The safest building at the Y-12 National Security Complex in Oak Ridge, Tennessee, is not safe enough. That is the conclusion of the Defense Nuclear Facilities Safety Board in an April 21, 2020, Staff Report on the storage of reactive materials at the Highly Enriched Uranium Materials Facility (HEUMF). The Staff Report was released on June 1, 2020, accompanied by a letter from Safety Board Chair Bruce Hamilton to Dan Brouillette, Secretary of Energy.

Faced with three separate discoveries of highly enriched uranium that posed an undetermined safety risk because it was pyrophoric, the contractor at Y-12, Consolidated Nuclear Services, without characterizing the materials, decided to re-categorize all the materials as not pyrophoric. NNSA agreed and took the additional step of ordering the contractor to revise the Documented Safety Analysis for the HEUMF to incorporate the material types into the facility safety basis. Neither action was justified, according to the Safety Board, and neither was sufficient to assure worker safety.

The HEUMF, less than ten years old, was designed to provide a safe, secure, fully modern, seismically qualified facility for the storage of certain forms and types of enriched uranium materials. The Y-12 National Security Complex has been called the “Fort Knox of Enriched Uranium;” in addition to storing highly enriched uranium, Y-12 uses HEU in the manufacturing of thermonuclear cores for US nuclear warheads and bomb. Y-12 also processes HEU to prepare it for use in naval nuclear reactors.

For the last decade, the National Nuclear Security Administration has attempted to reduce risks to workers by moving excess highly enriched uranium from work areas in deteriorating, but still operating, nuclear weapons production facilities. The program to move the HEU is part of a site-wide “material-at-risk (MAR) reduction strategy.”

The Safety Board report suggests that in some frying-pan-into-the-fire instances, the danger to workers has moved with the material. On at least three occasions, the contractor at Y-12, Consolidated Nuclear Services, has discovered safety violations as a result of unauthorized transfer of enriched uranium materials to the HEUMF. The discoveries represented “unreviewed safety questions,” and violated the Documented Safety Analysis—the plan that governs the handling of dangerous materials and operations in order to assure safety is not compromised.

In the case of the HEU violations, which involved canisters of materials that were suspected to be capable of an “energetic exothermic event”—a term of art that includes explosions—NNSA and CNS took an unusual step in order to bring the canisters into compliance with safety rules. According to the Safety Board, they “re-categorized all materials that were originally considered ignitable and potentially pyrophoric as not pyrophoric.” The Safety Board reported that “As part of this re-categorization, materials previously determined to be pyrophoric were designated as either stable and acceptable…or ignitable.”

NNSA approved the change, and also ordered the contractor to revise the Documented Safety Analysis to include the material types in the facility’s safety basis.

The Safety Board reviewed all this activity and determined that NNSA and CNS made the changes without fully understanding what is in the canisters. The Safety Board also said the final safety documentation does not address potential internal hazards that could cause an “energetic event.” The Safety Board quotes the Department of Energy’s Primer on Spontaneous Heating and Pyrophoricity and reviews incidents at Y-12 that demonstrate the risks—spontaneous exothermic events have occurred in the past.

The Safety Board staff concludes: The staff team does not agree with Y-12’s determination that these materials are not pyrophoric, and, later: The staff team does not consider the existing credited control set adequate to prevent and mitigate internal hazards for these materials in storage at HEUMF.

The Safety Board also notes the revised Documented Safety Analysis no longer conforms to Y-12’s own site-wide standard: Criteria for the Safe Storage of Highly Enriched Uranium at the Y-12 National Security Complex.

“The dangers posed by highly enriched uranium are not paper threats. They are real. The words ‘energetic exothermic event’ can mean anything from a fire to an explosion to a nuclear criticality,” said Ralph Hutchison, coordinator of the Oak Ridge Environmental Peace Alliance. “The NNSA can not wish away real safety problems by changing words on paper, especially when they still contradict their own safety requirements.

“This report underscores the failure of Y-12 to prioritize safety. The whole point of the plan to move material-at-risk is to reduce the danger to workers. In this case, when they learned that they have created another dangerous situation, their response was to re-write the rules, and simply declare, without doing sampling, that they solved the problem.

“The Safety Board report tells us three things.

• One: Operations at Y-12, even those designed to reduce risks, continue to pose safety threats.

• Two: NNSA can not be trusted to do the right thing—it thinks doctoring the paperwork is an acceptable way of dealing with real risks to workers.

• Three: we need the Safety Board and its oversight—it is the only front-line accountability the public has.

“The public should know that this latest report is just the tail of the dragon. Y-12 continues to carry on with nuclear weapons production operations in facilities it has acknowledged are unsafe. NNSA has declared that it is simply accepting some risks—it won’t say how much or what kinds—on behalf of the public, and it will continue to do so for the next thirty years because making the buildings safe is ‘cost prohibitive.’”

The Safety Board requested a briefing from the Energy Secretary within 90 days.

The Safety Board’s letter and report can be found here: https://www.dnfsb.gov/sites/default/files/document/20936/Y-12 HEUMF Reactive Hazards %5B2020-100-036%5D.pdf