Memo to RFP Work Group Re: Mg-Th 1 SC&A – September 11, 2014

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

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

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

MEMO

TO: Rocky Flats Plant Work Group

FROM: Joe Fitzgerald, SC&A

SUBJECT: Response to NIOSH Regarding the Existence of Mg-Th Alloy at RFP

DATE: September 11, 2014

INTRODUCTION

This is in response to the August 13, 2014, NIOSH Response Paper titled, Existence of Mg-Th 

Alloy at RFP Based on Worker Statements, Rev. 1, by J.S. Bogard and Dan Stemfley of Oak 

Ridge Associated Universities Team (ORAUT). As noted in this paper, SC&A originally raised 

the possibility of Mg-Th alloy being received by the Rocky Flats Plant (RFP) in 2006 during the 

Special Exposure Cohort (SEC) evaluation report review being conducted for Petition SEC00030, during which SC&A found that “it is clear from NUREG-1717 and the other 

considerations presented above that knowledge of the approximate quantities, periods, and 

processing status of the magnesium-thorium alloy is needed before any reliable conclusions can 

be arrived at regarding Rocky Flats workers from this material” (SC&A 2007a).

 

During this review, SC&A interviewed a Dow Madison worker who had claimed that shipments 

of Mg-Th alloy material were being sent to Rocky Flats during a 12-year period from 1963 to 

about 1975 (SC&A 2007b). The interviewee indicated that four truckloads of Mg-Th alloy were 

being shipped to RFP per month, and that the same material was being shipped to Los Alamos 

National Laboratory (LANL). Dow Madison also received scrap returns from the various 

Atomic Energy Commission (AEC) sites, including RFP, which was clearly labeled on the 

returns. The interviewee indicated that four Mg-Th alloys were involved: HK31, HK61, HM21, 

and HM31. 

At the Rocky Flats Work Group request, NIOSH subsequently interviewed four site experts from 

RFP regarding the degree of exchange of Mg-Th between RFP and Dow Madison, if any. As 

noted in NIOSH’s August 13, 2014, paper (NIOSH 2014), the four experts interviewed did not 

recall any large quantities of magnesium alloy in use at RFP, and did not recall any shipments of 

such material between RFP and Dow Madison. As the Work Group took no further action, 

NIOSH considered this issue closed.

The issue was raised again by the petitioner for the current SEC-00192 via e-mail on May 31, 

2013, who indicated that a third party had reported that Mg-Th alloy plates had been brought to 

RFP, refined in Building 881, and then sent to the MOD center for modification to fit “Semi 

Trucks” to make them bullet proof (NIOSH 2014). NIOSH has since conducted further records 

review of the Site Research Database (SRDB) to locate any documentation establishing a link 

between Mg-Th alloy and RFP, conducted new keyword searches of available RFP documents 

(e.g., using HK-31 and HK-31A, as key search parameters), performed additional onsite 

document searches, and interviewed additional former RFP workers, in particular, one who 
Memo to RFP Work Group Re: Mg-Th 2 SC&A – September 11, 2014

NOTICE: This information is protected by Privacy Act 5 U.S.C. § 552a; disclosure to any third party without the 

written consent of the individual to whom the information pertains is strictly prohibited.

worked at the MOD center. None of these more recent investigations have surfaced new 

information which has led NIOSH to change its original conclusions from 2007 that there is no 

evidence of the use of Mg-Th alloy material at RFP. NIOSH opines that there is likely 

“confusion between RFP and other Denver-area sites, as well as confusion regarding Mg-Th 

plates and other similar materials at RFP.”

SC&A REVIEW

Based on its review of past documentation, worker interviews, and NIOSH’s more recent 

investigation, SC&A finds the following:

1. The Dow Madison worker interviewed by SC&A in 2007 provided a level of clarity and 

detail in his recollections of the Mg-Th alloy shipments between Dow Madison and RFP,

which make it difficult to attribute his identification of RFP as the recipient as merely 

“confusion” on his part. For example, the interviewee clearly identified that returned 

scrap was received from all recipient sites, with that of RFP being clearly labeled as such. 

NIOSH’s conjecture of possible confusion between various federal sites located in the 

Denver, Colorado, area, is based on an interview conducted with the same worker where 

the question was posed whether it would be possible that he had mistaken “Rocky Flats 

Plant” for “Rocky Mountain Arsenal,” to which the worker admitted the possibility. On 

this basis, however, it is just as “possible” that the worker had it right all along—he had 

never heard of Rocky Mountain Arsenal before. In such speculative matters, it often 

depends on how the question is posed.

2. This interviewee identified five Mg-Th alloy specifications that applied to shipments to 

RFP and other locations: HK-31, HK-31A, HK-61, HM-21, and HM-31. NIOSH only 

searched against the first two specifications; HK-31 and HK-31A. Without a complete 

document search of both the SRDB and onsite holdings of LANL (see below) and the 

Denver Federal Records Center against all of the applicable Mg-Th alloy specifications in 

historic use, any results may be incomplete.

3. In his October 16, 2013, comments before the full Advisory Board in its meeting in 

Denver (McKeel 2013), Colorado, Dow co-petitioner Dan McKeel noted that he had 

made inquiries to the Department of Energy (DOE) via the Freedom of Information Act 

in May 2013 regarding Mg-Th use and had not yet heard anything. He was also told by 

DOE that about 400 boxes of records pertaining to RFP are located at LANL, but would 

need to be searched by hand. He indicated that some of these records are classified and 

was told any such search would take about 2 years. Without accessing these records, any 

final conclusions regarding facility use and shipments of Mg-Th would be premature.

4. As part of a search of the DOE’s NMMSS1classified inventory, a search was conducted 

by NIOSH on August 26, 2014, for the presence of thorium at RFP during the years in 

question. No evidence apparently was found that thorium in any form was present during 

the time period sampled (a month in 1974). This result, notwithstanding, it should be 

noted that, as explained by the DOE NMMSS project manager during that site visit, each 

 

1 Nuclear Materials Management and Safeguards System
Memo to RFP Work Group Re: Mg-Th 3 SC&A – September 11, 2014

NOTICE: This information is protected by Privacy Act 5 U.S.C. § 552a; disclosure to any third party without the 

written consent of the individual to whom the information pertains is strictly prohibited.

site contributed to this database inventory applying its own judgment of significance and 

it is likely that RFP would not have considered 2%–3% thorium in Mg-Th alloy to be a 

reportable quantity for materials accountability purposes, given the other more sizeable 

and significant radiological inventories of plutonium and uranium. 

While the above findings would indicate the need for additional investigation on the issue of MgTh receipt and use at RFP, the value of that effort would need to be weighed by the Work Group 

against the resources required to investigate the remaining records, if they can even be identified

at this stage. The reported Mg-Th use period for the AEC weapons complex (1956–1969, SRDB 

53615) falls within the current SEC period for RFP (1952–1983) and, therefore, would only 

influence partial dose reconstructions. While the reported concentration of thorium in the alloy 

material (2%–3%) is relatively low, the dose contribution to workers, if they were involved with 

certain, intrusive handling of the material (e.g., grinding, smelting, or fabricating), could 

potentially be significant, as pointed out by SC&A in its 2007 review of NUREG -1717 and 

potential worker exposures from 4% thoriated welding rods. (SC&A 2007a).

CONCLUSIONS

As SC&A observed in its June 1, 2007, Second Supplemental Report to the Advisory Board 

(SC&A 2007c):

Two rather different positions in regard to the thorium-magnesium alloy at Rocky 

Flats now exist. The first is a scenario based on Rocky Flats site expert 

statements regarding lack of evidence of receipt of such shipments, and other 

considerations (e.g., inventory). The second scenario is based on statements by a 

Dow Madison worker that there were large and regular shipments of thorium 

magnesium alloy to Rocky Flats.

While NIOSH’s more recent investigation has now encompassed additional site expert 

interviews that address the RFP MOD facility (the subject of the most recent allegation), 

additional document searches, and onsite data capture at the Denver Federal Records facility, the 

evidentiary conflict observed above has not changed.

In SC&A’s judgment, the receipt and use of Mg-Th alloy material at RFP remains inconclusive,

given the incompleteness of document searches and reviews, particularly of the apparent records 

collection identified at LANL. However, it is within the Work Group’s purview to judge 

whether further investigation is warranted, given the uncertainty of corroborating evidence being 

uncovered, the subsuming scope of the current SEC period, and the resources that will be 

required to probe this issue further. 
Memo to RFP Work Group Re: Mg-Th 4 SC&A – September 11, 2014

NOTICE: This information is protected by Privacy Act 5 U.S.C. § 552a; disclosure to any third party without the 

written consent of the individual to whom the information pertains is strictly prohibited.

REFERENCES

McKeel 2013. Daniel McKeel, public comments before the Advisory Board on Radiation and 

Worker Health, Denver, Colorado, October 16, 2013, transcript, page 340 

(http://www.cdc.gov/niosh/ocas/pdfs/abrwh/2013/tr101613.pdf).

NIOSH 2014. Existence of Mg-Th Alloy at RFP Based on Worker Statements, Rev. 1, National 

Institute for Occupational Safety and Health; Bogard, J.S., and Dan Stemfley, Oak Ridge 

Associated Universities Team (ORAUT), Cincinnati, Ohio. August 13, 2014.

SC&A 2007a. Review of the Rocky Flats Plant Special Exposure Cohort Petition, SEC-00030, 

Volume 1: Main Report, SC&A, Inc., Vienna, Virginia. April 5, 2007.

SC&A 2007b. Review of the Rocky Flats Plant Special Exposure Cohort Petition, SEC-00030, 

Volume 2: Attachments, SC&A, Inc., Vienna, Virginia. April 27, 2007.

SC&A 2007c. Review of the Rocky Flats Plant Special Exposure Cohort Petition, SEC-00030, 

Second Supplemental Report on the Rocky Flats SEC Petition, SC&A, Inc., Vienna, Virginia. 

June 1, 2007.