ORAU TEAM

Dose Reconstruction

Project for NIOSH

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

Page 1 of 10

Document Title:

External Coworker Dosimetry Data for the 

Portsmouth Gaseous Diffusion Plant 

Document Number: ORAUT-OTIB-0040

Revision: 00

Effective Date: 07/29/2005

Type of Document: OTIB

Supersedes: None

Subject Expert: Steven E. Merwin

Document Owner

Approval: Signature on File Approval Date: 07/11/2005

Judson L. Kenoyer, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 07/26/2005

Richard E. Toohey, Project Director

Approval: Signature on File Approval Date: 07/29/2005

James W. Neton, Associate Director for Science

 New Total Rewrite Revision Page Change

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

PLEASE DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-OTIB-0040 Revision No. 00 Effective Date: 07/29/2005 Page 2 of 10

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION

NUMBER DESCRIPTION

05/02/2005 00-A New technical information bulletin to provide information to allow 

ORAU Team dose reconstructors to assign doses at the Portsmouth 

Gaseous Diffusion Plant to certain workers who have no or limited 

monitoring data, based on site coworker data. Initiated by Steven E. 

Merwin.

05/11/2005 00-B Incorporates internal reviewer comments. Initiated by Steven E. 

Merwin.

06/30/2005 00-C Incorporates OCAS review comments. Also incorporates recent 

direction from OCAS regarding the calculation and use of coworker 

doses. Initiated by Steven E. Merwin.

07/29/2005 00 First approved issue. Training required: As determined by the Task 

Manager. Initiated by Steven E. Merwin.
Document No. ORAUT-OTIB-0040 Revision No. 00 Effective Date: 07/29/2005 Page 3 of 10

TABLE OF CONTENTS

Section

Publication Record ..............................................................................................................................

Page

2

1.0 Purpose ......................................................................................................................................4

2.0 Background................................................................................................................................. 4

3.0 General Approach.......................................................................................................................5

4.0 Applications and Limitations........................................................................................................5

5.0 References ................................................................................................................................. 5

6.0 PGDP Coworker Data Development ...........................................................................................6

7.0 PGDP Coworker Annual Dose Summaries .................................................................................7

8.0 PGDP Coworker Annual Dose Distributions................................................................................9

LIST OF TABLES

Table Page

6-1 Missed external doses based on PGDP Occupational External Dosimetry 

TBD and ORAUT-OTIB-0017...................................................................................................7

8-2 Annual PGDP external coworker doses modified to account for missed 

dose (rem) .............................................................................................................................10
Document No. ORAUT-OTIB-0040 Revision No. 00 Effective Date: 07/29/2005 Page 4 of 10

1.0 PURPOSE

Technical Information Bulletins (TIBs) are general working documents that provide guidance 

concerning the preparation of dose reconstructions at particular sites or categories of sites. They will 

be revised in the event additional relevant information is obtained. TIBs may be used to assist the 

National Institute for Occupational Safety and Health in the completion of individual dose 

reconstructions.

In this document the word “facility” is used as a general term for an area, building, or group of 

buildings that served a specific purpose at a site. It does not necessarily connote an “atomic weapons 

employer facility” or a “Department of Energy facility” as defined in the Energy Employees 

Occupational Illness Compensation Program Act of 2000 (42 U.S.C. § 7384l(5) and (12)).

The purpose of this TIB is to provide information to allow ORAU Team dose reconstructors to assign 

doses to Portsmouth Gaseous Diffusion Plant (PGDP) workers who have no or limited monitoring 

data, based on site coworker data. The data in this TIB are to be used in conjunction with ORAUTOTIB-0020, “Use of Coworker Dosimetry Data for External Dose Assignment.”1 

2.0 BACKGROUND

The ORAU Team is conducting a series of coworker data studies to permit dose reconstructors to 

complete certain cases for which external and/or internal monitoring data are unavailable or 

incomplete. Cases not having complete monitoring data may fall into one of several categories, 

including:

• The worker was unmonitored and, even by today’s standards, did not need to be monitored 

(e.g., a non-radiological worker).

• The worker was unmonitored, but by today’s standards would have been monitored.

• The worker may have been monitored but the data are not available to the dose reconstructor.

• Partial information is available, but it is insufficient to facilitate a dose reconstruction.

As described in ORAUT-OTIB-0020,1 some cases not having complete monitoring data can be 

processed based on assumptions and methodologies that do not involve coworker data. For 

example, many cases falling in the first category above can be processed by assigning ambient 

external and internal doses based on information in the relevant site Technical Basis Documents 

(TBDs).

As described in the PGDP External Dosimetry TBD,2

 operations at the site began in 1954. Initially, 

personnel received dosimetry based on job assignments. In 1960, dosimeters were issued to all 

employees, contractors, and visitors as part of their personnel badge; however, not all visitor or 

contractor badges were analyzed. There does not appear to be any significant administrative practice 

that would jeopardize the integrity of the recorded dose of record; however, the corrections 

recommended by the TBD (e.g., 1.125 for the reported deep photon dose between 1981 and 1986) 

are appropriate for the coworker doses established in this TIB, since the doses are based on the 

PGDP dosimetry data.
Document No. ORAUT-OTIB-0040 Revision No. 00 Effective Date: 07/29/2005 Page 5 of 10

3.0 GENERAL APPROACH

As described in ORAUT-OTIB-0020,1 the general approach to developing coworker data for cases 

without external monitoring data involves two phases. The first (Phase I) permits cases to be 

processed when a “best and final” estimate of dose is not required for claim determination. The 

second (Phase II) facilitates the assignment of “best and final estimates” of dose, when necessary. 

This initial revision of this TIB provides coworker external dosimetry summary statistics applicable to 

Phase I dose reconstructions; coworker dose distributions applicable to Phase II dose reconstructions 

will be made available in a subsequent revision. 

4.0 APPLICATIONS AND LIMITATIONS

1. Some PGDP workers may have worked at more than one major site within the DOE complex 

during their employment history. Thus, the data presented herein must be used with caution to 

ensure that for clearly non-compensable cases, unmonitored external doses from multiple site 

employment have been overestimated. This will typically require the availability of External 

Coworker Dosimetry Data TIBs for all relevant sites.

2. Summary statistics based on PGDP dosimetry data presented in this TIB do not extend beyond 

1992 because at the time this TIB was drafted, later data were not available. However, the 

absence of these data (and the subsequent development of dose distributions) should not 

interfere with the processing of most PGDP cases having a lack of external dosimetry data since

well before 1992 the monitoring and reporting practices at the site ensured that essentially all 

workers with a potential for external radiation exposure were monitored and the results are readily 

accessible. Should the need arise and sufficient data become available, coworker dosimetry data 

beyond the year 1992 will be presented in a subsequent revision to this TIB.

3. The data presented in this TIB address penetrating radiation from gamma radiation and nonpenetrating radiation from beta radiation. Neutron data are not presented. However, the potential 

for neutron exposures at the PGDP is limited to certain site areas and facilities, and the associated 

doses were low.

2

 Therefore, the PGDP TBD should be used as the basis for assigning neutron 

doses, when relevant, in addition to the photon and/or beta doses assigned in accordance with 

this TIB.

4. External on-site ambient doses should not be included in addition to the coworker doses assigned 

in accordance with this TIB, because any such doses would have already been included in the 

dosimetry results reported by the site which were used as the basis for the coworker dose 

distributions presented below.

2,4

5.0 REFERENCES

1. ORAU Team, ORAUT-OTIB-0020, Use of Coworker Dosimetry Data for External Dose 

Assignment, Rev 00, December 29, 2004. 

2. ORAU Team, ORAUT-TKBS-0015-6, Technical Basis Document for the Portsmouth Gaseous 

Diffusion Plant – Occupational External Dose, Rev 00, January 18, 2005. 

3. NIOSH (National Institute for Occupational Safety and Health), External Dose Reconstruction 

Implementation Guideline, Rev. 0, OCAS-IG-001, Office of Compensation Analysis and Support, 

Cincinnati, Ohio, 2002.
Document No. ORAUT-OTIB-0040 Revision No. 00 Effective Date: 07/29/2005 Page 6 of 10

4. ORAU Team, ORAUT-PROC-0060, External On-Site Ambient Dose Reconstruction for DOE 

Sites, Rev 00, March 7, 2005. 

5. ORAU Team, ORAUT-OTIB-0017, Interpretation of Dosimetry Data for Assignment of Shallow 

Dose, Rev 00, January 19, 2005.

6.0 PGDP COWORKER DATA DEVELOPMENT

Dosimetry data for monitored PGDP workers were obtained from the site in a database named 

“HR_prior_1993.mdb.” Historical external data through 1992 were contained in a table within the 

database titled “Doseext_dat.” In all cases, the reported data corresponded to individual badge 

readings of deep dose (i.e., penetrating gamma radiation) and shallow dose (i.e., penetrating plus 

non-penetrating radiation). 

The annual data calculated based on the summation of individual badge results were prorated to 

account for partial years of employment based on an analysis of the length of employment associated 

with each year (see Section 7.0 for further discussion). The data were prorated so that coworker 

doses representing a full year of monitored employment could be derived; this permits the dose 

reconstructor to assign appropriate doses based on specific employment dates and job descriptions. 

The validity of the data selected for coworker dose development was confirmed by selecting a

sampling of claimant dosimetry data submitted by the site as part of the EEOICPA Subtitle B program

and comparing it to the data selected as described above. A review of annual data for ten claimants 

covering more than 130 worker-years of monitored employment at PGDP indicated excellent 

agreement between the two data sets. Specifically, a perfect match was found for more than 99% of 

the reported values. It is concluded that the data cited above are acceptable for the development of 

coworker doses for the PGDP. 

Adjustment for Missed Dose

According to the External Dose Reconstruction Implementation Guideline,3 missed doses are to be 

assigned for null dosimeter readings to account for the possibility that doses were received but not 

recorded by the dosimeter or reported by the site. Annual missed doses are calculated by multiplying 

the number of null badge readings by the reported dosimeter limit of detection (LOD) and summing 

the results. These values are used as the 95th percentile of a lognormal distribution for the purpose 

of calculating probability of causation (which is determined by the Department of Labor); thus, in IREP 

the calculated missed doses are multiplied by 0.5 and entered in Parameter 1, and a value of 1.52 is 

entered in Parameter 2, to represent the geometric mean and geometric standard deviation, 

respectively.

The assignment of missed doses for monitored workers is particularly significant for PGDP claimants

in the 1950s when badge exchanges were frequent. Table 6-1 lists the maximum annual missed 

dose by era and type of radiation (penetrating gamma and non-penetrating) based on information 

presented in the site TBD2 and ORAUT-OTIB-0017.5 
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Table 6-1. Missed external doses based on PGDP Occupational External Dosimetry TBD and 

ORAUT-OTIB-0017. 

Period

Penetrating 

LOD (rem)

Non-penetrating 

LOD (rem)a

Exchange 

frequency

Maximum annual missed dose (rem)

Penetrating Non-penetrating

1954–1956 0.03 0.03 Weekly 1.560 1.560

1957 0.03 0.03 Variedb 1.230 1.230

1958 0.03 0.03 Variedc 0.990 0.990

1959 0.03 0.03 Variedd 0.690 0.690

1960 0.03 0.03 Variede 0.390 0.390

1961–1963 0.03 0.03 Monthly 0.360 0.360

1964 0.03 0.03 Variedf 0.240 0.240

1965–1980 0.03 0.03 Quarterly

g 0.120 0.120

1981–1982 0.015 Not applicableh Monthly 0.180 Not applicableh

1983–1998 0.01 0.04 Quarterly 0.040 0.160

1999–Present 0.01 0.03 Quarterly 0.040 0.120

a. ORAUT-OTIB-0017 (Attachment C) provides an explanation for the non-penetrating LODs for the PGDP.

b. The exchange frequency was weekly, then biweekly during this year. 

c. The exchange frequency was biweekly, then weekly (maximizing assumption) during this year. 

d. The exchange frequency was weekly (maximizing assumption), then every four weeks during this year. 

e. The exchange frequency was every four weeks, then monthly (maximizing assumption) during this year. 

f. The exchange frequency was monthly (maximizing assumption), then quarterly during this year. 

g. From 1975 through 1980 selected female employees were monitored monthly. However, this frequency was not used in 

this table since all such employees would have been monitored and coworker data would not be applied in the 

reconstruction of their dose.

h. See ORAUT-OTIB-0017 (Attachment C) for an explanation. 

Special Considerations

Certain aspects of the external dosimetry practices at the PGDP documented in the TBD2 were 

considered in the analysis of the site data. These include:

• In some cases, values less than the dosimeter LODs (listed in Table 6-1 above) were reported 

by the site. For example, in the 1990s single-digit doses in millirem were reported 

occasionally, even though the LOD was considered to be 10 mrem. This does not appear to 

be an issue prior to 1981, however, since a review of case submittals covering employment 

during that era did not reveal examples of positive badge readings reported less than the 

stated LOD for that period (30 mrem). 

• As discussed previously, the data available to analyze coworker doses represent dose 

summaries for individual workers from individual badge data with unknown specific monitoring 

dates other than the relevant calendar years. Because these data may include partial work 

years, the average annual doses reported tend to underestimate the average annual doses 

received by employees who worked an entire year. 

As described in Section 7.0 below, a claimant-favorable approach was adopted in the development of 

coworker dose summaries, and this approach is intended to account for any underestimate of doses 

to radiological workers at the PGDP based on the considerations described above.

7.0 PGDP COWORKER ANNUAL DOSE SUMMARIES

Based on the information and approaches described above, PGDP coworker annual external 

dosimetry summaries were developed for use in the evaluation of external dose for certain claimants 

potentially exposed to workplace radiation, but with no or limited monitoring data provided by DOE. 

These summaries were developed using the following steps:
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1. As described in Section 6.0 above, the annual deep and shallow doses obtained from summing 

the individual badge data were modified to account for partial years of employment. This 

adjustment was made by analyzing the NOCTS employment data for PGDP workers and adjusting 

the reported doses upward by an appropriate multiplier corresponding to the average fraction of a 

year an employee worked at the site. For example, if in a particular calendar year the average 

employment period for all PGDP employees in NOCTS was 11 months, the reported annual doses 

were multiplied by 12/11, or 1.09. This permits the dose reconstructor to assign an appropriate 

prorated dose to account for partial years of employment or potential exposure. 

2. One-half of the maximum annual missed doses listed in Table 6-1 were added to the annual 

doses from Step 1 (except for reported positive doses, in which case the maximum missed dose 

was reduced by the dose corresponding to one badge exchange because it is not possible that all 

individual badge results were zero if a positive annual dose was reported).

3. The 50th and 95th percentile annual penetrating and shallow doses were derived from the doses 

calculated in Step 2 by ranking the data into cumulative probability curves and extracting the 50th 

and 95th percentile doses for each year.

4. Because the reported shallow doses include both penetrating and non-penetrating radiation, the 

percentile doses pertaining to penetrating radiation identified in Step 3 were subtracted from the 

percentile doses pertaining to the reported shallow doses to derive percentile doses pertaining to 

non-penetrating radiation. 

5. The results are presented in Table 8-2 below. These percentile doses should be used for selected 

PGDP workers with no or limited monitoring data using the methodologies outlined in Section 7.0 

of ORAUT-OTIB-0020.1

 In general, the 50th percentile dose may be used as a best estimate of a 

worker’s dose when professional judgment indicates the worker was likely exposed to intermittent 

low levels of external radiation. The 50th percentile dose should not be used for workers who 

were routinely exposed. For routinely exposed workers (i.e., workers who were expected to have 

been monitored), the 95th percentile dose should be applied. For workers who are unlikely to 

have been exposed, external on-site ambient dose should be used rather than co-worker doses. 

Doses to organs impacted only by penetrating radiation (e.g., organs other than the skin, breast, and 

testes) are calculated based only on the “Gamma” columns in Table 8-2 combined with the 

appropriate organ dose conversion factors (DCFs).3

 Doses to the skin, breast, and testes (and any

other cancer location potentially impacted by non-penetrating radiation) are determined based on both

With the methodology described above, null values for non-penetrating dose can occur because of 

the subtraction of the reported penetrating doses from the reported shallow doses and the claimantfavorable method described above to establish coworker doses based on the addition of potential 

missed doses. However, a “zero” value in Table 8-2 for non-penetrating dose will not result in a dose 

of zero being assigned to an organ such as the skin. For example, the 50th percentile dose to the 

skin in 1960 would be assigned entirely as 0.195 rem of photons. This approach does 

the “Gamma” and “Non-penetrating” columns; gamma doses are assigned as photons with an energy 

range consistent with information in the external dosimetry TBD for the PGDP,

2 and non-penetrating 

doses are assigned as electrons >15 keV with corrections applied to account for clothing attenuation 

or other applicable considerations.5

 

not result in an 

underestimation of probability of causation (which is determined by the Department of Labor) because 

assigning beta dose as gamma dose in IREP has no negative effect, since the radiation effectiveness 

factors are the same for >15 keV electrons and >250 keV photons, and are higher for 30–250 keV 

photons. 
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8.0 PGDP COWORKER ANNUAL DOSE DISTRIBUTIONS

Reserved
Document No. ORAUT-OTIB-0040 Revision No. 00 Effective Date: 07/29/2005 Page 10 of 10

Table 8-2. Annual PGDP external coworker doses modified to 

account for missed dose (rem). 

Year

Gamma

95th%

Gamma

50th%

Non-pen

95th%

Non-pen

50th%

1954 1.736 0.780 0.055 0.000

1955 1.104 0.874 0.048 0.000

1956 0.945 0.799 0.016 0.000

1957 0.714 0.615 0.335 0.000

1958 0.857 0.574 0.434 0.031

1959 1.164 0.591 0.579 0.040

1960 0.283 0.195 0.123 0.000

1961 0.240 0.180 0.086 0.000

1962 0.332 0.180 0.094 0.000

1963 0.360 0.180 0.051 0.000

1964 0.262 0.120 0.021 0.000

1965 0.140 0.060 0.050 0.000

1966 0.136 0.060 0.010 0.000

1967 0.122 0.060 0.005 0.000

1968 0.338 0.060 0.007 0.000

1969 0.281 0.085 0.011 0.000

1970 0.459 0.158 0.047 0.005

1971 0.281 0.060 0.065 0.000

1972 0.367 0.078 0.173 0.000

1973 0.407 0.077 0.087 0.000

1974 0.337 0.060 0.033 0.000

1975 0.474 0.078 0.114 0.000

1976 0.415 0.060 0.050 0.000

1977 0.365 0.078 0.050 0.000

1978 0.414 0.077 0.223 0.016

1979 0.181 0.060 0.174 0.000

1980 0.307 0.060 0.001 0.000

1981 0.120 0.090 N/A1 N/A1

1982 0.112 0.090 N/A1 N/A1

1983 0.053 0.020 0.112 0.060

1984 0.053 0.020 0.080 0.060

1985 0.045 0.020 0.083 0.060

1986 0.058 0.020 0.082 0.053

1987 0.063 0.020 0.083 0.046

1988 0.057 0.020 0.087 0.060

1989 0.063 0.020 0.091 0.047

1990 0.075 0.022 0.098 0.055

1991 0.057 0.020 0.101 0.050

1992 0.054 0.020 0.109 0.060 1 See ORAUT-OTIB-0017 for a discussion of the assignment of non-penetrating doses 

for the years 1981 and 1982.5