The Defense Nuclear Facilities Safety Board wants the Department of Energy to address by early January 2023 whether a contractor in Washington state is being rigorous enough in overseeing a system critical to solidifying liquid radioactive waste at the Hanford Site.
In an Oct. 6 letter from Defense Nuclear Facilities Safety Board (DNFSB) Chair Joyce Connery to Secretary of Energy Jennifer Granholm, the board “requests a briefing within 90 days of receipt of this letter” on safety issues with the Tank Side Cesium Removal system. Ninety days from Oct. 6 is Jan. 4, 2023.
Tank Side Cesium Removal (TSCR) is a vital cog in the Direct Feed Low Activity Waste program to turn low-level radioactive tank waste into glass at the Waste Treatment and Immobilization Plant by the end of 2023. TSCR removes solids and cesium from tank waste prior to vitrification.
The board’s concern over the pretreatment system dates to an October 2021 contractor readiness assessment. DNFSB staff watched the contractor remove an ion-exchange column from TSCR and replace it with a new one: a chore that must be done every few months.
DNFSB staff said there was damage to the “threaded connections” or couplers used to connect the ion exchange columns to the system, according to Connery’s letter.
As a result, DNFSB staff concluded the contractor’s evaluation and repairs don’t meet safety requirements of the American Society of Mechanical Engineers for nuclear quality assurance, according to the letter.
Washington River Protection Solutions did not do a rigorous analysis on what caused the damage to multiple threaded connections. As a result, there is no assurance the repaired connections will satisfactorily perform the needed safety function over the system’s 50-year design life, DNFSB said.
Washington River Protection Solutions and DOE rely too much on “skill of the craft” to ensure the connections have adequate thread to hold together in the event of a flammable gas explosion, DNFSB said.
“The Department is committed to the safety of its workforce and the safe treatment of all waste stored in Hanford’s underground tanks,” a DOE spokesperson said via email, adding that a briefing will be held for DNFSB.
During the October 2021 outage cited by DNFSB, “ workers also evaluated and confirmed the design of existing threaded connectors, called couplers; and strengthened radiological protection practices,” the DOE spokesperson said.
The Amentum-led Washington River Protection Solutions, Hanford’s tank-waste prime, “contends that the type of material used for the components, the low service temperatures, and the lack of chloride sources make the risk of pitting or crevice corrosion over the 50-year life of the components extremely low, despite the potential for cracks” in the material, DNFSB said.
DOE concurred with its contractor, the board said.
The Tank-Side Cesium Removal project, now in a planned outage, has pre-treated 380,000 gallons of tank waste in two batches since it started up in January.
DOE expects to have 1 million gallons pre-treated before glass-making commences at the Waste Treatment and Immobilization Plant. The vitrification operation is targeted to start by the end of 2023 although DOE has federal court approval to delay that into 2024 if necessary.
