Rocky Flats Plant 

Special Exposure Cohort (SEC) 

Petition 00192 Follow-up Status

LaVon B. Rutherford, CHP

National Institute for Occupational Safety and Health

Division of Compensation Analysis and Support

September 2013

Cincinnati, OH 
Background

 SEC-00192 Evaluation Report (ER) was issued on 

September 5, 2012

 The ER was presented by NIOSH on September 18, 

2012, at the Advisory Board meeting in Denver, CO

• The recommendation was for no class to be added

 The Board made a determination at the meeting 

that additional review was required, including 

classified interviews and classified document 

review
Follow-up Efforts

 Additional Data Captures (classified and 

unclassified) – Los Alamos National Laboratory, 

Office of Scientific and Technical Information, 

Environmental Management Consolidated Business 

Center, and DOE-Legacy Management

 Secure Discussions

 Secure Interviews and other interviews (19)

 Additional dose reconstruction modeling
Post Evaluation Issues/White Papers

 Follow-up Efforts on SEC-00192 Rocky Flats Plant 

(RFP) Tritium Issues

 Evaluation of Petitioner Concerns about Data 

Falsification and/or Data Invalidation in RFP 

Building 123 Based on Worker Allegations

 U-233/Thorium Strikes – evaluation included in 

revised ER

 Neptunium – evaluation included in revised ER

 Other Thorium Activities – evaluation included in ER
White Paper - Tritium

 Follow-up Efforts on SEC-00192 RFP Tritium Issues

• Issued the report on 6-25-13

o White paper concluded tritium dose reconstruction feasible 

• Provided to the work group on 6-26-13 and the 

petitioners on 7-3-13 (Authorized Derivative Classifier 

Review-ADC)

• Presented to the work group and petitioners on 7-8-13 

during the RFP work group meeting

o Preliminary follow-up questions identified by the work group and 

Sanford Cohen and Associates (SC&A) 
White Paper – Data Falsification/

Data Invalidation

 White Paper: Evaluation of Petitioner Concerns 

about Data Falsification an/or Data Invalidation in 

RFP Building 123 Based on Worker Allegations

• Issued the report on 6-25-13 

• Provided to the work group on 6-26-13 and the 

petitioners on 7-3-13 (ADC Review)

• Presented to the work group and petitioners on 7-8-13 

during the RFP work group meeting

o Preliminary follow-up questions identified by the work group and 

SC&A
U-233/Thorium Strikes

 U-233/Thorium strikes was originally vetted under the SEC -

0030 evaluation

• Re-opened under SEC-0192 after indications this may have occurred 

more than the two times (1965 and 1967) previously identified

 U-233 was being evaluated for its use in the weapons 

program

 Problems with U-233 was a contaminant U-232

• U-232 progeny pose a significant external hazard

 A chemical process called a “Thorium strike” was used to 

remove the Th-228 and its progeny
U-233/Thorium Strikes—cont.

 During the deliberation of SEC-0030 the bounding 

Thorium dose was based on air sampling taken 

during the strike in 1965

 This strike was considered bounding because it had 

the highest concentration of U-232 of the two 

strikes

 No credit was taken for ventilation, hoods or time 

limits
U-233/Thorium Strikes—cont.

 Interviews and documents indicated additional strikes 

occurred other than the two previously evaluated

• Were the potential exposures from other strikes bounded by the 

1965 exposure analysis? 

 Other questions came up based on recent addition of a class 

at Hanford based on inability to reconstruct doses to U-233, 

Neptunium, Thorium and Highly Enriched Uranium

• Were the activities similar?

• Were the material quantities similar?

• How much monitoring data do we have in comparison?
U-233/Thorium Strikes—cont.

Reasons for believing 1965 Strike is still bounding for 

Thorium

 Most documents indicate the U-233 was to be processed or 

shipped off site prior to the 90 day period to prevent the 

hazard from the ingrowth and therefore a strike would not 

be required

 Documents indicate the concentration of U-232 did not 

exceed 8 ppm after 1965

 Although NIOSH determined the 1965 exposure was still 

bounding, it’s not clear how this would be applied if 

additional strikes are assumed
U-233/Thorium Strikes—cont.

Determining U-233 exposures

 The quantity of U-233 on site at RFP varied from 1964 to the 

end of U-233 operations in 1983

 Estimates from available documents indicate quantities 

could have been from 1 kg up to 150 kg from 1965 through 

1983

• Highest quantities from 1965 through 1968

 Bioassay data for uranium exists and a uranium co-worker 

model exists for the period of concern
U-233/Thorium Strikes—cont.

Determining U-233 exposures

 Initial idea was to give a corrected uranium dose to all 

workers with uranium bioassay

• Assumption based on all workers who worked on U-233 activities 

would have uranium bioassay

 A review was conducted to determine if any of the 

Operators (46) listed in logbook for U-233 operations were 

existing claimants in NOCTS

• There were 18 of the 46 who are claimants

• Of the 18 claimants, 17 had uranium bioassay. There was no clear 

reason why this claimant did not have bioassay.
U-233/Thorium Strikes—cont.

Determining U-233 exposures

 Indication not all workers working on U-233 operations had 

uranium bioassay

 Therefore, NIOSH would have to assume all workers could 

have been exposed and a correction factor for exposures to 

U-233/U-232 and progeny applied

• Factor could vary significantly depending on mass based analysis or 

activity based 

 DCAS management did not feel this was sufficiently accurate 

and the quantities, activities, and available monitoring were 

similar to a similar period at Hanford where DCAS 

determined dose reconstruction was not feasible
Neptunium

 General conclusion under SEC-0030 was Neptunium 

was used in small quantities for research type work 

and had limited exposure potential compared to 

Uranium and Thorium

 A determination was made to re-explore this 

exposure situation based on interviews and recent 

determination associated with Neptunium, U-233, 

and Thorium at Hanford
Neptunium

 Records indicate that Neptunium was processed at 

Rocky Flats as early as 1962 and inventories existed 

until 1988

 Neptunium was processed to produce pure 

Neptunium oxide, metal, and metal alloys

 Processes employed included dissolution, anion 

exchange, precipitation, filtration, calcination, 

conversion to fluoride, and reduction to metal
Neptunium—cont.

 Fabrication steps such as casting and rolling were 

performed to produce metal shapes and foils

 Neptunium was also recovered from residual 

materials including sand, slag, crucibles, casting 

skulls, and alloys

• The residues were not only from Rocky Flats operations, 

but residues were sent from other sites

 Based on documents and inventories it appears 

most work with Neptunium was completed by the 

end of 1983
Neptunium—cont.

 Annual on site inventories were typically 

maintained around 1 kg

• Does not address throughput

 Batches involving Neptunium typically did not 

exceed 300 grams

 Buildings having Neptunium inventories included 

371, 559, 707, 771, 776, 777, 779, 779A, and 991
Neptunium—cont.

Neptunium Exposure

 Documents indicate some early work was 

conducted in open hoods, but most work was 

performed in glove boxes

 Based on NIOSH’s review, Neptunium exposure 

potential existed at every processing step, including 

extraction and purification, hydrofluorination, 

reduction to metal, alloying, casting, and rolling
Neptunium—cont.

Personal Monitoring Data

 There are only two bioassay samples for Neptunium 

 They were both taken in 1966

• One “Below Significant Level” and the other 0.9 dpm/24hr

 Gross Alpha bioassay samples existed up until 1970s

Workplace Monitoring Data

 NIOSH has found no workplace monitoring records (e.g., air 

sample, surface contamination samples) specific to 

Neptunium
Neptunium—cont.

Feasibility Determination

 Can we use gross alpha samples as indicator for Neptunium?

• NIOSH interviewed two former Rocky Flats Plant employees involved 

with the Radiological Controls program and the Bioassay lab

• Interviews indicated that it would be questionable based on the 

chemistry whether you would see the Neptunium in the sample

• Interviews indicated that the intent of co-precipitation process used 

after 1961 for “Gross Alpha” analysis was to focus the analysis on 

specific radionuclides typically Uranium and possibly plutonium
Neptunium—cont.

Feasibility Determination-cont.

 Little to no personal or area monitoring data

 Gross Alpha bioassay samples not a viable means for 

estimating Neptunium exposures

 Too many different types of activities including wet and dry 

processes to develop an exposure model

 Additionally, the source term varied in amount and chemical 

form
Neptunium—cont.

Feasibility Determination-cont.

 Quantities and activities associated with Neptunium at 

Rocky Flats are similar to Hanford during the same time 

period

 Based on this, NIOSH has concluded dose reconstruction is 

not feasible for Neptunium exposures
Other Thorium Issues

 In SEC-0030 evaluation the NIOSH position was that documents 

supported that Thorium quantities present at Rocky Flats were 

not in high enough quantities to contribute significantly to 

internal dose potential.

 As stated in NIOSH’s original SEC-0030 evaluation, beginning in 

1952, Thorium was used on site in quantities small enough that 

effluents were not routinely analyzed for Th. Thorium quantities 

varied from as little as none to as much as 238 kilograms (kg) in a 

given month. The principle use was fabrication of metal parts 

from natural Thorium metal (Th-232) and from various Thorium 

alloys. Thorium oxide might have been used as a mold-coating 

compound in limited experiments. Thorium compounds were 

used in analytical procedures. 
Other Thorium Issues

 Most of the work associated with Thorium during 

the SEC-0030 evaluation was focused on specific 

activities that occurred in the 1960s

 Based on interviews and document review, NIOSH 

decided to re-evaluate the Thorium issue, especially 

for the earlier years
Other Thorium Issues

 NIOSH could not find any reports or documents that 

supported other activity occurring 

 Changing Inventories in these early years supported 

that work with Thorium was occurring during this 

period

 Based on NIOSH’s review of the NMMS database, 

no significant quantities of Thorium existed at 

Rocky Flats after 1971 
Other Thorium Issues

Thorium Feasibility Determination

 NIOSH is still evaluating the early years of Thorium 

operations at Rocky Flats Plant
SEC-0192 Revised Evaluation Report

 Current SEC classes from SEC-0030

– April 1, 1952 through December 31, 1958: Employees of DOE, its 

predecessor agencies, or DOE contractors or subcontractors who were 

monitored or should have been monitored for neutron exposures 

while working at the Rocky Flats Plant in Golden, Colorado, for a 

number of work days aggregating at least 250 work days from April 1, 

1952, through December 31, 1958, .....

– January 1, 1959 through December 31, 1966: Employees of DOE, its 

predecessor agencies, or DOE contractors or subcontractors who were 

monitored or should have been monitored for neutron exposures 

while working at the Rocky Flats Plant in Golden, Colorado, for a 

number of work days aggregating at least 250 work days from January 

1, 1959, through December 31, 1966, ....
SEC-0192 Revised Evaluation Report

 Based on the inability to reconstruct U-233 and 

Neptunium, NIOSH will be recommending a class at the 

October Advisory Board meeting 

 The parameters of that class recommendation have not 

been fully determined, but they will include the years 

previously discussed for U-233 and Neptunium 

operations