Conferences, Videos & Testimony

Index of Rocky Flats Plutonium "Source term" Reports

June 1, 1999

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(HTML page introducing a series of workshops on Rocky Flats)


One of the most difficult and controversial tasks facing the Rocky Flats historical public exposure studies was determining historical plutonium releases from the plant. Many official records were incomplete or destroyed. Excessive secrecy at the plant and within the US government meant that few public records existed when the exposure study started. At that time, wide differences existed about the magnitude of plutonium releases from the plant. For example, release estimates during the1957 fire varied between less than a gram to about 250 kilograms.

The fate of the entire study depended on the credible assessment of plutonium releases from the plant. Key to this effort was the development of "source terms" that would describe the magnitude and timing of plutonium releases from the plant. Developing credible source terms required the Health Advisory Panel (HAP), Radiological Assessments Corporation (RAC), MJP Risk Assessment, and ChemRisk to seek out records and other types of information, obtain the public release of information, and develop credible methodologies to estimate plutonium releases. This effort spanned the entire decade-long history of this project. It required the contractors, HAP, and members of the public to devote extensive resources to tackling a wide range of unique and difficult problems and to ensuring that information was released to the public.

Following phase 1 of the public exposure studies, HAP decided that more investigation of plutonium releases was needed. In particular, RAC was tasked to further evaluate the 1957 and 1969 fires and routine operations. The emphasis in these investigations was to reconstruct releases from the "inside," rather than to depend of existing environmental data to back-calculate a plutonium release estimate as was done in phase 1. The concern was that much of the environmental data from the first few decades of the plant’s operation were inaccurate, unreliable, or incomplete. This "inside-based" approach would turn out to be significantly more challenging than originally envisioned, but it would lead to a much deeper, and in many cases, new understanding of plutonium releases from the plant.

The phase 2 investigation of plutonium source terms coincided with major new commitments by the Department of Energy (DOE) to openness. DOE’s new policy made it much easier for RAC and HAP researchers to tour the principal buildings of concern, find information at the plant, and subsequently obtain its declassification. In certain cases, DOE headquarters in Washington, DC intervened directly to facilitate the location and declassification of critical information and declassify it. In addition, Paul Voillequé and other members of the RAC team were dogged in searching for information.

As RAC started to present its initial source term findings to the HAP and the public in the mid-1990s, many stakeholders were struck by the complexity of the analyses and the lack of time available at the regular HAP meetings to critique the new work. Because many of the presentations were based on overheads or slides and not written reports, the need for wide-ranging discussions among the researchers, HAP, and members of the public became pressing.

The Source Term Workshops

As a result, HAP-member David Albright organized a series of workshops where technical results could be presented and discussed in detail. These workshops, which were held from 1997-1999, were critical in RAC’s production of credible reports. Comments and discussions at the workshops led to many revisions in the assessments of the fires, with significant impact on the understanding of those fires and the final release estimates. The workshops also highlighted the interrelationships among the three cases. The development of release estimates for all three cases required a detailed understanding of accidents in the 700-series buildings, the history of operations in these buildings, and many properties of plutonium. As in any assessment of this nature, not all questions can be answered. In addition, some releases may have been missed, but no evidence of significant releases beyond those identified in the phase 1 and phase 2 studies have been found. A necessary caution is that saying "there is no evidence of additional releases" is not the same as concluding "no additional releases occurred."

Workshop reports

Extensive notes, compiled here, were prepared for four of the five workshops held between March 1997 and May 1999. The reports summarize presentations made by Paul Voillequé and others, and the comments and questions of the members of the public who attended the workshops. The reports were prepared by Kevin O’Neill, who also commented on the technical documents prepared by Voillequé.

The reader is referred to the Colorado Department of Public Health and Environment to obtain copies of the reports referenced in the workshop reports.

The March 1997 workshop, the first of the series, primarily covered plutonium releases from "routine" operations in buildings 771 and 776. The workshop also addressed releases from the 1957 fire in room 180 of building 71. Although it was intended that the 1969 fire should be discussed at this workshop, the questions and discussion on the other topics precluded a presentation on the 1969 fire.

The September 1997 workshop discussed Paul Voillequé‘s reanalysis of the releases from the 1957 fire in room 180 of building 71.

The December 1997 workshop returned to the topic of the 1957 fire, and also discussed the need to characterize uranium releases from the plant.

The May 1999 workshop again featured a presentation by Voillequé on the 1957 fire. In addition, this workshop featured a presentation by Michael Diliberto of Diliberto and Associates, who addressed the nature and propagation of the 1957 fire and the cause of the filter plenum explosion that resulted from the fire.

Related links on the ISIS web page:

  • The Lessons of Nuclear Secrecy at Rocky FlatsPress Release or Issue Brief
  • Photos of Rocky Flats can be found in this gallery.
  • Information about Making A Real Killing: Rocky Flats and the Nuclear West by ISIS Board member Len Ackland

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