The second of two Tennessee Valley Authority civilian nuclear reactors could get the license it needs to start producing tritium for U.S. nuclear weapons this year, a National Nuclear Security Administration (NNSA) official said on Thursday.

The government-owned Tennessee Valley Authority (TVA) already produces tritium for U.S. nuclear weapons by irradiating tritium producing burnable absorber rods in the Watts Bar Unit 1 reactor during normal operating cycles. The Pacific Northwest National Laboratory designs the rods for the NNSA, which extracts the tritium from the rods at the Savannah River Site in Aiken, S.C.

By Sept. 30 or sooner, Watts Bar Unit 2 in Rhea County, Tenn., will have the approval it needs to irradiate the tritium bearing rods, Kelly Cummins, NNSA’s program executive officer for strategic materials, said Thursday during a panel presentation at the ExchangeMonitor’s annual Nuclear Deterrence Summit. Exchange Monitor is a sister publication of Defense Daily.

TVA has “submitted a license amendment request to the nuclear regulatory commission to begin irradiation of these lithium rods in Watts Bar 2 [and] we expect that license amendment to be approved this fiscal year,” Cummins said.

With both Watts Bar Unit 1 and Watts Bar Unit 2 pumping out tritium, NNSA should be able to meet its goal of producing nearly three kilograms of tritium every 18 months by 2027, Cummins said. The reactors have to burn U.S.-origin fuel when irradiating the rods, since commercially available fuel may not be used for weapons programs, by international convention.

Cummins told sister publication Nuclear Security & Deterrence Monitor that NNSA still believes Watts Bar 2 will begin irradiating tritium rods in November 2020.

Tritium increases the explosive power of thermonuclear weapons. The gas degrades relatively rapidly, so the U.S. must refill the tritium reservoirs of existing weapons every few years.

In response to an audience question, Cummins said NNSA did not plan to produce tritium at TVA’s Sequoyah reactor in Hamilton County, Tenn., which is  also licensed for that purpose.