 

Head-On Collision 

For head-on train-to-train collisions, the worst-case assumptions applied are the cask train speed is 50 mph (80.4 km/hr), the cask 

breaks free of its car, and the cask collides head-on with the second train’s locomotive. For speeds of the second locomotive below 70 

mph (112.6 km/hr), Category I/II events can occur. For speeds of the second locomotive above 70 mph (112.6 km/hr), it is assumed 

that the cask impacts a hard object in the environment and damage that exceeds regulatory limits occurs, which corresponds to a

Category III event (see Table 21). 

The worst-case rear-end scenario assumed is that a stationary cask is struck by the second train’s locomotive and derails. After 

impact, the cask and locomotive continue to move at a residual velocity. For striking locomotive speeds under 40 mph (64 km/hr), the 

residual velocities do not exceed 30 mph (48.2 km/hr), which corresponds to a Category I/II. For striking locomotive speeds greater 

than 40 mph (64 km/hr), the cask impacts a hard object in the environment, and damage that exceeds regulatory limits occurs, which 

corresponds to a Category III event (see Table 22). 

Rear-End Collision 

Side Collision 

The side-collision scenario assumes the cask is hit broadside by a train and derails. After impact, the cask and locomotive continue to 

move at a residual velocity. For striking locomotive speeds under 40 mph (64 km/hr), the residual velocities do not exceed 30 mph 

(48.2 km/hr), which corresponds to a Category I/II. For striking locomotive speeds greater than 40 mph (64 km/hr), the cask impacts 

a hard object in the environment, and damage that exceeds regulatory limits occurs, which corresponds to a Category III event (see 

speeds defined in Table 22). 

For raking collisions, it is assumed that the cask is struck on the corner by another piece of rail equipment and derails. For speeds of 

the second locomotive below 70 mph (112.6 km/hr), Category I/II events can occur. For speeds of the second locomotive above 70

mph (112.6 km/hr), it is assumed that the cask impacts a hard object in the environment, and damage that exceeds regulatory limits 

occurs, which corresponds to a Category III event (see Table 23). 

Raking Collision 

Broken Train Collision 

In the broken train collision scenario, a section of a train rolls into the path of a moving train or rolls into another stopped train. The 

speeds of concern are assumed to be the same as in the raking collision. The broken train must be traveling at a speed below 70 mph 

(112.6 km/hr) for a Category I/II event to occur. The broken train must be traveling at a speed above 70 mph (112.6 km/hr) for a 

Category III event to occur (see Table 23). 

Highway-Rail Crossing For a highway-rail crossing scenario, the worst case occurs when the train derails. The derailment logic is then applied. 

Rail-Rail Crossing 

For the rail-rail crossing scenario, the cask is impacted broadside by a locomotive and derails. After impact, the cask and locomotive 

continue to move at a residual velocity. For striking locomotive speeds under 40 mph (64 km/hr), the residual velocities do not 

exceed 30 mph (48.2 km/hr), which corresponds to a Category I/II. For striking locomotive speeds greater than 40 mph (64 km/hr), 

the cask impacts a hard object in the environment, and damage that exceeds regulatory limits occurs, which corresponds to a Category 

III event (see Table 22). 

Obstruction These collisions are assumed to be similar to highway-rail crossing accidents discussed above. 

Explosion/Fire These events are evaluated independently in terms of potential fire hazard. 

80
3.3.4 Baseline Event Trees–Regular Trains 

Based upon nationally available historical train accident data for 1988-2001, three event trees were 

constructed. One representing regular trains involving all manners of movement on the mainline, the 

second representing regular trains in yards, and the third describing fire events. Fires are treated 

independently because they can be initiating events, or a secondary event following one of the other 

accident scenarios. 

An event tree is a useful representation of the likelihood of accidents of various types. This is a summary 

of the distribution of “types” of accidents given their rate of occurrence. The baseline event tree 

represents accidents that have occurred at all speeds on the mainline. The base rate is calculated by 

summing the total reported accidents during the period and normalizing by train miles in both yards and 

on the mainline (see Figure ). This probability is the accident rate per train mile in the U.S. for 1988-

2001. The probability of each of the accident types is based upon the fraction of those accidents that fell 

into one of the accident categories using the Railroad Accident Information Reporting System (RAIRS) 

data for this time period. FRA defines a reportable train accident as: 

Any collision, derailment, fire, explosion, act of God, or other event involving the operation 

of on-track equipment (standing or moving) that results in total damages to all railroads 

involved in the event that is greater than the current reporting threshold to railroad on-track 

equipment, signals, track, track structures, and roadbed. 

Note: The classification of a train accident by type (collision, derailment, other) is determined 

by the first reportable event in the accident sequence. All reports for a single accident are to 

use the same designation. For example, if following a derailment a train strikes a consist on 

an adjacent track, the report for this additional consist will indicate that the accident type was 

a derailment, not a collision [FRA, 2000]. 

Accidents that are reported are determined by a reporting threshold: 

The amount of total reportable damage resulting from a train accident which, if exceeded, 

requires the preparation and forwarding of form FRA F 6180.54 by the railroads involved. 

For accidents occurring in calendar years 1991-1996, the reporting threshold is $6,300. For 

accidents that occur in calendar year 1997, the reporting threshold is $6,500. See 61 Fed. 

Reg. 60632 (Nov. 29, 1996). Pursuant to § 225.19(e), the reporting threshold will be revised 

annually according to the formula set forth in Appendix B to Part 225 [FRA, 2000]. 

Due to the substantial difference in the frequency of accidents in yards versus mainline (nearly 50 percent 

of U.S. mainline accidents), a separate yard event tree was constructed. Figure 32 shows a representation 

of the event tree for yard accidents. The yard event tree is identical in structure to the mainline tree, but 

the probabilities are different due to the different distribution of accident types and speeds in yards. The 

probability of a train accident being either on the mainline or in a yard is distinguished in the event trees. 

The distinction between mainline and yard accidents is made first because of the significant difference in 

the number of yard entries made by a regular versus dedicated train and the resulting significant decrease 

in accident exposure (not accounting for severity) that results from this operational distinction. Given that 

the accident happens in one or the other environment, five further accident type scenario characteristics 

are described, including the probability of a collision; derailment, highway-rail grade crossing accident; 

fire or explosion; or some other type of accident. 

Each event tree begins with the overall train accident rate per train mile, based upon the historical RAIRS 

accident data. These are subdivided into types of accidents (e.g., grade crossings, collisions), and the 

probabilities of those types are reflected in the initial nodes. Some of each of those types of accidents 

81
result in derailments, and the probability of a subsequent derailment following each initiating event is also 

calculated. These derailments pose scenarios in which a secondary impact with another piece of railroad 

equipment, the ground, or an object on the wayside may occur and damage the cask as discussed in 

Section 3.2.2. The frequency of derailments was assessed using the accident report account of the 

number of cars that derailed in the event. The RAIRS report indicates whether any car derailed 

independent of whether the initiating event classified the accident as a derailment. 

Severity of the derailment is a crucial component of this analysis. Since the surface hardness of the final 

surface impacted by the cask is unknown, an approach to estimating the possibility of cask damage or 

release was constructed based upon impact velocity and the distribution of final velocities after secondary 

impacts that could result in cask damage. The probabilities have been categorized into impact velocities 

that would represent exceeding regulatory compliance limits for impacts with hard surfaces. This is a 

very conservative approach. The nodes that describe speed distributions follow the accident type nodes 

on the trees and summarize the probability that the accident will occur at or above the threshold speed that 

is the equivalent of the NRC’s 30-ft (9.1-m) drop compliance test for a hard surface impact. 

Several categories of collisions are grouped into two scenarios, those where the initial impact velocity 

must equal or exceed 70 mph (112.6 km/hr) to result in a 30 mph (48.2 km/hr) (NRC compliance speed 

equivalent) impact and those for which that speed is 50 mph (80.4 km/hr). Head-on, raking, and broken 

train collisions are in the former category, and rear-end and side collisions are in the latter. Rail-highway 

crossing, rail-rail, and obstruction collisions are analyzed separately in the event trees. In all cases 

involving derailments, it is assumed that the probability that the cask car is one of the derailing cars is 0.2. 

This is based upon the analysis of derailment characteristics presented in Section 3.4.2. 

To illustrate use of the mainline event tree in calculating accident probabilities (see Figure 31), an 

example is provided here. The example calculates the probability that obstruction collisions of regular 

trains operating on mainline will result in cask impacts that exceed regulatory compliance limits. In this 

example, the obstruction accident type branch of the tree is of interest. From the event tree, the overall 

mainline regular train accident rate is 2.0327×10-6; the probability of an obstruction collision is 0.03788; 

and the probability of a derailment following an obstruction collision is 0.13223. Furthermore the 

following distribution of train speeds for obstruction derailments is noted: less than 30 mph, 0.64969; 30 

mph to 50 mph (48 km/hr to 80.4 km/hr), 0.28355; 50 mph to 70 mph (80.4 km/hr to 112.6 km/hr), 

0.06614; and greater than 70 mph (112.6 km/hr), 0.00061. Finally, for all train derailments, the cask car 

has a 0.20 probability of actually derailing. As discussed in Section 3.2.2 and in Table 28, it was 

determined that, for obstruction derailments, the critical speed is 30 mph (48 km/hr); that is, obstruction 

derailments with initial train speeds greater than 30 mph (48 km/hr) will result in cask damage that 

exceeds regulatory compliance limits. The train speed probabilities of interest in the event tree will 

therefore be the sum of those above 30 mph (48 km/hr). Given the above, the calculation for the 

probability of obstruction collisions resulting in damage to casks that exceeds regulatory limits is: 

Pr (Obstruction collision > limits) = (2.03272×10-6) × (0.03788) × (0.13223) × (0.28355 + 0.06614 + 

0.00061) × (0.20) = 7.13278×10-10

The calculation of similar probabilities using the yard event tree is performed in the same manner as with 

the mainline tree, except that the 0.20 probability factor for cask car derailment does not apply to yard 

accidents. 

82
1988-2001 Accident Type Outcome Speed Distributions (Main)

Probability (per Train Mile) of 

Cask Imapct > NRC 

Certified Speed Equiv. for (30 

MPH)*

Remain on Track

Highway Grade Crossing 0.83975 Less than 30 mph 0.64969 HWY GRADE XING 3.37916E-09

0.14806 Hwy Grade Crossing Collision Followed by Derail 30 to 50 mph 0.28355

0.16025 50 to 70 mph 0.06614

>70 mph 0.00061

Rail - Rail Crossing Remain on Track

0.00088 0.35714

Rail -Rail Collision Followed by Derailment Less than 30 mph 0.77738 RAIL*RAIL XING 7.87744E-12

0.64286 30 to 50 mph 0.18824

50 to 70 mph 0.03439

>70 mph 0.00000

Remain on Track

0.60224

Head on, Raking, Broken 

Train Collision Collision Followed by Derailment Less than 30 mph 0.66404

Head On Broken Train or 

Raking Collision 2.01459E-12

0.02235 0.39776 30 to 50 mph 0.27552

50 to 70 mph 0.06339

>70 mph 0.00056

Remain on Track

0.46711

Rear end or Side Collision Collision Followed by Derailment

0.02855 0.53289

Less than 30 mph 0.66404 Rear end or Side Collision 3.95478E-10

30 to 50 mph 0.27552

50 to 70 mph 0.06339

>70 mph 0.00056

Obstruction Remain on Track

0.03788 0.86777

Obstruction Collision Followed by Derailment Less than 30 mph 0.64969 OBSTRUCTION 7.13278E-10

0.13223 30 to 50 mph 0.28355

50 to 70 mph 0.06614

>70 mph 0.00061

Train Accident 

per train mile

2.03272E-06

Derailment Less than 30 mph 0.64969 DERAILMENTS 9.51514E-08

0.66813 30 to 50 mph 0.28355

50 to 70 mph 0.06614

>70 mph 0.00061

## Fire/explosion Remain on track

0.01546 0.95758

Fire/explosion with Subsequent Derailment

0.04242 Less than 30 mph 0.64969 Fire or Explosion and Derail 6.04185E-09

30 to 50 mph 0.28355

50 to 70 mph 0.06614

>70 mph 0.00061

Other impacts Remain on track

0.07870 0.83055

Other Impact with Subsequent Derailment OTHER IMPACT 1.84033E-09

0.16945 Less than 30 mph 0.66404

30 to 50 mph 0.27552

50 to 70 mph 0.06339

>70 mph 0.00056 * A 20% reduction for derailment was taken 

for the following accident types: Grade 

Crossing, Obstruction, Derailment, 

Fire/Explosion, and Other Impact to account

for the probability of cask derailment. 

Figure 31. Main-Line Event Tree 

83
Accident Type Outcome Speed Distribution

Probability (per 

Yard Mile) of Cask

Imapct > NRC 

Certified Speed 

Equiv. for (30 

MPH)

Highway Grade Crossing Remain on Track

0.00147 0.63636

Hwy collision with subsequent derailment <30 0.9974 Hwy-Rail X-ing Collision 2.1131E-11

0.36364 30 to 50 0.0026

> 50 0.0000

Remain on Track

Rail X Rail Crossing 0.50000

0.00011 Rail - Rail Collision with subsequent derailment

0.50000 <30 1.0000 Rail X Rail Collision 0.0

30 to 50 0.0000

> 50 0.0000

Remain on Track

Collision 0.48026 Train Collision 3.3651E-09

0.11710

Collision with Subsequent Derailments

0.51974 <30 0.9963

30 to 50 0.0037

> 50 0.0000

Remain on Track

Obstruction 0.64835

0.00830 Obstruction Collision with Subsequent 

Derailments

0.35165 <30 0.9974 Obstruction Collision 1.1531E-10

30 to 50 0.0026

> 50 0.0000

Derailment All Derailments Derailment 2.8418E-08

0.65943 0.71966 <30 0.9974

30 to 50 0.0026

Remain on Track > 50 0.0000

Fire/explosion 0.89855

0.00520 Subsequent Derailment

0.10145

Other Impacts Remain on Track Other Impacts 6.2579E-09

0.20839 0.45688

Subsequent Derailment

0.54312 <30 0.9963

30 to 50 0.0037

> 50 0.0000

Figure 32. Yard Event Tree 

84
3.3.5 Fire Event Trees 

Fires are similar to other major accident events on the event tree in that they, like collisions or 

derailments, may occur as an initiating event or, like derailments, may occur as an aftermath of the initial 

event. Both the probability that an initial fire occurs and that a fire results from another incident are of 

concern in this analysis. Since a fire may result from any node on the event tree, a separate analysis was 

constructed to represent its overall risk. 

The framework for analysis of fire risk combines the assessment of fire probability for mainline or yard 

events, as initiating or secondary events, with a measure of the likely severity of the fire. The fire 

analysis is concerned with fire intensity (temperature) and duration. Intensity is governed by the type of 

fuel available to the fire, while duration is governed by the quantity of fuel and/or the accessibility of the 

accident site to emergency mitigation. 

The major contributory factors toward cask involvement (in the hypothetical fire) must be identified. The 

initial assumption is that a train fire is a type of accident, independent of other types, and occurs at a fixed 

frequency for mainline and yard environments. The fire accident probability is 4.11×10-08 per train mile 

on the mainline and 7.74×10-08 per yard mile. The probability of a fire as an initiating event on the 

mainline is 2.8×10-08 per train mile.29 Fires as initiating events in rail yards occur 6.95×10-08 per yard 

mile. The probability of a fire as a secondary event at either location type has been estimated by 

reviewing accident report narrative descriptions in which a fire is noted. The probability of fire, given an 

accident, is 1.47×10-02 per train mile on the mainline and 4.99×10-03 per yard mile for yards. 

The next determining factor in whether the fire is likely to exceed the certified cask performance standard 

is the presence of flammable hazardous material (hazmat) cargo in either the train transporting the cask or 

in other involved train consists. The presence of potentially flammable hazmat and particularly high 

levels of flammables and combustibles near the cask car is the foremost consideration in determining 

whether the cask can be compromised by fire in an accident. The estimate of the probability of exposure 

to flammable hazmat was based upon two inputs: first, the historical accident record of hazmat 

involvement in accidents where fires occurred, and second, the probability that the hazmat involved in 

any future accident will be flammable, based upon an analysis of waybill flow data. The RAIRS database 

for years 1998-2001 indicates that hazmat was carried in 48 out of 340 fire incidents and hence have a 

heightened potential for flammable release necessary for a large engulfing pool fire. This yields a 

probability of hazmat given a fire of 48/340 or 0.14. The probability that the hazmat is highly flammable 

is based upon an analysis of the Waybill Sample for 2001 [STB, 2001]. An assessment of flammability 

of the hazardous commodities reported in the waybill was based upon the National Fire Protection 

Association (NFPA) flammability rating. Using this standard, flammable hazmat consisted of 

approximately 610 of 1,017 commodities (60 percent). This estimate of flammability is based upon 

flashpoint and interactive chemical properties. NFPA ratings for all hazmat commodities reported in the 

waybill sample could not be found, so this estimate of exposure is a likely underestimate of the total 

flammable commodities shipped in the United States. Based upon the available information, however, 

these data showed that in addition to fuel not carried as cargo, about 60 percent of all hazmat tons shipped 

are flammable (rated 1 or above on the NFPA rating scale) and could contribute to a high-temperature 

fire.30 

 

29 These rates are based upon 1988-2001 RAIRS data, including all accident reports in which fires or explosions are described as 

the initial accident event. 30 The NFPA rates commodities in five categories: (4) will rapidly or completely vaporize at normal pressure and temperature, or 

is readily dispersed in air and will burn readily; (3) liquids and solids that can be ignited under almost all ambient conditions; 

85
The probability of a flammable material release can be estimated for any train involved in an accident, 

based upon whether it is carrying hazmat. This release estimate is the percentage of hazmat cars releasing 

given an accident (3.94 percent according to FRA accident records from 1988-2001) multiplied by the 

fraction of hazmat carloads with flammables (60 percent), as estimated based on the 2001 waybill sample. 

Without hazmat, only a small probability (0.001) to (0.00001) of a small flammable release remains 

because the type of volatile material in the consist that may be available to contribute to a fire event is 

limited to locomotive fuel. In yards specific data on the volume of hazmat available for ignition cannot 

be constructed from available data. Given the presence of many more tracks, trains, and consists that may 

contain hazmat that may be in the process of switching and therefore exposed to the cask, however, an 

estimate of the likelihood of exposure is 25 percent higher than on the mainline. 

Fire events that can achieve the temperature and durations described in SNL’s analysis were identified 

based upon the reported volume of flammable hazmat shipped in the 2001 Waybill sample and an 

estimate of the duration of fires resulting from involvement of a single carload. Reported weights for a 

single carload of flammable hazmat ranged from 8 to 89 tons (7.3 to 80.7 metric tons) per carload. On 

average, a carload of flammable hazmat contains 23,000 gallons (87,0656 liters) of material. Based upon 

this assumption, the cargo will be fully consumed in a 30-ft (9-m) diameter pool fire within at least 4.5 

hours of ignition. 

The final steps in establishing a framework for comparing the likelihood of a fire that exceeds NRC’s 

cask fire certification requirement are estimating the probabilities of: (a) exposure of the cask to a pool 

fire and (b) engulfment of the cask to the required levels of intensity and duration. A statistical basis for 

estimating the frequency of these three components is not easily available. Distinguishing factors, 

however, can be described for mainline versus yard environments and on the basis of the content of the 

consist of the train carrying SNF. The assumptions used to construct the final nodes on the fire event tree 

(see Figure 33) are described below. 

Exposure of Cask to Fire. The cask could be exposed if a fire is initiated on the train or results from an 

explosion or an impact (resulting from a collision or derailment), and a car(s) carrying flammable cargo 

released its contents and caught fire. The contents of one or more hazmat cars would: (1) have to release 

and then collect, forming a fully engulfing pool fire which must equal the dimensions of the cask and (2) 

the cask would have to come to rest within that pool. Although no empirical data is available, exposure 

likelihood given an accident and a flammable hazmat cargo release is estimated to be 0.01 for the 

mainline. In yards, because more directional opportunities exist for the fire spreading from adjacent 

tracks or facilities, the estimate is four times that of the mainline (0.04). 

Cask Engulfment. Engulfment, given cask exposure, is assumed to be even more rare than cask exposure, 

perhaps as low as 1/1,000 times (0.001), but it is not dependent upon mainline or yard environments. 

There is no known parametric data to confirm this figure. This estimate is based primarily on judgment 

regarding the scenario from which a pool fire and cask engulfment could result. This scenario is difficult 

to achieve since it involves the release, subsequent pooling (into a 30-ft (9.1-m) diameter or greater pool), 

and ignition of the contents of one or more flammable hazmat carrying cars directly underneath the cask. 

Accident reports and descriptions were evaluated to determine whether lengthy fire events involving 

sufficient material could result in this type of fire. However, historically only a few fire events have 

resulted in multi-hour, high temperature fires involving enough material to create a pool fire. Lacking 

more detailed data on specific consists’ configurations and fire events, the analysis has focused on the 

presence of a flammable material in the consist as a potential contributor to the initiating event, not upon 

 

(2) must be moderately heated or exposed to relatively high temperature before ignition can occur; (1) must be preheated 

before ignition can occur; (0) materials that will not burn. See http://www.ilpi.com/msds/ref/nfpa.html. 

86
the likelihood that the fire will result in a fully engulfing fire. Therefore, this probability is uniformly 

applied to yard and mainline accident events. 

To illustrate use of the fire event tree in calculating fire probabilities (see Figure 33), this report provides 

an example here. The example calculates the probability of a fully engulfing cask fire for regular and key 

trains for combined operations on mainlines and in yards that will result in cask damage exceeding NRC 

compliance limits. Starting at the root node of the fire event tree, the overall accident rates for 

regular/key trains is 2.03272×10-6 and 1.50307×10-5 on mainlines and in yards, respectively. The next two 

branches of the tree indicate the probability of different types of accidents occurring on mainlines and in 

yards, given an accident, and the probability that each of these accident types results in a fire. For 

example, the probability of a mainline derailment, given an accident, is 0.668127465, and the probability 

that this type of accident results in a fire is 0.004029235. These two probabilities are multiplied together 

for each accident type and summed over all accident types to yield the overall probability of a fire, given 

an accident on mainlines and in yards. The results are shown in the next node of the tree as 0.0245427 

and 0.0136757 for mainlines and yards, respectively. The following node probabilities are noted in 

subsequent branches of the tree: 

• The probability of hazmat being present in the consist is approximately 0.155 and 0.0714 for 

mainline and yard accidents, respectively. 

• The probability of a flammable hazmat release, given the presence of hazmat, is 0.0280 and 

0.0145 for mainline and yard accidents, respectively. 

• The probability of a pool fire being ignited, given a flammable hazmat release, is 0.0394 for 

mainline and yard accidents. 

• The probability of cask exposure to the pool fire is 0.01 and 0.04 for mainline and yard accidents, 

respectively. 

• The probability of the cask being engulfed in the pool is 0.001 for mainline and yard accidents. 

The overall probability of a fully engulfing cask fire for combined regular and key train operations on 

mainlines and in yards will be the sum of their separate mainline and yard probabilities. The mainline 

probability will be the product of the mainline accident rate times the probability of a fire, given an 

accident, times the probability of hazmat being present in the consist, given an accident, times the 

probability of a flammable hazmat release, given the presence of hazmat, times the probability of a pool 

fire being ignited, given a flammable hazmat release, times the probability of the cask being exposed, 

given a pool fire, times the probability of the cask being engulfed, given that it is exposed to the pool fire: 

Pr (Fire/Mainline > limits) = (2.03272×10-6) × (0.0245427) × (0.154798762) × (0.028015564) × (0.0394) ×

(0.01) × (0.001) = 8.5244×10-16

The corresponding probability for yard fire accidents, Pr (Fire/Yard > limits), is 3.3455×10-15. 

The combined probability for regular and key train operations on mainlines and in yards of accidents 

resulting in fires that will damage the cask in excess of NRC compliance limits is 4.1979×10-15, which is

the sum of the two probabilities above. 

87
Figure 1. Fire Event Tree 

Accident Type

HAZMAT 

Carried / 

Involved?

Flammable 

Released Typ

Prob hazmat released* fraction flam/hazmat:

0.6

Fire 

ml 0.014799154 

Grade Crossing Incident yd 0 Pool Fir

Reg/Key ml 0.148062355 0.394

Reg/Key yd 0.001471593 No Fire

Ded ml 0.153920208 ml 0.985200846 

Ded yd 0.003019926 yd 1 

Fire Flam Release

ml 0 ml 0.028015564

Rail/Rail Crossing Incident yd 0 yd 0.014457831

Reg/Key ml 0.000876479

Reg/Key yd 0.000105114 No Fire Other (N

Ded ml 0.000911156 ml 1 0.606

Ded yd 0.000215709 yd 1

Train 

Accident Fire HAZMAT

Reg/Key Mainline 2.03272E-06 ml 0.038081805 Reg/Key ml 0.154798762

Reg/Key Yard 1.50307E-05 Collision / Obstruction yd 0.001338056 Reg/Key yd 0.071428571

Ded Mainline 1.95536E-06 Reg/Key ml 0.088774807 Ded ml 0.025686729 Other Fl

Ded Yard 3.75768E-06 Reg/Key yd 0.125400746 No Fire Ded yd 0.008928571 0.175

Ded ml 0.092287042 ml 0.961918195 No Flam Release

Ded yd 0.257340847 yd 0.998661944 ml 0.971984436

yd 0.985542169

Fire Fire

ml 0.004029235 Reg/Key ml 0.02454271

Derailment yd 0.000159401 Reg/Key yd 0.00589724

Reg/Key ml 0.668127465 Ded ml 0.0255137

Reg/Key yd 0.659431334 No Fire Ded yd 0.012102

Ded ml 0.69456087 ml 0.995970765

Ded yd 1.353250465 yd 0.999840599

Fire

ml 1

Fire / Explosion yd 1 No HAZMAT

Reg/Key ml 0.015463595 Reg/Key ml 0.845201238

Reg/Key yd 0.005203132 No Fire RegKey yd 0.928571429

Ded ml 0.016075387 ml 0 Ded ml 0.974313271 Other Fl

Ded yd 0.010677596 yd 0 Ded yd 0.991071429 0.175

Fire

ml 0.010342084

Other yd 0.002017654

Reg/Key ml 0.07882051

Reg/Key yd 0.208755978 No Fire

Ded ml 0.081938918 ml 0.989657916

Ded yd 0.428398091 yd 0.997982346

Fire

Figure 35. Fire Event tree 

88 

 88
3.4 Modified Event Tree–Dedicated Trains 

An event tree based upon 14 years of rail accident history was constructed, to describe the probability of 

an accident. The event tree provides a basis for the probability assessment of accident likelihood 

involving the shipment of spent fuel by regular trains and can be used to predict how changes in train 

configurations or operational rules might affect accident likelihood. This event tree describes how likely 

it is that any train, independent of train makeup or environment, might be involved in an accident. The 

event trees are limited to a historical view of accidents, and in that sense, fail to reflect how trends in the 

use of different equipment, changes in operational factors (such as train density), and introduction of 

different train sets might affect future risk. The long time period included in the dataset, however, helps 

to compensate for historical trends in accident frequency. Some factors cannot be accounted for, such as 

the implementation of high-speed rail in many of the highest population density corridors of the country, 

which exposes trains to accidents that are of a higher velocity than most of those experienced in the 

accident time period of estimation. The deployment of 110 mph (177 km/hr) trains in corridors that may 

also experience spent fuel shipments poses a concern for risks of a high-speed collision, passenger 

exposure, and other significant consequences; this risk should therefore be included in this analysis. A 

list of proposed high-speed rail corridors appears in Appendix F. 

Dedicated and regular trains are expected to operate in different manners. Operational restrictions 

primarily affect the likelihood that a train is exposed to particular scenario, such as a collision or 

derailment, and the environment in which the accident might happen (and therefore its likely speed and 

severity). The baseline event tree (based on historical accident rates) was modified to reflect operational 

restrictions, consist content limits, speed limits, and other special constraints to be applied to the 

shipment, as well as differences in the lengths of regular and dedicated trains. This was accomplished by 

recalculating the probability that a particular type of accident might occur, that an accident would occur in 

a specific environment, or that the severity of the accident would be affected. In general, these 

operational restrictions and consist constraints reduce the accident probability. Each of these adjustments 

to the event tree was made to reflect how the accident probability for individual shipments might vary. 

Since the total number of additional trains generated by using dedicated trains represents a small fraction 

of total train volume, no specific adjustment for increases in train density was made in this analysis. 

Table 28 lists the adjustments to the accident rate that have been made for each section of the event tree in 

order to reflect these estimates of how the combination of operational restrictions and the dedicated 

consist contributes to overall accident risk. 

The methodology for estimating the non-catastrophic accident analysis involved a comparison of accident 

probability due to changing five aspects of service: 

• Yard entries 

• Train consist length or configuration 

• No pass rule for dedicated trains (not key trains as defined by AAR) 

• Speed limit 

• Other hazmat in consist (not in dedicated trains but possible in key trains as defined by AAR) 

89
Table 28. Adjustments to Baseline Accident Rate for Dedicated Train Service 

Accident Type 

Factors that Affect Accident 

Rate 

Dedicated Train Rate Adjustment Factor 

(Probability or Severity) 

Change in 

Probability 

(Increase 

Decrease 

No Change) 

Consist Length Reduces derailment rate Decrease Single Train 

Derailment Consist Configuration Effects 

on Train Handling 

Significantly reduces train handling 

accidents. Decrease 

Speed Factor 

Change in accident severity by reducing 

accident frequency for high-speed collisions. 

Reduction in expected accident severity in all 

scenarios depending upon route. 

Decrease 

Collision/ Yard Entry Rate Yard entry rate reduced or eliminated Decrease 

Obstruction 

No Passing Rule 

Reduction in raking collision rate in double 

track territory if dedicated train holds the 

main in other meets/passes, reduces 

derailment probability. 

Decrease 

Train Frequency 

(no passing rule) 

Increase frequency of trains may increase 

number of accidents. Improved stopping 

distances, train handling, pre-inspection, and 

use of escorts may, however, reduce accident 

probability. 

No Change 

Highway-Rail 

Grade Crossing 

or Rail-Rail 

Train Length Reduction in derailment probability, 

improvement in braking capability. Decrease 

Speed Factor Improvement in braking capability, severity 

reduction. Decrease 

Fire Train Length Reduction in derailment probability. Decrease 

No Hazmat in Consist Reduction in fire probability. Decrease 

Other Train Handling Reduction in derailment probability. Decrease 

3.4.1 Yard Entry Modifications 

The greatest difference in terms of operational behavior between a regular and dedicated train is the 

ability to conduct run-through service. This is because the required regular train entries in yards for 

reclassification adds time and risk to transportation. For that reason, and because the accident rates in 

yards and on the mainline are so dramatically different, the analysis of the accident rates has been 

subdivided into two categories, mainline and yard. 

Many previous analyses have assumed that accident probability, severity, and consequences are 

independent of the environments in which they occur. This assumption leads to the blanket application of 

a general or universal accident rate to all environments and all trains. It can easily be demonstrated, 

however, that accident involvement of trains can be affected by train makeup, track environment, and 

operational constraints. The significant differences between dedicated and regular trains with respect to 

the accident rate lie in the differences attributable to these three characteristics. Environmental and 

spatial factors were examined for a typical route (see Figure 34). The grouping of accidents around yards 

on the Humboldt route illustrates the tendency of accidents to cluster spatially, especially in higher traffic 

areas. 

90
Figure 34. Humboldt, CA, to Yucca, NV, Rail Route Illustrating Accident Locations (1988-1997) 

Table 28 illustrates a comparison of the effect of train environment on the accident rate. This table 

categorizes the total reported train accidents for 1988-2001 that were described with respect to the 

location of their occurrence into five accident categories. 

The total train miles in yards and on the mainline have also been calculated for those years. These sums 

reveal that the accident rate per train mile in yards is over seven times the rate on the mainline. Accident 

rates on the mainline are roughly 2.03 per million train miles (see Figure 31), while the rate for yards is 

15 per million yard miles (see Figure 32). This information is significant in comparing methods of 

shipment that would avoid yard entries or limit classification stops in yards. Reduction of yard entries by 

conducting run-through service will significantly affect accident probability by reducing exposure to one 

of the highest accident rate environments during shipment. If a train were able to avoid certain 

environments, the exposure to situations where accidents could occur would similarly decrease. This 

analysis assumes that although dedicated trains will have to stop in some yards, they will not have to stop 

in all yards or their stops will not involve classification activities within the yard. Based upon a 

hypothetical analysis of the six representative routes described in the incident-free analysis using the 

91
BNSF’s logistics planning model [BNSF, 2000], therefore the number of yard entries might be cut by 7 

percent, and the time spent in yards is cut by 75 percent compared to regular train service. Applying this 

75 percent reduction results in a reduction in the yard accident portion of the event tree due to yard 

exposure from 1.50×10-05 yard miles to 3.76×10-06 yard miles for dedicated trains. 

3.4.1.1 Train Consist Length/Configuration Modifications 

Train stability is enhanced when the arrangement of cars in the train minimizes dynamic instability due to 

load positioning. Trains in which the loads are inappropriately arranged can be dangerously unstable in 

transport. Even in the absence of incorrect load arrangement, dynamic instability is an issue when 

oversized or unusually heavy freight cars are included in train consists. Three factors are used to describe 

the stability of a train, the ratio of the weight of the cars to the locomotives, number of axles, and 

distribution of weight within the train consist. Simulations of train makeup comparing dedicated train 

configurations and regular train configurations with the cask consist at the rear of the train illustrate the 

unfavorable train-track dynamics resulting from the regular train configuration. A comparison of train 

forces exerted on different cars in a train for specific maneuvers and on particular routes was made. The 

results were used to compare how the configuration of the train (including position of the cask car and 

buffer cars) and train length, contribute to forces that may influence derailment risk. Figure illustrates 

the difference in forces exerted on the car in the middle of a 70-car train versus within the consist of a sixcar dedicated train in a situation where an emergency brake application has been made. Forces on the car 

in the cask position when braking from 50 mph (80.4 km/hr) are significantly higher in the longer train 

consist than would be experienced in a shorter, dedicated train. These unfavorable forces could 

contribute to an increased derailment risk. 

Train handling related incidents and accidents occur when either the individuals responsible for 

constructing trains in a yard fail to properly position the cars in the train so as to minimize dynamic 

instability in transit or the train operator fails to properly control the train during transit. The frequency of 

these events can be calculated based upon RAIRS accident data, which report accidents caused by 

improper train makeup or handling. On mainline track, 592 of these accidents (8.6 percent of total 

derailments) were reported in RAIRS between 1988-2001. If accident rates reflect the risk experienced 

by properly built trains not carrying oversized loads, it is possible to adjust that rate to reflect how the 

oversized loads might increase accident potential. This adjustment was made in the analysis to forecast 

what the specific effects of shipping the 125-ton (113-metric ton) cask may be as a worst case. Train 

accident involvement rates for collisions, grade crossing accidents, fires, and obstructions are not likely to 

be affected by train makeup. The most significant likely effect is in the derailment rate. Therefore, this 

analysis has assumed that the derailment accident rate should be augmented to reflect factors affected by 

the 125-ton (113-metric ton) cask. It is reasonable to assume that 50 percent of these train-handling 

accidents would be significantly reduced or eliminated in short trains with six or fewer cars. 

92
Regular versus Dedicated Train/50 mph/ Downhill

-200000

-150000

-100000

-50000

0

50000

100000

150000

0 10 20 30 40 50 60

Time (sec)

Force (lbs)

Dedicated (Loaded) 104 Car (Loaded)

Figure 35. Train Simulation of Railcar Forces Under Emergency Brake Application–50 mph 

 (80.4 km/hr) 

3.4.1.2 No-Pass Rule Modifications 

Accident involvement in raking collisions may be reduced if a no-passing rule is imposed. The effect of 

this operational constraint should be to reduce the probability of raking collisions between train consists 

on the mainline. This rule would not necessarily affect other raking collisions, such as train consist 

impacts with bridges. In this analysis, the estimated effect of the no-passing rule on the mainline was the 

elimination of all raking collisions, which account for approximately 20 percent31 of all mainline 

collisions. 

3.4.1.3 Speed Limit Modifications 

An examination of speed factors in determining the likelihood and severity of accidents was conducted 

using the same 1988-2001 dataset of accidents. A comparison of the likelihood of a derailment at a given 

speed for collisions and single train derailment accidents, as well as the number of cars derailing given a 

derailment, was made for accidents in the seven speed categories defined for the accident severity 

analysis shown in Table 29. 

This approach shows that increased speed does not factor significantly in the frequency of accidents, since 

more accidents occur at lower speeds. Determination of accident rates by speed categories would require 

mileage data for these categories. Since these detailed data are not available for this analysis, a reduction 

in accident probability (per train mile) at higher speeds could not be assumed. The most conservative 

 

31 Based upon RAIRS data, total raking collisions were 163 of 813 mainline collisions during the study period (1988-2001). 

93
assumption is that the accident rate remains constant and that only accident severity decreases with speed 

restrictions. The table illustrates that, on average, nearly 66 percent of reported mainline accidents in 

RAIRS occur at less than 35 mph (56.3 km/hr). Therefore, imposition of speed limits on dedicated trains 

is unlikely to reduce the overall frequency of accidents. This does not mean that accident severity (and 

therefore overall risk) is also unaffected. The speed effects are reflected in the event trees only by 

reducing the probability that the accident event will happen at speeds above the constrained limit, not by 

reducing accident probabilities overall. 

Table 29. Speed Distribution of Mainline Accidents (1988-2001) 

SPEED CATEGORIES 

Accident 

Type 

Less than 

35 mph 

(56.3 km/hr)

35 to 55 

mph 

(56.3 to 88.5 

km/hr)

55 to 65 

mph 

(88.5 to 

104.6 km/hr)

65 to 70 

mph 

(104.6 to 

112.6 km/hr)

70 to 75 

mph 

(112.6 to 

120.7 km/hr)

75 to 106 

mph 

(120.7 to 

170.5 km/hr)

Greater 

than 106 

mph 

(170.5 km/hr)

Collisions 85.80% 10.57% 1.48% 0.34% 0.07% 0.94% 0.61% 

Obstructions 58.09% 22.68% 8.15% 2.42% 1.91% 6.11% 0.64% 

Derailments 79.54% 17.76% 2.12% 0.36% 0.06% 0.16% 0.00% 

Grade 

Crossing 40.17% 38.18% 9.87% 4.33% 1.40% 6.05% 0.00% 

Average by 

Speed 

Categories 

65.90% 17.50% 0.60% 0.60% 0.40% 1.20% 0.40% 

A second issue with respect to speed is the question of how speed contributes to accident severity and 

whether that contribution changes depending upon train length. This is important because the likelihood 

of cask involvement in a derailment given an accident is of concern, as well as the likely duration of the 

response to the incident. The fewer the number of derailing cars, the shorter the response duration and 

derailment recovery time required. Therefore, both questions are addressed in this analysis. Measuring 

severity in terms of the number of cars that derailed in accidents that involved either collisions or noncollision related derailments at given speeds and for given train lengths provides insights into both of 

these questions. 

3.4.2 Train Length, Speed, and Accident Severity 

The relationship between train length and reported accident speed on derailments was examined for the 

accidents included in this analysis since both of these factors would be constrained in dedicated trains 

(compared to regular or key trains). The reason to constrain either of these factors is the expected 

reduction in risk, either by reducing the likelihood of accident involvement or reducing the expected 

severity of accidents. This section attempts to understand how train length and speed affect the expected 

severity of the derailment. Using RAIRS accident reports from 1988-2001, the accident type and number 

of derailing cars for accidents that had been classified as either derailments or collisions were analyzed. 

Derailments also occur in many collisions. Since the accident initiates with a train collision, however, it 

is classified in that category in RAIRS. By inspecting fields in the accident record that describe the 

number of derailed cars, it is possible to determine whether a subsequent derailment occurred after a train 

collision. Likewise, it is possible to determine (based upon other fields in the accident record) how many 

cars were in the train consist and how many of those derailed (referred to here as the derailment fraction). 

94
Derailment-only and collision-related derailment accidents differ in the number of cars that typically 

derail. In derailment-only accidents, 66.5 percent of all accidents result in a derailment of five cars or 

less. In collision-related derailments, that number is 94.2 percent. To provide a more normalized 

comparison, the fraction of the number of cars that typically derail in accidents was also calculated. In 

derailment-only accidents, 53.3 percent of all accidents result in a derailment of 10 percent of the consist 

or less (see Figure 36), while 79.36 percent of all collision-related accidents result in a derailment of 10 

percent of the consist or less (see Figure 37). 

These data suggest that in both types of accidents it is most probable for the number of derailed cars to be 

less than 10 percent of the train consist, in a six-car train, about one car. The rest of this analysis focuses 

on how the two factors potentially affected by dedicated train requirements, train length and speed, could 

affect the derailment outcome. 

Dedicated trains are assumed to be short, six cars or less. Key trains and regular trains are not constrained 

with respect to length. To make a comparison between the three types of service, the data have been 

disaggregated by train length and grouped into the following categories: 6 cars or less, 7 to 50 cars, 51 to 

100 cars, and over 100 cars. Some differences between derailment-only and collision-related derailments 

exist; therefore, Figure 38 presents the data for each type of accident separately. 

53.30%

84.81%

95.19% 97.03% 99.97%

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0.10 0.25 0.50 0.75 1.00

Derailed/Total Cars in Consist (fraction)

Frequency 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Cumulative Percentage of All Accidents

Frequency

Cumulative %

 Source: RAIRS 

Figure 36. Fraction of Total Number of Cars in Consist Derailed in Derailment-Only 

Accidents (1988-2001) 

95
79.36%

88.08%

93.83% 94.84%

100.00%

0

500

1000

1500

2000

2500

3000

3500

4000

0.10 0.25 0.50 0.75 1.00

Derailed Cars/Total Cars in Consist (fraction)

Frequency 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Cumulative Percentage of All Accidents

Frequency

Cumulative %

 Source: RAIRS 

Figure 37. Fraction of Total Number of Cars in Consist Derailed in Collision-Related 

Derailments (1988-2001) 

0

1

2

3

4

5

6

7

8

9

6 Cars or Less 7 to 50 Cars 51 to 100 Cars Over 100 Cars

Train Length

Average Number of Cars Derailed

Collision

Derailment

 Source: RAIRS 

Figure 38. Average Number of Cars Derailed in All Derailments by Train Length (1988-

2001) (Derailment-Only and Collision-Related Derailments) 

96
This comparison is interesting since the number of cars derailed in each case increases with train length. 

This suggests that in derailment accidents, the risk associated with an accident may also increase with 

train length. This increase in risk may be the result of changes in the likely consequences of the accident. 

In derailments, the probability that the cask-carrying car will be the car that derails in the accident does 

not increase with train length, since the fraction of cars that derail decreases in both collisions and 

derailments as train length increases. Since the total number of cars derailed increases on average, 

however, the time to clear the wreck after the event will increase due to the increase in the total number of 

derailed cars. Since the duration of the wreck clearing time affects the total population exposure to 

radiation associated with each event, the risk also increases. 

The second factor evaluated in this analysis was the potential effect of the 50-mph speed limit on risk. In 

this analysis, the number of collision-related derailments and derailment-only accidents in each speed 

category were compared. The two speed categories evaluated were 50 mph and less and greater than 50 

mph. On average, three or fewer cars derailed in collision-related derailment accidents at less than 50 

mph, and the average was five in derailments in the same speed category (see Figure 39). In accidents at 

speeds greater than 50 mph, the averages were around 8 and nearly 12, respectively. The severity of 

derailment accidents is different than collision-related derailments; in this case, the fraction of the consist 

that derails, given a derailment, goes from 15 percent of trains of six cars or less to 23 percent in 

derailments at greater than 50 mph. The percentage of the consist that derails in collision-related 

derailments remains about the same for those categories (ranging from 12 percent in the lower speed 

category to about 10 percent in the higher speed category). The data suggest that high-speed derailments 

are likely to result in more derailed cars, per derailment, and result in higher risk for transportation of the 

spent-fuel cask. 

0

2

4

6

8

10

12

14

Less Than or Equal to 50 mph Greater than 50 mph

Train Speed

Average Number of Cars Derailed

Collision

Derailment

 Source: RAIRS 

Figure 39. Average Number of Cars Derailed by Train Speed (1998-2001) (Derailment-Only 

and Collision-Related Derailments) 

97
3.5 Modified Event Tree for Dedicated Trains–Results 

In Section 3.3, the probability of an accident for regular trains was estimated. This section compares that 

result with the accident probability for dedicated trains, calculated by applying operational restrictions 

and carrying a short consist that includes only locomotive(s), buffer cars, and the cask car accompanied 

by a caboose or escort car. The resulting event tree illustrates the probability that the dedicated train has 

an accident and that the accident is at a velocity sufficient to exceed the equivalent compliance 

requirement velocity. The only known speed in historical accident records is the reported train speed at 

the time of the accident; this is not necessarily the impact velocity of every car in the consist. Absent a 

better measure of the velocity, however, all accidents have been categorized with respect to this reported 

velocity, and appropriate reductions applied where speed limits, speed mitigation, or other factors are 

expected to apply. The result of this is a new event tree, identical in form to the regular train event tree 

but with different probabilities to reflect the operational restrictions placed on the dedicated train (see 

Figure 40). 

Table 30 shows the cumulative effects on the event trees of the modifications in event probabilities. The 

effect of reducing the speed of the dedicated train, using operational restrictions that eliminate passing 

trains, and using consist arrangements that eliminate train-handling accidents would be to reduce the 

overall probability of a train-to-train collision by approximately 20 percent, and the probability of a trainto-train collision that exceeds regulatory compliance is reduced by about 50 percent. This reduction in 

train-to-train collisions is due to the combined effects of the dedicated train being limited to 50 mph (80.4 

km/hr), the elimination of raking collisions since dedicated trains are not allowed to pass other moving 

trains, and the avoidance of 50 percent of all train-to-train collisions above 50 mph (80.4 km/hr). This 50 

percent factor reflects the assumption that, since only one of the two train speeds is recorded in accident 

reports, a 50 percent probability exists that the speed not reported could be above 50 mph (80.4 km/hr), 

even though the dedicated train speed is less than 50 mph (80.4 km/hr). The reduction in overall 

derailment probability by using dedicated trains is about 4 percent, while the reduction in the probability 

of a high-speed derailment that could result in an impact that exceeds regulatory compliance is 

approximately 23 percent. 

The cumulative effect of the operational restrictions described in this section is reflected in a small 

reduction in the mainline accident rate from 2.03×10-06 per train mile to 1.96×10-06 per train mile or 

roughly 3.8 percent. The further expected reduction in yard accidents due to a 75 percent reduction in 

time spent in yards reduces the yard accident rate from 1.50×10-05 per yard mile to 3.76×10-06 per yard 

mile. 

To illustrate use of the mainline event tree in calculating accident probabilities for dedicated trains (see 

Figure 40), an example is provided here. The example calculates the probability that collisions of 

dedicated trains operating on mainlines will result in cask impacts that exceed regulatory compliance 

limits. In this example, the rear-end or side accident type branch of the tree is of interest. From the event 

tree, the overall mainline dedicated train accident rate is 1.9554×10-6; the probability of a rear-end or side 

collision is 0.02968; and the probability of a derailment following a rear-end or side collision is 0.53289. 

Furthermore, the following distribution of train speeds for rear-end or side derailments exists: less than 

30 mph, 0.66404; 30 mph to 50 mph, 0.27552; 50 mph to 70 mph, 0.06339; and greater than 70 mph, 

0.00056. As discussed above, for train-to-train collisions, a 0.50 probability exists that collisions above 

50 mph will be avoided. Finally, for all train derailments, including those that result from initial 

collisions, the cask car has a 0.20 probability of actually derailing. As discussed in Section 3.2.2 and in 

Table 28, it was determined that, for rear-end or side derailments, the critical speed is 50 mph; that is, 

rear-end or side derailments with initial train speeds greater than 50 mph will result in cask damage that 

98
exceeds regulatory compliance limits. The train speed probabilities of interest in the event tree will 

therefore be the sum of those above 50 mph. Given the above, the calculation for the probability of rearend or side collisions resulting in damage to casks that exceeds regulatory limits is as follows: 

Pr (rear end or side collision > limits) = (1.9554×10-6) × (0.02968) × (0.53289) × (0.06339 + 0.00056) ×

(0.50) × (0.20) = 1.9778×10-10. 

Minor differences between these results and the event tree result from round-off errors. 

Table 30. Regular versus Dedicated Train Results–Probability per Train Mile 

Probability per Train Mile 

Accident Type (Main and Yard) 

Regular Train Dedicated Train 

Mainline Accident Rate 2.03×10-06 1.96×10-06

Train-Train Collision 1.05×10-07 8.45×10-08

Train-Train Collision at Greater than NRC Cask Certification Equivalent 

Velocity 4.05×10-10 2.02×10-08

Derailment 1.36×10-06 1.30×10-06

Derailment at Greater than NRC Cask Certification Equivalent Velocity 9.52×10-08 7.37×10-08

Highway-Rail Grade Crossing 3.01×10-07 3.01×10-07

Highway-Rail Grade Crossing Impact at Greater than NRC Cask Certification 

Equivalent Velocity 3.38×10-09 2.74×10-09

Other 2.37×10-07 2.37×10-07

Other Accidents at Greater than NRC Cask Certification Equivalent Velocity 2.55×10-09 2.07×10-09

Fire 3.14×10-08 3.14×10-08

Engulfing Fire at Greater than NRC Cask Certification Duration and Intensity 4.20×10-15 4.66×10-16

Yard Accidents (per yard switching mile) 1.50×10-05 3.76×10-06

Yard Accidents at Greater than NRC Cask Certification Equivalent Velocity 3.82×10-08 9.54×10-09

Regular versus Dedicated Train Effect Difference 

Regular versus Dedicated 

Collision Difference -2.07×10-08

Collision at Greater than NRC Cask Certification Speed (Difference) -2.03×10-10

Derailment Difference -5.84×10-08

Derailment at Greater than NRC Cask Certification Speed (Difference) -2.14×10-08

Highway-Rail Grade Crossing Difference 0 

Highway-Rail Grade Crossing at Greater than NRC Certification Speed 

(Difference) -6.44×10-10

Yard Difference -1.13×10-05

Yard at Greater than NRC Certification Speed (Difference) -2.86×10-08

Fire Involvement Difference 0 

Engulfing Fire (Difference) -3.73×10-15

. 

99
1988-2001 Accident Type Outcome Speed Distributions (Main)

Probability (per Train Mile) of 

Cask Imapct > NRC 

Certified Speed Equiv. for (30 

MPH)

Remain on Track

Highway Grade Crossing 0.83975 Less than 30 mph 0.64969 HWY GRADE XING 2.73523E-09

0.15392 Hwy Grade Crossing Collision Followed by Derail 30 to 50 mph 0.28355

0.16025 50 to 70 mph 0.06614

>70 mph 0.00061

Rail - Rail Crossing Remain on Track

0.00091 0.35714

Rail Xing Collision Followed by Derailment Less than 30 mph 0.77738 RAIL*RAIL XING 3.93872E-12

0.64286 30 to 50 mph 0.18824

50 to 70 mph 0.03439

>70 mph 0.00000

Remain on Track

0.60224

Head on, Raking, Broken 

Train Collision Collision Followed by Derailment Less than 30 mph 0.66404

Head On Broken Train or 

Raking Collision 5.4738E-13

0.01263 0.39776 30 to 50 mph 0.27552

50 to 70 mph 0.06339

>70 mph 0.00056

Remain on Track

0.46711

Rear end or Side Collision Collision Followed by Derailment

0.02968 0.53289 Less than 30 mph 0.66404 Rear end or Side Collision 1.97739E-10

30 to 50 mph 0.27552

50 to 70 mph 0.06339

>70 mph 0.00056

Obstruction Remain on Track

0.03937 0.86777

Obstruction Collision Followed by Derailment Less than 30 mph 0.64969 OBSTRUCTION 5.77357E-10

0.13223 30 to 50 mph 0.28355

50 to 70 mph 0.06614

>70 mph 0.00061

Train Accident 

per train mile

1.9554E-06 Derailment Less than 30 mph 0.64969 DERAILMENTS 7.37075E-08

0.66469 30 to 50 mph 0.28355

50 to 70 mph 0.06614

Main only >70 mph 0.00061

Train Accident

1.0000 Fire/explosion Remain on track

0.01608 0.95758

Fire/explosion with Subsequent Derailment

0.04242 Less than 30 mph 0.64969 Fire or Explosion and Derail 7.56250E-11

30 to 50 mph 0.28355

50 to 70 mph 0.06614

>70 mph 0.00061

Other impacts Remain on track

0.08181 0.83055

Other Impact with Subsequent Derailment OTHER IMPACT 1.4936764373E-09

0.16945 Less than 30 mph 0.66404

30 to 50 mph 0.27552

50 to 70 mph 0.06339

>70 mph 0.00056

Figure 40. Modified Event Tree--Dedicated Trains on Mainline 

100
3.6 Effect of AAR Circular no. OT-55-D, Recommended Railroad Operating Practices 

for Transportation of Hazardous Materials 

When this study was initiated, AAR had not issued the recommended practice described in this section. 

The operational restrictions and definitions of dedicated train service included all of those factors 

described in the previous sections. 

In August 2001, AAR issued OT-55-D, which refers to trains that carry one or more carloads of SNF as 

key trains. Their recommended operational restrictions for this type of service are described in this 

excerpt from OT-55-D: 

Key Trains 

Definition: Any train with five tank car loads of Poison Inhalation Hazard (Hazard Zone A) or 20 car 

loads or intermodal portable tank loads of a combination of PIH (Hazard Zone A) or flammable gas, 

Class 1.1 or 1.2 explosives, and environmentally sensitive chemicals, or one or more car loads of 

spent nuclear fuel (SNF) or high level radioactive waste (HLRW) shall be called a “key train.” 

Attached as Appendix A is a list of PIH (Hazard Zone A or B) and environmentally sensitive 

chemicals with 49 Hazmat Codes. 

Restrictions: 

1. Maximum speed–key train - 50 mph (80.4 km/hr). 

2. Unless siding or auxiliary track meets FRA Class 2 standards, a key train will hold main track at 

meeting or passing points, when practicable. 

3. Only cars equipped with roller bearings will be allowed in a key train. 

4. If a defect in a key train bearing is reported by a wayside detector, but a visual inspection fails to 

confirm evidence of a defect, the train will not exceed 30 mph (56.3 km/hr) until it has passed 

over the next wayside detector or delivered to a terminal for a mechanical inspection. If the same 

car again sets off the next detector or is found to be defective, it must be set out from the train.32

The effect of these new operational restrictions on the risk of shipping HLRW can be analyzed in terms of 

their reduction in accident probability or severity relative to regular trains. Table 31 shows the 

assumptions used as a basis for comparing the effect of using key trains versus dedicated or regular trains. 

Key trains have only a few specific operational restrictions, and the recommended practice does not 

specifically require that they be short trains. Therefore, the impact on derailment accident probability due 

to consist length or configuration is expected to be unchanged relative to the rate for regular trains, 

including train-handling effects. The rail car used to transport spent fuel is expected to be a special car, 

designed to provide better handling than standard fleet cars. It is conservatively assumed, however, that 

the effect of this special car design does not reduce the derailment accident probability for the train since 

other cars in the consist might also derail. 

The speed restriction for key trains affects the expected severity of accidents in the same way that it 

would affect dedicated train accident severity. It is assumed that this speed restriction would also 

improve the ability of the key train to respond to emergencies where rapid braking would be required. 

The braking improvement resulting from the speed restriction should also reduce the likely severity of 

highway grade-crossing accidents similar to dedicated trains. 

Since the content of the train consist is not restricted, the possibility of yard entries at a frequency equal to 

regular trains must be assumed. Therefore, the expected accident rate in yards is estimated to be equal to 

that of regular trains. 

 

32 AAR, August 30, 2001. 

101
Key trains allow passing on the main with the exception of passes where the track class is less than Class 

2. The frequency of key train exposure to this type and condition of track on the main railroad line is 

expected to be infrequent, by comparison to higher quality (Class 3 or above) track. Since the exposure is 

low, it is assumed that the restriction on Class 2 track affects only a small number of the total number of 

train passes that the key train might make during a shipment. It is assumed, therefore, that the raking 

collision probability, and thus the overall train-to-train collision probability for key trains, is equal to that 

of regular trains. 

The impact of the key train recommended practice on the number of trains, and therefore the frequency of 

highway grade-crossing accidents, is assumed to be equal to that of regular trains since it is not clear how 

many (if any) additional trains would be generated under a key train requirement. 

Fire risk (probability and severity) for key trains is assumed to be equal to that of regular trains since the 

recommended practice does not require a limitation on the placement of other hazmat in the consist in 

excess of hazardous materials shipping regulations. It does not restrict yard entries, and it does not hold 

oncoming traffic in a train-meet or pass. Therefore, all of the scenarios that could result in a fire 

involving a regular train could also occur with a key train. Since one of the criteria for key train 

designation is 20 car loads or intermodal portable tank loads of a combination of PIH (Hazard Zone A or 

B), flammable gas, Class 1.1 or 1.2 explosives, and environmentally sensitive chemicals, this assumption 

is conservative since the likely number of key trains with 20 or more cars of flammable gas is significant. 

Table 32 summarized the numerical results of applying these assumptions for key trains compared to 

regular trains. The differences in results between key trains and regular trains are due solely to speed 

restrictions placed on key trains. The overall mainline and yard accident rates for key trains and regular 

trains are the same since speed is not assumed to influence overall rates. The overall accident rates for 

key trains for the specific categories of accidents investigated (train-to-train, derailments, highway-rail 

crossing, other, and fire) are also the same as for regular trains. The likelihood that these accidents will 

exceed NRC compliance limits for mainline operations, however, is less for key trains than regular trains 

since key trains are restricted to speeds less than 50 mph. The likelihood of yard accidents exceeding 

NRC compliance limits is the same for key and regular trains since their speeds are similar in yards. 

Table 31. Assumptions for Service Type–Key Train 

Accident Type Factors that Affect 

Accident Rate 

Key Train Rate Adjustment Factor 

(Probability or Severity) 

Change in Probability 

(Increase, Decrease, 

No Change) 

Single Train Consist Length Effect Consist length might remain the same as regular train. No Change 

Derailment Consist Configuration Consist configuration not affected. No Change 

Speed Factor Speeds held to 50 mph (80.4 km/hr) for key train. Decrease 

Yard Entry Rate Yard entries could equal regular train. No Change Collision/Obstruction 

Train Frequency Key trains allow passing on the main. Key train holds 

main where track class is <2. No Change 

Train Frequency Number of trains generated by key train rules could be 

equal to, less than, or greater than with regular trains. No Change 

Train Length Key train lengths are not necessarily shorter. No Change 

Highway-Rail or 

Rail-Rail Crossing 

Speed Factor Speed reduction should improve braking. Decrease 

Train Length Length of train not necessarily shorter than regular 

train. No Change 

Fire 

No Hazmat in Consist Other hazmat (including flammables) might be in 

consist. No Change 

Other Train Handling Train makeup not necessarily different. No Change 

102
Table 32. Regular Train versus Key Train Results–Probability per Train Mile 

Probability per Train Mile 

Accident Type (Main and Yard) 

Regular Train Key Train 

Mainline Accident Rate 2.03×10-06 2.03×10-06

Train-Train Collision 1.05×10-07 1.05×10-07

Train-Train Collision at Greater than NRC Cask 

Certification Equivalent Velocity 4.05×10-10 2.03×10-10

Derailment 1.36×10-06 1.36×10-06

Derailment at Greater than NRC Cask Certification 

Equivalent Velocity 9.52×10-08 7.70×10-08

Highway-Rail Crossing 3.01×10-07 3.01×10-07

Highway-Rail Crossing Impact at Greater than NRC 

Cask Certification Equivalent Velocity 3.38×10-09 2.74×10-09

Other 2.37×10-07 2.37×10-07

Other Accidents at Greater than NRC Cask 

Certification Equivalent Velocity 2.55×10-09 2.07×10-09

Fire 3.14×10-08 3.14×10-08

Engulfing Fire at Greater than NRC Cask 

Certification Compliance Duration and Intensity 4.20×10-15 4.20×10-15

Yard Accidents (per yard switching mile) 1.50×10-05 1.50×10-05

Yard Accident at Greater than NRC Cask Certification

Equivalent Velocity 3.82×10-08 3.82×10-08 

Regular versus Key Train Effect Difference 

Regular versus Key 

Collision Difference 0 

Collision at Greater than NRC Cask Certification 

Speed (difference) -2.03×10-10

Derailment Difference 0 

Derailment at Greater than NRC Cask Certification 

Speed (difference) -1.81×10-08

Highway-Rail Grade Crossing Difference 0 

Highway-Rail Crossing at Greater than NRC Cask 

Certification Speed (difference) -6.44×10-10

Table 33 summarizes a comparison of the resulting accident rates for regular, key, and dedicated trains. 

The overall mainline accident rates for all categories of accidents, as well as yard accident rates, for 

regular and key trains are the same. The overall mainline accident rate for dedicated trains is slightly less 

(about 3.8 percent) than the rates for key trains and regular trains. The overall yard accident rate for 

dedicated trains is significantly less (75 percent) than the rates for key and regular trains. The overall 

dedicated train accident rates for highway-rail crossing, other, and fire accidents are the same as for 

regular and key trains; however, dedicated train accident rates are lower for train-to-train collisions (about 

20 percent) and derailments (about 4.3 percent) than for key and regular trains. 

The rates of accidents that will exceed NRC compliance limits are the same for regular and key trains for 

fire and yard accidents. For all other categories of accidents that will exceed NRC compliance limits, 

dedicated and key trains will have a lower expected accident rate than for regular trains. The rate of trainto-train collisions that will exceed NRC compliance limits for dedicated and key trains is approximately 

50 percent less than for regular trains (key trains have a slightly higher rate than dedicated trains). The 

103
rate of derailments that will exceed NRC compliance limits for dedicated and key trains is about 23 

percent less and 19 percent less, respectively, than for regular trains. The rate of highway crossing 

accidents that will exceed NRC compliance limits for dedicated and key trains is approximately 19 

percent less than for regular trains. Similarly, the rate of other accidents that will exceed NRC 

compliance limits for dedicated and key trains is about 42 percent and 19 percent less, respectively, than 

for regular trains. 

Table 33. Regular versus Dedicated versus Key Train Results–Probability per Train Mile 

Probability per Train Mile (Main and Yard) 

Accident Type Regular Train 

Dedicated 

Train Key Train 

Mainline Accident Rate 2.03×10-06 1.96×10-06 2.03×10-06

Train-Train Collision 1.05×10-07 8.45×10-08 1.05×10-07

Category III Train-Train Collision 4.05×10-10 2.02×10-10 2.03×10-10

Derailment 1.36×10-06 1.30×10-06 1.36×10-06

Category III Derailment 9.52×10-08 7.37×10-08 7.70×10-08

Highway-Rail Crossing 3.01×10-07 3.01×10-07 3.01×10-07

Category III Highway-Rail Crossing Impact 3.38×10-09 2.74×10-09 2.74×10-09

Other 2.37×10-07 2.37×10-07 2.37×10-07

Other Category III Accidents 2.55×10-09 2.07×10-09 2.07×10-09

Fire 3.14×10-08 3.14×10-08 3.14×10-08

Category III Engulfing Fire Accident 4.20×10-15 4.66×10-16 4.20×10-15

Yard Accidents (per yard switching mile) 1.50×10-05 3.76×10-06 1.50×10-05

Category III Yard Accident 3.82×10-08 9.54×10-09 3.82×10-08 

3.7 Relative Accident Consequences 

3.7.1 Distribution of Accident Severities and Assessment of the Likelihood of Cask Damage 

The previous section distinguishes between the probability of an accident, given that one is either in a 

yard or on the mainline; the probability of a severe accident, given one or the other environments (as 

described by impact surfaces encountered and train velocity); and how those two distributions differ, 

depending upon the use of a dedicated versus regular or key train. 

Based upon the understanding of the resulting damage from impacts at different velocity ranges, the 

following accident severity categories were defined with respect to potential emission rates. 

• Category I Delay event–Accident well within the HAC modeled by the cask packaging test 

criteria of 10 CFR Part 71; dose rate assumed equivalent to the non-exclusive use 

transport rate of 10 mrem/hr at 3.3 ft (1 m) from the cask surface. Accidents in 

Category I could result in an increased duration of exposure to certain individuals 

(such as crew and nearby population) due to the extended time required to clear the 

wreck scene and to resume transport. 

104
• Category II Serious accident–An accident close to the HAC, which could result in a hundredfold 

increase in radiation levels, but no release of radioactive material occurs. The surface 

dose rate is assumed equal to 1 rem/hr (1,000 mrem/hr) at 3.3 ft (1 m) from the cask 

surface. 

• Category III Major accident–An accident that exceeds the HAC. A greater loss of shielding occurs 

but no release of radioactive material. The surface dose rate is assumed to be equal to 

4.3 rem/hr (4,300 mrem/hr) at 3.3 ft (1 m) from the cask surface. Accidents in 

Category III could expose populations to higher doses of radiation for extended time 

periods. 

• Category IV Severe accident–An accident well in excess of the regulatory compliance limit. A 

significant loss-of-shielding with the release of some radioactive material occurs. This 

category was not analyzed as it was considered equally unlikely for any of the rail 

shipping options, and the consequences would not be substantially different. 

3.7.2 LOS 

The possibility of particle releases from casks might be expected if impacts cause enough damage to force 

a seal to fail. However, strain to the exterior of the cask caused by a significant impact would more likely 

result in some LOS due to shifting of one of the interior layers of material (such as depleted uranium or 

lead) that provide external radiation shielding. Gamma shielding, lead in the case of the cask used in this 

analysis, is used to reduce external radiation doses to levels acceptable for transport. The presence and 

effectiveness of the shielding is subject to required testing during fabrication of the packaging. The 

shielding material usually performs no function other than shielding, and its presence is sufficient to 

satisfy this function. The shielding is usually enclosed by the inner and outer shells and, as a solid, is not 

subject to removal during normal conditions of transport. Under many accident conditions, the shielding 

remains in place and still performs the intended function. It is also possible, however, in an accident 

scenario to have impact forces or temperature conditions sufficient to cause lead slump, damage to the 

cask contents, or other conditions resulting in elevated radiation emission rates. The degradation of the 

lead shield reduces the effectiveness of the cask to perform its intended function. With spent-fuel casks, 

LOS is expected to be localized to a small fraction of the total surface area of the cask. In this case, 

although the contents of the cask are not directly exposed, at some locations on the cask surface, the level 

of radiation might exceed the normal transport level of 10 mrem per hour. Significant LOS can result 

from very high-speed impacts into soft surfaces and lower speed impacts into rigid surfaces. This LOS 

can result in a Category III accident, with dose rates ranging from the regulatory test allowable level of 

1,000 mrem per hour at 3.3 ft (1 m) (10 CFR 71.51), to 4,300 mrem per hour or above. The exact degree 

of LOS and resulting exposure would depend upon the impact velocity, angle, and hardness of the 

impacted surface. 

Sections 3.7.3 and 3.7.4 evaluate the potential consequences of hypothetical LOS incidents. Section 3.7.3

establishes the assumptions used for dose modeling, and Section 3.7.4 presents the findings. The analysis 

assumes that the only damage to the cask is to the shielding material (i.e., no seal leak or cask breach 

causing material release). 

3.7.3 LOS Incident Consequence Calculations 

The RADTRAN stop model was used to assess LOS incident consequences for the general population as 

well as emergency responders. The following sections discuss the input values used for the LOS 

modeling. 

105
3.7.3.1 Cask Dose Rate 

To evaluate LOS incidents, cask packages were constructed with the appropriate source strength to 

estimate the two dose rates that were analyzed for the subject cask, a single PWR fuel assembly in a steellead-steel rail cask with damaged lead shielding. The two dose rates analyzed were a 1 rem/hr (1,000 

mrem/hr) at 3.3 feet (1 m) dose rate (equivalent to the maximum regulatory (10 CFR 71.51) emission 

limit permissible for a cask to pass accident scenario acceptance testing) and a 4.3 rem/hr (4,300 

mrem/hr) at 3.3 ft (1 m) rate for a more severe hypothetical LOS incident. 

For real LOS accidents, cask orientation combined with shielding by the undamaged portions of the cask 

shell and also by nearby buildings would mean that radiation exposures would be limited by the view 

factor to the spent fuel through the damaged portions of the cask shell where shielding is compromised. 

Because the exact geometry of an accident cannot be predicted in advance, however, a point-source 

model and a uniformly distributed surrounding exposed population were used to calculate population 

dose. Accordingly, the estimates of the LOS accident dose risks should be somewhat conservative. 

3.7.3.2 Population Density 

General Population. Three LOS accident locations (urban, suburban, and rural) were evaluated. General 

population densities for these three locations were assumed to equal the mean of the respective population 

density distributions for the six routes, i.e., 5,477 persons/sq mi, 1,067 persons/sq mi, and 28 persons/sq 

mi (2,115 persons/sq km, 412 persons/sq km, and 11 persons/sq km), respectively (see Table 34). 

Population is modeled as being uniformly distributed around the source. 

Table 35 shows the predicted populations within the evacuated areas. Population densities were adjusted 

for the anticipated level of cordoning that would happen around the accident site. Note that these 

numbers include emergency responders working within the general population areas. 

Table 34. Average General Population Density for All Routes 

Average Population Density 

persons/sq mi (persons/sq km) 

Route Urban Suburban Rural 

1 6,237 (2,408) 1,164 (449) 26 (10) 

2 5,641 (2,178) 976 (377) 38 (15) 

3 5,169 (1,996) 1,006 (389) 26 (10) 

4 4,964 (1,917) 919 (355) 30 (12) 

5 6,109 (2,359) 1,028 (397) 28 (11) 

6 4,744 (1,832) 1,307 (505) 17 (7) 

Average 5,477 (2,115) 1,067 (412) 28 (11) 

Source: Census 2000. 

106
Table 35. General Population Densities for LOS Scenarios 

Population Density in persons/mi2

(persons/km2

) 

Location 

Annular Radii 

 Min.–Max. 

ft (m) Urban Suburban Rural 

Before 

Evacuation 49–2,625 (15-800) 5,477

(2,115) 

1,067

(412) 

28

(11) 

49-328 (15-100) 0* 0* 0* Urban, Rural, 

& Suburban After 

Evacuation 328-2,625 (100-800) 6,492 

(2,507) 

1,264 

(488) 

34 

(13) 

* Assumes 49-328 ft (15-100 m) area cordoned off–no general population access. 

Emergency Responders. In addition to the general population, this analysis considers the rail worker and 

emergency response populations. All railroads that handle shipments would have specific emergency 

response procedures to safely expedite recovery of shipments that are involved in a rail line accident. 

Continually manned railroad operation centers maintain the capability to contact personnel from a variety 

of resources that should provide appropriate equipment and manpower at the accident scene. A wide 

array of personnel would likely respond to such an incident: police and fire personnel, railroad personnel, 

wrecking contractors, railroad emergency response contractors, regulators, and shipper representatives. 

Rerailing the SNF train would likely require, at a minimum, lift capability and track repair personnel who 

would be required to work in close proximity to the cask. Table 36 shows the mix of personnel assumed 

for this analysis. 

Each incident is unique. Many unknowns exist, such as actual response times, capability and readiness, 

lift capability/availability/location, fire or involvement of other hazardous materials, accessibility to 

accident location, and site terrain. Each of these factors could change the mix of personnel and 

equipment required, as well as the duration of the event. 

3.7.3.3 Distance from Source 

The dose that could be received by a person decreases rapidly with distance from the cask and the highest 

doses are received at the points closest to the accident. Similarly dose decreases with lateral distance 

from the maximum dose point (centerline) at any distance. The following describes the distances from 

the source used in the calculation for total dose for the LOS incidents. 

General Population. The areas occupied by the general population were annular areas with a 49-ft (15 m) 

inner radius to 0.5-mile (0.8-km) outer radius. Table 35 shows the selected radii and population densities 

for the urban, suburban, and rural scenarios. 

Emergency Responders. For rail worker and emergency response personnel distances to the source will 

vary for each accident situation. Table 36 shows the distances used for this analysis. 

107
Table 36. LOS Emergency Response Personnel–Distance 

Distance from Source 

ft (m)

Population 

Number

of 

Persons 

Dedicated Regular/Key 

Lift 9* 9.8 (3) 9.8 (3) 

Track Repair 16 50 (15.2) 50 (15.2) 

2 300 (91.3) 2,140 (652.3) 

Fire/Police 2 98 (29.9) 98 (29.9) 

30 328.1 (100) 328 (100) 

6 32.8 (10) 32.8 (10) Regulators 12 328.1 (100) 328 (100) 

Crew 2 300 (91.2) 98 (652.3) 

Escorts 4 98 (29.3) 98 (29.3) 

*

 4 tractor operators, 4 groundsmen, 1 supervisor. 

3.7.3.4 Exposure Duration/Evacuation 

General Population. For the general population, the exposure duration begins at the time of the incident 

and ends when the train is underway again. For general population, dose estimates for 3- to 72-hour 

incident durations were analyzed to account for a range of incidents from a single car derailment to 

multiple car or locomotive derailments. 

In urban, suburban, and most rural areas where people could be exposed, emergency response actions will 

limit the chain of events through establishment of an exclusion zone around the accident site, thus 

reducing the amount of exposure. Because of evacuation/crowd control measures by first responders, the 

areas in which the highest dose could be received have a relatively small area. Locations very close to the 

accident site are unlikely to be occupied by people for any length of time after an accident. In the absence 

of specific information for this variable, 0.42 hours in urban areas and 0.67 hours in rural and suburban 

areas were the values used [DOE, 1995]. 

Emergency Responders. Table 37 shows exposure durations for emergency responders. Fire and police 

are assumed to be within 65.6 ft (20 m) of the cask for a 1⁄2-hour period for personnel injury response and 

then within 328 ft (100 m) for the duration of the LOS event. It was assumed that lift personnel would 

require 2-7 hours to rerail the derailed cars. An engineering estimate was made that, based on car 

derailments, a certain amount of track (360 ft (109.7 m) for dedicated trains and 480 ft (146.3 m) for 

regular/key trains) would require repair, and this is accomplished at a rate of 120 ft (36.6 m) per hour. 

These repair times were used to estimate the duration of exposure for track personnel. 

108
Table 37. LOS Emergency Response Personnel–Duration 

Duration 

(hours) 

Population 

Number 

of 

Persons 

Dedicated 

6-car train 

30-50 mph 

(48.2–80.4 km/hr) 

2 cars derailed 

360 ft (109.7 m) track damaged

Regular/Key 

70-car train 

30-50 mph 

(48.2–80.4 km/hr) 

7 cars derailed 

480 ft (146.3 m) track 

damaged

Lift 9* 2** 7***

Track Repair 16 33 43

2 0.5 0.5 

Fire/Police 2 0.5 0.5 

30 10 16 

6 1 1 Regulators 12 10 16 

Crew 2 0.5 0.5 

Escorts 4 0.5 0.5 

* 4 tractor operators, 4 groundsmen, 1 supervisor

** assumes 1 hour per derailed car *** assumes 1 hour per 120 ft (36.6 m) of 

damaged track led car

Total Duration 

10 Hours 

Total Duration 

16 Hours 

3.7.3.5 Shielding Factor 

General Population. The standard RADTRAN shielding factors (0.018, 0.87, and 1.0) for urban, 

suburban, and rural areas, respectively, were applied to the LOS scenarios. Table 38 shows these values. 

Emergency Responders. No shielding for emergency responders was considered (shielding factor = 1). 

109
Table 38. LOS General Population–Density, Duration, Distance, and Shielding 

Incident 

Duration 

(hours)

Incident 

Location 

Before/After 

Evacuation 

Duration 

of 

Exposure

(hours)

Population 

Density 

persons/mi2 

(persons/km2) 

Annular Radii 

 Min.–Max. 

ft (m) 

Shielding 

Factor 

Before 0.42 816.61 (2,115) 49-2,625 (15-800) 0.018 Urban 

After 2.58 967.96 (2,507) 328-2,625 (100-800) 0.018 

Before 0.67 159.07 (412) 49-2,625 (15-800) 0.87 

Suburban 

After 2.33 188.42 (488) 328-2,625 (100-800) 0.87 

Before 0.67 4.25 (11) 49-2,625 (15-800) 

3 

Rural 

After 2.33 5.02 (13) 328-2,625 (100-800) 

1 

1 

Before 0.42 816.61 (2,115) 49-2,625 (15-800) 0.018 Urban 

After 9.58 967.96 (2,507) 328-2,625 (100-800) 0.018 

Before 0.67 159.07 (412) 49-2,625 (15-800) 0.87 

Suburban 

After 9.33 188.42 (488) 328-2,625 (100-800) 0.87 

Before 0.67 4.25 (11) 49-2,625 (15-800) 

10 

Rural 

After 9.33 5.02 (13) 328-2,625 (100-800) 

1 

1 

Before 0.42 816.61 (2,115) 49-2,625 (15-800) 0.018 Urban 

After 23.58 967.96 (2,507) 328-2,625 (100-800) 0.018 

Before 0.67 159.07 (412) 49-2,625 (15-800) 0.87 

Suburban 

After 23.33 188.42 (488) 328-2,625 (100-800) 0.87 

Before 0.67 4.25 (11) 49-2,625 (15-800) 

24 

Rural 

After 23.33 5.02 (13) 328-2,625 (100-800) 

1 

1 

Before 0.42 816.61 (2,115) 49-2,625 (15-800) 0.018 Urban 

After 47.58 967.96 (2,507) 328-2,625 (100-800) 0.018 

Before 0.67 159.07 (412) 49-2,625 (15-800) 0.87 

Suburban 

After 47.33 188.42 (488) 328-2,625 (100-800) 0.87 

Before 0.67 4.25 (11) 49-2,625 (15-800) 

48 

Rural 

After 47.33 5.02 (13) 328-2,625 (100-800) 

1 

1 

Before 0.42 816.61 (2,115) 49-2,625 (15-800) 0.018 Urban 

After 71.58 967.96 (2,507) 328-2,625 (100-800) 0.018 

Before 0.67 159.07 (412) 49-2,625 (15-800) 0.87 

Suburban 

After 71.33 188.42 (488) 328-2,625 (100-800) 0.87 

Before 0.67 4.25 (11) 49-2,625 (15-800) 

72 

Rural After 71.33 5.02 (13) 328-2,625 (100-800) 

1 

1 

3.7.4 LOS Incident Results 

This section summarizes the results of the calculations for the radiological impacts for the two 

hypothetical LOS incidents during the transportation of SNF. The incidents were modeled using two cask 

dose rates–1,000 mrem/hr at 3.3 ft (1 m) and 4,300 mrem/hr at 3.3 ft (1 m). These scenarios correspond 

to the Category II and III accident severities. 

3.7.4.1 General Population 

Table 39 and Figure 41 show the general population dose for the Category II and Category III LOS 

incidents for three locations (urban, suburban, and rural) and for five exposure durations (3, 10, 24, 48, 

and 72 hours). Deleterious health effects ranging from minor to severe may arise from exposure of 

110
individuals and populations to ionizing radiation. These effects have been correlated to doses by the 

National Council on Radiological Protection and Measurement (NCRP), based on historical exposures 

and summarized in conversion factors that consider the probability of occurrence and a judgment of the 

severity of that effect [NCRP, 1993]. The NCRP LCF per person-rem conversion factor values used in 

this analysis for the estimated probabilities of a fatal cancer are 4.0×10-04 for workers and 5.0×10-04 for 

the public. 

Table 39. Range of Dose/LCF for General Population LOS Events 

Dose (person-rem) LCFs 

Severity 

Category Dose 

Duration 

(hours) Urban Suburban Rural Urban Suburban Rural 

3 4.32×10-03 4.26×10-02 1.30×10-03 2.16×10-06 2.13×10-05 6.52×10-07

10 1.36×10-02 0.130 3.98×10-03 6.80×10-06 6.48×10-05 1.99×10-06

24 3.22×10-02 0.305 9.33×10-03 1.61×10-05 1.52×10-04 4.67×10-06

48 6.40×10-02 0.605 1.85×10-02 3.20×10-05 3.02×10-04

Category 

II 

1,000 

mrem 

72 9.59×10-02 0.904 2.77×10-02 4.79×10-05 4.52×10-04

9.26×10-06

1.39×10-05

3 1.86×10-02 0.183 5.61×10-03 9.29×10-06 9.16×10-05 2.81×10-06

10 5.85×10-02 0.559 1.71×10-02 2.92×10-05 2.80×10-04 8.54×10-06

24 0.139 1.31 4.01×10-02 6.94×10-05 6.54×10-04 2.00×10-05

48 0.272 2.60 7.96×10-02 1.36×10-04 1.30×10-03

Category 

III 

4,300 

mrem 

72 0.412 3.89 0.119 2.06×10-04 1.94×10-03

3.98×10-05

5.94×10-05

Note: LCF rates for worker population: 0.0004 per person; for general population: 0.0005 per person (source: NCRP 

1993). 

LOS incident dose to the general population in suburban areas is higher than for urban populations despite 

the lesser population density because of the higher shielding factor for urban construction and faster 

evacuation rate for urban populations. 

3.7.4.2 Emergency Response Personnel 

The radiological impact on transportation workers and emergency responders for a SNF shipment is 

potentially much greater than for the general population. 

Table 40 shows the range of potential radiological impact on transportation workers and emergency 

response providers as the duration of the event increases. Single person dose rates for distances between 

3.3 ft (1 m) and 2,624.6 ft (800 m) are provided. As shown in Table 40 the dose received decreases 

sharply as distance increases and duration decreases. With no additional protection, a worker 196.8 ft (60 

m) from a 1,000 mrem/hr source, over a 10-hour period, would receive a dose of 9.00×10-03 rem, which 

corresponds to 3.60×10-06 LCF. 

111
Suburban

Urba

R

n

ural

4300 mrem

/ hr 3 Hours

4300 mrem

/ h r 10

hours

4300 mrem

/ h r 24

Hours

4300 mrem

/ h r 48

Hours

4300 mrem

/ h r 72

Hours

0.18

0.02

0.01

0.56

0.06

0.02

1.31

0.14

0.04

2.60

0.27

0.08

3.89

0.41

0.12

0.00E+00

5.00E-01

1.00E+00

1.50E+00

2.00E+00

2.50E+00

3.00E+00

3.50E+00

4.00E+00

(Package Dose Rate: 4,300 mrem e/hr at 1 meter)

Suburban

Urba

R

n

ural

1000 mrem

/ h r 3 Hours

1000 mrem

/ h r 10

hours

1000 mrem

/ h r 24

Hours

1000 mrem

/ h r 48

Hours

1000 mrem

/ h r 72

Hours

4.26E-02

4.32E-03

1.30E-03

0.13

0.01

3.98E-03

0.30

0.03

0.01

0.60

0.06

0.02

0.90

0.10

0.03

0.00E+00

5.00E-01

1.00E+00

LOS Dose to General Population

(Package Dose Rate: 1,000 m reme/hr at 1 m eter) (Package Dose Rate: 1,000 mrem/hr at 1 meter)

(Package Dose Rate: 4,300 mrem/hr at 1 meter) 

Figure 41. LOS Dose to General Population–Category II and III Events 

112
Table 40. Range of Dose for Rail Worker/Emergency Responder–Single Person Dose (rem)–

Category II LOS Event 

Incident Duration (hours) Distance From 

Source 

ft (m) 3 10 24 48 72 

3.3 (1) 4.50 15.0 36.0 72.0 108.0 

16.4 (5) 0.270 0.900 2.16 4.32 6.48 

32.8 (10) 6.75×10-02 0.225 0.540 1.08 1.62 

65.6 (20) 1.69×10-02 5.62×10-02 0.135 0.270 0.405 

98.4 (30) 7.50×10-03 2.50×10-02 6.00×10-02 0.120 0.180 

131.2 (40) 4.22×10-03 1.41×10-02 3.38×10-02 6.75×10-02 0.101 

196.8 (60) 2.70×10-03 9.00×10-03 2.16×10-02 4.32×10-02 6.48×10-02

328 (100) 6.75×10-04 2.25×10-03 5.40×10-03 1.08×10-02 1.62×10-02

656.1 (200) 1.69×10-04 5.62×10-04 1.35×10-03 2.70×10-03 4.05×10-03

984.2 (300) 7.50×10-05 2.50×10-04 6.00×10-04 1.20×10-03 1.80×10-03

1,312.3 (400) 4.22×10-05 1.41×10-04 3.38×10-04 6.75×10-04 1.01×10-03

1,968.5 (600) 1.88×10-05 6.25×10-05 1.50×10-04 3.00×10-04 4.50×10-04

2,624.6 (800) 1.05×10-05 3.52×10-05 8.44×10-05 1.69×10-04 2.53×10-04

Note: Assumes a shielding factor of 1 (no shielding). 

Table 41 and Figure 42 show the consequences to emergency response personnel and the general public 

for the two hypothetical LOS events of severity Categories II and III. 

Table 41. LOS Incident Consequences for Hypothetical Category II and III Events 

Total Dose (person-rem)

Category II Category III 

Population 

Dedicated 

10-Hour Event

Regular/Key 

16- Hour Event

Dedicated 

10- Hour Event

Regular/Key 

16- Hour Event 

Lift 4.50E+00 1.58E+01 1.94E+01 6.77E+01 

Track Repair 4.32E-02 5.76E-02 1.86E-01 2.48E-01 

Fire/Police 7.04E-02 1.11E-01 3.02E-01 4.75E-01 

Regulators 1.62E-01 1.78E-01 6.97E-01 7.67E-01 

Crew 2.70E-04 5.29E-06 1.16E-03 2.27E-05 

Escorts 5.25E-03 5.25E-03 2.26E-02 2.26E-02 

General Population 

(Suburban) 1.30E-01 2.05E-01 5.59E-01 8.81E-01 

Total 4.9 16.4 21.2 70.1 

113
Total Dose for Category II and III LOS Events

16.4

70.1

4.9

21.2

0

10

20

30

40

50

60

70

80

Dedicated Regular/Key Dedicated Regular/Key 

Category II Category III

Dose (person-rem)

Figure 42. Total Dose for Category II and III LOS Events 

Although it is difficult to predict the duration of an incident, since regular/key train service involves many 

more cars in the consist and the consist may contain other hazardous materials which could be involved in 

a fire, it is likely that an incident in regular/key train service will result in longer event durations than for 

the same incident in dedicated train service. 

3.7.5 Comparison of Delay and LOS Incident Consequences 

In addition to the LOS incidents evaluated above, elevated doses would also be experienced when SNF 

shipments with normal emission rate levels are delayed enroute or are involved in accidents with no LOS. 

This case was evaluated for situations where minor incidents or situations involving another train or piece 

of railroad equipment resulted in a significant delay for the cask-carrying train. 

Figure 43 shows doses to crew, escorts, and the general population for a 10-hour delay event. The only 

distinction between train services is the crew dose, which is lower for regular/key trains due to the 

position of the crew relative to the cask. 

114
Dose - 10 Hour Delay

2.71E-04

5.26E-03

1.03E-03

5.31E-06

5.26E-03

1.03E-03

0.00E+00

2.10E-03

4.20E-03

6.30E-03

Crew Escort General

Population

(Suburban)

Crew Escort General

Population

(Suburban)

Dedicated Regular / Key

10 Hours

Dose (person-rem)

Figure 43. Dose–10-Hour Delay 

Figure 44 shows the relative doses to the general population, rail crew, and escorts for a 10-hour delay 

event with an emission rate of 10 mrem/hr at 3.3 ft (1 m). Figure 44 also shows doses for Category II and 

III level LOS incidents with emission rates of 1,000 and 4,300 mrem/hr at 3.3 ft (1 m) for general 

population, rail workers, and emergency response personnel. This comparison assumes the level of 

response for the LOS incidents discussed in Tables 36, 37, and 38. The complement of workers and 

responders used is 9 lift personnel, 16 track repair, 34 fire/police, 18 regulators, 2 train crew, and 4 

escorts. The data presented also include general population exposure. 

Figure 44 illustrates the extent to which elevated emmision rates substantially increase the overall 

exposure. The Category II and III LOS doses are much higher than for the delay incident. All cases are 

considerably higher than the incident-free doses discussed in Chapter 2. Suburban incidents result in the 

most exposure because of the shielding factors. The relative safety of dedicated train service is based on 

reduced probability not consequence. 

115
6.56E-03

6.30E-03

4.91

16.36

21.17

70.09

0

10

20

30

40

50

60

70

80

Dose (person-rem)

Dedicated

(10 hours)

Regular/

 Key 

(10 hours)

Dedicated

(10 hours)

Regular/

 Key 

(16 hours)

Dedicated

(10 hours)

Regular/

 Key 

(16 hours)

Category I Category II Category III 

Delay LOS

Suburban

Figure 44. Total Dose for Category I, II, and III Events 

The radiological consequences of three types of events summarized in Table 42 and Figure 44 are 

provided to show the difference in the radiation dose for accidents of varying severity. 

The analyses of the severity of accidents for higher speeds and longer train lengths indicated that the 

duration of similar events at identical impacts were likely to differ. Emergency response and overall 

response time are likely to be longer when more rail cars are derailed or hazmat is present in a consist. 

Therefore, the consequences of these events has been scaled to reflect the typical response time for a 

dedicated (6-car) train versus a regular (70-car) train (see Table 42). Since exposure duration is critical in 

the calculation of overall consequences, the results for a shorter train in an equally severe event are lower. 

Finally, the comparative risk of accident consequences for dedicated or regular/key train service is 

expressed as the expected number of LCFs resulting from accidents of Category I, II, and III severity. 

Table 42 shows the result of this comparison. The expected number of LCFs for regular/key and 

dedicated trains given an accident of Category I severity (10 mrem per hour) are nearly equal, 2.62×10-6

and 2.73×10-6, respectively. For Category II (1,000 mrem per hour) and III (4,300 mrem per hour) 

accidents, however, the expected LCFs for dedicated trains are approximately 70 percent less than for 

regular/key trains, 1.98×10-3 versus 6.56×10-3 and 8.52×10-3 versus 2.81×10-2, respectively. 

116
Table 42. Summary of LCF Consequences–Delay/LOS Incidents 

Regular/Key Train Dedicated Train 

Event 

Total Event 

Duration 

(hours) 

Total Dose–

All 

Populations

(person-rem)

Predicted 

LCF 

Total Dose–

All 

Populations 

(person-rem) 

Predicted 

LCF 

Category 

I 

Delay 

(No LOS) 

10 mrem per 

hr 

10 6.30×10-03 2.62×10-06 6.56×10-03 2.73×10-06

Category 

II 

Regulatory 

Equivalent 

Impact–LOS 

1,000 mrem 

per hr 

10 

Dedicated 

16 

Regular/Key

16.36 6.56×10-03 4.91 1.98×10-03

Category 

III 

Hypothetical 

LOS 

4,300 mrem 

per hr 

10 

Dedicated 

16 

Regular/Key

70.09 2.81×10-02 21.17 8.52×10-03

Category 

IV 

Potential 

Release 

Not 

Evaluated 

The delay event has no emergency response component. 

117
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118
4. Conclusions 

The report considers the risks to the general public and workers for incident-free transport and accidentrelated radiological exposure for regular, dedicated, and key trains. 

4.1 Incident-Free Radiological Risk 

The incident-free exposures calculated for regular, dedicated, and key train service are very low for the 

general public and other impacted populations along specific train routes. These exposures were 

calculated assuming that no accident of any type occurs during shipment, and the dose rate to which 

populations are exposed is the maximum allowable cask emission radiation (10 mrem per hour measured 

at 3.3 ft (1 m) from the package surface) that results during shipment. The maximum individual exposure 

is approximately equal to the exposure received in 2 seconds during a typical 4-hour jet flight. 

The maximum expected dose to an individual in the general public for one incident-free shipment is about 

4.32×10-04 mrem, which is four orders of magnitude below a typical exposure from a 4-hour airline flight 

of 3 mrem. The number of expected additional cancer fatalities from 10,000 incident-free shipments on 

the longest route is approximately 0.22 for regular/key trains compared to 0.18 for dedicated trains. The 

movement campaign to Yucca Mountain is expected to generate somewhere between 11,000 and 17,000 

shipments of SNF and HLRW. The general public radiological exposure would result in less than one 

expected additional cancer fatality over the entire shipping campaign. 

Individual crew doses for the duration of a single shipment are expected to range between 1.98×10-01 to 

8.08 ×10-01 mrem for dedicated trains, and between 5.83×10-03 and 1.62×10-02 mrem for regular/key trains. 

Although the rail worker exposures and the LCFs are higher than those for the general population, the 

expected additional cancer rates are very low. For example, the average number of worker LCFs for 

Route 1 across all service types and speeds is 3.22×10-05 per shipment versus 1.43×10-05 for the general 

public. These numbers translate into one LCF for workers per approximately 31,073 shipments, versus 

one LCF per member of the public per 70,172 shipments. 

Exposure time is the determining factor in the amount of radiation members of a population group 

receive. The exposure time was determined by train speed, whether run-through operations are allowed, 

and the number of stops required at yards or sidings. The speed restrictions on the dedicated and key 

trains increase in-transit exposure time when compared to regular trains. As seen by the results presented 

above, methods of shipment that minimize stop times and total transit times can minimize exposure. 

4.2 Accident Analysis 

An event tree analysis was used to estimate the difference in accident probability between regular, 

dedicated, and key trains, and the likelihood that a regular, dedicated, and key train would be involved in 

an extra-regulatory accident. As shown in Table 43 and Figure 45, the overall accident rate expected for 

all service types is about two accidents per million train miles or about one accident for every 160 trips on 

the longest route. Most train accidents are minor and of little consequence. Only a major accident 

involves enough energy to damage a cask. For the purposes of this report, accidents were broken down 

into four severity categories: 

• Category I Delay event. Benign accident well below the regulatory compliance limit; dose rate 

assumed equivalent to the transport rate of 10 mrem/hr at 3.3 ft (1 m). Accidents in 

Category I result in an increased duration of exposure to certain individuals (such as 

crew and nearby population) due to the extended time required clearing the wreck. 

119
• Category II Minor accident. An accident close to the regulatory compliance limit where some 

LOS or internal damage has occurred but no release. An increase in the surface dose 

rate occurs. The surface dose rate is assumed equal to 1 rem/hr (1,000 mrem/hr) at 3.3 

ft (1 m). Accidents in Category II expose populations to higher doses of radiation for 

extended time periods. 

• Category III Major accident. An accident that generates forces or temperatures that exceed the 

regulatory compliance limits. A greater LOS or internal damage occurs but no release 

of radioactive material. The surface dose rate is assumed to be equal to 4.3 rem/hr 

(4,300 mrem/hr) at 3.3 ft (1 m). Accidents in Category III expose populations to 

higher doses of radiation for extended time periods. 

• Category IV Severe accident. An accident well in excess of the regulatory compliance limit. A 

significant LOS or cask damage with the release of some radioactive material occurs. 

This category was not analyzed. 

The consequences of any of these four types of accidents are determined by the environment in which the 

accident occurred; the potential for a second event such as a fire following the initial impact, puncture, or 

fall; and the time required to respond to the accident. 

4.2.1 Accident Probability 

Train accidents are rare events, and operational and maintenance procedures can make them rarer. 

The imposition of a speed restriction for dedicated and key trains was conservatively assumed not to 

reduce overall accident probability. The overall accident rate is affected by: (1) the environments in 

which the trains operate (yards, sidings, or mainline); (2) the duration of yard entries and whether 

classification activities are required; (3) whether other trains pass the cask-carrying train; and (4) how the 

train consist length and makeup affect its handling and derailment probability. Speed restrictions were 

assumed, however, to reduce the likelihood of accidents at high speeds (greater than 50 mph (80.4 

km/hr)) and thus the severity of such accidents. 

The estimated effect of imposing passing restrictions and shorter train consists is to reduce the overall 

mainline train accident rate from approximately 2.03×10-06 per train mile for regular and key trains to 

1.96×10-06 per train mile for dedicated trains. Due to the reduction of time spent in yards by dedicated 

trains, it is assumed that there would be a larger reduction in expected accidents in yards will occur (from 

1.50×10-05 to 3.76×10-06 per yard mile) compared to regular and key trains. 

Table 43 illustrates that the train-to-train collision probability for regular trains overall is about 1.05×10-07

per train mile, and the adjusted probability (when raking collisions are reduced due to the no-pass rule) 

for dedicated trains is approximately 8.45×10-08 per train mile. The expected collision probability of key 

trains is equal to that of regular trains because no passing restrictions are assumed to apply to key train 

operations. The effect of operational restrictions and consist limitations for dedicated and key trains on 

Category III accident probability is illustrated in Figure and Table 43 for collisions and other types of 

accidents. In this figure, the relative risk contribution of each type of train service is expressed in 

accidents per million train miles. If regular train service is used, the probability that a train-to-train 

collision results in a Category III event is 4.05×10-10 per train mile or 0.4 accidents per billion train miles, 

based upon its allowable higher speeds. Since dedicated trains are assumed to operate at speeds below 50 

mph (80.46 km/hr), the probability that a dedicated train will be involved in a Category III collision is 

2.02×10-10 per train mile. The corresponding probability for key train Category III collisions is similar to 

dedicated trains but slightly higher, 2.03×10-10 per train mile, because the raking collisions are included. 

120
Table 43. Comparison of Accident Rates for Regular, Dedicated, and Key Trains 

Probability per Train Mile (Main and 

Yard) Accident Type 

Regular Train Dedicated 

Train Key Train 

Mainline Accident Rate 2.03×10-06 1.96×10-06 2.03×10-06

Train-Train Collision 1.05×10-07 8.45×10-08 1.05×10-07

Train-Train Collision at Greater than NRC Cask 

Certification Equivalent Velocity (Category III) 4.05×10-10 2.02×10-10 2.03×10-10

Derailment 1.36×10-06 1.30×10-06 1.36×10-06

Derailment at Greater than NRC Cask Certification 

Equivalent Velocity (Category III) 9.52×10-08 7.37×10-08 7.70×10-08

Highway-Rail Crossing 3.01×10-07 3.01×10-07 3.01×10-07

Highway-Rail Crossing Impact at Greater than NRC Cask 

Certification Equivalent Velocity (Category III) 3.38×10-09 2.74×10-09 2.74×10-09

Other 2.37×10-07 2.37×10-07 2.37×10-07

Other Accidents at Greater than NRC Cask Certification 

Equivalent Velocity (Category III) 2.55×10-09 2.07×10-09 2.07×10-09

Fire 3.14×10-08 3.14×10-08 3.14×10-08

Engulfing Fire at Greater than NRC Cask Certification 

Compliance Duration and Intensity (Category III) 4.20×10-15 4.66×10-16 4.20×10-15

Yard Accidents (per yard switching mile) 1.50×10-05 3.76×10-06 1.50×10-05

Yard Accident at Greater than NRC Cask Certification 

Equivalent Velocity (Category III) 3.82×10-08 9.54×10-09 3.82×10-08 

The use of dedicated trains results in an overall reduction in the derailment rate (compared to regular 

trains) per train mile from 1.36×10-06 to 1.30×10-06 (see Table 43). Key trains are assumed to have the 

same derailment rate as regular trains since they are equally subject to train make-up- and handlingcaused derailments. 

The influence of restricting the speeds of dedicated trains is to reduce the probability that a high-speed 

derailment occurs resulting in a Category III accident from 9.52×10-08 to 7.37×10-08 per train mile. Key 

trains will have a similar, but slightly higher, probability of Category III derailments, 7.70×10-08 per train 

mile (see Figure 46), since key trains are more subject to train makeup and handling derailments than 

dedicated trains. 

High-temperature fires are extremely rare events in railroading, but they do occur. Compared to regular 

trains, dedicated trains reduce the likelihood of high-temperature fires resulting from exposure to highly 

flammable hazardous material in the consist of the train, as well as reduce the likelihood of involvement 

in a fire during yard entries or classification activity in yards. Dedicated trains would reduce the 

likelihood that the cask might be involved in a severe, fully engulfing fire that results in a Category III 

event from 4.20×10-15 to 4.66×10-16 per train mile or from about once in 20 billion trips to about once in 

200 billion trips on the longest route (see Figure 46). Since the specific definition of key train operations 

imposes no restrictions upon other allowable materials in the consist, such as flammable hazardous 

materials, and no explicit restrictions regarding the number or duration of yard entries (other than the 

normal operations of a regular train), the fire probability for a key train is assumed to be equal to that of a 

regular train. 

121
2.03

15.03

1.96

3.76

15.03

2.03

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

Mainline Accident Rate Yard Accident Rate

Accident Rate per Million Train Miles

Regular

Dedicated

Key Train 

Figure 45. Comparative Risk per Million Train Miles of Regular, Dedicated, 

and Key Trains by Mainline and Yard Accident Rates 3.38E-03

4.05E-04

2.55E-03

4.20E-09

2.74E-03

2.02E-04

4.66E-10

2.07E-03

2.03E-04

2.74E-03

2.07E-03

4.20E-09

0.00E+00

5.00E-04

1.00E-03

1.50E-03

2.00E-03

2.50E-03

3.00E-03

3.50E-03

4.00E-03

Collision > NRC

Compliance

Highway-Rail Grade

Crossing > NRC

Compliance

Other > NRC

Compliance

Fire > NRC

Compliance

Accident Type

Accident Rate per Million Train Miles

0.10

0.07

0.08

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

Derailment > NRC Regulatory

Compliance

Regular Dedicated Key Train 

Figure 46. Comparative Risk per Million Train Miles of 

Regular, Dedicated, and Key Trains by Accident Type 

In the case of highway crossing and other accidents (not collisions or derailments), the interventions 

associated with dedicated or key trains were not expected to make a difference in overall accident 

probability (see Table 43). The reduced speeds of dedicated and key trains, however, will reduce the 

probability of Category III highway grade crossing and other accidents. 

122
4.2.2 Accident Consequences 

Of the four accident categories, consequences were evaluated for the first three: incidents where a delay 

is caused but no elevated emission level results, and two levels of incidents where the radiation protection 

provided by the cask is compromised due to an accident. The report describes the likely doses to general 

population, workers, and emergency response personnel for a 10-hour delay incident with an emission 

rate of 10 mrem/hr at 3.3 ft (1 m) and for two incidents with emission rates of 1,000 and 4,300 mrem/hr at 

3.3 ft (1 m) lasting between 3 and 72 hours. The probability of a Category IV accident was considered 

remote for any of the methods of transport considered, and the consequences would not vary with 

shipment choice so the case was not directly studied. 

Elevated emission rates resulting from either scenario substantially increase the overall exposure. The 

Category II and III scenario exposures are much higher than for the delay incident. All cases are 

considerably higher than the incident-free exposures developed in this study. Individual doses for the 10-

hour Category II accident could be 0.5 rem for dedicated trains and 1.8 rem for regular/key trains. The 

maximum allowable annual occupational, whole-body dose for an individual by Occupational Safety and 

Health Administration (OSHA) standards is 5 rem [20 CFR 1910.1096-OSHA/10 CFR 20.1201-NRC]. 

Since a single individual could receive a substantial portion of the annual allowable dose in the time 

necessary to respond to the Category III accident, it is possible that personnel time rotation, distancing, 

and radiation protection measures may need to be taken to limit any one individual’s exposure to an 

acceptable level. 

Using a very conservative assumption to calculate crew exposure, for each case the exposure for the 

dedicated train service is higher than for regular and key train service for an equal duration, due primarily 

to the relative location of the crew to the cask. (Although train crews do not participate in the accident 

response and would not stay with the train for the duration of the accident response, they may require 

rescue after an accident.) 

Overall, the time required to resolve/remediate dedicated train incidents is expected to be substantially 

shorter than those required for regular or key train incidents, due to such complicating factors as length of 

the consist and other cargo that might be on the regular or key train. Suburban incidents result in the most 

exposure because of their relatively high populations and the moderate radiation shielding that woodframe construction provides. 

4.3 Summary 

This study has examined the risk of radiological exposure resulting from transport of SNF and HLRW 

using three alternative rail shipment methods. Incident-free risk for shipment by all three methods would 

result in very low additional population exposures. Dedicated trains would produce lower exposures 

when compared to regular trains or key trains, with the exception of crew and escort doses. This is due to 

the assumed position of the car in the consist relative to the crews in each type of train service. These 

doses are very low and fall substantially below the typical dose an individual receives during a 4-hour 

airline flight. 

The two most significant accident threats considered in the analysis are: (1) the potential for high-speed 

collisions and derailments that could result in a high-speed cask impact with a hard surface and (2) the 

potential for long duration high-temperature fires resulting from exposure to other hazmat on a train 

consist or in a yard. The risks associated with high-speed derailments are very small, and the likelihood 

of a long-duration, high-temperature fire are extremely small. Nevertheless, the speed restrictions 

associated with the use of dedicated and key trains is expected to reduce high-speed accident probability 

(compared to regular trains). Reduction of yard entries also substantially reduces the expected accident 

rate for dedicated trains, compared to regular or key trains. 

123
Analysis of the location and pattern of accident occurrences indicated that it is best to evaluate each of the 

potential operational restrictions in light of route-specific factors that may contribute to increases (or 

decreases) of a particular type of risk. In this report’s example, between Humboldt, CA, and Yucca 

Mountain, NV, the highest frequency of accidents occurred in mountainous territory and within yard 

limits. The use of a dedicated train could allow the railroad to avoid classification yard entries and 

impose restrictions, such as the no-passing rule in territory that may be operationally challenging. 

Based upon analyses of the typical number of cars involved in derailments and the possibility that other 

hazmat may be included in the consists of regular or key trains, the duration of the incidents involving 

dedicated trains are likely to be much shorter than those of regular or key trains. The duration of the 

event determines the amount of radiological exposure to surrounding population and responders. When 

duration is included, the result shows that dedicated trains reduce the potential exposure when compared 

to regular or key trains. The expected number of LCFs for either case is very small. Given a Category II 

accident event (1,000 mrem per hr at 1 m), the expected number of LCFs for regular/key trains is 

6.56×10-03 compared to 1.98×10-03 for dedicated trains. 

The shipment of SNF and HLRW by any of the methods analyzed presents a very small risk to the 

general public and workers even when considering major accident scenarios (Category III). Operational 

restrictions can reduce the likelihood of even the rarest of events. Dedicated trains are not required to 

implement most of the operational restrictions described above; with the exception of elimination or 

reduction of classification yard entries, all other operational restrictions analyzed in this study could, 

potentially, be required of regular or key trains. The shipment of SNF and HLRW in trains with longer 

consists, however, poses other operational concerns for the railroads. On long routes where multiple 

stops in yards would be required, use of a dedicated train would expedite shipment and allow the carrier 

much more discretion in routing the train and choosing the operating speed. 

124
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130 
Appendix A. 

AAR Circular OT-55-D - Recommended Practices for Transportation of 

Hazardous Materials 

ASSOCIATION 

OF AMERICAN 

RAILROADS 

P. G. Kinnecom 

Executive Director - Tank Car Safety 

August 30, 2001 

CIRCULAR NO. OT-55-D 

(CPC-1126) 

SUBJECT: Recommended Railroad Operating Practices for Transportation of Hazardous Materials 

TO MEMBERS AND PRIVATE CAR OWNERS: 

Based on recommendations of the Inter-Industry Task Force on the Safe Transportation of 

Hazardous Materials by Rail, AAR published Circular No. OT-55 on January 4, 1990 to document 

recommended railroad operating practices for the transportation of hazardous materials. The circular 

included recommended road and yard operating practices, designation of key routes, proposed separations 

from hazmat storage areas, training of transportation employees, and implementation of TRANSCAER®, 

a national community outreach program to improve community awareness, emergency planning and 

incident response for the transportation of hazardous materials. 

Circular No. OT-55 has been modified to revision D dated 8/23/2001 (copy attached). Circular 

No. OT-55-D incorporates the transportation of spent nuclear fuel and high level radioactive waste, and 

updates the list of PIH materials and environmentally sensitive chemicals that are subject to OT-55. 

A copy of Circular No. OT-55-D, Recommended Railroad Operating Practices for 

Transportation of Hazardous Materials, is attached for your reference and use. 

Sincerely, 

P. G. Kinnecom 

Safety and Operations 

50 F Street, N.W., Washington, D.C. 20001-1564 

Phone (202) 639-2147; FAX (202) 639-2930; e-mail pkinnecom@aar.org

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ASSOCIATION 

OF AMERICAN 

RAILROADS 

C. E. Dettmann 

Executive Vice President 

Safety and Operations 

August 23, 2001 

Circular No. OT-55-D 

Recommended Railroad Operating Practices For Transportation of Hazardous Materials

Chief Operating Officers: 

Based on recommendations of the AAR Hazardous Materials (BOE) Committee, the Safety and Operations 

Management Committee, on August 23, 2001, approved the following revised recommended operating practices for 

the transportation of hazardous materials. They are effective August 23, 2001. 

Road Operating Practices

I. "Key Trains"

A. Definition: Any train with five tank car loads of Poison Inhalation Hazard (Hazard Zone A or B) 

or 20 car loads or intermodal portable tank loads of a combination of PIH (Hazard Zone A or B), 

flammable gas, Class 1.1 or 1.2 explosives, and environmentally sensitive chemicals, or one or 

more car loads of spent nuclear fuel (SNF) or high level radioactive waste (HLRW) shall be called 

a "Key Train". Attached as Appendix A is a list of PIH (Hazard zone A or B) and environmentally 

sensitive chemicals with 49 Hazmat Codes. 

B. Restrictions: 

1. Maximum speed -- "Key Train" - 50 MPH. 

2. Unless siding or auxiliary track meets FRA Class 2 standards, a Key Train will hold main 

track at meeting or passing points, when practicable. 

3. Only cars equipped with roller bearings will be allowed in a Key Train. 

4. If a defect in a "Key Train" bearing is reported by a wayside detector, but a visual 

inspection fails to confirm evidence of a defect, the train will not exceed 30 MPH until it 

has passed over the next wayside detector or delivered to a terminal for a mechanical 

inspection. If the same car again sets off the next detector or is found to be defective, it 

must be set out from the train. 

II. Designation of "Key Routes"

A. Definition: Any track with a combination of 10,000 car loads or intermodal portable tank loads of 

hazardous materials, or a combination of 4,000 car loadings of PIH (Hazard zone A or B), 

flammable gas, Class 1.1 or 1.2 explosives, environmentally sensitive chemicals, spent nuclear 

fuel (SNF) or high level radioactive waste (HLRW) over a period of one year. 

A-3 
B. Requirements: 

1. Wayside defective bearing detectors shall be placed at a maximum of 40 miles apart on 

"Key Routes,” or equivalent level of protection may be installed based on improvements 

in technology. 

2. Main Track on "Key Routes" is inspected by rail defect detection and track geometry 

inspection cars or any equivalent level of inspection no less than two times each year; and 

sidings are similarly inspected no less than one time each year. 

3. Any track used for meeting and passing "Key Trains" must be Class 2 or higher. If a meet 

or pass must occur on less than Class 2 track due to an emergency, one of the trains must 

be stopped before the other train passes. 

III. Yard Operating Practices

A. Maximum reasonable efforts will be made to achieve coupling of loaded placarded tank cars at 

speeds not to exceed 4 MPH. 

B. Loaded placarded tank cars of PIH (Hazard zone A or B) or flammable gas which are cut off in 

motion for coupling must be handled in not more than 2-car cuts; and cars cut off in motion to be 

coupled directly to a loaded placarded tank car of PIH (Hazard zone A or B) or flammable gas must 

also be handled on not more than 2-car cuts. 

IV. Storage

Separation Distance for New Facilities 

Loaded Tank Cars and Storage Tanks from Mainline Class II Track or Higher 

Activity PIH (Zone A or B), Class 3, 

Division 2.1, Division 2.2 and all 

other Hazard Classes 

Combustible Liquids, 

Class 8, and Class 9 

Loading and Unloading 100 FEET 50 FEET

Storage of Loaded Tank 

Cars

50 FEET 25 FEET

Storage in Tanks 100 FEET 50 FEET

Note 1 - With regard to existing facilities, maximum reasonable effort should be made to conform to this 

standard taking into consideration cost, physical and legal constraints. 

Note 2 - The proposals apply to storage on railroad property and on chemical company property located 

close to railroad mainline. 

V. TRANSCAER® (Transportation Community Awareness and Emergency Response Implementation of 

Transcaer®) 

Railroads will assist in implementing TRANSCAER®, a system-wide community outreach program to 

improve community awareness, emergency planning and incident response for the transportation of hazardous 

materials. Objectives of TRANSCAER® are as follows: 

• Demonstrate the continuing commitment of chemical manufacturers and transporters to the safe 

transportation of hazardous materials; 

A-4 
• Improve the relationship between manufacturers, carriers and local officials of communities through 

which hazardous materials are transported; 

• Inform Local Emergency Planning Committees (LEPC's) about hazardous materials moving through 

their communities and the safeguards that are in place to protect against unintentional releases; 

• Assist LEPC's in developing emergency plans to cope with hazardous materials transportation 

incidents; 

• Assist community response organizations in preparations for responding to hazardous materials 

incidents. 

TRANSCAER® activities are also addressed in the Distribution Code of the American Chemistry Council’s 

Responsible Care® program. Many members have joined the Responsible Care® Partnership Program to help 

describe and improve their ongoing safety, health and environmental programs. 

An important product of the TRANSCAER® program will be to overcome the widespread belief that every 

local firefighter and policeman must have the expert skills and equipment to respond personally to any hazardous 

materials emergency. Through the awareness training and contingency planning provided through TRANSCAER®, 

states and local communities will be able to pool their expertise and resources with those of industry to provide for a 

more coordinated and better managed emergency response system. 

TRANSCAER® should be highly publicized to produce the maximum desirable enhancement of public 

awareness. 

VI. Criteria for Shipper Notification

The railroads will initiate the shipper's emergency response system by calling CHEMTREC, or the 

appropriate contact telephone number as required by regulation on the shipping document, when an incident occurs 

involving any car (load or residue) containing a hazardous material regulated in transportation by the Department of 

Transportation. 

An incident is defined as a rail car which is derailed and not upright, or which has sustained body or tank 

shell damage, or has sustained a release of any amount of product. 

The shipper's emergency response system should also be initiated if the carrier believes there is reason to 

suspect any other potential for injury to people, property or the environment. 

In the event of a major rail accident, a consist (to include shipper, consignee and commodity description for 

each hazardous material), waybill or equivalent document, should be provided to CHEMTREC or the appropriate 

shipper contact as identified by the emergency response telephone number displayed on the shipping document. 

This can be accomplished by facsimile or other appropriate and acceptable electronic means. 

A major rail accident is defined as one resulting in fire, explosion, the potential for an explosion, fatalities, 

evacuation of the general public, or multiple releases of hazardous materials. 

Anytime a consist or other document is provided to CHEMTREC or the appropriate contact a follow-up 

call by the carrier should be made to confirm the receipt of the information as well as to provide other additional 

information pertaining to the incident not contained in the facsimile or electronically transmitted document. 

This practice does not preclude any carrier from notifying CHEMTREC or the appropriate shipper contact 

of a rail incident involving hazardous materials that does not meet the criteria outlined above. 

A-5 
VII. Time Sensitive Materials

Railroads and shippers will be responsible for monitoring the shipments (loads & residue) of products 

classified by the Department of Transportation as being time sensitive. 

This monitoring process will, at a minimum, provide a means to ensure the movement of rail cars 

containing time sensitive materials in order to achieve delivery of the product within the time specified by the 

Department of Transportation. 

As warranted, railroads will implement an internal escalation process and communicate with shippers, 

receivers and other rail carriers concerning any rail car containing a time sensitive product that has been delayed in 

transit to the extent that it may not reach destination within the time specified by the Department of Transportation. 

In such cases, an expedited movement of the rail car, or other action as deemed appropriate by the carrier and 

shipper will be taken. 

Each AAR member will commit without reservation to comply with these recommendations/standards on 

its operations within the United States of America. 

On behalf of the Safety and Operations Management Committee. 

Very truly yours, 

Original signed by: 

C. E. Dettmann 

Attachment 

Supersedes Circular No. OT-55-C dated October 20, 2000. 

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Appendix A to 

Circular OT-55-D 

August 23, 2001 

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A-8 
(Page 1 of 6) 

August 23, 2001 

1.1.1.1.1. Poisonous Inhalation Hazard Liquids 

Acetone cyanohydrin, stabilized 4921401 

Acrolein, inhibited 4927007 

Allyl alcohol 4921019 

Allylamine 4921004 

Allyl chloroformate 4930001/4923113 

Arsenic trichloride 4923209 

Boron tribromide 4932010 

Bromine or Bromine solutions 4936110 

Bromine trifluoride 4918507 

Bromine pentafluoride 4918505 

Bromoacetone 4921727 

n-Butyl chloroformate 4921730 

sec-Butyl chloroformate 4921207 

n-Butyl isocyanate 4907415/4927027 

tert-Butyl isocyanate 4907485/4927026 

Chloroacetone, stabilized 4921558 

Chloroacetonitrile 4921009 

Chloroacetyl chloride 4931210/4923117 

Chloropicrin 4921414 

2-Chloroethanal 4921402 

Chloropivaloyl chloride 4921746 

Chlorosulfonic acid 4930204 

Crotonaldehyde, stabilized 4909137/4921248 

Cyclohexyl isocyanate 4921010 

3, 5 Dichloro-2, 4, 6 trifluoropyridine 4921741 

Diketene, inhibited 4912433/4921254 

Dimethylhydrazine, symmetrical 4909352/4921251 

Dimethylhydrazine, unsymmetrical 4921202 

Dimethyl sulfate 4921405 

Ethyl chloroformate 4921020 

Ethyl chlorothioformate 4933327 

Ethyldichloroarsine 4921404 

Ethylene chlorohydrin 4921420 

Ethylene dibromide 4921497 

Ethyleneimine, inhibited 4927006 

Ethyl isocyanate 4907434 

Ethyl phosphonothioic dichloride, anhydrous 4921745 

Ethyl phosphonous dichloride, anhydrous 4921742 

Ethyl phosphorodichloridate 4921744 

Hexachlorocyclopentadiene 4821722/4921722 

Hydrocyanic acid solution in alcohol 4921239 

Hydrocyanic acid aqueous solution or 

hydrogen cyanide, aqueous solutions 4921028 

Hydrogen cyanide, stabilized 4927014 

Iron pentacarbonyl 4927004 

Isobutyl chloroformate 4921211 

Isobutyl isocyanate 4907409 

Isopropyl chloroformate 4907628/4921252 

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(Page 2 of 6) 

August 23, 2001 

Isopropyl isocyanate 4909306 

Methacrylonitrile, inhibited 4910370 

Methanesulfonyl chloride 4921239 

Methyl isothiocyanate 4907453 

Methoxymethyl isocyanate 4909307 

Methyl bromide and ethylene dibromide,mixture 4921438 

Methyl chloroformate 4927008 

Methylchloromethyl ether 4927012 

Methyldichloroarsine 4921275 

Methylhydrazine 4927011 

Methyl iodide 4921304 

Methyl isocyanate 4927009/4921487 

Methyl orthosilicate 4907452/4921255 

Methyl phosphonic dichloride 4921695 

Methyl phosphonous dichloride 4921008 

Methyl vinyl ketone, Stabilized 4927022 

Nickel carbonyl 4927010 

Nitric acid, red fuming 4931201 

Pentaborane 4916138 

Perchloromethylmercaptan 4921473 

Phenylcarbylamine chloride 4921587 

Phenyl isocyanate 4921216 

Phenyl mercaptan 4921413 

Phosphorus oxychloride 4932352 

Phosphorus trichloride 4921016/4832359/ 

4932359 

Poisonous liquids, corrosive, n.o.s. 

(antimony pentachloride, arsenic trichloride) 4821269/4921269 

Poisonous liquids, corrosive, n.o.s. 

(sulfur chloride) 4921276 

Poisonous liquids, corrosive, n.o.s. (vanadium 

oxytrichloride and titanium tetrachloride) 4921262 

Poisonous liquids, corrosive, n.o.s. 

(sulfur dichloride) 4921223 

n-Propyl chloroformate 4921756 

n-Propyl isocyanate 4907458/4927025 

Sulfur Chloride 4930260 

Sulfuric acid, fuming 4830030/4930030 

Sulfur trioxide, inhibited 4930050/4936565 

Sulfur trioxide, uninhibited 4930051 

Tetranitromethane 4918180 

Thiophosgene 4923298 

Titanium tetrachloride 4932385 

Toxic liquid, inorganic, n.o.s. 

[inhalation hazard, Packing Group I Zone A] 4927020 

[inhalation hazard, Packing Group I Zone B] 4921234 

Toxic liquid, corrosive, inorganic, n.o.s. 

[inhalation hazard, Packing Group I Zone A] 4927021 

[inhalation hazard, Packing Group I Zone B] 4921237 

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(Page 3 of 6) 

August 23, 2001 

Toxic liquid, corrosive, inorganic, n.o.s. 

(antimony pentachloride, arsenic trichloride) 4821261/4921261 

Toxic liquid, corrosive, inorganic, n.o.s. 

(sulfur dichloride) 4921264 

Toxic liquid, corrosive, inorganic, n.o.s. 

(sulfur chloride) 4921278 

Toxic liquids, corrosive, organic, n.o.s. 

[Inhalation Hazard, Packing Group I, Zone A] 4927005 

[Inhalation Hazard, Packing Group I, Zone B] 4921270 

Toxic liquids, corrosive, organic, n.o.s. 

(bis(tri-chloromethyl sulfide and dimethyl formamide) 4921263 

Toxic liquids, flammable, organic, n.o.s. 

[inhalation hazard, Packing Group I Zone A] 4927001 

[inhalation hazard, Packing Group I Zone B] 4921271 

Toxic liquids, flammable, organic, n.o.s. 

(chloropicrin) 4921015 

Toxic liquids, flammable, organic, n.o.s. 

(chloropicrin, dichloropropene) 4921064 

Toxic liquids, flammable, organic, n.o.s. 

(methylchlorosilane, dimethylchlorosilane) 4921021 

Toxic liquids, organic, n.o.s. 

[inhalation hazard, Packing Group I Zone A] 4927002 

[inhalation hazard, Packing Group I Zone B] 4921272 

Toxic liquids, oxidizing, n.o.s. 

[inhalation hazard, Packing Group I Zone A] 4927003 

[inhalation hazard, Packing Group I Zone B] 4921273 

Toxic liquids, water-reactive, n.o.s. 

[inhalation hazard, Packing Group I Zone A] 4927030 

[inhalation hazard, Packing Group I Zone B] 4921256 

Trichloroacetyl chloride 4935231 

Trimethyl acetylchloride 4921063 

Trimethyloxysilane 4921213 

Trimethylacetyl chloride 4931745 

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(Page 4 of 6) 

August 23, 2001 

Poisonous Inhalation Hazard Gases - Hazard Zones A & B

Arsine 4920135 

Boron trifluoride 4920522 

Bromine chloride 4920715 

Carbonyl fluoride 4920559 

Chlorine 4920523 

Chlorine pentafluoride 4920189 

Chlorine trifluoride 4920352 

Chloropicrin and methyl bromide mixtures 4920547/4920516 

Chloropicrin and methyl chloride mixtures 4920392 

Compressed or liquefed gas, toxic, flammable, n.o.s 

[inhalation hazard Zone A] 4920165 

[inhalation hazard Zone B] 4920396 

Compressed or liquified gas, toxic, n.o.s. 

[inhalation hazard] Zone A] 4920181 

[inhalation hazard] Zone B] 4920570 

Compressed gas, toxic, corrosive, n.o.s. 

[inhalation hazard] Zone A] 4920102 

[inhalation hazard] Zone B] 4920331 

Compressed gas, toxic, flammable, corrosive, n.o.s. 

[inhalation hazard] Zone A] 4920102 

[inhalation hazard] Zone B] 4920303 

Compresses gas, toxic, oxydizing, corrosive, n.o.s. 

[inhalation hazard] Zone A] 4920103 

[inhalation hazard] Zone B] 4920306 

Compresses gas, toxic, oxydizing, n.o.s. 

[inhalation hazard] Zone A] 4920104 

[inhalation hazard] Zone B] 4920337 

Cyanogen chloride, inhibited 4920178 

Cyanogen, liquified 4920395 

Diborane 4920107 

Dichlorosilane 4920398 

Dinitrogen tetroxide, liquefied 4920174 

Fluorine, compressed 4920180 

Germane 4920354 

Hexafluoroacetone 4920528 

Hydrogen selenide, anhydrous 4920122 

Hydrogen sulfide, liquefied 4920513 

Insecticide gas, toxic, flammable, n.o.s 

[inhalation hazard Zone A] 4920116 

[inhalation hazard Zone B] 4920302 

Liquified gas, toxic, n.o.s. 

[inhalation hazard] Zone A] 4920195 

[inhalation hazard] Zone B] 4920571 

Liquefied gas, toxic, flammable, n.o.s 

[inhalation hazard Zone A] 4920164 

[inhalation hazard Zone B] 4920382 

Liquefied gas, toxic, corrosive, n.o.s 

[inhalation hazard Zone A] 4920105 

[inhalation hazard Zone B] 4920311 

Liquefied gas, toxic, flammable, corrosive, n.o.s 

[inhalation hazard Zone A] 4920108 

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(Page 5 of 6) 

August 23, 2001 

[inhalation hazard Zone B] 4920314 

Liquefied gas, toxic, oxidizing, corrosive, n.o.s 

[inhalation hazard Zone A] 4920110 

[inhalation hazard Zone B] 4920312 

Liquefied gas, toxic, oxidizing, n.o.s 

[inhalation hazard Zone A] 4920111 

[inhalation hazard Zone B] 4920317 

Methylchlorosilane 4920394 

Nitric oxide 4920112 

Nitric oxide and dinitrogen tetroxide mixtures 4920113 

Nitrogen dioxide 4920174 

Nitrogen trioxide 4920175 

Oxygen difluoride 4920173 

Perchloryl fluoride 4920356 

Phosgene 4920184 

Phosphine 4920160 

Phosphorus pentafluoride 4920183 

Silicon Tetrafluoride 4920357 

Selenium hexafluoride 4920106 

Stibine 4920167 

Sulfur tetrafluoride 4920187 

Tellurium hexafluoride 4920188 

Trifluoroaceetylchloride 4920347 

Tungsten hexafluoride 4920371 

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(Page 6 of 6) 

August 23, 2001 

Environmentally Sensitive Chemicals

Allyl Chloride 4907412 

Carbon Tetrachloride 4821831/4860106/ 

4921830/4921831/ 

4960115 

Chlorobenzene 4909153 

Chloroform 4925224/4925225 

4921767/4921769 

o-Dichlorobenzene 4915132/4925203 

Dichloropropane (Propylene dichloride) 4909265 

Dichloropropane/Dichloropropene mixture 4910234 

Dichloropropene 4909255 

Ethyl Chloride 4905712/4908129/ 

4908162 

Ethylene Dibromide (already listed as PIH) 

Ethylene Dibromide and Methyl Bromide Mixtures 

(already listed as PIH) 

Ethylene Dichloride 4909166/4912081/ 

4908129/4910437/ 

4913242/4913295/ 

4921030 

Epichlorohydrin 4921005 

Methyl Chloroform (1,1,1 Trichloroethane) 4825182/4925182/ 

4910463/4010475/ 

4915969/4925310/ 

4960205 

Methylene Chloride (Dichloromethane) 4925131/4905764 

Methylene chloride/chloroform mixture 4960150 

Perchloroethylene (Tetrachlorothylene) 4825202/4910134 

4840355/4925202 

Perchloroethylene/Trichloroethylene mixture 4940373 

Trichloroethylene 4925181

 

A-14 
Appendix B. 

Dedicated Train Workshop Notes - Stakeholder Positions 

The Brown Palace 

Denver, Colorado 

September 28 & 29, 1992 

PLEASE NOTE: 

This is intended to capture salient verbal comments made during the two days of the workshop. 

Comments have been loosely organized by subject and so do not follow in chronological order. The 

name of the commenter is given in (parentheses) preceding or sometimes following the statement. 

Statements that are available in written form are only briefly summarized to the chairman for 

consideration in the study is not included herein. 

DOE/OCRWM. (Mike Conroy) OCRWM shipments must move in compliance with DOT and NRC 

regulations (unlike the Naval Reactor shipments). The NRC-certified packages assure safe transport. 

DOE does not believe dedicated trains are necessary for safety, a position said to be corroborated by the 

findings in various court cases. DOE also points out that the Congressional Office of Technology 

Assessment found (in its 1986 report on hazmat transport) that the casks provide a high level of public 

protection and that mandated use of dedicated trains was found by the Interstate Commerce Commission 

(ICC) to be wasteful. Furthermore, DOE maintains that dedicated trains are not needed to meet NRC 

safeguard requirements. However, OCRWM will use dedicated trains where they are operationally 

advantageous and cost effective. Plans are to use them for MRS-to-repository shipments where DOE 

would have control over both origin and destination sites. DOE has been studying use of dedicated trains 

from the reactors as well, but they may not be possible or cost effective from all of the facilities. 

Conrail. [written statement submitted] (Allan Fisher) Conrail believes dedicated trains are necessary 

because the railroad can: 

• Plan route to avoid urban areas and use safest route 

• Avoid yards 

• Control schedule 

• Provide better surveillance and security 

• Limit accident forces on cask by limiting speed 

• Better control speed and braking, buff and draft forces 

• Control other trains being met or passed 

• Provide for emergency response more quickly 

• Reduce the chance that the cask will be involved in a fire 

Union Pacific. [written statement submitted] (Leo Tierney) “It is UP’s strong position that dedicated 

trains are essential for the movement of these radioactive materials in order to satisfy all the operational 

and safety considerations surrounding these shipments.” The 35 mph restriction on DOD SNF shipments 

has a negative impact on the safety of train operations. It is not feasible to use slow, local trains to 

provide the service. UP must put cask cars on manifest or secondary trains which must be slowed to 35 

mph. This disrupts operations and increases risk (in addition to increasing cost and having service 

impacts). As shown in the TMI campaign, dedicated trains have the following safety advantages: less 

B-1
handling and switching, less likelihood of equipment failure including derailment, safer train handling, 

easier to meet surveillance requirements, and eliminates potential exposure to hazmat in accident. 

Southern Pacific. [written statement submitted] (John Smith and Ken Moore) SP believes that 

dedicated trains are required for the DOD SNF shipments “for maximum security and risk reduction.” 

Like UP, SP “does not hold itself out to offer 35 mph service.” That speed restriction makes for a slow 

transit in regular service with much time sitting, often in exposed locations. This makes the cask car an 

easier target for terrorists and obstructionists. Security is further impaired by the anonymity (e.g., secrecy 

and lack of placarding) with which these moves take place. SP is also concerned about the risk to the 

cask of placing it in the same train with flammables, explosives and other hazmat. Furthermore, the DOD 

requirement that the heavy cask car be placed at the end of the train creates track/train dynamics that 

increase the likelihood of derailment, especially for long regular trains, as evidenced in ongoing analyses. 

Utilities/ Edison Electric Institute. (John Vincent) Uncertain of the safety improvement of dedicated 

trains. 

States. 

(Don Howell- ID) A state’s attitude is a function of whether it is a generating state (of SNF), a repository 

state, or a transit state. 

(Max Power- WA) Outreach is important. Advance planning needs to be done, in part to assure better 

preparedness. (State) control over the shipping activity is important and there should be no surprises (for 

state officials). They need to know the what, when, where about each shipment. Placarding is important. 

(Bob Halstead- NV) Low risk is not the same as no risk. Risks are higher with regular freight service. 

Minimize the number of shipments through the use of dedicated trains and use the AAR guidelines for 

their operations, in general. 

“Most people” assume that if there were an MRS, DOE would use dedicated trains (3 casks each) from 

the reactor sites as well as between MRS and repository. 

To maintain the nuclear power option, shippers should be willing to take (safety) measures. Utilities 

behave more this way than DOE. Dedicated trains would address some of the public concerns. 

National Conference of State Legislature (NCSL). (Senator Hickey, Chairman of the Task Force on 

High-Level Radioactive Waste/Hazardous Materials Transportation) NCSL supports the use of dedicated 

trains. In its position statement, NCSL recommends that DOE “utilize to the maximum extent unit or 

dedicated trains for spent fuel shipments to enhance safety and to increase public acceptability.” States 

need to have a direct relationship with railroads regarding RAM transportation, much like that they have 

with motor carriers now. Concerns over emergency response are substantiated by the recent Springfield, 

Massachusetts incident as documented in NTSB report. Also, there are concerns over the safety of mixed 

trains (compared to dedicated trains) due to (1) lower reliability of braking systems, given the mix of 

“foreign” cars, (2) potential for terrorist acts, and (3) the use of 2-man crews. The effect of crew 

reductions have yet to show up in train safety data due to the short time since this practice became 

developed. 

B-2
Additional Recommended Safety Measures 

The qualitative assessment performed by workshop participants also identified four safety measures that 

have notable potential for enhancing safety. 

1. Maintain a fixed train set. This ensures that the train equipment is, at all times, of appropriate 

quality and type. Also, the reliability of the braking system is improved since no “foreign” cars 

are used and (de) coupling is eliminated. Dedicated trains are a decided advantage because the 

consist would normally be fixed, with only the locomotive(s) switched between railroads. A fixed 

train set or consist, other than the cask car block, is not practical with regular service. 

2. Ensure the use of appropriate, safe equipment. In recent years, about 15% of all accidents have 

been due to equipment failures.1

 Therefore, it is important that all equipment in the train be 

reliable. In particular, buffer cars should be good quality, heavy, low-profile cars; in the past, 

railroads have often supplied poor, non-revenue cars as buffers. Operating a fixed cask car block 

helps. Employing a fixed train set plus frequent inspections ensure that the entire (dedicated) 

train is made of appropriate, reliable equipment. 

3. Enhance crew competency. About 1/3 of all accidents are caused by “human factors.”2

 Such 

accidents might be reduced by cutting duty hours and increasing the size of the crew 

(unfortunately, the latter would also increase total crew exposure). It has also been suggested that 

crews for cask trains could be specially trained and hand-picked. However, labor contracts and 

work rules limit what can be done, even with a dedicated train. 

4. Increase awareness of shipments and safety measures taken. Public officials contend that the 

more that the public is aware of shipping campaigns, safety measures taken, and the timing of the 

shipments themselves, the safer the operation becomes. Demand for counterproductive (i.e., 

hazardous) measures such as the use of chase cars, is reduced. Unnecessary evacuations may be 

avoided along with other improper emergency response actions. Occurrence of demonstrations 

and related actions may be diminished.3

 Advantages for dedicated trains are the enhanced 

visibility and precision of their movements and the greater number of safety measures that are 

being taken. 

Other Findings 

Most of the 25 safety measures were found by the Denver September 1992 study team to offer little or no 

potential for safety enhancement by virtue of using dedicated trains. Either they were judged to be 

relatively ineffective and/or they could be implemented nearly as well with regular train service. 

Interestingly, a net decrease in safety was found for implementing two of the 25 measures. In one case, 

counterproductive aspects were thought to outweigh the benefits and, in the other, regular trains were 

found to have the advantage: 

1. Passing Restrictions. Requiring one of two passing trains to stand (stop) was thought to be 

potentially counterproductive. Benefits of the passing restriction included a reduction in the 

 

1 Of the 2785 accidents reported to FRA in 1993, 13% were due to mechanical and electrical failures of locomotives and cars 

(Ref. 32, FRA). 2 In 1993, 31% of all reported accidents were attributed to “train operation – human factors” Ref. 32, FRA). 

3 Some shippers contend that awareness may only breed unreasonable demands for more “safety” measures and 

obstructionist activities, and may degrade security. 

B-3
likelihood and severity of raking accidents as well as elimination of the chance of involvement 

with derailments of the train on the adjacent track during passing. However, these benefits are 

probably outweighed by the hazards associated with the considerable disruption of rail traffic, 

especially the braking of following trains.4

2. Cask Car Placement. Constraining the location of the cask car in the consist was found to be a 

potentially effective means of reducing the chance that the cask would be damaged in an accident. 

Radiological dosage to onboard personnel can be lessened as well. The advantage, however, lies 

with regular trains. Short dedicated trains offer little opportunity to use placement of the cask car 

in the consist as a means of cutting risk. 

Results of the Qualitative Analysis 

In summary, the qualitative analysis of 23 safety measures associated with dedicated trains showed 

that some appear to have the potential to significantly improve safety, but most do not. Run-through 

operation benefits. Both incident-free and accident-induced radiological risk for such operations 

should be relatively low. However, the former can be estimated more accurately because it is directly 

related to transit time, an easily measured variable. Transit time should be 20-40% of that for regular 

trains; radiological exposure should be similarly lower.5

 In addition to this certain enhancement of 

safety, the accident-related risk should be less, though it is difficult to determine this quantitatively 

with any confidence; accident rates and release probabilities for dedicated trains are largely a matter 

of conjecture. Nonetheless, there are important factors that suggest a much lower accident rate. Runthrough operations do not enter classification yards, the site of nearly half of all accidents (albeit lowspeed ones). The short, fixed consist is safer to operate: derailments due to equipment failures and 

track-train dynamics would be far fewer, train controls would be simpler and safer, and the braking 

system more reliable. However, should an accident occur, the short train may or may not have an 

advantage. Lower kinetic energy would mean lower accident forces (and release probabilities) and 

the absence of flammable and explosives in the dedicated consist reduces that hazard. However, the 

train’s short length would increase the chance that the cask would be impacted in front or rear 

collisions. 

The qualitative analysis also indicated that operational restrictions may not be warranted. 

Accident Rates – Insight from “Key Train” Operations 

Accident rate data (accidents per million train-miles) is not available for dedicated trains because 

information on accidents and train-miles is not kept by type of train. However, some indication of 

what that accident rate might be can be gleaned from recent experience with “key trains,” for which 

some data was obtained for this study. In 1990, the AAR published a circular entitled, Recommended 

Railroad Operating Practices for Transportation of Hazardous Materials. That publication defines 

“key trains” as those trains that would receive special treatment because of the particularly hazardous 

nature of their cargo. Among other restrictions, AAR recommends that key trains be limited to 50 

mph (80.4 km/hr), that no cars with friction bearings be allowed in the consist, and that they remain 

on the main track at meets and passes. 

 

4 Detailed simulations of railroad operations incorporating hazard probabilities would be necessary to verify this subjective 

conclusion. 5 There are, of course, other factors. Dose levels for the train crew would be higher for the shorter train, for example. On the 

other hand, workers in yards would not be exposed in run-through operations. 

B-4
Data for key trains operated by Union Pacific were analyzed to see if trains that are made up and 

operated in ways intended to improve safety actually experience lower accident rates. Over the past 

three years, UP has operated from two to five daily trains that were permanently designated as “key 

trains.”6

 In addition to the restriction AAR recommends, Union Pacific generally limits the length of 

designated key trains to 100 cars or 6,000 feet. Information on key trains was obtained from Union 

Pacific: accidents reported to the FRA, number of trains run annually, and train-miles operated. For 

1990-1992, UP operated 4,368 key trains a total of 2.4 million train-miles. 

For the two years for which comparable data on UP’s other train operations are available (1990-

1991), the train accident rate for designated key trains averaged 2.2 per million train-mile vs. 7.1 for 

the Union Pacific as a whole. A statistical analysis of these data found that, despite the relatively 

small size of the database, there was nearly a 99% probability that key trains actually did have a lower 

accident rate during that period.7

 

Examination of the eight accidents reported for designated key trains (1990-1992) indicates that half 

of them would not have happened to a dedicated train and that one quarter would have been less 

likely. Three accidents occurred during activities in which dedicated trains do not engage, namely, 

yard operations and setting out and picking up cars along the mainline. A fourth inapplicable 

accident was caused by exceeding a 30 mph restriction for a bridge crane car that was part of the key 

train consist. Two of the accidents, though applicable to dedicated trains, would be less likely due to 

shorter train length. One of these, a serious release of hazardous materials, was caused by a journal 

failure on one of 72 cars in the train. The shorter dedicated train would experience proportionally 

fewer journal failures per million train-miles. In another accident, a broken switch point caused the 

last car of a 126-car train to derail. Assuming this was a random event that could affect any car in a 

train, a short dedicated train would be less likely to experience such a derailment accident because it 

has fewer cars. Two accidents, one at a grade crossing and another during delivery of cars on a poor 

industrial track, were judged to be as likely to occur to a dedicated train as to a key train. 

Setting aside the four accidents that would not be applicable to dedicated trains and scaling the 

probabilities for the two accidents that are a function of consist size yields a rate of slightly less than 1 

accident per million train-miles. This compares with a rate of 3.3 for UP’s key trains (1990-1992), an 

overall average for UP of 6.7 (1986-1991), and a national average of 4.9 accidents per million miles 

over the years 1986-1991. While this suggest that dedicated trains would have a substantially lower 

accident rate than regular trains, it would not be appropriate to use these results in a quantitative 

analysis. First, substantial differences remain between key trains and dedicated trains even after 

adjusting the accident history. Second, the sample size is small – there were only eight accidents in 

the key train data set. 

 

6 The railroad also operates other key trains when circumstances warrant. However, only data on the permanently designated key 

trains could be made available. 7 The size of the data set for key trains is small in light of the low frequency of train accidents. Consequently, large year-to-year 

fluctuation can be expected, as happened from 1991 to 1992 (from 2 to 4 accidents despite a significant decline in trainmiles). More observations from other key train operations and/or over a longer period are needed to generalize these findings 

with appropriate levels of confidence. 

B-5
This Page Intentionally Left Blank 

B-6
Appendix C. 

Reported Incidents Involving Spent Nuclear Fuel Shipments 1949 to 2002 

This appendix includes a summary of incidents involving spent nuclear fuel (SNF) shipments by rail and 

truck from 1949 through September 30, 2002. In reviewing this history, it is important to consider the 

changes in hazardous material transportation regulations and packaging requirements in particular. The 

incidents listed below cover a wide period of time during which packaging requirements were 

continuously refined. In the early 1950s, the Interstate Commerce Commission (ICC) first established 

radioactive material regulations limiting the radiation levels that emanate from packages to protect 

radiation-sensitive cargo. In l96l, the International Atomic Energy Agency (IAEA) adopted radioactive 

material transportation regulations (standards) based largely on those of the ICC. In 1973, revisions to 

IAEA standards introduced the concepts for Type B packages, to determine the extent to which each 

country must approve a package design when an international shipment is involved. In 1983, the U.S. 

Department of Transportation (DOT) and the Nuclear Regulatory Commission (NRC) adopted 

regulations, which essentially brought them into conformance with the 1973 edition of the IAEA 

requirements. 

There have been 72 reported incidents involving SNF shipments by rail and truck from 1949 to 

September 30, 2002: 

• From 1949 to 1970, 14 incidents were reported in a series of U.S. Atomic Energy Commission 

reports. They included six transportation-related accidents, three truck and three rail, none 

resulting in a release of radiation. The incidents also included eight non-transportation incidents 

(e.g., leakage of cask, contamination during loading/offloading) that resulted in small amounts of 

observed contamination. 

• From 1971 to September 30, 2002, 58 incidents have been reported in the Radioactive Material 

Incident Report database operated by Sandia National Laboratories. They included seven 

transportation-related accidents, four truck and three rail, none resulting in a release of radiation. 

The incidents also included 51 non-transportation incidents, 49 of which resulted in small 

amounts of observed contamination. 

The 72 incidents can be characterized as follows: 

• 59 non-transportation incidents (e.g., leakage of cask, contamination during loading/offloading): 

• 4 incidents of accidental radioactive contamination beyond the vehicle 

• 4 incidents of accidental radioactive contamination confined to the vehicle 

• 49 incidents of accidental surface contamination 

• 2 other incidents without additional descriptive material 

• 13 transportation-related incidents: 

• 7 truck incidents resulting in no release or contamination 

• 6 train incidents resulting in no release or contamination 

Eight incidents of radioactive material contamination, which were discovered during shipping (between 

1960-1984), involved leaks of water, liquid, or (reported as) coolant/moderator from casks. Description 

of the events and equipment are insufficient to evaluate the failure mechanisms or sources of 

contamination. The abbreviated information provided, however, seems to indicate contributing factors 

may include the absence of regulations for the design and use of transport casks, inadequate procedures, 

or not following the procedures. 

C-1
Table C-1 describes each of the 72 incidents in more detail. 

Table C-1. Reported Incidents Involving SNF Shipments 

1949 to September 30, 2002 (72 incidents by type) 

Date Mode Incident Description 

Radioactive material contamination beyond the vehicle (4 of 72 incidents):

6/2/60 Rail Leak from cask, small areas at three rail yards contaminated, no runoff or aerial 

dispersion. 

8/21/62 Truck Cask leakage, trailer, and small portion of road contaminated. 

11/11/64 Truck Cask leakage, trailer, packages, and terminal contaminated. 

1/27/84 Truck Slow drip from bottom front end of empty cask while stored in transportation 

terminal. 

Radioactive material contamination confined to vehicle (4 of 72 incidents):

11/20/60 Truck Small leak from cask onto trailer floor, result of shifting cask; contamination 

confined to vehicle. 

9/22/61 Truck Leak from cask onto trailer floor, result of shifting; contamination confined to 

vehicle. 

12/10/63 Rail Cask leakage, cask contaminated, contamination confined to trailer. 

7/4/76 Truck Pinhole leak, reported as coolant/moderator on outside jacket of cask. Shipment 

continued without risk to public. 

Transportation accident with no release or contamination (13 of 72 incidents):

12/1/56 Truck Slid off icy road and overturned, two casks, one fell off trailer; no damage, no 

release. 

1/29/57 Rail Uncoupling, damage from debris; no release. 

4/15/60 Truck Trailer unhitched from tractor at 5 mph; no release. 

11/15/60 Truck Truck jackknifed; struck station wagon; no release. 

12/7/60 Rail Engine backed into cask car on siding; no release. 

7/14/61 Rail Minor derailment at 10-12 mph; no release. 

12/8/71 Truck Truck left road and cask thrown off; no release. 

3/29/74 Rail Derailed tank car struck cask car in yard, empty cask; no release. 

2/9/78 Truck Trailer buckled from weight; no release. 

8/13/78 Truck Empty cask broke through trailer bed; no release. 

12/9/83 Truck Tractor separated from intermediate set of axles, remained connected to trailer; 

no release. 

3/24/87 Rail Train struck automobile at rail crossing; no release. 

1/9/88 Rail One set of rail car wheels derailed when switching tracks, empty cask; no release.

Surface contamination (49 of 72 incidents):

1/24/74 Truck Surface contamination on shipping pallet. 

2/26/74 Truck Surface contamination on pallet and truck, empty cask. 

4/29/74 Truck Surface contamination on pallet. 

12/11/74 Truck Surface contamination on pallet. 

12/23/74 Truck Surface contamination on pallet. 

1/13/75 Truck Surface contamination on cask. 

2/27/77 Truck Surface contamination on lifting yoke, empty cask. 

4/13/77 Truck Surface contamination on trailer, empty cask. 

5/3/77 Truck Surface contamination on empty cask. 

5/12/77 Truck Surface contamination on empty cask. 

5/16/77 Truck Surface contamination caused by small crack in impact limiter. 

7/26/77 Truck Surface contamination on empty cask. 

8/3/77 Truck Surface contamination. 

8/23/77 Truck Surface contamination on cask. 

2/16/78 Truck Surface contamination caused by open drain valve, empty cask. 

2/27/78 Truck Surface contamination on empty cask. 

C-2
5/16/78 Truck Surface contamination on empty cask. 

7/24/78 Truck Surface contamination on empty cask. 

7/29/78 Truck Surface contamination on cask. 

8/1/78 Truck Surface contamination on cask. 

8/7/78 Truck Surface contamination on cask. 

11/27/78 Rail Surface contamination on empty cask, yoke, and rail car caused by defective 

valve or closure. 

3/28/79 Truck Surface contamination on empty cask and trailer. 

4/2/79 Truck Surface contamination on cask. 

4/2/79 Truck Surface contamination on empty cask. 

4/3/79 Truck Surface contamination on tire chains, hold-down chains, and tighteners caused by 

loading or unloading cask from trailer. 

4/4/79 Truck Surface contamination on empty cask. 

4/5/79 Truck Surface contamination on trailer, empty cask. 

7/23/80 Truck Surface contamination on empty cask. 

8/25/80 Truck Surface contamination on cask. 

2/2/81 Truck Surface contamination on empty cask and trailer. 

5/30/81 Truck Surface contamination on cask and trailer. 

5/31/81 Truck Surface contamination on empty cask. 

6/2/81 Truck Surface contamination on cask. Third consecutive instance of surface 

contamination. NRC suspends further shipments. 

8/25/83 Truck Surface contamination on empty cask. 

9/30/83 Truck Surface contamination on empty cask. 

10/21/83 Truck Surface contamination on empty cask. 

1/7/84 Truck Surface contamination on empty cask. 

1/25/84 Truck Surface contamination on empty cask. 

2/24/84 Truck Surface contamination on cask. 

1/11/85 Truck Surface contamination on trailer; empty cask. 

2/3/85 Truck Surface contamination on cask. 

7/8/85 Truck Surface contamination on empty cask. 

2/28/86 Truck Surface contamination on empty cask. 

7/29/86 Truck Surface contamination on cask. 

7/29/86 Truck Surface contamination on empty cask and trailer. 

8/19/86 Truck Surface contamination on cask. 

10/15/91 Truck Surface contamination on empty cask. 

8/14/92 Truck Surface contamination on cask. 

Unknown (2 of 72 Incidents):

1965-1967 One incident, details not available. 

1968-1970 One incident, details not available. 

Definitions for release and contamination as used in transport accident or event reports: 

RELEASE An official definition for release from a cask is not found in NRC’s 10 CFR 

71.4, Definitions. An NRC definition of release as it pertains to 

transportation, however, can be inferred from 10 CFR 71 as follows: 

[10 CFR 71.4, Definitions] “Containment System means the 

components of a packaging intended to retain the radioactive material 

during transport.” 

[10 CFR 71.5 1, Additional requirements for Type B packages] 

Paragraph (a)(1) prohibits loss or dispersal of radioactive contents for 

normal condition of transport. Paragraph (a)(2) restricts escape of 

krypton or other radioactive materials for hypothetical accident 

C-3
conditions. Finally, the word “release” is used in paragraph (b) which 

states: “Compliance with the permitted activity release limits of 

paragraph (a) of this section must not depend upon filters or upon a 

mechanical cooling system.” 

From the above 10 CFR 71 material the authors can develop a definition 

that is consistent with NRC’s rules and regulations. Release means 

loss, dispersal, or escape of radioactive material from the package’s 

containment system. 

CONTAMINATION 10 CFR 71.87(l)(1) and (1)(2), routine determinations refers to non-fixed 

(removable) radioactive contamination on external surfaces. These 

paragraphs prescribe specific limits for transport of radioactive materials. A 

formal definition, however, is not provided. 

Although the NRC’s regulations do not provide a definition for 

contamination in 10 CFR 71, a definition is provided in NUREG-0770 (U.S. 

Nuclear Regulatory Commission, Glossary of Terms Nuclear Power and 

radiation, NUREG-0770, Washington, DC 20555, June 1981). 

Contamination is defined as “the deposition of unwanted radioactive material 

on the surface of structures, areas objects, or personnel.” 

C-4
Appendix D. 

Route-Specific Analysis 

An example using Geographic Information System (GIS) data for one route identified major features and 

risk exposure:

In most of the analyses in this appendix, data are aggregate. As in Chapter 2, this analysis focuses on 

presenting information at a route-specific level for several reasons. First, analyses of this sort generally 

focus on route-specific risk, and for comparability to similar studies (such as NUREG 6672) presentation 

of this type of information is valuable. Second, the true effect of operational restrictions can be most 

easily illustrated by looking at route-specific risks. Finally, it enables the quantification of the accident 

probability impacts for the route in the same form with which non-accident risk is evaluated. Several 

inputs were used to conduct this route specific risk analysis: 

• Identification of a rail route that conforms to the U.S. Department of Energy preferred routing 

(using their rail route selection criteria specified in INTERLINE). 

• Identification of risk factors for that route including: 

• Yards 

• Accident locations 

• Bridges 

• Surface hardness 

• Local topography 

To address route-specific risk in the accident analysis, one route was selected for further detailed analysis. 

The Humboldt, CA, to Yucca Mountain, NV, route was used to illustrate how risk may be concentrated in 

specific environments, as well as what the effect of train speed and operational restrictions may be on the 

likelihood of accident involvement. 

Available data are incomplete and insufficient to fully characterize release probability (using surface 

hardness or topography) for the Humboldt route. Figure D-1 and Figure D-2 illustrate the percent of the 

total route area that could be characterized with available data from the U.S. Geological Survey (USGS) 

on surface hardness in the vicinity of the track and surface contour. The location of railroad bridges, 

yards, and the proximity of accidents to these environments, however, illustrates that risk is not evenly 

distributed throughout this route, therefore leading to the hypothesis that a uniform accident rate per route 

mile may be inappropriate for evaluating shipment routes. 

An examination of the Humboldt route allowed the researchers to characterize the position of several 

track features (including switches, signals, yards, bridges, and stations) to characterize the slope and 

environment adjacent to the track for about 10 percent of the route and describe the surface hardness in 

that area. Using the milepost location reported in the accident reports in Railroad Accident/Incident 

Reporting System (RAIRS), 232 accidents were assigned on the route. These represent (232/11,485) 0.2 

percent of the mainline accidents during the time period. 

The California route represents approximately 1,000 rail route miles from Humboldt, CA, to Yucca 

Mountain, NV (although complete rail access to Yucca is not available at this time) [DOE, 2000]. Traffic 

density on this route varies from approximately 40 to 149 million gross tons per year. The route includes 

about 700 of the State’s 3,300 public grade crossings. 

Of the 232 accidents that were assigned to the route based upon the RAIRS accident record, 131 occurred 

within 262 miles of one another (see Figure D-1). This mileage amount reflects approximately 26 percent 

of the total rail route miles, but the accidents represent 65 percent of the total assigned to locations on this 

route. 

D-1 
Humboldt to Yucca Mountain Route 

Figure D-1. Humboldt to Yucca Mountain Route–All Features 

 D-2 
Humboldt Route Detail Soil and Contour Data Included 

Figure D-2. Humboldt Route Detail–Soil Hardness and Contour Data Coverage 

D-3 
Characterization for Surface Hardness

An examination of the environmental characteristics of the Humboldt route included an estimate 

of the slope of the ground in the immediate vicinity of the track and the surface hardness of that 

environment based upon soil usage data. 

Slope data was assigned to a significant portion of the route (see Figure D-2). Slope categories 

were defined based upon the percent of grade change in the area and assigned to a value 1-5 with 

1 being the least slope. Figure D-2 illustrates that a significant portion of the accidents that 

occurred in the southern portion of the Humboldt route occurred in the vicinity of the highest 

category of slope. In addition, many of these accidents occurred in close proximity to bridges and 

yards. 

Railroad Bridges 

Table D-1 shows the California/Humboldt route bridge numbers and clearances. 

Table D-1. California Railroad Bridges 

Total 

Route 

Miles 

Number of 

Railroad 

Bridges 

Clearance 

Average 

Clearance 

Maximum 

Bridges per 

Route Miles 

State of 

California 6393 729 16.4 feet (5 meters) 

98.4 feet 

(30 meters) 11.5 

Humboldt Route 801 346 

9.8 feet 

(3 meters) 

18.0 feet 

(5.5 meters) 

43 

Bridge Derailments 

Probability of Cask Car Involvement Given Bridge Derailment 

During the analysis period, 245 bridge-related accidents were identified. Using this gross-level 

data, the national probability that a derailment occurs on a bridge is 245/24,380 or 0.01. (One of 

those accidents occurred on the Humboldt route.) 

A complete characterization of bridge heights and clearances was obtained for Route 4 in the 

study. Figure D-3 shows the distribution of bridge heights for the River Bend, LA to Yucca 

Mountain, NV route. Only 84 of the 1,332 railroad bridges listed by the Union Pacific Railroad 

for this route exceed a 30-ft (9.1-m) height, yielding a probability of encountering a bridge high 

enough to result in an equivalent drop to the U.S. Nuclear Regulatory Commission (NRC) 

compliance level of 84/1332 or 0.063. Multiplied by the probability per mile of encountering a 

bridge, 0.01, the probability of encountering a bridge over 30 ft (9.1 m) is equal to 0.00063. 

D-4 
0

50

100

150

200

250

1

Bridges with Heights Greater than 30 Feet - Route 4

Bridge Height (feet)

Figure D-3. Bridge Maximum Height–Route 4 

Derailments at bridges that may result in the cask car (or other cars in the consist) derailing and 

falling from a significant height is of concern, particularly since drops of greater than 30 ft (9.1 

m) may exceed the impact velocity threshold defined by the NRC’s compliance tests. Few of 

these bridges, however, span environments that can be described as unyielding surfaces. 

For the purposes of this study, the issue of bridge heights and their potential hazard is limited to 

whether or not the dedicated train is more or less likely to be at risk crossing bridges than would 

be a regular train. To address this issue, the question of whether the position of the car in the 

consist (either in the front, the rear, or some other position) affected the likelihood of derailment 

was examined. It was thought that since, in the dedicated train, the cask car will be very near the 

front of the consist, and, in a regular or key train, it might be entrained toward the end of the train, 

the dedicated train risk might differ from a regular or key train. Figure D-4 illustrates the results. 

Based upon an analysis of the position of the first derailing car in bridge accidents, it was found 

that no one car position is more likely to be involved in the derailment at a bridge than any other. 

This figure plots the frequency of derailments in which the first car in the train was the first 

derailing car in a bridge derailment, second car, third car, and so on. The graph illustrates that the 

first derailing car is most often the locomotive, followed, in frequency, by the 9th car. However, 

the 3rd through 8th cars have nearly the same probability of being the first involved car. Since the 

probability that the cask will derail at the 5th car position as the first derailing car therefore 

sustaining the greatest impact after a fall, is equal for the 5th car position and the 29th car position, 

and only slightly different thereafter, no additional analyses of this factor in distinguishing regular 

and dedicated train risk was undertaken. 

D-5 
Number of bridge derailment accidents with first 

derailing car in this position

0

5

10

15

20

0 10 20 30 40

Car position

Count

Series1

Figure D-4. Bridge Derailment Distribution 

Conclusions from analysis of the Humboldt route are: 

1. Most derailment risk is centered near yards (even on the mainline) and in the vicinity of 

features, such as switches or bridges. 

2. Application of speed limits and operational restrictions would reduce the probability that 

high-speed derailments with high potential damage to the cask would occur. 

3. Due to the proximity of yards to population centers along the route, reduction of yard 

visits would also reduce the probability that low consequence accidents (such as delays 

resulting from a low-speed derailment) could affect the surrounding population. 

D-6 
Appendix E. 

Rail Transport of High-Level Radioactive Material 

Shipping Patterns and Amounts: Past, Present, and Future 

Compared with other hazardous materials, the shipping patterns for radioactive material (RAM) are 

relatively simple because a limited number of origins and destinations exist. Commercial shipments of 

spent fuel principally originate at the nuclear power reactors operated by utilities; some shipments are 

also from university and other research reactors. To date, most of these shipments were made because 

Spent Nuclear Fuel (SNF) storage pools at the reactor sites were at or near capacity. For the near term, 

reracking to increase pool capacity and the use of dry storage techniques will reduce the need for SNF 

transport from power plants. U.S. Department of Energy (DOE) shipments of naval spent fuel originate 

at the five U.S. Navy shipyards equipped to service the reactors of nuclear-powered ships: Bremerton, 

WA; Charleston, SC; Newport News, VA; Pascagoula, MS; and Portsmouth, NH. Future shipments of 

defense high-level waste would originate from current storage locations such as the Hanford Reservation, 

WA; Savannah River Site, SC; and the Idaho National Engineering Laboratory (INEL), ID. In the past, 

destinations have been other reactor sites (inter-plant transfers of SNF) and current high-level radioactive 

waste (HLRW) sites (e.g., DOE shipments of Department of Defense (DOD), SNF to INEL). Most future 

shipments will be destined for either: (1) private interim storage, such as PFS in Utah; (2) interim storage 

facilities for HLRW at Federal sites; or (3) the recently endorsed national repository at Yucca Mountain, 

NV. 

For the years 1979-1991, approximately 1,200 commercial SNF shipments totaling 1,091 tons of uranium 

(990 metric tons of uranium (MTU)) existed. Most all of these were relocations of spent fuel to facilities 

that could provide interim storage. Only about 10 percent of the shipments were by rail, but these 

accounted for nearly two-thirds of the tonnage [NRC, 1992]. To date, there have also been about 500 

shipments of naval SNF, mostly to INEL. All of these were via rail; more than half were moved in 

regular trains and the rest in dedicated trains.1

 

By the year 2046, the DOE estimates that waste inventories will be between 63,000 and 105,000 metric 

tons of heavy metal (MTHM) for commercial SNF; 2,333 to 2,500 MTHM for DOE SNF; and 8,315 to 

222,280 canisters of HLRW [DOE, 2002]. This material will be transported to the national repository 

either directly from 72 commercial and 5 DOE sites across the United States or indirectly via interim 

storage and consolidation facilities. The number of rail shipments for SNF and HLRW over a 24-year 

campaign could range from 300 to 18,300 depending on the mode emphasis of the shipping campaign. 

This traffic would at most average two shipments per day, depending primarily upon the presence and 

location of an interim facility (or facilities).2

Casks, Trains, and Shipping Campaigns 

The Nuclear Regulatory Commission must certify that a cask design meets those regulations before such 

casks can be used to transport spent fuel.3

 Rail casks commonly used in past and current commercial 

shipments weigh about 75 tons (68 metric tons); DOE’s civilian waste program plans to use 100-ton (91-

metric ton) casks. Those used most commonly to transport defense spent fuel and related material also 

weigh about 100 tons (91 metric ton). New, heavier casks are now replacing the existing fleet [ICC, 

 

1

 According to the written statement submitted by Larry Blalock, Director of the Transportation Management Division (DOE), to 

the Dedicated Train workshop held September 28-29, 1992. 2

 Rail shipments to the proposed private fuel storage (PFS) facility in Utah will alter these numbers considerably since SNF 

would move there first and be moved again to the Yucca Mountain Repository when it opens. 3

 Applies to casks used by commercial shippers and those to be used by DOE in the civilian radioactive waste program. Casks 

used by DOE to ship DOD spent fuel need not be certified by NRC if DOE issues its own certificate. However, it has been 

DOE’s practice to request NRC review of the cask designs for the Naval Reactors Program. In fact, NRC has issued 

certificates of compliance for all three types of casks including one for the M-140 cask (dated October 2, 1992). 

E-1 
1992a]. DOT regulations require that the casks be clearly marked with placards that identify the nature of 

their cargo. Casks and cask cars carrying DOE or DOD shipments which are “for the purpose of national 

security” and which are escorted by agency personnel are not subject to placarding requirements.4

Commercial rail casks are usually placed on conventional flatcars weighing about 30 tons (27 metric ton). 

The casks used in defense SNF shipments ride on specially designed rail cars. A 6-axle depressed center 

flatcar weighing about 60 tons (54 metric ton) is used with the older casks; an 8-axle, 70-ton car carries 

the heavier casks [ICC, 1992a]. 

In commercial and defense shipping campaigns, cask cars are accompanied by buffer cars which serve to 

separate them fore and aft from other cargoes and people on board. A single cask car is typically 

accompanied by two buffer cars and a personnel car, housing escorts and sometimes emergency response 

experts.5

 This unit of cars, referred to herein as a “cask car block,” can either be hauled from origin to 

destination by a combination of local and manifest (i.e., regular) trains or a dedicated train.6

 

Rail shipping campaigns to date have used regular and dedicated train service. Over 700 shipments of 

naval reactor SNF and related material have been made since the late 1950s. Of these, about 300 used 

regular trains. In the past, dedicated trains were sometimes used at the initiative of certain carriers. All 

defense shipments now use regular train service. DOD/DOE has advised the railroads that the shipments 

are not time-restrictive and may be moved in local or non-priority regular train service. As a result, the 

railroads have moved the shipments at their convenience in recent years [ICC, 1992a].7

 Currently, about 

50 shipments are made annually. Earlier commercial shipments also used regular train service, including 

15 shipments (1969-1971) by Pacific Gas & Electric from Humboldt Bay, CA, to West Valley, NY. 

More recent commercial shipping campaigns have used dedicated trains, including 30 shipments (1984-

1989) from Cooper, NE, to the General Electric facility in Morris, IL, and 29 shipments (1984-1987) from 

Monticello, MN, to the same destination. There have also been shipments from Robinson, SC, to a 

destination in North Carolina and intra-state movements within North Carolina. Shipments of debris from 

the failed reactor at Three Mile Island, PA, to INEL, ID, also used dedicated trains (1986-1990). 

Commercial shipping campaigns in recent years have also taken additional measures, including speed 

limits, onboard health physicists, operating a rail inspection car ahead of the cask train, escort vehicles, 

and other means of enhancing safety and security. 

 

4

49 CFR 173.7(b). The escorts must travel in a separate vehicle and must have in their possession a document certifying that the 

shipment is for the purpose of national security. 5

Under DOE Order 1540.4, governing “Physical Protection of Unclassified Reactor Fuel in Transit,” an escort must accompany 

each shipment to maintain visual surveillance of the shipment when the train is stopped, but those duties may be assigned to a 

railroad employee. Classified DOD shipments are always accompanied by special escort personnel. 6

In a regular train, buffer cars could be unplacarded; low profile cars from the consist were placed adjacent to the cask car to

serve as buffers (i.e., not part of a dedicated block of cars). However, the use of other consist cars as buffers has been rendered 

unlikely by a highly publicized incident in which an inappropriate buffer car (placarded as containing flammable material) was 

substituted on a Three Mile Island train at an intermediate yard. All remaining Three Mile Island shipments used dedicated 

buffer cars that accompanied the cask car(s) from origin to destination as part of the cask car block. 7

This ICC decision further notes that “for example, the Norfolk Southern will not move the shipments...in its ‘corporate’ or 

scheduled, time-sensitive trains. Moving at the convenience of Norfolk Southern, the radioactive shipments will move during 

weekends, when there is less time-sensitive traffic on its lines, in local service, or on an available ‘extra train.’...Burlington 

Northern generally uses local trains for the movement of radioactive materials...Until recently, the Union Pacific 

accepted...shipments only at specified times on particular days in what it called ‘operating window service,’...UP’s way of 

limiting the service...to non-priority trains.” UP’s current policy is to move all DOD casks/cask cars (loaded and empty) in 

dedicated trains. The only exception is the use of a regularly scheduled, speed-restricted train that departs westbound from 

Kansas City on Sundays. This decision was reportedly prompted by findings of a recent study of longitudinal forces in trains 

hauling heavy cask cars (per letter from L. Tierney, Director of Chemical Transportation Safety, Union Pacific Railroad to G. 

Watros, US DOT/VNTSC, dated March 22, 1993). 

E-2 
Appendix F. 

Current and Planned High-Speed Rail Corridors and Nuclear Power Plants 

Table F-1 shows current and planned high-speed rail corridors and the nuclear power plant locations on or 

near the rail route. 

Table F-1. Current and Planned High-Speed Rail Corridors and 

Nuclear Power Plant Locations Near Route 

High-Speed Rail Corridor 

Endpoint Cities 

Nuclear Power Plants 

On and Near Route 

Vancouver–Eugene Trojan 

Bay Area–Sacramento–Los Angeles (via valley) Humboldt, Rancho Saco, G.E. Vallacentos 

Bay Area–Los Angeles (via coast) Diablo Canyon 

Tulsa–Dallas, Little Rock–Dallas–San Antonio Arkansas, Comanche Peak, Sequoyah Fuel Co. 

Minneapolis–Chicago Monticello, Prairie Island Station, LaCrosse, Zion 

St. Louis–Chicago Dresden, Braidwood 

Detroit–Chicago Palisades, Cook 

Chicago–Toledo–Cleveland Fermi, Davis Besse, Perry 

New York City–Buffalo Ginna, Nine Mile Point, Indian Point 

Pittsburgh–Philadelphia Parks Township, Cabot, Three Mile Island, 

Limerick 

Philadelphia–Washington, D.C. Salem, Hope Creek, Shieldal, Peach Bottom 

Washington, D.C.–Richmond Surrey, North Anna 

Raleigh–Atlanta, Jessup, Savannah Harris, McGuire, Catawba, Robinson, Brunswick, 

Summer, Oconee, Vogtle, Hatch 

New Orleans–Houston Waterford 

F-1 
This Page Intentionally Left Blank 

F-2 
Appendix G. 

Energy Absorption Analysis 

Introduction 

The information contained in this appendix outlines the procedure developed to study the absorption of 

energy if a rail Spent Nuclear Fuel (SNF) cask is involved in a collision with a heavy freight locomotive. 

Three relevant collision scenarios were analyzed: a head-on collision, a transverse collision at a rail 

crossing, and a raking collision. Considerable uncertainty is associated with any collision, and the 

subsequent damage that a SNF cask may experience is extremely event- and consist-dependent. 

The purpose of developing a simplified approach to estimate energy absorption is to make a direct 

comparison of rail SNF cask responses in the rail environment for primary and secondary collision 

conditions. Primary collisions are defined as the initial contact of the rail SNF cask with a heavy piece of 

freight equipment; these analyses use a heavy freight locomotive as the object either being struck or 

striking the rail SNF cask. Rail SNF casks have historically been much stiffer than locomotives. When a 

collision occurs, momentum is exchanged, and the locomotive plastically deforms first and absorbs some 

of the initially available kinetic energy of the collision, reducing the speed of the cask. 

The speed at which the cask moves upon separation with the locomotive is defined as the cask residual 

speed. This speed is used to compare against the U.S. Nuclear Regulatory Commission (NRC) 30-ft (9.1-

m) impact into a rigid surface, which equates to 30-mph (48.2-km/hr) impact into a rigid surface. The 

secondary collision that may ensue with the surrounding rail environment is assumed to be rigid; 

therefore a direct comparison with the NRC 30-ft (9.1-m) impact into a rigid surface is an appropriate 

metric. 

Development of Equations of Motion 

The first step in the analysis is to define the system to be solved. This is a one-dimensional, lumpedparameter model of a single, bare cask striking a generic freight locomotive in a variety of orientations. 

To define independent force deflection behaviors for the crush of the locomotive and the rail SNF cask a 

dummy mass, the locomotive coupler is used to separate the response of the two objects involved in the 

collision. Figure G-1 shows a schematic of the system modeled. The stiffness of the cask is greater than 

that of the locomotive and so appears as a heavier spring in the schematic. The equations of motion for 

this system were written and solved numerically, using a standard Runge-Kutta differential equation 

solver in a MathCAD worksheet. 

Cask

x1 x3 x2

Figure G-1. Schematic of Collision Dynamic Model 

Loco

x1 x3 x2

Cask Locomotive Loco

G-1 
The equations of motion for this system are: 

mx x x k 11 1 3 && +− = ( ) cask 0 Equation G1. 

mx x x k x x k 33 3 2 && +− −− ( )( ) loco 1 3 cask = 0 Equation G2. 

mx x x k 23 3 2 && −− = ( ) loco 0 Equation G3. 

These equations were re-written as first order equations and solved simultaneously. 

Force-Deflection Characteristics 

The stiffness of the cask and locomotive were developed from the force deflection characteristics 

provided. Three force deflection diagrams were used to represent cask behavior for impacts into a rigid 

planar surface: end-wise, side-wise, and corner over the rail SNF cask center of gravity. The force 

deflection information was obtained for a generic steel-lead-steel rail Sandia National Laboratory (SNF) 

cask studied by SNL in NUREG 6672, which Figure G-2 presents. 

Figure G-2. Force Deflection of Steel-Lead-Steel Generic Rail SNF Cask for Three Impact 

Orientations at 30 mph into a Rigid Surface 

Two force deflection diagrams are used to represent a generic heavy freight locomotive for alternative 

loading paths: along the neutral axis of the underframe and for a climbing condition. The two 

locomotive force deflection characteristics were used to ascertain the sensitivity of the final, predicted 

residual speeds to the shape of the locomotive force deflection characteristics. This force deflection 

information for the locomotives was obtained from research conducted on locomotive crashworthiness, as 

shown in Figure G-3. 

G-2 
0

2000000

4000000

6000000

8000000

10000000

12000000

0 0.5 1 1.5 2 2.5 3 3.5 4

Crush (feet)

Force (lbs)

Locomotive Underframe Locomotive (Climb)

Figure G-3. Force Deflection of Heavy Freight Locomotive 

These force deflection characteristics, for the locomotive and rail SNF cask, were inputs into the lumpedparameter, collision dynamic model. Using these characteristics and defining collision scenarios of 

concern at a variety of closing speeds, an estimate of the energy absorbed in the given collision scenario 

was obtained, as well as the predicted residual velocity. The residual velocity was then used as input in 

the event trees. 

Collision Scenarios 

Three collision scenarios were developed. The first scenario is a head-on collision between the rail SNF 

cask and the locomotive. The second scenario is a transverse impact between the locomotive and the cask 

at a rail-rail crossing. The third scenario is a raking collision where the rail SNF cask has swung off the 

transport car and is fouling the right-of-way of an oncoming freight consist. Each scenario has a different 

rail SNF cask force deflection diagram. Both locomotive force deflection characteristics were also used 

to ascertain the sensitivity of the solution to the shape and magnitudes of the forces involved. Three 

examples are presented with representative results, one for each collision scenario. 

Head-On Collision Scenario 

The head-on collision scenario assumes that a bare cask (without the impact limiters) breaks free of its 

transport car and consist, at the maximum rated speed of the consist (~ 50 mph (80.4 km/hr)) and impacts 

a heavy freight locomotive traveling in the opposite direction. The cask is traveling in its longitudinal 

direction so the end-wise force deflection characteristic is used. A number of speeds are used for the 

locomotive. This example uses a locomotive speed of 70 mph (112.6 km/hr). The loading at the 

locomotive underframe neutral-axis force-deflection characteristic was used. This characteristic will 

provide the greatest deformations on the rail SNF cask. The weight of the locomotive is assumed to be 

440,000 lbs (199,581 kg). The cask weight is assumed to be 250,000 lbs (113,398 kg). To obtain the 

solution presented, 10,000 time-steps were used in the numerical integration scheme. 

Figure G-4 presents the relative displacements of the two masses as a function of time. The solid-line 

curve represents the crush of the locomotive while the dashed-line curve represents the crush of the rail 

SNF cask. The locomotive is completely crushed while the cask sustains little deformation. This result 

G-3 
means that the rail SNF cask cannot be damaged by a typical heavy freight locomotive when impacted in 

this orientation. 

0 0.1 0.2 0.3 0.4

60

40

20

0

20 0.089

− 70

Zn, 3 Zn, 1 −

Zn, 5 Zn, 3 −

0 Z 0.5 n, 0

Figure G-4. Head-On Collision Scenario: Crush of Locomotive and Rail SNF Cask 

Figure G-5 presents a plot of the velocities of the locomotive and the rail SNF cask. The solid-line curve 

represents the velocity of the locomotive while the dashed curve represents the velocity of the rail SNF 

cask. It is apparent that the force-deflection characteristic of the locomotive is exhausted due to the sharp 

change in the slope of the velocity. The time it takes to exhaust the force-deflection curve for the 

locomotive is ~ 0.4 seconds. The final cask speed is 28 mph (45.1 km/hr), and the final locomotive speed 

is 57 mph (91.7 km/hr). They are traveling in the opposite directions from one another after the event. 

This result translates into a secondary impact speed (the residual speed of the cask) with the rail 

environment of 28 mph (45.1 km/hr). If the secondary impact is assumed to be with a rigid, planar 

surface, then this residual speed can be compared against the metric obtained from the 30-ft (9.1-m) drop 

onto an unyielding surface. A drop height from 30 ft (9.1 m) equates to an initial impact speed of 30 mph 

(48.2 km/hr). Since the residual speed calculated here is less than 30 mph (48.2 km/hr), this accident 

scenario would not damage the cask sufficiently to result in emissions that exceed the allowable 

regulatory limit of 1,000 mrem/hr at 3.3 ft (1 m). The 70-mph (112.6-km/hr) speed was chosen as a good 

approximation of typical top track speed on Category 6 tracks. 

0 0.2 0.4 100

50

0

50

100 70

− 51.969

Zn, 2

3600

5280

⋅

Zn, 6

3600

5080

⋅

0 Z 0.5 n , 0

Figure G-5. Head-On Collision Scenario: Velocities of Locomotive and Rail SNF Cask 

G-4 
Rail-Rail Collision Scenario 

The rail-rail crossing-collision scenario assumes that a bare rail SNF cask without its impact limiters is 

sitting at a crossing when it is hit on its side by a locomotive freight consist. Because the cask is hit on its 

side, the side-wise force-deflection characteristic was used. A number of speeds were used for the 

locomotive. This example will use a locomotive speed of 50 mph (80.4 km/hr). The loading at the 

locomotive underframe neutral-axis force-deflection characteristic was used. This characteristic provides 

the greatest deformations on the rail SNF cask. The weight of the locomotive is assumed to be 440,000 

lbs (199,581 kg). The cask weight is assumed to be 250,000 lbs (113,398 kg). To obtain the solution 

presented, 10,000 time-steps were used in the numerical integration scheme. 

Figure G-6 presents the relative displacements, crush, of the two masses as a function of time. The solidline curve represents the crush of the locomotive while the dashed-line curve represents the crush of the 

rail SNF cask. The locomotive is crushed 19 feet, while the cask sustains very little deformation. This 

result means that the rail SNF cask cannot be damaged by a typical heavy freight locomotive when 

impacted in this orientation. 

0 0.2 0.4 0.6

20

0

10

− 30

Zn, 3 Zn, 1 −

Zn, 5 Zn, 3 −

0 Z 0.75 n , 0

Figure G-6. Rail-Rail Crossing Collision Scenario: 

Crush of Locomotive and Rail SNF Cask 

Figure G-7 presents a plot of the velocities of the locomotive and the rail SNF cask. The solid-line curve 

represents the velocity of the locomotive while the dashed curve represents the velocity of the rail SNF 

cask. The locomotive slows down from 50 mph (80.4 km/hr) to 31 mph (49.9 km/hr) as the cask is sped 

up from 0 mph (0 km/hr) to 33 mph (53 km/hr) in ~ 0.6 seconds. The cask is ejected from the locomotive 

at a slightly higher speed, but both are traveling in the same direction after the collision. 

G-5 
0 0.2 0.4 0.6 0

20

40

60 50

0

Zn, 2

3600

5280

⋅

Zn, 6

3600

5080

⋅

0 Z 0.75 n , 0

Figure G-7. Rail-Rail Crossing Collision Scenario: 

Velocities of Locomotive and Rail SNF Cask 

This result translates into a secondary impact speed (the residual speed of the cask) with the rail 

environment of 33 mph (53 km/hr). If the secondary impact is assumed to be with a rigid planar surface, 

then this residual speed can be compared against the metric obtained from the 30-ft (9.1-m) drop onto an 

unyielding surface. A drop height from 30 ft (9.1 m) equals an initial impact speed of 30 mph (48.2 

km/hr). Since the residual speed calculated here is greater than 30 mph (48.2 km/hr) this accident 

scenario could result in damage to the cask that exceeds allowable regulatory emission limits of 1,000 

mrem/hr at 3.3 ft (1 m). 

Raking Collision Scenario 

The raking collision scenario assumes that a bare rail SNF cask without its impact limiters has swung off 

its transport car and is fouling the right-of-way of an oncoming train. Because the cask was impacted on 

its corner, the corner of the cask over its center of gravity force-deflection characteristic was used. A 

number of speeds are used for the locomotive. This example will use a locomotive speed of 70 mph 

(122.6 km/hr). The loading at the locomotive underframe neutral-axis force-deflection characteristic was 

used. This characteristic will provide the greatest deformations to the rail SNF cask. The weight of the 

locomotive was assumed to be 440,000 lbs (199,581 kg). The cask weight was assumed to be 250,000 lbs 

(113,398 kg). To obtain the solution presented, 10,000 time-steps were used in the numerical integration 

scheme. 

Figure G-8 presents the relative displacements and crush of the two masses as a function of time. The 

solid-line curve represents the crush of the locomotive, and the dashed-line curve represents the crush of 

the rail SNF cask. The locomotive is fully crushed while the cask sustains very small deformations. 

Based on results presented in NUREG/CR 6672, this amount of cask deformation is not sufficient to 

cause a breach in the cask or a leak from one of the seals. There is the possibility of some loss of 

shielding, which would result in a small increase in emissions, but still within the allowable regulatory 

limit of 1,000 mrem/hr at 3.3 ft (1 m). 

G-6 
0 0.2 0.4 0.6

50

0

10

− 70

Zn, 3 Zn, 1 −

Zn, 5 Zn, 3 −

0 Z 0.75 n , 0

Figure G-8. Raking Collision Scenario: Crush of Locomotive and Rail SNF Cask 

Figure G-9 presents a plot of the velocities of the locomotive and the rail SNF cask. The solid-line curve 

represents the velocity of the locomotive while the dashed-line curve represents the velocity of the rail 

SNF cask. It was apparent when the force-deflection characteristic of the locomotive was exhausted due 

to the sharp change in the slope of the velocity. The time it took to exhaust the force-deflection curve for 

the locomotive was ~ 0.4 seconds. The final cask speed was 28 mph (45 km/hr), and the final locomotive 

speed was 57 mph (91.7 km/hr). They were traveling in the opposite directions from one another after the 

event. 

0 0.2 0.4 0.6 100

50

0

50

100 70

− 51.969

Zn, 2

3600

5280

⋅

Zn, 6

3600

5080

⋅

0 Z 0.75 n, 0

Figure G-9. Raking Collision Scenario: 

Velocities of Locomotive and Rail SNF Cask 

This result translates into a secondary impact speed (the residual speed of the cask) with the rail 

environment of 28 mph (45 km/hr). If the secondary impact was assumed to be with a rigid, planar 

surface, then this residual speed could be compared against the metric obtained from the 30-ft (9.1-m) 

drop onto an unyielding surface. A drop height from 30 ft (9.1 m) equals an initial impact speed of 30 

mph (48.2 km/hr). Since the residual speed calculated here was less than 30 mph (48.2 km/hr), this 

accident scenario would not damage the cask sufficiently to result in emissions that exceed the allowable 

regulatory limit of 1,000 mrem/hr at 3.3 ft (1 m). The 70 mph (112.6 km/hr) speed was chosen as a good 

approximation of typical top track speed on Category 6 tracks. 

G-7 
Conclusions 

The results from three sample calculations were presented. For the head-on and raking collision 

scenarios, the calculated residual speeds for the highest estimated locomotive consist traveling speed do 

not result in an extra-regulatory loading condition. This means that both scenarios would not damage the 

cask sufficiently to result in emissions that exceed the allowable regulatory limit of 1,000 mrem/hr at 3.3 

ft (1 m). The head-on rail SNF cask force deflection characteristic is sufficiently stiff that no deformation 

is expected on the cask itself, and all the energy is consumed in plastic deformations of the locomotive 

and through the exchange of momentum. The raking collision scenario does show deformations on the 

rail SNF cask. These deformations, however, are not sufficiently severe so that a breach or seal failure is 

expected and resulting emissions would not exceed the allowable regulatory limit of 1,000 mrem/hr at 3.3 

ft (1 m). The rail-rail crossing collision scenario does result in a residual speed in excess of the regulatory 

requirement and could pose a threat to the safety of the cask contents. The rail-rail crossing collision 

scenario, therefore, could result in damage to the cask that exceeds allowable regulatory emission limits 

of 1,000 mrem/hr at 3.3 ft (1 m). 

G-8 
Acronyms and Abbreviations 

AAR Association of American Railroads 

ADL Arthur D. Little, Inc. 

AEC U.S. Atomic Energy Commission 

ALARA as low as reasonably achievable 

BNSF Burlington Northern Santa Fe Railroad 

BOE Bureau of Explosives 

BTS Bureau of Transportation Statistics 

CFR Code of Federal Regulations 

CG center of gravity 

CSF commercial spent fuel 

COFC container on flatcar 

DEIS draft environmental impact statement 

DI ductile iron 

DOD U.S. Department of Defense 

DOE U.S. Department of Energy 

DOT U.S. Department of Transportation 

ECP Electronically Controlled Pneumatic 

EDE effective dose equivalents 

EIS environmental impact statement 

ERDA Energy Research and Development Administration 

FEIS Final environmental impact statement 

FRA Federal Railroad Administration 

ft foot/feet 

GRL gross rail load 

HAC Hypothetical Accident Conditions 

HAZMAT hazardous materials 

HLRW high-level radioactive waste 

HMTUSA Hazardous Materials Transportation Uniform Safety Act 

ICC Interstate Commerce Commission 

ICRP International Commission on Radiation Protection 

in inch(es) 

INEL Idaho National Engineering Laboratory 

km kilometer(s) 

km/hr kilometers per hour 

lbs pounds 

LCF latent cancer fatalities 

LNT linear, no-threshold 

LOS loss of shielding 

LPG liquefied petroleum gas 

LWR light water reactor 

m meter(s) 

mi miles 

MPC multi-purpose canister 

MPH miles per hour 

MRS monitored retrievable storage 

MTU metric tons of uranium 

MTHM metric tons of heavy metal 

173 
NCRP National Council on Radiation Protection 

NFPA National Fire Protection Association 

NHTS National Household Travel Survey 

NRC Nuclear Regulatory Commission 

NTSB National Transportation Safety Board 

NUREG Nuclear Regulations 

OCRWM Office of Civilian Radioactive Waste Management 

O-D origin-destination 

ORNL Oak Ridge National Lab 

OSHA Occupational Safety and Health Administration 

OTA Office of Technology Assessment 

PFS private fuel storage 

PHMSA Pipeline and Hazardous Materials Safety Administration 

PIH poison inhalation hazard 

PPS Package Performance Study 

PWR pressurized water reactor 

RAIRS Railroad Accident/Incident Reporting System 

RAM radioactive material 

RIA regulatory impact assessment 

RITA Research and Innovative Technologies Administration 

ROW right-of-way 

RSC Regional Services Contractor 

RSPA Research and Special Programs Administration 

SCOP Safety Compliance Oversight Plan 

SNF spent nuclear fuel 

SNL Sandia National Laboratories 

SS stainless steel 

STB Surface Transportation Board 

TI Transportation Index 

TOES train operation energy simulation 

TOFC trailer on flatcar 

UP Union Pacific Railroad 

USGS United States Geological Survey 

174 
Glossary 

Absorbed Dose. The energy imparted by ionizing radiation per unit mass of irradiated material. 

The units of absorbed dose are the rad and the gray. 

Accident. An unplanned sequence of events that results in undesirable consequences. 

Activity Mean Aerodynamic Diameter. The diameter of a unit-density sphere with the same 

terminal settling velocity in air as that of an aerosol particle the radioactivity of which is the 

median for the entire aerosol. 

Air Modes. Carriage of packages by cargo aircraft or passenger aircraft. 

Atmospheric Dispersion. Movement of a contaminant as a result of the cumulative effect of the 

wind patterns and random motions of the air. 

Atom. The smallest particle of an element that cannot be divided or broken up by chemical 

means. An atom consists of a nucleus, which contains protons and neutrons, and electrons 

that orbit the nucleus. 

Attenuation. The process by which a beam of radiation is reduced in intensity when passing 

through some material. 

Background Radiation. Radiation from cosmic sources; naturally occurring radioactive 

materials such as granite; and global fallout from nuclear testing. 

Beta Radiation. Charged particles emitted from atomic nuclei during radioactive decay. A 

negatively charged beta particle is identical to an electron. 

Buffer Cars. Railcars in front of or in back of those carrying spent nuclear fuel and high-level 

radioactive waste to provide additional distance to possibly occupied railcars or to railcars 

carrying hazardous materials other than radioactive materials. Federal regulations require 

the separation of a railcar carrying spent nuclear fuel and high-level radioactive waste from 

a locomotive, occupied caboose, carload of undeveloped film, or railcar carrying another 

class of hazardous material by at least one buffer car. These could be U.S. Department of 

Energy railcars or, in the case of general freight service, commercial railcars. 

Canister. An unshielded metal container used as: (1) a pour mold in which molten vitrified highlevel radioactive waste can solidify and cool; (2) the container in which U.S. Department of 

Energy and electric utilities place intact spent nuclear fuel, loose rods, or nonfuel 

components for shipping or storage; or (3) in general, a container used to provide 

radionuclide confinement. Canisters are used in combination with specialized overpacks 

that provide structural support, shielding, or confinement for storage, transportation, and 

emplacement. Overpacks used for transportation are usually referred to as transportation 

casks; those used for emplacement in a repository are referred to as waste packages. 

Carrier. A company engaged in the transportation of passengers or property by land or water as 

a common, contract, or private carrier, or by civil aircraft. 

Cask. A heavily shielded container that meets applicable regulatory requirements used to ship 

spent nuclear fuel or high-level radioactive waste. 

Characteristic Package Dimension. Usually the largest package dimension from among the 

package’s length, width, diameter, etc. 

Collective Dose. The sum of the individual doses received in a given period of time by a 

specified population from exposure to a specified source of radiation. 

175 
Commercial Spent Nuclear Fuel. Commercial nuclear fuel rods that have been removed from 

reactor use. See spent nuclear fuel and U.S. Department of Energy spent nuclear fuel. 

Corridor. As used in this transportation analysis, a strip of land, approximately 400-meters 

(0.25-mile) wide, that encompasses one of several possible routes through which rail 

transport spent nuclear fuel, high-level radioactive waste, and other material will pass to 

and from the proposed Yucca Mountain Repository. 

Cosmic Radiation. A variety of high-energy particles, including protons, that bombard the Earth 

from outer space. They are more intense at higher altitudes than at sea level where the 

Earth’s atmosphere is most dense and provides the greatest protection. 

Dedicated Freight Rail Service. A train that handles only one commodity (in this case, spent 

nuclear fuel or high-level radioactive waste); this separate train with its own crew would 

limit switching between trains for the railcars carrying these materials. 

Deformation. A change in the shape and size of a body. 

Dose Equivalent. (1) The number (corrected for background) zero and above that is recorded as 

representing an individual’s dose from external radiation sources or internally deposited 

radioactive materials; (2) the product of the absorbed dose in rads and a quality factor; (3) 

the product of the absorbed dose, the quality factor, and any other modifying factor. The 

dose equivalent quantity is used for comparing the biological effectiveness of different 

kinds of radiation (based on the quality of radiation and its spatial distribution in the body) 

on a common scale; it is expressed in rem. 

Dose or Radiation Dose. A quantity of radiation or energy absorbed living tissues. 

Dose Rate. The radiation dose delivered per unit of time, generally measured in millirem per 

hour. 

Dose Risk. The product of a radiation dose and the probability of its occurrence. 

Dual-purpose Canister. A metal vessel suitable for storing (in a storage facility) and shipping 

(in a shipping cask) commercial spent nuclear fuel assemblies. 

Effective Dose Equivalent. The sum of the products of the dose equivalent to the organ or tissue 

and the weighting factors applicable to each of the organs or tissues that are irradiated. 

Electron. An elementary particle with a unit negative charge. See beta radiation. 

Element. One of the 103 known chemical substances that cannot be broken down further without 

changing its chemical properties. Examples are hydrogen, nitrogen, gold, lead, and 

uranium. 

Escort Cars. Railcars in which escort personnel travel on trains carrying spent nuclear fuel or 

high-level radioactive waste. 

Evacuation. The urgent removal of people from an area to avoid or reduce high-level, short-term 

exposure, usually from an airborne plume or from deposited activity. 

176 
Exclusive Use (also referred to as sole use or full load). Sole use by a single consignor of a 

conveyance for which all initial, intermediate, and final loading and unloading are carried 

out in accordance with the direction of the consignor or consignee. The consignor and the 

carrier must ensure that any loading or unloading is performed by personnel having 

radiological training and resources appropriate for safe handling of the consignment. The 

consignor must issue specific instructions in writing, for maintenance of exclusive use 

shipment controls, and include them with the shipping paper information provided to the 

carrier by the consignor (49 CFR 173.403). 

Exposure. A measure of the ionization produced in air by X or gamma radiation; units of 

exposure in the air are the Roentgen or coulomb per kilogram (SI units). 

Exposure (to Radiation). The incidence of radiation on living or inanimate material by accident 

or intent. Background exposure is the exposure to natural ionizing radiation. Occupational 

exposure is the exposure to ionizing radiation that occurs during a person’s working hours. 

Population exposure is the exposure to a number of persons who inhabit an area. 

Fissile Material. Plutonium-238, plutonium-239, plutonium-241, uranium-233, uranium-235, or 

any combination of these radionuclides. The definition does not apply to unirradiated 

natural uranium and depleted uranium, and natural uranium or depleted uranium that has 

been irradiated in a thermal reactor. Certain additional exceptions are provided in § 

173.453 (173.403). 

Fissile Material, Controlled Shipment. Any shipment that contains one or more packages that 

have been assigned, in accordance with § 173.457, nuclear criticality control transport 

indices greater than 10 (173.403). 

Gamma Ray. The most penetrating type of radiant nuclear energy. It does not contain particles 

and can be stopped by dense materials, such as concrete or lead. See ionizing radiation. 

General Freight Rail Service. Railroad line service that uses trains that move railcars, each of 

which might contain a different commodity. Railcars carrying spent nuclear fuel or highlevel radioactive waste could be switched (in rail yards or on sidings) successively from 

one general freight train to another as they traveled from the commercial and U.S. 

Department of Energy locations to Nevada. 

Geologic Repository. A system for disposing of radioactive waste in excavated geologic media, 

including surface and subsurface areas of operation, and the adjacent part of the geologic 

setting that provides isolation of the radioactive waste in the controlled area. 

Half-Life. The time in which half the atoms of a particular radioactive substance disintegrate to 

another nuclear form. 

Heavy Metal. All uranium, plutonium, and thorium used or generated in a manmade nuclear 

reactor. 

High-Level Radioactive Waste. (1) The highly radioactive material resulting from the 

reprocessing of spent nuclear fuel, including liquid waste produced directly in reprocessing 

and any solid material derived from such liquid waste that contains fission products in 

sufficient concentrations; and (2) other highly radioactive material that the U.S. Nuclear 

Regulatory Commission, consistent with existing law, determines by rule requires 

permanent isolation. [DOE, 2002a]

Impact Limiters. Devices attached to rail shipping casks that would help absorb impact energy 

(reduce the acceleration of a package) in the event of a collision. Made of energy 

absorbing material (e.g., wood, foam, aluminum honeycomb). 

177 
Incident-Free Transportation. Routine transportation in which cargo travels from origin to 

destination without being involved in an accident. 

Ion. An atom that has too many or too few electrons, causing it to be chemically active. 

Ionizing Radiation. Any radiation capable of displacing electrons from atoms or molecules, 

thereby producing ions. This includes alpha particles, beta particles, gamma rays, X-rays, 

neutrons, high-speed electrons, high-speed protons, ultraviolet light, and other particles 

capable of producing ions. 

Irradiation. Exposure to radiation. 

Latent Cancer Fatality. A death resulting from cancer that has been caused by exposure to 

ionizing radiation. For exposures that result in cancers, the generally accepted assumption 

is that there is a latent period between the time an exposure occurs and the time a cancer 

becomes active. 

Maximally Exposed Individual. A hypothetical individual whose location and habits result in 

the highest total radiological or chemical exposure (and thus dose) from a particular source 

for all exposure routes (for example, inhalation, ingestion, direct exposure). The concept of 

the maximally exposed individual is used to evaluate potential short-term impacts to 

individuals around the repository and from transportation. The concept of the maximally 

exposed individual is used to evaluate potential short-term impacts to individuals from 

transportation. 

Metric Tons of Heavy Metal. Quantities of spent nuclear fuel without the inclusion of other 

materials, such as cladding (the tubes containing the fuel) and structural materials. A metric 

ton is 1,000 kilograms (1.1 tons or 2,200 pounds). Uranium and other metals in spent 

nuclear fuel (such as thorium and plutonium) are called heavy metals because they are 

extremely dense; that is, they have high weights per unit volume. 

Millirem. One one-thousandth (0.001) of a rem. 

Mitigation. Actions and decisions that (1) avoid impacts altogether by not taking a certain action 

or parts of an action; (2) minimize impacts by limiting the degree or magnitude of an 

action; (3) rectify the impact by repairing, rehabilitating, or restoring the affected 

environment; (4) reduce or eliminate the impact over time by preservation and maintenance 

operations during the life of the action; or (5) compensate for an impact by replacing or 

providing substitute resources or environments. 

Naval Spent Nuclear Fuel. Spent nuclear fuel discharged from reactors in surface ships, 

submarines, and training reactors operated by the U.S. Navy. 

Nuclear Waste. Unusable by-products of nuclear power generation, nuclear weapons 

production, and research, including spent nuclear fuel and high-level radioactive waste. 

Occupational Dose. The dose received by an individual in a restricted area or in the course of 

employment in which the individual’s assigned duties involve exposure to radiation and to 

radioactive material from licensed and unlicensed sources of radiation, whether in the 

possession of the licensee or other person. 

Package. Packaging and its radioactive contents. 

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Packaging. The assembly of components necessary to ensure compliance with packaging 

requirements. It may consist of one or more receptacles, absorbent materials, spacing 

structures, thermal insulation, radiation shielding, and devices for cooling or absorbing 

mechanical shocks. The vehicle, tie-down system, and auxiliary equipment may be 

designated as part of the packaging. 

Person-Rem. A unit used to measure the radiation exposure to an entire group and to compare 

the effects of different amounts of radiation on groups of people; it is the product of the 

average dose equivalent (in rem) to a given organ or tissue multiplied by the number of 

persons in the population of interest. 

Photon. A quantum (or packet) of energy emitted in the form of radiation. Gamma rays and Xrays are examples of photons. 

Point Source. Ideally, a source with infinitesimal dimensions. Practically, a source of radiation 

the dimensions of which are small compared with the viewing distance. 

Population Dose. A summation of the radiation doses received by individuals in an exposed 

population; equivalent to collective dose and expressed in person-rem. 

Pressurized Water Reactor. A nuclear power reactor in which heat is transferred from the core 

to a heat exchanger by high-temperature water kept under high pressure. 

Private Fuel Storage. Privately owned temporary site for the storage of spent nuclear fuel.

Probability. The relative frequency at which an event can occur in a defined period. Statistical 

probability is about what actually happens in the real world and can be verified by 

observation or sampling. Knowing the exact probability of an event is usually limited by 

the inability to know, or compile the complete set of, all possible outcomes over time or 

space. Probability is measured on a scale of 0 (event will not occur) to 1 (event will occur). 

Public Dose. The population dose received by members of the public from exposure to radiation 

and to radioactive material. It does not include occupational dose. 

Qualitative. With regard to a variable, parameter, or data, an expression or description of an 

aspect in terms of non-numeric qualities or attributes. See quantitative. 

Quantitative. Numeric expression of a variable. See qualitative. 

Rad. The unit of measure of absorbed radiation dose in terms of energy. One rad is equal to an 

absorbed dose of 100 ergs per gram or 0.01 J per kg (0.01 gray). (In the metric system of 

measurements, an erg is a unit of energy. One foot-pound is equal to 13,560,000 ergs.) 

Radiation. The emitted particles or photons from the nuclei of radioactive atoms. Some 

elements are naturally radioactive; others are induced to become radioactive by irradiation 

in a reactor. Naturally occurring radiation is indistinguishable from induced radiation. 

Radiation (Ionizing Radiation). Alpha particles, beta particles, gamma rays, X-rays, neutrons, 

and other particles capable of producing ions. 

Radiation Level. The radiation dose-equivalent rate expressed in millisievert(s) per hour or 

mSv/h (millirem(s) per hour or mrem/h) (49 CFR Part 173.403). 

Radioactive. Emitting/Exhibiting radioactivity. 

Radioactive Decay. The process in which one radionuclide spontaneously transforms into one or 

more different radionuclides, which are called decay products. 

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Radioactivity. The property possessed by some elements (for example, uranium) of 

spontaneously emitting alpha, beta, or gamma rays by the disintegration of atomic nuclei. 

Radioisotope. An unstable isotope of an element that decays or disintegrates spontaneously, 

emitting radiation. 

Radionuclide. A general term referring to all known unstable or radioactive isotopes of a 

chemical. 

Rail Classification Yard. A railroad switching yard where railcars arriving in inbound freight 

trains are classified and reassembled according to their routing to make up outbound freight 

trains. 

Rail Route. Route from point of origin to the repository. 

Receptor. A hypothetical person who is exposed to environmental contaminants (in this case 

radionuclides) in such a way—by a combination of factors including location, lifestyle, 

dietary habits, etc.—that this individual is representative of the exposure of the general 

population. U.S. Department of Energy used this hypothetical individual to evaluate longterm repository performance. The receptor represents the “Reasonably Maximally Exposed 

Individual (RMEI),” defined in 40 CFR Part 197. 

Rem. A unit of dose equivalent. 

Repository. See geologic repository. 

Risk. The product of the probability that an undesirable event will occur, multiplied by the 

consequences of the undesirable event. 

Shielding. Any material that provides radiation protection. 

Shipment. The movement of a properly prepared (loaded, unloaded, or empty) cask from one 

site to another and associated activities to ensure compliance with applicable regulations. 

Shipping Cask. A heavily shielded massive container that meets regulatory requirements for 

shipping spent nuclear fuel or high-level radioactive waste. See cask. 

Single-purpose (Storage or Transportation) Cask. A heavily shielded massive container for 

the dry storage of spent nuclear fuel; it is usable for either storage or transportation but not 

for emplacement in a repository. See cask. 

Spent Nuclear Fuel. Fuel that has been withdrawn from a nuclear reactor following irradiation, 

the constituent elements of which have not been separated by reprocessing. [DOE, 2002a].

Storage. The collection and containment of waste or spent nuclear fuel in a way that does not 

constitute disposal of the waste or spent nuclear fuel for the purposes of awaiting treatment 

or disposal capacity. 

Total Population. The sum of all people associated with direct and indirect exposure. 

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Transport Index. The dimensionless number (rounded up to the next tenth) placed on the label 

of a package to designate the degree of control to be exercised by the carrier during 

transportation. The transport index is determined as follows: (1) for non-fissile material 

packages, the number determined by multiplying the maximum radiation level in 

milliSievert(s) per hour at 3.3 ft (1 m) from the external surface of the package by 100 

(equivalent to the maximum radiation level in millirem per hour at 3.3 ft (1 m)); or (2) or 

fissile material packages, the number determined by multiplying the maximum radiation 

level in milliSievert per hour at 3.3 ft (1 m) from any external surface of the package by 

100 (equivalent to the maximum radiation level in millirem per hour at 3.3 feet (1 m)) or, 

for criticality control purposes, the number obtained by dividing 50 by the allowable 

number of packages which may be transported together, whichever number is larger (10 

CFR Part 71.4/49 CFR 173.403). 

Transuranic Waste. Waste materials (excluding high-level radioactive waste and certain other 

waste types) contaminated with alpha-emitting radionuclides that are heavier than uranium 

with half-lives greater than 20 years and that occur in concentrations greater than 100 

nanocuries per gram. Transuranic waste results primarily from treating and fabricating 

plutonium, as well as research activities at U.S. Department of Energy defense installations.

U.S. Department of Energy Spent Nuclear Fuel. Radioactive waste created by defense 

activities that consists of more than 250 different waste forms. The major contributor to 

this waste form is the N-Reactor fuel currently stored at the Hanford Site. This waste form 

also includes 65 metric tons of heavy metal of naval spent nuclear fuel. 

Vitrification. A waste treatment process that uses glass (for example, borosilicate glass) to 

encapsulate or immobilize radioactive wastes. 

X-Rays. Penetrating electromagnetic radiation having a wavelength much shorter than that of 

visible light. X-rays are identical to gamma rays but originate outside the nucleus, either 

when the inner orbital electrons of an excited atom return to their normal state or when a 

metal target is bombarded with high-speed electrons. 

Yucca Mountain Site. The area on which U.S. Department of Energy has built or would build 

the majority of facilities or cause the majority of land disturbances related to the proposed 

repository. 

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