ORAU Team

NIOSH Dose Reconstruction Project

Technical Basis Document for the K-25 Site - 

Occupational Medical Dose

Document Number:

ORAUT-TKBS-0009-3 

Effective Date: 06/29/2004

Revision No.: 00

Controlled Copy No.: ________

Page 1 of 12

Subject Expert: James E. Turner

Document Owner

Approval: Signature on File Date: 06/21/2004

Jay J. Maisler, TBD Leader

Approval: Signature on File Date: 06/29/2004 Judson L. Kenoyer, Task 3 Manager

Concurrence: Signature on File Date: 06/28/2004

Richard E. Toohey, Project Director

Approval: Signature on File Date: 06/29/2004

James W. Neton, OCAS Health Science Administrator

Supersedes:

None

TABLE OF CONTENTS

Record of Issue/Revisions ...................................................................................................................2

Acronyms and Abbreviations ...............................................................................................................3

3.0 Occupational Medical Dose ........................................................................................................4

3.1 Examination Frequencies...................................................................................................4

3.2 Equipment and Techniques................................................................................................4

3.3 Organ Dose Calculations....................................................................................................5

3.4 Uncertainty Analysis for K-25 Radiography Doses ............................................................. 6

3.5 Dose Reconstruction..........................................................................................................7

References ..........................................................................................................................................8

Glossary ............................................................................................................................................11

LIST OF TABLES

3.1-1 Frequency of occupational chest X-rays at K-25 ...................................................................... 9

3.2-1 X-ray equipment used at K-25..................................................................................................9

3.3-1 Organ dosesa per X-ray procedure for the various X-ray examinations from 

1945-2000..............................................................................................................................10

3.3-1 Reference organs for IREP organs not included in ICRP 34 .................................................. 10
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RECORD OF ISSUE/REVISIONS 

 

ISSUE 

AUTHORIZATION 

DATE

EFFECTIVE 

DATE

REV. 

NO. DESCRIPTION

Draft 02/05/2004 00-A New technical basis document for the Oak Ridge 

Gaseous Diffusion (K-25) plant – Occupational 

Medical Dose. Initiated by Joe Alvarez.

Draft 04/26/2004 00-B Incorporates internal review comments. Initiated 

by Jay J. Maisler.

Draft 05/20/2004 00-C Incorporates NIOSH and internal review 

comments. Initiated by Jay J. Maisler.

Draft 06/11/2004 00-D Incorporates additional NIOSH and internal review 

comments. Initiated by Jay J. Maisler.

06/29/2004 06/29/2004 00 First approved issue. Initiated by Jay J. Maisler.
Effective Date: 06/29/2004 Revision No. 00 Document No. ORAUT-TKBS-0009-3 Page 3 of 12

ACRONYMS AND ABBREVIATIONS

cm centimeter

DOE U.S. Department of Energy

GE General Electric

HVL half-value layer

IREP Interactive RadioEpidemiological Program

kVp kilovolt peak

LAT lateral

mA milliampere

mAs milliampere-second

mm millimeter

PA posterior-anterior

RMS root mean square

SID source-to-image distance

SSD source-to-skin distance
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3.0

Technical Basis Documents (TBDs) and Site Profile Documents 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 about the 

affected site(s). These documents may be used to assist the National Institute for Occupational 

Safety and Health in the completion of the individual work required for each dose reconstruction.

OCCUPATIONAL MEDICAL DOSE

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 Employee 

Occupational Illness Compensation Program Act of 2000 (42 U.S.C. § 73841 (5) and (12).

The K-25 occupational health and safety program required preemployment, annual physical, and 

health monitoring examinations. These examinations typically included diagnostic chest X-rays. The 

doses from these procedures depended on the characteristics of the X-ray machine and the 

procedure used.

3.1 EXAMINATION FREQUENCIES

During the early years at K-25, when little was known about health effects of working with uranium, Xray examinations were frequent in an effort to monitor worker health. Table 3.1-1 lists the nominal 

frequency of examinations over the years during which work-related X-rays were required. Some 

workers might have received occupational X-rays on a schedule different from that listed in Table 3.1-

1. The reconstruction of occupational dose should include all occupational X-rays according to the 

frequency listed in Table 3.1-1 unless the individual-specific frequency is known and is more frequent 

than that in Table 3.1-1. (Since chest X-rays were no longer required for non-radiation workers after 

1959, this procedure is claimant favorable.)

3.2 EQUIPMENT AND TECHNIQUES

The earliest X-rays at K-25 used the photofluorographic technique. Photofluorography had 

widespread use throughout the United States for tuberculosis screening in the 1930s and was stateof-the-art medical technology when work began at the gaseous diffusion plant as part of the 

Manhattan Project. The photofluorography technique was phased out in favor of the current 

conventional X-ray exam.

Two X-ray machines were used at K-25 during the 1940s and 1950s: (1) a General Electric (GE) 

Model KX-10 Photoroentgen X-ray machine, used primarily for photofluorography of the chest, and (2) 

a Westinghouse 200-mA X-ray machine, used with an adjustable table and fluoroscopic attachment to 

examine extremities, spine, hips, skull, shoulder, and other nonthoracic locations. The Westinghouse 

machine, which produced the now-conventional 14-in. x 17-in. chest X-ray, was primarily a backup to 

the GE machine (Cardarelli 2000). The GE machine was used with a lyselia grid to produce miniature 

4-in. x 5-in. stereoscopic posterior–anterior (PA) chest X-rays (Cardarelli 2000). The stereoscopic 

technique produces two images of the chest (on 4-in. x 10in. film) at slightly different angles, resulting 

in a three-dimensional image of the chest when viewed through a stereoscope (Mason 1944; Hemphill 

and Diercks 1945).

Different techniques were used to produce PA chest X-rays with the Westinghouse and GE machines 

(Cardarelli, 2002). The Westinghouse X-ray beam passes through the chest and directly exposes the 

film to produce an image of the chest (Quinn 1945). The GE photofluorographic X-ray beam passes 
Effective Date: 06/29/2004 Revision No. 00 Document No. ORAUT-TKBS-0009-3 Page 5 of 12

through the chest and produces an image on a fluorescent screen. The fluorescent image is 

photographed in two views for the stereoscopic image (Verstandig and Ainsworth 1944). The 

photofluorographic technique delivered a higher radiation dose to the subject because more exposure 

time was required to produce a photograph from the dim fluorescent image. Improvement in film and 

film processing enabled the phasing out of the photofluorographic technique in favor of 

film/intensifying screen imaging. 

The K-25 site used only the conventional PA chest X-ray technique for routine examinations after the 

early 1950s, which substantially reduced radiation doses per examination. In 1962, a Westinghouse 

300-mA machine replaced the 200-mA machine. Additional X-ray exposure was introduced in the 

early 1970s when the health monitoring program added a lateral (LAT) chest view to the routine chest 

X-ray examination procedure (Cardarelli 2000). In 1987, a Westinghouse 500-mA X-ray unit replaced 

the 300-mA machine. Routine PA and LAT chest views were performed through 2000.

This document assumes that K-25 medical practices followed the standards of radiology practice 

during the 1930s and 1940s. Nevertheless, workers might have received their largest occupational 

doses from the required medical X-ray examinations. The amount of dose received depends on the 

type of equipment, the technique factors, and the number of examinations typical in the early years 

(Cardarelli 2002). K-25 medical records include notations in individual worker files regarding the date 

and the purpose of the of X-ray examinations.

The occupational medical program at K-25 from 1945 to 2000 used three diagnostic radiographic 

procedures in connection with preemployment, health monitoring, or postemployment medical 

examinations:

1. 4-in. × 5-in. PA photofluorographic film

2. Posterior-anterior 14-in. × 17-in. chest film 

3. Lateral chest film 

Doses from these three techniques were evaluated for assigning occupational dose. Other 

radiographic examinations of K-25 employees that might have occurred were nonoccupational in the 

sense that they were necessitated by illness or injury and were not part of the employee physical 

examination process.

Table 3.2-1 lists the X-ray equipment used at K-25 and the entrance skin exposure (ESE) produced 

by the machines (Cardarelli 2002). The ESEs in Table 3.2-1 are all from actual measurements made 

and documented in the literature.

3.3 ORGAN DOSE CALCULATIONS

Estimated organ doses for PA and LAT chest X-rays were based on the dose conversion factors in 

ICRP (1982). Organ doses from LAT chest radiography were greater than those from the 

corresponding PA doses based on the greater mAs exposure per radiograph and the smaller SSD. 

ICRP (1982) provides tables of average absorbed dose (mGy) in selected organs for selected X-ray 

projections at 1 Gy entrance kerma (i.e., air kerma without backscatter) for selected views and 

selected beam qualities [i.e., various half-value layers (HVLs)]. These tables list the basic dose 

conversion factors for converting air kerma to organ dose. Air kerma was obtained from Table 3.2-1 

for machine, view, and period by assuming R = cGy (kerma). This assumption is conservative. The 
Effective Date: 06/29/2004 Revision No. 00 Document No. ORAUT-TKBS-0009-3 Page 6 of 12

estimation is made by equation 3-1, where ESE is the entrance skin exposure in R = cGy = rem, DCF

is the dose conversion factor in mGy/G = millirem/rem, and D is dose in millirem.

ESE DCF =× D (3-1)

Table 3.3-1 lists the results of equation 3-1 for the organs listed in ICRP (1982). The results of Table 

3.3-1 assume poor collimation prior to 1970, which means that some organs are included in the 

primary beam that would not normally be had the beam been properly collimated.

The Interactive RadioEpidemiological Program (IREP) code specifies organs for which there are no 

ICRP (1982) dose conversion factors. Organs not listed in Table 3.3-1 can be assigned doses by 

analogy of anatomical location – thorax, abdomen, and head/neck. The ICRP (1982) reference 

organs in these locations are lung, ovaries, and thyroid, respectively, as listed in Table 3.3-2. The 

dose for the analogous organ in Table 3.3-2 is assumed to be equal to that for the reference organ 

listed in Table 3.3-1 for the type of X-ray examination. Such a dose assignment will be conservative 

because the analog organ is more distant or more shielded than the reference organ. 

3.4 UNCERTAINTY ANALYSIS FOR K-25 RADIOGRAPHY DOSES

Error (deviation from the correct, true, or conventionally accepted value of a quantity) and uncertainty 

(defined in terms of the potential range of a stated, measured, assumed, or otherwise determined 

value of a quantity) provide an indication of the confidence of the dose estimates. Error implies 

knowledge of the correct or actual value, which is, of course, not known. Therefore, the more 

appropriate factor is uncertainty, which is expressed in terms of a confidence level (e.g., 99% -- that 

the correct or true value, although not actually known, has a 99% probability of falling within the range 

cited) and includes both precision or reproducibility of the measurement and accuracy, or how close 

the measurement or estimate of dose comes to the actual or correct value.

A large number of factors affect X-ray machine output intensity and, as a consequence, introduce 

uncertainty in the dose to the worker. Five factors produce the dominant dose uncertainty:

1. Variation in applied kilovoltage

2. Variation in beam current

3. Variation in exposure time

4. Distance from the worker to the source of the X-rays (SSD)

The influence of such other factors as the use of screens, grids, reciprocity failure, film speed, and 

development, while potentially variable, does not appreciably affect the beam output intensity.

X-ray output should be constant and unvarying for a given set of machine settings and parameters. 

This is not true in practice, although output is essentially constant unless focal spot loading occurs, 

which could be the case if the power rating of the machine is exceeded. It is unlikely that power 

ratings were ever exceeded, because such an event would be difficult to achieve and could result in 

damage to the X-ray tube. Nevertheless, even with the use of so-called constant voltage transformers 

to control line voltages, slight variations might occur in line voltage input or other internal voltages, 

which in turn could alter the kVp of the output beam. In general, for a given setting, variation in kVp 

falls within + 5% of the machine setting (Seibert et al. 1991). Beam intensity is approximately 

proportional to the 1.7 power of the kilovoltage (Trout, Kelley, and Cathey 1952; Taylor 1957); this 

translates to an uncertainty of approximately ± 8.6% with respect to output beam intensity in the 80 to 

100 kVp used for diagnostic radiographs at K-25. For conservatism, this is rounded up to ±9%.
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Similar slight variations in tube current are normal; as a tube ages, or heats up from use, current can 

change and typically will drop. With all other factors constant, beam intensity will be reduced in direct 

proportion to the change in tube current. Typically, the reduction in beam output from current 

variation is not more than a few percent under normal operating conditions; large decreases are 

readily detectable and result in maintenance on the machine to restore the output or, as a temporary 

measure, an increase in the current or kVp to provide the necessary intensity for proper radiography. 

For a given kVp setting, the output of the beam is a function of the tube current, which in turn is 

measured by a milliammeter, which measures average tube current. The measurement is subject to 

uncertainties; there might be minor changes in output as the tube heats from normal use. Because 

these variations are typically small, the estimated uncertainty in beam output attributable to current 

variation is ± 5%.

Another parameter with the potential to affect the dose from a diagnostic radiograph, perhaps 

significantly, relates to the time of exposure. A full wave rectified machine produces 120 pulses of Xrays per second. In an exposure time of 1/20 of a second, six pulses would result. A small error in 

the timer that resulted in a change of only + 1 pulse would correspondingly affect the output by ± 17%; 

for an exposure time of 1/30 of a second, the change in output corresponding to a deviation of + 1 

pulse is + 25%. Early mechanical timers were notoriously inaccurate. Accuracy improved 

significantly with the introduction of electronic timers. The assumed uncertainty in beam output 

attributable to timers has an upper limit of ± 25%.

The final factor likely to affect worker dose relates to distance from the source of the X-rays, which is 

a determinant of the entrance skin exposure. For a given individual, the SSD will be determined 

largely by the body thickness of the worker and the accuracy of the positioning. For a typical worker, 

the estimated variation in SSD is no more than a few centimeters, with an upper limit of perhaps 7.5 

cm. Using the inverse square, this indicates an uncertainty of ± 10% from this source.

The machine settings and parameters introduce random uncertainties and the total uncertainty is the 

root mean square (RMS) value. The RMS value is simply the square root of the sum of the squares, 

and computes as ± 28.9%. Rounding this up to ± 30% provides an adequate and suitably 

conservative estimation of uncertainty. Thus, for an individual ESE or derived organ dose, an 

uncertainty of ± 30% at a confidence interval of one standard deviation can be assumed. For further 

conservatism it might be appropriate to assume that errors are all positive, and only + 30% should be 

used.

3.5 DOSE RECONSTRUCTION

Worker X-ray examinations were recorded in individual medical histories. As described in Section 

3.1, dose should be assigned based on recorded history rather than the frequencies listed in Table 

3.1-1 when to recorded history is known and is more frequent than the data listed in Table 3.1-1. 

Otherwise, dose reconstruction should proceed on the basis of the nominal frequency listed in Table 

3.1-1. The type of X-ray machine was probably recorded, so organ dose can be extracted directly 

from Table 3.3-1. For 1945 to 1956, when both the GE KX-10 and the Westinghouse 200-mA were 

used, Cardarelli (2002) estimates that the GE KX-10 was used for 86% of the examinations. Workers 

with lost records should be assigned the most appropriate frequency based on type of employment. 

The assigned dose using Tables 3.3-1and 3.3-2 and the number of examinations is a point estimate. 

Uncertainty should be applied as a normal distribution with an uncertainty of 30%.
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REFERENCES

Cardarelli J J, 2000, A Potential Consequence of Excluding Workrelated X-Ray Exposures When 

Computing Cumulative Occupational Radiation Dose at a Uranium Enrichment Plant, 

Dissertation, University of Cincinnati, Cincinnati, Ohio.

Cardarelli, J., H. Spitz, C. Rice, R. Buncher, H. Elson, and P. Succop, 2002, “Significance of radiation 

exposure from work-related chest X-rays for epidemiological studies of radiation workers,” 

American Journal of Industrial Medicine 42:490–501.

Hemphill, S. P., and M. W. Diercks, 1945, “Simple method for taking stereoscopic chest films,” U.S. 

Nav M Bull 44:166–169.

ICRP (International Commission on Radiological Protection), 1982, “Protection of the Worker in 

Diagnostic Radiology,” Annals of the ICRP, ICRP Publication 34, 9(2/3):1-82.

Gupton, E.D., T. Tuck, and T.A. Lincoln, 1956, “Exposure Data Diagnostic Radiography,” Report to 

file, 9/26/56, Oak Ridge National Laboratory, Oak Ridge, Tennessee.

Lincoln, T. A. and Gupton, E. D. 1957. Radiation Doses in Diagnostic X-ray Procedures”. Radiology 

71:208-215.

Mason, M. W., 1944, “Photofluorography for chest surveys,” Radiology 43: 499–503.

Quinn, B., 1945, “Mass miniature radiography of the chest using 4x5 in film,” Radiography XI 

(125):33–37.

Seibert, J. A., G. T. Barnes, and R. G. Gould, 1991, Specification, Acceptance Testing, and Quality 

Control of Diagnostic X-ray Imaging Equipment, Medical Physics Monograph No. 20, 

American Institute of Physics, New York.

Verstandig, C. C, and C. W. Ainsworth, 1944, “Photoroentgenographic technique and dark room 

procedure used at the army recruiting and induction station, New Haven, Connecticut,” Am J 

Roentgenol 52:547– 550.

Taylor, L. S, 1957, “Practical Suggestions for Reducing Radiation Exposure in Diagnostic 

Examinations,” Amer. J. Roentgenology. Radium Ther. Nucl Med. 78:983-987.

Trout, E. D., J. P. Kelley, and G. A. Cathey, 1952, “Use of Filters to Control Radiation Exposure to 

Worker in Diagnostic Roentgenology,” Amer. J. Roentgenol. Rad. Ther. Nucl. Med. 67:962- 

963.
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 Table 3.1-1. Frequency of occupational chest X-rays at K-25. 

Period Frequency Comment

1944 – 1945 Annual a All employees

1946 - 1959 Annual b All employees

1960 – 1979 Annual All radiation workers.

1980 - 2002 Every 5th year All radiation workers

a Some workers monthly, with potential for exposure to uranium dust.

b Some workers every few months, with potential for exposure to uranium dust.

Table 3.2-1. X-ray equipment used at K-25 (Cardarelli 2002). 

Entrance Skin 

Exposure (cGy)

Period X-ray 

machine

kVp

(kV)

Assumed 

HVL (mm 

Al eq)

Image 

size 

(inches)

PA LAT

1944-1956 GE KX-10 80 2.5 4 x 5 2.488a

1944-1962 Westinghouse 

200-mA 65 2.5 14 x 17 0.055b 

1962-1969 Westinghouse 

300-mA 90 2.5 14 x 17 0.015c 

1970-1986 Westinghouse 

300-mA 150 4 14 x 17 0.010d 0.030d 

1987-2000 Westinghouse 

500-mA 150 4 14 x 17 0.022d 0.035d 

a. Quinn, 1945; Cardarelli, 2000.

b. Lincoln and Gupton 1957.

c. Gupton et al., 1956 on comparable unit.

d. Cardarelli, 2000, conservatively assumed 150 kVp and 4 mm Al HVL.
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Table 3.3-1. Organ dosea per X-ray procedure for the various X-ray examinations from 1944-2000. 

Organ View

1944-1956

GE Model KX-10

Photofluorographic

4" x 5"

2.5 mm Al

Dose

(rem)

1944-1961

Westinghouse 

200-mA

X-ray

14" x 17"

Dose

(rem)

1962-1969

Westinghouse 

300-mA

X-ray

14" x 17"

Dose

(rem)

1970-1986

Westinghouse 

300-mA

X-ray

14" x 17"

Dose

(rem)

1987-2000

Westinghouse 

500-mA

X-ray

14" x 17"

Dose

(rem)

Thyroid PA 4.33E-01b 9.57E-03 b 2.61E-03 b 7.80E-04 1.72E-03

LAT 4.92E-03 5.74E-03

Eye/Brain PA 7.96E-02c 1.76E-03c 4.80E-04c 7.80E-04 1.72E-03

LAT 4.92E-03 5.74E-03

Ovaries PA 2.07E-02 6.88E-03 2.52E-03 5.20E-05 1.14E-04

LAT 7.50E-05 8.75E-05

Testes PA 4.15E-03 1.38E-03 1.37E-04 1.00E-07 2.20E-07

LAT 3.00E-06 3.50E-06

Lungs (male) PA 1.04E+00 2.30E-02 6.29E-03 6.28E-03 1.38E-02

LAT 9.39E-03 1.10E-02

Lungs (female) PA 1.12E+00 2.48E-02 6.77E-03 6.74E-03 1.48E-02

LAT 1.05E-02 1.23E-02

Breast PA 1.22E-01 2.70E-03 7.35E-04 1.16E-03 2.55E-03

LAT 1.03E-02 1.20E-02

Uterus PA 3.23E-03 8.20E-03 2.24E-03 5.20E-05 1.14E-04

LAT 6.30E-05 7.35E-05

Bone marrow (male) PA 2.29E-01 5.06E-03 1.38E-03 1.78E-03 3.92E-03

LAT 2.28E-03 2.66E-03

Bone marrow (female) PA 2.14E-01 4.73E-03 1.29E-03 1.72E-03 3.78E-03

LAT 1.77E-03 2.07E-03

Skin PA 3.36E+00d 7.42E-02 d 2.03E-02 d 1.40E-02e 3.08E-02e

LAT 4.20E-02e 4.90E-02e

a Dose conversion Factors from Tables A.2 through A.9, ICRP Publication 34 (1982). b. Dose conversion factor for AP C-spine multiplied by depth dose correction factor of 0.20. c. Dose conversion factor for PA chest. d. Entrance kerma multiplied by a backscatter factor of 1.35. e. Entrance kerma multiplied by a backscatter factor of 1.40.

Table 3.3-2. Reference organs for IREP organs not included in ICRP 34. 

Anatomical location ICRP 34 reference organ IREP organ analogues

Thorax Lung Thymus, esophagus, stomach, bone surface, liver/

gall bladder/spleen, remainder organs

Abdomen Ovaries Urinary/bladder, colon/rectum

Head and neck Thyroid (unless otherwise 

specified)

Eye, brain
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GLOSSARY

backscatter 

A reflection x-rays from a nonreflective surface. The x-rays are scattered in all 

directions, including back in the direction from which it came.

dose

The amount of radiation energy deposited in a unit mass of tissue.

error

Deviation from the correct, true, or conventionally accepted value of a quantity.

gaseous diffusion plant 

A facility where the percentage of uranium-235 is increased relative to uranium-238 by 

a filtering process using uranium hexafluoride gas.

kerma

Acronym for kinetic energy released per unit ma

lyselia grid

ss. Kerma is the sum of the initial 

kinetic energies of all the charged particles liberated by uncharged ionizing radiation 

(neutrons and photons) in a sample of matter, divided by the mass of the sample. 

Kerma is expressed in gray (or its submultiples), and, unless otherwise specified, 

refers to the energy liberated per unit mass in a small sample of tissue. Free-in-air 

kerma refers to the amount of radiation at a location before adjustment for any external 

shielding from structures or terrain.

A grid made of thin lead strips placed between the patient and the image to reduce the 

scattered radiation from the patient.

Manhattan Project

The code name for the U.S. effort to develop the atomic bomb.

occupational dose

Radiation dose received as the result of employment.

photofluorography

A radiographic procedure where the fluorescent image on a simple screen (without 

image intensifier) was recorded on film with a camera

photoflouroscopic

Viewing photographs taken of a fluoroscope (fluorescent screen imager for x-rays).

stereoscopic

Three dimensional viewing of photographic images, two views of the same image 

taken at slightly different angles

uncertainty

An estimate of the variety of a measurement, the amount a measurement may vary 

about its true value given the technique and circumstances of the measurement.
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X-ray

Radiation emitted when matter is bombarded with fast electrons. Also, a picture 

produced by exposing photographic film to X-rays that traverse the body.