Another power-generation cycle is underway at the Tennessee Valley Authority’s Watts Bar Nuclear Plant Unit 1, one of two reactors in which rods that help the National Nuclear Security Administration top off the tritium reservoirs of U.S. nuclear weapons are irradiated.
The plant returned to operation on May 12 after a scheduled shutdown for maintenance and refueling that occurs about every 18 months. The outage began in mid-April. Irradiated tritium-producing burnable absorber rods (TPBAR), the source of weapons tritium, come out of the Watts Bar reactors during each refueling outage, and unirradiated TPBARs are inserted, according to a National Nuclear Security Administration spokesperson.
Watts Bar Unit 1 is now on its 19th power-generating cycle. The Tennessee Valley Authority (TVA) planned to carry 1,792 TPBAR in the reactor core for Cycle 19, according to a regulatory filing with the Nuclear Regulatory Commission dated April 27. That is the legal maximum the reactor can irradiate. TVA in March applied for a license amendment with the commission to increase the maximum TPBAR load to 2,496 TPBAR.
The quasi-government corporation hoped to get its license amendment in time to increase Unit 1’s TPBAR load during the next refueling outage, tentatively scheduled for the fall of 2024. In its application to the Nuclear Regulatory Commission, TVA said the increase in TPBAR should qualify as exempt from environmental review.
While Watts Bar 1 was shut down, TVA completed upwards of 11,000 individual work activities, including replacing 92 of Unit 1’s 193 fuel assemblies. TVA also inspected reactor components and other systems “to ensure continued safe operation of all components, replaced or serviced plant equipment, and installed enhancements to help the unit continue safe, reliable operation for years to come,” according to a TVA statement released May 16.
Watts Bar Unit 1 is one of seven operational nuclear reactors overseen by the TVA and one of two in which TPBAR are irradiated. The National Nuclear Security Administration (NNSA) in 2000 gave Westinghouse Government Services a contract to fabricate TPBAR at the Columbia Fuel Fabrication Facility near Columbia, S.C.
TPBARs are specially designed rods that are inserted into nuclear fuel assemblies in substitution for normal nuclear fuel rods. Watts Bar 1 has irradiated tritium since nearly 2003. Unit 2 started producing tritium in late 2020.
TPBAR are irradiated at the Tennessee Valley Authority’s Watts Bar Unit 1 and Unit 2 reactors and are then shipped back to South Carolina for tritium harvesting by Department of Energy contractors at the agency’s Savannah River Site.
The tritium gets transferred to reservoirs that are installed in nuclear weapons. Modern thermonuclear weapons use tritium to increase the efficiency of nuclear explosions. Radioactive tritium decays relatively quickly and so must be produced regularly for as long as a nation wishes to maintain an arsenal of thermonuclear weapons.
