POLICY ISSUE

NOTATION VOTE

July 27, 2004 SECY-04-0135

FOR: The Commissioners

FROM: Luis A. Reyes

Executive Director for Operations

SUBJECT: DEMONSTRATION TEST PLAN FOR FULL-SCALE SPENT

NUCLEAR FUEL RAIL TRANSPORTATION CASK TESTING

UNDER THE PACKAGE PERFORMANCE STUDY (WITS 200400069)

PURPOSE:

(1) To request the Commission’s approval of the staff’s proposed plan for a full-scale

demonstration test of a spent nuclear fuel transportation cask and to describe the basis

for the staff’s recommendation.

(2) To inform the Commission of the staff’s interactions with the U.S. Department of Energy

(DOE) concerning potential funding for the Package Performance Study (PPS).

BACKGROUND:

Over the past 25 years, the staff of the U.S. Nuclear Regulatory Commission (NRC), Office of

Nuclear Regulatory Research (RES), has conducted (or sponsored) and published a series

of studies assessing the risks associated with transporting spent nuclear fuel. The latest of 

CONTACT: Bret A. Tegeler, RES/DET/ERAB

 (301) 415-6793
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these studies, known as the Package Performance Study (or PPS), proposed a full-scale test

to demonstrate the robustness of spent nuclear fuel transportation casks. This confirmatory

research study is grounded in an enhanced public participatory process.

In February 2003, the staff published NUREG-1768, “Package Performance Study Test Protocols,”

which documented a proposed plan for performing extra-regulatory impact and fire tests (i.e., testing

beyond the regulatory criteria) on certified rail and truck spent fuel transportation casks. Through

extensive public meetings and comments, a wide range of stakeholders provided input for staff

consideration of how the test should be conducted. On the basis of that input, the staff identified

additional testing approaches and developed a Commission Paper (SECY-04-0029),

dated February 23, 2004, which summarized the major public comment themes and presented

testing options for the Commission’s review and approval.

In response to SECY-04-0029, the Commission issued a Staff Requirements Memorandum

(SRM), dated May 11, 2004, in which the Commission approved the testing of a full-scale,

certified rail cask of a type that is currently being used, or is expected to be used in

the foreseeable future to transport spent fuel. The Commission also directed the staff

to commence procurement of such a cask and, prior to publishing a request for bids, inform

the Commission of the specific details of the cask design and the related justification. 

The staff provided that information in a memorandum to the Chairman, dated July 2, 2004,

requesting authorization to enter into a procurement exceeding $3 million.

Additionally, the SRM for SECY-04-0029 directed the staff to submit, for Commission approval,

a plan for a demonstration test with sufficient instrumentation to collect data to confirm

the validity of key analytical methods and assumptions, including scaling. In particular,

the Commission specified that the demonstration test should be realistically conservative

and should include exposure to a fully engulfing fire. The Commission further directed the staff

to interact with DOE to determine whether the Department will provide funding for

the demonstration test and to inform DOE that the PPS could be expanded in the future

to include testing of a certified truck cask.

DISCUSSION:

The staff’s process for developing a demonstration test plan involved (1) assessing statistics

for rail transportation accidents involving both traditional commerce shipments and shipments

of spent fuel transportation casks, (2) evaluating potential “realistic” accident scenarios

to identify those that could result in a “realistically conservative” challenge to a spent fuel rail

transportation cask, (3) developing a test plan that is consistent with the direction provided

by the Commission, and (4) assessing the uncertainties in the test plan and the degree

to which it would satisfy the Commission’s direction.

Rail Transportation Accident Statistics

Over the past 25 years, NRC-certified packages have been used in 1,300 spent fuel shipments,

and none of those shipments has challenged a rail transportation cask. Moreover, since 1970,

there have been only four rail accidents involving trains transporting casks (only one of the four

involved a train carrying loaded spent fuel casks), and none of those accidents directly involved the
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rail casks. Consequently, the staff was not able to draw directly upon accident statistics to develop

a “realistic” accident scenario that could result in a “realistically conservative” challenge to a

spent fuel rail transportation cask.

The staff, therefore, also reviewed accident reports prepared by the Federal Railroad

Administration (FRA), transportation studies conducted by Lawrence Livermore National

Laboratory and Sandia National Laboratories, and research conducted by the Volpe Center

of the U.S. Department of Transportation (DOT). Those resources support the conclusion

that there is generally fewer than 1 rail accident per 10 million railcar-kilometers traveled.

These data indicate that train accident scenarios with the highest conditional probabilities,

relative to other types of train accidents, are train derailments resulting in impacts or collisions

with soil, roadbeds, rock, structures, railcars or locomotives, and/or vehicles at railroad

crossings. Moreover, the great majority of these accidents would not be sufficiently severe

to damage a cask. The staff, therefore, considered the following hypothetical cask and railcar

accident derailment scenarios:

(1) cask and railcar impact with a rock outcrop

(2) cask and railcar impact with a tunnel entrance

(3) cask and railcar impact with a bridge abutment

(4) collision of a locomotive and a cask (attached to a railcar)

Potential Realistic Accident Scenarios

For train derailment scenarios involving impacts with rock outcrops, transportation studies

indicate that only a small percentage of the ground adjacent to commercial railroad right-of-ways

involves “hard rock.” Depending on impact speed and cask mass, hard rock is the only

impact surface capable of behaving like an unyielding surface. All other soil types would

absorb significant energy before imparting energy to the cask. Thus, derailment scenarios

involving rock surfaces are deemed to be of relatively low probability, and the more likely

impacts with soil are judged to be unlikely to challenge cask integrity.

Derailment scenarios involving an impact of the cask and its conveyance (rail car)

into a tunnel entrance or bridge abutment are more likely events. However, a unique set of

circumstances would have to occur for the cask to directly impact either a tunnel entrance or

bridge abutment. The staff, therefore, concluded that while these types of derailment scenarios

are more likely than other scenarios, they do not represent a “realistically conservative”

challenge to cask integrity (i.e., not much kinetic energy is transferred to the cask).

The staff then considered accident scenarios that involve a collision of a locomotive and a cask

(attached to a railcar). This general class of accident is a more likely scenario in the relative

ranking of these low-probability events, and the staff concluded that such a scenario could

represent a “realistically conservative” challenge in that it would have the potential to impart

enough energy into the cask to challenge cask integrity. In fact, the British used this accident 

scenario in “Operation Smash-Hit,” the well-known demonstration test conducted by the United

Kingdom’s Central Electricity Generating Board (CEGB) in 1984. Specifically, this test involved
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the high-speed impact of a locomotive into a rail cask attached to a rail car at approximately

160 kph (100 mph).

FRA accident reports indicate that locomotive impacts into railcars have occurred in the past. 

In particular, a 1995 accident that involved three trains (one of which was stopped and

was impacted at low speed by a second train) resulted in a derailment of a railcar

which overturned onto an adjacent track and was subsequently struck by a third train

at relatively high speed. For these reasons, the staff chose to develop a test plan

based on this accident scenario.

Demonstration Test Plan

The staff proposes to conduct a demonstration test involving the collision of a locomotive and a

rail cask attached to a railcar. The proposed test scenario is based on the aforementioned 1995

rail accident, but adds a fully engulfing fire as directed by the Commission. The staff notes that the

probability of occurrence of a real-world accident with a spent nuclear fuel cask similar to the

proposed demonstration test scenario is small. NRC requires that spent fuel transportation casks

be designed to survive a sequence of tests including a 30 foot drop onto an unyielding surface. 

This is a very severe test for spent fuel cask designs, and encompasses an extremely high

fraction (well over 99%) of vehicle impacts at high speed. Only the most severe, incredible

accidents might challenge a cask design, but their likelihood is so remote that the NRC considers

the risk to public health acceptably low. The proposed demonstration test involves the following

events:

1. A “typical” spent fuel transportation cask will be affixed to a rail car, and the cask-rail car

assembly will be placed across railroad tracks to simulate a realistic derailment.

2. A locomotive with a realistic mass of trailing cars will impact the cask-car assembly

at a “realistically conservative” speed. The 1995 accident that the staff has used

as a basis involved an impact speed of approximately 80 kph (50 mph); however,

the Commission’s direction suggested a speed of 120 kph (75 mph). The staff believes

that further assessment is warranted to define an appropriate “realistically conservative” impact

speed.

3. The cask, railcar, and locomotive will be fully instrumented with accelerometers,

displacement transducers, strain gauges, thermocouples, and other similar devices

to collect data for comparison with pre- and post-test analyses. Subsequent to

the locomotive impact, the test progress will be halted so that the cask

can be inspected to determine its post-impact condition.

4. Following the post-impact evaluation, a fire exposure test will be conducted. The staff

considered two options for the fire exposure test. The first option is consistent with

the Commission’s direction to include exposure to a “fully engulfing” fire. The second 

option would involve a more realistic scenario, but would be significantly more difficult

to define and conduct.
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(a) This option would include a fully engulfing fire exposure test, in which the cask

would be removed from the “flat” car and placed on a test stand in a fire test pit. 

This test would be consistent with a fully engulfing, optically dense hydrocarbon fire

of a 30-minute duration, as specified in Title 10, Section 71.73, of the Code of

Federal Regulations (10 CFR 71.73)

(b) The second option for conducting a fire exposure test would involve constructing

a “pit” around and under the cask-car assembly at its post-impact location. 

The car-cask assembly would be exposed to a hydrocarbon fire that surrounds

the assembly in a realistic setting, for a duration of least 30 minutes. (The staff

has not yet fully developed the specifics of this scenario.) The “realism”

underlying this option is that hydrocarbon fuel from the locomotive or another tanker

car could leak into a “gouged” trench in the ground or a natural low spot in the

terrain, and then ignite and burn for an unspecified period of time. However, the

cask would be shielded by the tracks and the flat car, resulting in a less severe

fire exposure than in option 4a. Additionally, the test conditions and boundary

conditions would be extremely difficult to characterize or control and, therefore,

would result in a fire exposure test of a severity that cannot reasonably be

predicted or controlled; it could only be measured and assessed after the test.

The staff’s recommendation is to conduct the fully engulfing fire exposure test defined

in option 4a, because this option is consistent with the Commission’s direction and constitutes

a “conservative” post-impact fire exposure test with well-controlled conditions.

Uncertainties in the Test Plan

The test proposed by the staff will demonstrate the robustness of a certified spent fuel

transportation cask in the event of an accident (which is very unlikely and severe ) involving a fully

engulfing fire. However, by virtue of being “realistic,” the test is more complex than the relatively

straightforward testing used in the certification process defined by 10 CFR 71.73. This complexity

introduces a number of uncertainties, stemming largely from the anticipated nonlinear nature of

the collision between the locomotive and the cask-car assembly. Additionally, the staff has not

yet finalized certain aspects of the test design(impact speed and orientation of the cask-car

assembly relative to the tracks, for example) that could have a significant effect on the test and

its challenge to cask integrity.

The associated analysis predictions and testing conditions also introduce uncertainties into

the demonstration test. Analysis predictions strongly depend upon the accurate representation

of material properties and structural details of the cask, rail car, and locomotive. Because such

details may be difficult to obtain, the staff will rely on engineering judgment and approximations

to compensate for the anticipated lack of detailed design drawings. These uncertainties

and reliance on engineering judgment and approximations will increase the error bounds

in predicting the test results, and will increase the uncertainty in key parameters to be measured

during the test, thereby requiring an increase in the measurement range for those parameters.

In the SRM for SECY-04-0029, the Commission directed the staff to design a demonstration test

with “sufficient instrumentation to collect data which confirms the validity of appropriate key analytical
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methods and assumptions, including scaling methodology, that serve as the basis for NRC

regulations and regulatory review of transportation cask applications.” The Commission’s direction

to confirm the validity of the scaling methodology will not be achievable in the context of

traditional engineering analysis validation from the demonstration impact test. In this traditional

context, validation of the scaling methodology would involve comparing analysis results with

the results of two or more well-defined experiments. These validation experiments require wellcontrolled boundary conditions in order to limit uncertainties in interpreting test data regarding

component response. The boundary conditions for the demonstration impact test are complex

and not well-controlled for several reasons, including the uncertain behavior of the crushing of

the locomotive and railcar, uncontrollable friction effects between the cask, rail car, and the

ground, as well as the failure strength of the cask tie-downs.

What the Demonstration Test Can Accomplish

A full-scale demonstration test that is sufficiently instrumented can provide a clear demonstration

of cask robustness under realistic accident conditions, data that can be used in assessing the

ability of current analysis techniques to predict cask response under complex impact conditions,

and data that can be used to assess thermal analysis methods applicable to the fully engulfing fire

test.

Full-scale impact and fire demonstration tests on spent nuclear fuel rail transportation casks have

not been conducted in the past 20 years. Past rail cask demonstration tests have involved lighter,

lower capacity designs, which would not likely be used in the foreseeable future to transport spent

fuel. Conducting a full-scale, realistically conservative test can demonstrate the robustness of a

cask design that is likely to be used in shipments of spent fuel. The proposed demonstration

impact test will provide this demonstration. The proposed fully engulfing fire test will demonstrate

the integrity of the full-scale rail cask in a severe thermal event. 

The instrumentation that is expected to be used in the proposed test (consisting of

accelerometers, displacement transducers, thermocouples, and strain gauges, combined with a

state-of-the-art data acquisition system) will provide data not available from prior tests. The

specific types of instruments, their locations on the test cask, rail car, and locomotive, and the

anticipated ranges of parameters to be measured will be determined through pre-test predictions

of the impact and fire tests. An initial assessment of the instrumentation package and ranges of

parameters will be provided to the Commission six months after the Commission approves the

test plan. The staff expects that the details of the instrumentation package will evolve somewhat

as more detailed pre-test analyses are completed, and any significant evolution in the

instrumentation package will be reported to the Commission. 

Earlier methods for analyzing cask response in full-scale demonstration tests involved lumped

parameter mathematical models, two-dimensional (2D) finite element analysis, and coarse threedimensional (3D) finite element analysis. For the proposed tests, the staff plans to use modern

analysis techniques, such as those used in the current cask certification process. These modern

analysis techniques take advantage of more efficient, state-of-the-art, computing capabilities and

the development of high-fidelity 3D finite element models. These models allow for more accurate

representation of cask structural details and material characteristics involved in a realistic accident

scenario that is indeed three-dimensional.
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In addition, the staff expects to develop a collaborative analysis effort (e.g., round-robin

participation) with domestic and international stakeholders who are expected to use a wide

variety of analytical tools and modeling techniques. By performing both pre- and post-test

analyses, the collaborative analysis effort is expected to yield insights into the most accurate

modeling techniques for both the impact and fire tests. Prior experience with such collaboration

has shown that all of the participants gain valuable experience and insights into conducting

analyses of complex structure and loading conditions.

DOE Interaction

The staff is continuing to interact with DOE to determine whether the Department will provide

funding for the PPS demonstration test. On June 10, 2004, the staff met with representatives

from the DOE Office of National Transportation to discuss the potential use of truck casks

in PPS testing. DOE is currently evaluating the potential use of truck casks and will keep us

apprised. The staff is also exploring the possibility of DOE contributing funding for

the purchase of a rail cask.

RESOURCES:

Resources necessary to support the Package Performance Study are currently being

addressed and will be finalized once the Commission renders its decision on the proposed test

plan.

COORDINATION:

The Office of the General Counsel has reviewed this paper and has no legal objections. 

The Office of the Chief Financial Officer has also reviewed this paper for resource implications

and has no objections.

RECOMMENDATION:

The staff recommends that the Commission should approve the proposed PPS demonstration

test plan. Upon receipt of the Commission’s approval, the staff will develop comprehensive

test metrics and commence analysis predictions of key cask performance measurements

for estimating instrumentation gauge range and later comparison with test data. The staff

will continue to interact with DOE regarding the contribution of funds for the PPS

and the future use of truck casks for transporting spent fuel.

/RA Martin J. Virgilio Acting For/

Luis A. Reyes

Executive Director

 for Operations
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In addition, the staff expects to develop a collaborative analysis effort (e.g., round-robin participation) with

domestic and international stakeholders who are expected to use a wide variety of analytical tools and

modeling techniques. By performing both pre- and post-test analyses, the collaborative analysis effort is

expected to yield insights into the most accurate modeling techniques for both the impact and fire tests. 

Prior experience with such collaboration has shown that all of the participants gain valuable experience

and insights into conducting analyses of complex structure and loading conditions.

DOE Interaction

The staff is continuing to interact with DOE to determine whether the Department will provide funding for

the PPS demonstration test. On June 10, 2004, the staff met with representatives from the DOE Office of

National Transportation to discuss the potential use of truck casks in PPS testing. DOE is currently

evaluating the potential use of truck casks and will keep us apprised. The staff is also exploring the

possibility of DOE contributing funding for the purchase of a rail cask.

RESOURCES:

Resources necessary to support the Package Performance Study are currently being addressed and will

be finalized once the Commission renders its decision on the proposed test plan.

COORDINATION:

The Office of the General Counsel has reviewed this paper and has no legal objections. The Office of

the Chief Financial Officer has also reviewed this paper for resource implications and has no objections.

RECOMMENDATION:

The staff recommends that the Commission should approve the proposed PPS demonstration test plan. 

Upon receipt of the Commission’s approval, the staff will develop comprehensive test metrics and

commence analysis predictions of key cask performance measurements for estimating instrumentation

gauge range and later comparison with test data. The staff will continue to interact with DOE regarding

the contribution of funds for the PPS and the future use of truck casks for transporting spent fuel.

/RA Martin J. Virgilio Acting For/

Luis A. Reyes

Executive Director

 for Operations

DISTRIBUTION: Andrew Murphy, RES, Amy Snyder, NMSS, Robert Lewis, NMSS, Larry Camper, NMSS, 

Margaret Federline, NMSS, Robin Baum, OGC

DET r/f and MEB r/f RES 2004199; WITS 200400069

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*SEE PREVIOUS CONCURRENCE

OFFICE Tech. Editor N ERAB/DET ERAB/DET DET

NAME P. Garrity B. Tegeler* M. Evans* M. Mayfield*

DATE 7/22/04 7/21/04 7/22 /04 7/22/04

OFFICE NMSS NMSS OGC OCFO

NAME W. Brach* J. Strosnider* K. Cyr* J. Funches*

DATE 7/23/04 7/23/04 7/21/04 7/23/04

OFFICE RES DEDMRS EDO

NAME C. Paperiello* M. Virgilio L. Reyes

DATE 7/23/04 7/ 27 /04 7/ 27 /04

OFFICIAL RECORD COPY