The Defense Nuclear Facilities Safety Board favors having a national lab study the risk of a potential hydrogen explosion at a high-level radioactive waste vitrification plant being built at the Department of Energy’s Hanford Site in Washington state.
In a document dated July 19, the Defense Nuclear Facilities Safety Board (DNFSB), charged by Congress with making safety recommendations for DOE defense sites, reviewed an updated Preliminary Documented Safety Analysis for the High-Level Waste Facility at the Waste Treatment and Immobilization Plant.
The Preliminary Documented Safety Analysis considers accidents that rarely happen — major fires, explosions, earthquakes, natural disasters and the like — but could carry major risks for workers or the environment.
In 2021, the DOE Office of Enterprise Assessments gave a generally favorable review of evolving plans for the facility that would convert high-level waste into a glass-like form for eventual disposal.
Despite progress, the hydrogen control strategy “needs further refinement to ensure proper integration of safety into the design,” the DNFSB said. The DOE strategy leans heavily on high efficiency particulate air (HEPA) filters’ “ability to survive an explosion and prevent an unfiltered release” of radiation, the safety board said.
But an entity outside of the Hanford Office of River Protection, such as a DOE national laboratory, should be in charge of analyzing the HEPA filters’ ability to survive the explosion, the board said.
Likewise, more work should be done on a scenario where a volcano eruption sends ashfall onto the HLW facility, the DNFSB said. Project managers are looking at a passive safe shutdown of the facility should such an event occur.
But a passive shutdown would likely involve securing ventilation and other cooling systems, “which will cause the facility’s temperature to increase,” DNFSB said, adding the DOE analyses of hydrogen hazards do not consider a temperature rise.
“The Department and its contractor have taken actions to resolve the seven safety observations identified by DNFSB in its [earlier] April 2022 report,” a DOE spokesperson said in a Friday email. “Nuclear safety and engineering teams have made significant progress in resolving legacy technical safety issues and plans are in place to submit future revisions of the nuclear safety basis to resolve the remaining open issues.”
Amid safety concerns and whistleblower reports, DOE suspended construction of the high-level waste facility in 2012. But spending on the project resumed in the past couple of years.
A recently modified consent decree by a federal judge in Eastern Washington said construction of the high-level facility should be substantially complete by December 2030; cold commissioning should start by June 30, 2032 and hot commissioning by Dec. 31, 2033.
