The Department of Energy said Friday it wants to do more plutonium chemistry and experiments in an existing building at the Los Alamos National Laboratory as part of a plan to resume the lab’s production of fissile nuclear-weapon cores called plutonium pits.

The move would mean raising the amount of plutonium-239, or its equivalent, allowed in the lab’s Radiological Laboratory/Utility/Office Building: a tenfold increase to 400 grams from the current limit of just under 40 grams, DoE’s National Nuclear Security Administration (NNSA) said in a draft environmental assessment.lanl

Modifying the Radiological Laboratory/Utility/Office Building to handle more plutonium would involve installing “additional enclosures and equipment,” the agency said. That would take eight to 10 years, it estimated. In its fiscal 2019 budget request, the NNSA estimated recategorizing the facility would cost roughly between $210 million and $340 million.

The public may comment on the NNSA’s draft for 30 days. Some time after the comment period closes, the DoE branch will issue a final environmental assessment that will bring it a step closer to starting the project. Congress will have to fund construction.

The Pentagon wants the NNSA to produce at least 80 plutonium pits a year by 2030. The agency plans to make at least 30 of these annually at Los Alamos by 2026 and is considering manufacturing all or some of the remaining 50 per year at the Savannah River Site in Aiken, S.C.

Technically, raising the limit on plutonium-239 would mean recategorizing the Radiological Laboratory/Utility/Office Building as a Hazard Category 3 Nuclear Facility: a designation that by law would actually allow the building to house more than 2,500 grams of plutonium-239, or its equivalent. The building is currently classed as a radiological facility.

Doing more plutonium chemistry and plutonium characterization — examining how the material responds to changes in temperature and pressure, for example — frees up more space in the laboratory’s main plutonium production building, the PF-4 Plutonium Facility. Without the proposed modifications to the Radiological Laboratory/Utility/Office Building, PF-4 would have to devote more of its potential production space to chemistry and characterization.