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K-25 SITE, OAK RIDGE GASEOUS DIFFUSION PLANT ISSUES MATRIX

October 2012 Update – New or edited information appears in red text

No. TBD Issue SC&A Draft Finding NIOSH Response

1 0009-5 

(Occupational 

Internal Dose)

CLOSED

More guidance needed 

on appropriate 

enrichment 

assumptions.

More guidance is needed regarding 

appropriate enrichment to assume when 

interpreting uranium bioassay mass 

concentration data; the enrichment 

assumed for default isotopic distribution 

may not be appropriate.

Up to 1993, bioassay records for K-25 employees list results for 

uranium as mass measurements (normally in milligrams per liter) and 

gross alpha results (dpm/100 milliliters). Thereafter, isotopic uranium 

results are available. Gross alpha or isotopic uranium would typically 

be used for a dose reconstruction. Gross alpha measurements are 

favorable to the claimant since the results are more sensitive; the 

activity is known; and assumptions about enrichment are not necessary. 

However, if uranium mass bioassay is used and converted to total 

uranium alpha, the derived uranium results must be consistent with the 

gross alpha (or isotopic) bioassay. Table 5-1 will be revised to include 

3% enrichment as the default value. In addition, total uranium activity 

and gross alpha activity are assessed as uranium-234 as a claimantfavorable measure. This information will be clarified and incorporated 

into the next revision of the K-25 Occupational Internal Dose TBD.

SC&A Response: Agree with the NIOSH response, with one question: Would there be circumstances where the 3% enrichment default would not be appropriate given 

inclusion of reprocessed fuel in feed material? How would that issue be addressed? 

July 2011 Update: At the July 6, 2011, Work Group meeting, NIOSH confirmed that enrichment levels have no bearing on dose reconstruction, given reliance on gross 

alpha measurements, and that the 3% enrichment default value and U-234 as an assumed basis for claimant-favorable assessment would be added in the next TBD 

revision. Based on this discussion, the Work Group closed this issue.

2 0009-5

CLOSED

No default absorption 

(solubility) classes for 

intakes.

Absorption classes listed for UO3 and 

U3O8 appear to be incorrect. No 

discussion for high-fired uranium oxides. 

The compound of the material is not considered during the dose 

reconstruction process. Since there can be several related variables 

when reconstructing the internal dose, lung absorption types F, M, and S 

are evaluated for uranium and the most claimant-favorable type is 

assigned. Therefore, Table 5-3 will be deleted from the K-25 

Occupational Internal Dose TBD since it provides no added value. In 

addition, the TBD will be updated to clarify the evaluation of the lung 

absorption types for claimant favorability.

SC&A Response: Further clarification needed. How are high-fired uranium oxides (“class Y” or “super S”) addressed? These compounds would exhibit different 

biokinetic behavior when taken up in the body.

July 2011 Update: NIOSH indicated that there has been no evidence to date of any high-fired, insoluble uranium oxides at K-25, but would be vigilant on the issue. 

Based on this discussion, the Work Group closed this issue.
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3 0009-5

IN 

ABEYANCE

Default isotopic 

distribution not 

claimant favorable.

It does not contain Pu-238, Pu-240, Pu241, and Pu-242; Cm-242 and Cm-244; 

and it assumes only low enriched (2%) 

uranium; and the Tc-99 ratio is 

questionably low.

The default isotopic distribution listed in Table 5-6 as Pu-239 represents

total plutonium (all plutonium isotopes). This information is stated in 

Table 5-4, footnote b. A footnote with this information will be added to

Table 5-6 upon revision of the K-25 Internal Dose TBD.

Radionuclides Cm-242 and Cm-244 will be deleted from Table 5-2 

since these radionuclides may have been present only in trace quantities.

The actual enrichment of uranium at the K-25 Plant varied throughout

the years. Through 1964, K-25 was capable of enriching uranium up to 

93% U-235 (SRDB 16497). After the shutdown of the HEU facilities in 

1964 approximately 2 to 5% U-235 was produced (SRDB 16497). As 

stated in the response to Item #1, NIOSH agrees the default enrichment 

should be 3% and will revise the K-25 Internal Dose TBD accordingly.

After review of SRDB 16497, and in comparison to the default value 

listed for Paducah, NIOSH agrees the Tc-99 default value listed in 

Table 5-6 requires further evaluation. Values in Table 5-6 will be 

corrected in the next revision of the K-25 Internal TBD.

SC&A Response: Further clarification needed. If Cm-242 and Cm-244 are to be deleted from DR consideration, some confirmatory basis should be provided.

July 2011 Update: NIOSH indicated that while there is no evidence of Cm at K-25, there is a need to revisit Table 5-6 as part of the recycled uranium assessment to 

address its accuracy and completeness. Based on this discussion, the Work Group is holding this issue in abeyance awaiting NIOSH’s proposed changes.

Updated DCAS Response: In order to ensure that claimant-favorable activity fractions for recycled uranium contaminants are applied, the highest (except where noted) 

isotopic concentration values recorded in Table 2.4-1 of the Recycled Uranium Mass Balance Project Oak Ridge Gaseous Diffusion Plant (ref ID 016497) was adopted. 

The values are based on work activities, locations, and time frames posing the greatest potential for workers to be exposed to recycled uranium. The recorded 

concentrations come from activities performed during oxide conversion, cascade building operations, uranium recovery operations, and analytical laboratory analysis. In 

addition, the concentrations include potential worker exposure during the CIP/CUP campaigns. The activity fractions for RU exceed those currently listed in Table 5-6 of 

the K-25 Internal TBD; therefore, the assignment of RU contaminants are being revised and incorporated into the DRAFT K-25 Internal TBD.

4 0009-5

IN 

ABEYANCE

TBD inconsistent or 

lacks complete 

information on 

radionuclides.

General lack of consistency and lack of 

complete radionuclide guidance and 

information for facilities in tables 

provided. Several major radionuclides 

not shown in source terms for various 

buildings in Table 5-4.

The information in Table 5-4 of the K-25 Internal Dose TBD was 

obtained from Reference ID 16497. The radionuclides listed in Table 5-

4 are the RU constituents of most concern for each location. Table 5-2, 

lists all the radionuclides encountered at K-25. However, as previously 

stated in Response #3, Cm-242 and Cm-244 will be removed from 

Table 5-2 upon revision to the K-25 Internal Dose TBD. A footnote 
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will be added to Table 5-4 to better clarify this information.

SC&A Response: Disagree. SC&A’s comments point out a number of information sources that suggest that ID 16497 may not be complete and that the TBD does not 

account for all buildings that may have contained radiological hazards. NIOSH should corroborate its source term citations and building listings beyond ID 16497.

July 2011 Update: NIOSH agreed that the indicated tables will be corrected. Based on this response, the Work Group is holding this issue in abeyance. 

Updated DCAS response: Table 5-4 will be removed from the Internal TBD since the information is not used in the dose reconstruction process. The radionuclides of

concern at K-25 will be reported in the revised TBD. The Oak Ridge Gaseous Diffusion Plant consisted of over 400 buildings; it is therefore not feasible to include all of 

them in the TBD. However, a table listing the buildings and support facilities involved in uranium operations will be included in the revised TBD. A more 

comprehensive list of buildings, time frame of operations, and activities was added to the DRAFT K-25 Site Description. Additional references were citied regarding the 

source term and facilities at the K-25 Plant.

5 0009-5

IN 

ABEYANCE

Lack of information 

regarding incidents.

Lack of incident information for those 

with significant intakes could hinder 

accurate interpretation of bioassay results 

and identification of intakes of 

unmonitored or inadequately monitored 

workers.

Because dose is always assigned when there are bioassay results, 

detailed incident information can be helpful but in most cases is not 

necessary. Many cases are completed using over- or underestimates, 

where maximizing or minimizing assumptions are made. In the small 

fraction of cases needing best estimates, reasonable but claimantfavorable assumptions are made when there is a lack of information, 

such as intake date. In such cases, it is more likely that the additional 

information would result in a smaller dose estimate. For example, urine 

samples are typically collected within a few days of a known incident. 

If there is no incident identified in the file, the default date would be at 

the midpoint since the previous sample, which would yield a larger 

intake. If necessary, a supplemental request to the site for additional 

information regarding the incident in question can be made.

SC&A Response: Agree that incident data are helpful in some cases, but not necessarily in most cases; but disagree with the implication that NIOSH should not seek to 

locate whatever incident data exist (apparently an incident notification system did exist) for the sake of cases that would benefit.

July 2011 Update: NIOSH indicated that it would try to identify a more complete set of incidents, but could not predict what additional information would be available. 

The Work Group will hold this issue in abeyance awaiting NIOSH’s actions to resolve this issue.

Updated DCAS Response: Dates, buildings, and description of significant incidents with internal dose potential will be discussed in the revised K-25 Site Description and 

Occupational Internal Dose TBDs.

6 0009-5

IN 

Coworker data use and 

approach for 

unmonitored 

employees may not be 

a. Use of median bioassay data 

values from 1948 to 1988 for 

uranium intake rates and 1978 to 

1988 data for Tc-99 intake rates 

may not be reasonable or claimant 

NIOSH agrees that there is variation in the intake rates; that is why the 

median value of a lognormal distribution is assigned along with the 

geometric standard deviation. The dose reconstructor can assign the 

84th percentile when it appears warranted for a specific case, but the 

routine assignment of the 84th percentile to all unmonitored individuals 
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ABEYANCE appropriate. favorable. NIOSH needs to 

determine if work processes, 

exposure conditions, and 

radiological controls for 1945-1947 

were similar to periods that followed

to permit use of earlier intake rates. 

Also, SC&A found the guidance for 

dose reconstructors to be vague, 

advising that the “maximum 

reasonable coworker dose” be 

applied [emphasis added], without 

defining what is meant by 

“reasonable.”

b. Not clear whether assumed acute

intakes would be more claimant 

favorable than stipulated chronic 

intakes. While NIOSH default 

assumption is to assume chronic intakes, 

stronger basis should be provided for 

why that is necessarily more claimant 

favorable given K-25 exposure history of 

incidents and variable uranium releases. 

c. To what extent higher solubility 

uranium compounds (e.g., Type F) 

would not have been detectable once a 

bioassay program was established in 

1948. NIOSH is using intakes modeled 

from 1948-1988 to estimate intakes of 

workers prior to 1948; however, if any 

workers had relatively large intakes of 

Type F uranium in 1945-1946, it is 

possible bioassays in 1948 would not 

have detected them. 

d. Whether use of the outdated ICRP 

23 vs. 89 volume parameters would 

bias DR calculations in a claimantunfavorable manner. Urine bioassay 

is not reasonable because it assumes that all unmonitored workers were 

routinely exposed to larger concentrations than monitored workers. 

ORAUT-OTIB-0060, Internal Dose Reconstruction, provides 

information for unmonitored workers and the assignment of coworker 

dose. This TIB will be added to the Reference section of the K-25 

Internal Dose TBD upon revision.
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data was normalized to 1,400 ml, which 

is from ICRP 23, currently an outdated 

reference updated with ICRP 89 that uses 

1,600 ml for 24-hr excretion volume, a 

10% difference.

SC&A Response: Disagree with NIOSH response in that it is unresponsive to key SC&A review issues including whether earlier operations and radiological controls 

can be normalized over such a large time period, to what extent higher solubility uranium compounds (e.g., Type F) would not have been detectable once a bioassay 

program was established, to what extent multiple acute vs. chronic exposures would be more bounding, and whether use of the outdated ICRP 23 vs. 89 volume 

parameters would bias DR calculations in a claimant-unfavorable manner.

July 2011 Update: NIOSH pointed out that it actually applies the median and 95th percentile for coworker dose assignment; the 84th percentile distribution is only used 

to derive the GSD. SC&A pointed out while it accepts that response, there were other sub-issues imbedded in the SC&A profile review finding (which were highlighted 

in its response). Following some discussion of the sub-issues, SC&A agreed to highlight them in a revised finding description in this matrix for NIOSH reconsideration. 

The Work Group thereby has held this issue in abeyance to permit NIOSH an opportunity to review them.

SC&A Response (October 2012): SC&A highlights description of “sub-issues” identified in its site profile review finding, which were discussed at the July 6, 2011 

WG meeting.

Updated DCAS response for sub issues a - c above: 

Parts A&C) Regarding whether the 1948-1988 intake rates can be applied for 1945-1947:

As described in ORAUT-OTIB-0035, urinalysis results were fit into IMBA using types F, M, S materials to derive intake rates for 1948-1988. The results of the IMBA 

fitted data are graphically presented in B-1 through B-6 of ORAUT-OTIB-0035. Those figures contain the curves of the predicted urine concentration from the derived 

intake rate in comparison to the actual bioassay results. It was determined that the use of a single chronic (continuous) intake was appropriate since the uranium excretion 

rates were relatively constant from 1948-1988. The solid lines in Figures B-1 to B-6 show the individual fits to the 50th- and 84th-percentile excretion rates. Although the 

fitting routines for the intakes involve the effects of the biokinetics of the lung solubility type of the inhaled particulates at various times post-intake, the data indicates 

that the spread of the derived intake rates are directly proportional to the urine concentration data for all three solubility types. 

However, to ensure claimant favorability for the time period of 1945-1947, the coworker intake rate tables are being expanded to allow the assignment of the 95th

percentile uranium intake rates as a constant distribution. Verbiage is being added so dose reconstructors would assign the 95th percentile coworker intake rate for 

employees who have no monitoring data, were in an unknown work environment, and could have been routinely exposed to airborne radioactivity hazards.

Part B) Regarding whether assumed acute intakes would be more claimant favorable than stipulated chronic intakes: 

OTIB-0035 assigns a single continuous intake due to the relatively consistent urine results over the years. While the assumption of constant chronic intakes is considered 

to well describe the exposure conditions at K-25, it is also an acceptable method to assess exposure to multiple acute intakes when the time of the intake is not known. 
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This is part of the technical justification for using a chronic intake model to assign dose and missed dose from a urine bioassay result.

All DCAS coworker models are developed and applied under the assumption that an unmonitored worker receives constant chronic intakes. As a result, this issue is 

global for all coworker models. Therefore, concerns with this methodology are to be dealt with outside the Gaseous Diffusion Plant Working Group.

Part D) Regarding use of ICRP 23 versus ICRP 89:

The use of ICRP 23 versus ICRP 89 is a global issue to be dealt with outside the Gaseous Diffusion Plant Working Group.

7, 9,

and

11

0009-6

(Occupational 

External Dose)

IN 

ABEYANCE

Uranium cylinder 

storage yard dose may 

be underestimated.

Chronic neutron 

exposure opportunities 

may have been 

overlooked for early 

years.

Reliance on single 

neutron-to-photon 

ratio for entire plant 

questionable.

Dose reconstructors instructed to add 

missed neutron dose only for workers in 

the cylinder yards, although their 

dosimeters were insensitive to any dose 

rate due to neutrons below the NTA 

cutoff (somewhere between 0.5 and 1.0 

MeV).

Little attention was apparently paid to 

the possibility of neutron exposure in the 

early years. It would be prudent to 

revisit whether some categories of 

workers may have been exposed to 

chronic low-level neutron exposure.

K-25 plant had number of potential 

sources of neutron exposure that will 

have varied over time as processes, 

facilities, procedures, impurities, and 

enrichments changed.

The probable hazard from preparation and storage of UF6 at K-25 was 

identified in 1943 (SRDB 8328). SRDB 21791 describes many 

elements of the routine ORGDP radiation safety program to detect, 

measure, and control worker radiation exposure to include the use of 

personnel neutron dosimeters.

SRDB 29760 describes an evaluation of potential external radiological 

exposure from K-25 Plant UF6 Cylinder Storage Yards to members of 

the public and other unmonitored individuals. The exposure scenario 

with the highest dose involved unmonitored site workers because these 

individuals could access the radiological posted areas present inside the 

site fencing. The estimated dose in this study was 125 mrem/yr based 

on a worker spending 250 hrs in a year (one hr per work day) in an area 

with measured dose equivalent rates that exceeded the 0.4 mrem/hr used 

to establish the boundary of the radiological area posting. The dose 

equivalent rate of 0.4 mrem/hr includes exposure to both gamma and 

neutrons using a conservative 4:1 gamma to neutron (i.e., neutron to 

gamma dose ratio = 0.25) dose ratio.

Personnel dosimetry methods were very similar among the respective 

DOE Oak Ridge office gaseous diffusion plants (SRDB 79353).

Dose reconstructors evaluate the energy employees' potential neutron 

exposure by reviewing the employees' job title, work location(s), and 

time period. If applicable, neutron dose is assigned using the neutronto-photon ratio, as noted in the K-25 External Dose TBD Section 6.5.3.
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 ************

ORGDP did have capabilities to detect and measure significant neutron 

exposures as described in the respective “Standard Reference 

Information” provided by the Union Carbide and Carbon Corporation, 

(SRDB 21791). See for example Standard References SP-150, SP-152, 

SP-160, and SP-161.

However, for reasons described in the DOE “Guide of Good Practices 

for Occupational Radiological Protection in Uranium Facilities” (SRDB 

4617) and in the NIOSH Health Hazard Evaluation Report (SRDB 

10913), neutron exposures were considered to be insignificant in 

comparison with DOE radiation protection standard and also in 

comparison with beta/gamma exposure and potential intakes. As well, 

consider the response to #7 above, particularly with respect to dose 

reconstruction practices that evaluate the energy employees' potential 

neutron exposure by reviewing the employees' job title, work 

location(s), and time period. If applicable, neutron dose is assigned 

based on using the neutron-to-photon ratio, the calculated missed 

neutron dose, or an assigned unmonitored neutron dose based on 

employment.

 **********

Limited information has been received with respect to measured neutron 

and photon dose rates in the respective DOE Oak Ridge Office Gaseous 

Diffusion Plants because of the lack of personnel monitoring for neutron 

exposures, which were anticipated to be comparatively low. There are 

three studies of measured dose that were looked at. One study 

concerned calculation of the neutron-to-photon ratio based on the UF6

cylinder painting project (SRDB 13682) performed at the Paducah 

Plant. The second study, SRDB 8122, was a neutron study performed at 

Portsmouth. The results from these two studies can be reasonably 

applied to K-25 because of their operational similarities and common 

dosimetry programs. The studies determined that a 0.2 neutron to 

gamma ratio was conservative and is prudent for the worst case areas 

which are the cylinder storage yards. A third study (SRDB 29760) 

describes an evaluation of potential external radiological exposure from 

K-25 Plant UF6 Cylinder Storage Yards to members of the public and 

other unmonitored individuals. The exposure scenario with the highest 
K-25 Site Issues Matrix Page 8 of 12 Updated by SC&A – October 8, 2012 

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dose involved unmonitored site workers because these individuals could 

access the radiological posted areas present inside the site fencing. The 

estimated dose in this study was 125 mrem/yr based on a worker 

spending 250 hrs in a year (one hr per work day) in an area with a 

measured dose equivalent rate that exceeded the 0.4 mrem/hr used to 

establish the boundary of the radiological area posting. The dose 

equivalent rate of 0.4 mrem/hr includes exposure to both gamma and 

neutrons using a conservative 4:1 gamma to neutron (i.e., neutron to 

gamma dose ratio = 0.25) dose ratio. According to the survey (SRDB 

93592), performed at the K1066E cylinder storage yard, of the 86 

sampling points only 9 locations resulted in detectable neutron levels. 

The gamma to neutron ratio was calculated based on only a total of 9 

gamma and 9 neutron measurements. Since the data are limited and the 

actual n:p ratio would be lower than the TBDs value of 5:1 if all 86 

sampling points were used, NIOSH feels that the 5:1 ratio currently 

documented in the K-25 TBD is favorable to the claimant.

The Work Group asked that SC&A issues 7 and 9 be combined:

SC&A Response (Issue 7): Further clarification needed. Will NIOSH revise the TBD to reflect the estimates contained in SRDB 27960, both for external exposure 

for unmonitored workers and the neutron component? (as opposed to the 75 mrem estimate now included?).

SC&A Response (Issue 9): Agree that neutron doses were a relatively small component of overall dose at the GDPs, but question whether it would be feasible for 

NIOSH to assign neutron dose (based on a neutron-to-photon ratio) without establishing what operations had a potential for lower-energy neutron exposure and what 

workers would have been involved.

SC&A Response (Issue 11): Agree that based on the available neutron surveys cited, the 5:1 photon/neutron ration appears bounding. However, these studies all 

focused on cylinder yards, so SC&A’s concern that different operations and time periods where neutron doses may have been elevated and ratios may have been different 

(e.g., due to shielding) is not satisfied. However, SC&A acknowledges that this question may not be answerable without additional documentation regarding historic 

neutron exposures at K-25.

July 2011 Update: In response to all three SC&A neutron issues at the July 6, 2011, Work Group meeting, NIOSH indicated that it had found inconsistencies in how 

neutron exposure were addressed across the three GDPs and were in the process of re-evaluating its current approach for K-25. The Work Group will hold this issue in 

abeyance until NIOSH provides its revised approach.

Updated DCAS response: Since employees may have been exposed to neutrons while working in certain facilities or areas of the plant, instructions for the assignment of 

unmonitored and/or missed neutron doses will be added to the External Technical Basis Document (TBD). This will be accomplished by assigning neutron-to-photon 

ratios. The N:P ratios will be determined from the data obtained from the GDPs (SRDB 13682, 8122, 108666). In addition, a report, ORAUT-RPRT-0060, “Neutron 

Dose from Highly Enriched Uranium,” has been DRAFTED and is currently in internal review. This report is anticipated to provide support for a separate neutron-tophoton ratio for workers who may have been routinely exposed to highly enriched uranium. Once this evaluation process is completed, instructions will be provided to 
K-25 Site Issues Matrix Page 9 of 12 Updated by SC&A – October 8, 2012 

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dose reconstructors in the External TBD

8 0009-6

CLOSED

Until 1980, some 

dosimeters only 

processed upon 

request.

Until 1980, the TBD states that 

dosimeters were only processed upon 

request; another TBD statement points 

out that ORNL provided K-25 dosimeter 

and processing technical support starting 

in 1945. Unclear from these two 

statements whether dosimeters were 

routinely processed for workers or only 

done in some random frequency.

Beginning in 1945, through October, 1951, only the workers entering 

controlled radiation areas and those likely to receive a measurable dose, 

were assigned a dosimeter. Supervisors requested film badges and/or 

film rings for those employees working in areas where radiation 

exposure was likely (SRDB 16497, SRDB 21791, SRDB 13787). 

Supervisors made this decision with the support of the Health Physics, 

Medical, and Industrial Hygiene staff, daily readings from portable 

radiation detection instrumentation, pocket chambers, daily hand 

monitoring of employees, and spot checks to determine the extent of onthe-job contamination. The assigned dosimeters were provided by the 

Oak Ridge National Laboratory (ORNL) and the film badges were also 

processed by ORNL on a bi-weekly basis (SRDB 16497). In November 

1951, through 1979, dosimeters were issued to the entire work force as 

part of their security/dosimetry badge. Again, only those likely to 

receive a measurable dose were processed. The dosimeters and the 

processing were provided by ORNL through 1979. Starting in 1980

(SRDB 20126), all issued dosimeters were processed regardless of the 

area the employee worked in or job activities. For dose reconstruction 

purposes, if an unmonitored worker had radiological exposure potential 

based on their occupation and/or potential work locations, then 

coworker doses are evaluated and assigned as necessary. Upon revision 

to the K-25 External Dose Technical Basis Document, a more detailed 

description of the assignment and processing of the dosimeters shall be 

added to better clarify site practices.

SC&A Response: Agree with NIOSH response.

July 2011 Update: The Work Group closed this issue at its July 6, 2011, meeting.

10/12 0009-7/8

IN 

ABEYANCE

Potential exposures to 

Tc-99 betas not 

recorded.

All beta dosimetry 

based on uranium slab 

calibration.

Potential exposure to beta fields needs to 

be more fully evaluated; likely that film 

badges used in the 1945-1979 period 

could not detect Tc-99 (albeit details 

regarding dosimeter wrapping and cover 

materials would help judge this).

Given that some workers were routinely 

exposed to Tc-99, and given dosimeters 

could have partly or completely missed 

Neither film nor TLDs will likely detect the low energy beta from Tc99. As discussed on pages 13 and 17 of TKBS-0009-6, Tc-99 poses 

minimal external exposure potential because of limited range and the 

shielding afforded by clothing and gloves. Energy employee exposure 

situations that potentially involved Tc-99 skin contamination would be 

addressed using VARSKIN to assist with the skin dose estimation.

 *********

SRDB 3902 and 30642 estimated radiation doses received by workers in 
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lower energy beta fields, evaluation 

needed to determine degree to which Tc99 was under-reported or missed 

entirely.

the feed plant from transuranics (TRU) and fission products (FPs) 

during the processing of uranium recycle materials handled during the 

period of 1953 through 1973. TRU and FP nuclides, including 99Tc, 

were processed in addition to uranium. Recorded doses for operators 

and maintenance mechanics at the Paducah Feed Plant were examined. 

External exposure from these nuclides contributed a small fraction in 

comparison with exposure from normal processing of uranium.

The DOE “Guide of Good Practices for Occupational Radiological 

Protection in Uranium Facilities” (SRDB 4617), states the low energy 

beta radiation from 99Tc is effectively attenuated by the protective 

clothing required for contamination control (e.g., one pair of industrial 

cloth coveralls, one pair of impermeable (Tyvek) coveralls and heavy 

neoprene gloves). As noted earlier, the primary hazard from 99Tc 

concerns skin contamination. Energy employee dose reconstructions 

that involve skin contamination, including Tc-99, are addressed if 

significant using VARSKIN.

The Work Group asked that SC&A issues 10 and 12 be combined:

SC&A Response (Issue 10): Disagree that NIOSH has provided sufficient basis (discussion of quantities involved, contamination experience, doses reported, etc.) for 

its position that Tc-99 was of minimal dose significance outside of skin contamination, which would apparently be addressed on a case-by-case basis. The TBD should 

include more treatment of this exposure source. 

SC&A Response (Issue 12): Disagree that the Tc-99 source term contribution has been sufficiently characterized (per SC&A response to Issue 10 above). 

July 2011 Update: At the Work Group’s July 6, 2011 meeting, NIOSH agreed that it would address Tc-99 skin contamination and external shallow dose potential for 

dose reconstruction into a white paper addressing all three GDPs, with emphasis on the chronic vs. incident nature of contamination, specific operations where 

contamination is likely, and significance of skin contamination. On this basis, the Work Group will hold these issues in abeyance awaiting completion of this NIOSH 

paper.

SC&A Response (October 2012): NIOSH provided ORAUT-RPRT-0059, External Exposure to Technetium-99 at the Gaseous Diffusion Plants, dated Feb. 7, 2012. 

SC&A subsequently recommended closure of this issue for the Paducah Gaseous Diffusion Plant, and likewise, recommends closure of the issue for the K-25 TBD.

SECONDARY ISSUES

13s 0009-5

CLOSED

There is a lack of 

guidance on bioassay 

interpretation.

The TBD needs to either provide more 

specific guidance to the dose 

reconstructor on several parameters that 

must be chosen or adjusted for intake 

and dose assessment, or reference the 

Upon revision to the K-25 Internal TBD, and consistent with Response 

#1, clarification will be made to the bioassay data and/or appropriate 

references will be added. OTIB-0060 provides guidance on the general 

process of assessing intakes of radioactive material; the DRs are trained 

on this document.
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documents that will provide this 

guidance.

SC&A Response: Agree with NIOSH response.

July 2011 Update: The Work Group closed this issue at its July 6, 2011 meeting.

14s 0009-4

CLOSED

There is no 

comparison between 

measured and 

predicted ambient 

radiation dose data.

A comparison between personnel 

dosimetry data (measured) with 

estimates based on ambient 

environmental exposures (predicted) 

would prove useful to validate the 

methods for reconstruction external 

environmental doses.

No comparison is made between environmental doses and personnel 

badge data because there are two different purposes for the data and 

their application is job dependent.

SC&A Response: Agree with NIOSH response.

July 2011 Update: The Work Group closed this issue at its July 6, 2011 meeting.

15s 0009-5

CLOSED

The TBD does not 

provide a consistent 

time period for the 

processing of RU at 

K-25.

The TBD should identify specific time 

periods that RU and its default isotopic 

distribution are to be assumed in intake 

assessment. This is not consistent with 

current guidance, and may not be 

claimant favorable.

Section 5.3 of the K-25 Internal TBD states the processing of recycled 

uranium began in 1952 at the K-25 Plant. The normal process during 

dose reconstruction is to include the RU contaminants beginning in 

1952, through the energy employee’s termination date. In the next 

revision to the TBD it will be clarified that RU contaminants will be 

assigned for all years at K-25 beginning in 1952.

SC&A Response: Agree with NIOSH response.

July 2011 Update: The Work Group closed this issue at its July 6, 2011 meeting.

16s 0009-3

CLOSED

The TBD fails to 

adequately define 

frequency and assess 

all types of X-rays in 

occupational medical 

exposure.

NIOSH should review its interpretation 

of included medical exposure, and 

should reasonably adopt a broader 

interpretation in the K-25 Occupational 

Medical TBD of occupational medical 

dose, as provided in the most recent 

version of ORAUT-OTIB-0006 (Kathren 

and Shockley 2005).

By regulation, only X-rays performed for screening can be included in 

occupational dose reconstruction (42 CFR 81). Screening would 

include X-rays performed for respirator certification, beryllium workers, 

asbestos workers, food handlers, termination exams, etc., in addition to 

radiographic screening of workers to monitor for disease.

When x-ray records are requested from the site, it is assumed that all 

sources of records have been searched, including microfiche film. 

There is supporting evidence for K-25 that the film jacket for each 

worker contains all the X-rays ever received by the individual while 

employed at the K-25 Plant (SRDB 11105). Therefore, when actual Xray records are provided by the DOE, the X-ray dose is assigned 
K-25 Site Issues Matrix Page 12 of 12 Updated by SC&A – October 8, 2012 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution.

according to the frequency and type of examinations provided in the 

records. When no records are available, then the frequency listed in 

Table 3-1 of the K-25 Occupational Medical TBD is followed. 

ORAUT-OTIB-006, Revision 03 will be added to the reference section

when the K-25 Occupational Medical TBD is next revised.

SC&A Response: Agree with NIOSH response.

July 2011 Update: The Work Group closed this issue at its July 6, 2011 meeting.

17s 0009-3

CLOSED

Techniques and 

protocols increase 

uncertainty of dose 

conversion factors 

(DCFs) listed in the 

TBD.

The Occupational Medical Dose TBD 

(Turner 2006) provides little 

documentation to support the assumed 

techniques and protocols applied to 

calculate the dose.

The K-25 Occupational Medical Dose TBD states that PA chest X-ray 

exams were performed beginning in 1944.

From 1945 to 1956, 86% of these examinations were PFGs (SRDB 

11105). Based on information received from the site X-ray technician, 

lateral chest exams were not conducted until the 1970s (SRDB 11105)

which is consistent with radiology practice of that time. From a review 

of K-25 X-ray records, it is clear that lateral chest exams were not 

performed routinely for screening until the 1970s (SRDB 11105).

Upon revision to the K-25 Occupational Medical TBD, a discussion of 

the substitute DCFs will be incorporated. In addition, a new revision to 

ORAUT-OTIB-0006 will be published in the next several months. This 

revision has a better description of the choice of substitute DCFs for 

poorly collimated beams and will be added to the reference section of 

the K-25 Occupational Medical TBD.

SC&A Response: Agree with NIOSH response.

July 2011 Update: The Work Group closed this issue at its July 6, 2011 meeting.