ORAU TEAM

Dose Reconstruction

Project for NIOSH

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

Page 1 of 22

Document Title:

Paducah Gaseous Diffusion Plant – 

Occupational Medical Dose

Document Number: ORAUT-TKBS-0019-3 

Revision: 01

Effective Date: 09/26/2006

Type of Document: TBD

Supersedes: Revision 00

Subject Expert: James E. Turner

Approval: Signature on File Approval Date: 09/18/2006

Daniel Mantooth, Document Owner

Approval: Signature on File Approval Date: 09/18/2006

John M. Byrne, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 09/18/2006

Edward F. Maher, Task 5 Manager

Concurrence: Signature on File Concurrence Date: 09/14/2006

Kate Kimpan, Project Director

Approval: Brant A. Ulsh Signature on File for Approval Date: 09/26/2006

James W. Neton, Associate Director for Science

 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-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 2 of 22

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION 

NUMBER DESCRIPTION

02/05/2004 00 New technical basis document for the Paducah Gaseous Diffusion 

Plant – Occupational Medical Dose. First approved issue. Initiated 

by Jay J. Maisler.

09/26/2006 01 Revised as a result of biennial review. Approved Revision 01.

Constitutes a total rewrite of the document. Incorporates internal

formal review comments. Incorporates NIOSH formal review 

comments. This revision results in a reduction in assigned dose and 

no PER is required. Training required: As determined by the Task 

Manager. Initiated by Daniel Mantooth.
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 3 of 22

TABLE OF CONTENTS

SECTION TITLE PAGE

Acronyms and Abbreviations ...............................................................................................................5

3.1 Introduction ..............................................................................................................................6

3.1.1 Purpose..............................................................................................................................6

3.1.2 Scope................................................................................................................................. 7

3.2 Examination Frequencies.........................................................................................................7

3.3 Equipment And Techniques .....................................................................................................7

3.4 Organ Dose Calculations .........................................................................................................9

3.4.1 Air Kerma for Exposures from March 1975 to Present........................................................9

3.4.2 Air Kerma for Exposures from 1952 through February 1975............................................. 10

3.4.3 Dose Equivalents per Exposure for Organs Included in ICRP 

Publication 34...................................................................................................................10

3.4.4 Dose Equivalents per Exposure for Organs Not Included in ICRP 

Publication 34...................................................................................................................11

3.4.5 Combined Dose Equivalents for PA and LAT Exposures.................................................. 12

3.5 Uncertainty.............................................................................................................................12

3.6 Dose Reconstruction..............................................................................................................14

3.6.1 Organ Dose Equivalents Favorable to Claimants per Examination................................... 14

3.6.2 Optional Initial Screening..................................................................................................14

References ........................................................................................................................................17

Glossary ............................................................................................................................................18

ATTACHMENT A, ORGAN DOSE EQUIVALENTS FOR LUMBAR SPINE EXAMINATIONS.............19

ATTACHMENT B, ERROR PROPAGATION FOR KERMA.................................................................21
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 4 of 22

LIST OF TABLES

TABLE TITLE

3-1 Frequency of chest X-ray examinations ...................................................................................

PAGE

7

3-2 PGDP X-ray equipment............................................................................................................8

3-3 Operating parameters ..............................................................................................................8

3-4 Average mAs for exposures of workers of different body size .................................................. 9

3-5 Air kerma at skin entrance for PA and LAT views................................................................... 10

3-6 Dose equivalent per PA and per LAT exposure for organs included in 

ICRP Publication 34...............................................................................................................11

3-7 Dose equivalent per PA and per LAT exposure for organs not in ICRP 

Publication 34 ........................................................................................................................12

3-8 Organ dose equivalents for combined PA and LAT examinations .......................................... 13

3-9 Potential sources of uncertainty in organ dose equivalent assessments ................................ 14

3-10 Organ dose equivalents favorable to claimants per examination 

consisting of one PA and one LAT exposure.......................................................................... 15

3-11 Upper-bound organ dose equivalents per examination for screening ..................................... 16

A-1 Organ dose equivalents for lumbar spine examinations ......................................................... 19
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 5 of 22

ACRONYMS AND ABBREVIATIONS

AP anterior-posterior (X-ray view)

cGy centigray

cm centimeter

DCF dose conversion factor

DOE U.S. Department of Energy

EEOICPA Energy Employees Occupational Illness Compensation Program Act

GE General Electric Corporation

Gy gray

HVL half-value layer

ICRP International Commission on Radiological Protection

in. inch

IREP Interactive RadioEpidemiological Program

kVp applied kilovoltage

LAT lateral (X-ray view)

mA milliampere

mAs milliampere second

mm millimeter

mR milliroentgen

mrad millirad

mrem millirem

NIOSH National Institute for Occupational Safety and Health

PA posterior-anterior (X-ray view)

PGDP Paducah Gaseous Diffusion Plant

POC probability of causation

s second

SID source-to-image distance

SSD source-to-skin distance

TBD technical basis document

U.S.C. United States Code

yr year

§ Section
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 6 of 22

3.1 INTRODUCTION

3.1.1

Technical basis documents and site profile documents are not official determinations made by the 

National Institute for Occupational Safety and Health (NIOSH) but are rather general working 

documents that provide historic background information and guidance to assist in the preparation of 

dose reconstructions at particular sites or categories of sites. They will be revised in the event 

additional relevant information is obtained about the affected site(s). These documents may be used 

to assist NIOSH staff in the completion of the individual work required for each dose reconstruction.

Purpose

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 [DOE] facility” as defined in the Energy Employees 

Occupational Illness Compensation Program Act [EEOICPA; 42 U.S.C. § 7384l(5) and (12)]. 

EEOICPA defines a DOE facility as “any building, structure, or premise, including the grounds upon 

which such building, structure, or premise is located ... in which operations are, or have been, 

conducted by, or on behalf of, the Department of Energy (except for buildings, structures, premises, 

grounds, or operations ... pertaining to the Naval Nuclear Propulsion Program)” [42 U.S.C. § 

7384l(12)]. Accordingly, except for the exclusion for the Naval Nuclear Propulsion Program noted 

above, any facility that performs or performed DOE operations of any nature whatsoever is a DOE 

facility encompassed by EEOICPA.

For employees of DOE or its contractors with cancer, the DOE facility definition only determines 

eligibility for a dose reconstruction, which is a prerequisite to a compensation decision (except for 

members of the Special Exposure Cohort). The compensation decision for cancer claimants is based 

on a section of the statute entitled “Exposure in the Performance of Duty.” That provision [42 U.S.C. § 

7384n(b)] says that an individual with cancer “shall be determined to have sustained that cancer in the 

performance of duty for purposes of the compensation program if, and only if, the cancer ... was at 

least as likely as not related to employment at the facility [where the employee worked], as 

determined in accordance with the POC [probability of causation1

As noted above, the statute includes a definition of a DOE facility that excludes “buildings, structures, 

premises, grounds, or operations covered by Executive Order No. 12344, dated February 1, 1982 

(42 U.S.C. 7158 note), pertaining to the Naval Nuclear Propulsion Program” [42 U.S.C. § 7384l(12)]. 

While this definition contains an exclusion with respect to the Naval Nuclear Propulsion Program, the 

section of EEOICPA that deals with the compensation decision for covered employees with cancer 

[i.e., 42 U.S.C. § 7384n(b), entitled “Exposure in the Performance of Duty”] does not contain such an 

exclusion. Therefore, the statute requires NIOSH to include all occupationally derived radiation 

exposures at covered facilities in its dose reconstructions for employees at DOE facilities, including 

radiation exposures related to the Naval Nuclear Propulsion Program. As a result, all internal and 

external dosimetry monitoring results are considered valid for use in dose reconstruction. No efforts 

are made to determine the eligibility of any fraction of total measured exposure for inclusion in dose 

reconstruction. NIOSH, however, does not consider the following exposures to be occupationally 

derived:

] guidelines established under 

subsection (c) ...” [42 U.S.C. § 7384n(b)]. Neither the statute nor the POC guidelines (nor the dose 

reconstruction regulation) define “performance of duty” for DOE employees with a covered cancer or 

restrict the “duty” to nuclear weapons work.

• Radiation from naturally occurring radon present in conventional structures

• Radiation from diagnostic X-rays received in the treatment of work-related injuries

 

1 The U.S. Department of Labor is ultimately responsible under the EEOICPA for determining the POC. 
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 7 of 22

3.1.2

The NIOSH Dose Reconstruction Project requires assessment of doses from medical X-rays that 

were required for screening and as a condition of employment. The Paducah Gaseous Diffusion 

Plant (PGDP) occupational medicine program required preemployment and periodic screening chest 

X-ray examinations. The examinations consisted of one posterior-anterior (PA) and one lateral (LAT) 

chest projection. In addition to parts of the body exposed in the primary beam of an X-ray machine, 

other tissues receive some dose from secondary radiation. Secondary radiation consists of X-rays 

that are scattered from surrounding materials or that escape from the source assembly. This TBD 

contains tables that list estimated dose equivalents that are favorable to claimants to organs of the 

body that result from single and combined PA and LAT chest X-rays for male and female PGDP 

employees. The tables are the result of an assessment of the air kerma at the source-to-skin distance 

(SSD), based on specific operating parameters for the facility insofar as these are known.

Scope

3.2 EXAMINATION FREQUENCIES

Each X-ray examination consisted of one PA and one LAT chest view. Table 3-1 lists the minimum 

criteria for examination frequencies for PGDP employees. This policy has been in place since before 

1974, with the exception of the criterion for asbestos workers, which started in about 1986. Some 

lumbar spine projections might have been made in the early days. These are addressed in 

Attachment A. 

Table 3-1. Frequency of chest X-ray 

examinations. 

Employees Frequency

Nonsmokersa Every 5 yr

Smokers under age 40 Every 5 yr

Smokers age 40 and 

older

Every 3 yr

Asbestos workersb Every 2 yr

a. Ex-smokers are considered smokers 

for 10 yr after quitting.

b. Program started about 1986.

Regular repeat/retake analyses for the X-ray department have been performed for a number of years. 

The actual repeat rate is not known. There is no indication that the repeat rate has been of any 

significance. There is no evidence that PGDP ever used fluoroscopy for required chest X-ray 

examinations.

3.3 EQUIPMENT AND TECHNIQUES

Table 3-2 lists the medical X-ray equipment used at PGDP during specified periods. A General 

Electric (GE) machine was used from the opening of the plant in 1952 through February 1975. It was 

replaced by a Picker unit, which served from March 1975 through December 1995. The present 

equipment has been in operation since January 1996. Quality assurance has been verified regularly 

by the Food and Drug Administration and the Commonwealth of Kentucky, as well as by in-house 

surveys. The same technician has operated the X-ray unit at PGDP from November 1974 to the 

present. Interviews with him and with a resident X-ray physicist (Gregory 2003) provided much of the 

information in this TBD. 
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 8 of 22

Table 3-2. PGDP X-ray equipment. 

Period Equipment

1952–Feb. 1975 GE, some filtration, manual collimator, stationary grid, no 

phototiming, hand-developed film

Mar. 1975–Dec. 

1995

Picker, filtration, automatic collimator, Bucky grid, DuPont 

cassettes and screen, phototiming, automatic film 

development 

Jan. 1996–present XMA Linear II Eureka, filtration, automatic collimator, 

Bucky grid, phototiming, automatic film development

The dose received from an X-ray exposure depends on a number of factors. These include filtration, 

collimation, use of grids, projection, and size and positioning of the subject. Machine settings 

determine the peak voltage (applied kilovoltage), current (milliamperes), and exposure time, which 

can be selected for optimum imaging with minimum dose. The two most recent machines (see 

Table 3-2) controlled exposures by phototiming. This permits accurate termination of the exposure 

when the film has received a predetermined amount of radiation for a properly exposed radiograph. 

Timing for the GE machine was determined by using standard charts and considering worker size. 

Table 3-3 lists nominal operating parameters for the three machines, all of which are single-phase, for 

PA and LAT projections. The GE equipment operated in the range from 70 to 90 kVp and the newer 

machines in the range from 90 to 100 kVp. All used a current of 300 mA. From March 1975 to the 

present, the dose with either of the two more recent machines has been comparable for a given 

procedure. Therefore, organ dose equivalents are determined for two periods: 1952 to February 1975 

and March 1975 to the present.

Table 3-3. Operating parameters. 

Period Projection kVp (V)

Current 

(mA)

1952–Feb. 1975 PA 70–90 300

LAT 70–90 300

Mar. 1975–Dec. 

1995

PA 90–100 300

LAT 90–100 300

Jan. 1996–present PA 90–100 300

LAT 90–100 300

Other factors being equal, the air kerma and resultant organ doses are proportional to the timeintegrated current (milliampere-seconds, or mAs). Some measurements of mAs were conducted with 

the present equipment for PA and LAT views of 16 males and 4 females with body sizes classified as 

“large,” “medium,” and “small.” Table 3-4 summarizes the results, listing average values of mAs in 

each classification and for all 20 persons in the sample. Although the number of subjects is small, 

both genders exhibit the trend toward larger mAs with increasing body size. Larger values for males 

are evident. The kerma estimation in Section 3.4 uses the average for the 10 medium male workers 

from Table 3-4 for all employees. Rounded off, these values for the PA and LAT views, respectively, 

are: 

QPA = 16 mAs and QLAT = 64 mAs (3-1)
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Table 3-4. Average mAs for exposures of workers of 

different body size. 

Body size

(number of males, 

females) View

Males

(mAs)

Females

(mAs)

Large

(3 males, 0 females)

PA 26.9 -

LAT 145 -

Medium

(10 males, 2 females) 

PA 15.9 14.3

LAT 64.4 47.5

Small

(3 males, 2 females)

PA 10.3 6.2

LAT 61.8 19.9

All persons

(16 males, 4 females)

PA 17.7 10.3

LAT 79 33.7

3.4 ORGAN DOSE CALCULATIONS

The calculation proceeds in two steps: determination of the air kerma at the entrance to the skin, and 

conversion of this quantity to dose equivalent in different organs. NCRP (1989, Table B.3, p. 99) lists 

values of the air kerma (more precisely, the air kerma in air) per mAs at different distances from the 

source (X-ray focal point) and for different kVp values with a total filtration equivalent to 2.5 mm Al. 

As stated in Section 3.3, doses for the two more recent PGDP X-ray machines are comparable. 

Section 3.4.1 determines the air kerma at skin entrance, applicable to both machines from March

1975 to the present, by using Table B.3 from NCRP (1989). Section 3.4.2 assesses the air kerma for 

the GE equipment, applicable from 1952 to March 1975, by other means. For both periods, this 

assessment used dose conversion factors from International Commission on Radiological Protection 

(ICRP) Publication 34 (ICRP 1983) in Sections 3.4.3 and 3.4.4 to evaluate the dose equivalent in 

various organs.

3.4.1

With an average tube potential of 95 kVp, consistent with Table 3-3, one obtains directly by linear 

interpolation from Table B.3 of NCRP (1989) (total filtration equivalent to 2.5 mm Al) the air kerma 

value Ko = 0.19 cGy/(100 mAs) for single-phase generators at a source-to-image distance (SID) 

ro = 183 cm (72 in.). It will be convenient to work with the following units:

Air Kerma for Exposures from March 1975 to Present

mAs

9.1 10 rad

cGy

1rad

100 mAs

.0 19cGy −3 × Ko = =× (3-2)

For an exposure made with Q mAs, the kerma at distance r is given by: 

),( rad

2

Q

r

r KrQK o

o 



 



 = (3-3) 

The square of the distance ratio adjusts for the inverse-square dependence of the kerma over the 

range of distances considered.

For the PA view, an allowance of 5 cm is made for cassette thickness and 26 cm for chest thickness 

between the source and image. Therefore, the SSD is rPA = 183 – 31 = 152 cm. For the LAT 

projection with an assumed chest thickness of 34 cm, rLAT = 183 – 39 = 144 cm. Thus:
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 10 of 22

rPA = 152 cm and rLAT = 144 cm (3-4)

With ro = 183 cm, one obtains from equations 3-2 and 3-3 the following values for the kerma at skin 

entrance for the two projections:

(16 mAs) 0.0 44 rad

152

183

mAs

9.1 10 rad 3 2

 = 

 



×  =

−

KPA (3-5)

and

(64 mAs) 2.0 rad

144

183

mAs

9.1 10 rad 3 2

 = 

 



×  =

−

KLAT (3-6)

These estimates of air kerma at skin entrance apply to exposures made from March 1975 to the 

present.

The kerma estimate (equation 3-5) for the PA view can be compared directly to measurements made 

during an in-house radiation safety survey of the PGDP X-ray facility in June 2003 (Gregory 2003). 

The exposure measured in the beam at a distance of 183 cm was 19 mR. The value of the kerma at 

this distance implied by equation 3-5 is 30 mrad, which is consistent with an exposure close to 30 mR, 

approximately 1.5 times larger than the measured value. Using NCRP (1989) with a total filtration of 

3.8 mm Al leads to the calculated kerma value of 0.019 rad at 183 cm. Thus, the estimate (equation 

3-5) is probably higher than the actual value by about 50% due to greater filtration than that assumed. 

However, as applied to PA views for all persons in this TBD, KPA = 0.044 rad, which is favorable to 

claimants, is used.

3.4.2

Detailed information and technical data for operation of the original X-ray installation at PGDP are 

limited. The latest revision of ORAUT (2005) contains default values for skin-entrance kerma for use 

in such instances. These take into account common practices of the day, limited filtration and 

collimation, low applied kilovoltage, slow film speeds, and worker dose studies reported in the 

literature. With conservative assumptions, the default values probably were approached only rarely in 

an actual exposure. This TBD uses the default kerma values of ORAUT (2005) for pre-1970 

conditions. They are listed in Table 3-5, together with the values given by equations 3-5 and 3-6. 

Air Kerma for Exposures from 1952 through February 1975

Table 3-5. Air kerma at skin entrance 

for PA and LAT views. 

Dates

Kerma (rad)

PA LAT

1952–Feb. 1975 0.20 0.50

Mar. 1975–present 0.044 0.20

3.4.3

Tables A2 through A9 in ICRP (1983) list average values of absorbed doses in seven selected organs 

and the total body per unit entrance kerma (i.e., air kerma in air with no backscatter). For example, 

the dose equivalent to the active bone marrow is computed for the values of the kerma in Table 3-5.

Dose Equivalents per Exposure for Organs Included in ICRP Publication 34

ICRP (1983, Table A8, p. 59) lists absorbed dose values for active bone marrow for different beam 

qualities, expressed as the half-value layer (HVL) in millimeters of aluminum. Values that are 
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 11 of 22

favorable to claimants, 2.5 mm Al for 1952 to February 1975 (ORAUT 2005) and 3.5 mm Al for March

1975 to the present, are assumed. With a quality factor of unity for X-rays, the values in the ICRP 

(1983) tables, listed in milligray (organ absorbed dose) per gray (entrance kerma), are numerically 

equal to millirem of organ dose equivalent per rad of entrance kerma. It follows, therefore, that 

multiplication of the kerma in rad from Table 3-5 by the values in the ICRP (1983) tables yields the 

organ dose equivalents H in millirem directly. In other words:

K rad)( × ICRP value = H mrem)( (3-7)

With an SID of 183 cm and the two assumed beam qualities, one obtains from Table A8 of ICRP 

(1983) the values needed to compute the organ dose equivalents for male and female PA and LAT 

chest projections. With the entrance kerma from Table 3-5, the following summarizes the dose 

equivalent to the active bone marrow for the four cases:

1952 to February 1975: 

PA: 0.20 × 92 = 18 mrem (males) LAT: 0.50 × 37 = 19 mrem (males)

0.20 × 86 = 17 mrem (females) 0.50 × 29 = 15 mrem (females)

March 1975 to present: 

PA: 0.044 × 146 = 6.4 mrem (males) LAT: 0.20 × 61 = 12 mrem (males)

0.044 × 141 = 6.2 mrem (females) 0.20 × 48 = 9.6 mrem (females)

For 1952 to February 1975, these dose equivalents agree with the values in ORAUT (2005). These 

are the first entries in Table 3-6. In principle, the rest of the table values are calculated in similar 

fashion. However, ICRP (1983) applies to collimated beams, and thus would probably underestimate 

doses to some organs for 1952 to February 1975. Some organs not in the chest cavity, such as the 

ovaries, testes, thyroid, and uterus, could be exposed to the primary beam if the collimation is poor. 

For 1952 to February 1975, the dose conversion factors of ORAUT (2005) for pre-1970 are used.

Table 3-6. Dose equivalent per PA and per LAT exposure for organs 

included in ICRP Publication 34. 

Organ

Dose equivalent (rem)a

1952–February 1975 March 1975–present

PA LAT PA LAT

Bone marrow 

(active)

1.8E-02 (m)

1.7E-02 (f)

1.9E-02 (m)

1.5E-02 (f)

6.4E-03 (m)

6.2E-03 (f)

1.2E-02 (m)

9.6E-03 (f)

Breast (female) 9.8E-03 1.3E-01 4.0E-03 6.3E-02

Lungs 8.4E-02 (m)

9.0E-02 (f)

9.7E-02 (m)

1.1E-01 (f)

2.5E-02 (m)

2.7E-02 (f)

5.5E-02 (m)

6.2E-02 (f)

Ovaries 2.5E-02 1.3E-02 1.4E-04 3.2E-04

Testes 5.0E-03 2.5E-03 4.0E-07 2.0E-05

Thyroid 3.5E-02 6.9E-02 2.7E-03 3.0E-02

Uterus (embryo) 2.5E-02 1.3E-02 1.3E-04 2.8E-04

a. (m) = male; (f) = female

3.4.4

For estimating dose equivalents with the Interactive RadioEpidemiological Program (IREP), other

organs are classified in three anatomical regions, as listed in the first column of Table 3-7. In the 

second column, a single organ from ICRP (1983) is selected from Table 3-6 as representative of the 

dose to all organs in that region. Column 3 of Table 3-7 lists other organs according to the region in 

Dose Equivalents per Exposure for Organs Not Included in ICRP Publication 34
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 12 of 22

Table 3-7. Dose equivalent per PA and per LAT exposure for organs not in ICRP 

Publication 34. 

Anatomical

region

ICRP 

34

organ Other organs

Dose equivalent (rem)

1952–Feb. 1975

March 1975–

present

PA LAT PA LAT

Thorax Lungs Bone surface

Esophagus

Liver/gall 

bladder/spleen

Remainder organs

Stomach

Thymus

9.0E-02 1.1E-01 2.7E-02 6.2E-02

Abdomen Ovaries Colon/rectum

Urinary/bladder

2.5E-02 1.3E-02 1.4E-04 3.2E-04

Head/neck Thyroid Eye/brain 6.4E-03 6.9E-02 2.7E-03 3.0E-02

Skin 2.7E-01 6.8E-01 6.2E-02 2.8E-01

which they are located. With the exception of skin in the last row, they are assigned the dose 

equivalent from Table 3-6 for the organ listed in column 2. For the lungs, the slightly larger values for 

females from Table 3-6 are used for both sexes. The ICRP “remainder organs” (ICRP 1991) are 

assigned to the group with the largest dose equivalent (thorax). 

The skin is the only organ listed in Table 3-7 that does not involve ICRP (1983) dose conversion 

factors. The estimated dose equivalent is numerically equal to the product of the entrance kerma 

(Table 3-5) and a backscatter factor based on Table B.8 of NCRP (1989). For the period 1952 to 

February 1975, the default pre-1970 skin doses from ORAUT (2005) are assigned in Table 3-7. The

values for March 1975 to present are obtained from Table 3-5 with a backscatter factor of 1.4 based 

on Table B-8 of NCRP (1989). 

3.4.5

The periodic X-ray examinations at PGDP consisted of one PA and one LAT exposure. Table 3-8 

lists the estimated resultant total organ dose equivalents per examination. With the exception of the 

skin (last row), these values are the sums of the respective dose equivalents from Tables 3-6 and 3-7. 

If two sets of values, (m) and (f), are listed in Table 3-6, the larger of the respective sums was entered 

in Table 3-8. For skin, two estimates were made for consideration in each period for Table 3-8 as 

follows: From March 1975 to the present, when both PA and LAT views were made, the posterior 

skin (Table 3-7) received a dose equivalent of 6.2 × 10-2 rem (with backscatter) from the PA view plus 

radiation from the LAT view (without backscatter). The latter component of the posterior skin dose 

equivalent is roughly approximated by the LAT lung dose equivalent, which from Table 3-7 is 

6.2 × 10-2 rem. This estimate gives a total dose equivalent of 6.2 × 10-2 + 6.2 × 10-2 = 1.2 × 10-1 rem

for the posterior skin when both views are made. 

Combined Dose Equivalents for PA and LAT Exposures

3.5 UNCERTAINTY

For 1952 to February 1975, the values listed in Tables 3-6 and 3-7 are based on assumptions 

favorable to claimants described by ORAUT (2005). For further conservatism, the authors suggest 

the use of a positive error of +30%.
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 13 of 22

Table 3-8. Organ dose equivalents for combined PA and 

LAT examinations. 

Organ

Dose equivalent (rem)

1952–Feb. 

1975

Mar. 1975–

present

Bone marrow 

(active)

3.7E-02 1.8E-02

Bone surface 2.0E-01 8.9E-02

Breast (female) 1.4E-01 6.7E-02

Colon/rectum 3.8E-02 4.6E-04

Esophagus 2.0E-01 8.9E-02

Eye/brain 7.5E-02 3.3E-02

Liver/gall bladder 2.0E-01 8.9E-02

Lungs 2.0E-01 8.9E-02

Ovaries 3.8E-02 4.6E-04

Remainder 2.0E-01 8.9E-02

Stomach 2.0E-01 8.9E-02

Testes 7.5E-03 2.0E-05

Thymus 2.0E-01 8.9E-02

Thyroid 1.0E-01 3.3E-02

Urinary/bladder 3.8E-02 4.6E-04

Uterus (embryo) 3.8E-02 4.1E-04

Skin (a) (a)

a. Summing the skin doses is not appropriate since different areas of 

skin are exposed for each of these projections

For March 1975 to the present, Table 3-9 lists sources of uncertainty in worker organ dose 

equivalents. The first column lists, from top to bottom, the sequential steps by which the values in 

Tables 3-6 and 3-7 were obtained. The second column characterizes the potential significance of 

these values in terms of uncertainties they might introduce. Knowledge of actual organ dose 

equivalents for a given procedure is uncertain because of physical factors and variations between

individuals.

As summarized in the first row of Table 3-9, organ dose equivalent estimations for the original PGDP 

X-ray machine (before March 1975) are upper limits, based on knowledge of machines and practices 

of the time. Much better characterization of the radiation field is known for the two later machines. In 

the second row, the physical data in NCRP (1989) have been shown to have little error. The 

assessment of 10% accuracy for worker dose (Zamenhof, Shahabi, and Morgan 1987) could reflect 

variations among workers.

With other conditions fixed, uncertainties in the peak voltage, tube current and exposure time, and 

placement of the individual in the X-ray beam contribute to uncertainty in the kerma at skin entrance 

(Table 3-9, third row). Based on NCRP (1989), the kerma was calculated from equation 3-3. By 

assigning values for uncertainties as coefficients of variation (ratio of the standard deviation and 

mean) for r, Q, and the tube potential, one can apply error-propagation formalism to estimate the 

resultant coefficient of variation for the kerma. Attachment B describes this procedure. For 

uncertainties of 10% in r and 5% in Q and the voltage, it is suggested that KPA = 0.044 ±0.015 rad at 

the 95% confidence level. The estimated uncertainty in the kerma values at skin entrance for March 

1975 to the present (last row in Table 3-5) is no more than 35%, attributable primarily to differences 

among workers and their placement.
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 14 of 22

Table 3-9. Potential sources of uncertainty in organ dose equivalent assessments. 

Source Assessment

Equipment and techniques, 

Section 3.3

GE machine (1952–February 1975): little documentation. Use 

conservative default values (ORAUT 2005).

Newer machines (March 1975–present): little uncertainty in 

knowledge of radiation field, verified by independent surveys. Use 

technique factors.

NCRP (1989), Section 3.4 Table B.3 of NCRP (1989) lists air kerma per mAs at different 

distances for various kVp and filtration from measurements of 

Zamenhof, Shahabi, and Morgan (1987), which states average 

accuracy of 0.3% for fit to measurements and 10% for worker-dose 

validation.

Air kerma K at skin entrance, 

equation 3-3, Table 3-5 

Ko determined by tube voltage and Q by current and time with 

relatively little error. Distance r from source to skin subject to 

considerable variation because of worker size and placement. 

Analysis (Attachment B) indicates net uncertainty in K due to these 

factors by perhaps as much as 35%.

ICRP (1983), Table 3-6 for 

ICRP 34 organs, Table 3-7 

for other organs

ICRP 34 tables for organ absorbed doses per unit entrance kerma 

are derived from Monte Carlo calculations for anthropomorphic 

phantom (Gorson, Lassen, and Rosenstein 1982). Additional 

uncertainties in actual organ dose equivalents introduced in this step 

include differences between mathematical model and actual organs

and individual anatomical variations among persons. Rough 

estimate of uncertainty, 50%.

In the last row of Table 3-9, the same conversion factors from entrance kerma to organ doses are 

used for all individuals, a distinction being made between male and female for some organs. In any 

case, the conversion factors are representative for an exposed individual (for the assumed kerma) to 

the extent that the anatomical features of the individual match those of the phantom, which are the 

basis for the tables. The variation introduced in this step is not known. An indication can be gained 

through comparison with dose conversion factors in ICRP (1983) for the 5-yr-old pediatric phantom 

under the same irradiation conditions. Doses in the smaller phantom per unit entrance kerma are 

often larger by factors approaching 2. Estimated uncertainty due to adult worker variability might be 

as large as 50%.

In summary, there is relatively little uncertainty associated with the first two steps in Table 3-9. The 

third and fourth steps entail, sequentially, estimated uncertainties of 35% and 50%. In the worst case, 

these would act fully in the same direction to increase the error. An exposure could then give a dose 

equivalent for some individuals that is larger than those listed in Tables 3-6 and 3-7 for March 1975 to 

the present by the factor 1(1.35)(1.50) = 2. Uncertainty in the values of the dose equivalent for this 

period in Table 3-8 is, conservatively, not more than a factor of 2. 

3.6 DOSE RECONSTRUCTION

3.6.1

The normal occupational chest X-ray examination at PGDP consisted of a single PA and a single LAT 

exposure. Table 3-10 lists estimates that are favorable to claimants, allowing for uncertainty, of organ 

dose equivalents per examination that dose reconstructors can use. The total dose equivalent to an 

organ of a worker is the product of the value in Table 3-10 and the number of examinations the worker 

underwent during each period, including a preemployment examination. Table 3-1 lists the minimum 

Organ Dose Equivalents Favorable to Claimants per Examination
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 15 of 22

frequency of chest X-ray examinations. Attachment A provides dose equivalents for lumbar spine 

examinations (possible in the early days).

The values in Table 3-10 for 1952 to February 1975 are 1.3 times the values in Table 3-8. They 

reflect the +30% error favorable to claimants assessed by ORAUT (2005), as stated in Section 3.5. 

Dose equivalents for March 1975 to the present are twice the estimated values in Table 3-8. This 

factor reflects the estimate of uncertainty favorable to claimants described in Section 3.5. 

Table 3-10. Organ dose equivalents favorable to claimants 

per examination consisting of one PA and one LAT 

exposure. 

Organ

Dose equivalent (rem)

1952–Feb. 

1975

Mar. 1975–

present

Bone marrow (active) 4.8E-02 3.6E-02

Bone surface 2.6E-01 1.8E-01

Breast (female) 1.8E-01 1.3E-01

Colon/rectum 4.9E-02 9.2E-04

Esophagus 2.6E-01 1.8E-01

Eye/brain 9.8E-02 6.6E-02

Liver/gall 

bladder/spleen

2.6E-01 1.8E-01

Lungs 2.6E-01 1.8E-01

Ovaries 4.9E-02 9.2E-04

Remainder 2.6E-01 1.8E-01

Stomach 2.6E-01 1.8E-01

Testes 9.8E-03 4.0E-05

Thymus 2.6E-01 1.8E-01

Thyroid 1.3E-01 6.6E-02

Urinary/bladder 4.9E-02 9.2E-04

Uterus 4.9E-02 8.2E-04

Skin (a) (a)

a. Summing the skin doses is not appropriate since different areas of skin 

are exposed for each of these projections

3.6.2

It is sometimes useful to establish initially if a given exposure history indicates that the levels warrant 

precise evaluation. Table 3-11 divides organs into groups. Each organ in a group has a dose 

equivalent that is no smaller than its value in Table 3-10. 

Optional Initial Screening

Therefore, dose reconstructors can use Table 3-11 to estimate an upper bound favorable to claimants 

for an organ dose equivalent per examination. Unless the records indicate more frequent X-rays, 

base the expected number of examinations on Table 3-1. Assume a preemployment examination 

followed by a regular examination every 3 yr thereafter, whether the worker was a smoker or not, until 

1986. Beginning at the start of 1986, assume that the examination frequency changes to every 2 yr to 

be favorable to claimants. 
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 16 of 22

Table 3-11. Upper-bound organ dose equivalents per examination for screening. 

Organ

Dose equivalent (rem)

1952–Feb. 

1975

Mar. 1975–

present

Colon/rectum, ovaries, testes, urinary/bladder, 

uterus 

4.9E-02 9.2E-04

Bone marrow (active), eye/brain, thyroid 1.3E-01 6.6E-02

Bone surface, breast (female), esophagus, 

liver/gall bladder/spleen, lungs, remainder, 

stomach, thymus

2.6E-01 1.8E-01

Skin 1.0E-00 6.2E1E-01

Example.

5 × (1.3 × 10-1) + 9 × (6.6 × 10-2) = 1.5 rem (3-8)

 Calculate an upper bound for the dose equivalent to the active bone marrow of a worker. 

The individual was hired on February 1, 1962, and worked steadily until retirement on March 31, 

1996. Determine the number of examinations during each of the two periods and apply Table 3-11. 

Without making a distinction for smoking, assume initially an examination every 3 yr around 

February 1. The length of employment was 34 yr and 2 months. Starting with the preemployment 

examination, there would be a total of five examinations with the older GE equipment (the 

preemployment examination plus those in 1965, 1968, 1971, and 1974). Examinations after February 

1974 were with the more recent equipment [four through 1986 (every 3 yr) and five from 1988 through 

1996 (every 2 yr) for a total of nine]. An upper bound for the dose equivalent to the active bone 

marrow, based on Table 3-11, is:
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 17 of 22

REFERENCES

Gorson, R. O., M. Lassen, and M. Rosenstein, 1982, “Patient Dosimetry in Diagnostic Radiology,” 

Handbook of Medical Physics, R. G. Waggener, editor, CRC Press, Boca Raton, Florida, 

June.

Gregory, W. D., 2003, "Report on Survey of Medical X-Ray Unit," memorandum to R. Moss, United 

States Enrichment Corporation, Paducah Gaseous Diffusion Plant, Paducah, Kentucky, 

June 20. [SRDB Ref ID: 12317] 

ICRP (International Commission on Radiological Protection), 1983, Protection of the Patient in 

Diagnostic Radiology, Publication 34, Pergamon Press, Oxford, England.

ICRP (International Commission on Radiological Protection), 1991, 1990 Recommendations of the 

International Commission on Radiological Protection, Publication 60, Pergamon Press, Oxford, 

England.

NCRP (National Council on Radiation Protection and Measurements), 1989, Medical X-Ray, Electron 

Beam and Gamma-Ray Protection for Energies up to 50 MeV (Equipment Design, 

Performance and Use), Report 102, Bethesda, Maryland.

ORAUT (Oak Ridge Associated Universities Team), 2005, Dose Reconstruction from Occupationally 

Related Diagnostic X-Ray Procedures, ORAUT-OTIB-0006, Rev. 03 PC-1, Oak Ridge, 

Tennessee, December 21.

Taylor, J. R., 1997, An Introduction to Error Analysis: The Study of Uncertainties in Physical 

Measurements, Second Edition, University Science Books, Sausalito, California.

Tsoulfanidis, N., 1983, Measurement and Detection of Radiation, McGraw-Hill Publishing, New York, 

New York.

Zamenhof, R. G., S. Shahabi, and H. T. Morgan, 1987, “An Improved Method for Estimating the 

Entrance Exposure in Diagnostic Radiographic Examinations,” American Journal of 

Roentgenology, volume 149, number 3, pp. 631–637.
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 18 of 22

GLOSSARY

absorbed dose

Energy absorbed per unit mass; units are rad and gray (Gy).

backscatter (radiation)

Radiation that is scattered backwards, enhancing skin dose where an X-ray beam normally 

enters the body.

dose equivalent

Product of absorbed dose and quality factor or radiation weighting factor. With dose in rad, 

unit is rem; with dose in Gy, unit is sievert (Sv).

gray (Gy)

Unit of absorbed dose (1 Gy = 1 J/kg = 100 rad).

kerma

Sum of initial kinetic energies of all charged particles (including Auger electrons) liberated by 

uncharged radiation per unit mass. Units are rad and Gy.

primary X-rays

X-rays that constitute the useful beam that emerges from the tube target.

rad

Unit of absorbed dose (1 rad = 100 erg/g = 0.01 Gy).

rem

Unit of dose equivalent.

secondary radiation

As distinct from primary X radiation, secondary radiation consists of X-rays that have been 

scattered from objects or that leak from the source assembly.

sievert (Sv)

Unit of dose equivalent.

X-ray

Ionizing electromagnetic radiation of non-nuclear origin; also, a radiograph.
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 19 of 22

ATTACHMENT A 

ORGAN DOSE EQUIVALENTS FOR LUMBAR SPINE EXAMINATIONS

Page 1 of 2

Lumbar spine examinations might have occurred in the early days at PGDP, certainly before 1974, 

when the present X-ray technician was hired. They could have been a preemployment requirement, a 

practice in some industries at the time.

There is no specific information available for dose reconstruction other than that listed in Tables 3-2 

and 3-3 for the original GE machine. It is assumed that an examination consisted at most of five 

exposures: one anterior-posterior (AP), one LAT, two oblique, and one spot film. Operating voltage 

and current are assumed to be 90 kVp and 300 mA, respectively, with exposure times of 1 s for AP 

and 1.5 s for LAT, respectively. Under these conditions, organ dose equivalents can be calculated for 

the two views by the method used in this TBD. ICRP (1983) does not include the other three. In the 

absence of other information, initial organ dose equivalents HLS to be used for lumbar spine dose 

reconstruction are estimated to be those from all five views, roughly approximated as 2.5 times the 

sum of the AP and LAT dose equivalents, unless otherwise noted. Table A-1 lists values of HLS. 

Table A-1. Organ dose equivalents for lumbar spine 

examinations. 

Organ

Dose equivalent (rem)

HAP HLAT HLS

Bone marrow (active) 1.3E-01 1.4E-01 6.8E-01

Bone surface 2.7E-01 9.1E-02 9.0E-01

Breast (female) 2.7E-01 9.1E-02 9.0E-01

Colon/rectum 7.3E-01 3.1E-01 2.6E-00

Esophagus 2.7E-01 9.1E-02 9.0E-01

Eye/brain 1.0E-03 6.5E-05 3.4E01a 

Liver/gall 

bladder/spleen

2.7E-01 9.1E-02 9.0E-01

Lungs 2.7E-01 9.1E-02 9.0E-01

Ovaries 7.3E-01 3.1E-01 2.6E-00

Remainder 2.7E-01 9.1E-02 9.0E-01

Stomach 2.7E-01 9.1E-02 9.0E-01

Testesb 6.1E-02 2.1E-02 2.1E-01

Thymus 2.7E-01 9.1E-02 9.0E-01

Thyroid 1.0E-03 6.5E-05 4.5E01a 

Urinary/bladder 7.3E-01 3.1E-01 2.6E-00

Uterus 9.8E-01 2.0E-01 3.0E-00 a. Based on thymus dose equivalent. 

b. Used DCF for the abdomen. 

The calculation proceeds as in the main document. Analogous to equation 3-1, one has for the 

lumbar spine examination

QAP = (300 mA)(1 s) = 300 mAs and QLAT = (300 mA)(1.5 s) = 450 mAs (A-1)
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 20 of 22

ATTACHMENT A 

ORGAN DOSE EQUIVALENTS FOR LUMBAR SPINE EXAMINATIONS

Page 2 of 2

As before, a 5-cm thickness is allowed for the cassette. Body thicknesses of 26 and 34 cm are 

assumed for the AP and LAT views, respectively. The lumbar spine SID = 102 cm (ICRP 1983). 

Therefore, for the SSD:

rAP =−= 7131102 cm and rLAT =−= 6339102 cm (A-2)

From Table B.3 in (NCRP 1989), one finds for the kerma at the distance ro = 60 cm:

mAs

.0 016 rad

cGy

1rad

100 mAs

cGy6.1 o 1- K = =× (A-3)

The kerma values at skin entrance for the two views are:

(300 mAs) 3.4 rad

71

60

mAs

.0 016 rad 2

 = 

 



 KAP = (A-4)

and

(450 mAs) 6.5 rad

63

60

mAs

.0 016 rad 2

 = 

 



 KLAT = (A-5)

The procedures used for calculating organ dose equivalents in Tables 3-6 and 3-7 were applied to the 

lumbar spine AP and LAT views for the GE machine in use from 1952 to February 1975. As in 

ORAUT (2005), a beam quality HVL of 2.5 mm Al was assumed, and substitute projections were used 

for some organs to approximate the lack of good collimation. The estimated total dose equivalents 

HLS for the thyroid and eye/brain were assumed to be in the same ratios to the thymus as in Table 3-8. 

The dose equivalents for the breast were approximated by those for the lung. Table A-1 lists the 

resulting estimates of organ dose equivalents HAP and HLAT calculated for the two lumbar spine views. 

The last column lists estimated organ dose equivalents for the five assumed exposures, approximated 

by:

(5.2 ) HLS = AP + HH LAT (A-6)

These values for HLS can be used as rough first approximations for lumbar spine dose reconstruction 

in the absence of other information.
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 21 of 22

ATTACHMENT B 

ERROR PROPAGATION FOR KERMA

Page 1 of 2

The kerma at skin entrance distance for the two newer machines used from March 1975 to the 

present (Table 3-5) is calculated from equation 3-3. Given values for uncertainties in r, Q, and the 

tube potential, a standard formalism for error propagation (Taylor 1997; Tsoulfanidis 1983) can be 

applied to estimate the uncertainty in K that results. Because the beam intensity is approximately 

proportional to the 1.7 power of the tube potential V, one can make the replacement:

7.1 = oo VCK (B-1)

where Co is the constant of proportionality in equation 3-3. To show the explicit dependence of the 

kerma on these quantities, one can then write in place of equation 3-3: 

Q

r

r oVCQrVK

2

7.1 o ),,( 



 



 = (B-2)

For the analysis, it is convenient to employ uniform notation for the variables, defined by writing: 

V = X1 with mean μ1 = μV and standard deviation σ1 = σV

r = X2 with mean μ2 = μr and standard deviation σ2 = σr

Q = X3 with mean μ3 = μQ and standard deviation σ3 = σQ

The kerma can be written: 

2

7.1

2 ),,(

2

31

oo321 X

X X = rCXXXK (B-3)

Given estimated uncertainties σi in the Xi

, the task is to estimate the resulting uncertainty σK in K. 

According to the formalism, one approximates the kerma (equation B-3) by making a Taylor series 

expansion about the point μ = (μ1, μ2, μ3) and retaining only the linear terms. The variables are 

assumed to be independent. It follows that: 

2

2

μ

3

1

2

i

i i

K σ

X

K

σ ∑

= 















∂

∂

≅ (B-4)
Document No. ORAUT-TKBS-0019-3 Revision No. 01 Effective Date: 09/26/2006 Page 22 of 22

ATTACHMENT B 

ERROR PROPAGATION FOR KERMA

Page 2 of 2

The partial derivatives are to be evaluated at the point μ. Carrying out the differentiations from 

equation B-3 and substituting into equation B-4 gives:

( ) 































+ 













 − + 















≅ 2

2

2

7.1

2

2

3

3

7.1

2

2

2

0.7 2 2 2 7.1 2

3

2

1

2

2

1

1

2

31

ooK σ

μ

μ σ

μ

μμ σ

μ

μμ σ rC (B-5)

































+ 















+ 































≅

2 2 2 2

2

7.1

2 .2 89 4

3

3

2

2

1

1

2

31

oo μ

σ

μ

σ

μ

σ

μ

μμ rC

Comparison of the factor outside the bracket with equations B-2 and B-3 shows that it is the square of 

the kerma K(μ) at point μ. Returning to the original notation with Ko, r, and Q, one can write in place of 

the last equation: 

2

1

2 2 2

.2 89 4

)( 































+ 















+ 















≅

Q

Q

r

r

V

K V

μ

σ

μ

σ

μ

σ

K μ

σ (B-6)

The ratio of the standard deviation (standard error) and the mean is called the coefficient of variation, 

which for the kerma can be denoted by cK = σK ÷ μK. With similar notation for the coefficients of 

variation for the other variables, equation B-6 can be written: 

222

K .2 89 4 QrV c ≅ ++ ccc (B-7)

This result provides an estimate of the uncertainty of the kerma in terms of the uncertainties in V, r, 

and Q. The approximation is best to the extent that the σi << μi. 

Values of the operating parameters used to obtain KPA = 0.044 rad, equation 3-5, can be used as 

estimates for the quantities needed in equation B-7. For orientation, it will be assumed that the 

voltage V and mAs Q have standard errors of ±5%. An uncertainty in the SSD r of 10 cm, or ±7% with 

r = 152 cm, will be assumed to allow for anatomical and placement variations. With cV = cQ = 0.05 

and cr = 0.07, equation B-7 gives cK ≅ 0.17. Thus, the estimated standard error of the PA kerma is 

0.17 × 0.044 = 0.007 rad. With assumed normal statistics, KPA = 0.044 ±0.015 rad at the 95% 

confidence level (1.96σ). That is to say, the probability is 0.95 that the true value of the kerma (which 

is unknown) is in the stated range. The interval width is ±34%. With other reasonable assumptions, it 

appears that the largest contributor to uncertainty in row 3 of Table 3-9 rises from variations in the 

SSD. Use of Tables 3-6 and 3-7 implies that r = 152 cm for all persons. The uncertainty in the kerma 

at skin entrance is assumed to be no greater than about 35%.