SEC Petition Evaluation Report 

Petition SEC-00103 

Report Rev #: Addendum 2 Report Submittal Date: August 9, 2011 

Subject Expert(s): Mike Mahathy, Robert Morris, Bryce Rich, Leo Faust, Sam Chu, Mel Chew, 

Jason Davis 

Site Expert(s): N/A 

Petition Administrative Summary 

Petition Under Evaluation 

Petition # Petition 

Type 

Petition 

Receipt Date 

Qualification 

Date 

DOE/AWE Facility Name 

SEC-00103 83.13 Nov. 19, 2007 March 4, 2008 Savannah River Site (SRS) 

Class Evaluated by NIOSH 

All construction workers who worked in any thorium area at the Savannah River Site from January 1, 1953 

through December 31, 1972. 

NIOSH-Proposed Class(as) to be Added to the SEC 

All externally monitored employees of the Department of Energy, its predecessor agencies, and their contractors 

and subcontractors who worked at the Savannah River Site from January 1, 1953 through December 31, 1957, 

and whose records have dosimetry codes A, G, CMX, or TNX; and all externally monitored employees of the 

Department of Energy, its predecessor agencies, and their contractors and subcontractors who worked at the 

Savannah River Site from January 1, 1958 through September 30, 1972, and whose records have dosimetry codes 

5A, 5C, 6B through 6Z, 12D through 12H, or 12J through 12Z for a number of work days aggregating at least 250 

work days, occurring either solely under this employment or in combination with work days within the 

parameters established for one or more other classes of employees included in the Special Exposure Cohort. 

Related Petition Summary Information 

SEC Petition Tracking #(s) Petition Type DOE/AWE Facility Name Petition Status 

N/A N/A N/A N/A 

Related Evaluation Report Information 

Report Title DOE/AWE Facility Name 

 SEC Petition Evaluation Report, SEC-00103 

 Addendum to Savannah River Site SEC Petition Evaluation Report 

Savannah River Site (SRS) 

Savannah River Site (SRS) 

ORAU Lead Technical Evaluator: Mike Mahathy ORAU Peer Review Completed By: Daniel Stempfley 

Peer Review Completed By: [Signature on File] 8/9/2011

Timothy Taulbee Date 

[Signature on File] 8/9/2011 SEC Petition Evaluation Reviewed By: 

J. W. Neton Date 

[Signature on File] 8/9/2011 SEC Evaluation Approved By: 

Stuart L. Hinnefeld Date 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Addendum 2 to Savannah River Site (SEC-00103) 

Special Exposure Cohort Evaluation Report
 

NIOSH presented a Special Exposure Cohort (SEC) evaluation report (NIOSH, 2008) regarding the 

Savannah River Site (SRS) to the Advisory Board on Radiation and Worker Health (Advisory Board) 

during the Advisory Board’s meeting held from December 16-18, 2008. In its report, NIOSH 

evaluated the feasibility of reconstructing radiation doses of construction workers who worked in any 

area at SRS during the time period of January 1, 1950 through December 31, 2007. The feasibility of 

reconstructing doses received from thorium exposure from the start-up of thorium operations in 1953 

through 1959 was reserved in the evaluation report while NIOSH continued to evaluate approaches for 

bounding doses from thorium exposures during that time period. 

NIOSH prepared an addendum to the SEC-00103 Evaluation Report (issued May 4, 2010) in which 

NIOSH stated that it can complete dose reconstruction for exposure to all site occupational radiation 

sources for all construction workers who worked in any area at the Savannah River Site during the 

time period from January 1, 1950 through December 31, 2007 (NIOSH, 2010). Since the publication 

of that addendum, NIOSH has continued its research, captured additional information, and determined 

that thorium was used in more locations and operations than had been considered in the 2010 

addendum. Furthermore, NIOSH has determined that it lacks the necessary monitoring data or source 

term data needed to adequately bound internal doses received from exposures to unencapsulated 

thorium for certain workers at SRS. This Addendum 2 to the SEC-00103 Evaluation Report 

documents SRS work performed with thorium, locations where these tasks were performed, exposures 

that may been received from such work, and which exposures cannot be bounded. 

NOTE: This Evaluation Report Addendum 2 only addresses those sections in the Savannah River 

Site Evaluation Report that require discussion; therefore, the section numbering is not contiguous. 

The sections requiring additional thorium discussion begin below. 

Petition Evaluation Report Addendum 2 Summary 

Class Evaluated by NIOSH (in Addendum 2) 

The feasibility of reconstructing doses received from thorium exposure from the start-up of thorium 

operations in 1953 through 1959 was reserved for further consideration in the original SEC-00103 

Evaluation Report. During this subsequent evaluation, NIOSH has determined that thorium 

operations were conducted at SRS through 1972, and conducted in locations beyond those considered 

in the evaluation report (NIOSH, 2008) and the first addendum (NIOSH, 2010); therefore, in 

Addendum 2, NIOSH addresses the feasibility of bounding doses from thorium exposures received 

during the expanded time period from January 1, 1953 through December 31, 1972. Thus, the class 

under evaluation in Addendum 2 is: All construction workers who worked in any thorium area at the 

Savannah River Site from January 1, 1953 through December 31, 1972. 

Addendum 2 addresses thorium operations through 1972 at SRS. The NIOSH research associated 

with this effort has identified a deficiency resulting in the recommendation of a specific thorium class, 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

and the identification of sufficient information and reconstruction methods to support bounding the 

thorium dose for all other workers outside of that proposed class. Although there was still thorium on 

site after 1972, NIOSH has determined a sufficient end point for this thorium evaluation based on 

D&D of 300 Area thorium operations. NIOSH intends to continue reviewing and assessing any 

additional thorium documentation and data obtained for the post-1972 period. The findings of this 

research will be relayed accordingly if the research results require modification of any existing 

conclusions made in the SRS SEC Evaluation Report/Addendums. 

NIOSH-Proposed Class to be added to the SEC 

Based on its full research of the class under evaluation, NIOSH has defined a single class of 

employees for which NIOSH cannot estimate radiation doses with sufficient accuracy. The NIOSHproposed class includes all externally monitored employees of the Department of Energy, its 

predecessor agencies, and their contractors and subcontractors who worked at the Savannah River Site 

from January 1, 1953 through December 31, 1957, and whose records have dosimetry codes A, G, 

CMX, or TNX; and all externally monitored employees of the Department of Energy, its predecessor 

agencies, and their contractors and subcontractors who worked at the Savannah River Site from 

January 1, 1958 through September 30, 1972, and whose records have dosimetry codes 5A, 5C, 6B 

through 6Z, 12D through 12H, or 12J through 12Z for a number of work days aggregating at least 250 

work days, occurring either solely under this employment or in combination with work days within 

the parameters established for one or more other classes of employees included in the Special 

Exposure Cohort. 

The class under evaluation was modified (see Section 3.3 below). The class time period was 

narrowed to 1953 through 1972 because NIOSH has identified a starting point for thorium being on 

site and also determined a sufficient end point for this thorium evaluation based on the D&D of 300 

Area thorium operations. The class locations were restricted to the 700 Area and the CMX/TNX 

facility because unencapsulated thorium was used at those locations and NIOSH lacks sufficient 

documentation to bound potential doses received from thorium exposure at those locations. Class 

location restrictions also include Central Shops because workers assigned to Central Shops could have 

entered the other specified thorium areas to perform maintenance, remodeling, and renovation. 

Potential radiation doses can be bounded for those employees who worked on the SRS site during the 

proposed SEC time period (i.e., January 1, 1953 through September 30, 1972) but who did not work 

in the specified thorium-related locations. Furthermore, the remainder of the class evaluated in the 

original SEC-00103 SRS Evaluation Report is not part of the SEC class proposed by Addendum 2. 

Potential radiation doses received during the period preceding the proposed SEC class (January 1, 

1950 through December 31, 1952) and during the period after the proposed SEC class (October 1, 

1972 through December 31, 2007) can be bounded, as discussed in detail in the SEC-00103 SRS 

Evaluation Report (NIOSH, 2008). 

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SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

Feasibility of Dose Reconstruction 

NIOSH finds it is not feasible to estimate internal exposures with sufficient accuracy for all externally 

monitored employees of the Department of Energy, its predecessor agencies, and their contractors and 

subcontractors who worked at the Savannah River Site from January 1, 1953 through December 31, 

1957, and whose records have dosimetry codes A, G, CMX, or TNX; and all externally monitored 

employees of the Department of Energy, its predecessor agencies, and their contractors and 

subcontractors who worked at the Savannah River Site from January 1, 1958 through September 30, 

1972, and whose records have dosimetry codes 5A, 5C, 6B through 6Z, 12D through 12H, or 12J 

through 12Z. The finding is based on the lack of internal thorium monitoring data or other data or 

methods to support bounding internal thorium doses for SRS workers who may have worked with 

thorium in the designated site areas. With the exception of this class, per EEOICPA and 42 C.F.R. § 

83.13(c) (1), NIOSH has established that it has access to sufficient information to: (1) estimate the 

maximum radiation dose, for every type of cancer for which radiation doses are reconstructed, that 

could have been incurred in plausible circumstances by any member of the class; or (2) estimate 

radiation doses more precisely than an estimate of maximum dose. Information available from the site 

profile and additional resources is sufficient to document or estimate the maximum internal and 

external potential exposure to members of the evaluated class under plausible circumstances during 

the specified period. The specified period includes: January 1, 1950 through December 31, 1952 (the 

period preceding the proposed SEC class); January 1, 1953 through September 30, 1972 (for those 

employees who worked on the SRS site during the proposed SEC class but who did not work in the 

specified thorium-related locations); and October 1, 1972 through December 31, 2007 (the period 

after the proposed SEC class). The entire period originally under evaluation is discussed in detail in 

the SEC-00103 SRS Evaluation Report (NIOSH, 2008). 

The NIOSH dose reconstruction feasibility findings are based on the following: 

	 Principal sources of internal radiation for members of the proposed class included exposures to 

various radionuclides, including thorium in specified SRS locations. Internal exposure pathways 

for workers could have included inhalation and ingestion of the unencapsulated radionuclides 

during fabrication, research and development activities of reactor fuel components, and associated 

chemical separation operations. 

	 Based on NIOSH’s assessment of SRS thorium exposures, there is a lack of sufficient thorium 

personnel and area monitoring data from the onset of thorium operations in 1953 through the end 

of thorium research activities in 1972 (which have been related to the D&D of 300 Area thorium 

operations). The monitoring data deficiency extends only to the work with unencapsulated 

thorium in the 700 Area and CMX/TNX Area on site, and is associated with all externally 

monitored personnel working from January 1, 1953 through December 31, 1957 with dosimetry 

codes A, G, CMX, or TNX; and all externally monitored personnel working from January 1, 1958 

through September 30, 1972 with dosimetry codes 5A, 5C, 6B through 6Z, 12D through 12H, or 

12J through 12Z. NIOSH has identified that it cannot bound, or reconstruct with sufficient 

accuracy, the internal thorium dose for these identified workers at SRS. 

Page 5 of 55 
SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

	 NIOSH finds it is feasible to reconstruct doses received from potential exposures to thorium 

(metal) and its progeny for workers assigned to the 300 Area, SRS reactors, and F and H Canyons. 

	 Principal sources of external radiation for members of the proposed class included exposures to 

various radionuclides at the SRS site. This could have included beta-gamma and neutron 

exposures during fabrication, research and development activities of reactor fuel components, and 

associated chemical separation operations. 

	 NIOSH has determined that it has access to sufficient external monitoring data, and associated 

medical monitoring data, for all personnel during all time periods at SRS. NIOSH has identified 

that it can bound, or reconstruct with sufficient accuracy, the external and occupational medical 

dose for all SRS workers. 

	 Pursuant to 42 C.F.R. § 83.13(c)(1), NIOSH determined that there is insufficient information to 

either: (1) estimate the maximum radiation dose, for every type of cancer for which radiation 

doses are reconstructed, that could have been incurred under plausible circumstances by any 

member of the class; or (2) estimate the radiation doses of members of the class more precisely 

than a maximum dose estimate. 

	 Although NIOSH found that it is not possible to completely reconstruct radiation doses for the 

proposed class, NIOSH intends to use any internal and external monitoring data that may become 

available for an individual claim (and that can be interpreted using existing NIOSH dose 

reconstruction processes or procedures). Therefore, dose reconstructions for all externally 

monitored employees of the Department of Energy, its predecessor agencies, and their contractors 

and subcontractors who worked at the Savannah River Site from January 1, 1953 through 

December 31, 1957, and whose records have dosimetry codes A, G, CMX, or TNX; and all 

externally monitored employees of the Department of Energy, its predecessor agencies, and their 

contractors and subcontractors who worked at the Savannah River Site from January 1, 1958 

through September 30, 1972, and whose records have dosimetry codes 5A, 5C, 6B through 6Z, 

12D through 12H, or 12J through 12Z but who do not qualify for inclusion in the SEC, may be 

performed using these data as appropriate. 

Health Endangerment Determination 

Per EEOICPA and 42 C.F.R. § 83.13(c)(3), a health endangerment determination is required because 

NIOSH has determined that it does not have sufficient information to estimate dose for the members 

of the proposed class working from January 1, 1953 through December 31, 1957 with dosimetry codes 

A, G, CMX, or TNX; and from January 1, 1958 through September 30, 1972 with dosimetry codes 

5A, 5C, 6B through 6Z, 12D through 12H, or 12J through 12Z. 

NIOSH did not identify any evidence supplied by the petitioners or from other resources that would 

establish that the proposed class was exposed to radiation during a discrete incident likely to have 

involved exceptionally high-level exposures. However, evidence indicates that some workers in the 

proposed class may have accumulated substantial chronic exposures through episodic intakes of 

thorium materials. Consequently, NIOSH has determined that health was endangered for those 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

workers covered by this evaluation who were employed for at least 250 aggregated work days either 

solely under their employment or in combination with work days within the parameters established for 

other SEC classes. 

For the periods: January 1, 1950 through December 31, 1952 (the period preceding the proposed SEC 

class); January 1, 1953 through September 30, 1972 (for those employees who worked on the SRS site 

during the proposed SEC class but who did not work in the specified thorium-related locations); and 

October 1, 1972 through December 31, 2007 (the period after the proposed SEC class), a health 

endangerment determination is not required because NIOSH has determined that it has sufficient 

information to estimate dose for the members of the evaluated class. 

3.2 Class Evaluated by NIOSH (in Addendum 2) 

The feasibility of reconstructing doses received from thorium exposure from the start-up of thorium 

operations in 1953 through 1959 was reserved for further consideration in the original SEC-00103 

Evaluation Report. During this subsequent evaluation, NIOSH has determined that thorium 

operations were conducted at SRS through 1972, and conducted in locations beyond those considered 

in the evaluation report (NIOSH, 2008) and the first addendum (NIOSH, 2010); therefore, in 

Addendum 2, NIOSH addresses the feasibility of bounding doses from thorium exposures received 

during the expanded time period from January 1, 1953 through December 31, 1972. Thus, the class 

under evaluation in Addendum 2 is: All construction workers who worked in any thorium area at the 

Savannah River Site from January 1, 1953 through December 31, 1972. 

3.3 NIOSH-Proposed Class to be added to the SEC 

Based on its research of the class under evaluation, NIOSH has defined a single class of employees for 

which NIOSH cannot estimate radiation doses with sufficient accuracy. The NIOSH-proposed class 

to be added to the SEC includes all externally monitored employees of the Department of Energy, its 

predecessor agencies, and their contractors and subcontractors who worked at the Savannah River Site 

from January 1, 1953 through December 31, 1957, and whose records have dosimetry codes A, G, 

CMX, or TNX; and all externally monitored employees of the Department of Energy, its predecessor 

agencies, and their contractors and subcontractors who worked at the Savannah River Site from 

January 1, 1958 through September 30, 1972, and whose records have dosimetry codes 5A, 5C, 6B 

through 6Z, 12D through 12H, or 12J through 12Z for a number of work days aggregating at least 250 

work days, occurring either solely under this employment or in combination with work days within 

the parameters established for one or more other classes of employees included in the Special 

Exposure Cohort. During this period, employees at this facility were involved with fabrication and 

testing of reactor fuel components containing thorium and chemical separation of thorium waste in 

process canyons. 

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SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

4.0 Data Sources Reviewed by NIOSH to Evaluate the Class 

ATTRIBUTION: Section 4.0 and its related subsections were completed by Mike Mahathy, Oak Ridge 

Associated Universities. These conclusions were peer-reviewed by the individuals listed on the cover 

page. The rationales for all conclusions in this document are explained in the associated text. 

NIOSH has obtained additional process data and thorium inventory data for SRS since the initial 

evaluation report was published in November 2008 and the first addendum was published in May 

2010. Some of these data have been considered in the performance of this Addendum 2 evaluation 

and will be cited. NIOSH has also conducted additional interviews of former workers to obtain 

specific information on the use and monitoring of thorium. 

4.3 Facility Employees and Experts 

NIOSH interviewed former SRS employees in order to learn about thorium work, thorium work 

locations, health physics practices, internal and external dosimetry programs, and radiological 

incidents pertinent to thorium use from 1953 through 1972. 

	 Personal Communication, 2011a, Personal Communication with Former Health Physics 

Technician; Telephone Interview by ORAU Team, March 17, 2011, SRDB Ref ID: 93641; 

Follow-up interview, June 15, 2011, SRDB Ref ID: 98144 

	 Personal Communication, 2011b, Personal Communication with Former Health Physics 

Technician; Telephone Interview by ORAU Team, March 17, 2011, SRDB Ref ID: 93642; 

Follow-up interview, June 15, 2011, SRDB Ref ID: 98145 

	 Personal Communication, 2011c, Personal Communication with Former Supervisor of Reactor 

Support Group; Telephone Interview by ORAU Team; April 14, 2011; SRDB Ref ID: 94988 

	 Personal Communication, 2011d, Personal Communication with Former Process Coordinator; 

Telephone Interview by ORAU Team; March 31, 2011; SRDB Ref ID: 95253 

	 Personal Communication, 2011e, Personal Communication with Former Lab Worker and QA 

Employee; Telephone Interview by ORAU Team; March 31, 2011; SRDB Ref ID: 95254 

	 Personal Communication, 2011f, Personal Communication with Former Manager of Plant 

Facilities and Services; Telephone Interview by ORAU Team; May 5, 2011, 2:00 PM; SRDB Ref 

ID: 96050 

	 Personal Communication, 2011g, Personal Communication with Former SRS Employee; 

Telephone Interview by ORAU Team; May 16, 2011, 11:00 AM; SRDB Ref ID: 96343 

Page 8 of 55 
SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

	 Personal Communication, 2011h, Personal Communication with Former SRS Employee; 

Telephone Interview by ORAU Team; June 15, 2011; SRDB Ref ID: 98144 

	 Personal Communication, 2011i, Personal Communication with Former Health Physics 

Technician; Telephone Interview by ORAU Team, June 15, 2011, SRDB Ref ID: 98145 

4.5 NIOSH Site Research Database 

NIOSH has performed additional data captures at SRS since the first addendum was published in May 

2010. As of June 20, 2011, there were 5,225 documents in the Site Research Database (SRDB) 

pertaining to SRS; thus, approximately 1,548 additional documents have been captured, reviewed, and 

uploaded into the SRDB since May 2010. 

SRDB documents evaluated for relevance to the thorium issue include: historical background on 

thorium operations; radiological monitoring data (surface and air concentrations, personnel external 

and internal exposures); information on the radiological controls program; monthly reports; and 

incident documentation. 

The volumes of the History of the Savannah River Laboratory summarize the major activities and 

accomplishments at the Savannah River Laboratory. As appropriate, their thorium summary 

information is excerpted in the following sections and then matched with the plants and/or facilities 

that supported them in order to identify the SRS locations where thorium materials were handled and 

processed. Details regarding the processes and programmatic progress on the production side of the 

site can be gleaned from the periodic progress reports from various departments at the SRS (i.e., 

“Monthly Progress Reports of the Works Technical Department”). 

Another source of thorium information is the Thorium Accountability Ledger, which recorded the 

thorium inventories within the involved SRS facilities from 1952 through 1972 (Thorium Ledger, 

1952-1972; Thorium CEVs, 1955-1962; Thorium JEVs, 1961-1962). The thorium inventory 

information is included in this addendum in order to associate the quantities of thorium materials to 

the R&D and production activities. The Addendum 2 effort also considered the potential exposure 

hazard levels posed by thorium materials in Building 773-A, which were assessed qualitatively in 

Charts of Isotope Hazards (Isotope Charts, 1953-1976). The hazard potential information provides 

perspective on the type of materials that were handled and processed and the nature of the process 

activities at the time. 

NIOSH captured several radiological control notebooks during a data capture performed in June 2011 

(Lab Notes, 1954; Lab Notes, 1955; Lab Notes, 1955-1956; Lab Notes, 1956-1957a; Lab Notes, 1956­

1957b; Lab Notes, 1956-1962; Lab Notes, 1960). 

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SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

5.0 Radiological Operations Relevant to the Class Evaluated by 

NIOSH 

The following subsections summarize SRS radiological operations involving thorium from January 1, 

1953 through December 31, 1972 as well as the information available to NIOSH for characterizing 

particular processes and radioactive source materials. From available resources, NIOSH has gathered 

process and source descriptions, information regarding the identity and quantities of each radionuclide 

of concern, and information describing both the processes through which radiation exposures to 

construction workers may have occurred and the physical environment in which they may have 

occurred. The information NIOSH has included within its initial evaluation report and the report’s 

addendum is intended only to be a summary of the available information. 

Thorium was fabricated into reactor fuel and targets that were irradiated in the production reactors to 

produce U-233 (Personal Communication, 2011d; Personal Communication, 2011f). The U-233 that 

was created in the irradiated thorium fuel was chemically separated and extracted. Although the 

primary goal of the thorium programs was to produce U-233, the chemical process developmental 

work included thorium recovery for reuse. 

The Savannah River Laboratory (SRL), located in the 700 Area, provided necessary research and 

development (R&D) work for the production of U-233 via thorium irradiation (Personal 

Communication, 2011c). The SRL conducted R&D in reactor physics, fuel technology and 

fabrication, and separation process development and improvement. The SRL was also committed to 

solving plant start-up problems, improving production efficiency, developing new production 

processes, and providing analytical control of supplied chemicals, manufacturing processes, and 

finished products. Building 773-A served as the main laboratory of SRL and housed much of the 

process development and experimental research areas. Nearby were the Equipment Engineering 

Laboratory (Building 723-A) and the Waste Disposal Facility (Building 776-A), which handled the 

waste created by the laboratory. The Pile Physics Laboratory (Building 777-M) contained 

experimental reactors used for various lattice and reactivity experiments. 

Two other facilities performed SRL work though they were not located in the 700 Area: CMX and 

TNX, located in Buildings 679-G (also known as 679-T) and 678-G (also known as 678-T), 

respectively. CMX was designed to conduct long-term flow testing of new fuel and target elements 

(Personal Communication, 2011f; Swanson, 2006). TNX was used for determination of operational 

parameters for separations equipment and procedures. Models of SRS reactors to one-sixth scale were 

located in CMX for testing uncharged fuel assemblies (Personal Communication, 2011f). 

Maintenance and craft workers were assigned through Central Shops and may have worked in each of 

these areas, as needed. 

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SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

A February 6, 1952 memorandum described the thorium requirements for research and development 

work to be conducted at the Savannah River Plant (SRP) for calendar year 1952-1953 (Montenyohl, 

1952): 

	 Eleven tons of 0.75” slugs for Critical Experiments for two reactor loading configurations. This 

thorium was requested to be available by June 1953. 

	 Fourteen tons as ingots for Metallurgical Research which included: (1) evaluation of rolling vs. 

extrusion; (2) casting research to provide better ingot quality; (3) determination of impurity limits; 

and (4) alternate methods of fabrication. These ingots were to be supplied at the rate of one ton 

per month for 14 months. 

(1) Evaluation of Rolling vs. Extrusion 

•	 Rolling Investigation 

- Effect on quality of varying the rolling temperature 

- The desirability of salt bath heating vs. air heating 

- Selection of the optimum reduction per pass 

•	 Extrusion Investigation 

- Effect of varying the extrusion temperature 

- Clad extrusions vs. bare extrusion 

- Die materials and contours 

- Reduction ratio 

- The possibility of extruding sponge, without melting and casting to ingot 

(2) Casting Research to Provide Better Ingot Quality 

•	 Top pouring vs. bottom pouring 

•	 The effect of casting temperature 

•	 Mold geometry 

•	 Mold temperature 

•	 Materials of construction 

(3) Determination of Impurity Limits 

•	 As a function of ingot quality (i.e., those which would warrant rejection of the ingot) 

•	 As a limitation to fabrication. Several of the impurities damage the mechanical properties, 

causing “hot shortness,” brittleness, excessive hardness, or splitting on rolling 

•	 As a limitation for irradiation 

•	 As a limitation of separation processes 

(4)Alternate Methods of Fabrication 

•	 Recasting the zinc-thorium biscuits obtained from the reduction operation to a more usable 

shape, then de-zincing and extruding 

•	 Arc melting of thorium 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

The fuel fabrication for the critical experiment would have been done in the Slug Fabrication and 

Process Building (Building 313-M); the irradiation would have been conducted with one of the 

production reactors; and the metallurgical research would have been performed in the metallurgy and 

the metallurgical laboratories of the Main Laboratory (Building 773-A). A note of interest was that 

the memorandum expected delivery of the requested thorium by June 1953. 

In the 1960s, work with thorium was focused on production of U-233 reactor fuel (Personal 

Communication, 2011d). This work involved several campaigns. Tasks were performed in Building 

773A, Building 723-A, M Area, CMX/TNX, multiple SRS reactors, with dissolution in the F and H 

Areas. 

5.1 Savannah River Site Plant and Process Descriptions 

ATTRIBUTION: Section 5.1 and its related subsections were completed by Mike Mahathy, Oak Ridge 

Associated Universities; and Robert Morris, Mel Chew and Associates, Inc. These conclusions were 

peer-reviewed by the individuals listed on the cover page. The rationales for all conclusions in this 

document are explained in the associated text. 

5.1.1 K, L, P, C and R Reactors and Associated Facilities 

Thorium Operations 

In November 1954, 130 low-enriched uranium slugs and 156 thorium slugs were initially weighed and 

measured in the Assembly Area of Building 105-R for test work during L-2 charge. These slugs 

would be returned to the hot laboratory of R or P Areas for final examination when L reactor exposure 

was completed (Progress Report, Nov 1954). These irradiations were completed by December 1954 

(Thorium Ledger, 1952-1972; Thorium CEVs, 1955-1962; Thorium JEVs, 1961-1962). Prior to 

irradiation in the production reactors, the finished slugs and/or fuel elements were sent to the Graphite 

Test Pile in the Slug and Rod Testing Building (305-M) for suitability tests. The 305-M Graphite Test 

Pile was a graphite-moderated zero-power reactor provided primarily for the final assay of reactivity 

of all fuel and target slugs. 

Canned thorium slugs were received from Sylvania Electric Products (SEP) for R-6 and R-7 full-core 

reactor loadings. In 1955, the slugs were irradiated through August; inventories of R-6 and R-7 slugs 

remained at the R and L reactors. In February 1955, two quatrefoils containing striped LMF and 

thorium metal and one quatrefoil containing one channel of all thorium slugs and three channels of 

aluminum spacers were assembled in the Fuel or Rod Assembly and Disassembly (Building 105-L 

Hot Shop) and put in L-3 for an irradiation test in the L Reactor. The quatrefoils containing striped 

LMF and thorium metal were discharged, their fuel column heights measured, and the slugs unloaded 

for visual inspection in the Building 105-L Hot Shop. Inspection of the slugs indicated erosion or 

corrosion marks approximately 0.010-inch deep on the side of the thorium slug cans around the cap 

weld bead (Progress Report, Feb 1955). In September 1955, SRS developed a plan to dispose of the 

unused inventory by stripping the cans and returning the metal to the Feed Materials Production 

Center (FMPC) (Progress Report, Sep 1955). However, thorium ledgers show that a constant level of 

thorium remained at the L reactor through December 1956 and at the R reactor through June 1957 

(Thorium Ledger, 1952-1972; Thorium CEVs, 1955-1962; Thorium JEVs, 1961-1962). 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

In December 1958, ORNL proposed that pellets of mixed 4% enriched UO2 and ThO2 be irradiated at 

SRS. Each pellet was to be 0.26 inches diameter and 3.5 inches long and was to be clad in stainless 

steel, aluminum, or Zircaloy (Progress Report, Dec 1958). It is not known if this occurred; however, 

in June 1959 a procedure was developed and tested for making a final arc weld on aluminum-canned 

hot-press bonded slugs containing powdered and compacted thorium oxide. Ten slugs were welded 

and inspected (Progress Report, Jun 1959). 

In 1960, the AEC requested that SRS produce about 130 kilograms of U-233 via irradiation of 

thorium targets. Sylvania-Corning Nuclear Corporation (Sylcor) prepared a small lot of hollow 

aluminum-clad thorium slugs by a hot-press bonding process at their facility. Sylcor shipped the slugs 

to SRS where there were irradiated. However, when these slugs were dissolved and the uranium was 

recovered and analyzed, SRS determined that the amount of by-product U-232 exceeded the specified 

maximum. The excessive formation of U-232 was attributed to the fast neutron flux that resulted 

from the proximity of the target slugs to the fuel. Accordingly, quatrefoil assemblies containing only 

target slugs were proposed for future irradiations. SRS calculated that this arrangement, which 

provided a separation of several inches from the fuel, would permit sufficient thermalization of the 

neutron flux to reduce the formation of U-232 to an acceptable level. 

In October 1961, SRS authorized Sylcor to extrude and can 600 hollow thorium metal slugs for use in 

the Mark IV fuel (Progress Report, Oct 1961). A plan was also prepared for Sylcor to produce 560 

slugs for use as non-irradiation quality specimens. The Sylcor cladding process was to be qualified by 

destructive examination of slugs at SRS. All of the Sylcor pieces were expected for delivery by 

November 1961 (Progress Report, Oct 1961). Evaluations of thorium slugs that could be used in 

producing U-233 continued through 1963 with some irradiations in L reactor. Through this program, 

eighteen kg of U-233 with 3-5 ppm of U-232 was produced from 20 tons of thorium metal. 

In 1964, the Sylcor core was redesigned to use thorium oxide (ThO2) rather than thorium metal as the 

target material with the final core being a mixed lattice of four uranium fuel assemblies and two 

thorium oxide target assemblies per hex in the controlled zone of the reactor (Du Pont, 1984a). These 

redesigned assemblies were first stored in 1964 at the C, L, and P reactors; irradiation commenced in 

1965. Using the redesigned core, SRS produced one hundred kg U-233 containing less than 5-6 ppm 

U-232 from 56 tons of thorium dioxide (Du Pont, 1984b). 

In addition to the development of uranium fuel elements, some tests of thorium metal were done in 

1964 to evaluate the performance of this material for a thorium/U-233 converter cycle. Two 

thorium-uranium alloy tubes were fabricated and tested in the Heavy Water Components Test reactor 

(HWCTR) to evaluate the performance of thorium tubes under conditions that would be encountered 

in D2O-moderated reactor operating on an equilibrium thorium/U-233 fuel cycle. The tubes reached 

an exposure of about 3,500 MWD/T at peak temperatures of about 485°C (Du Pont, 1984c). 

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To study the behavior of various alloys in natural uranium, segmented metal tubes (SMT) were 

fabricated. Several assemblies were irradiated during 1964; however, inspection showed significant 

vibration damage (Du Pont, 1984c). 

Enriched metal tubes (EMT) were fabricated and irradiated to study the characteristics of slightly 

enriched uranium metal. Fuel from original assemblies, which was housed in stainless steel, was 

discharged from HWCTR after initial irradiation, placed in Zircaloy housings, and recharged into the 

reactor (Du Pont, 1984c). A similar assembly was designed and fabricated to study the characteristics 

of thorium metal. After satisfactory flow testing, two assemblies were charged into HWCTR and 

performed satisfactorily through the final reactor shutdown (Du Pont, 1984c). 

Seventeen different assemblies of test fuel were irradiated in the HWCTR during 1964. Of these, ten 

were tubes of uranium oxide, four were tubes of uranium metal, two were tubes of thorium, and one 

was a CANDU prototype consisting of nineteen rods of uranium oxide (Du Pont, 1984c). 

In 1965, SRS started development work on mixed lattices consisting of various target assemblies 

alternating with high-specific-power, three-tube-driver fuel assemblies. These lattices offered the 

capability of co-producing from the Savannah River reactors almost any variety of products which 

could have been desired. The first of the mixed lattices to go into the plant was the Mark XIIA-Mark 

50A, which was intended to produce U-233 along with lesser amounts of other radioisotope products 

(Du Pont, 1984a). Lattice testing continued through June 1966 with irradiations performed in the L 

reactor (Thorium Ledger, 1952-1972; Thorium CEVs, 1955-1962; Thorium JEVs, 1961-1962). 

Another campaign to produce a minimum of 150 kg U-233 began in K-reactor in June 1967. 

Operation of the four authorized charges (12 target subcycles) continued into 1968 (Du Pont, 1984a). 

The mixed-lattice charge consisted of 261 Mark XIIA fuel assemblies (three-tube drivers), 255 ThO2 

targets, and 84 depleted uranium blanket assemblies. Three thoria target stages (two heavy and one 

light) were irradiated during each driver cycle. Eight of the twelve authorized target subcycles were 

completed during 1967; about 125 kg U-233 with a U-232 concentration of about 7.5 ppm were 

produced (Du Pont, 1984a). Thorium oxide was irradiated in C and K reactors between 1966 and 

1969 as part of the Thorex I and Thorex II campaigns. The Thorex II campaign was completed with 

the recovery of 80 kg of U-233 from thirty-five tons of irradiated ThO2 (Du Pont, 1984b). A final 

thorex campaign was conducted during 1969 with the recovery of 181 kg of U-233 (Du Pont, 1984b). 

Irradiation of thorium oxide was performed in the K reactor. Some thoria materials were stored in the 

K reactor through at least May 1971 (Thorium Ledger, 1952-1972; Thorium CEVs, 1955-1962; 

Thorium JEVs, 1961-1962). 

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A summary of thorium operations at SRS reactors are shown in Table 5-1. NIOSH has not obtained 

documentation on specific thorium operations conducted at reactors from January 1958 through 

December 31, 1959. 

Table 5-1: Thorium Operations at SRS Reactors 

Time Frame Building Operation/Process 

7/1954-12/1955 

105-R Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

105-K Thorium storage 

105-L Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

1/1956-12/1957 

105-R Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

105-K Thorium storage 

105-L Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

1/1960-12/1963 

105-R Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

105-L Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

1/1964-12/1964 HWCTR Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

1/1964-12/1966 

105-L Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

105-P Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

105-K Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

105-C Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

1/1967-12/1968 

105-K Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage 

105-C Thorium storage 

1/1969-5/1971 

105-K Irradiation; non-destructive examination of irradiated thorium 

slugs and rods; thorium targets and fuel storage; thorium storage 

105-L Thorium storage 

105-C Thorium storage 

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The maximum thorium inventories for reactor areas in any month for calendar years 1954 through 

1972 are listed in Table 5-2. While some irradiations were performed in 1960 and 1961, NIOSH has 

not identified documentation to quantify the specific thorium inventories at reactors during those 

years. 

Table 5-2: Maximum Monthly Thorium Inventories at SRS Reactors 

(inventory values in pounds) 

Year C K L P R HWCTR 

1954 ‐ ‐ 500-2000 ‐ 50-500 ‐

1955 ‐ ‐ 2000-10000 50-500 >10000 ‐

1956 ‐ ‐ 2000-10000 ‐ >10000 ‐

1957 ‐ ‐ ‐ ‐ >10000 ‐

1958 ‐ ‐ ‐ ‐ ‐ ‐

1959 ‐ ‐ ‐ ‐ ‐ ‐

1960 ‐ ‐ ‐ ‐ ‐ ‐

1961 ‐ ‐ 50-500 ‐ ‐ ‐

1962 ‐ ‐ 500-200 ‐ ‐ ‐

1963 ‐ ‐ 500-2000 ‐ ‐ ‐

1964 500-2000 >10000 2000-10000 >10000 ‐ 50-500 

1965 >10000 >10000 >10000 2000-10000 ‐ ‐

1966 50-500 2000-10000 2000-10000 ‐ ‐ ‐

1967 >10000 >10000 ‐ 500-2000 ‐ ‐

1968 >10000 >10000 ‐ 500-2000 ‐ ‐

1969 500-2000 500-2000 >10000 ‐ ‐ ‐

1970 ‐ 500-2000 ‐ ‐ ‐ ‐

1971 ‐ 500-2000 ‐ ‐ ‐ ‐

1972 ‐ 500-2000 ‐ ‐ ‐ ‐

Source: Thorium Ledger, 1952-1972; Thorium CEVs, 1955-1962; Thorium JEVs, 1961-1962 

Note: A table cell with a hyphen (-) indicates No Data Available 

5.1.6 300 M-Area Fabrication Facilities 

Thorium operations conducted at the 300-M Area are presented in the first addendum to the 

SEC-00103 Evaluation Report issued May 4, 2010 (NIOSH, 2010). As a result of the research 

conducted since the first addendum, NIOSH has obtained information on additional thorium work 

performed but not previously discussed. Loadings containing varying mixtures of thorium metal and 

thorium oxide were irradiated at Subcritical Experiment (SE), Standard Pile (SP) and the Process 

Development Pile (PDP) (Building 777-M). Testing of thorium oxide intermixed with enriched 

uranium fuel clusters were tested at 777-M for their power evaluation in the HWCTR. Configurations 

of fuel rod clusters were tested at SE, SP and PDP (Du Pont, 1984a). 

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In 1964, SRS installed vibratory-compaction equipment in 313-M to facilitate the production of 

thorium oxide (thoria) slugs. Subsequently, the use of off-site vendors was discontinued. SRS canned 

slugs for L-1 and L-2 charge in 313-M. Additional fabrication work to develop, test, and fabricate 

thorium oxide slugs for thoria targets was performed in the 313-M and 320-M Area from 1964 

through 1970 (Du Pont, 1984a). Excess fuel tubes were chopped in Building 321-M to reclaim and 

consolidate material for use in new tubes. Thorium oxide materials were temporarily stored in 322-M 

awaiting shipment to 321-M during some of this period. 

The quantities of thorium metal slugs handled in the 300-M Area from 1953 through 1964 are 

provided in the first Addendum to the SEC-00103 Evaluation Report, Table 5-1 (NIOSH, 2010) and 

in Table 5-3 of this addendum. NIOSH has since obtained additional information and additional 

source term quantity data from the thorium ledgers. The maximum thorium inventories for 300-M 

Area in any month for calendar years 1953 through 1972 are listed in Table 5-3. 

Table 5-3: Maximum Monthly Thorium Inventories for 300-M Area 

(inventory values in pounds) 

Year 313-M 320-M 321-M/322-M 305-M 777-M 

Reported Inventory 

for M Area 

(# metal slugs) 

(NIOSH, 2010) 

1953 - - - - - 321 

1954 500-2000 2000-10000 - 10-50 2000-10000 1,726 

1955 2000-10000 500-2000 - 2000-10000 >10000 26,618 

1956 2000-10000 0.1-10 - 10-50 >10000 0 

1957 2000-10000 0.1-10 - 10-50 >10000 5,200 

1958 - - - - - 0 

1959 - - - - - 0 

1960 - - - - - 0 

1961 10-50 - 50-500 2000-10000 2000-10000 417 

1962 2000-10000 10-50 50-500 50-500 50-500 14,000 

1963 >10000 - 50-500 10-50 - 16,500 

1964 >10000 - 50-500 10-50 >10000 9,600 

1965 >10000 500-2000 500-2000 500-2000 2000-10000 -

1966 - 50-500 50-500 500-2000 >10000 -

1967 - 500-2000 50-500 - >10000 -

1968 - 500-2000 10-50 50-500 >10000 -

1969 - - 0.1-10 50-500 2000-10000 -

1970 - - 10-50 50-500 2000-10000 -

1971 - - 0.1-10 50-500 2000-10000 -

1972 - - 2000-10000 50-500 2000-10000 -

Source: Thorium Ledger, 1952-1972; Thorium CEVs, 1955-1962; Thorium JEVs, 1961-1962; NIOSH, 2010 

Note: A table cell with a hyphen (-) indicates No Data Available 

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5.1.7 Receiving Basin for Offsite Fuel (RBOF) 

The Receiving Basin for Offsite Fuel (RBOF), located in the H Area near the center of the SRS, was a 

storage pool for research reactor fuels. It became fully operational in 1964. In that same year, 

thorium ledgers show that 182 pounds of thorium material received from 244-H and HWCTR were 

stored at the RBOF. At least 170 pounds of thorium remained there until 1968 (Thorium Ledger, 

1952-1972; Thorium CEVs, 1955-1962; Thorium JEVs, 1961-1962). 

5.1.8 F Canyon 

In 1966, SRS considered the possibility of future U-233 campaigns in which large quantities of thoria 

would be dissolved and processed, requiring high processing rates to reduce the product unit cost. 

The large mixer-settlers in the 200-F Area had demonstrated a potential capacity of six tons of thoria 

per day, which was considered adequate for solvent extraction; however, the dissolving capacity was 

limited to about 0.8 ton per day in the annular dissolver (Du Pont, 1984b). However, NIOSH has not 

found documentation to show that thorium was processed in the F Canyon. 

5.1.11 H Canyon 

Thorium Operations 

Starting in August 1965, U-233 was separated and recovered from irradiated thorium by the Thorex 

process in H canyon. This process consists of six steps: (1) dissolution; (2) acid reduction in the 

dissolver solution, if necessary; (3) co-precipitation (head end) of protactinium with manganese 

dioxide; (4) separation and recovery of thorium and uranium from fission products, protactinium, and 

aluminum by continuous solvent extraction with tributylphosphate; (5) concentration of purified 

thorium nitrate by evaporation; and (6) conversion of recovered U-233 to uranium trioxide. Once 

separated, the U-233 was concentrated and further treated by conversion to oxides suitable for 

shipment or storage in the H-B Line. This Thorex program was conducted through June 1967 as part 

of the Thorex I campaign, and from and 1968 through 1970 as part of the Thorex II campaign (Du 

Pont, 1984b). 

Fifteen tons of thoria (ThO2) had been ordered during 1966 to verify the faster dissolution rate of the 

magnesium oxide (MgO-thoria observed in earlier plant tests at TNX. This MgO-thoria did not have 

the large particles found in the 600-lb pilot lots of thoria that had been produced previously. Even 

though the packing density was low, the MgO-thoria was irradiated with dissolution testing conducted 

in the H canyon (Du Pont, 1984b). 

Residual activities and shipment of thorium from the H area to Fernald began in 1971 and was 

completed in May 1972. 

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The maximum thorium inventories for the H Area in any month for calendar years 1965 through 1972 

are listed in Table 5-4. 

Table 5-4: Maximum Monthly Thorium Inventories at H Area 

Year Pounds 

1965 >10000 

1966 >10000 

1967 >10000 

1968 >10000 

1969 >10000 

1970 >10000 

1971 >10000 

1972 >10000 

Source: Thorium Ledger, 1952-1972; Thorium CEVs, 1955-1962; Thorium JEVs, 1961-1962 

5.1.12 Old HB Line 

Thorium operations conducted in the HB line are discussed in Section 5.1.11 above. 

5.1.15 Building 235-F Plutonium Fuel Fabrication Facility (PUFF) 

Thorium Operations 

From at least 1961 through 1965, the SRS Works Technical Division operated a portion of Building 

235-F for work with thorium oxide. The largest quantity of thorium oxide present in 235-F in any of 

these months was 500 pounds (Thorium Ledger, 1952-1972; Thorium CEVs, 1955-1962; Thorium 

JEVs, 1961-1962). 

5.1.16 Savannah River Laboratory (SRL) 

Thorium Operations 

Thorium work at SRL was assessed using SRS thorium ledger data, interviews with former SRS staff, 

and documents available in the SRDB. 

In mid-1953, the Laboratory had started to accumulate a thorium inventory on the order of tons; the 

inventory steadily increased over the next year and a half to about five tons. It is reasonable to assume 

that the tons of thorium at the Laboratory were used for the metallurgical research requested by the 

1952 memorandum (Montenyohl, 1952) in support of the fuel and target development work. The 

layout of Building 773-A is shown in Figure 5-1. 

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Source: Du Pont, 1957 

Figure 5-1: Building 773-A, SRS Main Technical Laboratory Building 

Section 1-A: The front wing of Building 773-A, which contains the administrative and technical services, 

the change area, and "cold" laboratories. 

Sections 1-B and 1-C: The main central portion with laboratory modules were located back-to-back but 

separated by a utility corridor and flanked on the outside walls by auxiliary modules and personnel corridors. 

Both of these sections were equipped to handle radioactive materials. 

Section 2: Physical property and corrosion testing, metallographic and x-ray diffraction studies, and general 

physical and chemical studies were conducted in support of the reactor fuel development program. 

Part II (Caves): Contained facilities for physical, chemical, and metallurgical work with high-level 

radioactive materials. By October 1954, a variety of cave apparatus was available, including: dimensioning 

equipment, contour tracing gauge, weighing scales, analytical balances, binocular periscope, a stage cut-off 

machine for sectioning irradiated metal, chemical apparatus for dissolving fuel elements, and hardness 

testers. 

Part III, Main Technical Laboratory Metallurgical Extension: Increased space for the Metallurgical Section 

of the Technical Division. It housed equipment required for the development of new fuel elements. It was 

divided into the element fabrication area, electroplating and cleaning area, tube-cleaning area, vertical 

assembly area, nondestructive testing area, machine shop, and storage area. Mock-ups of fuel assemblies 

were made in this area. 

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The CMX/TNX facilities (also referred to as Semiworks) were not located in the 700 Area nor were 

they always part of SRL. Both were located in the T Area (also referred to as CMX/TNX area and the 

600 Area). However, discussion of thorium operations at CMX/TNX has been included in this 

subsection because SRL technical staff were involved in research and development activities 

conducted there. CMX was constructed in 1951 with the initial mission of performing loop-testing of 

water as part of researching of SRS reactor cooling. CMX’s original scope called for no use of 

radioactive materials. CMX was also used as the first office of SRS Health Physics. TNX was placed 

in operation in 1951 with the initial mission of refining the PUREX process and other processes of the 

large-scale separation process used for separating plutonium and uranium in the 200 Area. In the 

years that followed, operations at both facilities were expanded to address new issues related to 

reactors and separations technology. A recent aerial view of the Semiworks is shown in Figure 5-2 

(Swanson, 2006). 

Source: Swanson, 2006 

Figure 5-2: Aerial View of SRS Semiworks (CMX/TNX) 

In 1953, Savannah River was requested to produce limited quantities of U-233 by thorium irradiation. 

The slug geometry was chosen for initial development of enriched uranium-aluminum alloy fuel and 

metallic thorium target elements. The R&D efforts were underway to: (1) produce and encapsulate 

[can] thorium metal slugs for the inclusion in reactor fuel rods and targets and subsequent irradiation 

in the reactors; (2) start development work to provide basic data on chemical processes for the 

separation of U-233 from irradiated thorium and for the recovery of thorium for reuse; and (3) 

evaluate the physics parameters of reactor loadings of enriched uranium-aluminum alloy fuel slugs 

intermixed with thorium target slugs (Du Pont, 1984a). 

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The slug geometry was chosen for initial development of enriched uranium-aluminum alloy fuel and 

metallic thorium target elements for the U-233 program. For the fuel assembly design, the initial 

emphasis was placed on the development of an assembly comprising a fuel tube that contained a 

column of solid thorium slugs. Because of increasing interest in U-233, more efficient fuel assembly 

design was investigated by the SRL. The investigation found that a more efficient fuel assembly 

design can be achieved by replacing the solid thorium slugs with hollow slugs (Du Pont, 1984a). 

SRL participated in research and testing of two processes to can thorium slugs: AlSi bath at different 

temperatures and hot die-size bonding. Some cans were removed to study interface wetting (Progress 

Report, Jul 1954; Progress Report, Aug 1954; Progress Report, Oct 1954; Progress Report, Nov 1954; 

Progress Report, Dec 1954). The AlSi canning was found to produce a hard, brittle layer between the 

thorium and the AlSi that interfered with the subsequent separations process. Hot die-size bonded 

slugs did not have the deleterious layer formed by the AISi, and they allowed superior bond strength 

and resistance to thermal shock. Therefore, the hot die-size bonded process was selected for future 

production use (Du Pont, 1984a). In December 1954, a total of 1,166 hot die-size bonded thorium 

slugs, about 6-1/2 inches in length and 1.085 inches in diameter, were received at SRL from Sylvania 

Electric Products Company. SRL performed other work to refine the thorium canning process. For 

example, the mechanical properties of irradiated thorium were studied (i.e., stress responses that could 

counteract the canning process). These stress tests were performed in the machine shop portion of the 

Metallurgical Lab (in Section II) without hood ventilation (Personal Communication, 2011e). Other 

such work, such as etching of the can cladding, was performed in Building 773 hot cells (Personal 

Communication, 2011e). 

NIOSH has found limited documentation on the receipt and transfer of individual shipments of 

thorium at the SRL; however, one document shows that nine wooden boxes of thorium were received 

from National Lead of Ohio and delivered to Building 773A (Log Sheets, 1955). At about that time, 

development work was started to provide basic data on chemical processes for the separation of U-233 

from irradiated thorium and for the recovery of thorium for reuse. Bench-scale research was 

performed in Building 773A in glove boxes; however, up to 1 kg of thorium was dissolved during 

these experiments (Personal Communication, 2011d). Thorium slugs were cut in a cut-off machine in 

one of the high-level caves and also in junior caves in 773-A in 1955. These cut pieces were then 

dissolved with small aliquots sent to B-103 for analysis (Slug, 1955). Uranium recovery equipment 

including an ion exchanger for the concentration of U-235 and a prototype critically-safe dissolver (of 

the ORNL "trickle type") were installed at TNX (Building 678-G). During late 1955, some of the 

development work on the recovery of U-235 was moved to ORNL in order to concentrate the SRL 

effort on U-233 production from irradiated thorium (Du Pont, 1984b). A workable process was 

developed that was very similar to the PUREX process and which used 30% tributylphosphate solvent 

for extraction. The process entailed: (1) dissolving the irradiated metal with nitric acid containing a 

hydrofluoric acid catalyst; (2) head-end scavenging with manganese dioxide to clarify and to begin the 

decontamination of the dissolver solution; and (3) solvent extracting of thorium and uranium to 

separate them from fission products and protactinium, and subsequently, from each other. Problems 

of particular concern were the corrosion of the dissolver and the adequate separation of thorium from 

the fission products and protactinium (Du Pont, 1984b). 

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Work performed in both Building 773A and TNX resulted in a method that appeared to be feasible for 

producing thorium metal by electrolytic reduction of thorium oxides in a molten salt bath. The best 

system studied was thorium oxide in potassium thorium fluoride (KThF5), which was quite similar to 

the Hall Process for the production of aluminum by the electrolysis of aluminum oxide in cryolite (Du 

Pont, 1984b). SRL used both metal and oxide forms of thorium in this early time period. 

Physics parameters of reactor loadings of enriched uranium-aluminum alloy fuel slugs intermixed 

with thorium target slugs from experiments done in the Subcritical Experiment (SE) and the Process 

Development Pile (PDP) (Building 777-M) were determined in the intermediate and high-level caves 

at Building 773-A (Du Pont, 1984a). Thorium oxide dummy slugs prepared by the University of 

California Radiation Laboratory were used in test irradiations as surrogates for irradiation of 

neptunium slugs. SRL removed welds from these thorium oxide slugs and fitted new end caps 

(Dummy Slugs, 1958). Starting in early 1959, thorium was used as a surrogate for neptunium in 

recovery and separation process development conducted in the Building 773-A, and later, in pilot 

plant tests in the TNX. A test involving two consecutive loading and elution operations was 

performed at TNX in August 1960 as part of a test of equipment used to separate neptunium from the 

PUREX high-activity waste. The test showed that the anion exchange column also had excellent 

thorium absorption characteristics (Progress Report, Aug 1960). 

Development work on hot die-size bonding continued through 1963, with the objective of reducing 

the cost of the fuel canning, particularly the cost of hot die-size bonding the inner Mark VB tubes in 

cans with integral ribs (Du Pont, 1984a). Building 774-A was a hot die size bonding facility equipped 

with a high-pressure autoclave, centrifugal extractors, and a miniature centrifugal extractor facility 

(Du Pont, 1984d). 

Development work on U-233 production performed in 1962 centered on the Mark VIB-VIIIT lattice. 

The U-232 contamination considered permissible at that time was on the order of 50 ppm. In 1963, 

theoretical studies were initiated to examine various methods of producing U-233 with U-232 contents 

ranging from 10 ppm down to less than 1 ppm. These studies were intended to define the mode of 

operation, cost, and required modification in the reactor, fuel fabrication, and separation areas (Du 

Pont, 1984a). A general study was made of the production of high-purity U-233 low in U-232 

content. Fabrication and testing was performed in the Metallurgical Laboratory (aka Fabrication 

Laboratory) and the high-level caves at Building 773-A (Personal Communication, 2011c). 

Subsequently, a charge was designed and a program formulated to produce 100 kg of U-233 at 5 to 6 

ppm U-232. For this study, ThO2, rather than thorium metal, was chosen as target material and the 

final core design was a mixed lattice of four uranium fuel assemblies and two thorium oxide target 

assemblies per hex in the controlled zone of the reactor (Du Pont, 1984a). Material and fabrication 

development were required for the thorium targets. ThO2 used in the development programs was 

produced by Mallinckrodt Chemical Works in a cooperative program aimed at developing 

specifications that could be used to obtain ThO2 from a commercial supplier (Du Pont, 1984a). 

In 1964, Procedures were developed by the Laboratory for processing irradiated thorium and thorium 

dioxide to separate U-233 and recover thorium for recycle. These procedures would be applied to two 

irradiation programs in progress: (1) 18 kg of U-233 with 3-5 ppm of U-232 was to be produced from 

20 tons of thorium metal; (2) 100 kg U-233 containing less than 65 ppm U-232 was to be produced 

from 56 tons of thorium dioxide (Du Pont, 1984b). 

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SRL conducted laboratory studies of the dissolution of "sol gel" thorium oxide, a dissolvent consisting 

of nitric acid and hydrogen fluoride. Optimum dissolving rates were produced in 1964. However, 

these rates were sufficient for plant scale use only if moderate agitation was applied (e.g., vigorous 

boiling obtained by strongly heating the bottom of the vessel). This dissolvent solution attacked 

aluminum fast enough to de-clad the thoria in 10 to 15 hours, which made a separate de-cladding step 

unnecessary (Du Pont, 1984b). Laboratory tests were made of a number of materials for the “head 

end” co-precipitation and removal of Pa-233 from the acid-adjusted Thorex dissolver solution. This 

step was necessary to decontaminate thorium and U-233 from protactinium, and was desirable for the 

production of U-233 free from U-232. Carrying agents tested included gelatin, niobium pentoxide, 

zirconium phosphate, thorium phosphate, thorium iodate, and manganese dioxide. Of these, 

manganese dioxide (MnO2) produced the best results. While the resulting cake was sensitive to 

radiation, tests with actual dissolver solutions showed that the cake could be centrifuged and separated 

under process conditions without appreciable loss of protactinium (Du Pont, 1984b). Tests with 

aluminum-canned thorium dioxide in the 6-foot-diameter dissolver at TNX demonstrated that the 

processing capacity of the H Area for the U-233 separations campaign could be increased from 1,000 

to 3,000 lb of thorium per day by installing horizontal heating coils at the bottom of the dissolver. 

Installation of the horizontal coils in an “extra machinery” dissolver was recommended (Du Pont, 

1984b). 

In 1964, all the equipment for one of the cells in the intermediate level caves at Building 773-A were 

redesigned, rebuilt, and replaced for use with the Thorex Process (Du Pont, 1984d). Additional pilot 

plant testing carried out at TNX with simulated aqueous waste from a first cycle extraction in the 

thorium process showed that the neutralized waste could be transferred through the plant waste header 

by gravity flow if it is diluted to a final volume five times the volume of the original acidic waste 

stream. If the volume resulting from this dilution was considered excessive for plant operation, the 

acidic waste could be transferred to the pump tank in Building 241-H for neutralization before the 

waste was pumped to a waste storage tank. Further tests showed that it was not necessary to flush the 

waste header after each gravity flow transfer of the diluted neutralized waste. Plant waste from the 

processing of irradiated thorium was successfully transferred to the waste tanks for storage (Du Pont, 

1984b). 

During the first half of 1964, the Experimental Physics Division conducted a number of studies in 

support of the power reactor evaluations performed at SRL and Oak Ridge. A program on thorium 

use in D2O reactors was pursued on an off-and-on basis due to changing program authorizations. A 

set of ThO2-U-235 fuel assemblies was procured from the Argonne National Laboratory, and the 

necessary hardware was designed and fabricated for testing this fuel in rod clusters in the SE and PDP. 

Negotiations were also underway with Nuclear Metals, Inc., to obtain fabricated thorium metal/U-235 

fuel assemblies for possible use in a cooperative program with the Babcock and Wilcox Company. 

Other work included the development of measurement techniques for determining thorium fast 

fissions and the production of U-232 from Th-232 captures (Du Pont, 1984c). 

In addition to the development of uranium fuel elements, a limited number of tests of thorium metal 

were undertaken to evaluate the performance of this material for a thorium/U-233 converter cycle. 

Two thorium-uranium alloy tubes were constructed in the Fabrication Laboratory and tested in the 

HWCTR to evaluate the performance of thorium tubes under conditions that would be encountered in 

Page 24 of 55 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

a D2O-moderated reactor operating on an equilibrium thorium/U-233 fuel cycle. These tubes reached 

an exposure of about 3,500 MWD/T at peak temperatures of about 485°C (Du Pont, 1984c). 

To study the behavior of various alloys in natural uranium, segmented metal tubes (SMT) were 

constructed in the Fabrication Laboratory. Several assemblies were irradiated during 1964; however, 

inspection showed significant vibration damage. Similar damage also occurred during extended flow 

testing in the Power Flow Loop (Du Pont, 1984c). Enriched metal tubes (EMT) were fabricated and 

irradiated to study the characteristics of slightly enriched uranium metal. Fuel from original 

assemblies, which was housed in stainless steel, was discharged from HWCTR after initial irradiation, 

placed in Zircaloy housings, and recharged into the reactor (Du Pont, 1984c). 

The handling of large quantities of short-cooled thorium oxide (ThO2) and uranium oxide (UO2) 

caused radiation problems in high level caves. Relatively large quantities of curium were extensively 

handled throughout the laboratory with excellent contamination control but with some exposure 

problems (Du Pont, 1984d). The procedures for processing irradiated thorium and thorium dioxide 

(thoria) to separate U-233 and recover thorium for recycle were demonstrated in the laboratory, tested 

at TNX, and successfully applied to two plant irradiation programs (Du Pont, 1984b). 

In 1965, SRL provided further and extensive technical support for the thorium program (Du Pont, 

1984b). A Thorex-type process compatible with existing process equipment in H Area was developed 

for processing irradiated thorium and thorium dioxide to separate U-233 and to recover thorium for 

recycle. After dissolution of the irradiated thorium, the product solution required a sorption or “headend” treatment in which most of the Pa-233 and some of the fission products were co-precipitated 

with manganese dioxide to separate them from U-233 and thorium. Bench-scale testing was 

performed in Building 773-A. Prototype testing was performed at TNX (Du Pont, 1984b). The TNX 

laboratory reported analyzing 6241 samples in 1965, an increase of 9.1% over the 5,718 reported in 

1964 (Du Pont, 1984d). 

In 1967, process development for thoria slug canning continued with analytical and metallurgical 

support being performed in Building 773-A. Other analytical support provided by SRL in 1967-68 at 

Building 773-A included thermogravimetric analysis and in-line mass spectrometry of released gas 

(Du Pont, 1984b). Pilot scale tests to support Thorex programs were conducted at TNX through 1968 

(Du Pont, 1984b). 

In 1968, compaction of mixed powders for co-extrusion billet cores was investigated. Evaluation of 

tubes made with compacted cores using several grades of U3O8, UO2, ThO2, and Al powders was 

completed (Du Pont, 1984a). Work may have been performed in Buildings 723-A,-773-A, and TNX. 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

One of the Thorex campaigns, Thorex IIB, was completed with the recovery of 181 kg of U-233. 

About 2.65 g of Pa-231 resulting from the decay of Th-232 in a former Thorex campaign was also 

recovered and purified (Du Pont, 1984b). SRL provided support to the Thorex program through 1970. 

NIOSH has not found documentation on processes and operations that may have involved thorium in 

Building 773-A in 1971 though inventory ledgers show that there were residual thorium processing 

and handling activities occurring during this time (Thorium Ledger, 1952-1972; Thorium CEVs, 

1955-1962; Thorium JEVs, 1961-1962). 

A summary of thorium operations in the 700 Area is shown in Table 5-5 (Progress Report, Aug 1960; 

Du Pont, 1957; Du Pont, 1984d; Du Pont, 1984b; Du Pont, 1984c; Swanson, 2006). 

Table 5-5: Thorium Operations in SRS 700 Area 

(This table spans two pages) 

Time Frame Building Operation/Process 

7/1953-12/1955 773-A 

Metallurgical research; fabrication; analytical control of supplied materials, 

manufacturing processes and finished products; research to find more efficient fuel 

design (hollow slugs); cut irradiated slugs underwater. Thorex process development 

work including: (1) dissolution, (2) head-end decontamination of dissolver solution, and 

(3) solvent extraction 

CMX Flow testing of new fuel and target elements 

TNX Testing of non-charged fuel assemblies; determination of operational parameters for 

separations equipment and procedures 

1/1956-12/1957 773-A Analytical control of supplied materials, manufacturing processes and finished products; 

slug fabrication; continued research of Thorex process 

CMX Flow testing of new fuel and target elements 

TNX Testing of non-charged fuel assemblies; determination of operational parameters for 

separations equipment and procedures 

1/1958-12/1959 773-A Analytical control of supplied materials, manufacturing processes and finished products; 

thorium used as surrogate for neptunium recovery and separation process development 

TNX Testing of non-charged fuel assemblies; determination of operational parameters for 

separations equipment and procedures 

1/1960-12/1960 773-A Dissolved Sylcor slugs, recovered some U-233 

TNX Testing of non-charged fuel assemblies; pilot-scale development of Thorex process 

1/1961-12/1961 773-A 

Analytical control of supplied materials, manufacturing processes and finished products; 

dissolving Sylcor slugs, recovering some U-233; destructive testing of slug welds; waste 

collected from high level caves, encased in concrete, and sent to 643-G 

TNX Testing of non-charged fuel assemblies 

1/1962-12/1962 773-A Analytical control of supplied materials, manufacturing processes and finished products 

TNX Testing of non-charged fuel assemblies; pilot-scale development of Thorex process 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Table 5-5: Thorium Operations in SRS 700 Area 

(This table spans two pages) 

Time Frame Building Operation/Process 

1/1963-12/1966 773-A 

Analytical control of supplied materials, manufacturing processes and finished products; 

development work on “hot die-size bonding” process; material development for thoria 

targets; laboratory studies of the dissolution of “sol gel” thorium oxide; support for 

Thorex process for the recovery of U-233 in the 200 Area (Building 221-H); handle 

large quantities of short-cooled ThO2 and UO2 (gram quantities were handled in 

Intermediate Level Cells and up to 250 mg were routinely handled in glove boxes in 

Separations Chemistry); Cell 1 of the Intermediate Level Cells redesigned, rebuilt, and 

replaced for use with the Thorex process; assay irradiated thorium targets in both metal 

and oxide form; test various materials for the “head end” co-precipitation and removal of 

Pa-233 from the acid-adjusted Thorex dissolver solution 

CMX Flow testing of new fuel and target elements 

TNX Testing of non-charged fuel assemblies; pilot-scale development of Thorex process 

1/1967-12/1969 773-A 

Analytical control of supplied materials, manufacturing processes and finished products; 

laboratory studies of the dissolution of “sol gel” thorium oxide; support Thorex process 

(Thorex I, IIA and IIB) for the recovery of U-233 in the 200 Area (Building 221-H); 

Handle large quantities of short-cooled ThO2 and UO2 (gram quantities were handled in 

Intermediate Level Cells and up to 250 mg were routinely handled in glove boxes in 

Separations Chemistry); assay irradiated thorium targets in both metal and oxide form; 

Removal of thorium from building 

CMX Flow testing of new fuel and target elements 

TNX Pilot-scale development of Thorex process 

1/1970-12/1972 773-A Removal of any remaining thorium 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

The maximum thorium inventories in any month for calendar years 1953 through 1972 for 700 Area 

buildings (as recorded on ledger sheets) are listed in Table 5-6. Inventories for Buildings 723-A are 

included, although NIOSH has obtained no documentation on the processes in which these inventories 

were employed. 

Table 5-6: Maximum Monthly Thorium Inventories, SRS 700 Area 

(inventory values in pounds) 

Year 773-A 723-A CMX TNX 

1953 500-2000 - - -

1954 2000-10000 - 50-500 500-2000 

1955 >10000 - 50-500 2000-10000 

1956 2000-10000 - - 2000-10000 

1957 2000-10000 - - -

1958 - - - -

1959 - - - -

1960 50-500 10-50 - -

1961 50-500 10-50 50-500 -

1962 50-500 10-50 - -

1963 - 0.1-10 - -

1964 2000-10000 0.1-10 500-2000 >10000 

1965 2000-10000 10-50 10-50 >10000 

1966 2000-10000 10-50 500-2000 >10000 

1967 500-2000 50-500 500-2000 >10000 

1968 500-2000 0.1-10 500-2000 >10000 

1969 500-2000 0.1-10 - -

1970 500-2000 - - -

1971 500-2000 - - -

1972 - - - -

Source: Thorium Ledger, 1952-1972; Thorium CEVs, 1955-1962; Thorium JEVs, 1961-1962 

Note: A table cell with a hyphen (-) indicates No Data Available 

Page 28 of 55 
SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

6.0 Pedigree of Savannah River Site Data 

The following statements apply to the thorium exposure analysis in this SEC Evaluation Report 

Addendum 2: 

	 All air monitoring data used in this analysis came from official SRS primary source documents 

(i.e., handwritten logs) obtained during NIOSH data captures. 

	 Thorium bioassay data used in this evaluation came from official SRS bioassay record books. 

Uranium bioassay data recorded in the record books through 1965 were entered into spreadsheets 

for use in the statistical analyses. 

	 Thorium inventories used in this evaluation were recorded in SRS thorium inventory ledgers. 

	 Work locations specified in the proposed SEC class were derived from external dosimetry codes 

that indicate where dosimeters were issued. Use of the code set published in this addendum 

ceased on September 30, 1972; a new set of codes were implemented on October 1, 1972. The 

codes were used to limit entry to the 700 Area regulated areas and the CMX/TNX regulated areas. 

While it was possible for someone from another area to have picked up a badge and gone to the 

700 Area and/or the CMX/TNX regulated areas, it is not feasible that they would have worked 250 

days there without ever having a dosimeter code from that area. Most SRS workers were 

monitored for external radiation and therefore have a dosimeter code location. In fact, based on 

the NOCTS claims to date, 80% of SRS claimants have some external monitoring records during 

their SRS employment. The remaining 20% are a mix of clerical staff, cafeteria staff, coal power 

plant operators, and construction trades workers. The construction trades workers who were not 

monitored did not enter a regulated area and were typically involved in new construction 

activities. 

	 Information given in thorium ledger documents (Thorium Ledger, 1952-1972) were entered into 

Microsoft Excel spreadsheet files before being assessed for inclusion in this addendum to the 

evaluation report. Additional thorium inventory data for 1959 through 1962 are available 

(Thorium CEVs, 1955-1962; Thorium JEVs, 1961-1962). 

	 All other documents and data used in this analysis were addressed in the original data pedigree 

analysis provided in SEC Petition Evaluation Report for Savannah River Site (NIOSH, 2008). 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

7.1 Evaluation of Bounding Internal Radiation Doses at Savannah River Site 

ATTRIBUTION: Section 7.1 and its related subsections were completed by Mike Mahathy, Oak Ridge 

Associated Universities; Sam Chu, Mel Chew and Associates, Inc.; Billy Smith, Mel Chew and 

Associates, Inc.; Robert Morris, Mel Chew and Associates, Inc; and Elizabeth Brackett, MJW 

Corporation. These conclusions were peer-reviewed by the individuals listed on the cover page. The 

rationales for all conclusions in this document are explained in the associated text. 

In its SRS evaluation report (NIOSH, 2008), NIOSH reserved for future consideration the feasibility 

determination for thorium exposures from January 1, 1950 through December 31, 1959. Since the 

publication of that SRS report, NIOSH has evaluated and quantified thorium operations conducted at 

SRS from 1950 through 1959. During that evaluation, NIOSH determined that the period of thorium 

metal work for which a common feasibility decision should be applied extended through 1965. 

NIOSH published that evaluation in 2010 (NIOSH, 2010). Subsequently, NIOSH conducted 

additional document captures and interviews with former SRS workers, further extending its 

evaluation of SRS thorium work through 1972. This section provides further discussion of thorium 

operations by SRS area and discusses the feasibility of bounding thorium doses in each of those areas. 

7.1.1.8 Thorium (Th-228, Th-232) 

300 Area 

In the first Addendum to the SEC-00103 Evaluation Report, NIOSH stated that under the conditions 

of use of natural thorium metal at SRS for the period 1953 through 1965, uranium bioassay data can 

be used to support thorium intake modeling. In order to demonstrate how thorium operations 

compared to uranium operations, NIOSH analyzed air monitoring data (results in mass) obtained 

during sampling of thorium and uranium work performed on the same days in the 300 Area. Further, 

NIOSH tested the hypothesis that the mean of the natural log of the mass air concentrations of thorium 

was less than or equal to the mean of the natural log of the mass air concentrations obtained for 

uranium. The hypothesis could not be rejected (NIOSH, 2010). 

After publication of first Addendum to the SEC-00103 Evaluation Report, a critique of the air 

concentration statistical test stated that NIOSH matched thorium sample results to uranium sample 

results based on date, but should assess the comparison based on similar operations between thorium 

and uranium. The critique postulated that the selected uranium results may have represented 

processes that did not have the same potential for airborne contamination as did the selected thorium 

operations. To address the critique NIOSH re-performed its original analysis selecting uranium and 

thorium results based on comparable operations (e.g., lathing). For this latter analysis, NIOSH has 

eliminated one of the thirty thorium results used in the original statistical analysis published in the 

addendum. NIOSH selected thirty-two uranium results taken during cutting, lathing, machining, and 

drill operations. The thorium and uranium air sampling results used for this evaluation are shown in 

Appendix A, Tables A-1 and A-2. The location where the sample was collected and the associated 

operation are provided for each result. 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Air concentrations (pCi/m3) of total thorium were calculated using the raw count data, combined 

assumed counting and collection efficiencies1, collection time, and sampler flow rate. The airborne 

thorium activity is assumed to be fully equilibrated between Th-232 and Th-228. This assumption 

that the isotopes generally exist in a 1-to-1 ratio maximizes the activity per unit mass collected on a 

filter. However, due to the extremely long half-life (and therefore, low specific activity) of Th-232, 

the mass remaining at the time of the air sample is counted is assumed to be essentially all associated 

with Th-232. Conversely, the mass of Th-228 is assumed to be immeasurably small (as compared to 

the Th-232) and is assumed to be zero for the purposes of this assessment. Therefore, thorium mass 

concentrations for the purpose of this mass comparison were derived using a Th-232 specific activity 

of 0.111 pCi/μg; uranium mass concentrations were derived using a specific activity of 0.672 pCi/μg. 

The mass concentrations (μg/m3

) for Th-232 and natural uranium are included in Appendix A, Tables 

A-1 and A-2, respectively. 

Descriptive statistics were generated for the thorium dataset and the uranium dataset using mass 

concentrations; these are shown in Table 7-1. 

Table 7-1: Descriptive Statistics for SRS Thorium 

and Uranium Air Monitoring Data (μg/m3

) 

Statistic Th-232 Uranium 

number of results 28 31 

minimum 0.49 0.87 

lower quartile 1.86 2.96 

mean 6.15 13.91 

median 3.42 6.33 

standard deviation 6.21 21.80 

upper quartile 8.15 12.76 

Maximum 25.46 112.27 

geometric mean 3.77 0.87 

The descriptive statistics were used to generate the box-and-whisker plots in Figure 7-1. When two 

box-and-whisker plots are displayed on the same scale, as in Figure 7-1, key features of the data can 

be graphically compared. The minimum values of both distributions are as close to zero as can be 

measured with the selected technology. The box portion of the plot is bounded by the lower quartile 

and upper quartile values and the median is between those two values (represented by the horizontal 

solid line inside the box). The box defines the range of the middle 50% of the data, which is also 

called the interquartile distance. Whiskers on each side of the box represent the 10th and 90th 

percentiles; the black dots represent the 5th and 95th percentiles. The conclusion drawn from this 

figure is that the thorium distribution median values are generally less than the uranium distribution. 

1

 Attribution: Robert Morris, Mel Chew and Associates, Inc. These assumptions are based on extensive experience with 

alpha counter and air sampling equipment. Several of these assumptions can be substantiated in the Air Force Institute of 

Operational Health consultative letter, Alpha Correction Factor for New Bioenvironmental Engineering Radiological Air 

Sampling Equipment – RADeCO® Model H-809VII (Correction Factor, 2005). 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Thus, the plots support the hypothesis that the thorium concentrations are in the same airborne 

concentration range (by mass) as the uranium values and the internal exposure profiles for uranium 

and thorium are similar. 

Figure 7-1: Comparison of SRS Thorium and Uranium Air Sample Data 

NIOSH performed a one-tail t-Test analysis (two-sample assuming unequal variances) to test the 

hypothesis that the mean of the natural log of the mass concentrations of thorium was less than or 

equal to the mean of the natural log of the mass concentrations obtained for uranium using α= 0.05 

(H0 : μt = μu) with the alternate hypothesis H1 : μt > μu. In order for the hypothesis to be true, P(t) ≤

tcritical must be true. Results of the hypothesis test are shown in Table 7-2. 

Table 7-2: t-Test Analysis 

Statistic Thorium Uranium 

mean 1.35 1.94 

variance 1.10 1.33 

observations 29 31 

hypothesized mean difference 0 --- 

degrees of freedom 58 --­

t Stat -2.08 --- 

P(T<=t) one-tail 0.02 --- 

t Critical one-tail 1.67 --­

Note: Data values used in the analysis are log transformations of 

the mass concentrations. 

Page 32 of 55 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

With a p value of 0.02, there is not sufficient statistical evidence to reject the null hypothesis (μt = μu) 

in favor of the alternate hypothesis (μt > μu). Since the specific activity of thorium is less than that of 

uranium, small errors in mass intake would result in less of an effect compared to uranium. Therefore, 

NIOSH concludes that uranium and thorium operations are sufficiently comparable that uranium 

bioassay assigned as thorium data can be used to bound doses received from exposures to thorium 

metal and to thoron from 1953 through 1965 in the 300 Area using the guidance and intake rates 

provided in the Addendum to the SEC-00103 Evaluation Report (NIOSH, 2010, Section 7.1.1.8). 

In ORAUT-RPRT-0046, NIOSH published an analysis of thoria air sample data obtained during 

periods of thoria work conducted in Building 313-M. The air samples were collected during thoria 

production operations. An interview with a former Health Physics technician who monitored the 

operations indicates that the thoria production operations were well-controlled and the intake potential 

was low (Personal Communication, 2009). The data and interviews show that during the periods 

when thoria processing campaigns were being conducted, a bounding thorium intake rate can be 

established based on the lognormally-fitted air sample data and assumptions regarding breathing rate. 

The interview with the former Health Physics technician suggested that exposure potential was 

equally low during periods of maintenance and decommissioning. This was confirmed by review of 

routine contamination survey data for that period data (Sawyer, 1966a; Sawyer 1966b; Sawyer 1966c; 

Sawyer 1966d; Sawyer, 1966e). NIOSH has more uranium air sample results that could be used to 

support assessing/bounding the thoron exposures because uranium canning was conducted at the same 

time as the thorium operations. Intake rates of Th-232 and thoron were derived from the air 

monitoring data and are available in ORAUT-RPRT-0046. 

A critique of ORAUT-RPRT-0046 inquired whether the analysis considered work with recycled 

thorium at 313-M. NIOSH’s response is that personnel working with thorium were much more likely 

to be exposed to uranium and, consequently, were bioassayed for uranium. Analyses of thorium 

nitrate stored in five railcars in 1966 showed U-233 contamination ranging from 0.5 to 1.3 ppm and 

total U ranging from 0.9 to 9.5 ppm (Maher, 1966). 

K, L, P, C and R Reactors and Associated Facilities 

NIOSH has not identified specific air monitoring data obtained in reactor facilities for monitoring the 

release of irradiated thorium. Thorium work at reactor facilities included assembly of encapsulated 

thorium slugs into target core assemblies, and irradiation of assemblies for varying but specified 

times. Once irradiation was completed, assemblies were stored in a cooling pool to permit decay 

(“cooling”) of mixed fission product activities. Analytical work conducted on irradiated thorium 

slugs was performed in hot caves with monitoring by Health Physics. An examination of the Special 

Hazards Database identified no incidents involving release of thorium contamination during handling 

or pre-irradiated or post-irradiated thorium slugs at reactor facilities. NIOSH finds that operations at 

reactor facilities were adequately controlled, and because the work was performed with encapsulated 

thorium in shielded contained environments, thorium exposures were controlled such that they can be 

bounded by the same methods used for the 300 Area. 

Page 33 of 55 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

F Canyon (Area) 

For Building 235-F from 1961 through 1965, the largest monthly quantity of thorium oxide present 

per available inventory reports was 50 to 500 pounds. NIOSH has not discovered documentation or 

information that would support a significant exposure potential to thorium in Building 235-F; 

however, based on the materials and quantities of thorium that existed in this location, NIOSH finds 

that potential doses from such exposures may be bounded using guidance in ORAUT-RPRT-0046. 

H Canyon (Area) 

NIOSH has not identified specific air monitoring data obtained in H Canyon or thorium bioassay data 

for workers in H Area. However, HIOSH has captured information on the handling of irradiated 

thorium and thorium by-products in H Canyon. SRS thorium wastes generated through 1964 were 

encased in concrete and shipped to either ORNL or to the 643-G burial ground (Progress Report, Sep 

1955; Progress Report, Oct 1961). 

As a result of the research and development work performed in Building 773-A and the TNX facility, 

a process to separate U-233 from irradiated thorium was well developed by 1965 when the first 

Thorex campaign began. Irradiated thorium was transported to the H Canyon. Dissolution was 

performed in an enclosed canyon to separate and recover the U-233. Once separated, the U-233 was 

concentrated and further treated by conversion to oxides suitable for shipment or storage in the H-B 

Line. Mixed fission products removed from the stream were sent to the tank farms. Separated 

thorium nitrate was stored in the canyon and in the HB Line and, after storage for a minimum of 231 

days, transported through pipe (> 2" diameter) to railcars where the ThNO2 was stored for up to one 

year. Railroad cars were equipped with 4" x 4" x 6" CWS filters with a rating of 10 cfm of air at 0.8" 

differential pressure to prevent particulate contamination during filling or from thermal expansion of 

the tank. Health Physics personnel monitored the loading of the cars. The cars were roped off to 

denote radiation control boundaries and the cars were inspected frequently (at least weekly) with 

binoculars to look for any leakage. An emergency procedure was in place to move the contents of a 

leaking railroad car to a stand-by car; the stand-by car, pump, and hose were readily available (Hobert, 

1965). NIOSH has found no documentation that shows that SRS ever encountered a railroad car 

leaking thorium nitrate. All ThNO2 was shipped to Fernald between 1966 and June 1972 (Maher, 

1966; Thorium Ledger, 1952-1972; Thorium CEVs, 1955-1962; Thorium JEVs, 1961-1962). 

NIOSH has determined there was a low risk of exposure to thorium nitrate in the process of pumping 

wastes to railcars and from railcar venting. Considering this information, NIOSH has determined that 

any doses resulting from potential thorium exposures associated with the operations in the H Canyon 

(Area) can be bounded using the associated thorium intake rates for the 300 Area for 1965 through 

1971 (ORAUT-RPRT-0046). 

Page 34 of 55 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Savannah River Laboratory 

Section 5.1.16 discusses the significant work that was performed in Building 773-A. Thorium 

inventory data shows significant quantities of “unencapsulated” thorium recorded for many of the 

years from 1953 through 1972. However, there is no breakdown on where in Building 773-A thorium 

was used. In summary, chemical analysis and chemical engineering studies for the support of plant 

operation activities were performed in Section 1, Wings B and C. Interviews with former engineers 

and scientists confirmed that these types of tasks were performed in Section 1 (Personal 

Communication, 2011c; Personal Communication, 2011d; Personal Communication, 2011e; Personal 

Communication, 2011f). 

Six steel “junior” caves complete with viewers and manipulators were equipped in some of the labs, 

including LB-106, LB-107, and LB-142 (Lab Notes, 1955; Lab Notes, 1955-1956). Some of the 

equipment in the junior caves included scale-downs of the separations equipment used in the 200 

Area. Although documented for use with plutonium, there was also a glove box facility located on the 

centerline of the wall dividing LB-126 and LB-130, which documentation shows to have had some 

thorium work (Data Capture, 2011). Physical property and corrosion testing, metallography and x-ray 

diffraction studies, and general physical and chemical studies in support of the reactor fuel 

development program were performed in laboratories in Section 1, Wing C, and Section 2. Physical, 

chemical engineering, and metallurgical work with high-level radioactive materials was performed in 

the 773-A Caves (also referred to as Part II of 773-A). By October 1954, a variety of cave apparatus 

was available, including: dimensioning equipment, contour tracing gauge, weighing scales, analytical 

balances, binocular periscope, stage cut-off machine for sectioning irradiated metal, chemical 

apparatus for dissolving fuel elements, and hardness testers. Fuel element fabrication testing and 

manufacture were performed in Part III of 773-A (also referred to as the Metallurgical Extension). It 

contained a laboratory, foundry, welding lab, and development office that provided for full-size 

metallurgical development work with capabilities for melting, vacuum melting, forging, rolling, heattreating, machining, welding, and pickling various metals (Du Pont, 1957). 

Figure 7-2 shows layout of Building 773-A (Building 773-A Layout, 2010). Grey-shaded areas show 

where thorium work was performed; yellow-shaded areas show change rooms and Health Physics 

offices. Change rooms were located next to building exits. At least one office (SRS engineer) was 

located in Part III of the building, which was a controlled area (Personal Communication, 2011g). No 

thorium work was conducted in Section 1, Wing A (Personal Communication, 2011b). 

Page 35 of 55 
SEC-00103 Addendum 2 07-21-11 

Figure 7-2: Building 773-A Thorium Operations Locations 
SEC-00103 Addendum 2 07-21-11 Savannah River Site 

Health Physics actively monitored locations where thorium operations were conducted. During its 

June 2011 review of the SRS notebooks (Lab Notes, 1955; Lab Notes, 1955-1956, Lab Notes, 1956­

1957b), NIOSH identified hundreds of radiological surveys made within the Savannah River 

Laboratory (773A). Health Physics surveyed and tagged material before it was transferred out of 

773A; this practice was extensively documented. NIOSH noted specific surveys of thorium materials 

which indicate “No Smearable Contamination Detected.” NIOSH also noted routine surveys 

performed in the hallways and change rooms looking for contamination with most indicating “no 

contamination detected.” Such records indicate an active program of contamination control dating 

back to the early 1950s (Lab Notes, 1954; Lab Notes, 1955; Lab Notes, 1955-1956; Lab Notes, 1956­

1957b). 

One 1955 notebook mentions that a list of persons who had worked with thorium at SRL and TNX 

had been compiled for inclusion on a roster for follow-up bioassay (Lab Notes, 1954; Lab Notes, 

1955-1956). It is likely that bioassay results obtained by NIOSH pertain to some of those workers. 

NIOSH noted that some air sampling was conducted in the metallurgical extension (Part III) during an 

operation that involved grinding of thorium. That particular job was covered by a Special Work 

Permit (SWP). The SWP stated that the individual doing the grinding was wearing an “assault mask” 

(respirator). This information illustrates that during high-risk operations that could involve significant 

inhalations, the radiation control organization took care to prevent the internal exposures (Lab Notes, 

1954; Lab Notes, 1955; Lab Notes, 1955-1956; Lab Notes, 1956-1957b). 

The Health Physics group provided training on all health physics topics to maintenance workers 

entering the 700 Area (Misc. Areas, 1955). At least some of the work with radioactive materials 

performed by SRL maintenance workers was done by SWP (Lab Notes, 1955; Lab Notes, 1956­

1957b). Maintenance and construction workers were consulted by Health Physics before and during 

operations involving contaminated areas or equipment (Lab Notes, 1956-1957b). 

Based on this Addendum 2 evaluation, there is clear indication that there was some potential for 

radiological exposure to “unencapsulated” thorium in 773A. Since equipment for small-scale canyon 

and “junior cave” experiments had been installed in Section I, it is reasonable to assume that work 

with thorium was conducted beyond bench-scale chemical analysis. The SRS notebooks reviewed in 

June 2011 (Lab Notes, 1954; Lab Notes, 1955; Lab Notes, 1955-1956; Lab Notes, 1956-1957b) noted 

thorium spills that resulted in contamination on the order of a few thousand dpm and that required 

clean-up of the labs before they could continue operating. One of the documented spills indicated that 

the highest smearable contamination was 37cpm which translated to about 105 dpm. Thus, spills of 

even low-level contamination were monitored by Health Physics. In addition, the notebooks 

discussed hand and foot monitors alarming due to metal chips embedded in the soles of worker’s 

shoes who had traveled through Part III of 773-A; this indicates there was some radioactive material 

in the form of chips on the floors in the Metallurgical Extension. NIOSH has made a qualitative 

evaluation of worker exposure potential for 773-A workers by year, as shown in Table 7-3 (Isotope 

Charts, 1953-1976). 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Table 7-3: Worker Exposure Potential in SRS Building 773-A 

Year Exposure Potential 

1953 Low 

1954 High 

1955 Medium 

1956 Medium 

1957 Low 

1958 Low 

1959 Low 

1960 Low 

1961 Low 

1962 Low 

1963 Low 

1964 High 

1965 High 

1966 High 

1967 High 

1968 Low 

1969 Medium 

1970 Medium 

1971 Medium 

1972 Low 

Source: Isotope Charts, 1953-1976 

In several notebooks, radiation control technicians identified procedural violations by operations 

personnel. Specifically, there were times when the operations personnel were doing work outside the 

scope of a special work permit and the radiation control technicians would observe the action, 

reporting the workers to Health Physics supervisors. There were also some examples of construction 

workers who violated the work permit conduct of operations requirements. In one case, two 

electricians were potentially exposed when they inappropriately accessed a fume hood that contained 

radioactive materials to work on an electrical device. The violation was observed by radiation control 

technicians who stopped the work and reported it to supervision. Another instance involved the use of 

hand and foot monitors. Some individuals set off monitor alarms due to metal chips being embedded 

in the soles of their shoes. Radiation control technicians proceeded to survey all of the workers shoes 

in the locker room and found additional instances of shoes with radioactive metal chips embedded in 

them (apparently because the workers were not surveying themselves prior to exiting the work area 

using the hand and foot monitors). The radiation control technicians began observing workers exiting 

the Metallurgical Lab. 

NIOSH believes that actual exposures to thorium in Building 773-A were minimal due to the 

radiological control operations within the facility. However, there are some documented lapses that 

resulted in contamination incidents (Lab Notes, 1954; Lab Notes, 1955; Lab Notes, 1955-1956; Lab 

Notes, 1956-1957b). In most instances, the radiation control lapses and the less-than- formal conduct 

of operations generally do not present a problem for dose reconstruction because there was a routine 

bioassay program that provided data that can be used to assess doses. 

Page 38 of 55 
 

SEC-00103 Addendum 2 08-09-11 Savannah River Site 

At SRL, NIOSH has obtained bioassay for the most dosimetrically-significant radionuclides. 

However, NIOSH has not discovered a sufficient amount of bioassay data for thorium over the period 

under evaluation in this ER Addendum 2, other than the period 1955-1956 for which NIOSH has 

obtained 225 thorium bioassay results for 175 workers (in NOCTS) (Thorium Records, 1956). Those 

bioassayed workers represented the following nineteen job titles (including Not Found). 

 Chemist  Helper  Physicist 

 Chemist Trainee  Junior Chemist  Research Supervisor 

 Clerk  Maintenance Foreman  Supervisor 

 Engineer  Mechanic  Technical Assistant 

 Engineer Trainee  Metallurgist  Technician 

 Engineering Assistant  Not Found 

 Foreman  Operator 

Some of these data indicate positive intakes of thorium from unencapsulated sources for some 

monitored workers; however, it is not known if this set of bioassay data represents all SRL workers 

exposed to thorium. Therefore, the data may be used to assess an individual’s dose but cannot be used 

to bound thorium doses of unmonitored SRL workers. NIOSH believes that no thorium urinalysis 

data exist for the period 1957 through 1972. While NIOSH does have the aforementioned thorium 

bioassay data, NIOSH cannot be certain that the bioassay program covered all workers who had a 

potential for exposure. Although NIOSH found notations indicating some air sampling had been done 

in Building 773-A, NIOSH has not captured actual air monitoring results for Building 773-A 

sufficient to model potential worker thorium intakes. 

Interviews with two former SRS Health Physics technicians established that only monitored personnel 

entered regulated areas (Personal Communication, 2011h, Personal Communication, 2011i); Part I, 

Sections IB and C and Part I, Sections II and III of Building 773-A were regulated. As shown in 

Figure 7-2, Building 773-A, Section 1A was an administrative area with Health Physics offices, 

change/shower rooms, and hand and foot monitors separating it from the radiological areas of 

Sections IB and IC and farther back. One of the technicians stated that all workers who worked in 

regulated areas had to wear film badges. He indicated that all workers, including visitors, were 

required to wear film badge dosimeters if entering or working in any radiological (regulated) areas. 

He indicated that supplemental pencil dosimeters (ion chambers) were also used to track exposures 

when working on some high-level jobs. Film badge dosimeters were stored in an administrative area 

on a board and were usually picked up every morning and returned to the storage board as the end of 

the shift. The technician indicated that there were no exceptions to workers having to wear dosimeters 

in regulated areas (Personal Communication, 2011h). 

Page 39 of 55 
SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

7.2.3.1 Methods for Bounding Operational Period Internal Dose 

Internal doses from potential exposure to thorium and thoron may be bounded for monitored workers 

in the 300 Area, the SRS reactors, and F and H canyons using: 

	 Guidance and intake rates using the (first) Addendum to SEC-00103 Evaluation Report for 

exposure to metals during the period 1953-1965 (NIOSH, 2010). 

	 Guidance and intake rates using ORAUT-RPRT-0046 for exposure to oxides during the period 

1964-1972. 

Personnel who worked in the 300 Area in 1964 and/or 1965 should be assigned the maximum dose 

derived from the two models. 

NIOSH has determined that it cannot estimate with sufficient accuracy internal radiation doses 

resulting from exposure to unencapsulated thorium at two SRS locations: 773A and the CMX/TNX 

facility from 1953 through September 1972. Due to the inability to estimate internal thorium doses in 

these two areas, NIOSH is recommending adding a class of workers to the SEC. NIOSH has 

developed dose reconstruction methodologies to estimate with sufficient accuracy internal and 

external doses incurred in all other SRS areas where thorium work was conducted. 

In order to identify members of the proposed SEC class, NIOSH proposes to use SRS external 

dosimetry records to identify the location where an energy employee picked up their dosimeter badge. 

The proposed class will be based on the SRS requirement that all workers entering a regulated area 

wear a dosimeter badge. External dose records identify the location where the energy employee 

picked up their dosimeter badge for a given period of time (typically a month or a quarter). There are 

two types of records that document these locations during the time period 1953 through September 

1972. The first is an “annual personnel meters card” used at the site until 1958. Table 7-4 lists the 

dosimeter codes pertaining to the areas covered in the evaluation where thorium was used and 

specifies the dosimeter codes that should be included in the NIOSH-proposed SEC class. 

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SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

Note: This is a new table that is not in either the original ER or the first addendum. This table does 

not replace an existing table in either of those documents. 

Table 7-4: Summary of Dosimeter Locations and Their Inclusion in the SEC 

Functional 

Designation 

Alpha-Numeric 

Designation 

Area 

Designation 

Unencapsulated 

Thorium? 

Encapsulated 

Thorium? 

Inclusion in 

SEC? 

Separations 200F F No No No 

200H H No No(a) No 

Manufacturing 300M M Yes Yes No(b) 

Heavy Water 400D D No No No 

Technical 

Semi-works 

773A A Yes Yes Yes 

777M M Yes Yes No(c) 

CMX/TNX A,G, CMX, 

or TNX Yes Yes Yes 

A Area Support A Area A - - Yes(d) 

Reactors 

100R R No Yes No 

100P P No Yes No 

100L L No Yes No 

100K K No Yes No 

100C C No Yes No 

Central Shops CS G Yes(e) 

(a)	 Unencapsulated thorium was not present in the H area prior to 1964. 

(b) Internal doses from potential exposure to thorium and thoron may be bounded for monitored 300M area workers 

using: (1) guidance and intake rates specified in the (first) Addendum to SEC-00103 Evaluation Report (NIOSH, 

2010) for exposure to metals during the period 1953-1965; (2) guidance and intake rates specified in ORAUTRPRT-0046 for exposure to oxides during the period 1964-1972; and (3) the maximum dose derived from the 

preceding two models for personnel who worked in the 300M area in 1964 and/or 1965. 

(c)	 The 777M area conducted reactivity measurements on mostly encapsulated thorium. Any exposure to 

unencapsulated thorium can be estimated using the methods developed for the 300M area. Therefore, the 777M 

workers are not recommended for inclusion in the SEC. 

(d) The A Area includes other support facilities for which unencapsulated thorium was not typically present; however, 

workers in this area could have worked for extended periods of time in 773A and therefore are recommended for 

inclusion in the SEC. 

(e)	 Although thorium was not present in the Central Shops area, construction trades workers could work in areas where 

unencapsulated thorium was present for extended periods of time and therefore are recommended for inclusion in 

the SEC. 

In general, these early dosimeter cards indicate a wearer’s work location; however, there are occasions 

where the area designation is blank (i.e., not filled out or unknown). When a card is blank for a 

worker, that individual should be included in the SEC because this circumstance is effectively 

equivalent to a missing record (i.e., NIOSH cannot state with certainty that the individual was or was 

not conducting work in either the 773A building or the CMX/TNX facilities). 

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SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

The second type of record is the personnel dosimetry printouts, also called “personnel meters.” 

Post-1957, the work designation and time resolution improved significantly; they were reported on a 

biweekly basis from 1958 through 1962, and on a quarterly basis from 1963 through September 1972. 

During this same period, there was greater location definition within areas. Table 7-5 lists the 

designation codes for each of the areas and some sub-areas. The last column identifies workers who 

should be considered part of the NIOSH-proposed SEC class (i.e., they have a code for an area with 

the potential for exposure to unmonitored unencapsulated thorium). 

Note: This is a new table that is not in either the original ER or the first addendum. This table does 

not replace an existing table in either of those documents. 

Table 7-5: Location Designations from 1958 through September 1972 

Functional 

Designation 

Alpha-Numeric 

Designation 

HP Area 

Code 

Unencapsulated 

Thorium? 

Encapsulated 

Thorium? 

Inclusion in 

SEC? 

Separations 200F 1A No No No 

200H 2A No Yes No 

Manufacturing 300M 3A Yes Yes No(a) 

Heavy Water 400D 4A No No No 

Technical 

Semi-works 

773A 5A Yes Yes Yes 

777M 5B Yes Yes No(b) 

CMX/TNX 5C Yes Yes Yes 

A Area Support A Area 6B-6Z(b) Yes(c) 

Reactors 

100R 7A No Yes No 

100P 8A No Yes No 

100L 9A No Yes No 

100K 10A No Yes No 

100C 11A No Yes No 

Central Shops CS 

12D-12H(d) 

and 

12J-12Z(e) 

Yes(f) 

(a)	 Internal doses from potential exposure to thorium and thoron may be bounded for monitored 300M area workers 

using: (1) guidance and intake rates specified in the (first) Addendum to SEC-00103 Evaluation Report (NIOSH, 

2010) for exposure to metals during the period 1953-1965; (2) guidance and intake rates specified in ORAUTRPRT-0046 for exposure to oxides during the period 1964-1972; and (3) the maximum dose derived from the 

preceding two models for personnel who worked in the 300M area in 1964 and/or 1965. 

(b) The 777M area conducted reactivity measurements on mostly encapsulated thorium. Any exposure to 

unencapsulated thorium can be estimated using the methods developed for the 300M area. Therefore, the 777M 

workers are not recommended for inclusion in the SEC. 

(c)	 The main administration building 703A should not be included in the recommended SEC class. The designation 

for this building was 6A. This was an office building that managers and program directors worked from and were 

generally issued badges so that they could move throughout the site. It is improbable that these individuals would 

work hands-on with radioactive materials, and therefore, be exposed to unencapsulated thorium for extended 

periods of time. All other A Aarea workers could have spent extended periods of time in 773A and therefore are 

recommended for inclusion in the SEC. 

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SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

(d) This is constructions trades worker codes that operated out of the Central Shops area. The first three sub-shops 

relate to transportation. Workers from these three shops would only have been exposed to encapsulated thorium; 

thus, there was no potential for internal exposure and therefore they are not recommended for inclusion in the 

SEC. The three transportations shops were: 

- 618G (12A) = Locomotive Shop 

- 705G (12B) = Traffic and Transportation Shop 

- 706G (12C) = Traffic and Transportation Office 

(e)	 The “temporary construction” or TC area, later known as B Area, should not be included in the recommended 

SEC class. The designation for this area was 12I. This area housed the offices for procurement, payroll, 

accounting, medical, timekeeping as well as management offices for the construction division. The actual 

construction trades workers worked out of the main portion of the Central Shops area designated by the selected 

codes. 

(f)	 Although thorium was not present in the Central Shops area, construction trades workers could work in areas 

where unencapsulated thorium was present for extended periods of time and therefore are recommended for 

inclusion in the SEC. 

7.2.4 Internal Dose Reconstruction Feasibility Conclusion 

NIOSH lacks sufficient bioassay, air monitoring data, and source term data necessary to bound 

thorium doses for monitored personnel who worked in the Building 773A or TNX. Although NIOSH 

found that it is not possible to completely reconstruct internal radiation doses for the period from 

January 1, 1953 through September 30, 1972 for this group of workers, NIOSH intends to use any 

internal monitoring data that may become available for an individual claim (and that can be 

interpreted using existing NIOSH dose reconstruction processes or procedures). Dose reconstructions 

for individuals employed at the Savannah River Site during the period from January 1, 1953 through 

September 30, 1972, but who do not qualify for inclusion in the SEC, may be performed using these 

data as appropriate. 

NIOSH can bound internal doses received from potential exposure to thorium metals using bioassay 

data and to thoron using available air monitoring data for monitored personnel who worked in the 300 

Area, SRS reactors, F canyon and/or H canyon. 

7.6 Summary of Feasibility Findings for Petition SEC-00103 

This report evaluates the feasibility for completing dose reconstructions for all construction workers 

who worked in any thorium area at the Savannah River Site from January 1, 1953 through December 

31, 1972. NIOSH found that the available monitoring records, process descriptions and source term 

data available are not sufficient to complete dose reconstructions for all members of the evaluated 

class, specifically: All externally monitored employees of the Department of Energy, its predecessor 

agencies, and their contractors and subcontractors who worked at the Savannah River Site from 

January 1, 1953 through December 31, 1957, and whose records have dosimetry codes A, G, CMX, or 

TNX; and all externally monitored employees of the Department of Energy, its predecessor agencies, 

and their contractors and subcontractors who worked at the Savannah River Site from January 1, 1958 

through September 30, 1972, and whose records have dosimetry codes 5A, 5C, 6B through 6Z, 12D 

through 12H, or 12J through 12Z. 

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SEC-00103 Addendum 2 08-09-11	 Savannah River Site 

Potential radiation doses can be bounded for those employees who worked during the proposed SEC 

time period but who did not work in the specified thorium-related locations. The remainder of the 

class evaluated in the original SEC-00103 SRS Evaluation Report can be bounded, specifically: (1) 

the period before the proposed SEC class (January 1, 1950 through December 31, 1952); and (2) the 

period after the proposed SEC class (October 1, 1972 through December 31, 2007). Table 7-5 

summarizes the results of the feasibility findings at Savannah River Site for each exposure source 

during the time periods specified above. 

Table 7-6: Summary of Feasibility Findings for SEC-00103 

January 1, 1950 through December 31, 1952 (before proposed SEC class period) 

January 1, 1953 through September 30, 1972 (proposed SEC class period) 

October 1, 1972 through December 31, 2007 (after proposed SEC class period) 

Source of Exposure 

Designated Codes (1953-Sep 1972): 

Jan. 1, 1953 through Dec. 31, 1957: A, G, 

CMX, or TNX 

Jan. 1, 1958 through Sep. 30, 1972: 5A, 5C, 

6B through 6Z, 12D through 12H, or 12J 

through 12Z 

Sitewide - Non-designated Codes: 

Jan. 1, 1953 through Sep. 30, 1972 

Sitewide – All Codes: 

Jan. 1, 1950 through Dec. 31, 1952 

Oct. 1, 1972 through Dec. 31, 2007 

Reconstruction 

Feasible 

Reconstruction 

Not Feasible 

Reconstruction 

Feasible 

Reconstruction 

Not Feasible 

Internal1 X X 

 - Thorium/Thoron X X2 

External X X 

- Gamma X X 

 - Beta X X 

- Neutron X X 

 - Occupational Medical X-ray X X 

1	 Internal includes an evaluation of urinalysis (in vitro), airborne dust, and lung (in vivo) data 

2	 There was no thorium on site during the period January 1, 1950 through December 31, 1952. Internal doses from potential 

exposures to thorium metals can be bounded using bioassay data, and thoron doses can be bounded using available air 

monitoring data for monitored personnel who worked in the 300 Area, SRS reactors, F canyon and/or H canyon from 

January 1, 1953 through September 30, 1972. Although thorium was still on site after September 1972, NIOSH has 

determined a sufficient end point for this thorium evaluation based on the D&D of 300 Area thorium operations. NIOSH 

intends to continue reviewing and assessing any additional thorium documentation and data obtained for the postSeptember 1972 period. The findings of this research will be relayed accordingly if the research results require 

modification of any existing conclusions made in the SRS SEC Evaluation Report/Addendums. 

Page 44 of 55 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Although NIOSH found that it is not possible to completely reconstruct radiation doses for the 

proposed class, NIOSH intends to use any internal and external monitoring data that may become 

available for an individual claim (and that can be interpreted using existing NIOSH dose 

reconstruction processes or procedures). Therefore, dose reconstructions for individuals employed at 

the Savannah River Site during the period from January 1, 1953 through September 30, 1972, but who 

do not qualify for inclusion in the SEC, may be performed using these data as appropriate. 

8.0 Evaluation of Health Endangerment for Petition SEC-00103 

The health endangerment determination for the class of employees covered by this evaluation report is 

governed by both EEOICPA and 42 C.F.R. § 83.13(c)(3). Under these requirements, if it is not 

feasible to estimate with sufficient accuracy radiation doses for members of the class, NIOSH must 

also determine that there is a reasonable likelihood that such radiation doses may have endangered the 

health of members of the class. Section 83.13 requires NIOSH to assume that any duration of 

unprotected exposure may have endangered the health of members of a class when it has been 

established that the class may have been exposed to radiation during a discrete incident likely to have 

involved levels of exposure similarly high to those occurring during nuclear criticality incidents. If 

the occurrence of such an exceptionally high-level exposure has not been established, then NIOSH is 

required to specify that health was endangered for those workers who were employed for a number of 

work days aggregating at least 250 work days within the parameters established for the class or in 

combination with work days within the parameters established for one or more other classes of 

employees in the SEC. 

In its evaluation NIOSH found that it does have sufficient bioassay and air monitoring data to bound 

thorium doses for some members of the evaluated class. Chiefly, NIOSH can bound thorium doses for 

monitored workers who worked in the 300 Area, SRS reactors, F canyon and/or H canyon. Based on 

the sum of information available from available resources, NIOSH’s evaluation determined that it is 

not feasible to estimate radiation dose with sufficient accuracy for a group of members of the NIOSHevaluated class for the time period January 1, 1953 through September 30, 1972. Therefore, the 

resulting NIOSH-proposed SEC class must include a minimum required employment period as a basis 

for specifying that health was endangered for this time period. NIOSH further determined that it is 

feasible to estimate radiation dose with sufficient accuracy for members of the NIOSH-evaluated class 

for the time periods: (1) January 1, 1950 through December 31, 1952; and (2) October 1, 1972 

through December 31, 2007. Therefore, a health endangerment determination is not required for these 

two time periods. 

Page 45 of 55 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

9.0 Class Conclusion for Petition SEC-00103 

Based on its full research of the class under evaluation, NIOSH has defined a single class of 

employees for which NIOSH cannot estimate radiation doses with sufficient accuracy. The NIOSHproposed class to be added to the SEC includes all externally monitored employees of the Department 

of Energy, its predecessor agencies, and their contractors and subcontractors who worked at the 

Savannah River Site from January 1, 1953 through December 31, 1957, and whose records have 

dosimetry codes A, G, CMX, or TNX; and all externally monitored employees of the Department of 

Energy, its predecessor agencies, and their contractors and subcontractors who worked at the 

Savannah River Site from January 1, 1958 through September 30, 1972, and whose records have 

dosimetry codes 5A, 5C, 6B through 6Z, 12D through 12H, or 12J through 12Z. 

NIOSH has carefully reviewed all material sent in by the petitioner, including the specific assertions 

stated in the petition, and has responded herein (see Section 7.4). NIOSH has also reviewed available 

technical resources and many other references, including the Site Research Database (SRDB), for 

information relevant to SEC-00103. In addition, NIOSH reviewed its NOCTS dose reconstruction 

database to identify EEOICPA-related dose reconstructions that might provide information relevant to 

the petition evaluation. 

These actions are based on existing, approved NIOSH processes used in dose reconstruction for 

claims under EEOICPA. NIOSH’s guiding principle in conducting these dose reconstructions is to 

ensure that the assumptions used are fair, consistent, and well-grounded in the best available science. 

Simultaneously, uncertainties in the science and data must be handled to the advantage, rather than to 

the detriment, of the petitioners. When adequate personal dose monitoring information is not 

available, or is very limited, NIOSH may use the highest reasonably possible radiation dose, based on 

reliable science, documented experience, and relevant data to determine the feasibility of 

reconstructing the dose of an SEC petition class. NIOSH contends that it has complied with these 

standards of performance in determining the feasibility or infeasibility of reconstructing dose for the 

class under evaluation. 

Page 46 of 55 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

10.0 References (for Addendum 2) 

42 C.F.R. pt. 83, Procedures for Designating Classes of Employees as Members of the Special 

Exposure Cohort Under the Energy Employees Occupational Illness Compensation Program Act of 

2000; Final Rule; May 28, 2004; SRDB Ref ID: 22001 

Building 773-A Layout, 2010, Building 773-A Layout with Indications of Thorium Work, Savannah 

River Site; occupancy data as of March 29, 2010; SRDB Ref ID: 98490 

Correction Factor, 2005, Alpha Correction Factor for New Bioenvironmental Engineering 

Radiological Air Sampling Equipment – RADeCO® Model H-809VII, consultative letter, Air Force 

Institute of Operational Health; 2005; http://airforcemedicine.afms.mil/idc/groups/ 

public/documents/afms/ctb_039469.pdf; SRDB Ref ID: 71951 

Data Capture, 2011, [Name redacted] Data Capture Notes, National Institute of Occupational Safety 

and Health; various dates in June 2011; SRDB Ref ID: 99499 

Dummy Slugs, 1958, Evaluation of Thorium Dummy Slugs for Interim Neptunium Irradiation 

Program, Savannah River Laboratory Technical Division, December 30, 1958; SRDB Ref ID: 99402 

Du Pont, 1957, Savannah River Plant Engineering and Design History Volume IV #300/700 Areas 

and General Services and Facilities; E. I. du Pont de Nemours and Company (Du Pont); January 

1957; SRDB Ref ID: 33180 

Du Pont, 1984a, History of the Savannah River Laboratory, Volume I-Production Reactor, Fuel, and 

Target Technology; E. I. du Pont de Nemours and Company (Du Pont); August 1984; SRDB Ref ID: 

89232 

Du Pont, 1984b, History of the Savannah River Laboratory, Volume II-Separations Technology; E. I. 

du Pont de Nemours and Company (Du Pont); June 1984; SRDB Ref ID: 89523 

Du Pont, 1984c, History of the Savannah River Laboratory, Volume III-Power Reactor and Fuel 

Technology; E. I. du Pont de Nemours and Company (Du Pont); June 1984; SRDB Ref ID: 90054 

Du Pont, 1984d, History of the Savannah River Laboratory, Volume IV-General; E. I. du Pont de 

Nemours and Company (Du Pont); August 1984; SRDB Ref ID: 49497 

Hobert, 1965, By-Product Thorium Nitrate Solution Handling and Storage; R. H. Hobert; November 

19, 1965; SRDB Ref ID: 58541, pdf pp. 3-4 

Isotope Charts, 1953-1976, Isotope Charts for the Years 1953 Through 1976, Savannah River Site; 

1953-1976; SRDB Ref ID: 94568 

Lab Notes, 1954, SRL Laboratory Notebook, R. A. Moyer; Savannah River Laboratory; various dates 

in 1954; DPSTN-00049; SRDB Ref ID: 99460 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Lab Notes, 1955, SRL Laboratory Notebook, R. A. Moyer; Savannah River Laboratory; various dates 

in 1955; DPSTN-00380; SRDB Ref ID: 99461 

Lab Notes, 1955-1956, SRL Laboratory Notebook, K. K. Brown; Savannah River Laboratory; various 

dates in 1955-1956; DPSTN-00040; SRDB Ref ID: 99434 

Lab Notes, 1956-1957a, SRL Laboratory Notebook, W. G. Rinehart; Savannah River Laboratory; 

various dates in 1956-1957; DPSTN-00704; SRDB Ref ID: 99462 

Lab Notes, 1956-1957b, SRL Laboratory Notebook, R. A. Moyer; Savannah River Laboratory; various 

dates in 1956-1957; DPSTN-00772; SRDB Ref ID: 99464 

Lab Notes, 1956-1962, SRL Laboratory Notebook, R. A. Moyer; Savannah River Laboratory; various 

dates in 1956-1962; DPSTN-00716; SRDB Ref ID: 99463 

Lab Notes, 1960, SRL Laboratory Notebook, C. D. Loadholt; Savannah River Laboratory; various 

dates in 1960; DPSTN-01442; SRDB Ref ID: 99466 

Log Sheets, 1955, Radiation Survey Logsheets M-Area 2/55-3/55, Savannah River Plant, various date 

in 1955; SRDB Ref ID: 99493 

Maher, 1966, Thorium Nitrate Analyses; R. Maher; February 15, 1966; SRDB Ref ID: 58544, pdf pp. 

4-5 

Misc. Areas, 1955, Miscellaneous Areas: June 1955, inter-office memorandum, Savannah River 

Plant, June 29, 1955; SRDB Ref ID: 99490 

Montenyohl, 1952, Thorium Research Requirements, memorandum to file; V. I. Montenyohl; 

February 6, 1952; SRDB Ref ID: 49556, pdf pp. 3-6 

NIOSH, 2008, SEC Petition Evaluation Report for Petition SEC-00103, Savannah River Site; 

National Institute for Occupational Safety and Health (NIOSH); November 14, 2008; SRDB Ref ID: 

90587 

NIOSH, 2010, SEC Petition Evaluation Report for Petition SEC-00103, Savannah River SiteAddendum 1; National Institute for Occupational Safety and Health (NIOSH); April 28, 2010; SRDB 

Ref ID: 90588 

ORAUT-RPRT-0046, Analysis of Savannah River Site Thoria and Thoron Air Sampling Data as a 

Method of Intake Bounding between 1965 and 1971, Oak Ridge Associated Universities; Rev. 00; 

May 18, 2010; SRDB Ref ID: 81418 

Personal Communication, 2009, Personal Communication with Former Health Physics Technician; 

Telephone Interview by ORAU Team, August 13, 2009, SRDB Ref ID: 73086 

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SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Personal Communication, 2011a, Personal Communication with Former Health Physics Technician; 

Telephone Interview by ORAU Team, March 17, 2011, SRDB Ref ID: 93641; Follow-up interview, 

June 15, 2011, SRDB Ref ID: 98144 

Personal Communication, 2011b, Personal Communication with Former Health Physics Technician; 

Telephone Interview by ORAU Team, March 17, 2011, SRDB Ref ID: 93642; Follow-up interview, 

June 15, 2011, SRDB Ref ID: 98145 

Personal Communication, 2011c, Personal Communication with Former Supervisor of Reactor 

Support Group; Telephone Interview by ORAU Team; April 14, 2011; SRDB Ref ID: 94988 

Personal Communication, 2011d, Personal Communication with Former Process Coordinator; 

Telephone Interview by ORAU Team; March 31, 2011; SRDB Ref ID: 95253 

Personal Communication, 2011e, Personal Communication with Former Lab Worker and QA 

Employee; Telephone Interview by ORAU Team; March 31, 2011; SRDB Ref ID: 95254 

Personal Communication, 2011f, Personal Communication with Former Manager of Plant Facilities 

and Services; Telephone Interview by ORAU Team; May 5, 2011, 2:00 PM; SRDB Ref ID: 96050 

Personal Communication, 2011g, Personal Communication with Former SRS Employee; Telephone 

Interview by ORAU Team; May 16, 2011, 11:00 AM; SRDB Ref ID: 96343 

Personal Communication, 2011h, Personal Communication with Former SRS Employee; Telephone 

Interview by ORAU Team; June 15, 2011; SRDB Ref ID: 98144 

Personal Communication, 2011i, Personal Communication with Former Health Physics Technician; 

Telephone Interview by ORAU Team, June 15, 2011, SRDB Ref ID: 98145 

Progress Report, Jul 1954, Monthly Progress Report for July 1954; E. I. du Pont de Nemours and 

Company; issued August 19, 1954; SRDB Ref ID: 16851 

Progress Report, Aug 1954, Monthly Progress Report for August 1954; E. I. du Pont de Nemours and 

Company; issued September 15, 1954; SRDB Ref ID: 17106 

Progress Report, Oct 1954, Monthly Progress Report for October 1954; E. I. du Pont de Nemours and 

Company; issued November 16, 1954; SRDB Ref ID: 11458 

Progress Report, Nov 1954, Monthly Progress Report for November 1954; E. I. du Pont de Nemours 

and Company; issued December 20, 1954; SRDB Ref ID: 11459 

Progress Report, Dec 1954, Monthly Progress Report for December 1954; E. I. du Pont de Nemours 

and Company; issued January 19, 1955; SRDB Ref ID: 11461 

Progress Report, Feb 1955, Monthly Progress Report for February 1955; E. I. du Pont de Nemours 

and Company; issued March 18, 1955; SRDB Ref ID: 11465 

Page 49 of 55 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Progress Report, Sep 1955, Monthly Progress Report for September 1955; E. I. du Pont de Nemours 

and Company; issued October 21, 1955; SRDB Ref ID: 11476 

Progress Report, Dec 1958, Monthly Progress Report for December 1958; E. I. du Pont de Nemours 

and Company; issued January 23, 1959; SRDB Ref ID: 11615 

Progress Report, Jun 1959, Progress Report for June 1959; E. I. du Pont de Nemours and Company; 

issued July 21, 1959; SRDB Ref ID: 11628 

Progress Report, Aug 1960, Monthly Progress Report for August 1960; E. I. du Pont de Nemours and 

Company; issued September 20, 1960; SRDB Ref ID: 16848 

Progress Report, Oct 1961, Progress Report for October 1961; E. I. du Pont de Nemours and 

Company; issued November 20, 1961; SRDB Ref ID: 11796 

Sawyer, 1966a, Radiation Survey Log Sheet from Building 313-M, April 15, 1966; J. Sawyer; April 

15, 1966; SRDB Ref ID: 70243 

Sawyer, 1966b, Radiation Survey Log Sheet from the 300-M and 3/700 Area, April 27 to May 25, 

1966; J. Sawyer; 1966; SRDB Ref ID: 70120 

Sawyer, 1966c, Radiation Survey Log Sheet from the 300-M and 3/700 Area, June to August 25, 1966; 

J. Sawyer, H. C. Sims, A. Alexander; 1966; SRDB Ref ID: 70118 

Sawyer, 1966d, Radiation Survey Log Sheets from the 300-M and 3/700 Area, August 31 to October 

25, 1966; J. Sawyer, H. C. Sims, A. Alexander; 1966; SRDB Ref ID: 70115 

Sawyer, 1966e, Radiation Survey Log Sheets from the 300-M and 3/700 Area, October 26, 1966 to 

February 24, 1967 ; J. Sawyer, H. C. Sims, A. Alexander, et. al.; 1966; SRDB Ref ID: 70114 

Slug, 1955, SRP 88 Slug Dissolving, inter-office memorandum from M. R. Caverly to D. G. Karraker, 

Savannah River Laboratory Technical Division; October 7, 1955; SRDB Ref ID: 94565 

Swanson, 2006, CMX and TNX Savannah River’s Pilot Plants; Mark T. Swanson and Mary Beth 

Reed, New South Associates; November 30, 2006; SRDB Ref ID: 93961 

Thorium CEVs, 1955-1962, SF Accountability Dept. Cross Entry Vouchers, C. H. Miller, Savannah 

River Site; various dates in 1955-1962; SRDB Ref ID: 94551 

Thorium JEVs, 1961-1962, SF Accountability Dept. Journal Entry Vouchers, C. H. Miller, Savannah 

River Site; various dates in 1961-1962; SRDB Ref ID: 94555 

Page 50 of 55 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Thorium Ledger, 1952-1972, Thorium Accountability Ledger for 1952 Through 1972, Savannah River 

Site; 1952-1972; SRDB Ref ID: 94571 

Thorium Records, 1956, Thorium Record Book February 28 through November 7, 1956; Savannah 

River Site, unknown author; 1956; SRDB Ref ID: 49573 

Page 51 of 55 
SEC-00103 Addendum 2 08-09-11 Savannah River Site 

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Page 52 of 55 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Appendix A: SRS Thorium and Uranium Air Sample Results 

Table A-1: SRS Thorium Air Sample Results 

Sampled for Building Location Comment Collection 

Date cpm 

Derived 

Concentration 

Th-232 

(pCi/m3

) 

Mass/volume 

Th-232 

(μg/m3

)

†

thorium 320M Lathe Room Cutting and 

machining rods 6/22/1954 14.3 0.37 3.37 

thorium 320M Lathe Room Cutting and 

machining rods 6/22/1954 12.0 0.30 2.74 

thorium 320M Lathe Room Cutting and 

machining rods 6/23/1954 28.0 0.69 6.26 

thorium 320M Lathe Room Cutting and 

machining rods 6/23/1954 56.7 1.34 12.03 

thorium 320M Lathe Room Cutting and 

machining rods 6/25/1954 4.0 0.07 0.64 

thorium 320M Lathe Room Cutting and 

machining rods 6/25/1954 7.7 0.16 1.41 

thorium 320M Lathe Room Cutting and 

machining rods 6/25/1954 36.3 0.47 4.28 

thorium 320M Lathe Room Cutting and 

machining rods 6/28/1954 31.0 0.37 3.29 

thorium 320M Lathe Room Cutting and 

machining rods 6/29/1954 44.0 0.90 8.12 

thorium 320M Lathe Room Cutting and 

machining rods 6/29/1954 42.8 0.92 8.25 

thorium 320M Lathe Room Cutting and 

machining rods 6/29/1954 38.3 0.62 5.60 

thorium 320M Lathe Room Cutting and 

machining rods 6/30/1954 35.0 0.78 7.07 

thorium 320M Lathe Room Cutting and 

machining rods 6/30/1954 30.0 2.83 25.46 

thorium 320M Lathe Room Cutting and 

machining rods 7/1/1954 10.0 0.26 2.36 

thorium 320M Lathe Room Cutting and 

machining rods 7/2/1954 4.7 0.10 0.87 

thorium 320M Lathe Room Cutting and 

machining rods 7/2/1954 3.7 0.32 2.88 

thorium 320M Lathe Room Cutting and 

machining rods 7/6/1954 46.6 1.83 16.48 

thorium 320M Lathe Room Cutting and 

machining rods 7/7/1954 55.3 2.17 19.55 

thorium 320M Lathe Room Cutting and 

machining rods 7/8/1954 37.3 1.46 13.19 

thorium 320M Lathe Room Cutting and 

machining rods 7/9/1954 8.0 0.19 1.70 

thorium 320M Lathe Room Cutting and 

machining rods 7/9/1954 26.1 0.61 5.54 

Page 53 of 55 
 

 

 

 

 

 

 

 

 

 

 

 

 

SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Table A-1: SRS Thorium Air Sample Results 

Sampled for Building Location Comment Collection 

Date cpm 

Derived 

Concentration 

Th-232 

(pCi/m3

) 

Mass/volume 

Th-232 

(μg/m3

)

†

thorium 320M Spectro-Chem 

Lab Grinding 7/30/1954 28.0 1.10 9.90 

thorium 320M Swagging 

Area 

Swagging of 

rods 8/11/1954 9.0 0.21 1.91 

thorium 320M Swagging 

Area 

Swagging of 

rods 8/12/1954 3.0 0.05 0.49 

thorium 313M Special 

Process 

Handling 

Thorium 4/15/1955 3.8 0.15 1.34 

thorium 313M Special 

Process 

One foot from 

welding of slugs 4/15/1955 2.6 0.08 0.69 

thorium 313M Special 

Process 

Two feet from 

welding of slugs 4/15/1955 3.6 0.38 3.41 

thorium 313M Special 

Process Thorium in room 5/3/1955 12.9 0.38 3.43 

Table A-2: SRS Uranium Air Sample Results 

Sampled for Building Location Comment Collection 

Date cpm 

Derived 

Concentration 

Th-232 

(pCi/m3

) 

Mass/volume 

U-nat 

(μg/m3

)

†

uranium 320M Special Metal 

Prep Lab Cutting 7/17/1957 7.0 0.58 0.87 

uranium 321M Special Lathe Machining 11/21/1957 281.0 37.33 55.54 

uranium 321M Lathe Room 

Cutting 

Natural 

Uranium 

11/7/1957 7.0 1.86 2.77 

uranium 321M Lathe Room Cutting 

Billets 12/30/1957 32.0 4.25 6.33 

uranium 321M Lathe Room Cutting and 

Machining 10/6/1957 31.0 2.75 4.09 

uranium 321M Lathe Room Cutting and 

Machining 12/27/1957 28.0 3.72 5.53 

uranium 321M Lathe Room Cutting 

Billets 12/19/1957 11.0 1.46 2.17 

uranium 321M Sanding Hood Sanding 12/31/1957 8.0 0.71 1.05 

uranium 321M Lathe Room Cutting and 

Machining 11/14/1957 17.0 1.51 2.24 

uranium 321M Press Drilling 

Billet 12/6/1957 199.0 22.03 32.78 

Page 54 of 55 
 

 

 

 

 

 

SEC-00103 Addendum 2 08-09-11 Savannah River Site 

Table A-2: SRS Uranium Air Sample Results 

Sampled for Building Location Comment Collection 

Date cpm 

Derived 

Concentration 

Th-232 

(pCi/m3

) 

Mass/volume 

U-nat 

(μg/m3

)

†

uranium 313M MarkVI Lathe 

Room 

Cutting and 

Machining 12/19/1956 114.2 17.83 26.52 

uranium 313M MarkVI Lathe 

Room 

Cutting and 

Machining 11/3/1956 10.0 1.89 2.82 

uranium 313M MarkVI Lathe 

Room 

Cutting and 

Machining 11/4/1956 8.6 1.63 2.42 

uranium 313M MarkVI Lathe 

Room 

Cutting and 

Machining 12/19/1956 16.3 6.78 10.10 

uranium 313M MarkVI Lathe 

Room 

Cutting and 

Machining 12/21/1956 40.6 6.34 9.43 

uranium 313M MarkVI Lathe 

Room 

Cutting and 

Machining 12/20/1956 74.3 11.82 17.59 

uranium 313M Mark III Lathe 

Room 

Cutting and 

Machining 12/7/1956 30.7 9.58 14.26 

uranium 313M Mark III Lathe 

Room 

Cutting and 

Machining 11/6/1956 20.8 8.12 12.08 

uranium 313M Mark III Lathe 

Room 

Cutting and 

Machining 11/11/1956 11.8 2.23 3.32 

uranium 313M Mark III Lathe 

Room 

Cutting and 

Machining 8/31/1956 10.7 2.23 3.31 

uranium 313M Mark VI Lathe 

Room 

Cutting and 

Machining 12/10/1956 10.7 2.09 3.11 

uranium 313M Mark VI Lathe 

Room 

Cutting and 

Machining 12/20/1956 36.8 7.66 11.40 

uranium 313M Mark VI Lathe 

Room 

Cutting and 

Machining 12/19/1956 23.1 5.15 7.66 

uranium 320M Mark VI Lathe 

Room 

Cutting and 

Machining 4/2/1957 15.0 4.26 6.33 

uranium 313M Lathe Room Cutting and 

Machining 12/16/1956 50.0 7.80 11.61 

uranium 321M Lathe Room Cutting and 

Machining 9/24/1957 168.0 22.32 33.21 

uranium 321M Lathe Room Cutting and 

Machining 10/24/1957 7.0 0.93 1.38 

uranium 313M Lathe Room Cutting 

Billets 12/11/1956 69.0 7.18 10.68 

uranium 321M Lathe Room Cutting 

Billets 11/29/1957 24.0 3.19 4.74 

uranium 321M Press Drilling 12/12/1957 568.0 75.45 112.27 

uranium 321M Lathe Room Cleaning up 

Chips 10/26/1957 68.0 9.03 13.44 

Page 55 of 55