Congress’ final 2019 budget bill for the National Nuclear Security Administration, unveiled in detail Tuesday, would increase funding for maintenance and cleanup to buildings across the nuclear weapons complex, decrease funding for a controversial plutonium-disposal project and provide funding for the first time to make a low-yield, submarine-launched, ballistic-missile warhead.

The House and Senate are set to vote on the bill, part of a so-called minibus appropriations package that funds the Department of Energy and other federal agencies, this week. The measure has more than $15 billion for the agency’s semi-autonomous National Nuclear Security Administration (NNSA): the steward of the U.S. nuclear-weapons stockpile.

President Trump had not issued a statement of administration policy — a formal statement about whether he plans to sign or veto the bill — at deadline Tuesday for Defense Daily.

Congress had completed the bulk of its work on the minibus that includes NNSA’s 2019 budget by the middle of the summer, but political differences over funding for veterans programs prevented House and Senate lawmakers from ironing out the differences in their separate appropriations proposals until this week.

In what amounts to the biggest funding concession in the compromise bill, the Senate went along with the House’s plan to boost NNSA’s infrastructure and operations budget above the requested level. The account, which mostly funds maintenance and improvements at NNSA’s eight main field sites, would get about $3.1 billion in 2019, if Trump signs the bill. That is nearly four percent lower than the current budget, but about three percent more than requested for the fiscal year that starts Oct. 1.

Over the summer, the Senate’s proposed 2019 NNSA budget called for only about $2.8 billion in infrastructure and operations funding —  eight percent below the request.

Within the infrastructure and operations budget, NNSA’s maintenance and repairs account would get the biggest increase, relative to the request: more than 40 percent to $515 million for 2019.

Elsewhere in the bill, and in a potentially gloomy development for contractor CB&I AREVA MOX Services, Congress provided $220 million for the Mixed Oxide Fuel Fabrication Facility (MFFF) under construction at Savannah River: almost a 35 percent cut from 2018 levels, and in line with the White House’s request.

The long-delayed, over-budget MFFF was designed to turn surplus weapon-grade plutonium into commercial reactor fuel. NNSA wants to cancel that mission and dispose of the plutonium by other means, then turn MFFF into a factory for nuclear warhead cores called plutonium pits.

South Carolina opposes cancelling MFFF and has sued NNSA in federal court to stop it. The state won a temporary injunction from the South Carolina District Court in June that stopped NNSA from cancelling MFFF at least until early in fiscal year 2019. On Sept. 27, a federal appeals judge is set to hear oral arguments for and against lifting the lower court’s injunction.

In the meantime, Congress has approved its lowest MFFF appropriation since NNSA officially proposed cancellng the program as part of its 2017 budget request. In the past two appropriations cycles, support from House Appropriators and Sen. Lindsey Graham (R-S.C.) had been enough to get the facility a $325 million appropriation.

But this week, in the detailed explanatory statement accompanying the final 2019 NNSA budget bill, lawmakers said the agency would get only $220 million, which per the 2019 National Defense Authorization Act signed in August must be used to continue building MFFF. However, the authorization act gives Secretary of Energy Rick Perry the ability to cancel the construction, if he certifies NNSA’s alternative plutonium disposal method, dilute and dispose, is cheaper.

Perry is likely to exercise his opt-out authority. The 2018 National Defense Authorization Act contained the same authority, and Perry exercised it in May. Despite that, Congress has again ordered NNSA to keep building MFFF.

MFFF is a key cog in the NNSA’s plan to supply the Department of Defense with 80 plutonium pits a year. NNSA wants to make 30 of those fissile warhead cores a year at the Los Alamos National Laboratory, which is scheduled to start producing pits in 2026 and ramp up to 30 annually by 2030. By the same year, according to NNSA’s mostly unfunded strategy to convert MFFF into a pit plant, the South Carolina facility would be producing the other 50 pits a year needed to meet the Pentagon’s requirements.

Congress, which remains skeptical about NNSA’s pit production strategy, has ordered the agency to produce a detailed report on what it will take to finish the pit mission on schedule. The report would be due 120 days after Trump signs the 2019 NNSA budget bill, according to the measure’s explanatory statement. The statement also directed NNSA to include a detailed project data sheet for the Los Alamos plutonium-pit production project in the agency’s 2020 budget request. A project data sheet usually includes a project’s scope, justification, cost and schedule details.

The Senate, meanwhile, got its way with regard to $53 million in NNSA funding to continue development work on a so-called interoperable warhead, which could conceivably fly on future Air Force and Navy missiles. The warhead could fly on the Ground Based Strategic Deterrent missiles set to replace the Air Force’s current fleet Boeing [BA]-built Minuteman III intercontinental ballistic missiles beginning late next decade. Boeing and Northrop Grumman [NOC] are competing to build the new missiles under three-year Air Force development contracts awarded in 2017 and worth about $350 million and $330 million, respectively.

The House, despite the White House’s request to continue the Barack Obama administration’s interoperable warhead program, wanted to cancel the development effort and instead explore a large-scale refurbishing of the W78 warheads that tip the Minuteman III fleet now.

In a nod to the House, the 2019 NNSA budget’s explanatory statement directed the agency to compare the cost of the first planned interoperable warhead with the cost of refurbishing existing W78 warheads. The full report would be due 180 after the budget bill is signed, with a rough cost estimate due to appropriations committees 60 days after signing.

In less controversial matters, the 2019 NNSA budget bill would meet the White House’s funding request for the agency’s four ongoing nuclear-weapons life-extension programs. These programs are intended to keep weapons in service past their initial design lives and together account for about $1.8 billion in proposed 2019 funding. The life-extension programs are mostly run by the three U.S. nuclear weapons laboratories: the Los Alamos National Laboratory in New Mexico, which is the largest and oldest lab; the Lawrence Livermore National Laboratory in California; and the Sandia National Laboratory in New Mexico.

The 2019 NNSA spending bill also provides $65 million for the new low-yield, submarine-launched, ballistic missile warhead the Trump administration called for in February as part of its 2018 Nuclear Posture Review. However, Congress ordered NNSA to provide a more detailed funding request for the weapon in its fiscal year 2020 budget, which is notionally due the first week of February 2019. Sen. Dianne Feinstein (D-Calif.) said in an April appropriations hearing that the low-yield warhead would cost a combined total of $125 million in fiscal years 2019 and 2020.