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 K25 Site 

Document Number: ORAUT-OTIB-0026

Revision: 00 PC-1 

Effective Date: 07/29/2005

Type of Document: OTIB

Supersedes: None

Subject Expert: Steven E. Merwin 

Document Owner

Approval: Signature on File Approval Date: 05/19/2005

Judson L. Kenoyer, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 05/19/2005

Richard E. Toohey, Project Director

Approval: Signature on File Approval Date: 05/31/2005

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-0026 Revision No. 00 PC-1 Effective Date: 07/29/2005 Page 2 of 10

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION 

NUMBER DESCRIPTION

01/10/2005 00-A New technical information bulletin to provide information to allow 

ORAU Team dose reconstructors to assign doses to certain workers 

at the K-25 site who have no or limited monitoring data, based on site 

coworker data. Initiated by Steven E. Merwin.

02/25/2005 00-B Incorporates NIOSH review comments. Initiated by Steven E. 

Merwin.

04/27/2005 00-C Incorporates additional responses to NIOSH comments. Initiated by 

Steven E. Merwin.

05/31/2005 00 First approved issue. Initiated by Steven E. Merwin.

06/30/2005 00 PC-1-A Page change initiated to incorporate recent direction from NIOSH

regarding the calculation and use of coworker doses. Initiated by 

Steven E. Merwin.

07/06/2005 00 PC-1-B No further changes occurred as a result of formal internal review. 

Initiated by Steven E. Merwin.

07/29/2005 00 PC-1 Approved page change revision. Page change incorporates recent 

direction from NIOSH regarding the calculation and use of coworker 

doses to pages 7, 8, 9, and 10. Text was modified in Sectons 6.0 

and 7.0. No sections were deleted. Retraining is not required. 

Initiated by Steven E. Merwin.

Approval:

Document Owner:

Judson L. Kenoyer, Task 3 Manager

Signature on File__________ _________ 07/20/2005

Signature on File__________ _____________ Richard E. Toohey, Projector Director07/26/2005

Signature on File__________ _____________ James W. Neton, Associate Director for Science07/29/2005
Document No. ORAUT-OTIB-0026 Revision No. 00 Effective Date: 05/31/2005 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 K-25 Coworker Data Development..............................................................................................6

7.0 K-25 Coworker Annual Dose Summaries....................................................................................8

8.0 K-25 Coworker Annual Dose Distributions ................................................................................ 10
Document No. ORAUT-OTIB-0026 Revision No. 00 Effective Date: 05/31/2005 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 Technical Information Bulletin (TIB) is to provide information to allow ORAU Team 

dose reconstructors to assign doses to workers at the Oak Ridge Gaseous Diffusion Plant (K-25) who 

have no or limited monitoring data, based on site coworker data. The data in this TIB are to be used 

in conjunction with ORAUT-OTIB-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.

• the worker may have partial information, but the available information is insufficient to permit a 

dose reconstruction to occur.

As described in ORAUT-OTIB-0020, 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 K-25 External Dosimetry TBD,2 dosimeters were issued to the entire workforce 

beginning in 1951, but only a fraction of the dosimeters were actually processed. According to the 

TBD, this practice continued until 1980 when all dosimeters were processed. This information is 

largely consistent with the data provided to NIOSH in conjunction with this program; however, the data 

are largely complete and sufficient for external dose reconstruction beginning in 1975, indicating that 

the monitoring and reporting of external doses for most workers at the site began somewhat earlier 

than is indicated in the TBD. 
Document No. ORAUT-OTIB-0026 Revision No. 00 Effective Date: 05/31/2005 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 (Phase I) permits cases to be 

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

second phase (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. At the Oak Ridge complex, many workers were employed at more than one of the major Oak 

Ridge sites (K-25, X-10 and Y-12). For some cases, employment information is provided in 

NOCTS as a multiple site listing such as “K-25/Y-12/X-10,” and the available information such as 

the DOE dosimetry records and claimant interview are insufficient to determine the actual work 

location(s), especially on an annual basis. Similarly, workers may have worked at more than one 

major site at different locations across 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.

2. Summary statistics based on K-25 dosimetry data presented in this TIB do not extend beyond 

1985 because at the time this TIB was drafted, data beyond 1985 were not available from the 

Comprehensive Epidemiologic Data Resource (CEDR). However, the absence of these data (and 

the subsequent development of dose distributions) should not interfere with the processing of 

most K-25 cases having a lack of external dosimetry data since well before 1985, 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 reliable data become available, coworker dosimetry data beyond the year 1985 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 locations 

within the K-25 site at which neutron exposures were possible are limited to specific areas, and 

the site TBD establishes a method for assigning neutron doses when relevant.2

 Therefore, the 

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 co-worker doses assigned 

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

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

presented below.4

5. The data in this TIB supersede the occupational dose data in Tables 6-4 and 6-5 of the K-25 

Occupational External Dose TBD.2

 

5.0 REFERENCES

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

Assignment, Rev 00, December 29, 2004. 
Document No. ORAUT-OTIB-0026 Revision No. 00 Effective Date: 05/31/2005 Page 6 of 10

2. ORAU Team, ORAUT-TKBS-0009-6, Technical Basis Document for the K-25 Site – Occupational 

External Dose, Rev 00, November 24, 2004.

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.

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

Environmental Dose, Rev 00, December 29, 2004.

6.0 K-25 COWORKER DATA DEVELOPMENT

Dosimetry data for monitored K-25 workers from the CEDR databases maintained by the U.S. 

Department of Energy (DOE) were selected for this evaluation. The CEDR data evaluated 

represented quarterly or annual gamma and non-penetrating (“skin”) dosimetry data provided by the 

K-25 site, which pertain to the shielded and open-window dosimetry readings and exclude neutron 

doses. As discussed in the site TBD on Occupational External Dose,2 low-energy (<30 keV) photons 

are not an issue at K-25, so the penetrating doses can be assumed to be associated entirely with 30-

250 keV photons, and the non-penetrating doses can be assumed to be associated entirely with > 15 

keV beta particles (electrons). 

The CEDR records represent annual data through 1975, after which the data are quarterly and have 

thus been summed and extrapolated in this analysis to derive annual doses. The year 1975 coincides 

with the time period in which the number of monitoring results in the database increased substantially 

from hundreds to thousands, indicating that the majority of personnel at the site were monitored 

starting in that timeframe. This is consistent with the NIOSH claimant data, which indicate that most 

people whose employment spanned the 1970s were not monitored (or the monitoring results were not 

available) until 1975 or shortly thereafter.

According to the site TBD,

2 monitoring at K-25 began in 1945 using dosimeter and processing support 

provided by the Oak Ridge National Laboratory (ORNL). Initially, only those workers entering 

controlled areas and likely to receive measurable dose received dosimeters. Starting in 1951, all 

workers received dosimeters as part of their security badges, but the dosimeters were not processed 

(by ORNL) unless the worker was deemed likely to have received measurable doses. According to 

the TBD, all dosimeters were processed beginning in 1980; however, as discussed in Section 2.0

above, both the CEDR and claimant data indicate that the great majority of the dosimeters were 

processed beginning in 1975.

Starting in 1976, the CEDR data are identified by quarter. Since, as described above, the site 

implemented a quarterly badge exchange cycle for essentially all workers starting in 1975,

2 these data 

represent directly the K-25 site monitoring results. Prior to 1976, the CEDR data appear to represent 

annual summary data. As shown in Table 1 below, prior to 1975 the badge exchange cycle was 

weekly, and most of the badges were not processed. Thus, the CEDR data in this period likely 

represent the summation of weekly dosimeter readings that may or may not encompass an entire

year of radiation exposure. 

The validity of the CEDR data 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 pertinent 

CEDR data. A review of annual data for eleven claimants covering 321 worker-years of employment 

at K-25 indicated excellent agreement between the two data sets. Specifically, a perfect match in the 

CEDR database was found for 10 of the 11 claimants for all relevant years. For one claimant, there 
Document No. ORAUT-OTIB-0026 Revision No. 00 PC-1 Effective Date: 07/29/2005 Page 7 of 10

were no positive data through 1985, the last year for which data are present in the CEDR database, 

so it was not possible to identify a unique match. It is concluded that the CEDR data are acceptable

for the development of coworker doses for the K-25 site, except for one quarter in 1977 which is

discussed in Section 7.0 below.

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 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 K-25 claimants

prior to 1975 when workers were monitored weekly. This is complicated by the fact that monitoring 

data are largely not available for this period because, as discussed above, the site apparently elected 

to have only a small fraction of the badges evaluated. Thus, it is generally not possible to obtain an 

accurate count of the number of null badge results prior to 1975 because the reported data reflect an 

annual summation of an unknown number of badge readings during the course of each year.

Table 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 TBD.2

 Although the TBD and a review of 

claimant data indicate that some workers may have been on a different cycle than is listed below, the 

majority of workers were on the typical schedule so the values provided in Table 1 are deemed 

appropriate for the adjustment of reported coworker doses to account for missed dose.

Table 1. Missed external doses based on K-25 TBD.

2

Period

Penetrating 

LOD (rem)

Non-penetrating 

LOD (rem)a Exchange frequency

Maximum annual missed dose (rem)

Penetrating Non-penetrating

1945-1974 0.03 0.03 Weekly 1.560 1.560

1975-1987 0.03 0.03 Quarterly 0.120 0.120

1988 – present 0.005 0.005 Monthlyb 0.060 0.060

a. K-25 does not distinguish between open-window and shielded dosimeter measurements when reporting 

minimum detectable levels (MDLs). It is implied that the MDLs should be considered the same.

b. The TBD indicates monthly exchanges for 1988 but does not indicate the exchange frequency for subsequent 

years. A review of claimant data for those years indicates that workers were on either a quarterly or monthly 

cycle. Therefore, a monthly cycle has been assumed, which is claimant favorable.

Special Considerations

Certain aspects of the external dosimetry practices at the K-25 site documented in the TBD2 were 

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

• In some cases, values less than the dosimeter LOD were reported by the site. For example, 

values as low as 10 or 20 mR were reported even though the LOD was considered to be 30 

mrem (or 30 mR) prior to 1988. 

• Prior to 1975, even though dosimeters were issued to essentially all workers, only a fraction of 

the dosimeters were actually processed. Thus, the possibility exists that the annual doses 

reported do not represent the actual annual doses received by some employees. 
Document No. ORAUT-OTIB-0026 Revision No. 00 PC-1 Effective Date: 07/29/2005 Page 8 of 10

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

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

radiological workers at the K-25 site based on the considerations described above.

7.0 K-25 COWORKER ANNUAL DOSE SUMMARIES

Based on the information and approaches described above, K-25 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 monitoring data provided by DOE. These summaries 

were developed using the following steps:

1. As described in Section 6.0 above, the penetrating and “skin” doses available from CEDR were 

converted to annual data by summing the reported quarterly data (1976 and later). Consistent 

with the guidelines in ORAUT-OTIB-0020,1 doses for individuals with less than four quarters of 

data for a particular year were converted to annual doses by extrapolating (i.e., one quarterly 

result was multiplied by 4; two quarterly results were multiplied by 2; and three quarterly results 

were multiplied by 1.333). In 1977, the result “104” appeared for numerous employees for one 

particular quarter; it appears that these values were nominal and were entered due to damaged 

film that could not be processed. Thus, all such values were eliminated from the analysis. Prior to 

1976, reported doses were not extrapolated since the reported values apparently represented 

doses received during the entire year.

2. One-half of the maximum annual missed doses listed in Table 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 “skin” 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 “skin” doses to derive percentile doses pertaining to 

non-penetrating radiation. 

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

K-25 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. 
Document No. ORAUT-OTIB-0026 Revision No. 00 PC-1 Effective Date: 07/29/2005 Page 9 of 10

Table 2. Annual K-25 external coworker doses modified to account 

for missed dose (rem). 

Year

Gamma

95th%

Gamma

50th%

Non-pen

95th%

Non-pen

50th%

1945 1.290 1.240 0.802 0.773

1946 1.455 0.805 0.884 0.065

1947 1.015 0.780 1.745 0.030

1948 1.264 0.780 0.838 0.000

1949 1.035 0.780 0.470 0.040

1950 0.841 0.780 0.115 0.000

1951 1.052 0.780 0.582 0.015

1952 0.951 0.780 1.549 0.035

1953 1.096 0.780 2.053 0.095

1954 0.913 0.780 1.088 0.000

1955 0.835 0.780 0.237 0.000

1956 0.855 0.780 0.566 0.000

1957 1.088 0.780 0.896 0.000

1958 1.049 0.780 1.325 0.000

1959 1.245 0.810 1.775 0.030

1960 1.154 0.791 1.078 0.024

1961 0.942 0.778 0.741 0.010

1962 0.824 0.780 0.663 0.022

1963 0.840 0.780 0.619 0.033

1964 0.841 0.780 0.363 0.034

1965 0.936 0.780 0.490 0.066

1966 0.952 0.780 1.188 0.040

1967 0.928 0.780 1.122 0.056

1968 0.906 0.780 0.506 0.000

1969 0.946 0.780 1.106 0.000

1970 1.041 0.780 1.436 0.038

1971 1.092 0.780 0.635 0.010

1972 1.034 0.779 0.381 0.088

1973 0.871 0.780 0.515 0.000

1974 1.065 0.835 0.339 0.008

1975 0.111 0.062 0.119 0.043

1976 0.149 0.060 0.069 0.000

1977 0.089 0.060 0.058 0.000

1978 0.136 0.052 0.043 0.013

1979 0.088 0.060 0.063 0.000

1980 0.145 0.060 0.160 0.000

1981 0.085 0.060 0.120 0.000

1982 0.060 0.060 0.425 0.000

1983 0.060 0.060 0.245 0.000

1984 0.060 0.060 0.125 0.000

1985 0.060 0.060 0.105 0.000

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 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 the 

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

range of 30-250 keV consistent with information in the external dosimetry TBD for the K-25 site,2 and 
Document No. ORAUT-OTIB-0026 Revision No. 00 PC-1 Effective Date: 07/29/2005 Page 10 of 10

non-penetrating doses are assigned as electrons >15 keV with corrections applied to account for 

clothing attenuation or other applicable considerations.

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 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 1948 would be assigned entirely as 0.780 rem of photons. This approach does not

The values in Table 2 do not show an increase in dose when the site began monitoring essentially all 

workers and reporting all results beginning in the mid 1970s. The values actually show a marked 

decrease compared to the values associated with the period during which a weekly badge exchange 

occurred. This is an indication that the methodology described in this TIB to adjust the reported 

annual doses based on potential missed dose more than compensates for any underreporting of 

annual doses by the site due to incomplete monitoring.

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. 

8.0 K-25 COWORKER ANNUAL DOSE DISTRIBUTIONS

Reserved