Page 1 of 42

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Follow-up Efforts on SEC-00192 

Rocky Flats Plant Tritium Issues 

White Paper 

Rev. 2 

National Institute for Occupational 

Safety and Health 

July 1, 2015 

J. S. Bogard, E. M. Brackett, Mutty Sharfi, Tom LaBone, Nancy Chalmers, and Dan Stempfley, 

Oak Ridge Associated Universities Team

- 

Reviewed by Dr. James W. Neton and LaVon B. Rutherford, CHP 

Division of Compensation Analysis and Support 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

Page 2 of 44 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review 

contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution. 

INTRODUCTION

This is a summary of the initial and secondary tritium follow-up efforts performed by the 

National Institute for Occupational Safety and Health (NIOSH) Division of Compensation 

Analysis and Support (DCAS) and Oak Ridge Associated Universities Team (ORAUT) in 

support of the SEC-00192 Rocky Flats Plant (RFP) Special Exposure Cohort (SEC) Evaluation 

Report (ER) presented to the Advisory Board on Radiation and Worker Health (Advisory Board) 

in September 2012. 

As part of the initial follow-up, additional document data captures and personnel interviews were 

performed (classified and unclassified) to: (1) clarify the existence of tritium on site and 

associated personnel exposures; (2) expand the investigation on tritium bubbler sampling; (3) 

confirm the existence of shipping container tritium surveys; and (4) confirm the type and amount 

of sampling analysis performed in Building 123. These initial follow-up efforts were performed 

to validate the tritium bounding method for the SEC-00192 RFP ER (which uses information 

from the 1973 tritium incident as the maximum exposure scenario), and to provide more precise 

estimates of doses due to tritium. 

NIOSH requested that ORAUT conduct a secondary follow-up effort and evaluate all available 

documentation/data in light of the additional information captured during the initial effort (this 

additional information was included in Rev. 1 to the initial tritium follow-up paper). NIOSH 

requested that ORAUT: 

 analyze RFP occupational tritium exposures prior to 1973 (see Appendix 1).

 determine the best approach for tritium dose assignments for 1973 and later (see Appendix 1).

 provide an example tritium dose reconstruction using this approach (see Appendix 1).

 prepare responses to comments from the Advisory Board Work Group and Sanford Cohen & 

Associates (SC&A) on the RFP Tritium White Paper (see Appendix 2).

In this most recent revision (additional information included in this Rev. 2 to the initial tritium 

follow-up paper), ORAUT was also asked to: 

 revise the best approach for tritium dose assignments for 1973 and provide additional 

explanation on the reconstruction of organically-bound tritium (OBT) using urine bioassay in 

IMBA (see Appendix 1).

 comprehensively close out the issue of RFP tritium exposure after 1973 by evaluating the 

evidence of a robust workplace monitoring program (see Appendix 3). 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

Page 3 of 44 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review 

contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution. 

INITIAL FOLLOW-UP

A review of all RFP-related Site Research Database (SRDB) documents was performed to 

determine if any documents existed in that dataset that could expand on any of the issues raised 

regarding tritium. The documents relating to tritium monitoring at RFP were identified, 

including some tritium bubbler results, and some indication of tritium contamination surveys. 

There are multiple documents regarding four significant incident-related tritium releases that 

occurred in 1968, 1973, 1974, and 1977 (SRDB Ref ID: 8265, 8790, 24164, 24165, 24167, 

110900, 110901, and 110903). There are also post-1977 documents that confirm continued 

monitoring of tritium releases and residual tritium as a result of these four earlier releases. 

There is also an SRDB document that provides information on post-1977 stack releases 

occurring in 1981 and 1986; both releases were considered small with no impact to site 

personnel or the immediate surrounding area (SRDB Ref ID: 110900). While some of the 

documents corroborated the classified interview issues addressed in the following sections of this 

white paper (i.e., bubblers and tritium contamination surveys), it does not appear that any of the 

new information supports the notion that there were any tritium levels that exceeded the 1973 

incident. Therefore, ORAUT finds no evidence disputing the use of the 1973 incident data as the 

bounding estimate for tritium at RFP, as presented in the SEC-00192 RFP ER. 

As stated in the SEC-00192 ER, RFP operations that were related to, or had potential exposure 

impacts associated with tritium included neutron generator operations (i.e., the use of tritiated 

targets), and returned pit operations. Subsequent post-ER classified interviews identified 

shipping container handling as a potential exposure source. 

The following was learned: 

 The follow-up effort corroborated in at least one interview (SRDB 122907) and in two 

documents (SRDB 118369; 117274) the point made in the SEC-00192 ER that the stainless 

steel reservoir operation was a construction operation before the introduction of tritium, 

which occurred at other sites. RFP was responsible for constructing the reservoirs and 

shipping them to other locations where they were filled/used. 

 The follow-up effort corroborated that the neutron generator tritium target sources did not 

represent a source larger than the one represented in the 1973 tritium incident. 

 The tritium-contaminated pits and shipping containers are considered directly related because 

the shipping container tritium was a result of tritium from the pits loaded in the containers. 

Because of potential classification issues, the assessment of this issue will be addressed later 

in this document under the more general term Shipping Containers rather than the term Pits. 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

Page 4 of 44 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review 

contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution. 

 A follow-up effort was directed to determine if there are any other scenarios with the 

potential to exceed the SEC-00192 RFP ER bounding approach. These scenarios are being 

assessed as part of the pre-1973 tritium shipping container exposure evaluation (discussed 

later). 

The indications found in the available documentation and provided by the majority of 

interviewees, was that RFP did not work with tritium as a normal or usual process, and therefore, 

did not expect it on site. The RFP radiological program did very little monitoring for tritium 

prior to the 1973 incident because they felt they had limited tritium exposure potential. Changes 

to the program related to tritium monitoring were implemented as a result of the 1973 incident. 

It has been corroborated that tritium bubbler monitoring did exist on site as part of the usual RFP 

air monitoring program before and after the 1973 tritium incident (SRDB 122907); however, the 

current information does not indicate how long before the 1973 incident bubblers existed on site. 

The available bubbler monitoring data are being evaluated for applicability in dose 

reconstructions. 

As indicated in the SEC-00192 ER, the site implemented a routine tritium bioassay program after 

the 1973 tritium incident, but discontinued the routine program in 1975 due to lack of positive 

bioassay results. The program was subsequently implemented on an as-needed or as-identified 

basis. This situation was corroborated in at least one personnel interview performed during this 

follow-up effort (SRDB 122907). 

INITIAL FOLLOW-UP: TRITIUM BUBBLERS 

Significant information on the bubbler monitors was discovered during the additional follow-up 

data capture efforts. There is some documentation in the SRDB that discusses the use of tritium 

bubblers. Based on the available data, including the most recent information (schematics and 

pictures of the tritium air sampling and monitoring equipment and processes [SRDB 122779 

through 122791]), there was a program that included the use of tritium bubblers to monitor 

enclosed and exhaust systems for tritium (SRDB 122466). As previously discussed, the exact 

start date for the use of bubblers has not been confirmed, but they did exist on site before the 

1973 incident (SRDB 122907). Most individuals interviewed were not well-informed on bubbler 

use or operation. 

The SRDB contains some tritium bubbler results (SRDB 111095 and 122712) as well as detailed 

schematics and pictures of the units (SRDB Ref ID’s: 122691, 122692, 122693, 122787, 122788, 

122789, and 122790). Based on these results, information discovered during the follow-up 

research, and the interviews there is nothing to support the occurrence of a release event more 

significant than the 1973 incident. 

Table 1 below presents a summary of the Rocky Flats tritium bubbler information contained in 

the SRDB. 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

Page 5 of 44 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review 

contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution. 

Table 1: Rocky Flats Tritium Bubbler Information in the SRDB

(This table spans three pages)

SRDB 

Ref ID

Year File Description Comments

Category: Tritium Monitoring Results, Procedures, and Occurrences

17824 1990-

1991 Occurrence reports

Contains two occurrence reports involving inoperable bubblers, 

and one report of a Triton tritium air monitor that was shut off. 

None of the occurrences involved tritium releases.

24164 1976-

1983

Tritium inventories and

effluents

Contains: an evaluation of tritium-release potential from a 

proposed neutron crate counter (1983); elevated tritium 

effluents from Bldg. 776/777 (January 1981); estimated 

inventory of tritium as surface contamination in glove boxes, 

ducts, and exhaust plenums in Bldg. 776/777 (1980); evaluation 

of ethylene glycol in place of water in tritium bubblers (1978); 

special study of tritium in ambient air (1976); a report, 

“Estimates of Maximum Tritium Releases to the Atmosphere 

from Operations at the Rocky Flats Plant” (1976); and a Call 

Report indicating that 0.058 μCi of tritium would probably be 

vented to the atmosphere for an experiment on May 20, 1974.

24307 1986

Procedure for effluent 

and room air tritium 

sampling

Operating procedure

111095 1977-

1981

Tritium bubbler 

sampling results

Log of analytical results for bubblers in operating areas, 

including room air and near downdraft tables. Most results are 

<100 pCi/m3, but results exceed 1,000 pCi/m3 on several 

occasions in Bldg. 559 - Rm 102, and in Bldg. 881- Rm 283. 

Highest result appears to be 89,230 pCi/m3in Bldg. 771 for the 

period May 11-18, 1978 (PDF pp. 92, 93), although the 

measurement appears to be associated with a filter plenum or 

filter unit and not workplace air.*

122466 2013 Documented interview 

with [Name redacted]

Includes a discussion of the different laboratories at Rocky Flats 

for analyzing tritium and other radionuclides in samples.

122712 1998 Lab report - tritium 

activity in bubblers

Detailed analytical report from Thermo NUtech, including 

sample activity, counting uncertainty, detection limit, and total 

propagated uncertainty.

122907;

24167 2013

Documented interview 

with [Name redacted]; 

1973 incident report

Includes a discussion of the tritiated targets for laser fusion 

experiments and corroboration that bubblers were in use at 

several Rocky Flats locations prior to the 1973 tritium release 

incident.

Category: Tritium Sampler Photos and Design Documents

122691 1973 Photos – tritium 

operations at Dow

Relevance of photos to tritium monitoring or tritium operations 

is not apparent, except for one photo of a Triton tritium monitor.
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

Page 6 of 44 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review 

contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution. 

Table 1: Rocky Flats Tritium Bubbler Information in the SRDB

(This table spans three pages)

SRDB 

Ref ID

Year File Description Comments

122692 1977 Photos - tritium 

monitoring

Good photos of sampling fixture for sealed cans and drums, 

Triton Model 955B tritium monitor, and bubblers mounted 

outside a glove box for sampling glove box air.

122693 1983 Photos – tritium air 

sampling station

Labeled tritium sampling assembly showing building number, 

air flow rates, and water volume.

122779 1974

Drawing 1 of 8 - Tritium 

and iodine sampler 

assembly

Engineering drawing

122780 1974

Drawing 2 of 8 - Tritium 

and iodine sampler 

assembly

Engineering drawing

122781 1974

Drawing -

Environmental tritium 

and radioiodine sampler 

details

Engineering drawing

122782 1974

Drawing -

Environmental tritium 

and radioiodine sampler 

wiring diagram

Engineering drawing

122783 1974

Drawing -

Environmental tritium 

and radioiodine sampler 

mounting detail

Engineering drawing

122784 1974

Drawing -

Environmental tritium 

and radioiodine sampler 

onsite electrical hookup

Engineering drawing

122785 1974

Drawing -

Environmental tritium 

and radioiodine sampler 

offsite electrical hookup

Engineering drawing

122786 1974

Drawing -

Environmental tritium 

and radioiodine sampler 

onsite and offsite 

electrical hookup

Engineering drawing

122787 1978 Drawing – Tritium 

detector assembly Engineering drawing
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

Page 7 of 44 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review 

contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution. 

Table 1: Rocky Flats Tritium Bubbler Information in the SRDB

(This table spans three pages)

SRDB 

Ref ID

Year File Description Comments

122788 1978 Drawing – Tritium 

detector details (1) Engineering drawing

122789 1978 Drawing – Tritium 

detector details (2) Engineering drawing

122790 1978 Drawing – Tritium 

detector details (3) Engineering drawing

122791 1978 Drawing - Tritium 

detector flow diagram Engineering drawing

* The bubbler location associated with the elevated result of May 11-18, 1978 was entered in the sample analysis 

log as “771 Fu 2”. Two incident reports found in the SRDB refer to the FU2B filter plenum or filter unit in Building 

771 (SRDB 17817, PDF pp. 285-287, 344-347; SRDB 17819, PDF pp. 363-365). 

INITIAL FOLLOW-UP: SHIPPING CONTAINER TRITIUM SURVEYS 

As part of the follow-up, additional research was performed regarding the issue of tritium 

contamination in shipping containers. This issue arose from one of the classified interviews 

(SRDB 122516). Tritium contamination in shipping containers was corroborated in an SRDB 

document (SRDB Ref ID: 111301); however, no actual contamination surveys have been found. 

The follow-up survey requirements and processes were corroborated in a follow-up interview in 

which the interviewee discussed implementing the shipping container tritium survey program in 

response to the 1973 incident (SRDB 122907). During that interview, the interviewee said that 

no tritium contamination was ever found. Other classified interviewees indicated that they had 

heard about shipping-container contamination, but they had no direct experience of it. A worstcase situation analysis of potential shipping-container contamination levels has been performed 

for comparison with the SEC-00192 ER bounding analysis in order to validate the ER’s 

bounding exposure scenario and to provide a more precise estimate for tritium dose prior to 

1973. This analysis is provided in Appendix 1. 

INITIAL FOLLOW-UP: SAMPLE ANALYSIS IN BUILDING 123 

Analytical capability existed in both the production areas and in Building 123 (SRDB 122625), 

which housed the laboratories supporting worker health and safety (Industrial Hygiene and 

Health Physics) as well as the environmental programs (SRDB 122627). Samples collected in 

the production areas may have been analyzed either in the production laboratories or in Building 

123, depending on the anticipated level of analytes and the potential for contamination with 

plutonium or uranium, for which strong contamination-control practices were in place. Tritium 

samples from stack exhausts, which were filtered several times before sampling and release to 

the environment, were typically analyzed in Building 123. Samples collected in the work areas 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

Page 8 of 44 

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Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review 

contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution. 

were analyzed in a production area laboratory to eliminate the possibility of introducing 

plutonium contamination into the Building 123 lab (SRDB 122627). Samples with a high 

likelihood of elevated tritium content might also be analyzed in a production lab to prevent 

tritium contamination in the low-level Building 123 laboratories (SRDB 122624). 

Some effort was made prior to 1973 to use commercially-available tritium monitoring equipment 

(e.g., the vibrating reed spectrometer and tritium sniffers) (SRDB 110885; 122623; 122670; 

122671) or to develop an in-house capability (through development of specialized ion chambers 

or tritium concentration techniques, such as silica gel traps [SRDB 24648; 24680]). Liquid 

scintillation counting was reportedly used for quantitative analysis of a variety of radioactive 

materials in the production areas; it quickly became the technique of choice for tritium sample 

analysis after the 1973 environmental tritium release. Tritium sniffers continued to be used to 

indicate elevated tritium in the workplace, but they did not provide quantitative data of record. 

No results for tritium samples analyzed in the production areas have been captured, and only 

limited data are available from the Building 123 laboratories. ORAUT’s understanding of the 

criteria for determining where tritium samples were analyzed comes solely from interviews with 

former Rocky Flats Plant employees. 

INITIAL FOLLOW-UP: CONCLUSION

The additional documents and interviews obtained during the post-ER follow-up efforts provide 

additional evidence of the potential for tritium exposures. However, the information also 

supports the case that estimates of potential tritium exposure that could have occurred prior to 

1973 are bounded by the exposure estimate for the 1973 event, and that more precise estimates 

are feasible. 

Table 2 below lists the follow-up actions performed in support of SEC-00192. 

Table 3 further below lists the follow-up interviews performed in support of SEC-00192. 

SECONDARY FOLLOW-UP: APPENDICES 1, 2 AND 3 

In light of the additional information and data gathered during the follow-up effort, NIOSH 

requested that ORAUT evaluate the available documentation and data to: (1) analyze RFP 

tritium exposures for 1959-1973; (2) determine the best approach for dose assignment for 1973 

and later; and then (3) produce an example tritium dose reconstruction employing the best 

approach determined in the analysis. The results of this assessment are provided in Appendix 1. 

NIOSH also asked ORAUT to prepare responses to comments from the Board Working Group 

and SC&A on the RFP Tritium White Paper. These responses are provided in Appendix 2. 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

Page 9 of 44 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review 

contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution. 

NIOSH further asked ORAUT to comprehensively close out the issue of RFP tritium exposure 

after 1973 by evaluating the evidence of a robust workplace monitoring program. Such a 

program would support using the co-worker model discussed in Appendix 1, Part II. The 

evaluation of evidence for a workplace monitoring program is provided in Appendix 3. 

Table 2: Initial and Secondary Follow-up Actions Performed in Support of SEC-00192

Date Activity Locationa

Initial Follow-Up Actions

10/03/2012 Secure Discussions NIOSH (Cincinnati OH)

10/28/2012 Data Capture LANL (Los Alamos NM)

11/06/2012 

through 

11/07/2012

Eleven secure interviews with former RFP employees

(see Table 3) DOE-EMCBC (Denver CO)

01/15/2013 

through 

01/31/2013

Eight follow-up telephone interviews with former RFP 

employees (see Table 3) Employee homes via telephone

02/03/2013 Data Capture DOE-LM (Westminster CO)

EMCBC (Denver CO)

02/22/2013 Data Capture OSTI (Oak Ridge)

02/25/2013 Secure Discussions NIOSH (Cincinnati OH)

Secondary Follow-Up Actions

05/30/2013 Reconstructing Rocky Flats Tritium Doses Pre- and Post1973 (see Appendix 1) ORAUT (Cincinnati OH)

03/06/2014 Response to WG/SC&A Comments on the RFP Tritium 

White Paper (see Appendix 2)

NIOSH (Cincinnati OH); prepared 

by ORAUT (Cincinnati OH)

05/13/2015 Workplace Air Tritium Monitoring at Rocky Flats, 1977-

1981 (see Appendix 3) ORAUT (Cincinnati OH)

aDOE-EMCBC (Denver), LANL (Los Alamos), and OSTI (Oak Ridge) are sites where reviews of classified material were 

performed. Secure interviews were conducted at DOE-EMCBC. 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

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This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review 

contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution. 

Table 3: Follow-up Interviews Performed in Support of SEC-00192

Site Interview Topic Interview Date SRDB Ref ID

Rocky Flats, SEC-00192 Tritium (DFC)* 11/6/2012 122515

Rocky Flats, SEC-00192 Tritium (DFC) 11/6/2012 122553

Rocky Flats, SEC-00192 Tritium (DFC) 11/6/2012 122666

Rocky Flats, SEC-00192 Tritium (DFC) 11/6/2012 122667

Rocky Flats, SEC-00192 Tritium (DFC) 11/6/2012 122668

Rocky Flats, SEC-00192 Tritium (DFC) 11/6/2012 122551

Rocky Flats, SEC-00192 Tritium (DFC) 11/6/2012 122550

Rocky Flats, SEC-00192 Tritium (DFC) 11/7/2012 122517

Rocky Flats, SEC-00192 Tritium (DFC) 11/7/2012 122516

Rocky Flats, SEC-00192 Tritium (DFC) 11/7/2012 122669

Rocky Flats, SEC-00192 Tritium Building 123 1/15/2013 122627

Rocky Flats, SEC-00192 Tritium Building 123 1/15/2013 122628

Rocky Flats, SEC-00192 Tritium Building 123 1/16/2013 122624

Rocky Flats, SEC-00192 Tritium Building 123 1/18/2013 122625

Rocky Flats, SEC-00192 Tritium Building 123 1/22/2013 122629

Rocky Flats, SEC-00192 Tritium Building 123 1/22/2013 122623

Rocky Flats, SEC-00192 Tritium Building 123 1/23/2013 122626

Rocky Flats, SEC-00192 Tritium Building 123 1/31/2013 122670

Rocky Flats, SEC-00192 Tritium Building 123 1/31/2013 122671

* DFC = Denver Federal Center where secure interviews regarding tritium were conducted. 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

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Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review 

contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution. 

Appendix 1: Reconstructing Rocky Flats 

Tritium Doses Pre- and Post-1973

J. S. Bogard, E. M. Brackett, and Mutty Sharfi, ORAUT

Introduction 

The potential for tritium exposure to Rocky Flats personnel was not considered significant until 

an unexpected release occurred in April 1973. Because tritium monitoring was not rigorous 

before this event, NIOSH requested that ORAUT perform a follow-up effort to validate the 

tritium bounding method for the SEC-00192 RFP ER, which uses information from the 1973 

tritium incident as the maximum exposure scenario. ORAUT conducted additional document 

data captures and personnel interviews regarding the existence of tritium on site and associated 

personnel exposures as well as follow-up on tritium bubbler sampling, shipping container tritium 

surveys, and sampling analysis performed in Building 123. 

In light of the additional information and data gathered during the follow-up effort, NIOSH 

requested that ORAUT evaluate the available documentation and data to: (1) analyze RFP 

tritium exposures for 1959-1973; (2) determine the best approach for dose assignment for 1973 

and later; and then (3) produce an example tritium dose reconstruction employing the best 

approach determined in this analysis. This white paper presents the results of these three efforts: 

 PART I: Analysis of Rocky Flats Tritium Exposures for 1959-1973 by J. S. Bogard 

 PART II: Rocky Flats Tritium Dose Assignment for 1973 and Later by E. M. Brackett 

- Attachment A: Rocky Flats 1973 H-3 Dose Assignment by Tom LaBone, 

Nancy Chalmers, and E. M. Brackett 

 PART III: Example RFP Tritium Dose Reconstruction by Mutty Sharfi 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

Page 12 of 44 

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contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for 

distribution. 

PART I: Analysis of Rocky Flats Plant 

Tritium Exposures for 1959-1973

J. S. Bogard, ORAUT 

Tritium Monitoring Data Prior to 1973 

Although tritium was used as a boost gas in weapons and as target material in neutron 

generators, it was not processed or handled in any significant quantities at Rocky Flats. Tritium 

was monitored in the environment around the site for a time, but that monitoring ceased and was 

left to the State of Colorado for a brief period preceding an environmental release that occurred 

in April 1973. No analytical records have been captured by NIOSH that might help establish the 

Rocky Flats workplace tritium environment prior to that time. 

The management of Rocky Flats woke abruptly to the potential for tritium workplace and 

environmental contamination with the release in April 1973 of 500 Ci - 2,000 Ci of tritium, 

primarily from Building 779A, and its eventual detection in waters draining into a reservoir 

serving as a municipal drinking water supply (SRDB Ref ID: 110941; 111269; 111284). The 

release also resulted in tritium exposure to a small number of Rocky Flats personnel. Subsequent 

workplace monitoring and personnel bioassay was implemented, in part to establish the baseline 

tritium environment against which future incidents could be evaluated. A smaller and lessimpactful tritium release occurred in September 1974 from Building 777; the subsequent 

investigation report (SRDB Ref ID: 8790) includes release details along with summaries of 

tritium workplace monitoring results prior to the incident for comparison. These data provide 

the basis for a model for bounding chronic tritium exposures to workers and of smaller, lessnotable tritium releases that might have occurred prior to 1973. 

Several factors single out the 1973 tritium release as bounding for the entire history of Rocky 

Flats operations. These factors include the large quantity of tritium involved, the chemical form 

of the released tritium, and the meteorological conditions at the time of the release. Other 

documented releases involved smaller quantities of elemental tritium, having a much smaller 

dose conversion factor than the tritium oxide released in 1973. Bounds for personnel tritium 

exposures after the 1973 release can be developed based on measurement results, since personnel 

bioassay, air sampling, and workplace contamination monitoring for tritium became more 

common after that release. There are only very limited tritium measurement results prior to 1973 

because tritium was not perceived as a radionuclide of occupational or environmental interest at 

Rocky Flats. Bounding tritium exposures for the pre-1973 period are more difficult to develop 

as a result of this lack of measurement data. 

According to the ChemRisk report (SRDB 8017), there was no environmental monitoring for 

tritium prior to 1970, and little in the way of workplace monitoring until after the 1973 tritium 

release; therefore, evidence of tritium releases prior to 1973 is primarily anecdotal. A 600-Ci 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

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release of elemental tritium (from a different source than the 1973 release) occurred in 1968. 

The ChemRisk report said the following with regard to possible releases from tritiated Pu 

shipments (SRDB 8017, pdf p. 285): 

The 1973 findings associated with the tritiated plutonium initiated an investigation of other 

possible similar shipments and processing of tritiated plutonium. The investigation 

discovered three other shipments with maximum estimated tritium releases of 57 Ci (April 

1969), 40 Ci (March 1971), and 29 Ci (November 1971). 

The reported investigation and the documented 1968 release of elemental tritium are the only 

sources of information about other possible releases. The 1968 release was elemental tritium 

with no significant environmental or personnel exposure. None of the three identified potential 

releases from tritiated Pu was near the magnitude of the 1973 release. There is no evidence of a 

tritium release comparable to the magnitude and impact of the 1973 release prior to that year. 

Source of Data for the pre-1973 Period 

Despite the lack of measurement data, it is possible to develop pre-1973 tritium exposure bounds 

based on measurement results provided in a Rocky Flats Area Office (RFAO) report issued 

subsequent to a tritium release in one of the Rocky Flats production buildings on August 30, 

1974 (SRDB Ref ID: 8790). The information contained in this report includes measurement data 

(i.e., results from air samples, surface contamination surveys, and bioassay) from the production 

area where the release occurred as well as comparison data from other areas prior to, during, and 

after the release. Several factors support the use of these data as surrogates for bounding the 

tritium environment at Rocky Flats prior to 1973: 

1. Background tritium levels immediately prior to the incident described in the RFAO report, 

although undoubtedly elevated since the more significant 1973 release, were well below 

dosimetrically-significant values and can be considered as fairly representative of typical 

background levels for this analysis. The background tritium levels monitored in the months 

prior to the 1974 incident are consistent with internal radiation doses from tritium of well 

under 1 mrem annually. They are dosimetrically insignificant in this sense. 

2. The quantity of tritium released (1.5 Ci) was significantly less than that released in 1973, and 

is probably more typical of potential undocumented releases in work areas – particularly 

those resulting from opening contaminated shipping containers. 

The 1974 1.5-Ci tritium release is the only documented release from a shipping container in 

the Rocky Flats workplace. It is taken to be typical since there are no other such documented 

releases to use in forming the model. There is documented concern about tritium releases, as 

shown in the following quote from the ChemRisk report (SDRB 8017, pdf p. 38): 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

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As early as 1962, Rocky Flats maintained instruments for detection of tritium gas in 

particular work areas of the plant because operations have sometimes resulted in the 

storage of tritium containers.

The instruments available to Rocky Flats at that time were only semi-quantitative for 

indicating the presence of tritium; NIOSH has captured no records of these results. 

Because NIOSH has only identified six documented releases from 1968-1974 (an average of 

1 per year), the application of a daily release would be a significant/bounding overestimate of 

the number of RFP tritium releases. 

3. Tritium was released to the workplace environment, and not in a glovebox.

4. The release involved elemental tritium (HT, T2), and not tritium oxide (HTO)1.

5. The tritium was released from a contaminated shipping container which was procured by 

Rocky Flats in 1970 and can be taken as representative of shipping containers in use prior to 

1973. 

As stated in the response to Item 2, the 1974 1.5-Ci tritium release is the only documented

release from a shipping container in the Rocky Flats workplace. It is taken to be typical since 

there are no other such documented releases to use in forming the model. There is 

documented concern about such releases, as shown in the following quote from the 

ChemRisk report (SDRB 8017, pdf p. 38): 

As early as 1962, Rocky Flats maintained instruments for detection of tritium gas in 

particular work areas of the plant because operations have sometimes resulted in the 

storage of tritium containers. 

The instruments available to Rocky Flats at that time were only semi-quantitative for 

indicating the presence of tritium; NIOSH has captured no records of these results. 

Because NIOSH has only identified six documented releases from 1968-1974 (an average of 

1 per year), the application of a daily release would be a significant/bounding overestimate of 

the number of RFP tritium releases. 

6. The incident occurred close enough in time to the 1973 tritium release that work practices 

and controls were likely more similar to those prior to 1973 than to those even a year or two 

later, as procedures and controls evolved with greater sensitivity to the potential for tritium 

contamination.

 

1

 The impact of the 1973 tritium release was largely due both to the quantity (500 Ci – 2,000 Ci) and the chemical form (HTO) of 

the material. The presence of tritium oxide in the 1973 release resulted from peculiarities of the plutonium recovery operation from 

which it was generated. There is no indication that any other tritium release at Rocky Flats involved the oxide. Tritium in its 

elemental form (HT, T2) is far more likely to have been a contaminant at Rocky Flats because of the nature of its possible source 

terms – tritiated accelerator targets (neutron generators), plutonium hydride in recovery operations, and boost gas in returned 

reservoirs or pits. 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

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distribution. 

The RFAO report provides the best source of monitoring data for use in bounding both chronic 

and accidental tritium exposures to Rocky Flats personnel prior to the unique circumstances of 

the 1973 release. The RFAO report states that elevated tritium concentrations were detected in 

air samples from Room 452 (Special Assembly Area) in Building 777 and from the Building 205 

exhaust plenum servicing Building 776/777 over the period of August 29 – September 4, 1974 

(SRDB Ref ID: 8790, pdf p. 9). Subsequent sampling and investigation of the elevated sample 

results concluded that about 1.5 Ci of tritium was released from the exhaust system of Room 

452, Building 777, when a shipping container (referred to as a “pressure cooker”) received in 

July 1974 from Battelle Pacific Northwest Laboratory (BNW) was opened on a downdraft table 

in Room 452 on August 30 (SRDB Ref ID: 8790, pdf pp. 36-39). No elevated environmental 

tritium levels were detected as a result of the incident, but workplace tritium levels seven times 

the applicable Radiological Control Guide were detected in air samples collected on August 30 

in Room 452 adjacent to the downdraft table, with average concentrations for the work week 

about 1.5 times the guidelines. Table A1-1 below shows the reported values. 

Table A1-1: Reported Tritium Air Concentrations (μCi/m3) from the August 30, 1974 Release

Sampling Reference Plenum 205, Bldg. 776/777a Room 452, Bldg. 777

Normal Concentrations <1×10-2 <1×10-2

August 29-30, 1974 0.148 37.7

September 3-4, 1974 2.51 1.1

 Source: SRDB 8790, pdf pp. 93-96

aThe Special Assembly Glovebox Line in Room 452, Building 777, was normally served by Plenum 206, but exhaust air from 

this area was vented through Plenum 205 from February 11 – August 7, 1974, while a new Plenum 206 was constructed. A 

tritium air sampler for Plenum 206 was installed on August 30, 1974, but showed no elevated results. However, both 

Plenums 205 and Plenum 206 showed elevated tritium removable contamination (SRDB 8790, pdf pp. 74-82). 

An air sampler located near the downdraft table in Room 452 indicated a tritium air 

concentration of 4.9×10-3 μCi/m3on August 29 and 37.7 μCi/m3on August 30. The applicable 

Radioactive Concentration Guideline at the time was 5 μCi/m3

. Two “pressure cookers” were 

opened at the downdraft table, coincident with the elevated tritium-in-air measurements, and 

were smear-sampled for removable tritium contamination. One cooker showed smear levels of 

1.16×10-2 μCi; the other showed 3.43×102 μCi and was presumed to be the source of the gaseous 

tritium release. 

Air Sample Results 

Results from air samples collected daily in Room 452, Building 777, are available from June 3 to 

September 11, 1974. The air sampler was located near the downdraft table entry to the Special 

Assembly Line where the tritium contaminated “pressure cooker” was opened and was the only 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

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tritium air sampler in Building 777 at the time. Room air samples were collected in a water 

bubbler during the day shift (approximately 6 or 8 hours sampling time) at an air flow rate of 

2 L/min. Individual results are shown in Table A1-2 below (SRDB: 8790, pdf pp. 87-89). 

Table A1-2: Tritium Activity Concentrations in Room Air: Rm. 452 - Special Assembly-Bldg. 

777

Analysis Date 

(1974)

[

3H] 

(pCi/m3)

Analysis Date 

(1974)

[

3H] 

(pCi/m3)

Analysis Date 

(1974) [

3H] (pCi/m3

)

3-Jun 9,428 8-Jul 3,872 8-Aug 628

5-Jun 12,121 5-Jul 3,030 12-Aug 1,256

4-Jun 20,370 3-Jul 4,655 13-Aug 1,301

7-Jan 5,892 10-Jul 2,602 16-Aug --

6-Jun 16,498 9-Jul 2,512 20-Aug 2,439

14-Jun 5,387 11-Jul 4,553 21-Aug 3,140

13-Jun 4,553 17-Jul 21,022 22-Aug 3,298

12-Jun 12,358 16-Jul 5,040 23-Aug --

11-Jun 13,972 15-Jul 6,742 26-Aug 2,927

11-Jun 10,894 19-Jul 5,041 27-Aug 3,089

21-Jun 4,348 18-Jul 4,209 28-Aug 4,874

20-Jun 4,553 24-Jul 1,010 29-Aug 3,986

19-Jun 4,414 23-Jul 4,866 30-Aug 37,676,609

18-Jun 5,781 22-Jul 4,866 3-Sep 1,098,901

17-Jun 6,829 29-Jul 2,512 4-Sep 8,477

26-Jun 4,519 26-Jul 2,118 5-Sep 5,108

25-Jun -- 25-Jul 3,089 6-Sep --

24-Jun -- 1-Aug 1,842 9-Sep 3,030

2-Jul 3,454 30-Jul 1,727 10-Sep 3,140

1-Jul 4,348 1-Aug 2,269 11-Sep 2,898

27-Jun 5,366 7-Aug 1,179

27-Jun 4,553 5-Aug 2,512

Source: SRDB: 8790, pdf pp. 87-89

The average and standard deviation of daily air sample results prior to August 30, the day of the 

tritium release from the contaminated shipping container, are (5343 ± 4518) pCi/m3

. The result 

on August 30 is 37,676,609 pCi/m3, and the sample taken on September 3 indicated a tritium 

concentration in the room air of 1,098,901 pCi/m3. However, the September 3 result is suspect 

because the sample was collected in the same vessel that was used on August 30 and which had 

not been cleaned. Smear surveys of Room 452 on September 3 failed to show significant tritium 

contamination (SRDB: 8790, pdf pp. 37-38). Tritium levels in Building 777 were known to be 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

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somewhat elevated over normal background because of residual contamination present since the 

1973 tritium release. 

Bioassay Results 

The practice of pulling a sample of air from within shipping containers through a tritium air 

monitor to check for contamination was implemented after the 1973 tritium release. This 

practice was discontinued after urinary tritium results in the range of 0.75 μCi/L – 1.3 μCi/L 

were detected in May 1974 for the health physics technician who performed the monitoring. The 

technician’s urinary tritium dropped to less than 0.1 μCi/L beginning in early July 1974 (SRDB 

8790, pdf pp. 18-19).

All employees who worked in Room 452, Building 777, submitted urine samples after the 

August 30 tritium release, with a high result of 32,320 pCi/L. Table A1-3 below shows 

individual results (SRDB 8790, pdf p. 90). 

Table A1-3: Tritium Urinalysis Results - Exposed Workers and Others, August 30, 1974

Worker ID Area Urinary Tritium 

(pCi/L) Uncertainty (pCi/L)

A 777 32320 ± 6170

B 777 25610 ± 6100

C 779 24000 ---

D 777 22370 ± 5800

E 777 21600 ± 5800

F 707 17000 ---

G 777 15740 ± 6100

H 777 15730 ± 5640

I 779 14000 ---

J 707 13700 ± 5370

K 123 630 ± 580

Non-Occupational (Denver) 470 ---

Source: SRDB 8790, pdf p. 90; Three hyphens (---) = Value not provided. 

The report indicates that both a Denver resident and a [redacted] employee who did not work in 

radioactive material-handling areas were sampled with results < 0.01 μCi/L (<10,000 pCi/L). 

The Denver resident is identified in Table A1-3, and Worker ID K is believed, by implication, to 

be the [redacted] non-radiological worker. 
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Work Area Smear Surveys 

Over 200 smear results for tritium are tabulated in the RFAO report (SRDB 8790, pdf pp. 74-

82). Most appear to be surveys inside glove boxes, but there are also workplace area results that 

can be used as indicators of likely sources of internal contamination of workers following an 

event such as the one in August 1974. The workplace smear results are shown in Table A1-4

below. 

Table A1-4: Tritium Smear Surveys - Work Areas in Buildings 776-777

(This table spans two pages)

Date Bldg/Room Location Maximum Smear (pCi)

9/6/74 776-205 205 Plenum - cold side < 100

9/6/74 776-206 206 Plenum - cold side < 100

9/6/74 777-452 206-532 - top of box < 100

9/6/74 777-430 E.S. Welder 353,000

9/6/74 777-437 Penthouse < 100

9/6/74 777-437 A-1 110,000

9/6/74 777-437 A-2 4,800

9/6/74 777-437 A-3 9,400

9/6/74 777-463 A-5 1,200

9/6/74 777-463 Conveyor Line 7,900

9/6/74 777-463 A-7 7,700

9/9/74 776-205 205 Plenum (hot side) 211,000

9/9/74 776-206 206 Plenum (hot side) 1,230,000

9/10/74 776 - Size Reduction Floor < 500

9/10/74 776-201 Floor 1,100

9/11/74 777-452 Floor at J-24 460

9/11/74 777-452 Floor at K-24 470

9/11/74 777-452 Floor at L-24 640

9/11/74 777-452 Floor at M-24 780

9/11/74 777-452 Floor at K-25 560

9/11/74 777-452 Floor at J-25 950

9/11/74 776-250 Plenum Floor < 100

9/11/74 776-250 Plenum Fan < 100

9/11/74 776-252 Plenum Floor 465

9/11/74 776-252 Plenum Filter 1,636

9/11/74 776-S-8 Plenum Filter < 100

9/11/74 776-S-8 Plenum Deep Beds < 100

9/11/74 776-S-7 Plenum Filter < 100
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Table A1-4: Tritium Smear Surveys - Work Areas in Buildings 776-777

(This table spans two pages)

Date Bldg/Room Location Maximum Smear (pCi)

9/11/74 776-S-7 Plenum Floor < 100

9/11/74 776-S-4 Plenum Filter < 100

9/11/74 776-251 Plenum Floor 3,625

9/11/74 776-251 Plenum Filter 3,603

9/11/74 776-440 Floor 1,000

9/11/74 776-432 Floor K-20 500

9/11/74 776-432 Floor H-19 1,460

9/11/74 776-432 Floor H-20 710

9/11/74 776-432 Floor K-19 520

9/11/74 776-201 #1 System Kathene 160,000

9/11/74 776-201 #4 System Kathene 400,000

9/11/74 776-201 #3/7 System Kathene 450,000

9/11/74 776-201 #8 System Kathene 140,000

9/11/74 776-201 GBDA System Kathene 400,000

Source: SRDB 8790, pdf pp. 74-82

The exhaust plenums and the Kathabar air driers (which use a lithium chloride solution called 

Kathene) appear to have collected the greatest amount of tritium after the release. Workers 

responsible for changing filters in the plenums or recharging the Kathabar systems would appear 

to be at greatest risk for tritium uptake after the initial release. 

Assessment of the 1974 Incident 

The 1.5-Ci tritium release from a contaminated shipping container occurred on August 30, 1974. 

The RFAO report provides air survey, bioassay, and smear survey results (SRDB 8790). 

Specific urine sample collection dates were not included in the report but data were matched to 

two NOCTS claims, which reported a collection date of September 5, 1974. A dose assessment 

was performed using the Integrated Modules for Bioassay Analysis (IMBA) software. An intake 

date of August 30, 1974 was assumed, and the largest reported result collected after the incident, 

36,320 pCi/L, was used. There was a slight discrepancy (one digit) between the result included 

in the RFAO report and that in the NOCTS case file; the NOCTS value is assumed to be correct 

because it is the handwritten urinalysis record and is also the larger of the two values. The 

resulting dose is < 1 mrem (0.15 mrem). The Excel file RFP H-3 dose calculations – data.xlsx 

contains the information above as well as the data used for the analysis. 
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Conclusion 

The RFAO report (SRDB 8790) of a 1.5-Ci tritium release on August 30, 1974 from a 

contaminated shipping container (“pressure cooker”) provides air survey, bioassay, and smear 

survey results that can be used to model similar releases. Such a model can be scaled to account 

for the source term and applied to incidents prior to the 1973 environmental tritium release when 

such tritium monitoring data are not available for Rocky Flats. The baseline information from 

these data can also be used to model the pre-1973 background tritium environment at Rocky 

Flats because the 1974 release described in the RFAO report occurred close enough in time to 

the seminal 1973 tritium event that many or most of the procedures and workplace practices had 

only begun to transition to account for the new sensitivity to tritium and its potential impact on 

Rocky Flats operations. 

The number and nature of reported tritium release events, both before and after 1973, provide the 

basis for assumptions of pre-1973 workplace release frequencies, quantities and chemical forms. 

The parameters of this model can then be used to estimate pre-1973 bounding doses to Rocky 

Flats workers from estimates of the tritium background environment and tritium release 

incidents, particularly those involving contaminated shipping containers. 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

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PART II: Rocky Flats Tritium Dose 

Assignment for 1973 and Later 

E. M. Brackett, ORAUT 

Dose Assignment for 1973 

The report, Investigation of the Tritium Release Occurrence at the Rocky Flats Plant (SRDB 

24165, PDF p. 16), describes a 1973 incident that prompted the site to sample a number of 

workers for tritium exposure (also referred to as H-3). A shipment of scrap plutonium from 

LLNL was discovered to have been contaminated with tritium. This material was processed in 

Building 779A from April 9-25, 1973. Because the scrap was not immediately identified as 

being contaminated, monitoring of potentially-exposed individuals did not begin until late 

September 1973. 

Two-hundred-fifty people were sampled following the discovery; this included all employees 

who worked in areas in which the contaminated scrap was processed or who were involved in the 

processing of wastes from this scrap. Due to the large sample load, raw urine samples were first 

analyzed in many of the cases. It was noted that the counting efficiency was only about 3% for 

these analyses, and that the corrections made for spectral shift could lead to abnormally-high 

readings. Nineteen employees were initially identified as having elevated tritium levels in their 

urine. These samples were distilled and re-analyzed. Upon this re-check, fourteen of these 

employees were found to be below the 10,000 pCi/L action level established by the site. The 

five most-exposed individuals were identified and details of their potential exposures, including 

bioassay results, are included in the above-cited investigation report. One of these five 

individuals is in NOCTS. 

Tritium contamination was associated with plutonium scrap material; therefore, H-3 doses will 

be assigned to all individuals who were monitored for plutonium in 1973. Doses will be 

assessed on an individual basis using reported H-3 bioassay results and any additional 

information in the NOCTS file. For those who were not monitored for H-3, dose will be 

assigned based on claimant-favorable assumptions. 

As previously discussed, the tritium release incident report (SRDB 24165) discusses the tritium 

sampling of two-hundred-fifty people as of 10/15/73. There are no results or specific sample 

dates given in the report for those individuals who did not exceed the H-3 bioassay action level 

of 10,000 pCi/L. Only five individuals were found to have results exceeding the action level so 

this current assessment assumes that they are the maximally-exposed workers in the incident and 

that those who were not monitored would not have been exposed at those same levels. 

Therefore, for the purpose of this current tritium assessment, 10,000 pCi/L is used as the 

maximum H-3 bioassay result for those who were not monitored.
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Based on this information, the following assumptions were applied: 

 H-3 was in the form of tritiated water (HTO) 

 IMBA was used to model intakes for inorganic H-3, as described in Guidance on Use of 

IMBA Software for DOE Safety Applications (DOE, 2006) 

 Mode of intake was injection (for modeling with IMBA) 

 Intake date = 4/9/1973 (first day the material was processed) 

 Sample collected on 10/15/1973 

 Result = 10,000 pCi/L (14,000 pCi/day) 

Using the IMBA model, which is in agreement with values obtained from Rad Toolbox, the total 

dose is 49 mrem. Attachment A contains details and justification for the model used in IMBA. 

Dose Assignment for 1974-1975 and Post-1975 

ORAUT performed a co-worker study using data from NOCTS for 1974 and 1975. There are 38 

individuals with tritium data in 1974 and 37 in 1975. ORAUT-OTIB-0075, Use of Claimant 

Datasets for Coworker Modeling, provides justification and guidance for the study. 

When assessing tritium intakes for most sites, it is assumed that intake potential exists only while 

tritium bioassay monitoring is being performed because monitoring is cheap, easy, and requires 

only spot samples, thus presenting less of a burden than other forms of bioassay on both the 

employer and the employee. Because tritium was not of primary concern at RFP and was 

present only as a potential contaminant on equipment, a given individual was not placed on a 

routine tritium sampling program. Instead, a program was established whereby one-tenth of the 

urine samples collected for plutonium analysis were also analyzed for tritium content (SRDB 

111267, letter from RFP General Manager to RFAO AEC Manager) as well as the collection of 

samples when a particular concern was identified. Samples available in NOCTS for these two 

years indicate that analyses were performed throughout the year, with most individuals sampled 

only once. 

For the purpose of the co-worker study, it was assumed that each worker had the potential to be 

exposed at a constant level throughout the year in which the urine sample was collected. The 

95th percentile was used because one-tenth of the population was sampled. The co-worker study 

for 1974 -1975 yielded doses of much less than 1 mrem for everyone. The file, Tritium for 1974-

1975 coworker.xlsx, contains the assumptions employed in the study. 
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For the post-1975 years, there are 11 or fewer individuals in NOCTS with tritium data; this is 

insufficient for performing a co-worker study. Results for these years are consistent with those 

from the previous years and show a general decreasing personnel exposure trend. The dose from 

the 1974-1975 co-worker study (i.e., 0 mrem - see above) will apply to these years. 

The ORAUT analysis of the post-1973 tritium exposures yielded information that suggests very 

low personnel doses and very little tritium exposure potential. Therefore, no additional 

unmonitored dose due to tritium, as it relates to the assessment performed in this analysis, will be 

assigned after 1973 at RFP. 

Attachment A - Tritiated Water Models 

Thomas LaBone, Nancy Chalmers, and E. M. Brackett, ORAUT 

Introduction 

IMBA2offers the ability to evaluate intakes of organically-bound tritium (OBT) using urine 

bioassay. The biokinetic model used for OBT in IMBA, which is the ICRP 56 OBT biokinetic 

model [ICRP(1990)] with the addition of a urinary bladder, is shown in Figure A1-1 below (the 

diagram is from the technical documentation provided with IMBA). 

Figure A1-1: IMBA Biokinetic Model for OBT 

IMBA does not natively offer the ability to evaluate intakes of tritiated water (referred to as 

inorganic tritium in IMBA) using urine bioassay. A workaround for this limitation is offered in 

DOE-HS-0002, Guidance on Use of IMBA Software for DOE Safety Applications (SRDB 

 

2

 IMBA Professional Plus V4.1.18 
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33212). This workaround consists of changing the transfer rate constant going from the Transfer 

Compartment to Total Body 1 from 0.5[ln(2)/0.25d] to 0.97[ln(2)/0.25d] and changing the 

transfer rate constant going from the Transfer Compartment to Total Body 2 from 

0.5[ln(2)/0.25d] to 0.03[ln(2)/0.25d], which effectively converts the OBT model to the tritiated 

water model. With this workaround, IMBA can provide the instantaneous urinary excretion rate 

ėu (t) and the 24-hour incremental urinary excretion Δeu(t) at time = t days after intake. The 

instantaneous concentration of tritium in the urine Cu(t) is obtained by dividing the instantaneous 

urinary excretion rate by the daily urine output of 1.4 liters per day. The ICRP 88 biokinetic 

model for instantaneous urine concentration [ICRP(2001)] is given by dividing the content of the 

three systemic compartments3

at time = t days after intake by the volume of free body water (42 

liters). In the discussion below, we provide detailed calculations of the IMBA tritiated water 

biokinetic model and compare it to the ICRP 88 tritiated water biokinetic model. The 

calculations are performed in the statistics software R [The R Team(2013)] and are reproducible 

(i.e., the code can be copied from this document, pasted in R, and executed to give the same 

results given here). 

Calculations 

To calculate the IMBA and ICRP 88 urinary excretion functions we need to define and solve the 

system of differential equations based on the ICRP 56 biokinetic model shown above. Note that 

in R, log(x) is the natural logarithm of x. The biokinetic model is defined below. 

#Rate matrix 

k <- matrix(data=0,nrow=6,ncol=6) 

#radioactive decay constant (in units of days) 

lambda <- log(2) / (12.32 * 365.25) 

#Name the compartments (makes life easier) 

xfer <- 1 

tbA <- 2 

tbB <- 3 

other <- 4 

bladder <- 5 

urine <- 6 

#Define transfer and total removal rate constants (in units of 1/day) 

k[xfer,tbA] <- 0.97 * log(2)/0.25 

k[xfer,tbB] <- 0.03 * log(2)/0.25 

k[tbA,bladder] <- log(2)/10 * 1.4/3 

k[tbA,other] <- log(2)/10 * 1.6/3 

 

3

 Transfer Compartment, Total Body 1, and Total Body 2. 
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k[tbB,bladder] <- log(2)/40 

k[bladder,urine] <- 12 

k[xfer,xfer] <- -(k[xfer,tbA]+k[xfer,tbB]) 

k[tbA,tbA] <- -(k[tbA,bladder]+k[tbA,other]) 

k[tbB,tbB] <- -(k[tbB,bladder]) 

k[bladder,bladder] <- -k[bladder,urine] 

k[other,other] <-0 

k[urine,urine] <-0 

#Define the content of each compartment at t = 0 

#Everything is in the transfer compartment 

q0 <- numeric(6) 

q0[1] <- 1 

The function qq below implements the eigensystem method for solving systems of first order 

linear differential equations, as discussed by [Jacquez(1985)] and [Polig(2001)], to give the 

content of a given biokinetic compartment at time t. Because we are starting out with a unit 

intake (e.g., q0 =1 Bq), this is also the fraction of the intake present in the biokinetic 

compartment (i.e., the intake retention function [IRF]). 

qq <- function(x,initial.burdens,rate.constants,comp) { 

K <- eigen(t(rate.constants))$values 

V <- eigen(t(rate.constants))$vectors 

M <- solve(V,initial.burdens) 

qq <- 0 

for (j in 1:nrow(rate.constants)) { qq <- qq + M[j]*V[comp,j]*exp(x*K[j]) } 

return(qq) 

} 

In the examples below,4the content of stable tritium in the cumulative urine compartment at t = 

10 days after an acute unit intake of stable tritium, and the 24-hour incremental urinary excretion 

of stable tritium, are given. 

t.bio <-10 

#cumulative urine 

qq(t.bio,q0,k,urine) 

## [1] 0.22375899 

#24-hour incremental urine 

qq(t.bio,q0,k,urine) - qq(t.bio-1,q0,k,urine) 

 

4

 A line starting with # is a comment and a line starting with ## is output from the R statement above it. 
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## [1] 0.01720243 

The excretion functions for radioactive tritium are easily derived by adjusting the stable 

functions for radioactive decay. The reason why we differentiate between stable and radioactive 

tritium is that incremental urine samples and instantaneous urinary excretion rates are most 

easily calculated with stable excretion functions that are subsequently adjusted for radioactive 

decay. 

#cumulative urine 

exp(-lambda*t.bio) * qq(t.bio,q0,k,urine) 

## [1] 0.22341458 

#24-hour incremental urine 

exp(-lambda*t.bio) * ( qq(t.bio,q0,k,urine) -qq(t.bio-1,q0,k,urine) ) 

## [1] 0.017175952 

As a side note, the incremental urinary excretion functions for tritiated water given in 

Radiological Toolbox V3.0.0 agree with those calculated above. For example, in Radiological 

Toolbox, Δeu(10) = 0.01718 compared to Δeu(10) = 0.01718 calculated above. 

The function dq below implements the eigensystem method for solving systems of first order 

linear differential equations to give the instantaneous rate of change of the content of a given 

biokinetic compartment at time t. The instantaneous rate of change of the stable tritium in the 

urine compartment is the instantaneous urinary excretion rate of stable tritium. The 

instantaneous urinary excretion rate for radioactive tritium is obtained by adjusting the stable 

excretion rate for radioactive decay. 

dq <- function(x,initial.burdens,rate.constants,comp) { 

K <- eigen(t(rate.constants))$values 

V <- eigen(t(rate.constants))$vectors 

M <- solve(V,initial.burdens) 

dq <- 0 

for (j in 1:nrow(rate.constants)) { dq <- dq + K[j]*M[j]*V[comp,j]*exp(x*K[j]) } 

return(dq) 

} 

The instantaneous urinary excretion rate ėu(10) of radioactive tritium is shown below, along 

with the instantaneous concentration Cu(10) of tritium in urine. 

#Instantaneous excretion (1/day) 

exp(-lambda*t.bio) * dq(t.bio,q0,k,urine) 

## [1] 0.016598922 
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#Instantaneous excretion (1/L) 

exp(-lambda*t.bio) * dq(t.bio,q0,k,urine) / 1.4 

## [1] 0.011856373 

The instantaneous concentration of radioactive tritium in the urine at t = 10 days calculated with 

the ICRP 88 model is shown below. The excretion rates calculated here using the ICRP 88 

approach agree with those given by [Potter(2004)]. For example, in Potter Cu(10) = 0.0124 

compared to Cu(10) = 0.01243 calculated below. 

exp(-lambda*t.bio) * ( qq(t.bio,q0,k,tbA) + qq(t.bio,q0,k,tbB) + qq(t.bio,q0,k,xfer) ) / 42 

## [1] 0.01242897 

The IMBA excretion rate (black line) is compared to the ICRP 88 excretion rate (blue line) in 

Figure A1-2 below. 

t.bio <- seq(0.1,200,by=0.1) 

n <- length(t.bio) 

Ins.IMBA <- numeric(n) 

for(i in 1:n) { 

Ins.IMBA[i] <- exp(-lambda*t.bio[i]) * dq(t.bio[i],q0,k,urine) / 1.4 

} 

Ins.88 <-numeric(n) 

for(i in 1:n) { 

Ins.88[i] <-exp(-lambda*t.bio[i]) * (qq(t.bio[i],q0,k,tbA) + 

qq(t.bio[i],q0,k,tbB) + qq(t.bio[i],q0,k,xfer)) / 42 

} 

plot(t.bio,Ins.IMBA,type="l",log="y", ylab="Instantaneous Urinary Excretion Rate", 

xlab="Days After Intake") 

lines(t.bio,Ins.88,col="blue") 

abline(v=30,col="red",lty=6) 
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Figure A1-2: Comparison of IMBA Excretion Rate (black) and ICRP 88 Excretion Rate (blue) 

The ICRP 88 model predicts a higher excretion rate than the IMBA model at all times after 

intake, which is a result of adding the contents of the OBT compartment into the free-body water 

pool in the ICRP 88 model. We consider this to be physiologically-inconsistent with the ICRP 

56 biokinetic model5. Thus, the ICRP 88 model is an approximation of convenience that allows 

one to readily model the tritium urine concentration results, as was done in ICRP 54 

[ICRP(1989)], which used a biokinetic model that consisted of a single free-body water 

compartment having a 10-day half-life. For reference, t = 30 days is indicated on the plot as the 

vertical red line. The significance of 30 days is that it is probably the greatest length of time 

between urine samples one would observe in a routine occupational monitoring program. The 

tritium concentrations predicted by the two models differ by ∼ 9% at t = 30 days, which is an 

insignificant difference when modeling intakes of tritiated water in an operational radiation 

protection program. At t = 200 days post-intake, the excretion rates differ by ∼ 90%. It is our 

opinion that the ICRP 88 approximation is not applicable at such extremely long times 

post-intake and that the ICRP 56 model, as implemented in IMBA, should be used. 

 

5

 The ICRP never really explains how it is possible for the tritium in a compartment having a 40-day half-life to be 

evenly distributed in a free-body water compartment that has a half-life of 10 days. 
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#Ratio at 30 days post intake 

t.bio[300] 

## [1] 30 

Ins.88[300] / Ins.IMBA[300] 

## [1] 1.0886159 

#Ratio at t = 200 days 

t.bio[n] 

## [1] 200 

Ins.88[n] / Ins.IMBA[n] 

## [1] 1.9191289 

Intake and Dose Example 

To illustrate the differences in the IMBA and ICRP 88 models, both are used to evaluate a spot 

urine sample having a concentration of 10,000 pCi/L collected 187 days after an acute uptake of 

tritiated water. The intake-to-dose conversion factor (DCF) in units of mrem/pCi is from 

Radiological Toolbox6

. 

Result <-10000 #pCi/L 

num.days <-187 

DCF <-6.67E-8 #mrem/pCi 

First, the intake (Result / irf) in pCi and 50-year committed equivalent dose (DCF * Result / irf) 

in mrem calculated with IMBA. 

irf <-exp(-lambda*num.days) * dq(num.days,q0,k,urine) / 1.4 

irf 

## [1] 1.4285345e-05 

Result / irf 

## [1] 700018095 

DCF * Result / irf 

## [1] 46.691207 

Then, the intake and dose is calculated with ICRP 88. 

irf <- exp(-lambda*num.days) * (qq(num.days,q0,k,tbA) + qq(num.days,q0,k,tbB) + 

qq(num.days,q0,k,xfer)) / 42 

 

6

 IMBA gives a slightly higher DCF of 6.76E-8 mrem/pCi 
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irf 

## [1] 2.7392236e-05 

Result / irf 

## [1] 365066948 

DCF * Result / irf 

## [1] 24.349965 

The dose calculated with the IMBA model is approximately a factor of 2 higher than the dose 

calculated with the ICRP 88 model. 

References 

[ICRP(1989)] 

Individual Monitoring for Intakes of Radionuclides by Workers, ICRP Publication 54, Elsevier. 

[ICRP(1990)] 

Age-dependent Doses to Members of the Public from Intake of Radionuclides Part 1, ICRP 

Publication 56, Elsevier. 

[ICRP(2001)] 

Doses to the Embryo and Fetus from Intakes of Radionuclides by the Mother, ICRP Publication 

88, Elsevier. 

[Jacquez(1985)] 

Jacquez, J., Compartmental Analysis in Biology and Medicine, The University of Michigan 

Press, 2nd ed. 

[Polig(2001)] 

Polig, E. (2001), Modeling the Distribution and Dosimetry of Internal Emitters, Health Physics 

81(5):492–501.

[Potter(2004)] 

Potter, C. A. (2004), Application of the ICRP Clarification of the Tritium Metabolic Model, 

Health Physics 87(4):375–381.

[The R Team(2013)] 

The R Team (2013), R: A Language and Environment for Statistical Computing, Internet: 

http://www.R-project.org. 
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PART III: Example RFP Tritium Dose Reconstruction 

Mutty Sharfi, ORAUT 

Employee Information 

Cancer Description: Lung (ICD-9: 162); diagnosed 12/31/2000 

Prostate (ICD-9: 185); diagnosed 12/31/2000 

BCC (ICD-9: 173); diagnosed 12/31/2000 

SCC (ICD-9: 173); diagnosed 12/31/2000 

Year of birth: 1932

Gender: Male 

Smoking: Never Smoked 

Ethnicity: “White, non-Hispanic” 

Employment Information 

Start date: 01/01/1959 

End date: 12/31/1975 

Occupation: Unknown 

Dosimetry Data: None 

Organ Dose Assessed

Table A-7: Organ Dose Assessed

Cancer External Organ Used Internal Organ Used

Lung Lung Lung

Prostate Urinary Bladder Heart Wall1

Skin Skin Skin

Source: ORAUT-OTIB-0005 

1 Non-metabolic organ with the highest dose 

External Dose

Not applicable for tritium exposures. 

Internal Dose 

 Pre-1973: The 1.5-Ci tritium release from a contaminated shipping container occurred on 

August 30, 1974. The largest reported bioassay result (SRDB 8790) collected after the 

incident was used to assess the potential exposure from this release. The resulting dose is 
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was about 0.15 mrem. Assuming this event occurred every workday of the year (250 times a 

year), the resulting annual dose would be about 38 mrem/year. 

 1973: A tritium incident associated with contaminated scrap occurred in Building 779A, 

Room 154, in mid- to late-April 1973. Because of this incident, the site sampled a number of 

workers for potential H-3 exposure (SRDB 24165). The incident report indicates that 250 

people who were determined to have exposure potential to this incident were sampled as of 

October 15, 1973. Two-hundred-forty-five of the 250 individuals were found to have results 

less than the action level of 10,000 pCi/L. This action level was employed to identify those 

individuals who needed follow-up sampling. It is assumed that those individuals who were 

not monitored would have also not exceeded the action level. Therefore, the action level will 

be used as the maximum bioassay result for those who were not monitored, given that no 

results or dates were provided for those individuals below that level. An analysis of the 

potential missed dose from a bioassay result at the action level resulted in a total dose of 49 

mrem. This dose will be assigned to all unmonitored workers. 

 Post-1973: ORAUT performed a co-worker study using data from NOCTS for 1974 and 

1975 in accordance with ORAUT-OTIB-0075, Use of Claimant Datasets for Coworker 

Modeling. The 95th percentile annual dose was less than 1 mrem. Therefore, no dose will be 

assigned for unmonitored tritium after 1973. 

Uncertainty 

All doses are applied as a constant distribution. 

Summary 

The assessment methods presented in this report define the methods by which a dose estimate 

can be determined for the evaluated worker class. These methods support NIOSH’s conclusion 

that the operationally-related internal dose for the evaluated worker class can be bounded. A 

summary of the doses and probability of causations are provided in Table A-8 below. 

Table A-8: Example RFP Tritium DR - Summary of Doses and Probabilities of Causation

Cancer External (rem) Internal (rem) Total (rem) Probability of Causation

Lung 0.000 0.574 0. 574 3.73%

Prostate 0.000 0. 574 0. 574 1.36%

Skin BCC 0.000 0. 574 0. 574 3.25%

Skin SCC 0.000 0. 574 0. 574 0.44%
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Appendix 2: Response to Work Group/SC&A Comments 

on the Rocky Flats Plant Tritium White Paper 

TIMELINE 

7/2013 – Board Working Group Meeting – developed issues that were responded to in the 

response to comments document. 

9/2013 – Board Working Group Meeting – the tritium white paper was reviewed and the 

three periods assessed in the white paper were discussed: 

- 1973 – Liz B. to send the WG and SC&A her IMBA files so that they may perform a 

comparative review of the proposed pre-1973 method. 

- Post-1973 (1974-1975) – WG/SC&A not in agreement at the meeting about the dose 

being less than 1 mrem. 

- Pre-1973 – discussions about the applicability of the 1974 incident data for the pre-1973 

period. 

10/2013 – AB Meeting – although a SEC class is recommended that covers the time period in 

question related to the tritium exposure, additional confirmation/agreement to occur in regard 

to the partial DR method for tritium in the SEC period. 

- Dr. Ziemer requested information on why the post-1973 co-worker model came up with 0 

dose when there was dose associated with the 1974 incident – ensure that the bioassay 

samples from the 1974 incident in a co-worker model. 

1/2014 – The SC&A report titled: SC&A Review of Part II, Rocky Flats Tritium Dose 

Assignment for 1973, Attachment A, was provided as an additional review response to the 

NIOSH tritium white paper based on Working Group tasking. Included in the email response 

associated with this SC&A review was an indication that this tritium dose assignment review 

only focused on the 1973 period, and that SC&A was awaiting a response for the pre and 

post-1973 methodologies presented in the NIOSH white paper. 
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COMMENT RESPONSES 

1. If bubbler data exists and can be compared, compare pre-1973 data to 1974 data. 

RESPONSE: Only environmental and stack effluent tritium results have been captured 

for Rocky Flats prior to 1973; no tritium bubbler data for RFP work areas have been 

found for the pre-1974 period. However, additional SRDB searches identified workplace 

tritium results obtained in September-October 1973 using cold traps – part of the effort 

by Rocky Flats to identify the source of the 1973 environmental tritium release. These 

data may be useful for comparison with the 1974 bubbler data, but they still represent 

results from work areas potentially affected by the April 1973 release. (See information 

in Item 2 below.)

2. Look at baseline survey data from 1973 (SRDB 68351) to see if comparisons can be 

made. NOTE: Recognize that bubbler data may be suspect based on a classified 

interview noting that the bubbler was only present during opening of the secondary 

container and not present when opening the primary container. 

RESPONSE: In response to the working group discussion of the documents referenced 

in the white paper:

 SRDB 111095 is a collection of hand-written records of survey and air sample logs, 

including bubbler sample results (1121 pages). The document contains information 

for the years from 1977-1982.

 SRDB 122712 is a collection of 1997 bubbler results analyzed and reported by 

Thermo NUtech (33 pages). There is no information in this source about other years 

at RFP. 

 SRDB 122550 is the official transcript of the NIOSH-ORAUT interview of a former 

RFP employee. The former employee indicates that RFP started using tritium 

bubblers when opening outer containers (not when opening inner containers 

containing the pits). This occurred in 1965 in the B771 downdraft room; however, no 

bubbler results for the period prior to 1973 have been found. The interviewee also 

indicated that the bubblers were positioned in front of the intake plenums of the 

exhaust systems to serve as alarming devices, and not to record routine airborne 

concentrations in the area. 

Based on additional research into the tritium release evaluation at RFP, ORAUT 

confirmed that smears, radioactive gas monitors, and cold traps were used in tracing the 

source of the April 1973 release; however, the only workplace air monitoring results 

reported were from cold trap samples. 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

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Radioactive gas monitor results were all from glove box atmospheres. SRDB 111284, pdf p. 75, 

states (bold added for emphasis): 

“A general survey using smear technique and subsequent radiochemical analysis at 

Building 123 was initiated in all buildings or specific areas of those buildings 

where the possibility of tritium was suspected. Smears were also taken inside 

glovebox lines in several areas. Most of the analysis for the latter group of smears has 

not been completed. In addition, air was monitored using Johnson Model 1055 or 

955 radioactive gas monitors and/or cold trap samplers in Buildings 774 and 779-

A. A bubbler sampler was installed to sample the Building 779-A exhaust air effluent 

and analysis for tritium was performed on water traps normally used as part of the 

stack sampler system for the Building 774 evaporator stack.” 

Table A2-1 summarizes the cold trap sample data presented on pdf p. 79 in SRDB 111284. 

Table A2-1: RFP Cold Trap Samples – Air 

Building Room Date H-3 

(pCi/m3)

Remarks

774 203 9-28-73 20.7 none

220 9-28-73 9.2 none

210 10-1-73 14 none

320 10-1-73 15 none

779-A 154, NE 9-26-73 1,580 none

154, NE 9-28-73 10,000 none

154, NE 10-1-73 1,068 none

154, NE 10-2-73 451 none

154, NE 10-4-73 302 none

154, SW 9-26-73 1,491 none

154, SW 10-1-73 400,750 none

154, SW 10-2-73 113 none

154, SW 10-4-73 5,540 none

001 10-4-73 3,700 Sampling from above liquid level in 

building process holding tanks

142 10-4-73 12,146

Boiler ventilation room. Filtered air passes 

through room and is recycled back to dryers 

and laboratories
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

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NOTE: The average and standard deviation of the above results are: 

 Building 774: (14.7 ± 4.7) pCi/m3

 Building 779-A, Rm 154 NE and SW: The documentation offers no explanation for 

the high result of 400,750 pCi/m3on October 1, 1973. 

- Calculation including the high value: (46,810 ± 132,766) pCi/m3 

- Calculation excluding the high value: (2568 ± 3466) pCi/m3

Readings taken in Building 777, Rm 452 in the 31⁄2 months prior to the 1974 tritium 

contamination incident had average and standard deviation of (5343 ± 4518) pCi/m3. 

Building 779-A, Rm 154 housed the glove box hydriding reaction chamber where 

tritium-contaminated Pu from LLL was processed in April 1973, resulting in the 

highly-publicized environmental tritium release to public drinking water supply 

reservoirs. The resulting plutonium hydride was oxidized in other glove boxes in 779-A, 

Rm 154 before transfer to Bldg. 771 for reduction to Pu metal. Bldg. 771 process wastes 

were then transferred to Bldg. 774 for further processing, or were sent either to the solar 

evaporation ponds or the sanitary sewer. 

Glove boxes in Building 779-A, Rm 154 and in Buildings 771 and 774 were all found to 

be contaminated with tritium after the 1973 environmental release. It is interesting to 

note that, even though Bldg. 774 glove boxes were tritium-contaminated, the Building 

774 work area cold trap samples showed extremely low tritium results. It appears that the 

glove boxes provided good containment. 

ORAUT also reviewed the available NOCTS claims that had tritium bioassay data to 

determine the existence of a pre-1973 bioassay sampling program and to assess the 

sufficiency of the monitoring program for identifying potential tritium exposures and/or 

incidents. Five pre-1973 tritium bioassay samples for five different individuals were 

identified out 312 total sample results for 125 individuals (data ranging from 1966-1996). 

The five pre-1973 tritium sample results are: 

 Three urine samples, 1966: all background 

 One urine sample, January 1973: 5542 ± 846 (units not specified - assumption: pCi/L) 

 1 urine sample, April 1973: background 
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There do not appear to be any specific tritium incidents related to the collection of any of 

the pre-1973 bioassay samples. However, the fact that the samples do exist indicates that 

there was a capability for tritium urinalysis and a will to use it going back to 1966. The 

result from January 1973 is about 17% of the highest urine specimen from the 1974 

incident, which supports the use of the 1974 data to bound the pre-1973 tritium doses. 

To date, no information has been identified to dispute the use of the 1974 data in the 

development of a pre-1973 bounding approach for tritium at RFP. NIOSH-ORAUT will 

continue to assess the data to confirm that this continues to be the case and will address 

issues with the bounding approach if and when they arise. 

3. If the ChemRisk report is used for supporting dose reconstruction, look and see if the 

report was validated in any way. 

RESPONSE: The ChemRisk report was referenced and used in the development of the 

RFP Environmental TBD; however, no additional validation of the report data has been 

performed by ORAUT. While this TBD may be used to support dose reconstructions, the 

exposure scenarios associated with the ChemRisk data are not considered to be 

representative of the most highly-exposed individuals (i.e., the data are more 

representative of radiological conditions outside of the work areas and plants). The 

available personnel monitoring/bioassay data contained in an individual’s personnel 

monitoring records are considered the most representative and bounding from a personnel 

exposure perspective. 

4. Determine whether Pantex changed their shipping controls/survey criteria/shipping 

survey and contamination limits (did they change?) after the 1973 tritium release at 

Rocky Flats. If so, when did any changes occur? 

RESPONSE: Based on the available documentation, it appears that the earliest changes 

made by Pantex that were related to tritium-contaminated shipments were made in the 

early 1980s. Below is a summary of the documentation review: 

Pantex: 

 Based on the available documentation, it is not apparent that changes in the Pantex 

program in response to the 1973 or 1974 incidents (i.e., shipping controls/survey 

criteria/shipping survey and contamination limits) occurred until 1981 

(SRDB 107801). Other Pantex documentation in the SRDB corroborates this 

conclusion (i.e., no available information is dated earlier than 1981) (SRDB 109244; 

109245; 109246; 109255). 
White Paper: Follow-up Efforts on SEC-00192 Rocky Flats Plant Tritium Issues (Rev. 2) 

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contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

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distribution. 

RFP: 

 The 1974 incident occurred on September 3-4, 1974. Five RFP documents in the 

SRDB relate to the post-1974 incident follow-up: 

- SRDB 111267 (September 12, 1974) 

- SRDB 111288 (September 12-16, 1974) 

- SRDB 111301 (October 21, 1974) 

- SRDB 8789 (November 12, 1975) 

- SRDB 111106 (December 1974) 

 All these documents are related to the RFP’s post-incident responses, including: (1) 

implementation of RFP action levels; (2) RFP performance of tritium surveys of 

suspect shipments; and (3) RFP requests that sites shipping related packages to RFP 

perform their own surveys. 

 A June 6, 1974 memorandum from Rocky Flats to the AEC indicates adoption of an 

upper limit of 10 mCi tritium per kilogram of plutonium shipped into Rocky Flats 

(SRDB 111268). Certification of an incoming material’s history was required of 

shippers in response to AEC recommendations issued after the 1973 tritium release 

led to the realization that trace amounts of tritium could be found in almost all 

materials, thus pointing to the need for an acceptance limit. Incoming shipments that 

could result in excessive tritium levels at RFP continued to be monitored for 

verification. 

 ORAUT coordinated a request for information from RFP related to communication 

with Pantex regarding the implementation of control limits for shipments. RFP 

responded that no information was available (August 8, 2013 email from Rod 

Hoffman); since the time limit for retention of those records has expired, RFP 

believes that the documents may have been destroyed per the document 

retention/destruction schedule. 

ADDITIONAL COMMENT RESPONSE – DR. ZIEMER QUESTION 

1. The question of why the co-worker model came up with 0 dose when there was dose 

associated with the 1974 incident – was the bioassay samples from the 1974 incident 

included in the post-1973 RFP tritium co-worker model presented in the RFP tritium 

white paper. 

RESPONSE: The co-worker model was based on the analysis of the NOCTS claimant 

data. The assessed dose from the co-worker was less than 1 mrem per year, which, in 

terms of dose assignments for an individual DR under the EEOICPA program, results in 

a zero dose assignment for the purpose of calculating POC. All the NOCTS claimant 
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data available for 1974 were used in the co-worker study. While all the results from the 

1974 site incident report were not added in because details regarding the individuals were 

incomplete, the data/results that can be matched with NOCTS claimants (for two 

individuals) were used – data from the claimant’s NOCTS files; no data were added from 

the incident report. The results matched with NOCTS claimants included those for one 

individual identified as having the largest intake from the incident. It is noteworthy that 

the largest dose from the 1974 incident was only 0.15 mrem so inclusion of all of the 

results still wouldn’t yield a dose greater than 1 mrem. 

ADDITIONAL COMMENT RESPONSE – SC&A REVIEW OF TRITIUM WHITE 

PAPER 

1. SC&A reviewed the NIOSH tritium White Paper and provided comments and feedback 

on the tritium dose reconstruction method presented for the 1973 period at RFP in their 

paper titled: SC&A Review of Part II, Rocky Flats Tritium Dose Assignment for 1973, 

Attachment A.

RESPONSE: The primary NIOSH response to the SC&A review is that the SC&A 

analysis uses a draft model that is clearly identified as not for use at this time, which is 

acknowledged in the SC&A response. The Rule governing this program explicitly 

requires the use of currently approved ICRP models for the purpose of assessments and 

use of such unapproved models is outside of the scope of the NIOSH methodology. As 

such, NIOSH has not performed a detailed analysis of the model as it relates to 

EEOICPA dose reconstruction or the results provided by SC&A in their assessment. The 

general observation is that it should have very little impact on situations outside of the 

RFP because it only affects cases where urine samples are collected more than 100 days 

after intake, which should be a rare occurrence for tritium. It is noted that the SC&A 

paper matched the NIOSH White Paper values when the bioassay was collected 50 or 60 

days after the assumed intake. If the model is approved and issued by the ICRP, it will be 

reviewed for incorporation into the EEOICPA dose reconstruction program. 

One of the focuses in the SC&A assessment of the NIOSH Tritium White Paper was the 

analysis of Case A (from the RFP evaluation of the five highest exposed individuals from 

the 1973 tritium release incident). It appears that the SC&A assessment results are 

approximately the same as the results presented in the NIOSH White Paper for Case A 

when the same intake assumptions are used. The similar results occur when assessing the 

exposures based on the ‘best fit’ of the data in the model – the best fit scenario is not 

disputed by SC&A; rather, the SC&A assessment offers other possible exposure 

situations that were not considered plausible based on NIOSH’s review. The earlier 

intake date assumed by SC&A had been ruled out in the NIOSH analysis because Case A 

worked with Cases D and P in April and they did not exhibit similar excretion levels, and 

Case A’s elimination pattern exhibited a less-than-10-day half time, which is indicative 

of a relatively recent intake. In its review, the SC&A assessment concurs with the 
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NIOSH assessment of Case D. However, as it relates to Case A, SC&A does not address 

that workers A and D (and P) worked together in April 1973 on the same project. When 

considered, there is no support for the use of the SC&A assumptions for Case A that 

results in the significantly higher dose totals. Further explained, the likelihood of one 

individual receiving an intake of 92 mCi when co-located workers received no intake, is 

not plausible. NIOSH concludes that the nature of the exposure scenario does not 

support large differences in personnel exposure; rather, it supports the use of the NIOSH 

best fit analysis. 

The other details discussed by SC&A regarding the use of un-distilled versus distilled 

samples support the basis that the NIOSH assessment presents a claimant-favorable 

approach for tritium dose reconstruction in the SEC period. In addition to the above 

thoughts regarding the assessment of the tritium exposures for 1973, it is important to 

remember that the entire period being assessed for tritium falls in the currently 

recommended SEC period (through 1983). Therefore, NIOSH feels that the assessment 

for 1973, as well as the pre and post-1973 periods, represent NIOSH’s best and final 

approaches for reconstructing tritium at RFP within the associated time periods. 
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contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. 

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distribution. 

Appendix 3: Workplace Air Tritium Monitoring

at Rocky Flats, 1977-1981 

PURPOSE

NIOSH requested in May 2015 that ORAUT evaluate evidence of a robust workplace monitoring 

program in order to comprehensively close out the issue of RFP tritium exposure after 1973. 

This appendix establishes the locations and frequencies of workplace monitoring at the Rocky 

Flats Plant between 1977 and 1981. The existence of a robust workplace monitoring program at

RFP would support the validity of bounding occupational exposures to tritium during and after 

1973 using the analysis and co-worker model that ORAUT performed, as discussed in Appendix 

1, Part II of this tritium follow-up paper. 

METHOD

NIOSH has been unable to capture digitized records describing workplace tritium monitoring 

programs prior to the end of plutonium processing operations7(with which tritium releases and 

contamination incidents are closely linked). However, the SRDB contains three handwritten logs 

of analytical results for tritium collected by bubblers used for both environmental and workplace 

air sampling (SRDB 111095; 111157; 111189). One of these logs (SRDB 111095), spanning the 

period 4/1/1977 to 12/23/1981, was evaluated by noting the locations and results for bubbler 

samples of workplace air analyzed8during the first seven-day period of each year’s records 

beginning in April 1977 and the last seven-day period of December 1981. Any location logged 

to indicate that sampling was taken from an effluent system, such as a plenum or exhaust duct, 

was excluded. Other sampling sites not otherwise clearly marked were excluded when 

documentation was found indicating that they sampled an effluent system (e.g., SRDB 24164, 

PDF p. 19) or a glovebox environment (SRDB 122692, PDF p. 9). Locations marked as a Room 

or as a support column coordinate within a room were assumed to be workplace air sampling 

locations. 

RESULTS

Review of the selected log (SRDB 111095) identified 107 log entries for tritium bubbler sample 

results that are not associated with glovebox environments or effluents. The PDF page number, 

sampling location, date of analysis, and analytical result for each of these entries, grouped by 

 

7

 Plutonium-processing operations ceased subsequent to the FBI raid in 1989 (SRDB 8016, PDF p. 12). 

8

 Samples were typically analyzed within a week of collection, except over holidays. 
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location, is provided in an Excel spreadsheet (SRDB 144998). Results range9from 0 pCi/m3to a 

high of 7,920 pCi/m3. The high value was associated with the Disassembly Area (SRDB 24164, 

PDF p. 10) at Glovebox 452 (SRDB 118366, PDF pp. 2, 5). The average value is 152.5 pCi/m3

if ‘less than’ values are treated as zero. 

There are 17 separate locations in the 107 entries where bubbler results for tritium were logged. 

An occurrence matrix showing the bubbler monitoring locations and the number of analyses 

reported for each of the periods for which results were noted is shown in Table A3-1 below. 

Table A3-1: Occurrence Matrix for Bubbler Tritium Air Samples, April 1977 – December 1981

Bldg. Location

Number of Analyses*

Apr.

1977

Jan.

1978

Jan.

1979

Jan.

1980

Jan.

1981

Dec.

1981

374 First Floor - - 2 - - -

559 102 - - 1 - - -

771 181 - 1 1 - - -

771 305 - 1 - - - -

771 Rm 146 - 1 1 - - 5

771 Rm 149 - - - - - 4

771 Rm 174 - - 1 - - 4

774 220 - 1 - - - -

777 430, G-18 - - - - 5 4

777 430, K-15 - - - 1 - -

777 Rm 452, Downdraft 4 3 2 2 4 4

777 Rm 452, Col J-23 4 3 3 3 4 4

777 Rm 465 - - - - - 4

779A Rm 154 - 4 2 4 7 2

881 225 - - - - - 1

881 283 - 2 - 1 3 -

881 Rm 15 - - - - - 2

*These are the numbers of work-area bubbler samples analyzed during the first seven days of records for 1977-

1981, and for the last seven days of records for 1981.

 

9

 Values of zero do not appear in the record until after the first week of 1981; entries less than or equal to a value no 

greater than 170 pCi/m3 (presumably the detection limit) are used instead of zero prior to this time. 
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Monitoring frequencies were consistent in three of these locations during the five-year period: 

1. Building 777, Room 452 (Special Assembly) Downdraft, the location of tritium released 

from a contaminated shipping container on 8/30/1974 (SRDB 8790) 

2. Building 777, Room 452, Col J-23

3. Building 779A, Room 154, the Hydriding Laboratory (SRDB 118367, PDF p. 3) and location 

of glovebox #1363, where elevated tritium levels were seen just prior to Dec 5, 1977 (SRDB 

110903, PDF p. 2). 

The above areas were known to have elevated potential for tritium release into the workplace 

because of the prior incidents. Samples were normally retrieved from these locations three times 

weekly (Monday, Wednesday, and Friday). This sampling frequency was specified on log sheets 

prior to January 1978 (SRDB 111095, PDF p. 22) and in later radiological operating instructions 

(SRDB 24307, PDF p. 3). The same (Monday, Wednesday, and Friday) frequency was applied 

wherever glovebox environment and effluent monitoring for tritium was performed. 

Inspection of Table A3-1 above shows that areas where tritium release to the workplace was 

known to have happened in the past were monitored frequently and consistently in the five-year 

period from 1977-1981 and that other areas were monitored occasionally. Tritium limits were 

established after the 1973 release for workplace surface smears (0.005 μCi/100 cm2

), effluent air 

(2 μCi/m3), and room air (0.05 μCi/m3) (SRDB 4632, PDF p. 165). 

A brief review of two similar documents of handwritten tritium monitoring results for the years 

1974-1982 and 1974-1975, respectively, indicated similar monitoring frequencies and locations 

as those discussed here during years not included in this analysis (SRDB 111157; 111189).

SUMMARY AND CONCLUSIONS

Workplace air monitoring for tritium using bubblers was performed frequently and consistently 

at the Rocky Flats Plant after 1973 in areas known to have a significant potential for personnel 

exposure. Other areas were also monitored, but less frequently, perhaps on the basis of 

production activity with a potential for tritium release. Analytical results indicate a detection 

limit almost three orders of magnitude below the 0.05 μCi/m3limit for tritium in workplace air 

established by RFP management. The largest result noted for this analysis was 7,920 pCi/m3, 

which is 16% of the limit. 
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Rocky Flats continued to monitor workplace tritium well beyond the release incident in 1973 

with results indicating that tritium levels were normally quite low. NIOSH concludes that the 

use of a co-worker model for estimating and bounding tritium doses during normal operations at 

Rocky Flats is, therefore, appropriate.