SEC Petition Evaluation Report

Petition SEC-00058 

Report Rev # 0 Report Submittal Date 09-01-2006 

Subject Expert(s): Robert M. Coblentz, Albert W. Wolff 

Site Expert(s): N/A 

Independent Technical Reviewer: N/A 

Petition Administrative Summary 

Petition Under Evaluation 

Petition # Petition 

Type 

Petition B 

Qualification Date 

DOE/AWE Facility Name 

SEC-00058 83.13 August 9, 2006 Blockson Chemical 

Petitioner Class Definition 

All Atomic Weapons Employer employees, contractors, and subcontractors, who worked in Building 55 at the 

Blockson Chemical Company (also known as Olin Mathieson) from January 1, 1951 to December 31, 1962. 

Proposed Class Definition 

All Atomic Weapons Employer personnel who worked on uranium recovery pilot studies and/or in Building 55 

of the Blockson Chemical Company, Joliet, Illinois, from January 1, 1951 through December 31, 1962. 

Related Petition Summary Information 

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

SEC-00045 83.13 Blockson Chemical Under evaluation 

Related Evaluation Report Information 

Report Title DOE/AWE Facility Name 

NONE 

ORAU Lead Technical Evaluator: [Signature on file] 9/5/06 

Robert M. Coblentz Date 

Peer Review Completed By: [Signature on file] 9/5/06 

Thomas P. Tomes Date 

SEC Petition Evaluation Reviewed By: [Signature on file] 9/5/06 

Jim Neton Date 

SEC Evaluation Approved By: [Signature on file] 9/5/06 

Larry Elliott Date 
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Evaluation Report Summary: SEC-00058, Blockson Chemical 

This evaluation report by the National Institute for Occupational Safety and Health (NIOSH) 

addresses a class of employees proposed for addition to the Special Exposure Cohort (SEC) per the 

Energy Employees Occupational Illness Compensation Program Act of 2000, as amended, 42 U.S.C. 

§ 7384 et seq. (EEOICPA) and 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. 

Petitioner-Requested Class Definition

Petition SEC-00058, qualified on August 9, 2006 requested that NIOSH consider the following class: 

All Atomic Weapons Employer employees, contractors, and subcontractors, who worked in Building 

55 at the Blockson Chemical Company (also known as Olin Mathieson) from January 1, 1951 to 

December 31, 1962. Another petition (SEC-00045) on behalf of a subset of the above-requested class 

of workers was qualified and merged into SEC-00058.

NIOSH-Proposed Class Definition

Based on its research, NIOSH modified the petitioner-requested class to define a single class of 

employees for which NIOSH can estimate radiation doses with sufficient accuracy. The NIOSHproposed class includes all Atomic Weapons Employer personnel who worked on uranium recovery 

pilot studies and/or in Building 55 of the Blockson Chemical Company, Joliet, Illinois, from January 

1, 1951 through December 31, 1962. The work activity definition was modified because Building 55 

was not completed for uranium recovery production until 1952; however, uranium recovery pilot 

studies occurred in 1951. 

Feasibility of Dose Reconstruction

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 incurred by any member of the class; or (2) 

estimate radiation doses more precisely than a maximum dose estimate. 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 proposed class under plausible circumstances 

during the specified period. 

Health Endangerment Determination

Per EEOICPA and 42 C.F.R. § 83.13(c)(3), a health endangerment determination is not required 

because NIOSH has determined that it has sufficient information to estimate dose for the members of 

the proposed class. 
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Table of Contents 

Evaluation Report Summary: SEC-00058, Blockson Chemical ............................................................. 3 

1.0 Purpose and Scope.......................................................................................................................... 7 

2.0 Introduction .................................................................................................................................... 7 

3.0 Petitioner Requested Class/Basis and NIOSH Proposed Class/Basis............................................ 8 

4.0 Data Sources Reviewed by NIOSH................................................................................................ 9 

4.1 Technical Basis Document (TBD) ........................................................................................ 9 

4.2 ORAU Technical Information Bulletin (OTIB).................................................................. 10 

4.3 Facility Employees and Experts.......................................................................................... 10 

4.4 Previous Dose Reconstructions........................................................................................... 12 

4.5 NIOSH Site Research Database .......................................................................................... 13 

4.6 Documentation and/or Affidavits Provided by Petitioners ................................................. 13 

5.0 Radiological Operations Relevant to the Proposed Class ............................................................ 13 

5.1 Blockson Chemical Plant and Process Descriptions........................................................... 14 

5.2 Blockson Chemical Company Functional Areas................................................................. 15 

5.2.1 Recovery of Uranium from Phosphoric Rock......................................................... 15 

5.2.2 Packaging of Uranium Concentrate for Shipment to the USAEC .......................... 15 

5.3 Radiological Exposure Sources from Blockson Chemical Operations............................... 16 

5.3.1 Alpha Particle Emissions......................................................................................... 16 

5.3.2 Beta Radiation Fields .............................................................................................. 16 

5.3.3 Neutron Exposures .................................................................................................. 17 

5.3.4 Photon Exposures.................................................................................................... 17 

6.0 Summary of Available Monitoring Data for the Proposed Class................................................. 18 

6.1 Blockson Chemical Company Internal Monitoring Data.................................................... 18 

6.2 Blockson Chemical Company External Monitoring Data................................................... 18 

6.3 Blockson Chemical Company Air Sampling Data.............................................................. 18 

6.4 Blockson Chemical Company Contamination Monitoring Data......................................... 19 

7.0 Feasibility of Dose Reconstruction for the Proposed Class ......................................................... 19 

7.1 Pedigree of Blockson Chemical Company Data ................................................................. 20 

7.1.1 Internal Dose Data Review...................................................................................... 20 

7.1.2 External Dose Data Review..................................................................................... 20 

7.2 Internal Radiation Doses at Blockson Chemical Company ................................................ 21 

7.2.1 Process-Related Internal Doses at Blockson Chemical Company .......................... 21 

7.2.2 Ambient Environmental Internal Radiation Doses at Blockson Chemical ............. 23 

7.2.3 Internal Dose Reconstruction .................................................................................. 23 

7.2.3.1 Uranium Intakes ....................................................................................... 23 

7.2.3.2 Radon and Radon Progeny ....................................................................... 23 

7.2.3.3 Residual Radioactivity.............................................................................. 24 

7.2.4 Internal Dose Reconstruction Feasibility Conclusion ............................................. 24 
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7.3 External Radiation Doses at Blockson Chemical Company ............................................... 24 

7.3.1 Process-related External Radiation Doses at Blockson Chemical .......................... 24 

7.3.2 Ambient Environmental External Radiation Doses at Blockson Chemical ............ 25 

7.3.3 Blockson Chemical Occupational X-Ray Examinations......................................... 25 

7.3.4 External Dose Reconstruction ................................................................................. 25 

7.3.4.1 Photon Dose.............................................................................................. 25 

7.3.4.2 Electron Dose ........................................................................................... 27 

7.3.4.3 Neutron Dose............................................................................................ 27 

7.3.4.4 Unmonitored Individuals Working in Production Areas.......................... 28 

7.3.4.5 Medical X-ray........................................................................................... 28 

7.3.5 External Dose Reconstruction Feasibility Conclusion............................................ 28 

7.4 Evaluation of Petition Basis for SEC-00058....................................................................... 29 

7.4.1 No Monitoring of Worker Exposures...................................................................... 29 

7.4.2 Particle Size Used Is Not Claimant Favorable ........................................................ 29 

7.4.3 Ingestion of Radioactive Material In Phlegm Not Considered ............................... 30 

7.4.4 Uranium Daughter Beta/Gamma Emitters Not Considered .................................... 30 

7.5 Other Issues Relevant to the Petition Identified During the Evaluation ............................. 30 

7.6 Summary of Feasibility Findings for Petition SEC-00058.................................................. 31 

8.0 Evaluation of Health Endangerment for Petition SEC-00058...................................................... 31 

9.0 NIOSH Proposed Class for Petition SEC-00058.......................................................................... 32 

10.0 References .................................................................................................................................... 33 

Tables 

4-1: No. of Blockson Chemical Co. Claims Submitted Under the Dose Reconstruction Rule ........... 12 

5-1: Blockson Chemical Company Development Chronology ........................................................... 15 

5-2: Default Photon Energies for Blockson Materials......................................................................... 17 

7-1: Uranium Inhalation Intake Rates for Blockson Workers............................................................. 23 

7-2: Radon Exposures for Blockson Workers ..................................................................................... 24 

7-3: Uranium dose rates from drums of yellowcake............................................................................ 26 

7-4: Shallow Dose for Building 55 Workers ....................................................................................... 27 

7-5: Annual Organ Doses From Medical X-rays................................................................................. 28 

7-6: Summary of Feasibility Findings for SEC-00058 ........................................................................ 31 
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SEC Petition Evaluation Report for SEC-00058

1.0 Purpose and Scope 

This report evaluates the feasibility of reconstructing doses for all Atomic Weapons Employer 

personnel who worked on uranium recovery pilot studies and/or in Building 55 of the Blockson 

Chemical Company, Joliet, Illinois, from January 1, 1951 through December 31, 1962. It provides 

information and analyses germane to considering a petition for adding a class of employees to the 

Congressionally-created SEC. 

This report does not provide any determinations concerning the feasibility of dose reconstruction that 

necessarily apply to any individual energy employee who might require a dose reconstruction from 

NIOSH. This report also does not make the final determination as to whether or not the proposed 

class will be added to the SEC (see Section 2.0). 

This evaluation was conducted in accordance with the requirements of EEOICPA, 42 C.F.R. pt. 83, 

and the guidance contained in the Office of Compensation Analysis and Support’s Internal 

Procedures for the Evaluation of Special Exposure Cohort Petitions, OCAS-PR-004. 

2.0 Introduction 

Both EEOICPA and 42 C.F.R. pt. 83 require NIOSH to evaluate qualified petitions requesting that the 

Department of Health and Human Services (HHS) add a class of employees to the SEC. The 

evaluation is intended to provide a fair, science-based determination of whether or not it is feasible to 

estimate with sufficient accuracy the radiation doses of the class of employees through NIOSH dose 

reconstructions.1 

42 C.F.R. § 83.13(c)(1) states: Radiation doses can be estimated with sufficient accuracy if NIOSH 

has established that it has access to sufficient information to 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 if NIOSH has established that it has access to 

sufficient information to estimate the radiation doses of members of the class more precisely than an 

estimate of the maximum radiation dose.

 

Under 42 C.F.R. § 83.13(c)(3), if it is not feasible to estimate with sufficient accuracy radiation doses 

for members of the class, NIOSH must also determine whether or not there is a reasonable likelihood 

that such radiation doses may have endangered the health of members of the class. The regulation 

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 

1

 NIOSH dose reconstructions under EEOICPA are performed using the methods promulgated under 42 C.F.R. pt. 82 and 

the detailed implementation guidelines available at www.cdc.gov/niosh/ocas. 
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not been established, then NIOSH is required to specify that health was endangered for those workers 

who were employed for at least 250 aggregated work days within the parameters established for the 

class or in combination with work days within the parameters established for other SEC classes 

(excluding aggregate work day requirements). 

NIOSH is required to document its evaluation in a report, and in doing so, relies upon both its own 

dose reconstruction expertise as well as technical support from Oak Ridge Associated Universities 

(ORAU). Once completed, the report is provided to the petitioners and to the Advisory Board on 

Radiation and Worker Health (Board). The Board will consider the NIOSH evaluation report, 

together with the petition, petitioner(s) comments, and other information the Board considers 

appropriate, in order to make recommendations to the Secretary of HHS on whether or not to add one 

or more classes of employees to the SEC. Once NIOSH has received and considered the advice of the 

Board, the Director of NIOSH will propose a decision on behalf of HHS. The Secretary of HHS will 

make the final decisions, taking into account the NIOSH evaluation, the advice of the Board, and the 

proposed decision issued by NIOSH. As part of this final decision process, petitioners may seek a 

review of certain types of final decisions issued by the Secretary of HHS.2

 

3.0 Petitioner Requested Class/Basis and NIOSH Proposed Class/Basis 

Petition SEC-00058, qualified on August 9, 2006, requested that NIOSH consider the following class:

All Atomic Weapons Employer employees, contractors, and subcontractors, who worked in Building 

55 at the Blockson Chemical Company (also known as Olin Mathieson) from January 1, 1951 to 

December 31, 1962. 

The petitioner for SEC-00058 stated his belief that accurate dose reconstruction over time is 

impossible because no monitoring was performed. Based on further research, NIOSH deemed the 

petitioner’s submission sufficient to qualify SEC-00058 for evaluation and further consideration by 

NIOSH, the Board, and HHS. Detail regarding the SEC-00058 petition basis is presented below in 

Section 7.4. 

Another petition, SEC-00045, on behalf of a subset of the above-requested class of workers was 

qualified on March 6, 2006 and later merged into SEC-00058. The petitioner for SEC-00045 

provided information and affidavit statements to support his/her belief that accurate dose 

reconstruction over time is impossible. NIOSH deemed the following information and affidavit 

statements sufficient to qualify SEC-00045 for evaluation: 

The petitioner submitted twelve affidavits (from one former Atomic Weapons Employee 

and eleven survivors) to support his/her position that neither the government nor Blockson 

Chemical ever monitored Atomic Weapons Employee exposures to radioactive materials, 

or monitored the workplace for radiation levels. 

2

 See 42 C.F.R. pt. 83 for a full description of the procedures summarized here. Additional internal procedures are 

available at www.cdc.gov/niosh/ocas. 
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The information and statements provided by the petitioner for SEC-00045 qualified the petition for 

further consideration by NIOSH, the Board, and HHS. SEC-00045 was subsequently merged with 

SEC-00058. Details on the SEC-00045 petition basis are included in the discussion in Section 7.4. 

Based on its research, NIOSH modified the petitioner-requested class for SEC-00058 to define a 

single class of employees for which NIOSH can estimate radiation doses with sufficient accuracy. 

The NIOSH-proposed class thus includes all Atomic Weapons Employer personnel who worked on 

uranium recovery pilot studies and/or in Building 55 of the Blockson Chemical Company, Joliet, 

Illinois, from January 1, 1951 through December 31, 1962. The work activity definition was modified 

because Building 55 was not completed for uranium recovery production until 1952; however, 

uranium recovery pilot studies occurred in 1951. 

4.0 Data Sources Reviewed by NIOSH 

NIOSH identified and reviewed numerous data sources to ascertain the availability of information 

relevant to determining the feasibility of dose reconstruction for the class of employees proposed for 

this petition. This included determining the availability of information on personal monitoring, area 

monitoring, industrial processes, and radiation source materials. The following sections summarize 

the data sources identified and reviewed. 

4.1 Technical Basis Document (TBD) 

A Technical Basis Document (TBD) provides specific information concerning the documentation of 

historical practices at the specified site. A dose reconstructor can use the TBD to evaluate internal and 

external dosimetry data for monitored and unmonitored workers, and to serve as a supplement to, or 

substitute for, individual monitoring data. A TBD provides process history information, information 

on personal and area monitoring, radiation source descriptions, and references to primary documents 

relevant to the radiological operations at the site. As part of NIOSH’s evaluation, it examined 

information in the following TBDs for insights into Blockson operations or related topics/operations 

at other sites: 

• Basis for Development of an Exposure Matrix for Blockson Chemical Company, Joliet, Illinois; 

Period of Operation: March 1, 1951 through March 31, 1962, ORAUT-TKBS-0002, Rev. 01; 

June 29, 2004 

• Technical Basis Document for Atomic Energy Operations at Blockson Chemical, Joliet, Illinois, 

OCAS-TKBS-0002; Rev. 00-B; July 19, 2006 (Draft) 

• Y-12 National Security Complex – Occupational Internal Dose, ORAUT-TKBS-0014-5, Rev. 01, 

PC-3, February 14, 2006 

• Technical Basis Document for the Fernald Environmental Management Project (FEMP) – 

Occupational Internal Dose, ORAUT-TKBS-0017-5, Rev. 00; May 28, 2004 
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• Technical Basis Document: Basis for the Development of an Exposure Matrix for Chapman Valve 

Manufacturing, Indian Orchard, Massachusetts, Period of Operation: January 4, 1948 through 

April 30, 1949, ORAUT-TKBS-0033, Rev. 00; February 22, 2005 

4.2 ORAU Technical Information Bulletin (OTIB) 

An ORAU Technical Information Bulletin (OTIB) is a general working document that provides 

guidance concerning the preparation of dose reconstructions at particular sites or categories of sites. 

NIOSH reviewed information in the following OTIBs as part of its evaluation: 

• OTIB: Estimating the Maximum Plausible Dose to Workers at Atomic Weapons Employer 

Facilities, ORAUT-OTIB-0004; Rev. 3 PC-1; November 18, 2005

• OTIB: Dose Reconstruction from Occupationally Related Diagnostic X-ray Procedures, 

ORAUT-OTIB-0006; Rev. 3 PC-1; December 21, 2005

• OTIB: Estimation of Neutron Dose Rates from Alpha-Neutron Reactions in Uranium and Thorium 

Compounds, ORAUT-OTIB-0024; Rev. 00; April 7, 2005

• OTIB: Characterization of Occupational Exposure to Radium and Radon Progeny During 

Recovery of Uranium from Phosphate Materials, ORAUT-OTIB-0043; Rev. 00; January 6, 2006

4.3 Facility Employees and Experts 

Telephone interviews were conducted with five former Blockson Chemical Co. employees to gain 

additional information and insight into the operations associated with uranium processing in Building 

55. The information gained from these interviews has been compiled in NIOSH’s SEC Information 

System (SECIS). These communications are documented under SEC-00058, Non-Submitter 

Communications, SECIS IDs 83 through 87. The primary interview questions were: 

• How many people worked in Building 55? 

• Was uranium extraction work confined to Building 55?

• Did work crews remain constant? 

• How were the drums filled? 

• Was there any localized ventilation used during drum filling? 

• Was the work area cleaned regularly, and how was that done? 

• Were there incidents or spills? 

• Were there any implemented radiological controls? 

• Do you recall any details regarding a uranium urinalysis program? 
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The respondents’ answers are summarized as follows: 

• All respondents described the work crews in Building 55 as small (2 to 6 people) and constant. 

They also confirmed that uranium extraction activities were confined to Building 55. 

• An access security clearance requirement and access control by posted guard was confirmed by all 

but one individual (who had no information regarding clearances or guards). 

• Three out of five respondents had seen uranium drum loading. One thought that there had been a 

loading hopper, while two were certain that the drums were filled by hand-shoveling. 

• Only one individual was certain that there was no localized ventilation in the drum loading area, 

while the other four were unsure. One of those four mentioned a “dust collector,” but could not 

remember where it had been or how it had been used. 

• Three stated that the work area was cleaned regularly (one said each shift), and two of those three 

recalled that the area was swept first, and then washed down using a water hose. 

• None of the five recalled any uranium urinalysis program or any radiological controls program. 

• One individual thought that there had been medical X-rays administered, while the other four did 

not know. 

• Two of the five recalled small, occasional spills which required clean-up. One described spills as 

occurring when he had been involved in changing out cloth screens on the “Kelly Filters.” Some 

of the uranium would fall off of the screens onto the floor and they would have to clean it up. He 

stated that the material was wet at that point in the process. 

• When asked later if there was anything else the respondents thought was important, the individual 

who mentioned the Kelly Filters stated that when changing out the cloth screens, the screens were 

difficult to hold while wearing gloves, so they had to grab them with their bare hands. 
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4.4 Previous Dose Reconstructions 

NIOSH reviewed its dose reconstruction database, NIOSH OCAS Claims Tracking System (NOCTS), 

to locate dose reconstructions under EEOICPA that might provide information relevant to the petition 

evaluation. Table 4-1 summarizes the results of this review for the period of January 1, 1951 through 

December 31, 1962. (Data available as of August 28, 2006) 

Table 4-1: No. of Blockson Chemical Co. Claims Submitted Under the Dose Reconstruction Rule

(January 1, 1951, through December 31, 1962) 

Description Totals 

Total number of claims submitted for energy employees who meet the proposed class definition criteria 113 

Number of dose reconstructions completed for energy employees who were employed during the years 

identified in the proposed class definition 68 

Number of claims for which internal dosimetry records were obtained for the identified years in the 

proposed class definition 0*

Number of claims for which external dosimetry records were obtained for the identified years in the 

proposed class definition 0 

* Data capture efforts identified internal monitoring data for three claimants that match the employment time frame (one based on last 

name and first initial, and two based on last name only). 

NIOSH reviewed each claim to determine whether internal and/or external personal monitoring 

records could be obtained for the employee. At the time that dose reconstructions were performed, 

NIOSH was not able to obtain personnel dosimetry records for any employee represented in an 

individual claim submitted for dose reconstruction under EEOICPA for the time period of January 1, 

1951 through December 31, 1962. However, data capture efforts did locate internal monitoring data 

for 25 former Blockson Chemical employees who were monitored by urinalysis. This is discussed in 

greater detail in Section 7.2.1. Computer Assisted Telephone Interviews (CATIs) were also 

conducted to obtain additional information relevant to the individual claim, such as work locations, 

hours, job titles, and other information. 

As part of the dose reconstruction process, the CATI summaries were carefully reviewed for relevant 

information. Particular attention was given to the interviews of former employees. To the extent that 

they related to the individual claims reviewed for this evaluation, the interviews provided some 

information, such as hours worked, that could be useful for future dose reconstructions. In addition, 

three of the energy employees interviewed indicated that some air monitoring was performed, and two 

other former employees stated there was some sort of external radiation dosimetry monitoring 

performed. However, no record of air or external dosimetry radiation monitoring was found. Most 

interviewees reported that no monitoring of any sort was performed. 
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4.5 NIOSH Site Research Database 

The NIOSH site research database was reviewed to locate documents to support the evaluation of the 

proposed class. Sixteen documents were identified as pertaining to Blockson Chemical. These 

documents were evaluated for their relevance to this petition. The documents include historical 

background on site processes; proposals and contracts with the USAEC; uranium yellowcake 

production totals; FUSRAP activities; and general background documents. The only documents 

containing monitoring data of any kind are several pages of urine sample results for 25 employees 

between the years 1954 and 1958. 

4.6 Documentation and/or Affidavits Provided by Petitioners 

In qualifying and evaluating petitions SEC-00058 and SEC-00045, NIOSH reviewed the following 

documents submitted by the petitioners: 

• (SEC-00058) Petition Form B and supporting information, received May 13, 2006; SECIS 

document ID: 9722 

• (SEC-00045) Petition Form B and supporting information, received January 26, 2006; SECIS 

document ID: 9475 

• (SEC-00045) Twelve affidavits by petitioners, received January 26, 2006; SECIS document ID: 

9477 

The twelve affidavits in support of SEC-00045 and one affidavit in support of SEC00058 were 

provided by two former Atomic Weapons Employee and eleven survivors. Each party provided 

general employee information such as dates and location of employment, and nearly identical 

statements regarding the lack of personnel or area monitoring, and lack of protective gear provided to 

the employee. 

5.0 Radiological Operations Relevant to the Proposed Class 

The following subsections summarize the radiological operations at Blockson Chemical Company 

from January 1, 1951 through December 31, 1962 and the information available to NIOSH to 

characterize particular processes and radioactive source materials. From available sources NIOSH has 

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

radionuclide of concern, and information describing the process through which the radiation 

exposures of concern may have occurred and the physical environment in which they may have 

occurred. The information included within this evaluation report is meant only to be a summary of 

the available information. 
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5.1 Blockson Chemical Plant and Process Descriptions 

The Blockson Chemical Company produced technical grades of sodium phosphate compounds, such 

as disodium and trisodium phosphate, from phosphate rock obtained mainly from Florida sources. 

The naturally-occurring uranium content of the phosphate rock averaged about 0.014% U3O8. In the 

early 1950s, the U.S Atomic Energy Commission (AEC) approached Blockson Chemical Company 

about the possibility of recovering uranium from the phosphate rock they processed (Stoltz, 1958). 

In March 1951, Blockson and the AEC entered into Letter Contract AT (49-1)-606 to build a pilot 

plant to further test and refine the process. In May 1951, Blockson started preliminary 

experimentation to determine the feasibility of this process. Blockson determined that it was 

economically feasible to make the uranium recovery a by-product process designed to fit into their 

normal production of phosphates (Stoltz, 1958). 

From both a process and economic standpoint, using chlorine as an oxidizing agent and then adding 

sodium hydrosulfite to cause precipitation was determined to be the best option (Stoltz, 1953). Based 

on existing production, uranium production capacity was estimated to be 50,000 pounds per year of 

basis uranium oxide (yellowcake) containing 50% to 60% U3O8 (Lopker). 

A second contract, replacing the original contract, was signed October 18, 1951. Under this second 

contract, Blockson constructed a facility (Building 55) at its plant in Joliet, Illinois, capable of 

recovering uranium. This facility was built at Blockson’s expense, with the AEC providing and 

installing the uranium recovery equipment. Blockson was also responsible for both the health and 

safety of workers at the site and for conforming to AEC health and safety regulations (AEC Letter 

Contract AT (49-1)-611). 

Uranium recovery production began August 15, 1952 (Stoltz, 1953). By the end of December 1955, 

Blockson had produced 121,400 pounds of uranium oxide (AEC, 1955). 

In 1955, the Blockson Chemical Company was sold to the Olin Mathieson Chemical Corporation 

which assumed the liabilities and obligations under all Blockson contracts. The contract was amended 

in 1958, primarily to change the pricing structure for uranium. Production was also limited by this 

amendment to no more than 50,000 pounds of uranium concentrate per year starting in 1958 (DOE, 

1985). The 1958 contract also removed the provision that made Blockson responsible for the health 

and safety of the workers. In March 1962, the uranium extraction work ended when the contract 

expired (DOE, 1985). 
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Table 5-1 summarizes Blockson site development. 

Table 5-1: Blockson Chemical Company Development Chronology 

Years Buildings Comments 

1951-1952 Pilot Plant, Building 55 • Pilot Plant constructed and used to evaluate and refine 

the process. 

• Construction of Building 55, a one-story brick building 

of approximately 18,900 ft2

. 

• Production begins in Building 55 on August 15, 1952. 

1955 Building 55 • Contract amended; contract work transferred from 

Blockson Chemical Company to Olin Mathieson 

Chemical Corporation. 

1958 Building 55 • Contract amended which: (1) limited production to 

50,000 lbs uranium concentrate per year; and (2) 

deleted Olin Matheison’s AEC health and safety 

enforcement responsibilities. 

1962 Building 55 • Contract ends; production ceases. 

5.2 Blockson Chemical Company Functional Areas 

Blockson Chemical operations included the following main functional areas: 

• Recovery of uranium from phosphoric acid 

• Packaging of uranium concentrate (yellowcake) into drums for shipment to the AEC 

5.2.1 Recovery of Uranium from Phosphoric Rock 

The initial phases of the uranium recovery process at Blockson were identical to normal phosphate 

production. To recover uranium, phosphate rock is first calcined to remove organic matter, then 

pulverized to a fine material and reacted with sulfuric acid to produce phosphoric acid and 

phosphogypsum. The phosphoric acid (which retains around 70-90% of the uranium) is separated for 

uranium extraction, and the phosphogypsum (which contains most of the radium) is left behind. The 

phosphoric acid is then converted into monosodium phosphate and other phosphorus derivatives. The 

uranium by-product is precipitated from the monosodium phosphate stream. The monosodium 

phosphate liquor is heated and clarified, and then sodium hydrosulfite (Na2S2O4) is added to 

precipitate the uranium. The liquor is filtered and the filtrate is returned to the phosphate processing 

plant. The precipitate, containing about 5% U3O8 is slurried in water in which the uranium is 

re-dissolved. The uranium is then re-precipitated as sodium uranous phosphate. The slurry is filtered 

and the precipitate, known as yellowcake, contains 40 to 60% U3O8. 

5.2.2 Packaging of Uranium Concentrate for Shipment to the USAEC 

In the final packing areas, the essentially-pure uranium compound is dried and packaged in drums for 

shipping, resulting in a potentially-dusty operation (OCAS-TKBS-0002). Follow-up interviews were 

conducted with five former Blockson Chemical employees who were asked to describe the drumloading process. Two described the loading process as that of hand-shoveling the product into drums. 
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One mentioned the use of a hopper, but could not be certain of his recollection. The method used for 

packing the drums is unclear; it may have included manual loading and/or the use of a hopper system. 

5.3 Radiological Exposure Sources from Blockson Chemical Operations 

The primary source of radiological exposure from operations performed at Blockson Chemical 

Company from January 1, 1951 through December 31, 1962 was natural uranium in the form of 

yellowcake, of which 40-60% was U3O8. Potential exposure pathways to be considered include: 

• Internal exposure through inhalation and ingestion of airborne uranium dust 

• Internal exposure from radon and radon progeny 

• External photon dose from drums of uranium yellowcake 

• External photon dose from radium 

• External beta dose from direct exposure to yellowcake material and from uranium skin 

contamination 

• External neutron dose from drums of yellowcake 

5.3.1 Alpha Particle Emissions 

Alpha particle emissions from the radioactive materials handled at Blockson Chemical present the 

greatest potential for exposure through internal deposition via inhalation and ingestion (alpha particles 

do not present an external exposure hazard). The principal alpha-emitting radioactive materials 

associated with Blockson operations were natural uranium in the form of yellowcake which contained 

40 to 60% uranium oxide (U3O8). Natural uranium consists of approximately equal activities of 

uranium-238 (4.20 MeV and 4.15 MeV alpha particles) and uranium-234 (4.77 MeV and 4.72 MeV 

alpha particles). There are smaller amounts of uranium-235 (approximately 1/20 of the activity levels 

of uranium-238 or uranium-234) with alpha particles of 4.40 MeV and 4.36 MeV (Radiological 

Health, 1970). 

Uranium-238 and Ra-226 are essentially in radioactive equilibrium in phosphate rock. During the 

process in which the phosphate rock is pulverized, mixed with sulfuric acid, and separated into 

phosphogypsum and phosphoric acid streams, uranium and radium are chemically separated such that 

the radium is concentrated in the phosphogypsum while the uranium is concentrated in the phosphoric 

acid. The Ra/U activity ratio found in phosphogypsum was about 75, whereas the Ra/U activity ratio 

in the phosphoric acid was only about 0.01 (Roessler, C. E., et al, 1979). It is the phosphoric acid 

stream which was used in the uranium recovery process and that was diverted to Building 55 for 

uranium extraction. Therefore, personnel performing uranium extraction activities at Blockson would 

not have been exposed to the concentrations of radium associated with phosphogypsum. 

5.3.2 Beta Radiation Fields 

The beta dose rate on the surface of yellowcake just after separation is negligible, but rises steadily 

thereafter due to the build-up of uranium-238 decay products protactinium-234 and thorium-234. A 

few months after chemical separation, when equilibrium is reached, the beta dose rate from 

yellowcake is approximately 150 mrad/hr. 
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Former workers describe very dusty workplace conditions and direct handling of yellowcake with no 

protective clothing. Therefore, beta skin dose from skin contamination should also be evaluated. 

5.3.3 Neutron Exposures 

Uranium compounds can be a source of neutrons from both spontaneous fission occurring in the 

isotopes of uranium and from alpha-neutron reactions with low atomic number materials, such as 

oxides and impurities. Neutron exposures from yellowcake, a natural uranium compound, are 

considerably lower than the photon exposures and are, therefore, not significant. ORAU Team 

Technical Information Bulletin, ORAUT-OTIB-0024, describes the expected neutron dose rates from 

the various forms of uranium compounds. In Table 5-2 of that document, the listed neutron dose rate 

at three feet from a source of natural uranium (U3O8) is 8.79E-13 R/hr-gram, with no alpha-emitting 

progeny (Roessler, C. E., et al, 1979). 

5.3.4 Photon Exposures 

Photon exposure rates are about 1.2 mrad/hr in contact with fresh yellowcake, but during the build-up 

of the uranium daughters thorium-234 and protactinium-234 in fresh yellowcake, the radiation levels 

increase somewhat for several months following yellowcake production (NRC, 2002). Photon 

exposure rates are estimated to be approximately 1.0 mrad/h at 30 centimeters from a drum of aged 

yellowcake (OCAS-TKBS-0002, Table 4).

Table 5-2 summarizes default photon energies for Blockson materials. Assignment of a 50%-50% 

distribution of dose from 30-250 keV photons and >250 keV photons is claimant-favorable because 

only approximately 8% of the total dose comes from photons less than 300 keV (OCAS-TKBS-0002). 

Overestimating dose in the 30-250 keV range (compared to >250 keV range) results in a higher 

probability of causation. 

Table 5-2: Default Photon Energies 

for Blockson Materials 

Energy Natural 

Uranium 

<30 keV 0% 

30-250 keV 50% 

>250 keV 50% 
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6.0 Summary of Available Monitoring Data for the Proposed Class 

By the terms of the October 1951 AEC contract, Blockson was responsible for the health and safety of 

workers at the site as well as for conforming with AEC health and safety regulations. However, 

NIOSH has been unable to find evidence of regulatory inspections pertaining to radiological 

conditions. Although urine sample results are available, no evidence of an external dosimetry or area 

monitoring program was found. 

 

6.1 Blockson Chemical Company Internal Monitoring Data 

As discussed in Section 5.3, the primary source of internal radiation exposure at Blockson Chemical 

was uranium dust produced from the drying and loading of yellowcake into containers for transfer to 

the AEC. One hundred twenty-two urine sample results obtained from 25 different employees 

between the years 1954 and 1958 are available. These samples were requested by Blockson and 

analyzed by the AEC New York Operations Office, Health and Safety Division (AEC, 1953). 

It is meaningful to note that while there are urinalyses results for 25 workers, there are 113 dose 

reconstruction claims on file. Based on claimant interviews, the dose reconstructions include workers 

who: (1) did not work in Building 55 during the covered time period; (2) worked in Building 55 on an 

infrequent basis; (3) never worked in Building 55; or (4) worked in Building 55 during the covered 

period as uranium process workers. Other documents on file support the conclusion that the urinalysis 

data include results for workers who had the potential for uranium intakes (see Section 7.2.1). 

6.2 Blockson Chemical Company External Monitoring Data 

NIOSH discovered no evidence of individual external exposure monitoring or area radiation 

monitoring at Blockson Chemical. 

6.3 Blockson Chemical Company Air Sampling Data 

NIOSH discovered no evidence of air sampling during uranium extraction operations at Blockson 

Chemical Company. Air monitoring was performed in between March and November, 1978, as a part 

of a characterization survey conducted by Argonne National Laboratory (ANL). Particulate air 

monitoring was performed and analyzed for both long-lived radionuclides and short-lived particulate 

radon progeny. The survey report states, “The radon decay-product concentrations in air samples 

collected at selected locations in the building, including the areas where contamination was found, 

ranged form 0.0014 to 0.0061 Working Levels (WL), including background......No long-lived 

radionuclides were detected in any air sample.” (ANL, 1978) 
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6.4 Blockson Chemical Company Contamination Monitoring Data 

The only available contamination/radiation monitoring results are from surveys done by ANL between 

March and November 1978. The ANL survey was performed throughout Building 55, including plant 

surfaces, tanks, pipes, and other process equipment. A dose rate was taken at contact and at one meter 

on all 63 locations where contamination was detected. The dose rates at one meter on seven of the 63 

“hot” spots ranged from 0.04 mrad/hr to 0.2 mrad/hr. The other 57 spots had one-meter dose rates 

indistinguishable from background. 

7.0 Feasibility of Dose Reconstruction for the Proposed Class 

The feasibility determination for the proposed class of employees covered by this evaluation report is 

governed by both EEOICPA and 42 C.F.R. § 83.13(c)(1). Under this Act and rule, NIOSH must 

establish whether or not it has access to sufficient information either to 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 to estimate the radiation 

doses to members of the class more precisely than a maximum dose estimate. If NIOSH has access to 

sufficient information for either case, NIOSH would then determine that it was feasible to conduct 

dose reconstructions. 

In determining feasibility, NIOSH begins by evaluating whether current or completed NIOSH dose 

reconstructions demonstrate the feasibility of estimating with sufficient accuracy the potential 

radiation exposures of the class (identified in Section 9.0 of this report). If not, NIOSH systematically 

evaluates the sufficiency of different types of monitoring data, process and source or source-term data, 

which together or individually might allow NIOSH to estimate either the maximum doses that 

members of the class might have incurred, or more precise quantities that reflect the variability of 

exposures experienced by groups or individual members of the class (summarized in Section 7.6). 

Previous dose reconstructions estimate dose by determining the maximum feasible dose using 

claimant-favorable assumptions, and reasonable worst-case scenarios. This approach is discussed in 

the SEC Petition Evaluation Internal Procedures (OCAS-PR-004) available at 

www.cdc.gov/niosh/ocas. The next four major subsections examine: 

• the sufficiency and reliability of the available data. (Section 7.1) 

• the feasibility of reconstructing internal radiation doses. (Section 7.2) 

• the feasibility of reconstructing external radiation doses. (Section 7.3) 

• the bases for petitions SEC-00058 and SEC-00045 as submitted by the petitioners. (Section 7.4) 
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7.1 Pedigree of Blockson Chemical Company Data 

This subsection answers questions that need to be asked before a feasibility evaluation is performed. 

The topic of Data Pedigree addresses the background, history, and origin of the data. It requires 

looking at site methodologies that may have changed over time; primary versus secondary data 

sources and whether they match; and internal data consistency. All these issues form the bedrock of 

the researcher’s confidence and later conclusions about the data’s quality, credibility, reliability, 

representativeness, and sufficiency for determining the feasibility of dose reconstruction. The 

feasibility evaluation presupposes that data pedigree issues have been settled. 

7.1.1 Internal Dose Data Review 

NIOSH has records and data from 122 urine samples from 25 different employees collected from 

April, 1954 to February, 1958 (nineteen employees have multiple samples). Ten records of the 

urinalyses are available, with results for 10 to 14 workers on each report. Standard photofluorometric 

methods were used by the AEC New York Operations Office, Health and Safety Division (AEC, 

1954-58). Results of the samples ranged from 0 to 17 ug of uranium per liter of urine, and detection 

thresholds likely ranged between 2 and 3.8 ug of uranium per liter of urine (HASL-58). 

The original New York Operations Office (NYOO) documentation is available for review and was 

used both to develop the Blockson TBD and in this evaluation. The hard-copy data sheets, provided 

on a standard NYOO form, include the site/plant identification, the individuals sampled, the date(s) of 

the samples, the type of sample, information on the analysis performed, and the analysis results in 

ug/L (handwritten). No other source of information (database or otherwise) has been identified as of 

the time of this evaluation; therefore, a quality check of this data was not possible. 

7.1.2 External Dose Data Review 

NIOSH has been unable to find any record of external dosimetry monitoring of Blockson uranium 

workers. 

Although using a source term is not the preferred method for estimating external worker doses, in the 

absence of personal dosimeter or monitoring data, co-worker data, or area monitoring data, a source 

term with process information may be used to estimate and bound external doses (OCAS-IG-001, 

Table 1.1). The source term present at Blockson can be derived from the AEC monthly production 

reports, the design capacity of the uranium extraction process, contract limits on production, and the 

source term data input into MCNPX (version 2.5.0) for exposure rate calculation from drums of 

yellowcake (AEC, 1955; Lopker; AEC Letter Contract AT (49-1)-611; OCAS-TKBS-0002). A 

claimant-favorable assumption of worker occupancy in the vicinity of the source term can be used to 

bound the external doses. 

NIOSH has not located any documentation regarding AEC-required physical examinations for 

Blockson employees. Nevertheless, several claimants reported that chest X-rays were performed as 

part of either pre-employment or periodic physicals. One claimant reported that he had received chest 

X-rays during work in the “HF” building after he had left Building 55. On this basis, NIOSH would 

assume employees received an annual chest X-ray and use claimant-favorable methods and data to 

estimate related radiation doses (OCAS-TKBS-0002). 
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7.2 Internal Radiation Doses at Blockson Chemical Company 

During chemical processes through which uranium is concentrated, contamination and dust exposures 

are minimal. Such wet chemical processes occur in closed tanks and piping systems. The greatest 

potential for exposure to radioactive materials associated with a uranium recovery process arises in the 

final packing areas. Here the essentially-pure uranium compound is dried and barreled for shipping, 

resulting in a potentially-dusty operation (OCAS-TKBS-0002). 

At Blockson, it is unclear whether engineering controls (e.g., hood or room ventilation) were used to 

lower dust levels during the uranium recovery process. Of the dose reconstruction claimants 

interviewed, one reported that ventilation had been used in Building 55, and one sample analysis 

technician reported that a ventilation hood was always used for work that he performed. There was a 

line item for miscellaneous fans in the summary of cost estimate proposed by Blockson for the 

construction of Building 55; however, details are not available (Lopker). There was no specific lineitem in the proposal for local ventilation of the packing operations. 

The principal source of internal radiation doses for members of the proposed class was uranium dust 

produced from the drying and loading of yellowcake into containers for transfer to the AEC (OCASTKBS-0002). Other sources of internal dose to be considered are from: (1) residual contamination on 

building and equipment surfaces; and (2) radon and radon progeny that may have been present on site. 

7.2.1 Process-Related Internal Doses at Blockson Chemical Company 

The preferred method for estimating internal dose is by urinalysis. Urinalysis results for total uranium

are available for 25 Blockson workers from April, 1954 through February, 1958. The results are 

documented on ten urinalysis reports, with 10 to 14 workers listed on each report. These workers 

include personnel assumed to be exposed to the highest concentrations present at the site (e.g., process 

operators) as well as workers unlikely to be regularly exposed to the highest concentrations.

The urinalysis data reports list the individuals either by last name and first initial or by last name only. 

NIOSH has documentation confirming five individuals as being involved in uranium process work in 

Building 55. Their job titles were: 

• Chemical Operator: Confirmed in NIOSH records as claimant in previous Blockson-related dose 

reconstruction; confirmed in urinalysis report by first and last name; confirmed by CATI 

interview; stated that he scraped dried yellowcake out of the drier and shoveled it into drums; 

stated it was a three-man operation. He said that usually the powder form was processed on day 

shift and the wet processing occurred on night shift. 

• Supervisor: Identified by first and last name by the Chemical Operator listed above as his 

Supervisor during his uranium process work in Building 55; listed by last name and first initial in 

multiple urinalysis results. 

• Chemical Product Analyst: Confirmed in NIOSH records as claimant in previous Blockson-related 

dose reconstruction; confirmed in urinalysis report by an uncommon last-name-only match; job 

title confirmed by CATI interview; stated that he sometimes analyzed uranium samples. 
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• Control Chemist: Confirmed in NIOSH records as claimant in previous Blockson-related dose 

reconstruction; confirmed by last name only on two urinalysis sample results; job title confirmed 

by CATI interview; stated he worked in Building 55 during uranium processing. 

• Filter Operator: Initial and last name match from urinalysis results match the middle initial and 

last name from a former worker providing information in a petition. The former worker stated that 

he worked in Building 55 as a Filter Operator of a device that filtered out the solids in the 

uranium-bearing solution. 

The information above supports the conclusion that urinalysis sampling was performed on those 

individuals who had potential for exposure. The plausible duties of the job titles listed above range 

from those likely have had the most significant exposure (Chemical Operator) to those likely to have 

had the least (Supervisor). The urinalysis data are considered to be that of actual Building 55 uranium 

workers, based on the following: 

• A letter of request from Blockson Chemical to the AEC for personnel urinalysis for “about 20 

workers involved in uranium work” (Barr, 1953) 

• Blockson pre-operational labor estimates listing the need for 18 workers with specified job titles. 

The titles listed included operators, chemists, part time maintenance support, supervisors and 

clerks. (OCAS-TKBS-0002; Lopker) 

• Urinalysis records of 122 samples for 25 workers with five names matching those known to be 

involved in uranium process work in Building 55 

• Three of the workers listed on urinalysis reports having Blockson-related dose reconstructions on 

file 

• One of the three dose reconstruction claimants having performed work that would be considered 

having the highest potential for exposure (loading yellowcake into drums) 

• The assumed workforce size being supported by former Blockson employees’ estimates of the 

Building 55 work force 

Based on review of the available data (i.e., production reports, contract limitations), uranium 

extraction operations performed at Blockson were consistent over the entire operational period. 

Therefore, NIOSH has assumed that the internal monitoring data that exist are representative of the 

personnel exposures that occurred over the entire operational period evaluated in the report. Applying 

this assumption, the sampling that occurred from 1954 through 1958 is representative of the personnel 

exposures at Blockson over the period from 1951 through 1962. 
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7.2.2 Ambient Environmental Internal Radiation Doses at Blockson Chemical 

Ambient environmental dose is accounted for in the assignment of process-related dose. 

7.2.3 Internal Dose Reconstruction 

Workers in Building 55 and related activities were potentially exposed to airborne uranium. Thorium 

(which is assumed to follow the uranium in the Blockson process) and radon are also considered to be 

present. 

7.2.3.1 Uranium Intakes

For dose reconstruction purposes, intake rates that are favorable to claimants are chosen to ensure that 

the maximally-exposed workers are assigned favorable values in the absence of individual monitoring 

information for EEOCIPA claimants. Therefore, production workers would be assumed to have been 

continually exposed at the 95th percentile intake rate of 82 pCi/day, and administrative personnel 

assumed to have been exposed continually at the median intake rate of 25 pCi/day. These bounding 

intakes should be entered into the NIOSH Interactive RadioEpidemiological Program (IREP) as 

constants (OCAS-TKBS-0002). The presence of associated radionuclides that could be present and 

contribute to significant internal dose is assumed (ORAUT-OTIB-0043). Intakes can be assessed by 

either the presumption of inhalation or ingestion. Tissues of the gastrointestinal tract receive larger 

doses from ingestion than from inhalation. Although inhalation is generally considered the most 

common route of occupational intakes, internal dose to tissues of the gastrointestinal tract can be 

bounded by assuming all bioassay results are a result of ingestion of uranium. The results of the 

bioassay analysis are summarized in Table 7-1, based on the presumption of inhalation (OCASTKBS-0002). 

Table 7-1: Uranium Inhalation Intake Rates for Blockson Workers 

Worker category Intake rate 1 Distribution 

Administrative 25 pCi/day total U Constant value 

Administrative 0.35 pCi/day Th-232 and Th-228 2 Constant value 

Production workers 82 pCi/day total U Constant value 

Production workers 1.1 pCi/day Th-232 and Th-228 2 Constant value 

1. Intake rates are normalized to units of calendar days. 

2. Thorium intake rates are derived from ratios in ORAUT-OTIB-0043. 

7.2.3.2 Radon and Radon Progeny

Significant radon levels have been known to exist during uranium extraction operations due to the 

resultant radium concentrations generated during some processes. However, at Blockson, the 

phosphoric acid used for uranium extraction was a by-product of commercial work already being 

conducted. As described in Section 5.1.1, the separation process results in essentially no radium being 

left in the phosphoric acid. Because the acid was the source of the monosodium phosphate being 

pumped to Building 55, there would be no significant levels of radon in Building 55 from the uranium 

operations. However, radon could have been present due to dispersion from other areas (outside of 

Building 55). 
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Radon exposures to workers at phosphate plants have been evaluated for the NIOSH EEOICPA dose 

reconstruction project (ORAUT-OTIB-0043). Because no radon monitoring data are available for the 

period of Blockson uranium operations, the appropriate default values will be assigned. Therefore, for 

reconstructing lung doses, all Blockson workers are to be assigned an exposure of 0.036 WLM 

(working level month) per year due to radon progeny (see Table 7-2). 

Table 7-2: Radon Exposures for Blockson Workers 

Dose component Annual dose/exposure 1 Distribution 

Radon progeny 0.036 WLM (lungs only) Lognormal, GSD=2.0 

Radon progeny 75 rem alpha (ET1 only) 2 Lognormal, GSD=2.0 

Radon progeny 0.30 rem alpha (ET2 only) 2 Lognormal, GSD=2.0 

Radon gas 0.002 rem alpha (non-respiratory 

tract tissues only) 

Constant value 

1. Exposure and dose values are from ORAUT-OTIB-0043. 

2. ET1 and ET2 dose conversion factors are from OCAS-TIB-0011. 

7.2.3.3 Residual Radioactivity

Internal dose from residual contamination is addressed in the Blockson TBD (OCAS-TKBS-0002), 

but is outside the bounds of the timeframe specified in the SEC class definition, and is not addressed 

in this evaluation report. 

7.2.4 Internal Dose Reconstruction Feasibility Conclusion 

This evaluation concludes that dose reconstruction for members of the proposed class is feasible, 

based on: (1) the availability of representative personnel internal monitoring data; and (2) the 

application of 95th percentile doses that are bounding or more accurate than bounding. 

7.3 External Radiation Doses at Blockson Chemical Company 

The principal sources of external radiation doses for members of the proposed class were (OCASTKBS-0002): 

• Drums of yellowcake 

• Medical x-rays 

7.3.1 Process-related External Radiation Doses at Blockson Chemical 

External dosimetry data are not known to exist for Blockson workers, and data capture efforts for the 

EEOICPA dose reconstruction project have not found any direct radiation survey results from the 

Blockson facility. Therefore, source term information has been used to estimate external doses. 

Blockson’s uranium recovery process was a by-product process designed to fit into the existing 

phosphate process (Stoltz, 1958). The primary radionuclides of interest for potential external 

exposure in Building 55 are U-238 and daughter radionuclides Th-234 and Pa-234m. 
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7.3.2 Ambient Environmental External Radiation Doses at Blockson Chemical 

Ambient environmental dose is accounted for in the assigning of process-related dose. 

7.3.3 Blockson Chemical Occupational X-Ray Examinations 

 

Dose from occupationally-required medical X-rays have also been considered and assumed to have 

occurred. 

7.3.4 External Dose Reconstruction 

By the end of August 2006, 113 EEOICPA claims from Blockson Chemical workers had been 

submitted to NIOSH. Of those 113 claims, NIOSH has completed dose reconstructions for 68 claims. 

These claims cover the entire range of operations at Blockson Chemical; however, no indication of 

personnel external radiation exposure monitoring was found. 

There is an established protocol for assessing external exposure when performing dose reconstructions 

(these protocol steps are discussed in the following subsections): 

• Photon Dose 

• Electron Dose 

• Neutron Dose 

• Unmonitored Individuals Working in Production Areas 

• Medical X-ray 

7.3.4.1 Photon Dose

The primary source of photon dose to Blockson workers was from drums of uranium yellowcake. 

Other sources to be considered are photon dose from residual contamination, and from radium. 

Photon Dose from Drummed Yellowcake

The Blockson TBD (OCAS-TKBS-0002) discusses evaluation of photon dose from drums of 

yellowcake. It states: “MCNPX (version 2.5.0) was used to determine the dose rate per curie of 238U 

regardless of the actual activity in the drum. This was later adjusted for actual source activity to 

compare actual dose rates. All radionuclides were ratioed with respect to 238U to determine the 

number of photons and electrons per decay of 238U. Anderson and Hertel showed that the short lived 

nuclides (234Th, 234mPa, 234Pa, and 231Th) are very close to equilibrium (adjusted for branching ratios) 

at 100 days. For the purposes of this evaluation, branching ratio adjusted equilibrium was assumed.” 

ICRP Publication 74 (Table A.1) was used to convert the photon flux to units of air kerma using the 

conversion factors in shown Table 7-3 below. (ICRP 74; OCAS-TKBS-0002) 
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The dose rate was determined at 77.9 cm above the ground, and 30 cm from the edge of the drum for 

both the photon and beta emissions of natural uranium and its progeny. Results are provided in Table 

7-3. 

Table 7-3: Uranium dose rates from drums of yellowcake 

Density of U3O8

(g/cm-3) 

Activity of U in 

drum (Ci) 

Photon emission dose 

(rad/hr) 

Bremsstrahlung 

dose (rad/hr) 

Total dose rate at 

30 cm (rad/hr) 

0.5 * 3.121E-02 3.96E-04 3.20E-04 7.16E-04 

1 6.242E-02 5.00E-04 3.60E-04 8.60E-04 

2 1.248E-01 5.54E-04 3.76E-04 9.30E-04 

4 2.497E-01 5.84E-04 3.84E-04 9.69E-04 

6 3.745E-01 5.84E-04 3.64E-04 9.48E-04 

6.7 4.182E-01 5.81E-04 3.74E-04 9.56E-04 

* The drum begins to noticeably impact the dose rates at low material concentration 

The air kerma dose rates were converted to annual organ doses by assuming a worker’s exposure time 

was lognormally distributed. The median exposure time was determined by assuming all workers 

were working eight hours per day, one day per week at a distance of one foot from the drum. This 

was normalized to 400 hours per work year. The 95th percentile exposure time was determined by 

assuming the worker spent a standard 2000-hour work year at a distance of one foot from the drum. 

This results in a kerma dose distribution with a median value of 0.387 rad per year with a geometric 

standard deviation of 2.7. The dose distribution was assumed to be 50% from photons 30-250 keV 

and 50 % from photons >250 keV. 

For the purposes of calculating organ doses for use in the NIOSH Interactive RadioEpidemiological 

Program (NIOSH-IREP), Monte Carlo methods were used to multiply the whole body doses times the 

triangular organ dose conversion factors found in the NIOSH External Dose Reconstruction 

Implementation Guideline (OCAS-IG-001). The results are annual doses that are lognormally 

distributed. The results are in Table 5 of the Blockson TBD. For skin, the air kerma values were 

multiplied by 1.0. 

Photon Dose from Residual Contamination

Photon dose from residual contamination is addressed in the Blockson TBD (OCAS-TKBS-0002), but 

is outside the bounds of the timeframe specified in the SEC class definition, and is not addressed in 

this evaluation report. 

Photon Dose from Radium 

As stated in Section 5.3.1, the Ra/U activity ratio found in phosphogypsum was about 75, whereas the 

Ra/U activity ratio in the phosphoric acid was only about 0.01 (Roessler, C. E., et al, 1979). 

Therefore, photon dose from radium is not addressed in this evaluation. 
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7.3.4.2 Electron Dose

For accumulations of processed yellowcake dust, the surface beta dose rate from U-238 daughters is 

negligible just after separation, but rises steadily until Pa-234m and Th-234 reach equilibrium 

concentrations. After a few months, the beta dose rate is approximately 150 mrem/hr (OCAS-TKBS0002). 

We have assumed that there was a potential for workers to receive a shallow dose from exposure to 

open drums of yellowcake during drum loading and sealing. The dose rate at one foot from the 

surface of aged yellowcake is between 1-2 mrem/hour. The production workers are assumed to have 

spent eight hours per week, 50 weeks per year, at one foot from the surface of aged yellowcake at a 

dose rate of 2 mrem/hour. This results in a shallow beta dose of 0.8 rem/year. To allow for 

uncertainty, the time of exposure was assumed to be lognormally distributed with the 95th percentile 

exposure time assumed to be 40 hours per week, 50 weeks per year. This shallow dose result 

applicable for dose reconstructions is shown in Table 7-4. The calculated beta dose has not been 

reduced to allow for doses to areas of the skin that are typically covered by clothing (which results in 

a reduction of beta dose to the skin). 

Table 7-4: Shallow Dose for Building 55 Workers 

Dose component Annual dose/exposure Distribution 

Beta dose, E>15 keV 0.8 rem per year Lognormal, GSD=2.7 

It is also assumed that there was a potential for workers to receive a shallow dose from electrons due 

to skin contaminated with yellowcake. The amount of skin contamination can be calculated by using 

the measured deposition velocity of 4-μm particles to skin of 0.012 m/s (Andersson, 2002; Fogh, 

1999), assuming that the material was deposited on the skin for an entire 8-hour shift. The estimated 

amount of skin contamination, combined with electron dose-rate conversion factors for U-238 and 

daughter radionuclides Th-234 and Pa-234m, results in an estimated dose to skin due to electron 

exposure of 0.0018 rem. This skin dose is negligible when compared to the shallow dose estimate 

from exposure to a drum of aged yellowcake discussed in the above paragraph (and shown in Table 7-

4). 

7.3.4.3 Neutron Dose

There is no indication that personnel monitoring for neutrons was performed at Blockson. Technical 

Information Bulletin ORAUT-OTIB-0024 describes the expected neutron dose rates from the various 

forms of uranium compounds. In Table 5-2 of that document, the listed neutron dose rate at three feet 

from a source of natural uranium (U3O8) is 8.79E-13 R/hr-gram, assuming no presence of alphaemitting progeny (Roessler, C. E. et al , 1979). Assuming both that a drum of yellowcake weighs 

1000 pounds, and 2000-hour occupancy, the estimated annual neutron dose would be <0.001 rem. 

This level of exposure is considered insignificant for purposes of dose reconstruction. 
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7.3.4.4 Unmonitored Individuals Working in Production Areas

Records indicate that no personnel were monitored for photon, electron, or neutron doses at Blockson. 

Methods for dose reconstruction are discussed in the preceding sections. 

7.3.4.5 Medical X-ray

Dose from occupationally-required medical X-rays has also been considered and assumed to have 

occurred. For the AEC operational period at Blockson, employees are assumed to have received an 

annual chest X-ray. Organ doses are listed in Table 7-5 and are based on an assumed PosteriorAnterior (PA) exposure with minimal collimation. Dose values are reproduced from Dose 

Reconstruction from Occupationally Related Diagnostic X-ray Procedures (ORAUT-OTIB-0006, 

Table 6-5). The annual doses are applied as dose from 30-250 keV photons using the values in Table 

7-5 as the mean of a normal distribution with a 30% standard deviation. 

Table 7-5: Annual Organ Doses From Medical X-rays 

Organ Annual dose, rem; photon 30-250 keV 

Thyroid 3.48E-02 

Eye/brain 6.40E-03 

Ovaries 2.5E-02 

Liver/gall bladder/spleen 9.02E-02 

Urinary bladder 2.5E-02 

Colon/rectum 2.5E-02 

Testes 5.0E-03 

Lungs (male) 8.38E-02 

Lungs (female) 9.02E-02 

Thymus 9.02E-02 

Esophagus 9.02E-02 

Stomach 9.02E-02 

Bone surfaces 9.02E-02 

Remainder 9.02E-02 

Breast 9.80E-03 

Uterus 2.5E-02 

Bone marrow (male) 1.84E-02 

Bone marrow (female) 1.72E-02 

Skin 2.70E-01*

* Skin dose is for skin in the primary beam. 

7.3.5 External Dose Reconstruction Feasibility Conclusion 

This evaluation concludes that external dose reconstruction for members of the proposed class is 

feasible. By modeling external dose from source term estimates, and by making reasonable exposure 

time estimates which are favorable to the claimant, dose estimates are either bounding or more 

accurate than bounding. 
SEC-00058 Blockson Chemical

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7.4 Evaluation of Petition Basis for SEC-00058 

The following assertions were made on behalf of petition SEC-00058 (and SEC-00045, as notated) 

regarding work at Blockson Chemical Company. Italicized statements are from the specified petition; 

the comments that follow are from NIOSH. 

7.4.1 No Monitoring of Worker Exposures 

SEC-00058: [From petitioner’s Form B statement] “While extracting uranium there was no 

monitoring of dose received, no safety or protective equipment furnished and inadequate ventilation 

in the building. No exposure records were ever kept.” 

SEC-00045: [From the 12 Affidavits] “....that neither the government nor Blockson Chemical ever 

monitored (worker’s) exposure to radioactive materials; that neither the government nor Blockson 

Chemical ever monitored the radiation levels and/or exposure of Building 55 during...” (the proposed 

class dates relevant to this petition). 

NIOSH obtained results from 122 uranium urine samples collected from 25 different workers between 

1954 and 1958. Furthermore, according to a document provided by Blockson to the AEC that 

estimated a breakdown of labor needs for operating Building 55, about 18 people were employed in 

Building 55 operations (OCAS-TKBS-0002; Lopker). The results of the urine monitoring do not 

contain the names of any workers appearing on SEC Petition SEC-00045; however, they do contain 

an initial and last name that matches the middle initial and last name of the petitioner for SEC-00058. 

Additionally, as verified in NOCTS, the results include three workers for which a dose reconstruction 

was performed or initiated. One of the three worked as a Chemical Operator who was involved in 

drum-loading activities with direct handling of yellowcake material. As explained in Section 7.2.1, the 

urine data are considered representative of the potential exposures from the uranium operations being 

performed by Blockson Chemical. It can be concluded that this group of workers was selected because 

they had jobs with a potential for exposure, and includes those individuals with the highest potential 

for exposure, as well as those considered to be only intermittently exposed. 

No evidence of air monitoring or external radiation monitoring during uranium extraction activities 

was found; however, knowledge of the source term and processes can provide a means for estimating 

radiological conditions and external dose for members of the proposed class. 

7.4.2 Particle Size Used Is Not Claimant Favorable 

SEC-00045: Numerous studies have determined that a significant portion of dusts less than 5 micron 

collects in tissue deep in the lungs and can cause significant damage to surrounding tissue. It is not 

clear that the TBD adequately accounts for the accumulation of material in the lungs other than a 

“calculated” chronic intake rate of 24 pCi/day using broad assumptions that do not necessarily 

reflect more recent published research. 

The derived intakes in the Technical Basis Document OCAS-TKBS-0002 are based on the particle 

size recommendations contained in ICRP Publication 66. Calculations using urinalysis data indicate 

that the lung dose from inhalation of 1 micron AMAD particles is marginally higher than the dose 

from inhalation of 5 micron AMAD particles. When derived from bioassay data, the 50-year 
SEC-00058 Blockson Chemical

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committed dose to the lung from the chronic inhalation of 1 micron particles is nominally 15% higher 

than the 5 micron particle dose. In the absence of specific particle size studies, intakes and dose can 

be estimated based on the recommendations of the ICRP (ICRP 66). 

7.4.3 Ingestion of Radioactive Material In Phlegm Not Considered 

SEC-00045: The TBD also appears to fail to account for radioactive material that can be ingested as 

phlegm from previously inhaled matter. 

The amount of material transferred to the gastrointestinal tract from inhaled particles (ingestion as 

phlegm) is included in the ICRP Publication 66 lung model being used for dose reconstructions (ICRP 

66). Material that is ingested (not via inhalation) is also addressed in the Technical Basis Document 

OCAS-TKBS-0002. Ingestion intakes can be bounded by assuming all uranium in urine is the result 

of eating or ingesting uranium. Therefore, the available bioassay data can be utilized to estimate 

bounding doses from ingestion. 

7.4.4 Uranium Daughter Beta/Gamma Emitters Not Considered 

SEC-00045: The 24 pCi/day value does not appear to address the presence of the beta-emitting 

isotopes Th-234 and Pa-234(m). These isotopes have short half-lives of 24 days and a few hours 

respectively. 

Progeny in-growth is addressed in Technical Basis Document OCAS-TKBS-0002 and is assumed to 

have occurred. The dose calculated from intakes of uranium account for the presence of Th-234 and 

Pa-234m. 

7.5 Other Issues Relevant to the Petition Identified During the Evaluation 

During the feasibility evaluation for SEC-00045 (later merged with SEC-00058), one issue was 

identified that required further analysis and resolution. There was a potential for beta dose to worker 

hands from the handling of uranium filter screens without gloves. It was determined that the source 

term information available in the site profile and other sources was sufficient to determine the 

maximum dose that one could receive from direct contact with the uranium yellowcake material. 
SEC-00058 Blockson Chemical

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7.6 Summary of Feasibility Findings for Petition SEC-00058 

This report evaluated the feasibility for completing dose reconstructions for employees at Blockson 

Chemical Company from January 1, 1951 through December 31, 1962. NIOSH found that the 

monitoring records, process descriptions and source term data available are sufficient to complete 

dose reconstructions for the proposed class of employees. 

Table 7-6 summarizes the results of the feasibility findings at Blockson Chemical Company for each 

exposure source for the time period January 1, 1951 through December 31, 1962. 

Table 7-6: Summary of Feasibility Findings for SEC-00058 

January 1, 1951 through December 31, 1962 

Source of Exposure Reconstruction Feasible Reconstruction Not Feasible 

Internal X 

 - Urinalysis (in vitro) X 

External X 

 - Gamma X 

 - Beta X 

 - Neutron X 

 - Occupational Medical x-ray X 

As of June 20, 2006 a total of 113 claims have been submitted to NIOSH for individuals who worked 

at Blockson Chemical. Dose reconstructions are complete for 68 individuals (60%). 

8.0 Evaluation of Health Endangerment for Petition SEC-00058 

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. The regulation 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. 

NIOSH has determined that internal doses can be estimated with sufficient accuracy using the 

available bioassay data, and maximum external doses can be estimated using knowledge of the source 

term and processes at Blockson Chemical. Therefore, this evaluation determined that it is feasible to 
SEC-00058 Blockson Chemical

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estimate radiation dose for members of the proposed class with sufficient accuracy based on the sum

of information available from available resources. Accordingly, it is not necessary to evaluate health 

endangerment. 

9.0 NIOSH Proposed Class for Petition SEC-00058 

Based on its research, NIOSH expanded the petitioner-requested class to define a single class of 

employees for which NIOSH can estimate radiation doses with sufficient accuracy. The 

NIOSH-proposed class includes all Atomic Weapons Employer personnel who worked on uranium 

recovery pilot studies and/or in Building 55 of the Blockson Chemical Company, Joliet, Illinois, from 

January 1, 1951 through December 31, 1962. 

NIOSH has carefully reviewed all material sent in by petitioners for SEC-00058 (and SEC-00045 

which was merged with SEC-00058), including the specific assertions stated in the petitions, and has 

responded to them herein (see Section 7.4). NIOSH has also reviewed the available technical 

resources, and many other references, including the Site Research Data Base (SRDB) for information 

relevant to SEC-00058. In addition, NIOSH reviewed its dose reconstruction database, NIOSH OCAS 

Claims Tracking System (NOCTS), to identify dose reconstructions under EEOICPA 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, it is often feasible to estimate doses by using additional information that might be available, 

such as area monitoring results, information on the radiological sources and the work processes 

involving radiological exposures, and monitoring information from comparable operations at other 

facilities. When using such additional information, radiation estimates typically overestimate, within 

plausible limits, the likely actual exposures and doses of employees at the facility. NIOSH has 

attempted to comply with these standards of performance in determining that it would be feasible to 

reconstruct the dose for the class proposed for this petition. 
SEC-00058 Blockson Chemical

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10.0 References 

42 C.F.R. pt. 81, Guidelines for Determining the Probability of Causation Under the Energy 

Employees Occupational Illness Compensation Program Act of 2000; Final Rule, Federal 

Register/Vol. 67, No. 85/Thursday, Page 22296; May 2, 2002; SRDB Ref ID: 19391 

42 C.F.R. pt. 82, Methods for Radiation Dose Reconstruction Under the Energy Employees 

Occupational Illness Compensation Program Act of 2000; Final Rule; May 2, 2002; SRDB Ref ID: 

19392 

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 

42 U.S.C. §§ 7384-7385 [EEOICPA], Energy Employees Occupational Illness Compensation 

Program Act of 2000, as amended 

OCAS-IG-001, External Dose Reconstruction Implementation Guideline, Rev. 1; Office of 

Compensation Analysis and Support; Cincinnati, Ohio; August, 2002 

OCAS-IG-002, Internal Dose Reconstruction Implementation Guideline, Rev. 0, National Institute for 

Occupational Safety and Health (NIOSH); Cincinnati, Ohio; August, 2002 

OCAS-PR-004, Internal Procedures for the Evaluation of Special Exposure Cohort Petitions, Rev. 0, 

National Institute for Occupational Safety and Health (NIOSH); Cincinnati, Ohio; September 23, 

2004 

OCAS-TIB-0011, Lung Dose Conversion Factor for Thoron WLM, Rev. 2, National Institute for 

Occupational Safety and Health (NIOSH); Cincinnati, Ohio; January 13, 2006 

OCAS-TKBS-0002, Technical Basis Document for Atomic Energy Operations at Blockson Chemical, 

Joliet, Illinois, Rev. 00, National Institute for Occupational Safety and Health (NIOSH); Cincinnati, 

Ohio; June 29, 2006 (Draft) 

ORAUT-OTIB-0004, Estimating the Maximum Plausible Dose to Workers at Atomic Weapons 

Employer Facilities, Rev. 3 PC-1; November 18, 2005 

ORAUT-OTIB-0006, Dose Reconstruction from Occupationally Related Diagnostic X-ray 

Procedures, Rev. 3 PC-1; December 21, 2005 

ORAUT-OTIB-0024, Estimation of Neutron Dose Rates from Alpha-Neutron reactions in Uranium 

and Thorium Compounds, Rev. 00; April 7, 2005 

ORAUT-OTIB-0043, Characterization of Occupational Exposure to Radium and Radon Progeny 

During Recovery of Uranium from Phosphate Materials, Rev. 00; January 6, 2006 
SEC-00058 Blockson Chemical

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ORAUT-TKBS-0002, Basis for Development of an Exposure Matrix for Blockson Chemical 

Company, Joliet, Illinois; Period of Operation: March 1, 1951 through March 31, 1962, Rev. 01; 

June 29, 2004; SRDB Ref ID: 19480 

ORAUT-TKBS-0014-5, Y-12 National Security Complex – Occupational Internal Dose, Rev. 01, 

PC-3, February 14, 2006 

ORAUT-TKBS-0017-5, Technical Basis Document for the Fernald Environmental 

Management Project (FEMP) – Occupational Internal Dose, Rev. 00; May 28, 2004 

ORAUT-TKBS-0033, Technical Basis Document: Basis for the Development of an Exposure Matrix 

for Chapman Valve Manufacturing, Indian Orchard, Massachusetts, Period of Operation: January 4, 

1948 through April 30, 1949, Rev. 00; February 22, 2005 

AEC, 1953, Letter from James A. Barr, Jr., Assistant Director, Domestic Production, Division of Raw 

Materials, to Dr. Richard Fahrner, Medical Consultant, Blockson Chemical Company; September 14, 

1953; SRBD Ref ID 9728, Page 16 

AEC, 1954-58, Urine Sample Results from Analysis Performed by the AEC New York Operations 

Office, Health and Safety Division, 1954 through 1958; SRDB Ref. IDs: 4032 and 9754 (Pages 7, 12, 

14, and 24) 

AEC, 1955, Division of Raw Materials, Domestic Production Phosphates, Office of Domestic 

Procurement, Monthly Report on Activities of Domestic Production Phosphates, USAEC, December 

1955; SRDB Ref ID: 22264 

AEC Letter Contract AT (49-1)-611, Contract between Blockson Chemical and USAEC 

(Amendments 1 and 3 included); October 18, 1951; SRDB Ref ID: 16328 

Andersson, Radiation Dose Implications of Airborne Contaminant Deposition to Humans, Andersson 

K.G., et al; Health Physics 82(2), pages 226-232; 2002 

ANL, 1978, Formerly Utilized MED/AEC Sites Remedial Action Program Radiological Survey of 

Chemicals Group, Olin Corporation (Formerly Blockson Chemical Company), 1978; Argonne 

National Laboratory; 1978; SRDB Ref ID: 23615 

Barr, 1953, Letter from James A. Barr (AEC, NYOO, Division of Raw Materials) to Richard Fahrner, 

Medical Consultant, Blockson Chemical Co.); September 14, 1953; SRDB Ref ID: 9728 

DOE, 1985, FUSRAP Authority Review of the Former Blockson Chemical Company, Joliet, Illinois, 

U.S. Department of Energy; 1985; SRDB Ref ID: 11587, Pages 80-85 

Eidson, Predicted Deposition Rates of Uranium Yellowcake Aerosols Sampled in Uranium Mills, 

Eidson, A.F., and Damon, E.G.; Health Physics, Volume 46, Number 1, Pages 165-176; 1984 
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Fogh, Quantitative Measurement of Aerosol Deposition on Skin, Hair and Clothing for Dosimetric 

Assessment – Final Report; Fogh, C.L., et al; Roskilde, Denmark: Riso National Laboratory; Riso-R1075(EN); 1999; SRDB Ref ID: 14018 

HASL-58, Symposium on Occupational Health Experience and Practices in the Uranium Industry, 

USAEC, Division of Biology and Medicine and the Health and Safety Laboratory; October 15-17, 

1958; SRDB Ref ID: 7886 

ICRP 66, Human Respiratory Tract Model for Radiological Protection, International Commission on 

Radiological Protection (ICRP) Publication 66; 1994 

ICRP 74, Conversion Coefficients for Use in Radiological Protection Against External Radiation, 

International Commission on Radiological Protection (ICRP) Publication 74; 1996 

Lopker, Proposal Letter from E. B. Lopker, Blockson Chemical Company, to Sheldon Wimpfen, Raw 

Materials Operations, USAEC; July 31, 1951; SRDB Ref ID: 9558 

Meyer, Overview of the Fernald Dosimetry Reconstruction Project and Source Term Estimates for 

1951-1988, Meyer, K. R., et al.; Health Physics, Volume 71, Number 4, Pages 433-434, October 1966 

NRC, 2002, Regulatory Guide 8.30, Health Physics Surveys in Uranium Recovery Facilities, Rev. 1, 

U.S. Nuclear Regulatory Commission; May 2002; SRDB Ref ID: 13982 

Radiological Health, 1970, Radiological Health Handbook, Revised Edition; Public Health Service, 

U. S. Department of Health, Education, and Welfare; January 1970; Publicly Available—Not 

Included in SRDB 

Roessler, C. E., et al., Uranium and Radium-226 in Florida Phosphate Materials, Health Physics, 

Vol. 37(3):269-277, 1979 

Stoltz, 1953, Uranium Recovery from Wet Process Phosphoric Acid, RMO-2850, pg. 19; Stoltz, Emil 

M., Jr.; February 23, 1953; SRDB Ref ID: 4027 

Stoltz, 1958, Recovery of Uranium for Phosphate Ores, Proceedings of the 2nd UN Int. Conf. 

PUAE 3, pg. 3; Stoltz, E.M., Jr.; 1958; SRDB Ref ID: 4026 

Wilkinson, Uranium Recovery from Wet Process Phosphoric Acid; History and Present Status; 

Wilkinson, G., Gardinier, Inc.; AJChE, November 1976; SRDB Ref ID: 7255