White Paper 

Review of the NIOSH “White Paper on Fernald Th-230 

and Other Associated Radionuclides – Rev. 7” 

 

Prepared by 

S. Cohen & Associates 

1608 Spring Hill Road, Suite 400 

Vienna, Virginia 22182 

Saliant, Inc. 

5579 Catholic Church Road 

Jefferson, Maryland 21755

May 2010 

Disclaimer 

This document is made available in accordance with the unanimous desire of the Advisory Board on 

Radiation and Worker Health (ABRWH) to maintain all possible openness in its deliberations. However, 

the ABRWH and its contractor, SC&A, caution the reader that at the time of its release, this report is predecisional and has not been reviewed by the Board for factual accuracy or applicability within the 

requirements of 42 CFR 82. This implies that once reviewed by the ABRWH, the Board’s position may 

differ from the report’s conclusions. Thus, the reader should be cautioned that this report is for 

information only and that premature interpretations regarding its conclusions are unwarranted.
Draft Review of NIOSH White Paper 2 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

1.0 INTRODUCTION 

During the Fernald Work Group meeting held on January 29, 2010, the Work Group discussed 

six issues identified by SC&A. Issue 4 is concerned with NIOSH’s approach for reconstructing 

the doses to workers exposed to Ra-226 and Th-230. One aspect of this issue deals with Fernald 

operations where workers could have been exposed to material that contained relatively high 

levels of Th-230, especially under conditions where there were relatively low levels of Ra-226 

and uranium. NIOSH addresses this issue in “White Paper on Fernald Th-230 and Other 

Associated Radionuclides – Rev. 7,” by Bryce L. Rich and Paul Ruhter (January 6, 2010). 

During the Work Group meeting, SC&A was tasked with reviewing that white paper. This 

report is provided in response to that request. 

1.1 Purpose of NIOSH’s White Paper 

The stated purpose of NIOSH’s white paper is to “provide information necessary to perform dose 

reconstruction for those workers at the Feed Materials Production Center (FMPC) who may have 

been exposed to, but not monitored for, specific uranium decay contaminants that were present in 

plant processes.” This paper specifically addresses the expressed concern for elevated Th-230 

concentrations, which is most evident in the isotopic characterization of raffinates stored in Silos 

1, 2, and 3. Other uranium decay product isotopes are also addressed, including radium and its 

decay products. Doses from the intake of radium resulting from a short-term operation of 

dumping barrels of hot raffinates from the processing of pitchblende ores at other plants 

(primarily Mallinckrodt) into Silos 1 and 2 were discussed briefly in previous meetings of the 

Procedures Subcommittee and in another SC&A white paper (previously distributed to the Work 

Group). Those discussions centered around ORAUT-OTIB-0025, which describes NIOSH’s 

generic approach to reconstructing Ra-226 body burdens and intakes based on radon breath 

analysis. 

As stated in the NIOSH white paper, the primary concern of the white paper is: 

Th-230, which is a long-lived decay product of U-234, which in turn is a decay 

product of U-238 – all of which would be present in the primary feed materials 

(pitchblende ores and uranium mill yellowcake) during the early years from 

startup to 1971. 

1.2 Basic Method for Calculating Th-230 Doses as Described in the NIOSH White 

Paper 

NIOSH proposes to calculate bounding intakes of Th-230, based on intakes from uranium, as 

described in the following excerpt from the NIOSH white paper: 

Since uranium was the primary material in the process and was low in specific 

activity, heavy metal toxicity from the uranium was considered the initial and 

limiting health concern. An extensive urine sampling program was administered 

in concert with an equally comprehensive air sampling program to guide 

personnel protection programs, i.e., respiratory protection, improvements in 
Draft Review of NIOSH White Paper 3 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

process containment, etc. For this reason, the approach developed in this paper 

has determined claimant favorable values for the historical levels of the trace 

quantities of contaminant isotopes relative to the levels of uranium intake, which 

was determined by a routine urine bioassay program. A dose reconstruction 

approach is proposed that once a determination of the intake of uranium has been 

made from bioassay data, unmonitored intakes of the other isotopes can be added 

based upon a bounding analysis of the levels that could have been encountered 

relative to the levels of uranium present in the given work areas. 

With respect to reconstructing doses from Th-230, the NIOSH white paper presents a dose 

reconstruction strategy that takes advantage of the proportion of Th-230 relative to U-238 and 

changes in operations as a function of time, as described in the following excerpt from the 

NIOSH white paper: 

The exposure of workers to Th-230 plus other daughter products in Plants 2/3 

and 1 can be appropriately bounded by adding an intake of Th-230 that is equal 

to the intake of U-234 or U-238 in natural uranium determined in mass units. 

The isotopic ratios in Silo 3 or Silos 1 and 2 to uranium are not used as defaults, 

since the recorded air activity levels with the associated exposure potential within 

the raffinate areas (represented by Silo 3 analyses) were so demonstrably low. 

The primary elevated Th-230 plus daughters exposure potential existed primarily 

in the high air activity areas in Plant 2/3 and Plant 1, which sampled, mixed, etc., 

ores and concentrates also.

Following the major process of concentrate feeds in the early to mid 1970s, 

process of uranium feeds shifted to other materials without elevated Th-230 

contaminants. All concentrates (AEC stockpile) were consumed in 1977 and 

other materials, including enriched uranium, became the primary feeds. Hence 

not only the total production but specifically the use of concentrate feeds (with 

elevated Th-230 and daughters) were reduced to less than 10% of previous highs. 

Thus the values in Table 3 should be reduced to 10% as a claimant favorable 

default to account for possible continuing Th-230 exposures. Also, in order to 

account for the fact that internal process equipment and some residual process 

materials that could have Th-230 contaminants existed in the plant the 

assumptions outlined in OTIB-70 were used to demonstrate that aging of 

contaminants reduce the resuspension of those contaminants into exposure areas 

to less than 1%, which further validates the reduction of default values to 10% as 

a conservative assumption.

2.0 FINDINGS ASSOCIATED WITH NIOSH’S PROPOSED METHOD OF 

CALCULATING TH-230 DOSES 

The NIOSH white paper describes four different categories of areas where workers could have 

been exposed to Th-230, as follows: 
Draft Review of NIOSH White Paper 4 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

(1) Areas where uranium and U-238 chain daughters, including Th-230 and Ra-226, are 

present, as for example, the pilot plant (during the initial operation of FEMP); Plant 1 

(sampling, homogenization and milling operations); Plants 2 and 3 (areas where chemical 

processing of uranium ores took place, through the three-step process; digestion, 

extraction, and denitration); Plant 8 (Recovery Plant). Facilities and operations that fall 

within this category are distinguished by the fact that U-238 and its progeny are all 

present. For these areas, NIOSH proposes to calculate U-238 intakes from bioassay 

results and to add an intake of Th-230 that is equal to the intake of U-238. The activity 

ratio of Th-230/U238 intakes may be discussed but, in theory, bioassay data that provide 

information on the concentration of uranium in urine can be used directly to estimate the 

intake rate of not only uranium, but also its progeny, including Th-230 and Ra-226, if 

workers in these areas did not perform additional jobs where U-238 is not present.. 

(2) The raffinate areas located in Plant 3: In these areas, Th-230 is present after separation 

from uranium. Ra-226 is present in some of the operations, but not in all of the processes 

conducted in the raffinate areas of Plant 3. As explained in NIOSH’s white paper: 

...the objective of the extraction processes was to separate uranium from the 

feed stream; the impurities, i.e., anything other than uranium, were extracted 

into waste streams called raffinates. ...

The Hot Raffinate Building (3E) was utilized to filter insolubles from UNH 

and to process the raffinates. The Purex process resulted in raffinate waste 

streams into which those isotopes and material contaminants were extracted. 

This is the primary source of contaminants in the Silos, with relatively 

concentrated Th-230. 

The raffinate areas included hot and cold sides. The liquid raffinate from the extraction 

process contained valuable metal oxides. These oxides were recovered from the liquid 

raffinate and placed in the Metal Oxide Storage Tank. There were two streams, 

depending on where the raffinate originated. Hot raffinates were those resulting from 

Ra-containing ores, while cold raffinates were Ra-free. Hot raffinates were first 

processed to remove the Ra. The filter cake was mixed with water and calcium oxide, 

and the resulting slurry was pumped to the K-65 silos for storage. The purpose of the hot 

raffinate treatment was to segregate the radium-bearing insolubles from the slurry. The 

process ended with a precipitate of Ra (Ra cake) and Ra-free filtrate continuously 

pumped to the combined raffinate area, where it was mixed with a stream of cold 

raffinate slurry before being evaporated. The Ra cake (K-65) was reslurried with an 

alkaline solution, and after processing, went to the K-65 storage. (CCC 1951, “Plant 2/3, 

Institutional History and Exposure Database, produced under the direction of Susan 

Pinney, 1998”) 

The filtered hot and cold raffinate streams were received in the combined raffinate area. 

The combined raffinate stream was evaporated to obtain a concentrated metal nitrate 

solution [CCC possibly 1956 (date unclear)]. Facilities and operations that fall within 

this category are distinguished by the fact that Th-230 and/or Ra-226 are present, but 
Draft Review of NIOSH White Paper 5 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

workers are exposed to insignificant quantities of uranium. As the exposure to uranium 

is not significant, uranium bioassay results, if existent, are of no value to calculating 

Th-230 or Ra-226 exposures. NIOSH’s White Paper discards exposures to alphaemitting nuclides in these areas, by stating that: 

...the workers in the raffinate areas experienced airborne concentrations that 

were consistently at the same levels as were assigned to the records clerks 

and administrative assistants. These levels should be considered ambient 

levels very near the detection limit of the monitoring equipment. The value of 

0.1 MAC (maximum allowable concentration) or NCG (National Lead 

Concentration Guide) is the same value consistently reported for those areas 

considered to represent background levels. 

(3) Silo Areas 1 and 2, where Th-230 and Ra-226 are present: 

NIOSH White Paper explains that: 

The raffinate streams from the early Fernald processing (1953 to 1955) of 

Pitchblende Uranium ores were stored in Silos 1, 2, since they were the 

property of the Belgian Government Agency. Also in the 1955 to 1958 time 

period approximately 13,000 barrels of pitchblende ore raffinates were 

slurried and added to Silos 1 & 2 from another Site.

Historical core sampling was performed and the mean isotopic values at the upper 95% 

confidence interval were reported in Table 2 of the White Paper. 

During a short period of time (1953–1958) when pitchblende ore raffinates were shipped 

to Fernald from other AEC sites in approximately 13,000 drums for disposal in Silos 1 & 

2, the transfer operations were monitored and radon breath bioassay data were collected. 

These data are available for use in estimating radium intake, as discussed in ORAUTOTIB-0025 (2005). NIOSH’s white paper does not mention how the radon breath 

analysis results are going to be used to calculate Th-230 intakes. 

NIOSH’s White Paper does not make any reference on how to calculate Th-230 or 

Ra-226 doses to workers involved in other jobs related to Silos 1 & 2 besides the transfer 

of the 13,000 drums. 

(4) The Silo 3 Areas where Th-230 is present in much higher activities than U-238 or 

Ra-226: 

According to the NIOSH white paper: 

The raffinate streams from the processing of uranium mill concentrate feeds 

during the 1955 to 1971 time period were stored initially in Silo 3, because 

they were a dry powder resulting from the acid recovery calcining primarily 

from domestic and Canadian mines and mills. Later, the extraction process 

was changed to the use of dilute nitric acid, which allowed the raffinate to be 
Draft Review of NIOSH White Paper 6 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

 

neutralized and disposed of directly as a slurry to pit 5, eliminating the need 

for calcining to recover the nitric acids.

This facility is distinguished by the fact that Th-230 is present in the waste stream at 

concentrations that are high, relative to the concentrations of uranium and Ra-226. 

Hence, it might be difficult to estimate Th-230 intake rates for workers that handled this 

material, because of uncertainties in the proportion of Th-230 to either uranium or 

Ra-226. NIOSH’s White Paper does not make any reference on how to calculate doses to 

workers involved in jobs related to Silo 3. 

Finding 1: The fundamental strategy, as adopted by NIOSH to reconstruct Th-230 intake 

rates, presents many challenges to the dose reconstructor. 

Some of our major concerns are as follows: 

(1) For Category 1 areas, the reconstructed Th-230 intakes are only valid for workers that did 

not perform jobs or spend time in the raffinate areas of Plant 3 or the silo areas, where 

exposure to uranium was negligible. If the worker is miscategorized with respect to 

his/her work location, the Th-230 body burden, as estimated for Category Type 1 

workers, could be significantly underestimated. 

(2) For Category Type 2 exposures, the proposed methodology to estimate Th-230 intakes 

based on U-238 bioassay is not scientifically valid. It is not possible to estimate U-238 or 

Th-230 intakes based on bioassay results of U-238 in areas where exposures to uranium 

were negligible. 

(3) For Category Type 3 exposures, the assumption that the intake rate of Th-230 can be 

reconstructed based on knowledge of the Ra-226 body burden (as derived using radon 

breath analysis) is valid for the short period of time (1953–1958), when some 13,000 

drums of pitchblende ore raffinate were transferred for disposal in Silos 1 and 2. The 

transfer operations were monitored, and radon breath bioassay data are available upon 

which to determine radium intake. However, there is some question whether workers 

that experienced these exposures can be identified, and whether there are sufficient data 

to construct a coworker model for those workers that might have handled Ra-226 and 

Th-230, but do not have radon breath analyses.1

 

(4) For Category Type 4 exposures, it is not apparent that the ratio of U-238 to Th-230 in the 

source material to which a worker might be exposed is known, nor are the jobs performed 

described in detail. For most jobs involving Silo 3 raffinate stream exposures, U-238 

1

 During the review of this draft, questions were also raised regarding a possible limitation of using radon 

breath analysis to reconstruct Th-230 body burdens, even when the ratio of Ra-226 to Th-230 in the inhaled 

material is known. The reason for this concern is the possibility that Ra-226 is cleared from the body more 

rapidly than Th-230. Hence, radon breath analyses might underestimate the Th-230 body burden under some 

circumstances. NIOSH does not mention how Th-230 intakes should be calculated based on radon in breath 

analysis. 
Draft Review of NIOSH White Paper 7 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

 

concentrations are not significant, and uranium bioassay results cannot be used to derive 

Th-230 intakes. 

Many of these fundamental findings are developed in greater detail in the remaining 

findings. Hence, there is some duplication between these and subsequent findings. 

Finding 2. We have concerns regarding the way jobs, and therefore area assignments, are 

assigned in the white paper. 

Specifically, NIOSH does not offer an explanation of how the jobs were divided between Plant 2 

and Plant 3, and which jobs were done in areas where the workers might have been exposed to 

Th-230 in concentrations above equilibrium. This information is important to understanding 

NIOSH’s comparisons of Appendix A tables of daily weighted activity (DWA)2

 for specific jobs 

in Plant 2/3, Plant 2, and Plant 3. Those comparisons were used by NIOSH to justify an 

equilibrium isotopic ratio of Th-230 to uranium. The following are examples of disconnects 

between job assignments, locations, and categorization of workers as belonging to either 

Category Types 1 or 2 exposures: 

(1) The document by Wing and Halcomb (1958) describes the incorporation of the 

denitration area into Area 3 in 1958. 

(2) An Analytical Data Sheet from May 1957 shows that drumming of Australian 

pitchblendes took place in the Plant 3 Hot Raffinate Area. The general air (GA) and 

breathing zone (BZ) were much higher than the maximum air concentration (MAC). 

There is an observation that some operators did not wear respirators. Did drumming of 

pitchblende occur in Plant 3, as well as in Plant 2? Who were the workers in each area of 

Plant 2 and Plant 3? Did some workers perform jobs in both plants and in different 

areas? 

NIOSH should present a detailed analysis of the jobs and the areas were workers could have 

been exposed to Th-230, and of the most probable isotopic concentration in relation to uranium. 

NIOSH should clarify if workers that performed work in uranium areas might also have worked 

in areas where exposure to uranium was negligible. 

Finding 3. We are concerned with the assumption that there were no exposures in areas 

where processes were contained in closed piping systems. 

For example, pipe leaks were identified in several reports by Wing and Halcomb (1958, 1959), 

Wing et al. (1962) and Ross et al. (1968) on exposures of personnel in Plants 2 and 3. This 

contradicts the presumption in the white paper that exposures in the solvent extraction process of 

Plant 2 were low, because it was a liquid-liquid extraction process essentially contained within a 

closed piping system. In addition, it contradicts the presumption that the high thorium ratio 

observed in the Silo 3 materials is associated with the liquid stream contained within an 

essentially confined system, which presents little if any exposure potential to the workers. 

2

 The terms daily weighted activity (DWA) and daily weighted exposure (DWE) are used interchangeably. 
Draft Review of NIOSH White Paper 8 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

Finding 4. We are concerned that the recycling of raffinate materials could contain high 

concentrations of Th-230 and not the low values assumed in the white paper. 

For example, in some operations in areas of Plant 2/3, workers were exposed to Th-230 in 

concentrations higher than equilibrium in the uranium chain. Due to recycling of raffinate 

material, intakes that are equal to the intake of U-234 or U-238 in natural uranium determined in 

mass units do not appear to be claimant favorable; i.e., they are not bounding for the purpose of 

an SEC evaluation. 

Finding 5. Questions regarding the types of exposures experienced by Plant 8 workers. 

The White Paper states the following: 

A few of the uranium concentrate materials from different mills had chemical 

characteristics which did not allow direct insertion as Plant 2/3 process feed 

streams, i.e., significant organic contaminants were avoided. Plant 8 furnace 

facilities were used to “roast” the concentrates that did not meet specifications 

and drive off volatile chemical contaminants prior to Plant 2/3 processing. In 

these few cases Plant 8 would have ore concentrates with the elevated Th-230 

levels, although these uranium processes would not constitute more than a small 

fraction of the total exposure potential.

The other process streams handled in Plant 8 were scraps and waste products 

from plants which had processed purified uranium products. Thus, though some 

additional Th-230 levels would be expected from handling some out-ofspecification uranium concentrates, they would not add a significant dose 

potential. 

For some operations in Plant 8, intakes that are equal to the intake of U-234 or U-238 in natural 

uranium determined in mass units are not claimant favorable for determining Th-230 intakes. 

Finding 6. Questions regarding exposure assumption for the time period from 1970–1989. 

For the period after 1970, the white paper states the following: 

Following the major process of concentrate feeds in the early to mid 1970s, 

process of uranium feeds shifted to other materials without elevated Th-230 

contaminants. All concentrates (AEC stockpile) were consumed in 1977 and 

other materials, including enriched uranium, became the primary feeds. Hence 

not only the total production but specifically the use of concentrate feeds (with 

elevated Th-230 and daughters) were reduced to less than 10% of previous highs. 

Thus the values in Table 3 should be reduced to 10% as a claimant favorable 

default to account for possible continuing Th-230 exposures. Also, in order to 

account for the fact that internal process equipment and some residual process 

materials that could have Th-230 contaminants existed in the plant the 

assumptions outlined in OTIB-70 (reference 3) were used to demonstrate that 

aging of contaminants reduce the resuspension of those contaminants into 
Draft Review of NIOSH White Paper 9 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

exposure areas to less than 1%, which further validates the reduction of default 

values to 10% as a conservative assumption. 

NIOSH needs to provide the scientific basis to use 10% of the values in Table 3 as a claimantfavorable default. The quantities and type of feed material received by FEMP as a function of 

time is not shown in detail. NIOSH did not show the time spent by workers when exposed to the 

different feed materials, nor their correlation with the time uranium bioassay measurements were 

conducted. NIOSH did not present data on the raffinate treatment for 1970–1989. NIOSH did 

not discriminate which workers were exposed only to raffinates, and which workers were 

exposed to both processes. Furthermore, a reduction in the quantity of material processed cannot 

be assumed to correspond to a reduction in intake by a specific worker, unless the timeframe 

worked by every worker is proportionately reduced. 

Finding 7. Concerns on bounding exposures based on DWAs. 

As SC&A has noted in prior reviews, daily weighted activities (DWAs) reflect typical routine 

exposures (apart from incidents), rather than bounding exposures. In an SEC Petition context, 

air concentration data needs to be analyzed to yield bounding rather than typical dose. See, for 

instance, SC&A’s white paper on use of DWA data for Th-232 exposure estimation at Fernald 

prior to 1968 (SC&A 2009). 

Finding 8. We are concerned that the airborne dust loading of Th-230 in the raffinate 

areas was substantially higher than assumed by NIOSH, and thus a method for dose 

calculations for Th-230 should be available for dose reconstruction in those areas. 

NIOSH’s white paper states the following: 

The workers in the raffinate areas experienced airborne concentrations that were 

consistently at the same levels as were assigned to the records clerks and 

administrative assistants. These levels should be considered ambient levels very 

near the detection limit of the monitoring equipment. The value of 0.1 MAC 

(maximum allowable concentration) or NCG (National Lead Concentration 

Guide) is the same value consistently reported for those areas considered to 

represent background levels. 

SC&A has several concerns with this position, as follows: 

(1) Concerns relative to the uncertainties related to air sampling. 

Air sampling (especially GA samples) can underestimate concentrations in the BZ of a 

worker, often by an order of magnitude (ICRP Pub. 78, 1997). ICRP SG 3 (2002) further 

specifies that the use of static samplers does not ensure a representative measurement of 

exposure of the worker, especially in workplaces where the aerosol release points are 

discrete and distributed. The DWEs were calculated using GA samples and BZ air 

samples. The document by Wing and Halcomb (1958) shows that for 1955–1958, the air 

sampling on the hot raffinate and combined raffinate areas consisted only of GA samples. 

As discussed before, GA samples can dramatically underestimate exposures. 
Draft Review of NIOSH White Paper 10 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

(2) Concerns regarding the completeness of air sampling data. 

The DWA results in Appendix A were not derived using the complete set of results taken 

during the whole year. The following are some of the reasons for this concern: 

 The DWA results in Appendix A were based on sampling during certain months of 

the year. Area 3 DWAs, in 1958 for example, are the ones registered by Wing and 

Halcomb (1958) and were based on August to October sampling. 

 The document by Halcomb and Huesing (1957), “...reports that numerous leaks had 

been observed in the calciner and feed hopper area, but that air dust samples were not 

obtained during the time of these leaks.” 

 The 1962 DWAs in Appendix A were based on the document Wing et al. 1962, and 

cover exposures from January to March 1962. This document shows only GA 

samples taken at the Hot Raffinate Building. On the other hand, the “Analytical Data 

Sheet Document Plant 3 Hot Raffinate, 226Ra and 230Th, and Combined Raffinate, 

230Th Air dust Samples,” 1962, shows BZ air sampling results for an operator 

shoveling solvent cake in Oliver Filter that are higher than the MAC in the Plant 3 

Hot Raffinate Building. The DWAs in Appendix A for 1962, Plant 3, do not show 

these results. 

 An Analytical Data Sheet from May 1955 (“1955 Plant 3 Combined Raffinate BZ and 

GA results Th-230”) reports raw data for GA and BZ samples results in the 

Combined Raffinate area of Plant 3. It shows some results with concentrations above 

the MAC in the control room and for workers operating the batch conveyor at the 

calciner. The DWAs in Appendix A for 1955, Plant 3, do not show these results. 

 An Analytical Data Sheet from May 1957 (“Plant 3 Hot Raffinate Building Air Dust 

Samples,” 1957) shows several GA results above the MAC in Plant 3 Hot Raffinate 

area. Breathing zone samples taken in this area were well above the MAC, for 

example, the result 30,706 dpm/m3

 for an operator using air hoses to unplug the 

loading chute. Several other operations in the same area (hot raffinate area, filtering 

pitchblende residues) showed BZ and GA well above the MAC. Breathing zone 

sample results for Oliver Filter operators were also high. Several GA samples in the 

Oliver Filter area were much higher than the MAC. These data are not reflected in 

Appendix A DWAs for Plant 3. 

The above 5 items are only examples of data and analytical issues that were not taken 

into consideration in the development of the DWA tables in Appendix A, which are used 

in the white paper to demonstrate that exposures experienced by workers in “Plant 3, 

which housed the raffinate operations, were low, essentially at background levels.” The 

DWA tables should summarize all available data, or a justification for not using all the 

available data. 
Draft Review of NIOSH White Paper 11 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

Finding 9. Concerns regarding the methods proposed by NIOSH for calculating bounding 

Th-230 intakes based on uranium bioassay results for Category 2, 3 and 4 areas. 

The white paper states that Th-230 intakes should be based upon a bounding analysis of the 

levels that could have been encountered relative to the levels of uranium present in the given 

work areas. The white paper states that, in the raffinate processing areas, the levels of uranium 

were very low, because uranium had been already extracted. The workers in most raffinate 

operations were essentially not exposed to uranium. Because uranium was not present to any 

significant extent in these areas, it does not appear to be possible to assign thorium intakes using 

uranium bioassay results. 

Finding 10. Concerns regarding the reconstruction of Th-230 related to Silos 1 and 2 (i.e., 

the K-65 Silos). 

From 1953 until 1958, pitchblende ore containing high concentrations of uranium and uranium 

daughter products were used as the raw material for the production of uranium products. This 

ore was obtained from the Shinkolobwe mine in the Belgium Congo. Uranium was separated 

from the pitchblende ore by the use of the three-phase Purex process—digestion, extraction, and 

denitration. The aqueous raffinate or waste from this process was pumped into one of two large 

concrete silos for storage. These residues, which were assigned the code name “K-65,” 

contained small amounts of Th-232 and Th-228, and daughter products of uranium, including 

Th 230, Ra-226, Rn-222, Pb-210, and Po-210. The raffinate was slurried from the refinery 

(Plant 2/3) through pipes into Silo 2. 

The radium-containing material in K-65 Silo 1 came from another source. Prior to 1952, large 

amounts of radium-bearing radioactive waste were shipped to the Fernald Site from Mallinckrodt 

Chemical Works in St. Louis, and eventually stored in the K-65 Silo 1. When the waste material 

first arrived, however, it was placed in metal drums, which were temporarily stored on a concrete 

pad near Plant 1. An internal FMPC memorandum indicates that 13,000 55-gallon drums of 

K-65 material were received at the FMPC during the period September 25, 1951, to July 31, 

1952. Other drums of K-65 material were stored in Plant 8 for long periods of time. The 

drummed material was transferred into Silos 1 and 2 over a 6-year period, between July 1952 

and September 1958. 

The transfer of K-65 waste material from the 13,000 drums was a manual process that likely 

exposed workers internally to high airborne levels of contaminants, as well as externally to 

penetrating radiation (SC&A 2007) 

NIOSH’s White Paper states that: 

During a short period of time (1953–1958) when pitchblende ore raffinates were 

shipped to Fernald from other AEC Sites in some 13,000 drums for disposal in 

Silos 1 & 2, the transfer operations were monitored and radon breath bioassay 

data are available upon which to determine radium intake. By ratioing to Ra-226 

intake it is possible to bound the intakes of the other isotopes that could have been 

part of an unmonitored intake. See the Draft Radon Breath Analysis white paper 
Draft Review of NIOSH White Paper 12 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

(previously distributed to the Working Group) and OTIB-25 for a more complete 

analysis and Dose Reconstruction approach. 

ORAUT-OTIB-0025 (2005) was reviewed and its conceptual basis was approved by 

SC&ANIOSH’s white paper does not specify how Th-230 intakes should be calculated from 

radon breath analysis. 

Additional monitoring results are necessary to calculate Th-230 intakes from any other activities 

related to K-65 silos that are different than the transfer of the 13,000 drums. For any operations 

in which direct contact with these residues was required, the K-65 silos represented a continuing 

internal exposure potential from the unusually high concentrations of Ra-226 and its progeny, 

Pb-210 and Po-210 (these three radionuclides comprise approximately 90% of the total activity 

in the K-65 materials). The uranium daughter Th-230 was also present in significant quantities 

(7% to 10%) in this location. 

An analytical data sheet from 1955 (“Plant 2, K-65 Metal Oxide Storage of Th-230”) describes 

some operations that took place in March 1955 in the K-65 storage material, where the air 

concentrations were much higher than the MAC. 

Finding 11. Concerns regarding Th-230 exposure to workers involved with Silo 3 material. 

Silo 3 was used for the raffinate storage from “cold metal oxide” extraction separations and 

contained approximately 138,000 cubic feet of raffinate. The feedstock for these processes was 

uranium concentrates from a variety of uranium mills in the United States and abroad. The 

material in Silo 3 was calcined prior to storage and was a fully oxidized, fine powder, in contrast 

to the K-65 material in Silos 1 & 2, which was approximately 30% moisture (ORAUT-TKBS0017-5, 2004b). 

ORAUT-TKBS-0017-2 (2004a) cites the inhalation exposures associated with Th-230 in Silo 3, 

as follows: 

The immediate concern involving Silo 3 is the risk of inhalation dose from 

suspended material following a release. The radionuclide having both the largest 

specific activity (60 nCi/gm) and the greatest fraction of relative dose (83%) in 

Silo 3 is Th-230, which is produced from the natural decay of 238U. The primary 

hazard for workers is the inhalation of the fine powder in the silo. ... 

In the SEC Petition Evaluation Report Petition SEC-00046 (2006), it is explained that: 

...the immediate concern involving Silo 3 was the risk of inhalation dose from 

suspended material following a release. Thorium-230, which is produced from 

the natural decay of uranium-238, had the largest specific activity (60 nCi/gm) in 

Silo 3. 

The NIOSH White Paper would benefit from additional discussion regarding the scenarios that 

could have resulted in exposures to workers handling or exposed to material in Silo 3. For 

example, a letter dated March 16, 1956, from [redacted], to Mr. C.L. Karl, Area Manager, 
Draft Review of NIOSH White Paper 13 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

describes a spillage of metal oxide that occurred on January 25, 1956. It states that the Plants 

[redacted] foremen were notified, and that a total of 2,700 pounds of metal oxide had been sent 

to the silo on the third shift. 

We are also concerned that since Silo 3 did not contain uranium in significant quantities, it is not 

apparent how NIOSH can derive Th-230 intakes from uranium bioassay results for workers who 

performed operations related to Silo 3 material. 

3.0 CONCLUSIONS 

 It does not appear to be possible to assign Th-230 bounding intakes based on uranium 

bioassay results to workers that performed their jobs in the raffinate areas of Plant 3 and 

in Silos 1, 2 or 3, where exposures to uranium were insignificant. The DWAs given in 

Appendix A of the White Paper were used to demonstrate that in Plant 3 raffinate areas, 

the exposure levels were low and should be considered ambient levels. NIOSH used the 

DWAs results to justify discarding exposures that occurred in those areas. This 

justification is questionable, because the DWAs in Appendix A of the White Paper are an 

incomplete set of DWAs. Other data on air concentrations taken in the Plant 3 raffinate 

area have shown much higher exposures. In addition, GA measurement results carry 

significant uncertainties in relation to the workers’ real exposures. No data or analyses 

were provided to justify discarding Th-230 exposures in Silos 1, 2 and 3 areas. 

 For workers that performed their jobs in areas of mixed exposure to uranium and uranium 

daughters, it is necessary to know if the workers could have been exposed in the raffinate 

areas and in Silos 1, 2 or 3, as well. Bounding intakes of thorium can only be assigned to 

those workers if there was no job assignment in the raffinate and silos areas. 

 SC&A has concerns on the assignment of thorium intakes that are equal to the intake of 

U-234 or U-238 in natural uranium determined in mass units, based on reviews of DWA 

in Plants 2 and 3 (Period 1953–1970). For workers that performed their jobs only or 

mainly in areas of mixed exposure to uranium and daughters, the DWA data used to 

justify the chosen ratio of Th-230/U-238 concentrations in air are incomplete, and the 

assumption is not claimant favorable. 

 DWA data represent typical, rather than bounding, exposures. NIOSH needs to develop 

bounding exposure values for Th-230 in the SEC context. 

 SC&A has concerns on the assignment of thorium intakes that are equal to 10% of the 

intake of U-234 or U-238 in natural uranium, determined in mass unit, in the period 

1970–1989, for workers that only performed their jobs in areas of mixed exposure to 

uranium and daughters. NIOSH did not present a detailed analysis for this conclusion, 

and there is no scientific calculation to demonstrate the validity of the assigned ratio of 

Th-230/U-238 intakes. 
Draft Review of NIOSH White Paper 14 SC&A – May 6, 2010 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

REFERENCES 

Analytical Data Sheet, 1955. Plant 3, Combined Raffinate BZ and GA Results Th-230. 

Analytical Data Sheet, 1955. Plant 2, K-65 Metal Oxide Storage Th-230. 

Analytical Data Sheet, 1957. Plant 3 Hot Raffinate Building Air Dust Samples. 

Analytical Data Sheet, 1962. Plant 3 Hot Raffinate, 226Ra and 230Th, and Combined Raffinate, 

230Th Air Dust Samples. 

CCC (Catalytic Construction Company) 1956 (date unclear). Combined Raffinate Area and 

Metal Oxide Handling System, Operating Manual for Supervision Personnel, Part IX, Doc. 

Number CCCo 900. 

CCC (Catalytic Construction Company) 1951. Hot Raffinate Treatment Process Design, The 

Engineering Department of Catalytic Construction Company, Philadelphia 2, Pennsylvania. 

(Doc. Number CCCo 222) 

Halcomb, R.N., and J.A. Huesing, 1957. Exposure Study of Plant 3 Personnel to Airborne 

Radioactive Dust, December 31, 1957, SRDB 41029. 

ICRP (International Commission on Radiological Protection) 1997. Individual Monitoring for 

Internal Exposure of Workers. ICRP Publication 78, Annals of the ICRP, Volume 27, Issues 3–

4. 

ICRP (International Commission on Radiological Protection) 2002. Supporting Guidance 3, 

Guide for the Practical Application of the ICRP Human Respiratory Tract Model, Annals of the 

ICRP, Volume 32, Issues 1–2. 

[Redacted] 1956. Letter dated March 16th 1956, from [redacted], to Mr. C.L. Karl, Area 

Manager, U.S. Atomic Energy Commission, Cincinnati, Ohio. 

ORAUT-OTIB-0025. 2005. Estimation of Radium-226 Activity in the Body from Breath Radon222 Measurements, Rev. 00, Oak Ridge Associated Universities Team, Cincinnati, Ohio. 

ORAUT-OTIB-0070. 2008. Dose Reconstruction during Residual Radioactivity Periods of 

Atomic Weapons Employer Facilities, Rev. 00, Oak Ridge Associated Universities Team, 

Cincinnati, Ohio. 

ORAUT-TKBS-0017-2. 2004a. Technical Basis Document for the Fernald Environmental 

Management Project (FEMP) – Site Description, Rev. 00, Oak Ridge Associated Universities 

Team, Cincinnati, Ohio. 

ORAUT-TKBS-0017-5. 2004b. Technical Basis Document for the Fernald Environmental 

Project (FEMP) – Occupational Internal Dose, Rev. 00, Oak Ridge Associated Universities 

Team, Cincinnati, Ohio. 
Draft Review of NIOSH White Paper 15 SC&A – May 6, 2010 

 This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

NOTICE:

Plant 2/3, Institutional History and Exposure Database, produced under the direction of Susan 

Pinney, 1998. 

Ross, K.N., E.D. Leininger, and M.H. Lawrence, 1968. Exposure Study of Plant 2&3 Personnel 

to Airborne Radioactive Dust, SRDB 41063. 

SC&A 2007. Review of the Feed Materials Production Center (FMPC) Special Exposure 

Cohort (SEC) Petition-00046 and the NIOSH SEC Petition Evaluation Report, SCA-SECTASK5-0056, Rev.1. SC&A, Inc. Vienna, Virginia and Saliant, Inc., Jefferson, Maryland. 

SC&A 2009. Draft Review of White Paper on the Use of FMPC DWE Reports for Estimation of 

Chronic Daily Intake Rate for Th-232 Internal Dose Reconstruction. SC&A, Inc., Vienna, 

Virginia, and Saliant, Inc., Jefferson, Maryland. 

SEC Petition Evaluation Report Petition SEC-00046, 2006. 

Rich, Bryce L. and Paul Ruhter, 2010. White Paper on Fernald Th-230 and Other Associated 

Radionuclides, Rev. 7. January 6, 2010. 

Wing, J.F. and R.N. Halcomb, Exposure Study of Plant 3 Personnel to Airborne Radioactive 

Dust, December 4, 1958, SRDB 41050. 

Wing, J.F. and R.N. Halcomb, 1959. Exposure Study of Plant 3 Personnel to Airborne 

Radioactive Dust, December 31, 1959, SRDB 40990. 

Wing, J.F., K.N. Ross, and E.D. Leininger, 1962. Exposure Study of Plant 2&3 Personnel to 

Airborne Radioactive Dust, November 27, 1962, SRDB 41126.