The Nuclear Regulatory Commission allowed the Tennessee Valley Authority to work some people harder during an ongoing service outage at the Watts Bar 2 nuclear reactor, where the restart of tritium production for nuclear weapons has slipped to June from mid-May, the commission said.

The outage now “is now scheduled to be completed by early June 2022,” the commission said in a Friday Federal Register notice. The outage that started in March “was originally planned to be completed in mid-May, 2022,” but was delayed by bad weather and unidentified issues with the reactor’s new steam generators, the commission wrote.

In late 2020, Watts Bar 2 started irradiating tritium producing burnable absorber rods for the National Nuclear Security Administration (NNSA), joining Watts Bar 1, which has irradiated tritium since nearly 2003. NNSA is in the middle of scaling up tritium output at the civilian plants but has suffered some setbacks since Watts Bar 2 started producing in 2020, mostly tied to the steam generators.

To help minimize the additional downtime the reactor now needs, the Tennessee Valley Authority (TVA) sought and received permission from the Nuclear Regulatory Commission to give fewer days off to some of the people working on the ongoing Watts Bar 2 outage, according to Friday’s Federal Register notice.

In March, Watts Bar 2 shut down so that, in addition to receiving new fuel and tritium producing rods, TVA could replace all four of the reactor’s steam generators. The units were due to be replaced in 2023 but the Tennessee Valley Authority (TVA) decided to swap them out in 2022 instead after discovering the extent of the degradation during a fall 2021 outage. TVA also described problems with the Watts Bar 2 steam generators after a fall 2020 outage

Watts Bar 2’s fiscal year 2021 tritium output was about half what the NNSA hoped: 544 tritium producing burnable absorber rods instead of 922. 

NNSA is ramping up tritium production at the power plants — presently the weapons program’s only source of the relatively rapidly decaying, radioactive hydrogen isotope — to cope with the looming demands of the five major nuclear-weapon refurbishments scheduled for this decade. NNSA wants the two plants to produce 2,800 grams of tritium per cycle starting in fiscal year 2025, which begins Oct. 1 — substantially more than earlier estimates.

Tritium boosts the power of modern thermonuclear weapons but decays often enough that the NNSA must regularly replace the tritium reservoirs of each active weapon in the U.S. arsenal. Without the specified amount of the gas, the weapons will not retain their designed destructive power. 

Tritium from the TVA reactors is harvested at the Savannah River Site in Aiken, S.C.