When the Tennessee Valley Authority’s Watts Bar Unit 2 nuclear reactor reactivates from a refueling outage that started Oct. 26, it will begin producing tritium for nuclear weapons for the first time, a National Nuclear Security Administration spokesperson said Monday.
The specialized rods will start producing yield-boosting gas for nuclear weapons during Watts Bar Unit 2’s Cycle 4. Watts Bar Unit 1 already makes tritium and is on its 17th fuel cycle.
The Tennessee Valley Authority (TVA) loaded Watts Bar Unit 1 was loaded with 1,792 tritium producing burnable absorber rods for its current cycle; Unit 2 is supposed to get 900 rods for its first tritium-producing cycle, according to the National Nuclear Security Administration’s (NNSA’s) 2021 budget request.
The semi-autonomous Department of Energy nuclear-weapons agency is in the early phases of four major nuclear-weapons refurbishments and needs to up the tritium output of the Watts Bar reactors to about 2,800 grams by Sept. 30, 2025.
The Pacific Northwest National Laboratory tritium designs tritium producing burnable absorber rods, which WesDyne fabricates near Columbia, S.C.
TVA irradiates the rods under an interagency agreement with NNSA and must burn U.S.-government uranium for any reactor cycles that produce tritium, since the gas is used for nuclear weapons. NNSA reimburses the Tennessee Value Authority for tritium production, paying the federally owned corporation a fee for each burnable rod it irradiates.
The NNSA provides the fuel for tritium irradiation from its own stock of highly-enriched uranium, which BWX Techologies subsidiary Nuclear Fuel Services converts to low-enriched uranium suitable for the Watts Bar reactors. The company’s seven-year, $505-million contract for the downblending, awarded in 2018, runs through 2025.
After the Tennessee Valley Authority irradiates the rods, the NNSA harvests the resulting tritium at the Savannah River Site in Aiken, S.C., where the agency puts the gas into reservoirs that are sent to NNSA’s Pantex Plant in Amarillo, Texas, to be installed in nuclear weapons. The half life of tritium is about 12.5 years, so the NNSA has a constant demand for more of the gas.
Editor’s note, 03/02/2021, 7:12 p.m. Eastern time: the story was updated with the correct target date for obtaining 2,800 grams of tritium per reactor cycle from the Watts Bar reactors.