A June 26 letter from the Defense Nuclear Facilities Safety Board has provided new insight into safety design features for the Y-12 National Security Complex’s Uranium Processing Facility.
Details regarding progress of the Tennessee facility have been something of a secret since the project was significantly reconfigured in 2014 to encompass a mix of new and existing buildings rather than one all-new structure.
A team review directed by the Senate Appropriations energy and water subcommittee prompted the revisions to rein in runaway costs. First projected to cost $650 million, the facility’s budget is now capped at $6.5 billion, and the subcommittee has mandated that the UPF design must be 90 percent complete before construction can begin.
Officials have said the plans should reach the 90 percent mark by September, with building starting by next year. Bechtel is designing and constructing the plant, through a subcontract with Y-12 prime Consolidated Nuclear Security, of which the company is a majority partner.
Construction is due to be complete by 2025, giving Y-12 a new source for uranium processing operations now conducted in aging facilities for the U.S. nuclear deterrent.
The National Nuclear Security Administration, the semiautonomous branch of the Department of Energy that oversees Y-12, has kept mum on the state of design without specifying why the information is being withheld.
In a June 26 letter to NNSA Administrator Frank Klotz, DNFSB Chairman Sean Sullivan noted concerns by board staff with the preliminary safety design report and preliminary fire hazards analysis for UPF.
The revised plans eliminate the majority of thermal barriers that existed in the previous designs, and would protect fissile material in the event of a fire caused by a major earthquake. Without thermal barriers, a specialized fire suppression system would aid in preventing nuclear criticality – a self-sustaining nuclear chain reaction. Board staff urged that the system planned for the UPF be designated as safety-significant, which would require more stringent design, acquisition, maintenance, and surveillance.
Additionally, the system’s diesel pumps do not have the necessary classification to ensure they would function if a design-basis seismic event occurred, the DNFSB found.
Board staff also raised concerns about the materials to be used in windows of UPF glove boxes that will contain material-at-risk (MAR), according to Sullivan. While industry associations call for noncombustible materials for glove-box windows, current plans for UPF call for a combustible material that has not shown an equal fire protection.
“Either using a non-combustible window material or demonstrating that the material selected by the UPF project provides equivalent performance would improve the reliability of the facility’s primary confinement for MAR,” the DNFSB said.
An April 2017, the DOE Office of Enterprise Assessments report took issue with the facility’s fire safety plans, indicating that sprinklers in high ceilings might be ineffective in suppressing a major blaze.
Uranium Processing Facility Project Office spokeswoman Courtney Branton declined comment on the facility’s fire safety provisions, saying the concerns were addressed to Klotz. Bechtel and Consolidated Nuclear Security have also declined to comment.
