ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller & Associates I MJW Corporation

Page 1 of 26

Document Title:

Occupational Onsite Ambient Dose 

Reconstruction for DOE Sites

Document Number: ORAUT-PROC-0060

Revision: 01

Effective Date: 06/28/2006

Type of Document: Procedure

Supersedes: Revision 00

Subject Expert: Robert C. Winslow

Document Owner

Approval: Signature on File Approval Date: 05/11/2006

James P. Griffin, Deputy Project Director

Concurrence: Signature on File Concurrence Date: 05/22/2006

Kate Kimpan, Project Director

Approval: Signature on File Approval Date: 06/28/2006

Stuart L. Hinnefeld, Health Science Administrator

 New Total Rewrite Revision Page Change

FOR DOCUMENTS MARKED AS A TOTAL REWRITE, REVISION, OR PAGE CHANGE, REPLACE THE PRIOR 

REVISION AND DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 2 of 26

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION

NUMBER DESCRIPTION

03/07/2005 00 New document to provide direction for external onsite ambient dose 

reconstruction for DOE sites. Incorporates internal and NIOSH 

formal review comments. First approved issue. Initiated by Steven E. 

Merwin. 

06/28/2006 01 Revised document to include additional DOE sites. Incorporates 

formal internal and NIOSH review comments. Constitutes a total 

rewrite of the document. Training required: as determined by the 

Task Manager. Initiated by Robert C. Winslow.
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 3 of 26

TABLE OF CONTENTS

SECTION TITLE PAGE

1.0 PURPOSE ..................................................................................................................................4

2.0 SCOPE .......................................................................................................................................4

3.0 REFERENCES ...........................................................................................................................4

4.0 RESPONSIBILITIES...................................................................................................................5

5.0 GENERAL...................................................................................................................................5

6.0 PROCEDURE.............................................................................................................................8

6.1 Review the Information Provided in the Case File ..........................................................8

6.2 Maximizing Methodology.................................................................................................8

6.3 Best Estimate Methodology ............................................................................................9

6.4 Minimizing Methodology................................................................................................10

7.0 RECORDS................................................................................................................................10

8.0 APPLICABLE DOCUMENTS....................................................................................................10

8.1 Drivers...........................................................................................................................10

8.2 Forms ............................................................................................................................10

9.0 DEFINITIONS AND ACRONYMS.............................................................................................10

ATTACHMENT A, EXTERNAL ONSITE AMBIENT DOSE ASSIGNMENT FOR 

MONITORED SITE EMPLOYEES......................................................................... 14

ATTACHMENT B, MAXIMIZING DOSE SUMMARY........................................................................... 15

ATTACHMENT C, METHODS FOR ASSIGNING SITE-SPECIFIC BEST 

ESTIMATES OF EXTERNAL ONSITE AMBIENT DOSES ................................... 20
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 4 of 26

1.0 PURPOSE

The purpose of this procedure is to provide direction to the Oak Ridge Associated Universities 

(ORAU) Team Dose Reconstructors for the assignment of external dose from onsite ambient 

radiation for the National Institute for Occupational Safety and Health (NIOSH) Energy 

Employees Occupational Illness Compensation Program Act (EEOICPA) dose reconstruction 

project. This procedure relies upon information contained in site technical basis documents 

(TBDs), and it supersedes the instructions pertaining to external onsite ambient dose 

reconstruction in ORAUT-PROC-0006.

2.0 SCOPE

This procedure applies to NIOSH technical support contractors involved in performing dose 

reconstruction for covered employees of the U.S. Department of Energy (DOE), its 

predecessor agencies, and certain of its contractors and subcontractors.

3.0 REFERENCES

OCAS-IG-001, External Dose Reconstruction Implementation Guideline

ORAUT-PROC-0006, External Dose Reconstruction

ORAUT-TKBS-0003, Savannah River Site

ORAUT-TKBS-0006-4, Technical Basis Document for the Hanford Site – Occupational 

Environmental Dose

ORAUT-TKBS-0007-4, Technical Basis Document for the Idaho National Engineering and 

Environmental Laboratory (INEEL) – Occupational Environmental Dose

ORAUT-TKBS-0008-4, Technical Basis Document for the Nevada Test Site – Occupational 

Environmental Dose

ORAUT-TKBS-0009-4, Technical Basis Document for the K-25 Site – Occupational 

Environmental Dose

ORAUT-TKBS-0010-4, Technical Basis Document for the Los Alamos National Laboratory –

Occupational Environmental Dose

ORAUT-TKBS-0011-4, Technical Basis Document for the Rocky Flats Plant – Occupational 

Environmental Dose

ORAUT-TKBS-0012-4, Technical Basis Document for the Oak Ridge National Laboratory –

Occupational Environmental Dose

ORAUT-TKBS-0013-4, Technical Basis Document for the Pantex Plant – Occupational 

Environmental Dose

ORAUT-TKBS-0014-4, Technical Basis Document for the Y-12 National Security Complex –

Occupational Environmental Dose
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 5 of 26

ORAUT-TKBS-0015-4, Technical Basis Document for the Portsmouth Gaseous Diffusion Plant 

– Occupational Environmental Dose

ORAUT-TKBS-0016-4, Technical Basis Document for the Mound Site – Occupational 

Environmental Dose

ORAUT-TKBS-0017-4, Technical Basis Document for the Fernald Environmental Management 

Project (FEMP) – Occupational Environmental Dose

ORAUT-TKBS-0019-4, Technical Basis Document for the Paducah Gaseous Diffusion Plant –

Occupational Environmental Dose

ORAUT-TKBS-0026-6, Technical Basis Document for the Argonne National Laboratory – West 

– Occupational External Dose

ORAUT-TKBS-0029-4, Pinellas Plant – Occupational Environmental Dose

ORAUT-TKBS-0031, Site Profile for the Kansas City Plant

ORAUT-TKBS-0035-4, Lawrence Livermore National Laboratory – Occupational 

Environmental Dose

Crystal Ball, Decisioneering Inc., Denver, CO.

4.0 RESPONSIBILITIES

Principal External Dosimetrist – As the Subject Expert, revises this procedure as necessary 

based on revised or new information in TBDs.

Task 3 Manager – Advises the Principal External Dosimetrist of impending revisions to the 

TBDs or issues that might render information inaccurate in approved TBDs.

Task 5 Group Leaders – Inform the Principal External Dosimetrist of issues with 

implementation of this procedure identified by Dose Reconstructors or Peer Reviewers.

Dose Reconstructors – Inform their Task Group Leader of issues with implementation of this 

procedure identified during the course of performing dose reconstructions.

Peer Reviewers – Inform their Task Group Leader of issues with implementation of this 

procedure identified during the course of performing peer reviews.

5.0 GENERAL

As described in OCAS-IG-001, doses from elevated background radiation must be included in 

dose reconstructions performed under this program. This requirement is complicated by site 

reporting practices, fallout from atmospheric weapons testing, and worker location in relation 

to the site monitoring data. Since these exposures are a concern for energy employees who 

were not monitored or who worked at a site where elevated background radiation might have 

been subtracted from dosimeter results, reconstruction of doses must rely upon information 
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 6 of 26

provided in site-specific TBDs, technical information bulletins, and other published health 

physics resources.

External dosimeters using film or thermoluminescent dosimeters (TLDs) have been used for 

occupational radiation monitoring since the 1940s. To account for background radiation 

levels, which are not traditionally included in occupational radiation dose records, control 

dosimeters have been used from the outset. Good radiation protection practice dictates that, 

during shipment, a control dosimeter accompany each batch of dosimeters issued to workers. 

Between manufacture (or annealing) and issuance, and between retrieval and processing, 

each shipment of dosimeters is irradiated by natural cosmic and terrestrial radiation sources, 

and potentially inadvertently irradiated by other sources. The function of the control dosimeter 

is to measure all nonoccupational radiation exposure to the batch of dosimeters. On 

processing, the reading from the control dosimeter is subtracted from the reading of each of 

the other dosimeters in the batch, yielding a result for each dosimeter that is uniquely due to 

occupational radiation exposure. Note that the subtraction could occur with raw data, such as 

optical density readings for film or glow curves, or with transformed data, such as exposures in 

roentgens, absorbed doses in rads or grays, or dose equivalents in rems or sieverts. 

Determination as to whether control dosimeters were exposed to elevated ambient levels of 

external radiation (EALER) is generally associated with where the control dosimeters were 

stored. From the intended use of control dosimeters, it is clear that controls should be 

subjected to exactly the same nonoccupational radiation exposure as the issued dosimeters, 

and differ only in the occupational component. The implementation of this intention, that is, 

procedures for issuance and retrieval of dosimeters, likely differed over time within a given 

facility and certainly differed among various DOE and Atomic Weapons Employer (AWE) sites. 

For example, at large facilities like Hanford, the Idaho National Engineering and Environmental 

Laboratory (INEEL), Los Alamos National Laboratory (LANL), and Savannah River Site (SRS), 

controls might have been kept at a central dosimeter location, or distributed with batches of 

dosimeters to remote identification (ID) badge/dosimeter exchange buildings such as guard 

stations near reactors, reprocessing facilities, or manufacturing facilities. During some 

periods, dosimeters were incorporated into ID badges to ensure that no one entered without a 

dosimeter, and these ID badges were picked up at the entrance station at the beginning of 

each shift, and turned in there at the end of each shift. If control dosimeters were kept at 

remote exchange facilities, they would have recorded elevated ambient levels of external 

radiation at those facilities. Such doses from EALER recorded by the controls would 

subsequently have been subtracted from each worker’s dosimeter reading. However, if 

control dosimeters were kept at a distant, central badging facility where ambient radiation 

levels were lower than in the work areas, each worker’s dosimeter would have recorded not 

only his or her occupational exposure, but also his or her exposure to elevated ambient 

radiation levels. In the latter case, no adjustment for occupational environmental radiation 

levels is needed, since they would have been included in the worker’s occupational 

measurements.

One important component of external environmental dose arose from submersion in, or 

irradiation at a distance from, a plume containing 41Ar (with a radiological half-life of 1.83 

hours), formed when naturally occurring 40Ar nuclei absorb neutrons near operating reactor 

facilities in the early days. The emissions from 41Ar are primarily a 1.2-MeV (maximum) 

β particle and a 1.3-MeV γ photon. A wooden badge exchange building would likely provide 

very little shielding or attenuation of the γ emission and, if air exchange rates at the control 

dosimeter storage point were high, even the β component could have approached outdoor 
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 7 of 26

levels. Besides radiation from airborne releases of radioactive materials, other components of 

EALER could arise from:

1. Scattered radiation from waste trenches, storage facilities, etc., 

2. Terrestrial contamination, and 

3. Skyshine (radiation scattered to the ground from air over nuclear or high-energy 

accelerator facilities). 

However, these components are unlikely to have been the same at dosimeter exchange 

facilities as on the rest of the site, so control dosimeters stored at remote exchange facilities 

would not have recorded this component.

Processes with potential for significant EALER include those with 

• Operating production reactors,

• Fuel reprocessing,

• Other radiochemical processing facilities,

• Atmospheric nuclear weapons testing,

• Underground nuclear weapons testing with significant venting of fission gasses,

• Accidental airborne releases of radioactive materials, and

• Certain high-energy accelerators (in the early years).

Large sites might have had inhomogeneous EALER, and a need for distributing control 

dosimeters with batches intended for particular areas might have had potential for significant 

EALER that the Energy Employee’s dosimeter might not have measured. 

In general, there will be a point in time, probably no later than 1970, after which there will be 

no need to assess a specific EALER to add to claimants’ dose histories, because (1) levels 

were so low they would not significantly impact probability of causation, and (2) control 

dosimeters were kept out of harm’s way and EALER would not have been subtracted. As 

environmental monitoring programs matured, environmental TLD measurements rule out 

significant EALER values. This can only be established for a particular site by reviewing site 

activities. 

External dosimetry results account for both occupational and environmental penetrating 

radiation exposures if control dosimeters were not exposed to elevated environmental 

radiation due to weapons production operations. All DOE and AWE sites might not have 

experienced the problem of missed EALER. 

It is concluded that for the years 1980 and later, except for the sites noted in Attachment A, 

environmental (onsite ambient) doses need not be considered when evaluating occupational 

doses because they would have been accounted for by personnel dosimeters. For extremely 

small environmental doses that were received but not reported due to dosimeter detection 

limits or reporting practices (i.e., in cases in which the reported dose is zero for a particular 

badge cycle), the assignment of missed doses according to procedures developed for this 

Project ensures that such environmental doses have been accounted for. 

All external ambient doses are assigned in the Interactive RadioEpidemiological Program

(IREP) as follows:
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 8 of 26

Exposure Rate: Chronic

Radiation Type: Photons E = 30–250 keV. 

NOTE: The energy range prescribed above differs from that recommended in OCAS-IG001. Other IREP parameters not listed above depend on the specific analysis being 

performed. 

The attachments to this procedure provide direction for assigning external ambient dose for 

employees from specific sites based on approved TBDs. 

NOTE: In this procedure, reference to a TBD pertains to the environmental dose TBD, 

typically Part 4, of the site profile. 

If the relevant site-specific TBD has not been issued, the Dose Reconstructor should review 

TBDs from other sites performing similar functions within the DOE complex, as well as other 

published health physics resources, to determine whether the case can be completed or 

needs to be placed on HOLD pending approval of the relevant site-specific TBD. 

Due to the variations in site geography, monitoring practices, reporting practices, and facilities 

and operations at the different sites, a best estimate cannot be generated for a site that does 

not have a completed TBD. To assess doses in recent years (e.g., 2003 to the present) that 

might not be covered in the TBDs, the most recent onsite ambient doses listed can be 

assumed to apply.

6.0 PROCEDURE

Dose Reconstructors

6.1 Review the Information Provided in the Case File

Determine the methodology (Maximize, Best Estimate, or Minimize) that will be applied 

to reconstruct the dose. The Dose Reconstructor must then consult the appropriate 

attachment to this procedure for specific instructions on reconstructing the onsite

ambient dose for that site. As described in OCAS-IG-001, onsite ambient doses apply 

both to unmonitored employees who were not likely to have been exposed to 

workplace radiation and to monitored employees whose monitoring results could have 

reflected a subtraction of elevated onsite ambient radiation doses. Attachment A

provides site-specific information regarding the need to assign onsite ambient doses 

for monitored employees.

6.2 Maximizing Methodology

Attachment B provides maximizing external ambient doses that can be assigned by a 

Dose Reconstructor to ensure claimant favorability. Background radiation not related 

to site operations has generally been included in the values listed, unless unequivocal 

background-subtracted values were provided in the TBD. Site-specific notes to the 

table are provided describing the sources of the values listed.
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 9 of 26

As a claimant-favorable assumption, the maximizing approach assumes that the 

employee worked 50 hours per week for 52 weeks per year, or 2,600 hours per year, 

and that he/she worked continuously in the area with the highest external onsite

ambient dose rate. Unless otherwise noted, the values should be assigned in IREP as 

a constant, and they include a multiplication factor of 1.3 (or other appropriate factor 

based on the TBD) to account for any potential under-response by the ambient 

radiation measurement devices. A claimant-favorable organ dose conversion factor 

(DCF) of 1 can be assumed. These factors combined with the maximum ambient 

values assumed when applying this methodology ensure that the ambient doses 

received by a worker have been overestimated.

For some sites, this approach significantly overestimates the external ambient dose for 

most employees. If necessary, the Dose Reconstructor can use more realistic, yet still 

claimant-favorable, assumptions to process clearly noncompensable cases.

Prior to assigning the doses listed in Attachment B for an unmonitored employee, the 

Dose Reconstructor must review the claim files provided by DOE to verify that the 

employee would not have been likely to have received doses exceeding the values 

listed and that there was not a potential for the employee to spend more than 50 hours/

week on the site over the course of his/her employment. In some cases, an employee

for whom monitoring data were not available could have received doses from radiation 

sources that exceed the onsite ambient levels, in which case the assignment of 

unmonitored dose is appropriate. 

6.3 Best Estimate Methodology

Attachment C provides information for the assignment of a best estimate of external 

onsite ambient dose. A best estimate must take into account all available records 

pertinent to determination of work location. For employees who worked in multiple 

areas of the site, if the employee records and claimant interview do not provide enough 

information to determine specific work locations, values representing a “site average” 

are appropriate as a best estimate. Otherwise, the annual dose should be calculated 

according to the fraction of time spent in different areas of the site.

Consistent with the precedent established in the SRS TBD, the assumption should be 

made that the energy employee worked 50 hours per week. In addition, 50 weeks of 

work per year should be assumed (to reasonably account for holiday and/or vacation 

time), for a total of 2,500 work-hours per year as a best estimate. Partial years of 

employment should be scaled accordingly. In addition, if the claimant interview or 

other available information indicates definitively that fewer or more hours were worked 

than the default assumption, this information should be used accordingly. For 

example, if it is indicated that the employee spent half of his/her time at offsite locations 

where only natural background radiation levels existed, only 25 hours of exposure per 

week should be assumed.

The calculated annual dose should be multiplied by the appropriate exposure (R)-toorgan DCF documented in OCAS-IG-001 for an isotropic exposure geometry.

If the supporting documentation for all of the elements necessary for a best estimate 

dose reconstruction does not exist, conservative assumptions should be applied 

related to work location and area conditions, erring in favor of the claimant. 
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 10 of 26

Attachment C provides information that describes how best estimate ambient doses 

are calculated from the site-specific TBDs, including information on the treatment of 

uncertainty. If appropriate, the attachment describes best estimate values that include 

subtraction of background radiation from the doses reported in the TBDs, although this 

calculation was often complicated by the site monitoring and reporting practices and 

the paucity of pertinent information in the TBDs. The numbers calculated in the 

manner described in Attachment C are available to the Dose Reconstructor either in 

the site-specific calculational workbooks or on the network. (Contact the Task 5 Tools 

Manager for assistance.)

6.4 Minimizing Methodology

The general philosophy for a minimizing approach is to assign dose from external 

ambient radiation only if the dose is necessary to generate a probability of causation 

(POC) greater than 50%. Doses should be assigned only for periods during which the 

employee was employed at the site and known to be present in conditions during which 

above-background onsite ambient doses might have been received. For many sites,

this excludes time spent indoors and in areas near the perimeter of the site. If the work 

location is unknown, doses from the area with the lowest external ambient dose should 

be applied. A best estimate approach (see Section 6.3) is warranted if records are not 

available to indicate the energy employee’s work location or if the employment area

was not monitored for ambient dose rates and the inclusion of external ambient dose is 

necessary to raise the calculated POC to 50% or greater. 

7.0 RECORDS

No records are generated as a result of this procedure.

8.0 APPLICABLE DOCUMENTS

8.1 Drivers

42 U.S.C. §§ 7384-7385, Energy Employees Occupational Illness Compensation 

Program Act (EEOICPA) of 2000, As Amended

Contract No. 200-2002-00593, Radiation Dose Estimation, Dose Reconstruction, and 

Evaluation of SEC Petitions Under EEOICPA

ORAUT-PLAN-0001, Quality Assurance Program Plan

8.2 Forms

None

9.0 DEFINITIONS AND ACRONYMS

ANL-W – Argonne National Laboratory-West.

AWE – Atomic Weapons Employer.
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 11 of 26

DCF – dose conversion factor.

DOE – U.S. Department of Energy.

EALER – Elevated Ambient Levels of External Radiation.

EEOICPA – Energy Employees Occupational Illness Compensation Program Act of 2000.

FEMP – Fernald Environmental Management Project.

FFTF – Fast Flux Test Facility.

GSD – geometric standard deviation.

ID – Identification.

INEL – Idaho National Engineering Laboratory (later changed to Idaho National Engineering 

and Environmental Laboratory (INEEL).

INEEL – Idaho National Engineering and Environmental Laboratory.

IREP – Interactive RadioEpidemiological Program.

KCP – Kansas City Plant.

keV – kilo-electron volt.

LANL – Los Alamos National Laboratory.

LLNL – Lawrence Livermore National Laboratory.

MeV – mega-electron volt.

mrem – millirem.

NIOSH – National Institute for Occupational Safety and Health.

NTS – Nevada Test Site.

OCAS – Office of Compensation Analysis and Support.

ORAU – Oak Ridge Associated Universities.

ORNL – Oak Ridge National Laboratory.

POC – probability of causation.

rem – roentgen equivalent man.

RFP – Rocky Flats Plant.

SRS – Savannah River Site.
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 12 of 26

TBD(s) – technical basis document(s).

TLD – thermoluminescent dosimeter.

β – beta radiation.

γ – gamma radiation.
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 13 of 26

ATTACHMENTS

The information contained in the following attachments is derived from the approved site Occupational 

Environmental Dose TBDs. All tables, figures, etc., referred to in these attachments pertain to the 

official revision number of the approved TBD for that site in place at the time the attachment was 

drafted. Although revisions to the TBDs will be reviewed by the Principal External Dosimetrist and 

any necessary modifications will be subsequently incorporated in a modification to this procedure, the 

Dose Reconstructor should be aware that this process could experience delays and, thus, should 

carefully review any revised TBDs with dates later than the effective date of this procedure.

These attachments include interpretation of sometimes unclear or inconsistent information contained 

in the TBDs. The Dose Reconstructor and Peer Reviewer have the authority to overrule these 

interpretations on a case-specific basis if all available information indicates that a different approach is 

warranted. However, the Dose Reconstructor and Peer Reviewer shall notify the Principal External 

Dosimetrist of any changes of interpretation or new information obtained that could affect other cases 

so that such information can be incorporated into subsequent revisions to this procedure.
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 14 of 26

ATTACHMENT A

EXTERNAL ONSITE AMBIENT DOSE ASSIGNMENT FOR MONITORED SITE EMPLOYEES

The following table lists rules for assigning external onsite ambient dose for monitored employees at 

the DOE sites addressed in Attachments B and C of this procedure. These rules have been derived 

from an evaluation of information provided in site profiles and communications with the site profile 

authors. Despite these rules, it is always acceptable with a noncompensable case to include onsite

ambient dose for all years of employment to ensure claimant favorability.

Site Assign external onsite ambient dose for monitored employees?

ANL-W Yes.

Fernald No (prior to 1985). Yes (1985–present, pending study of elevated ambient doses at badge 

storage locations).

Hanford Yes (prior to 1972). No (1972–later).

INEEL Yes.

KCP No. There is little likelihood of significant occupational environmental exposure. The TBD 

directs assignment of unmonitored dose for unmonitored workers.

K-25 No.

LANL No.

LLNL No.

Mound No.

NTS No.

PNNL Yes (prior to 1972). No (1972–later).

Paducah No. (Although information on the control dosimeter storage practices at the site is 

unavailable, background levels were present at most areas of the site that indicate it is likely 

that above-background radiation was not inappropriately excluded from the monitored 

doses.)

Pantex No.

Pinellas No.

Portsmouth No. (Although information on the control dosimeter storage practices at the site is 

unavailable, background levels were present at most areas of the site that indicate it is likely 

that above-background radiation was not inappropriately excluded from the monitored 

doses.) 

Rocky Flats Yes (prior to 1977, since control badges were stored on boards and could have been 

exposed to elevated ambient doses). No (1977–1999). Yes (2000–present).

SRS Yes through 1979. No (1980–present).

Weldon 

Spring

No.

X-10 No.

Y-12 No.
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date 06/28/2006 Page 15 of 26

ATTACHMENT B

MAXIMIZING DOSE SUMMARY

Page 1 of 5

Maximizing external ambient dose (rem)

Year

Site name

ANL-W Fernald Hanford INEEL K-25 LLNL LANL Mound NTS PNNL PADGDP Pantex Pinellas PORGDP RFP

Weldon

Spring ORNL (X-10) Y-12

1940

1941

1942

1943

1944 0.252 0.130 2.500 0.252 0.473 0.315

1945 0.252 0.130 15.000 0.252 0.473 0.315

1946 0.159 0.130 15.000 0.159 0.473 0.315

1947 0.157 0.130 15.000 0.157 0.473 0.315

1948 0.150 0.130 15.000 0.150 0.980 0.315

1949 0.205 0.130 0.723 0.205 1.555 0.315

1950 0.072 0.130 0.640 0.072 0.270 0.315

1951 0.032 0.072 0.130 0.640 0.072 0.030 0.372 0.315

1952 0.032 0.125 0.159 0.130 0.130 0.640 0.125 0.260 0.030 0.946 0.315

1953 0.032 0.082 0.159 0.130 0.130 0.640 0.082 0.260 0.030 0.073 0.710 0.315

1954 0.389 0.282 0.159 0.130 0.130 0.640 0.282 0.260 0.030 0.452 0.073 0.473 0.315

1955 0.389 0.345 0.159 0.130 0.130 0.356 0.345 0.260 0.030 0.452 0.073 0.406 0.315

1956 0.646 0.451 0.159 0.130 0.130 0.356 0.451 0.260 0.030 0.452 0.073 0.473 0.315

1957 0.646 0.350 0.159 0.130 0.130 0.356 0.350 0.260 0.030 0.452 0.073 0.646 0.372 0.315

1958 0.646 0.415 0.159 0.130 0.130 0.356 0.415 0.260 0.030 0.452 0.073 0.646 0.439 0.315

1959 0.646 0.225 0.159 0.130 0.130 0.356 0.225 0.260 0.030 0.452 0.073 0.646 0.642 0.315

1960 0.646 0.186 0.159 0.130 0.130 0.207 0.186 0.260 0.030 0.452 0.073 0.646 0.439 0.315

1961 0.646 0.186 0.159 0.130 0.130 0.207 0.186 0.260 0.030 0.452 0.073 0.646 0.338 0.315

1962 0.646 0.186 0.159 0.130 0.130 0.207 0.186 0.260 0.030 0.452 0.073 0.646 0.359 0.315

1963 0.646 0.153 0.159 0.130 0.130 0.207 0.123 0.153 0.260 0.030 0.001 0.452 0.073 0.646 0.351 0.315

1964 0.646 0.153 0.159 0.130 0.130 0.207 0.123 0.153 0.260 0.030 0.001 0.452 0.073 0.646 0.274 0.315

1965 0.021 0.646 0.153 0.159 0.130 0.130 0.126 0.127 0.123 0.153 0.260 0.030 0.001 0.452 0.073 0.646 0.243 0.315

1966 0.021 0.646 0.140 0.159 0.130 0.130 0.105 0.127 0.123 0.140 0.260 0.030 0.001 0.452 0.073 0.646 0.254 0.315

1967 0.021 0.646 0.163 0.159 0.130 0.130 0.090 0.127 0.123 0.163 0.260 0.030 0.001 0.452 0.073 0.646 0.241 0.315

1968 0.021 0.646 0.204 0.159 0.130 0.130 0.090 0.127 0.110 0.204 0.260 0.030 0.001 0.452 0.073 0.257 0.315

1969 0.021 0.646 0.163 0.159 0.130 0.130 0.090 0.127 0.123 0.163 0.260 0.030 0.001 0.452 0.073 0.283 0.315

1970 0.021 0.646 0.096 0.159 0.130 0.130 0.039 0.085 0.123 0.096 0.260 0.030 0.001 0.452 0.073 0.243 0.315

1971 0.021 0.291 0.040 0.159 0.130 0.117 0.082 0.085 0.123 0.040 0.260 0.030 0.001 0.452 0.073 0.237 0.315

1972 0.021 0.291 0.044 0.159 0.130 0.130 0.067 0.085 0.123 0.044 0.260 0.030 0.001 0.452 0.073 0.237 0.315

1973 0.013 0.291 0.048 0.144 0.130 0.130 0.102 0.085 0.123 0.048 0.260 0.030 0.001 0.452 0.073 0.237 0.315

1974 0.132 0.291 0.043 0.223 0.130 0.130 0.102 0.085 0.123 0.043 0.260 0.030 0.001 0.452 0.073 0.237 0.315

1975 0.094 0.291 0.040 0.127 0.130 0.130 0.113 0.061 0.123 0.040 0.260 0.015 0.001 0.452 0.073 0.077 0.237 0.315

1976 0.055 0.291 0.035 0.111 0.130 0.121 0.077 0.061 0.123 0.035 0.260 0.015 0.001 0.452 0.073 0.077 0.190 0.315

1977 0.067 0.227 0.035 0.113 0.130 0.130 0.081 0.061 0.123 0.035 0.260 0.015 0.001 0.452 0.073 0.077 0.142 0.315

1978 0.038 0.287 0.029 0.089 0.130 0.130 0.069 0.061 0.123 0.029 0.260 0.015 0.001 0.452 0.073 0.077 0.125 0.315

1979 0.023 0.000 0.029 0.084 0.130 0.125 0.075 0.061 0.074 0.029 0.260 0.015 0.001 0.452 0.073 0.077 0.112 0.315

1980 0.020 0.323 0.029 0.089 0.130 0.130 0.090 0.048 0.080 0.029 0.260 0.015 0.001 0.452 0.073 0.077 0.108 0.315
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date 06/28/2006 Page 16 of 26

ATTACHMENT B

MAXIMIZING DOSE SUMMARY

Page 2 of 5

Maximizing external ambient dose (rem) (continued)

Year

Site name

ANL-W Fernald Hanford INEEL K-25 LLNL LANL Mound NTS PNNL PADGDP Pantex Pinellas PORGDP RFP

Weldon

Spring ORNL (X-10) Y-12

1981 0.015 0.500 0.038 0.091 0.130 0.130 0.052 0.048 0.084 0.038 0.260 0.015 0.001 0.452 0.073 0.077 0.098 0.315

1982 0.015 0.510 0.058 0.157 0.130 0.130 0.048 0.048 0.081 0.058 0.260 0.015 0.001 0.452 0.073 0.077 0.101 0.315

1983 0.018 0.521 0.062 0.127 0.130 0.130 0.056 0.048 0.079 0.062 0.260 0.015 0.001 0.452 0.073 0.077 0.098 0.315

1984 0.017 0.385 0.073 0.027 0.130 0.130 0.054 0.048 0.126 0.073 0.260 0.015 0.001 0.452 0.073 0.091 0.105 0.315

1985 0.017 0.406 0.073 0.025 0.130 0.104 0.056 0.041 0.134 0.073 0.260 0.015 0.001 0.452 0.073 0.086 0.101 0.315

1986 0.017 0.385 0.073 0.027 0.130 0.090 0.054 0.041 0.123 0.073 0.260 0.015 0.001 0.404 0.073 0.071 0.101 0.315

1987 0.017 0.100 0.073 0.027 0.130 0.092 0.049 0.041 0.095 0.073 0.260 0.015 0.001 0.452 0.073 0.056 0.101 0.315

1988 0.017 0.175 0.073 0.027 0.130 0.090 0.056 0.041 0.086 0.073 0.260 0.015 0.001 0.440 0.073 0.049 0.101 0.315

1989 0.017 0.202 0.073 0.030 0.130 0.130 0.044 0.041 0.084 0.073 0.260 0.015 0.001 0.435 0.073 0.054 0.101 0.315

1990 0.010 0.116 0.028 0.027 0.130 0.130 0.053 0.037 0.074 0.028 0.260 0.015 0.001 0.424 0.073 0.051 0.101 0.315

1991 0.010 0.128 0.028 0.035 0.130 0.101 0.053 0.037 0.075 0.028 0.260 0.015 0.001 0.441 0.073 0.058 0.101 0.315

1992 0.010 0.136 0.028 0.031 0.130 0.099 0.070 0.037 0.073 0.028 0.260 0.015 0.001 0.417 0.073 0.053 0.101 0.315

1993 0.010 0.149 0.027 0.030 0.130 0.096 0.044 0.037 0.082 0.027 0.260 0.015 0.001 0.254 0.073 0.965 0.101 0.315

1994 0.009 0.149 0.025 0.036 0.130 0.103 0.047 0.037 0.055 0.025 0.260 0.015 0.001 0.061 0.073 0.965 0.101 0.315

1995 0.015 0.137 0.032 0.026 0.130 0.087 0.112 0.037 0.082 0.032 0.260 0.015 0.001 0.152 0.073 0.965 0.101 0.315

1996 0.014 0.050 0.019 0.026 0.078 0.072 0.037 0.087 0.019 0.260 0.015 0.189 0.073 0.064 0.101 0.315

1997 0.006 0.051 0.016 0.026 0.083 0.137 0.037 0.066 0.016 0.260 0.015 0.222 0.073 0.071 0.101 0.315

1998 0.007 0.045 0.027 0.022 0.086 0.126 0.037 0.078 0.027 0.260 0.015 0.228 0.073 0.054 0.101 0.315

1999 0.008 0.045 0.029 0.017 0.082 0.072 0.037 0.074 0.029 0.260 0.015 0.222 0.073 0.048 0.101 0.315

2000 0.022 0.049 0.029 0.022 0.085 0.080 0.037 0.084 0.029 0.260 0.015 0.252 0.073 0.044 0.101 0.315

2001 0.009 0.049 0.029 0.011 0.130 0.169 0.037 0.115 0.029 0.260 0.254 0.073 0.044 0.101 0.315

2002 0.014 0.048 0.029 0.019 0.070 0.037 0.029 0.241 0.073 0.044 0.101 0.315

2003 0.029 0.037 0.029 0.241 0.073 0.044 0.101

Notes Supporting the Calculation and Use of Maximum External Ambient Doses

General Notes

Unless otherwise indicated in the site-specific notes below, maximum values provided in the above table were derived from the 

reported TBD values without background subtraction by adjusting for a 2,600-hour work year and multiplying by 1.3 to account for 

uncertainty. These values should be assigned in IREP as a constant. All tables or other data sources cited in the notes below refer 

to the Occupational Environmental Dose TBD (typically Part 4) of the site profile.

Site-Specific Notes

ANL-W: The maximum annual dose is based on the maximum values listed for each year from Tables 4-6 and 6-1 of the TBDs, 

multiplied by 1.2 to account for a 20% uncertainty in the TLD readings suggested in the TBD. The 20% uncertainty also applies to 
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date 06/28/2006 Page 17 of 26

ATTACHMENT B

MAXIMIZING DOSE SUMMARY

Page 3 of 5

the early (film-badge) years because the reported values are based on back-extrapolation from TLD readings. These values reflect 

background-subtracted doses.

Fernald: Based on information provided in the TBD, some areas of the site had the potential to deliver an annual dose greater than 

3 rem/year during certain periods of site operation. However, the TBD also provides an FEMP site average as a more realistic value

that excludes the K-65 silos since that area has the highest dose rate and was occupied infrequently. For the purpose of assigning a 

maximized external ambient dose to a typical unmonitored employee, the FEMP site average dose rates provided in Table 4-17 of 

the TBD were used.

Hanford: The maximum annual dose is based on the maximum value for each year listed in Table 4.3.1-1 of the TBD, adjusted for a 

2,600-hour year. The value for 1944 was assumed to be equal to the value for 1945; this is likely to be a claimant-favorable 

assumption because the operations at the site were limited in 1944 compared to 1945. For 1943, only very limited operations 

occurred, so no onsite ambient doses should be assigned. (The few employees involved in radiological operations that year should 

instead be assigned unmonitored doses.)

INEEL: The maximum annual dose is based on the maximum values listed for each year from Table 4-13 of the TBD, multiplied by 

1.2 to account for a 20% uncertainty in the TLD readings suggested in the TBD. The 20% uncertainty also applies to the early (filmbadge) years at the site because the reported values are based on back-extrapolation from TLD readings. These values reflect 

background-subtracted doses.

KCP: According to Section 4.0 of the site profile, KCP routinely handles hazardous chemicals, but there is limited handling of 

radioactive materials and thus essentially little likelihood of a significant occupational environmental exposure associated with 

releases. The site profile provides guidance for assignment of unmonitored dose in the case of unmonitored workers. No onsite

ambient dose is provided.

K-25: A maximum annual dose of 0.130 rem is the result of adding the highest dose rate provided in Table 4D-4 (10.5 μR/hr for 

1976) after application of the provided geometric standard deviation (GSD) of 1.07 to determine the 95th-percentile dose and adding 

the dose rate from the parking area near the cylinder yards. The dose rates were then multiplied by 2,600 hours per year. A 

multiplication factor of 1.3 has NOT been applied. 

LLNL: The maximum annual dose is based on the maximum values listed in Table 4-9 of the TBD, adjusted for 2,600 hours per 

year. Based on this being a maximum, a multiplication factor of 1.3 has NOT been applied.
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date 06/28/2006 Page 18 of 26

ATTACHMENT B

MAXIMIZING DOSE SUMMARY

Page 4 of 5

LANL: The maximum annual dose for 1965 through 2002 is based on the maximum values listed in Tables 4-25 and 4-30 of the 

TBD and has been adjusted to 2,600 hours to calculate the maximum doses in this procedure. For 1943 through 1964, the highest 

value for any year (2001) was used to estimate the onsite ambient dose since no value is provided in the TBD.

Mound: The maximum onsite ambient doses are based on the maximum values listed for each year in Tables 4-9 and 4-29 of the 

TBD. For 1945 through 1948, the maximum is the permissible level of 15 rem per year. For 1944, based on 210Po production being 

performed for 8 weeks, the maximum of 15 rem per year was multiplied by a factor of 0.16 based on the mean doses provided in the 

TBD. For 1949 through 2003, the maximum provided in Table 4-29 was adjusted by a factor of 1.3 to account for an assumed 2,600 

hours on the site. 

NTS: The maximum onsite ambient doses are based on the maximum values listed for each year in Table 4.3.1-2 of the TBD. The 

TBD states that, prior to 1967, the dose rates for 1967 can be applied for the years 1963–1966 as a maximizing assumption. Years 

prior to 1963 have been omitted due to substantial releases from above-ground testing.

PNNL: See Hanford above.

Paducah: The TBD states that 200 mrem should be assigned for a 2,000-hour year. Adjusting for a 2,600-hour work year, the 

maximum onsite ambient dose is 260 mrem (0.260 rem) per year. Since this value is claimant-favorable according to the TBD, a 

multiplication factor of 1.3 has NOT been applied.

Pantex: Section 4.3.1 of the TBD recommends that ambient external dose should be applied as 0.100 rem for the years from 1951 

to 1974, and 0.050 rem for the years from 1975 to 2000. These values represent a full year, so they have been adjusted to reflect a 

2,600-hour work year. Since it is stated in the TBD that these values are claimant-favorable, they have NOT been multiplied by 1.3.

Pinellas: The primary environmental release was tritium, which does not contribute to external dose. The external dose was 

determined based on 14 C and 85Kr emissions. Note that from 1957 through 1962, there were no external doses due to stack 

emissions because neither 14 C nor 85Kr was emitted during these years. The doses provided in Table 4.3.1-1 are assumed to be for 

2,600 working hours per year. A maximizing onsite ambient dose of 0.001 rem per year is a very claimant-favorable assumption.

Portsmouth: The doses included in the above table significantly overestimate the average unmonitored employee’s external onsite

ambient dose. The values were derived from the TBD Table 4.3.1-1 values at the “Power Pole 874” location at the northwest corner 

of the cylinder storage areas, where it is unlikely an unmonitored employee would have been present and where the dose rates are 

significantly higher than both the dose rates found on the rest of the site and the median dose to a monitored employee. Note that in 

2000 and 2001, dose rates at the X-744G Building were higher than the “Power Pole 874” doses. For the period between 1954 and 

1985, the maximum ambient dose has been assumed to equal the value for 1987 at “Power Pole 874,” as this is the highest value
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date 06/28/2006 Page 19 of 26

ATTACHMENT B

MAXIMIZING DOSE SUMMARY

Page 5 of 5

listed for that location. If it can be determined that the employee did not work in this location, the TBD stipulates that the maximum 

value of 35.9 mrem from Table 4.3.1-1 can be used as the basis for a maximizing assessment; this value converts to an annual dose 

of 0.061 rem under the assumptions stated in the “General Notes” above.

RFP: To ensure claimant favorability, the maximum mean yearly dose from Table 4-3 of the TBD, combined with the maximum 

standard deviation recommended in the TBD, was applied to all years. This results in a recommended maximum value of 73 mrem, 

calculated as follows: 

(2600 / 8760)(Mean Max + 2σ Max ) = .297 (167 + (2 * 39)) = 73 mrem.

This value clearly provides a claimant-favorable assessment of onsite ambient dose for administrative work or work in outside 

locations because, as described in both the TBD and Attachment C of this procedure, the external onsite ambient doses at the site 

exceed natural background by only 9%.

SRS: The maximum values for application are provided in Table 3.4-1 of the SRS TBD.

Weldon Spring: The plant was shut down at the end of 1966. Shutdown procedures began in 1967 and only a few pounds of pure 

compounds were present in any single piece of equipment. The bulk of the remaining radiological materials that remained on the site 

were in building sumps and secondary pieces of process equipment without routine access ports. Monitoring and maintenance was 

performed from 1975 to 1985 with site remediation beginning in 1986. 

X-10: See ‘Best Estimate’ section for X-10.

Y-12: The maximum annual dose is based on the 95th-percentile dose rate (excluding background) from Table D-7 of the TBD. 

Because the 95th-percentile value was used, a multiplication factor of 1.3 has NOT been applied.
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 20 of 26

ATTACHMENT C

METHODS FOR ASSIGNING SITE-SPECIFIC BEST ESTIMATES 

OF EXTERNAL ONSITE AMBIENT DOSES

Page 1 of 7

Best estimates incorporate a 2,500-hour work year (which the Dose Reconstructor has the discretion 

to modify, as discussed in Section 6.3). The reported values are not multiplied by a factor to ensure 

claimant favorability, but are typically treated as normal or lognormal distributions depending on the 

TBD information regarding uncertainty. If uncertainty is not discussed in the TBD, a default 

assumption of a normal distribution and 30% standard deviation is applied. Background is excluded 

from the reported values unless the TBD does not provide reliable information that supports 

background subtraction.

ANL-W: For the best estimate approach, the area-specific values provided in Table 4-6 of the 

environmental TBD are applied. Additional fenceline direct gamma values for the EBR-1 and 

Radioactive Waste Management Complex are provided in Table 6-1 of the external dose TBD. These 

values should be applied in IREP as a normal distribution with a standard deviation of 20%. If the 

employee’s work location was unknown or included many areas of the site with no apparent location 

frequented more than others, the following values should be used:

NOTE: The Parameter 1 and Parameter 2 values should be multiplied by an appropriate factor to 

account for the fact that the TBD values are relevant to a full year, e.g., 0.285 for 2,500 hours per 

year. 

ANL-W Best Estimate Doses (rem)

Year(s) Distribution type IREP Param. 1 IREP Param. 2

1952-72 Normal 0.047 0.006

1973 Normal 0.029 0.004

1974 Normal 0.140 0.025

1975 Normal 0.102 0.018

1976 Normal 0.087 0.012

1977 Normal 0.070 0.013

1978 Normal 0.055 0.008

1979 Normal 0.043 0.006

1980 Normal 0.040 0.005

1981 Normal 0.026 0.003

1982 Normal 0.025 0.003

1983 Normal 0.028 0.004

1984 Normal 0.031 0.004

1985 Normal 0.031 0.004

1986 Normal 0.031 0.004

1987 Normal 0.031 0.004

1988 Normal 0.031 0.004

1989 Normal 0.031 0.002

1990 Normal 0.020 0.002

1991 Normal 0.020 0.002

1992 Normal 0.020 0.003

1993 Normal 0.023 0.002

1994 Normal 0.014 0.003

1995 Normal 0.022 0.003

1996 Normal 0.028 0.002

1997 Normal 0.016 0.002

1998 Normal 0.010 0.002

1999 Normal 0.016 2.039

2000 Normal 0.037 0.005

2001 Normal 0.009 0.002

2002 Normal 0.030 0.004
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 21 of 26

ATTACHMENT C

METHODS FOR ASSIGNING SITE-SPECIFIC BEST ESTIMATES 

OF EXTERNAL ONSITE AMBIENT DOSES

Page 2 of 7

Fernald: For the best estimate approach, the area-specific “Net above background” values from 

Table 4-17 are applied. If the employee’s work location was unknown or included many areas of the 

site, the FEMP site average values should be used. These values should be applied in IREP as a 

normal distribution with a standard deviation of 30%.

Hanford: The areas listed in Table 4.3.1-1 have been grouped in the table below to simplify the 

assignment of external onsite ambient dose. The doses represent an average value for the area and 

have been modified for a 2,500-hour work year. These values reflect a subtraction of 20 mrem, which

represents a claimant-favorable interpretation of background radiation from the TBD data. Any

negative value resulting from this subtraction has been changed to zero. The values should be 

treated in IREP as a normal distribution with a standard deviation of 30%.

If the specific work locations within the area are known, the Dose Reconstructor should use the 

appropriate values from Table 4.3.1-1 of the TBD (adjusted to a 2,500-hour work year). As an 

inherently claimant-favorable assumption, values for 1944 can be assumed to be equal to the 1945 

values. For 1943, unmonitored doses (as opposed to onsite ambient doses) should be assigned if 

applicable. In the 100 and 300 Areas from 1957 to 1959 if values were not reported, the claimantfavorable assumption was made to use the previously listed value for that area. For 1960 to 1965, the 

values for “Perimeter Locations/FFTF” represent the site-wide average excluding the 100, 200, and 

300 Areas. In the 100, 200, and 300 Areas from 1960 to 1962, ambient dose rates were based on the 

average gamma levels for all three locations from 1952 to 1956. Similarly, the values listed for 1963 

to 1965 for the 100, 200, and 300 Areas were based on the average values for 1966 to 1970. In 

1969, the value from 1968 was used for the perimeter areas.

Hanford Best Estimate Doses (rem)

Year

300 

Area

100 

Area

200 

Area

Perimeter 

locations/FFTF

1945 0.193 0.140 0.217 0.166

1946 0.066 0.029 0.088 0.031

1947 0.131 0.058 0.088 0.090

1948 0.075 0.043 0.041 0.124

1949 0.055 0.015 0.003 0.178

1950 0.041 0.035 0.031 0.020

1951 0.041 0.035 0.031 0.020

1952 0.100 0.017 0.011 0.000

1953 0.024 0.028 0.050 0.009

1954 0.010 0.108 0.160 0.019

1955 0.085 0.107 0.257 0.075

1956 0.180 0.248 0.275 0.138

1957 0.316 0.248 0.163 0.138

1958 0.316 0.248 0.379 0.138

1959 0.316 0.248 0.196 0.138

1960 0.080 0.100 0.131 0.018

1961 0.080 0.100 0.131 0.018

1962 0.080 0.100 0.131 0.029

1963 0.038 0.055 0.038 0.027

1964 0.038 0.055 0.038 0.022
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 22 of 26

Hanford Best Estimate Doses (rem)

Year

300 

Area

100 

Area

200 

Area

Perimeter 

locations/FFTF

1965 0.038 0.055 0.038 0.014

1966 0.029 0.048 0.043 0.019

1967 0.030 0.069 0.049 0.041

1968 0.029 0.075 0.032 0.024

1969 0.080 0.079 0.080 0.024

1970 0.019 0.029 0.024 0.004

1971 0.001 0.005 0.009 0.001

1972 0.006 0.009 0.012 0.003

1973 0.003 0.007 0.016 0.001

1974 0.001 0.003 0.014 0.001

1975 0.001 0.003 0.013 0.001

1976 0.000 0.001 0.008 0.000

1977 0.000 0.000 0.009 0.000

1978 0.000 0.002 0.006 0.000

1979 0.000 0.002 0.007 0.001

1980 0.004 0.001 0.005 0.000

1981 0.016 0.002 0.004 0.001

1982 0.131 0.002 0.004 0.001

1983 0.103 0.002 0.002 0.001

1984 0.006 0.003 0.000 0.001

1985 0.004 0.000 0.000 0.000

1986 0.006 0.000 0.000 0.000

1987 0.006 0.003 0.004 0.003

1988 0.004 0.004 0.004 0.004

1989 0.005 0.004 0.005 0.005

1990 0.004 0.004 0.003 0.004

1991 0.008 0.009 0.006 0.006

1992 0.008 0.007 0.008 0.007

1993 0.006 0.007 0.008 0.006

1994 0.010 0.011 0.011 0.009

1995 0.004 0.003 0.004 0.003

1996 0.003 0.003 0.004 0.003

1997 0.003 0.003 0.004 0.003

1998 0.004 0.003 0.005 0.004

1999 0.004 0.003 0.006 0.005

2000 0.004 0.003 0.005 0.004

2001 0.004 0.004 0.005 0.005

INEEL: For the best estimate approach, the area-specific values from Table 4-13 are applied. These 

values should be applied in IREP as a normal distribution with a standard deviation of 20%. If the 

employee’s work location was unknown or included many areas of the site with no apparent location 

frequented more than others, the following values should be used (NOTE: the Parameter 1 values 

should be multiplied by an appropriate factor to account for the fact that the TBD values are relevant 

to a full year, e.g., 0.285 for 2,500 hours per year; the Parameter 2 values should not be changed):

ATTACHMENT C

METHODS FOR ASSIGNING SITE-SPECIFIC BEST ESTIMATES 

OF EXTERNAL ONSITE AMBIENT DOSES

Page 3 of 7
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 23 of 26

ATTACHMENT C

METHODS FOR ASSIGNING SITE-SPECIFIC BEST ESTIMATES 

OF EXTERNAL ONSITE AMBIENT DOSES

Page 4 of 7

INEEL Best Estimate Doses (rem)

Year(s) Distribution type IREP Param. 1 IREP Param. 2

1952-72 Lognormal 0.048 3.947

1973 Lognormal 0.047 3.058

1974 Lognormal 0.064 4.767

1975 Lognormal 0.039 4.111

1976 Lognormal 0.047 2.798

1977 Lognormal 0.020 7.173

1978 Lognormal 0.019 5.452

1979 Lognormal 0.029 3.481

1980 Lognormal 0.034 3.090

1981 Lognormal 0.029 3.301

1982 Lognormal 0.023 3.019

1983 Lognormal 0.034 2.471

1984-92 Lognormal 0.032 2.846

1993 Lognormal 0.025 1.671

1994 Lognormal 0.019 2.695

1995 Lognormal 0.013 3.114

1996 Lognormal 0.021 2.183

1997 Lognormal 0.015 2.255

1998 Lognormal 0.016 2.184

1999 Lognormal 0.016 2.039

2000 Lognormal 0.022 1.980

2001 Lognormal 0.013 3.045

2002 Lognormal 0.025 1.888

Each of the 11 area-specific data points in Table 4-13 of the TBD were used to generate the annual 

distributions to represent the site-wide ambient doses shown above. The values were calculated

using the Crystal Ball code (Decisioneering Inc., Denver, CO) based on the assumption that the data 

fit a lognormal distribution. An analysis of the data indicated that they fit a lognormal distribution 

better than a normal distribution for most years; thus, a lognormal distribution was assumed for all 

years to ensure consistency and claimant favorability.

KCP: According to Section 4.0 of the TBD, KCP routinely handles hazardous chemicals, but there is 

limited handling of radioactive materials and thus essentially little likelihood of a significant 

occupational environmental exposure associated with releases. The TBD provides guidance for 

assignment of unmonitored dose in the case of unmonitored workers. No onsite ambient dose is 

provided.

K-25: The best estimates should be based on the average levels provided in Table 4D-4 of the TBD. 

The dose rates should be multiplied by an assumed 2,500 working hours per year and entered into 

Parameter 1. The GSD should be entered as Parameter 2 and a lognormal distribution applied. If 

there is indication that the Energy Employee spent time in proximity to the cylinder yards, the dose 

rate given in the TBD should be scaled based on the assumed hours in that location.

LLNL: The best estimate values should be based on the site average values provided in Table 4-9 of 

the TBD. The values provided in the TBD are based on 2,000 hours per year and should be adjusted 
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 24 of 26

ATTACHMENT C

METHODS FOR ASSIGNING SITE-SPECIFIC BEST ESTIMATES 

OF EXTERNAL ONSITE AMBIENT DOSES

Page 5 of 7

for an assumed 2,500 working hours per year and entered into Parameter 1. Parameter 2 is 

determined by multiplying the dose for Parameter 1 by 0.20 (20% uncertainty). The calculated dose 

and uncertainty should be entered into IREP as a normal distribution.

LANL: The best estimates should be applied as a lognormal distribution based on the Geometric 

Mean, adjusted for 2,500 hours, provided in Table 4-25 of the LANL TBD as Parameter 1 and the 

provided GSD provided in Table 4-25 as Parameter 2.

Mound: The best estimates should be based on the mean site-wide values from Tables 4-9 and 4-29 

in the TBD. The values provided in the TBD are based on 2,000 working hours per year and should 

be adjusted for an assumed 2,500 working hours per year. A GSD of 3.6 should be applied for 1944 

through 1948 and a GSD of 3.12 applied starting in 1949. The calculated dose and GSD should be 

entered into IREP as a lognormal distribution.

NTS: The best estimates are based on the values from Table 4.3.1-2 minus the background radiation 

from Table 4.3.1-1. (If the resultant value is negative, the onsite ambient dose is considered zero.) 

(NOTE: The values provided in the tables are based on 8,760 hours per year). If the employee’s 

work location was unknown or included many areas of the site, the average of the area-specific 

values should be used. The background for years listed in the TBD as “Not Reported” is assumed to 

be 95 mrem. For periods where there are no data, the site maximum should be applied as suggested 

by the TBD. Based on information in Section 4.3.1 of the TBD, the values should be applied in IREP 

as a lognormal distribution with a GSD of 1.52.

PNNL: See Hanford.

Paducah: Similar to Portsmouth, the monitoring locations around the cylinder storage yards show an 

ambient background rate that is clearly elevated over the rest of the site. At other areas of the site, it 

appears that the ambient dose rates might not have been elevated over the background rates. In 

addition, the ambient dose rates in the cylinder yards are proportional to the amount of material stored 

there, which grew over time. Therefore, as stated in the TBD, in the early periods of operation when it 

was more likely an unmonitored employee might have been present in the cylinder yards, the dose 

rates were lower, while in the modern era it is unlikely an unmonitored employee would spend a

significant amount of time in the cylinder yards. Thus, consistent with the approach for the 

Portsmouth site, for employees not near the cylinder storage yards, the best estimate of the 

background-subtracted external onsite ambient dose rate is 0 mrem. For employees near the cylinder 

storage yards, the average values presented in the TBD, when adjusted for a 2,500-hour work year, 

lead to a geometric mean of 0.131 rem. These values should be applied in IREP as a lognormal 

distribution with a GSD of 1.43. Because these values are based on limited data, mostly from the 

modern era (when the cylinder yard inventories were the highest), they are, by necessity due to the

paucity of data, claimant-favorable for employees in the early years at the site.

Pantex: The linear regression method discussed in the TBD was used to generate an annual dose. 

The values were then adjusted from a full year (8,760 hours) to a 2,500-hour year. The calculated 

annual values are consistent with the 5-year values presented in Table 4-6 of the TBD. The yearly 

standard deviation was calculated assuming that the 95th percentile is twice the value at the mean. 
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ATTACHMENT C

METHODS FOR ASSIGNING SITE-SPECIFIC BEST ESTIMATES 

OF EXTERNAL ONSITE AMBIENT DOSES

Page 6 of 7

The values in the table below should be applied in IREP as a normal distribution together with values 

listed for Parameter 2 based on the calculated standard deviation. 

Pantex Best Estimate External Ambient Doses (rem)

Year Dose (Parameter 1) σ (Parameter 2) Year Dose (Parameter 1) σ (Parameter 2)

1950 0.0311 0.0189 1976 0.0147 0.0090

1951 0.0305 0.0185 1977 0.0141 0.0086

1952 0.0298 0.0181 1978 0.0135 0.0082

1953 0.0292 0.0178 1979 0.0128 0.0078

1954 0.0286 0.0174 1980 0.0122 0.0074

1955 0.0280 0.0170 1981 0.0116 0.0070

1956 0.0273 0.0166 1982 0.0109 0.0067

1957 0.0267 0.0162 1983 0.0103 0.0063

1958 0.0261 0.0158 1984 0.0097 0.0059

1959 0.0254 0.0155 1985 0.0091 0.0055

1960 0.0248 0.0151 1986 0.0084 0.0051

1961 0.0242 0.0147 1987 0.0078 0.0047

1962 0.0235 0.0143 1988 0.0072 0.0044

1963 0.0229 0.0139 1989 0.0065 0.0040

1964 0.0223 0.0136 1990 0.0059 0.0036

1965 0.0217 0.0132 1991 0.0053 0.0032

1966 0.0210 0.0128 1992 0.0047 0.0028

1967 0.0204 0.0124 1993 0.0040 0.0024

1968 0.0198 0.0120 1994 0.0034 0.0021

1969 0.0191 0.0116 1995 0.0028 0.0017

1970 0.0185 0.0113 1996 0.0021 0.0013

1971 0.0179 0.0109 1997 0.0015 0.0009

1972 0.0172 0.0105 1998 0.0010 0.0005

1973 0.0166 0.0101 1999 0.0010 0.0001

1974 0.0160 0.0097 2000 0.0010 0.0001

1975 0.0154 0.0093

Pinellas: The information provided in the maximizing section is adequate for all dose reconstructions 

when external onsite ambient dose needs to be applied.

Portsmouth: The TBD states that for employees not near the UF6 cylinder storage yards (i.e., the 

guard gates, switchyards, warehouses, process buildings, and wastewater facility), the backgroundsubtracted external onsite ambient dose rate is 0 mrem. For employees near either the UF6 cylinder 

storage yards or the X-744G Bulk Storage Building, the values from the appropriate columns in 

Table 4.3.1-1 or 4.3-3, respectively, should be used after adjusting for a 2,500-hour work year. The 

values should be applied in IREP as a normal distribution with a standard deviation of 30%.

RFP: The TBD states that the ambient radiation at the site is elevated approximately 9% above the 

natural background radiation. Thus, an annual external ambient dose of 4 mrem can be considered a 

best estimate for work in outside areas or for administrative workers not potentially exposed to 

workplace radiation sources. This value should be applied in IREP as a constant. The TBD 

information does not support a best estimate of onsite ambient dose that could have been 
Document No. ORAUT-PROC-0060 Revision No. 01 Effective Date: 06/28/2006 Page 26 of 26

ATTACHMENT C

METHODS FOR ASSIGNING SITE-SPECIFIC BEST ESTIMATES 

OF EXTERNAL ONSITE AMBIENT DOSES

Page 7 of 7

inappropriately subtracted from a worker’s dosimeter readings due to the storage of control badges in 

areas with elevated ambient dose rates.

SRS: The best estimate for external onsite ambient dose can be calculated using the tool that 

incorporates the Crystal Ball program to perform best estimate dose reconstructions. 

Weldon Spring: The best estimate for claims should be assigned the values provided below for the 

appropriate area as a normal distribution with a standard deviation of 30% applied as Parameter 2 in 

the IREP input sheet

Weldon Spring Best Estimate Doses (mrem)

Year WSRP WSCP WSQ

1957-1967 478

1975-1979 57 28

1980 57 28

1981 57 28

1982 57 24

1983 57 27

1984 67 36

1985 64 57 35

1986 53 44 27

1987 40 41 27

1988 36 34 21

1989 40 37 23

1990 38 38 22

1991 43 40 24

1992 39 39 21

1993 36 34 713

1994 34 34 713

1995 40 41 713

1996 39 47 18

1997 39 53 17

1998 36 40 16

1999 35 35 16

2000 17 32 14

2001 17 32 14

2002 17 32 14

2003 17 32 14

2004 17 32 14

X-10: The TBD does not contain sufficient information regarding natural background radiation or 

fallout from atmospheric weapons testing to allow their subtraction from the rates reported in

Attachment 4C of the TBD. Also, the TBD does not provide sufficient information to permit areaspecific assessments of ambient dose. Thus, the Attachment 4C values (combined with a 2,500-hour 

work week and assigned as lognormal with a GSD of 3.0) can be considered best estimates. 

Y-12: For a best estimate approach, the geometric mean (13 μrem/hr) of the background subtracted 

dose reported in Table D-7 of the TBD translates to a dose of 0.0325 rem. This value should be 

applied in IREP as a lognormal distribution, with a GSD of 4.0 based on the TBD information (revised 

upward to account for the uncertainty associated with background subtraction).