ORAU Team

Dose Reconstruction Project for NIOSH

Technical Information Bulletin – External Coworker 

Dosimetry Data for the X-10 Site 

Document Number:

ORAUT-OTIB-0021

Effective Date: 12/29/2004

Revision No.: 00

Controlled Copy No.: ______

Page 1 of 8

Subject Expert: Steven E. Merwin

Document Owner

Approval: Signature on File Date: 12/20/2004

Edward F. Maher, Task 5 Manager

Concurrence: Signature on File Date: 12/21/2004

Richard E. Toohey, Project Director

Approval: Signature on File Date: 12/29/2004

James W. Neton, Associate Director for Science

Supersedes:

None
Effective Date: 12/29/2004 Revision No.: 00 Document No. ORAUT-OTIB-0021 Page 2 of 8

RECORD OF ISSUE/REVISIONS

ISSUE 

AUTHORIZATION 

DATE

EFFECTIVE 

DATE

REV. 

NO. DESCRIPTION

Draft 11/30/2004 00-A New technical information bulletin to provide 

information to allow ORAU Team dose 

reconstructors to assign doses to workers at the 

X-10 site who have no or limited monitoring data, 

based on site coworker data. Initiated by Steven 

E. Merwin.

Draft 12/14/2004 00-B Incorporates internal review comments. Initiated 

by Steven E. Merwin.

Draft 12/16/2004 00-C Incorporates NIOSH review comments. Initiated 

by Steven E. Merwin.

12/29/2004 12/29/2004 00 First approved issue. Initiated by Steven E. 

Merwin.
Effective Date: 12/29/2004 Revision No.: 00 Document No. ORAUT-OTIB-0021 Page 3 of 8

1.0

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 X-10 site 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

PURPOSE

2.0

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

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

Such cases may fall into one of several categories, including:

BACKGROUND

• 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 the X-10 External Dosimetry TBD,2 most workers with a potential for radiation 

exposure at the X-10 site wore radiation dosimetry badges, especially after 1950. Also, the data 

provided to NIOSH in conjunction with this program are largely complete and sufficient for external 

dose reconstruction. Therefore, the coworker data provided in this TIB are expected to be of limited 

use for individuals who worked exclusively at the X-10 site. However, the specific work history is 

unknown for some individuals with no monitoring data who worked at more than one site within the 

Oak Ridge complex, and the data presented in this TIB will be a key component of dose

reconstructions for some of those workers. 

3.0

As described in ORAUT-OTIB-0020,1

 the general approach to applying 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) of the external coworker data approach 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. 

GENERAL APPROACH

4.0

1. Revision 0 of this document provides site coworker data and information that may be used only for 

cases not requiring best estimate calculations. Such cases include clearly non-compensable 

cases for which a higher external dose can be assigned than was likely to have been actually 

received, or clearly compensable cases for which a lower external dose can be assigned than was 

likely to have been actually received. Revision 1 of this document will provide dose distributions 

APPLICATIONS AND LIMITATIONS
Effective Date: 12/29/2004 Revision No.: 00 Document No. ORAUT-OTIB-0021 Page 4 of 8

and additional information based on the data presented herein to permit the processing of cases 

requiring a best estimate analysis.

2. 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 

and compensable cases, unmonitored external doses from multiple site employment have been 

overestimated and underestimated, respectively.

3. Summary statistics based on X-10 dosimetry data presented in this TIB do not extend beyond 

1985 because reliable data were not available at the time this TIB was drafted. However, the 

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

interfere with the processing of most X-10 cases having a lack of external dosimetry data, since in 

recent years the monitoring practices at X-10 (and the other Oak Ridge sites) were sufficiently 

robust to ensure that essentially all workers with a potential for external radiation exposure were 

monitored. Coworker dosimetry data beyond the year 1985 will be presented in a subsequent 

revision to this TIB should the need arise and sufficient reliable data become available.

4. The data presented in this TIB address penetrating radiation from gamma radiation and nonpenetrating radiation from beta radiation (and potentially low-energy photons). Neutron data are 

not presented. However, the locations within the X-10 site at which neutron exposures were 

possible are limited, and neutron doses were monitored separately for most workers having a 

potential for neutron exposure.2

 Therefore, it is not anticipated that the lack of coworker neutron 

dosimetry data in this TIB will negatively impact X-10 dose reconstructions. Coworker dosimetry 

data for neutron exposures will be presented in a subsequent revision to this TIB should the need 

arise and sufficient reliable data become available.

5.0

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

Assignment. 

REFERENCES

2. ORAU Team, ORAUT-TKBS-0012-6, Technical Basis Document for the Oak Ridge National 

Laboratory – Occupational External Dose. 

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.

6.0

Dosimetry data for monitored X-10 workers maintained by the Comprehensive Epidemiologic Data 

Resource (CEDR) maintained by DOE were selected for this evaluation. However, for the year 1966, 

data maintained by the ORAU Center for Epidemiologic Research (CER) were selected because 

CEDR data were not available for that year.

X-10 COWORKER DATA DEVELOPMENT
Effective Date: 12/29/2004 Revision No.: 00 Document No. ORAUT-OTIB-0021 Page 5 of 8

The CEDR data evaluated represented quarterly or annual gamma and non-penetrating (“skin”) 

dosimetry data maintained by the X-10 site, which pertain to the shielded and open-window dosimetry 

readings and exclude neutron doses. Starting in 1961, the CEDR data are identified by quarter. 

Since the site implemented a quarterly badge exchange cycle for essentially all workers starting in the 

third quarter of 1956, these CEDR data represent directly the X-10 site monitoring results. Prior to 

1961, the CEDR data for X-10 typically include from one to three monitoring results each year for an 

individual. This is as indication that the result represents annual summaries of the quarterly or weekly 

(which was the typical exchange frequency prior to the third quarter of 1956) dosimetry data. The fact 

that two or three results are associated with some individuals is an indication that dosimetry results 

from Oak Ridge sites other than X-10 (e.g., K-25 and Y-12) were included. It does not appear 

possible based on either the CEDR or CER data to separate the doses associated with the individual 

Oak Ridge sites prior to 1961; thus, these data should be used with caution by the dose 

reconstructors. 

The validity of the CEDR data (and CER data for 1966) was confirmed by comparing a random 

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

B program. A review of data for ten claimants covering 253 worker-years of employment at X-10 

indicated generally good agreement between the two data sets. Specifically, the annual penetrating 

doses extracted from the two data sets matched perfectly in 92% and 74% of the 253 annual results 

for gamma and non-penetrating doses, respectively. Importantly, when the data did not match, the 

CEDR data were higher more than half of the time, suggesting that relying on the CEDR data for 

coworker dose reconstruction would not result in a negative bias against the claimants. Additionally, 

part of the mismatches were apparently attributable to quarterly doses that overlapped two calendar 

years being assigned two different years in the two data sets. Also, some of the instances in which 

the CEDR annual doses were less than the annual doses extracted from the EEOICPA claimant data 

were attributable to an occasional missing quarter of CEDR data; however, these instances do not 

result in an underestimation of coworker dose because of the extrapolation approach described in 

Section 7.0 below. Overall, the CEDR data (and CER data for 1966) are considered to be acceptable

for the development of coworker doses for the X-10 site. 

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. 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 X-10 claimants, 

because there is historically a high percentage of null dosimeter results for this site. By the 1980s 

more than 90% of quarterly penetrating dose readings and

Because X-10 claimants with null monitoring data are assigned missed dose, including those 

claimants who likely had no potential for external radiation exposure during their employment, the 

reported annual doses were zero. By 

comparison, in the late 1950s, less than one-third of the quarterly results were zero. This is largely 

due to the site monitoring practices and the increasing robustness of radiological controls over time 

(starting in 1951, all regular workers wore a combination dosimeter and security badge regardless of 

work area - the transition to this system was completed by 1953).
Effective Date: 12/29/2004 Revision No.: 00 Document No. ORAUT-OTIB-0021 Page 6 of 8

assignment of doses to workers with no monitoring data based on coworker data must also account 

for the assignment of missed dose.

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 indicates that 

some workers may have been on a dosimeter exchange cycle that was less or more frequent than the

typical cycle, the great 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 X-10 external TBD. 

Period

Penetrating 

LOD (rem)

Non-penetrating 

LOD (rem)a,b Exchange frequency

Maximum annual missed dose (rem)

Penetrating Non-penetrating

June 1944- June 1956 0.03 0.03 Weekly 1.560 1.560

July 1956 – 1974 0.03 0.03 Quarterly 0.120 0.120

1975 – present 0.01 0.01 Quarterly 0.040 0.040

a. Non-penetrating LODs are based on the TBD statement that “for assigning missed shallow dose, dose 

reconstructors should apply the deep dose values...unless there is reason to suspect exposure to a field 

consisting primarily of low-energy electrons.”2

b. The listed LODs are not reliable for low-energy beta particles. The X-10 TBD2 should be reviewed to identify 

potential exposure scenarios involving low-energy beta particles to determine whether the scenarios may apply 

to particular claimants. Note that cancer location is an important consideration, because beta particles with a 

low enough energy to render the tabulated LODs unreliable would deliver little dose through clothing.

Other Considerations

Certain aspects of the external dosimetry practices at the X-10 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 1951, dosimeter use was not expressly required for all workers – badges were 

typically provided only for people who entered the restricted area, and the badges were worn 

based on an “honor system” rather than a strict requirement. A review of claimant data 

indicates that most such workers actually wore the badges when provided.

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 X-10 site based on the considerations described above.

7.0

Based on the information and approaches described above, X-10 coworker annual external dosimetry 

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

exposed to workplace radiation, but with no monitoring data provided by DOE. These summaries 

were developed using the following steps:

X-10 COWORKER ANNUAL DOSE SUMMARIES

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

for 1966) were converted to annual data by summing the reported quarterly data (1961 and later) 

or summing the annual results that apparently cover the major Oak Ridge sites. 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 
Effective Date: 12/29/2004 Revision No.: 00 Document No. ORAUT-OTIB-0021 Page 7 of 8

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

multiplied by 1.333). Prior to 1961, reported doses were not extrapolated since the reported 

values apparently represented doses received during the entire year. 

2. The 50th, 95th and 99th percentile annual penetrating and skin doses were derived for two 

scenarios: excluding and including reported zeroes.

3. The 50th, 95th and 99th percentile doses based on the exclusion of zeroes were used as the 

basis for the coworker data set, since these are representative of radiological worker doses which 

are the principal focus of the coworker studies. However, to ensure claimant favorability, the 

percentile doses with zero results included were evaluated, and if the addition of one-half of the 

maximum annual missed doses (listed in Table 1) to these percentile doses resulted in values 

exceeding the percentile doses based on the exclusion of zeroes, the latter were replaced with the 

former.

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

X-10 workers with no or limited monitoring data using the methodologies outlined in Section 7.0 of 

ORAUT-OTIB-0020.1

 Should these data prove insufficient for the completion of dose 

reconstructions, “best estimate” coworker dose distributions should be used as documented in 

Section 8.0 below and in accordance with Section 8.0 of ORAUT-OTIB-0020.1

 

Table 2. Annual X-10 external coworker doses modified to account 

for missed dose (rem). 

Year

Gamma 

99th%

Gamma

95th%

Gamma

50th%

Non-pen

99th%

Non-pen

95th%

Non-pen

50th%

1943 1.762 1.370 0.780 0.000 0.000 0.000

1944 3.861 2.810 0.915 0.507 0.235 0.025

1945 2.950 1.465 0.780 4.559 1.325 0.000

1946 2.501 1.373 0.780 6.947 3.895 0.000

1947 3.363 1.329 0.780 5.286 2.030 0.000

1948 2.564 1.290 0.780 4.593 0.835 0.030

1949 3.999 2.542 0.780 4.595 2.340 0.000

1950 3.113 1.604 0.780 3.967 2.003 0.000

1951 4.356 2.585 0.780 5.163 2.970 0.000

1952 6.131 3.750 0.780 5.303 2.881 0.040

1953 5.081 2.539 0.800 4.821 2.632 0.045

1954 5.508 2.206 0.780 8.202 3.244 0.070

1955 4.686 2.541 0.820 8.119 4.649 0.073

1956 4.550 2.161 0.500 3.996 1.592 0.040

1957 5.463 2.035 0.180 4.303 1.796 0.195

1958 3.156 1.610 0.320 3.249 1.087 0.195

1959 3.600 1.788 0.270 3.456 1.329 0.090

1960 2.879 1.304 0.110 2.401 0.936 0.055

1961 2.020 0.980 0.100 1.344 0.430 0.030

1962 2.268 1.020 0.110 1.479 0.570 0.043

1963 2.030 1.006 0.120 1.200 0.415 0.030

1964 2.067 0.904 0.090 1.397 0.502 0.030

1965 2.371 1.220 0.080 1.729 0.766 0.060

1966 2.816 1.230 0.080 3.824 0.740 0.070

1967 2.828 1.360 0.110 2.240 0.923 0.080

1968 2.669 1.302 0.100 2.506 0.663 0.060

1969 2.302 1.192 0.110 2.043 0.593 0.050
Effective Date: 12/29/2004 Revision No.: 00 Document No. ORAUT-OTIB-0021 Page 8 of 8

1970 1.850 1.029 0.100 2.190 0.581 0.060

1971 2.109 1.100 0.090 1.939 0.565 0.060

1972 2.435 1.386 0.100 4.156 0.746 0.060

1973 2.238 1.210 0.080 2.246 0.370 0.050

1974 1.485 0.750 0.060 1.123 0.188 0.020

1975 2.080 1.188 0.090 2.283 0.470 0.020

1976 1.992 1.121 0.060 0.544 0.140 0.010

1977 2.356 0.980 0.060 0.324 0.190 0.010

1978 1.901 1.021 0.100 0.550 0.315 0.010

1979 1.977 1.194 0.100 0.749 0.377 0.015

1980 2.312 1.269 0.080 3.124 0.583 0.010

1981 1.954 1.176 0.160 1.626 0.986 0.050

1982 1.612 1.030 0.180 2.074 0.620 0.080

1983 1.829 1.237 0.250 2.190 0.796 0.055

1984 1.740 0.949 0.175 1.699 0.519 0.060

1985 1.300 0.940 0.170 1.400 0.330 0.080

Dose 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 “zero” values for non-penetrating dose result from occurrences when the calculated missed 

doses (as described in Step 3 above) are used as the basis for the gamma and non-penetrating 

coworker doses; since the LODs are the same for both types of radiation (see Table 1), the 

subtraction of the two values results in a net non-penetrating dose of zero. This approach does 

the 

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

consistent with information in the external dosimetry TBD for the X-10 site,2 and non-penetrating 

doses are assigned as electrons >15 keV (or <30 keV photons if appropriate) with corrections applied 

to account for clothing attenuation or other relevant considerations. This approach explains why the 

occasional “zero” values 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 50-th percentile dose to the skin in 1943 

would be assigned entirely as 0.780 rem of photons.

not

8.0

result in an underestimation of dose because there cannot be missed dose for both penetrating and 

non-penetrating radiations at the LOD simultaneously without the open-window element recording a 

positive value (e.g., if the LOD is 30 mrem for both elements and a penetrating dose of 30 mrem is 

received in addition to a non-penetrating dose of 30 mrem), the open-window reading would 

effectively be twice the LOD, or 60 mrem). Additionally, assigning beta dose as gamma dose in IREP 

has no negative effect because the radiation effectiveness factors are the same for >15 keV electrons 

and >250 keV photons, and are higher for both <30 keV photons and 30-250 keV photons. 

Reserved

X-10 COWORKER ANNUAL DOSE DISTRIBUTIONS