DRAFT 

ADVISORY BOARD ON RADIATION AND WORKER HEALTH 

NATIONAL INSTITUTE FOR 

OCCUPATIONAL SAFETY AND HEALTH 

A REVIEW OF NIOSH’S PROGRAM EVALUATION REPORT 

OCAS-PER-031, “Y-12 TBD REVISIONS”

Contract No. 200-2009-28555 

SCA-TR-PR2013-0031, Rev. 0 

Prepared by 

Ron Buchanan, PhD, CHP 

SC&A, Inc. 

S. Cohen & Associates 

1608 Spring Hill Road, Suite 400 

Vienna, VA 22182 

July 2013 

Disclaimer 

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

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

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

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

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

information only and that premature interpretations regarding its conclusions are unwarranted.
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However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

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S. COHEN & ASSOCIATES:

Technical Support for the Advisory Board on

Radiation & Worker Health Review of

NIOSH Dose Reconstruction Program

Document No. 

SCA-TR-PR2013-031

Effective Date: 

Draft – July 15, 2013

Revision No.

0 – Draft

A PRELIMINARY REVIEW OF NIOSH’S 

PROGRAM EVALUATION REPORT

OCAS-PER-031, “Y-12 TBD REVISIONS”

Page 2 of 24

Task Manager:

________________________ Date: ___________

Ron Buchanan, PhD, CHP

Supersedes:

N/A

Peer Reviewer(s):

 Hans Behling, PhD, MPH

Project Manager: John Stiver, MS, CHP

________________________ Date: ___________

John Stiver, MS, CHP

Record of Revisions

Revision 

Number

Effective 

Date Description of Revision

0 (Draft) 07/15/2013 Initial issue
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TABLE OF CONTENTS 

Abbreviations and Acronyms ..........................................................................................................4

1.0 Statement of Purpose ...........................................................................................................5

2.0 Subtask 1: Assess NIOSH’s Identification of the Issues and Their Impact on Dose 

Reconstruction .....................................................................................................................7

2.1 Issuance of OCAS-PER-031 ....................................................................................8

2.2 SC&A’s Assessment of the Development of OCAS-PER-031 ...............................9

3.0 Subtask 2: Assess NIOSH’s Specific Methods for Corrective Action .............................10

3.1 SC&A’s Evaluation of Y-12 Technical Basis Documents ....................................10

3.1.1 SC&A’s Previous Evaluation of Y-12 Technical Basis Documents .........10

3.1.2 SC&A’s Current Evaluation of Y-12 Technical Basis Document 

Revisions ....................................................................................................11

3.2 SC&A’s Evaluation of NIOSH’s Corrective Action Plan .....................................11

3.2.1 Issues Identified by SC&A ........................................................................12

3.2.2 Technical Summary ...................................................................................13

3.2.3 Summary of Findings .................................................................................17

3.2.4 Conclusions ................................................................................................18

4.0 Subtask 3: Evaluate the PER’s Stated Approach for Identifying the Number of 

DRs Requiring Re-evaluation ............................................................................................20

5.0 Subtask 4: Conduct Audits of a Sample Set of DRs Affected by OCAS-PER-031 .........21

6.0 References ..........................................................................................................................22

Attachment A – SC&A’s Previous Findings in Y-12 Technical Basis Documents ......................24
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ABBREVIATIONS AND ACRONYMS 

Advisory Board 

 or ABRWH Advisory Board on Radiation and Worker Health 

CFR Code of Federal Regulations 

DOE Department of Energy 

DOL Department of Labor 

dpm disintegration per minute 

DR dose reconstruction 

IMBA Integrated Modules for Bioassay Analysis 

LOD limit of detection 

MDA minimum detectable activity 

mg milligram 

MPLB maximum permissible lung burden 

nCi nanocuries 

NIOSH National Institute for Occupational Safety and Health 

OCAS Office of Compensation Analysis and Support 

ORAUT Oak Ridge Associated Universities Team 

PEP Program Evaluation Plan

PER Program Evaluation Report 

POC probability of causation 

SC&A S. Cohen and Associates (SC&A, Inc.) 

SEC Special Exposure Cohort 

TBD Technical Basis Document 

TIB Technical Information Bulletin 
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1.0 STATEMENT OF PURPOSE 

To support dose reconstruction (DR), the National Institute for Occupational Safety and Health 

(NIOSH) and the Oak Ridge Associated Universities Team (ORAUT) have assembled a large 

body of guidance documents, technical basis documents (TBDs), workbooks, computer codes, 

and tools. In recognition of the fact that all of these supporting elements in DR may be subject to 

revisions, provisions exist for evaluating the effect of such programmatic revisions on the 

outcome of previously completed DRs. Such revisions may be prompted by document revisions 

due to new information, misinterpretation of guidance, changes in policy, and/or programmatic 

improvements. 

The process for evaluating potential impacts of programmatic changes on previously completed 

DRs has been proceduralized in OCAS-PR-008, Preparation of Program Evaluation Reports 

and Program Evaluation Plans, Rev. 2, dated December 6, 2006. This procedure describes the 

format and methodology to be employed in preparing a Program Evaluation Report (PER) and a 

Program Evaluation Plan (PEP). 

A PER provides a critical evaluation of the effect(s) that a given issue/programmatic change may 

have on previously completed DRs. This includes a qualitative and quantitative assessment of 

potential impacts. Most important in this assessment is the potential impact(s) on the Probability 

of Causation (POC) of previously completed DRs with POCs of <50%. 

As needed, a PEP may be issued that serves as a formal notification of an impending PER. The 

PEP provides a preliminary description of the issue(s) that will be addressed in the PER, and 

summarizes the likely scope of the effort required to complete the PER. 

S. Cohen and Associates (SC&A) was tasked by the Advisory Board to conduct a review of 

OCAS-PER-031, Y-12 TBD revisions. In conducting a PER review, SC&A is committed to 

perform the following five subtasks, each of which is discussed in this report: 

Subtask 1: Assess NIOSH’s evaluation/characterization of the “issue” and its potential impacts 

on DR. Our assessment intends to ensure that the “issue” was fully understood and 

characterized in the PER. 

Subtask 2: Assess NIOSH’s specific methods for corrective action. In instances where the PER 

involves a technical issue that is supported by document(s) [e.g., white papers, technical 

information bulletins (TIBs), procedures] that have not yet been subjected to a formal 

SC&A review, Subtask 2 will include a review of the scientific basis and/or sources of 

information to ensure the credibility of the corrective action and its consistency with 

current/consensus science. Conversely, if such technical documentation has been 

formalized and previously subjected to a review by SC&A, Subtask 2 will simply provide 

a brief summary/conclusion of this review process. 

Subtask 3: Evaluate the PER’s stated approach for identifying the universe of potentially 

affected DRs, and assess the criteria by which a subset of potentially affected DRs was 

selected for re-evaluation. The second step may have important implications in instances 
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where the universe of previously denied DRs is very large and, for reasons of practicality, 

NIOSH’s re-evaluation is confined to a subset of DRs that, based on their scientific 

judgment, have the potential to be significantly affected by the PER. In behalf of 

Subtask 3, SC&A will also evaluate the timeliness for the completion of the PER. 

Subtask 4: Conduct audits of DRs affected by the PER under review. Based on information 

contained in the PER (and discussed in Section 5 below), the number of DRs selected for 

audit for a given PER will vary. (It is assumed that the selection of the DRs and the total 

number of DR audits per PER will be made by the Advisory Board.) 

Subtask 5: Prepare a comprehensive written report that contains the results of the above-stated 

subtasks, along with our review conclusions. 
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Health for factual accuracy or applicability within the requirements of 42 CFR 82. 

2.0 SUBTASK 1: ASSESS NIOSH’S IDENTIFICATION OF THE ISSUES 

AND THEIR IMPACT ON DOSE RECONSTRUCTION 

NIOSH has issued six TBDs for the Y-12 site, along with a number of revisions. As stated in 

OCAS-PER-031, these documents have been utilized to perform DRs for claims from the 

National Security Complex (Y-12). Each of these documents has been through several revisions. 

Although many of the revisions only added annotation and attribution or corrected errors that did 

not affect the DR methods, there were a number of substantial changes made that could affect the 

outcome of a DR. In preparation of OCAS-PER-031, the technical changes made in the 

revisions of these documents were reviewed to determine if any previously completed DR would 

result in an increased dose using the current methods. The review was limited to identifying any 

increase in assigned dose, rather than any change or an overall increase. 

A summary of the Y-12 TBDs revisions that are pertinent to the evaluation of OCAS-PER-031

are listed below. 

 ORAUT-TKBS-0014-1 - Introduction – This TBD was revised as follows: 

o 01/06/2004, Rev. 00 

o 11/24/2004, Rev. 00 PC-1

o 10/11/2005, Rev. 00 PC-2

o 10/24/2006, Rev. 01

 ORAUT-TKBS-0014-2 - Site Description – This TBD was revised as follows: 

o 11/19/2003, Rev. 00

o 09/09/2004, Rev. 00 PC-1

o 01/19/2005, Rev. 01

o 10/11/2005, Rev. 01 PC-1

o 10/25/2006, Rev. 01 PC-2

o 11/08/2007, Rev. 02 

 ORAUT-TKBS-0014-3 - Occupational Medical Dose – This TBD was revised as 

follows: 

o 12/15/2003, Rev. 00 

o 09/09/2004, Rev. 00 PC-1

o 10/11/2005, Rev. 00 PC-2

o 04/18/2006, Rev. 00 PC-3

o 06/18/2007, Rev. 01

 ORAUT-TKBS-0014-4 - Occupational Environmental Dose – This TBD was revised as 

follows: 

o 12/05/2003, Rev. 00 

o 05/20/2004, Rev. 00 PC-1

o 09/09/2004, Rev. 00 PC-2

o 10/11/2005, Rev. 00 PC-3

o 07/20/2006, Rev. 01
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 ORAUT-TKBS-0014-5 - Occupational Internal Dose – This TBD was revised as 

follows: 

o 03/17/2004, Rev. 00 

o 05/10/2005, Rev. 01

o 10/11/2005, Rev. 01 PC-1

o 01/12/2006, Rev. 01 PC-2

o 02/14/2006, Rev. 01 PC-3

o 08/03/2006, Rev. 02

o 10/10/2006, Rev. 02 PC-1

o 03/12/2012, Rev. 03

 ORAUT-TKBS-0014-6 - Occupational External Dosimetry – This TBD was revised as 

follows: 

o 11/19/2003, Rev. 00 

o 10/11/2005, Rev. 00 PC-1

o 02/14/2006, Rev. 00 PC-2

o 05/11/2006, Rev. 00 PC-3

o 06/02/2009, Rev. 01

o 12/18/2009, Rev. 02

2.1 ISSUANCE OF OCAS-PER-031 

On December 18, 2007, NIOSH issued OCAS-PER-031, which contained the following major 

sections: 

1. Section 1.0 provides a description of the basis for the issuance of OCAS-PER-031. It 

was determined, after reviewing the Y-12 TBD revisions, that there was the potential for 

increases in previously assigned claimant internal doses.

2. Section 2.0 provides a summary of the potential for increased internal doses associated 

with thorium, as described in the following: 

After evaluating the Y-12 documentation, one issue did arise that could 

increase the dose estimate for some claims. The equilibrium ratio for 

Th-228/Th-232 was changed from assuming 100% equilibrium to assuming 

80% equilibrium. Incorporating this change would increase the dose estimate 

for claims containing a thorium intake determined from chest count data. 

This change was included in revision 1 page change 2 (Rev. 1 PC-2) of the 

internal dose section of the Y-12 TBD (ORAUT-TKBS-0014-5). This change 

was issued on 1/12/2006. 

3. Section 3.0 states that there were 693 Y-12 claims completed prior to the issuance of the 

January 12, 2006, Occupational Internal Dose TBD (ORAUT-TKBS-0014-5) revision 

with a POC <50% and identifies the criterion that will be used to determine if a new dose 

estimate is necessary. 
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2.2 SC&A’S ASSESSMENT OF THE DEVELOPMENT OF OCAS-PER-031

SC&A’s review of the applicable Y-12 TBDs, with their revisions, and OCAS-PER-031

indicates that NIOSH properly outlined the necessary steps to re-evaluate the claims potentially 

impacted by the revisions in the TBDs as proceduralized in OCAS-PR-008, Preparation of 

Program Evaluation Reports and Program Evaluation Plans, Rev. 02. However, SC&A found 

that the recommended method of assigning thorium doses from chest counts at Y-12 is both 

unclear to the dose reconstructors, and technically incorrect, resulting in an underestimate 

of internal dose being assigned from purified thorium intakes. The recorded thorium data 

for Y-12 workers were obtained from the same chest counting method as was used for 

Fernald workers, which was deemed unable to provide sufficient thorium intake 

information and resulted in the issuance of a Special Exposure Cohort (SEC) for Fernald 

in June of 2012.

A detailed analysis of our review is provided in Section 3.0 of this report.
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3.0 SUBTASK 2: ASSESS NIOSH’S SPECIFIC METHODS FOR 

CORRECTIVE ACTION 

In instances where the PER involves a technical issue that is supported by documents [e.g., white 

paper(s), TIB(s), and/or procedure(s)] that have not yet been subjected to a formal SC&A 

review, Subtask 2 will assess the scientific basis and/or sources of information to ensure the 

credibility of the corrective action and its consistency with current/consensus science. 

Conversely, if such technical documentation has been formalized and previously subjected to a 

review by SC&A, Subtask 2 will simply provide a brief summary/conclusion of this review 

process. 

3.1 SC&A’S EVALUATION OF Y-12 TECHNICAL BASIS DOCUMENTS 

In September 2005, SC&A performed a formal review of all six Y-12 TBDs (SC&A 2005), as 

cited in Section 3.1.1 below. Although there have subsequently been numerous page-change 

revisions issued for the Introduction (Section 1), Site Description (Section 2), Occupational 

Medical Dose (Section 3), and Occupational Environmental Dose (Section 4), these changes had 

no impact on dose or the issuance of OCAS-PER-031. In addition, SEC-related revisions 

introduced in Occupational External Dose (ORAUT-TKBS-0014-6) after SC&A’s 2005 review 

do not appear to have any increased dose implications, based on our review of information 

provided in the publication record accompanying each revision. 

However, it was the revision to the Y-12 Occupational Internal Dose (ORAUT-TKBS-0014-5) 

that prompted the genesis of OCAS-PER-031. Therefore, as part of our review of OCAS-PER031, SC&A also performed a technical evaluation of changes introduced in ORAUT-TKBS0014-5 since our 2005 review. This assessment focused on revisions that could potentially 

increase assigned dose as of the issue date (December 18, 2007) of OCAS-PER-031.

3.1.1 SC&A’s Previous Evaluation of Y-12 Technical Basis Documents 

Y-12 Site technical documents relevant to OCAS-PER-031 previously reviewed by SC&A 

(SC&A 2005) include the following: 

 ORAUT-TKBS-0014-1, Technical Basis Document for the Y-12 Site – Introduction. 

November 24, 2004 (Murray 2004a).

 ORAUT-TKBS-0014-2, Technical Basis Document for the Y-12 Site – Site Description. 

January 19, 2005 (Jessen 2005). 

 ORAUT-TKBS-0014-3, Technical Basis Document for the Y-12 Site – Occupational 

Medical Dose. September 9, 2004 (Murray 2004b).

 ORAUT-TKBS-0014-4, Technical Basis Document for the Y-12 Site –Occupational 

Environmental Dose. September 9, 2004 (Ijaz and Adler 2004). 
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 ORAUT-TKBS-0014-5, Technical Basis Document for the Y-12 Site – Occupational 

Internal Dose. May 10, 2005 (ORAUT-TKBS-0014-5 ( 2005a). 

 ORAUT-TKBS-0014-6, Technical Basis Document for the Y-12 Site – Occupational 

External Dosimetry (Kerr 2003).

A short summary of one of SC&A’s findings that is relevant to the evaluation of OCAS-PER031 is provided in Attachment A of this report. 

3.1.2 SC&A’s Current Evaluation of Y-12 Technical Basis Document Revisions 

SC&A reviewed and compared the first three revisions (up to and including the January 12, 

2006, that was used in OCAS-PER-031) of ORAUT-TKBS-0014-5 to identify changes. The 

changes identified were then narrowed down to only those that would impact dose assignments; 

these changes were then further reduced to only those that could potentially result in an increase 

in assigned dose. While performing this task, SC&A identified the following documentation 

errors: 

 The “PUBLICATION RECORD” (or sometimes labeled “RECORD OF 

ISSUE/REVISIONS”) in the front of each ORAUT-TKBS-0014-5 document lists an 

original ORAUT-TKBS-0014-5 version dated March 17, 2004 (Rev. 00). However, this 

first version can not be located on any of the databases searched to date. In view of the 

changes listed for the next version (Rev. 01), the lack of the original version does not 

appear to impact the evaluation of OCAS-PER-031.

 ORAUT-TKBS-0014-5, Rev. 01 PC-1, of October 11, 2005, retains the old issue 

information of Rev. 01, May 10, 2005, in the heading on many pages; instead of the 

correct information of Rev. 01 PC-1, October 11, 2005. This is an error, but would not 

impact the doses assigned. 

 ORAUT-TKBS-0014-5, Rev. 01 PC-2, of January 12, 2006, retains the old issue 

information of Rev. 01, May 10, 2005, in the heading on many pages; instead of the 

correct information of Rev. 01 PC-2, January 12, 2006. This is an error, but would not 

impact the doses assigned. 

SC&A’s page-by-page comparison of the different versions of ORAUT-TKBS-0014-5 did not 

identify any changes that would impact the assigned doses, except for the method of determining 

purified thorium (Th-232 and Th-228) body burdens. Details of this evaluation are provided in 

Section 3.2 below under the corrective action plan.

3.2 SC&A’S EVALUATION OF NIOSH’S CORRECTIVE ACTION PLAN 

According to Section 3.0 of OCAS-PER-031, on December 18, 2007 (the issue date of the PER), 

NIOSH identified 693 Y-12 claims that were completed prior to that date and had a POC below 

50%. NIOSH will review the DRs for each of these 693 claims to determine if the evaluation of 

dose involved exposure to, and intake from, purified thorium. 
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NIOSH will provide the Department of Labor (DOL) with the list of 693 claims, as well as a 

determination for each claim as to whether a new dose estimate is required. Documentation for 

each claim not requiring a new DR will provide the basis for that determination. 

3.2.1 Issues Identified by SC&A 

SC&A was able to confirm that the Th-228/Th-232 ratio of 1:1 was changed to 0.8:1 in the 

January 12, 2006, version of ORAUT-TKBS-0014-5, which concurs with NIOSH’s statement for 

issuing OCAS-PER-031.

As a result of SC&A’s evaluation of the impact of the Y-12 ORAUT-TKBS-0014-5 (2006) 

changes on assigned internal dose, SC&A identified the following findings: 

 Finding #1: Change in Assigned Dose – This change in the Th-228/Th-232 ratio 

would actually reduce the assigned dose, not increase it, if thorium intakes, and resulting 

doses, are based on recorded mg values of thorium from chest counts, as was observed in 

the case files SC&A has reviewed to date. 

 Finding #2: Chest Counts Conversion to Th-232 Body Burden – The method 

NIOSH uses (in both the older ORAUT-TKBS-0014-5 (2005a and 2005b) and the new 

ORAUT-TKBS-0014-5 (2006) versions) to assign Th-232 body burdens assumes that 

the gamma counts obtained during the chest counts are directly related to Th-232 (in mg) 

in the lungs, using an empirically derived calibration factor that applies to all Y-12 

workers at all times. This is incorrect since the gammas from Ac-228 and Pb-212 are 

being counted, and (1) Ac-228 is not in equilibrium with Th-232, (2) Pb-212 is not in 

equilibrium with Th-228, and (3) Th-228 is not in equilibrium with Th-232. 

Additionally, a given equilibrium cannot be assumed because it is constantly changing 

for many years after the purification of thorium. 

 Finding #3: Different Solubility of Thorium and Decay Products in the Lung – The 

lung may retain thorium, being relatively insoluble, longer than the more soluble decay 

products in some cases. Therefore, a lung count based on the decay product (i.e., 

Ac-228 and/or Pb-212) would not necessarily have a consistent relationship to the 

thorium (Th-232 and/or Th-228) body burden. Additionally, the solubility of the decay 

products themselves (inhaled or formed in the lungs) may have different solubility and 

not have consistent ratios.

 Finding #4: MDA or LOD Value – NIOSH assumed a Ra-228 to Th-232 ratio of 0.6 

[page 31 of ORAUT-TKBS-0014-5, Rev. 01 PC-2 (2006)] for determining the minimum 

detectable activity (MDA) of 0.6 nCi; this would require approximately 8 years from 

purification to counting. This is not a valid assumption for almost all workers and is not 

constant between each chest count. The limit of detection (LOD) value was not directly 

based on counting statistics, but it was empirically derived and meant to be used only as 

a screening tool, not to accurately assign dose (West 1965, Scott 1961). 
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In order to fully understand the basis for these findings, a brief technical summary of the 

detection and assignment of purified thorium body burdens is provided. 

3.2.2 Technical Summary 

The purified thorium project at Y-12 consisted of receiving thorium from outside sources that 

had recently been purified to remove all but the thorium product, which would consist of Th-232 

and Th-228 in equilibrium at the time of purification. The Th-228 activity (with a half-life of 

1.9 years) would then decrease faster than the Th-232 (with a half-life of 1.4E10 years), and the 

Th-228 would grow back in through the Th-232 → Ra-228 (T1/2 = 5.7 years) → Ac-228 → 

Th-228 decay chain. 

Thorium Decay Chain 

Figure A illustrates the thorium decay chain (West 1965, page 11); note the 5.7 year half-life of 

Ra-228. 

Figure A. Decay Chain of Thorium (from West 1965)

Radionuclide Activity After Thorium Purification 

Figure B illustrates the activity of various radionuclides in the thorium decay chain after 

purification of thorium (West 1965, page 13). Figure 5-4, page 31, of ORAUT-TKBS-0014-5

(2006) is similar, but Figure B contains more details; note that the Ra-228 activity ranges from 

near zero to 10% of the Th-232 activity during the first year. 
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Figure B. Decay and Ingrowth of Various Radionuclides after Purification of Thorium 

(from West 1965)

Chest Count Gamma Energy Spectra 

Figure C below illustrates the gamma spectrum from a chest counter showing (1) a person with 

no thorium body burden (lower curve), and (2) the simulated spectrum of a worker with a lung 

burden of thorium in the upper curve (West 1965, page 13). 

Figure C. Gamma-ray Energy Spectra from Chest Counter (from West 1965) 
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According to West 1965, page 25, a Th-228/Th-232 (not Th-238 as in the text) ratio of 0.8 and a 

Ra-228/Th-232 ratio of 0.6 was assumed. This corresponds to the calibration source, quoted in 

an article by Scott (1966), that was used in deriving the empirical calibration factor of 8.84 mg 

thorium per sum of net count ratios, as quoted in a 1961 article by Scott (1961). These ratios 

are also quoted on page 31 of ORAUT-TKBS-0014-5 (2006). The details of how the empirically 

derived calibration factor for the chest counter was obtained are not provided in any of these 

documents (i.e., the placement of the standard source, counting statistics, etc.). However, a Ra228/Th-232 ratio of 0.6 (corresponding to approximately 8 years after purification) would neither 

be applicable nor constant for Y-12 personnel working with purified thorium and being chest 

counted every 6 months. 

Y-12 DOE Recorded Chest Count Data 

SC&A’s preliminary review of a few of the Y-12 claimant files identified five cases that had 

chest count data recorded. Of these five cases, four Department of Energy (DOE) files recorded 

the chest count results as mg of thorium during the period 1961–1974, and one DOE file 

recorded the chest count results as nCi of Ac-228 in 1995. These were the only quantities listed; 

no Pb-212 or other related data were provided in the DOE files. 

DR Use of DOE Recorded Thorium Data 

SC&A analyzed the methodology used by NIOSH in these five cases. The specific activity of 

Th-232 is 0.11 nCi/mg, which corresponds to 244.2 dpm/mg; this is the conversion factor SC&A 

found in some of the DR worksheets. The following table summarizes the different DR 

methodologies SC&A found in analyzing the five cases: 

Table 1. Units in DOE Records and DR Methodologies Found in Five DR Cases 

Year of DR 

Report

Years

of bio

Units in

DOE records

Th-232 

used in DR*

Th-228 

used in DR*

Correct per 

PER-031

2005 & 2009 1971 Thorium (mg) 60% 40% No

2006 1964–1974 Thorium (mg) 100% 80% Yes

2006 1961–1963 Thorium (mg) 100% 80% Yes

2007 1968 Thorium (mg) 100% 80% Yes

2010 1995 nCi Ac-228** 100% 25% No

*Percent of IMBA-derived Th-232 intake from bioassay/MDA data. 

**DR assumed Th-232/Ac-228 ratio of 1:1 in the input to the IMBA program. 

These methods are not consistent, technically correct, or claimant favorable. 

MDA or LOD Value 

A brief treatment of the MDA value is provided on page 31 of ORAUT-TKBS-0014-5 (2006),

but no detailed analysis is presented. The LOD of 0.6 nCi, for screening purposes, was derived 

in a fairly complex way in the Scott 1961 and the West 1965 documents.

MDA Value as Derived by NIOSH – From page 31 of ORAUT-TKBS-0014-5 (2006), it 

appears that NIOSH derived an MDA value of 0.6 nCi by assuming a Th-228/Th-232 ratio of 0.8 

[from the Th-228/Th-232 ratio of 80% at 1 year shown in Figure 5-4 on page 31 of ORAUTTKBS-0014-5 (2006)], which corresponds to a maximum permissible lung burden (MPLB) of 
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3.2 nCi Th-232, as per Figure 2 on page 13 of the West 1965 document. A Ra-228/Th-232 ratio 

of 0.6 was then assumed, as stated on page 31 of ORAUT-TKBS-0014-5 (2006). (According to 

Figure B above, this would correspond to an elapsed period of approximately 8 years, which is 

not acceptable for DR purposes, as will be discussed later.) The MDA value of 20% of MPLB 

was then taken from West 1965, page 26, and applied to the 3.2 nCi Th-232 to derive an MDA of 

0.2 × 3.2 nCi = 0.6 nCi Th-232. This would correspond to 0.6 nCi × (1/0.11 nCi/mg) = 5.5 mg 

Th-232. 

Limit of Detectability Derived in Scott 1961 and West 1965 Documents – Pages 25–26 of the 

West 1965 document outline a method that could use the chest count results for an indication of 

thorium uptakes, and states a “...limit of detectability” of about 20% of the MPLB, using certain 

assumptions (i.e., Ra-228/Th-232 ratio of 0.6 and a Th-228/Th-232 ratio of 0.8); but states that 

the sensitivity “...is dependent upon the ratios of the Th-232 and Ra-228 to the daughters being 

measured.” West 1965 further states: 

Because of this dependency on daughters, a quantitative estimate of thorium or 

radium is difficult because it depends upon a knowledge of the relationship 

between the daughters and these parents. 

The main purpose of the work leading to the 1965 West article was to document that safeguards 

were in place at Y-12 such that workers were not receiving a significant lung burden of thorium 

from the purified thorium project. This article was not designed to assign lung burdens and 

resulting doses for determination of compensation. SC&A’s understanding of the methodology 

used in the West 1965 document to illustrate some sort of detection limit for screening (under 

certain conditions) is as follows: 

The LOD value of 20% of MPLB (0.2 × 3.2 nCi = 0.6 nCi; and 0.6 nCi × 1.0 mg/1.1E-1 nCi = 

5.5 mg thorium) was derived by: 

 Using the results of counting 1,100 persons not exposed to thorium to obtain the gamma 

energy spectrum represented by the lower curve in Figure C above (Figure 13 on page 13 

of West 1965). The sum of the ratio of the thorium peak counts to the adjacent higherenergy region counts for the three major peaks was 3.23 ± 0.7. 

 The gamma energy spectrum in the upper curve of Figure C was simulated as an 

individual with a lung burden (the amount of lung burden was not stated). The details of 

how this spectrum was obtained were not presented in the West 1965 document; only that 

the following conditions were assumed: 

 A Th-228/Th-232 ratio of 0.8 (from the Th-228/Th-232 ratio of 80% at 6 months) 

as shown in Figure B (Figure 2 on page 13 of West 1965), which corresponds to a 

MPLB of 3.2 nCi. 

 A Ra-228/Th-232 ratio of 0.6, as stated on page 25 of West 1965 (according to 

Figure B, this would correspond to an elapsed period of approximately 8 years, 

which is not acceptable for DR purposes, as is discussed later). 
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 An empirically derived conversion factor was created by summing the ratio of the counts 

in one Pb-212 and two Ac-228 gamma energy peaks to those in the next higher energy 

region of each peak, and then subtracting out the sum of these same ratios from the 1,100 

workers with no industrial thorium intakes. The resulting ratio is then multiplied by a 

factor of 8.84 mg thorium. This is illustrated below: 

Note: The method used to derive the factor of 8.84 mg thorium is not provided. 

 According to the West 1965 article, page 26, the sum of the ratios of the background 

Pb-212 and Ac-228 peaks counts to the adjacent higher-energy region counts for the 

1,100 workers was 3.23 + 0.7 at the 95th percentile confidence interval, and a rise of 

0.7 represents about 20% of one MPLB. Therefore, the corresponding LOD was derived 

as follows: 

LOD = 0.20 × 3.23 nCi = 0.6 nCi = 5.5 mg = 1,332 dpm 

Note: Details on how an increase in the sum of the ratios by 0.7 represents 20% of 

the MPLB are not provided.

3.2.3 Summary of Findings 

As discussed above, SC&A has identified four findings regarding the technical merit of changes 

introduced in ORAUT-TKBS-0014-5, Rev. 01 PC-1, which resulted in the issuance of OCASPER-031. These findings are summarized below: 

Finding #1: Change in Assigned Dose – The change in the Th-228/Th-232 ratio from 1:1 to 

0.8:1 would actually reduce the assigned dose, not increase it, if thorium body burdens are based 

on chest counts [i.e., using 80% of the Th-232 intake to assign Th-228 intake will result in a 

lower body burden (and dose) than using the previous value of 100%]. The only instance where 

a Th-228/Th-232 ratio of 0.8/1.0 would increase the overall dose is if only the counts from 

Pb-212 were used to determine the Th-228 body burden, and then the Th-232 body burdens were 

derived from those results. This method was not used by NIOSH and cannot be used with the 

data provided in the DOE records because the detail of the gamma energy spectrum counts is not 

recorded. 

Finding #2: Chest Counts Conversion to Th-232 Body Burden – The method NIOSH uses 

[in both the older ORAUT-TKBS-0014-5 (2005a and 2005b) and the new ORAUT-TKBS-0014-

5 (2006) versions] to assign Th-232 body burden most likely assumes that the Pb-212 and Ac228 counts obtained during the chest counts are directly related to Th-232 in the lungs on a 

consistent basis. This is incorrect because the gammas from Pb-212 and Ac-228 are actually 

being counted and then recorded as mg of thorium, or nCi of Ac-228. However, by definition, 

purified thorium less than 1-year old is not in equilibrium with the parent Th-232 because the 

Ra-228 in the decay chain has a half-life of 5.7 years (see Figure A). The use of an Ac-228/Th-
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232 ratio of 1.0 would require an elapsed period over 30 years (see Figure B) because of the Ra228 half-life of 5.7 years; even the use of an Ac-228/Th-232 ratio of 0.6 would require an 

elapsed period of approximately 8 years. Both time periods are too long for Y-12 personnel 

working with purified thorium during the first year after receipt. The Ac-228/Th-232 ratio 

ranges from near zero to 10% during the first year (see Figure B), with a value of approximately

6% at 6 months; this would increase the assigned dose by a factor of 10, when compared to using 

an Ac-228/Th-232 ratio of 0.6. Additionally, chest counts taken at later times will have a 

different Ac-228/Th-232 ratio because of Ra-228 ingrowth. Therefore, the most important issue 

is not the Th-228/Th-232 ratio, but the unknown (and changing) Ac-228/Th-232 ratio when 

using chest count data derived from counting Ac-228 gamma rays. A similar analysis applies to 

the Pb-212 counts.

Finding #3: Different Solubility of Thorium and Decay Products in the Lung – The lung 

may retain thorium, being relatively insoluble, longer than the more soluble decay products in 

some cases. Therefore, a lung count based on the decay product (i.e., Ac-228 and/or Pb-212) 

would not necessarily have a consistent relationship to the thorium (Th-232 and/or Th-228) body 

burden.

Finding #4: MDA or LOD Value – To attain a Ra-228 to Th-232 ratio of 0.6 [page 31 of 

ORAUT-TKBS-0014-5 (2006)] for determining the MDA of 0.6 nCi would require 

approximately an 8-year period from purification to counting. This is not a valid assumption for 

most workers and is not constant between each chest count.

3.2.4 Conclusions

SC&A finds the use of OCAS-PER-031 and the Y-12 ORAUT-TKBS-0014-5 (2006) thorium 

dose assignment procedures to be inappropriate for the following reasons:

 Neither OCAS-PER-031, nor the ORAUT-TKBS-0014-5 (2006) it is based on, is 

technically correct.

 The application of OCAS-PER-031 in past DRs that have been reviewed is incorrect and 

inconsistent in many cases.

 The application of OCAS-PER-031 and ORAUT-TKBS-0014-5 (2006) (as worded) 

actually decreases the assigned thorium dose compared to the previous method.

 Changes in the thorium equilibrium ratios using original count data cannot be performed 

because the raw count data are not recorded in the DOE files.

 A consistent relationship between thorium and decay products cannot be assumed in the 

lung because of possible changes in solubility.

 The assumptions of a constant Th-238/Th-232 ratio of 0.8 and a Ra-226/Th-232 ratio of 

0.6 made in deriving the calibration factor and MDA value are not applicable to 

personnel working with purified thorium at Y-12 during the first year, and having chest 

counts every 6 months.
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It is also relevant to compare the similarities of the chest-counting equipment and data 

collected/recorded for the Y-12 facility to that of the Fernald facility. Y-12 equipment and 

counting techniques were used at the Fernald facility; however, as the result of numerous 

reviews and analyses (as summarized in SC&A 2012), it was determined that the thorium data 

for Fernald were not adequate to allow for sufficient accuracy in DR and an SEC was granted in 

2012 for the period 1968–1978 for all workers at Fernald. The same issues are pertinent to the 

Y-12 thorium chest-counting data.
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4.0 SUBTASK 3: EVALUATE THE PER’s STATED APPROACH FOR 

IDENTIFYING THE NUMBER OF DRs REQUIRING 

RE-EVALUATION 

Section 3.0 of OCAS-PER-031 identified the set of criteria used to determine the total population 

of claims that had the potential of being affected by changes in the Y-12 TBDs. At the time that 

OCAS-PER-031 (2007) was issued, NIOSH identified 693 Y-12 claims that were completed 

prior to that date and had a POC below 50%. This established an upper-bound estimate of the 

number of claims that may be impacted. NIOSH intends to screen these claims to determine if 

the evaluation of dose involved any of the methods outlined in Section 3 of this report 

concerning NIOSH’s corrective action plan.

The application of these screening criteria will undoubtedly exclude many of the 693 potential 

claims from impacts associated with OCAS-PER-031 and the need for the reconstruction of the 

organ dose. However, until NIOSH reviews all of these claims, the actual number of cases that 

will be affected by OCAS-PER-031 and require a new dose assessment remains unknown.

In addition, based on the outcome of the findings identified as a result of our technical review of 

ORAUT-TKBS-0014-5 (2006), there may be a need to cancel OCAS-PER-031 and reissue a 

PER after this document is appropriately revised.
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5.0 SUBTASK 4: CONDUCT AUDITS OF A SAMPLE SET OF DRs

AFFECTED BY OCAS-PER-031

In behalf of the four subtasks evaluated under OCAS-PER-031, SC&A identified four findings 

that question the technical merit of the Y-12 Occupational Internal Dose TBD and corrective 

actions taken by NIOSH in OCAS-PER-031.

SC&A recommends that the selection of Subtask 4 cases be delayed until the Subcommittee on 

Procedures Review can further investigate SC&A’s findings and concerns.
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6.0 REFERENCES

42 CFR 82, 2002. Methods for Radiation Dose Reconstruction under the Energy Employees

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

Register/Vol.67, No. 85/Thursday, May 2, 2002, p. 22314.

Ijaz, T. and Adler, T.C. 2004. Technical Basis Document for the Y-12 National Security

Complex – Occupational Environmental Dose ORAUT-TKBS-0014-4, Rev. 00 PC-2, Oak

Ridge Associated Universities, Oak Ridge, Tennessee, September 9, 2004.

Jessen, K. 2005. Technical Basis Document for the Y-12 National Security Complex – Site

Description ORAUT-TKBS-0014-2, Rev. 01, Oak Ridge Associated Universities, Oak Ridge,

Tennessee, January 19, 2005.

Kerr, G.D. 2003. Technical Basis Document for the Y-12 National Security Complex –

Occupational External Dosimetry, ORAUT-TKBS-0014-6, Rev. 00, Oak Ridge Associated

Universities, Oak Ridge, Tennessee, November 19, 2003.

Murray W.E. 2004a. Technical Basis Document for the Y-12 National Security Complex – Y-12

Site Profile ORAUT-TKBS-0014-1 Rev. 00, PC-1, Oak Ridge Associated Universities, Oak

Ridge, Tennessee, November 24, 2004.

Murray, W.E. 2004b. Technical Basis Document for the Y-12 National Security Complex –

Occupational Medical Dose, ORAUT-TKBS-0014-3, Rev, 00, Oak Ridge Associated

Universities, Oak Ridge, Tennessee, September 9, 2004.

OCAS-PR-008. 2006. Preparation of Program Evaluation Reports and Program Evaluation 

Plans, Rev. 02, NIOSH’s Office of Compensation Analysis and Support, Cincinnati, Ohio. 

December 6, 2006.

OCAS-PER-031. 2007. Y-12 TBD Revisions, Rev. 00, National Institute for Occupational 

Safety and Health, Office of Compensation Analysis and Support, Cincinnati, Ohio. December 

18, 2007.

ORAUT-TKBS-0014-1. 2006. Technical Basis Document for the Y-12 – Introduction, Rev. 01, 

Oak Ridge Associated Universities Team, Cincinnati, Ohio. October 24, 2006.

ORAUT-TKBS-0014-2. 2006. Technical Basis Document for the Y-12 – Site Description, Rev. 

01 PC-2, Oak Ridge Associated Universities Team, Cincinnati, Ohio. October 25, 2006.

ORAUT-TKBS-0014-3. 2006. Technical Basis Document for the Y-12 – Occupational Medical 

Dose, Rev. 00 PC-3, Oak Ridge Associated Universities Team, Cincinnati, Ohio. April 18, 

2006.
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However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

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

ORAUT-TKBS-0014-4. 2006. Technical Basis Document for the Y-12 – Occupational

Environmental Dose, Rev. 01, Oak Ridge Associated Universities Team, Cincinnati, Ohio. July 

20, 2006.

ORAUT-TKBS-0014-5. 2005a. Technical Basis Document for the Y-12 – Occupational 

Internal Dose, Rev. 01, Oak Ridge Associated Universities Team, Cincinnati, Ohio. May 10, 

2005.

ORAUT-TKBS-0014-5. 2005b. Technical Basis Document for the Y-12 – Occupational 

Internal Dose, Rev. 01 PC-1, Oak Ridge Associated Universities Team, Cincinnati, Ohio. 

October 11, 2005.

ORAUT-TKBS-0014-5. 2006. Technical Basis Document for the Y-12 – Occupational Internal 

Dose, Rev. 01 PC-2, Oak Ridge Associated Universities Team, Cincinnati, Ohio. January 12, 

2006.

ORAUT-TKBS-0014-5. 2012. Technical Basis Document for the Y-12 – Occupational Internal 

Dose, Rev. 03, Oak Ridge Associated Universities Team, Cincinnati, Ohio. March 12, 2012.

ORAUT-TKBS-0014-6. 2006. Technical Basis Document for the Y-12 – Occupational External 

Dose, Rev. 00 PC-3, Oak Ridge Associated Universities Team, Cincinnati, Ohio. May 11, 2006.

SC&A. 2005. Y-12 National Security Complex Site Profile Review. SCA-TR-TASK1-0007, S. 

Cohen & Associates, McLean, Virginia, and Saliant Inc., Jefferson, Maryland. September 19, 

2005.

SC&A. 2012. Lipsztein, J., SC&A Final Position on the Th-232 In-vivo Data Quality and 

Adequacy for FEMP Workers. S. Cohen & Associates, Vienna, Virginia. January 30, 2012.

Scott, L. 1961. Internal Correspondence: Rule of Thumb for Computing Thorium Body Burden 

From In Vivo Counts. L. Scott to C. West. Union Carbide Nuclear Company, Oak Ridge, 

Tennessee. November 21, 1961.

Scott, L. 1966. A Technique of Assessing Thorium Body Burdens Utilizing in vivo Gamma 

Spectrometry. Health Physics, Pergamon Press, 1966. Vol. 12, pp. 101–103. Printed in 

Northern Ireland.

West, C.M., 1965. Health Physics Considerations Associated with Thorium Processing. Y-KB53, Union Carbide Corporation, Oak Ridge, Tennessee, January 19, 1965.
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ATTACHMENT A – SC&A’S PREVIOUS FINDINGS IN 

Y-12 TECHNICAL BASIS DOCUMENTS

On September 19, 2005, SC&A issued a draft report (SC&A 2005) SCA-TR-TASK1-0007 titled,

Y-12 National Security Complex Site Profile Review. This draft report presents SC&A’s 

evaluation of the National Institute for Occupational Safety and Health (NIOSH) Site Profile for 

the Y-12 National Security Complex, which was issued as six separate technical basis documents 

(TBDs) numbered ORAUT-TKBS-0014-1 through ORAUT-TKBS-0014-6.

The finding most relevant to the evaluation of OCAS-PER-031 is stated on page 72 of that 

document (SC&A 2005):

The TBD should provide additional information to the dose reconstructor relating 

to operations involving thorium and its daughters, including consideration of 

concentrating daughter products during processing and waste management. 

Chemical and metallurgical processes can displace the equilibrium existing in the 

original source material. Further guidance on when to assign thorium uptakes 

and what default assumptions should be used during various phases of thorium 

processing should be provided. [Emphasis added.]

SC&A’s current evaluation of the Y-12 ORAUT-TKBS-0014-5 (2006) document and PER-031 

concurs with this statement.