With the end of the Cold War and breakup of the Soviet Union in the early 1990s, control of surplus nuclear weapons material became an urgent U.S. foreign policy goal. Particular U.S. concern focused on plutonium from Soviet nuclear warheads, which it was feared posed a major nuclear weap ons proliferation risk. The United States supported a successful effort to consolidate the storage of Soviet nuclear weapons and materials in Russia, and then began negotiating reductions in weapons material stockpiles. Congress has been closely involved in formulating U.S. policy on surplus plutonium disposition, as well as funding the necessary facilities, operations, and Russian assistance to implement the program. Because of sharply rising cost estimates for plutonium disposition facilities under construction in South Carolina, the Obama Administration proposed in its FY2017 budget request to end construction and pursue a "dilute and dispose" (D&D) option. The Trump Administration proposed the same strategy in its FY2018 budget request. In September 1998, the United States and Russia each agreed to convert 34 metric tons of surplus weapons-grade plutonium to a form that could not be returned to nuclear weapons under the Plutonium Management and Disposition Agreement (PMDA). The agreement was designed to ease concerns about the possible theft or diversion of weapons-grade plutonium by nations or others seeking to develop their own nuclear weapons. According to the agreement, the parties could use two methods for disposing of the plutonium—they could either convert it to mixed oxide (MOX) fuel for nuclear power reactors or immobilize it and dispose of it in a way that would preclude its use in nuclear weapons. However, Russia had expressed little interest in the permanent immobilization and disposal of plutonium, or burning it in conventional reactors, preferring to use the material as fuel for its civilian fast reactor program. The United States initially intended to pursue both immobilization and MOX fuel for conventional reactors. However, after reviewing U.S. nonproliferation policies in 2001, the Bush Administration concluded that the dual approach would be too costly. Instead, it outlined a plan for the United States to convert almost all its surplus plutonium to MOX fuel. The PMDA was amended with a Protocol which entered into force on July 13, 2011. The PMDA Protocol renewed the commitment of each side to dispose of 34 metric tons of weapons-grade plutonium. It also laid out conditions for Russian use of the plutonium as fast reactor fuel, including restrictions on breeding additional plutonium in fast reactors. The two countries agreed to begin plutonium disposition in 2018. The United States pledged to pay $400 million to support the Russian plutonium disposition. The Russian government was to fund the remainder of the approximately $2.5 billion in estimated costs. The plutonium disposition program, including U.S. assistance for the Russian program, is administered by the National Nuclear Security Administration (NNSA), a semiautonomous agency of the Department of Energy (DOE). A key component of the U.S. strategy for disposing of surplus weapons plutonium has been the Mixed Oxide Fuel Fabrication Facility (MFFF) at DOE's Savannah River Site in South Carolina. NNSA estimated in 2002 that MFFF would cost about $1 billion to design and build. That estimate had risen to $4.8 billion when the construction of MFFF began in 2007. According to DOE's FY2014 budget request, the MFFF contractor then estimated that the project's total construction cost would rise to $7.78 billion, and that construction would not be completed until November 2019. DOE slowed construction during FY2013 and FY2014 while other disposition options were evaluated. DOE's FY2015 budget justification said the total lifecycle cost of the MOX fuel program for plutonium disposition—including construction, operations, waste management, and facility decommissioning—had risen to $30 billion. Because of that increase, according to DOE, "the MOX fuel approach is not viable within the available resources." DOE planned to put MFFF and related facilities currently under construction in "cold standby," reducing funding for the U.S. plutonium disposition program from $560.3 million in FY2014 to $286 million in FY2015. DOE planned to "further analyze options to complete the plutonium disposition mission more efficiently." Congress rejected the Administration's plan to put MFFF in "cold standby" in FY2015. The FY2015 National Defense Authorization Act ( P.L. 113-29 ) and the FY2015 Consolidated and Further Continuing Appropriations Act ( P.L. 113-235 ) each required DOE to conduct independent cost and schedule estimates for MFFF and analyze alternative disposition approaches. The two acts authorized and appropriated $345 million to continue MFFF construction at a reduced level from FY2014. DOE's FY2016 budget justification said that Aerospace Corporation had been contracted to carry out the required analyses, and, pending that decision, DOE requested $345 million for FY2016 to continue MFFF construction at the FY2015 level. The analyses of the MOX disposition program and the alternatives were concluded before submission of DOE's FY2017 budget request. "These analyses confirm that the MOX fuel approach will be significantly more expensive than anticipated and will require approximately $800 million to $1 billion annually for decades," according to the DOE budget justification. "As a result, beginning in FY 2017 the MFFF project will be terminated." DOE proposed reducing funding for MFFF from $340.0 million to $270.0 million to develop a termination plan and begin implementing it. At the same time, DOE planned to begin developing a "detailed lifecycle baseline" for diluting the plutonium for disposal in a deep geologic repository. Congress approved $15 million for DOE planning activities for the dilute and dispose option, but it also appropriated $335 million to continue MFFF construction in FY2017, a 1.5% reduction from FY2016 ( P.L. 115-31 ). In its FY2018 request to Congress, the Trump Administration supported the proposal to "terminate the MOX project and pursue the dilute and dispose strategy as an alternative." The FY2018 National Defense Authorization Act, enacted by Congress on November 16, 2017 ( H.R. 2810 ), requires DOE to continue MFFF construction unless the Secretary of Energy certifies that an alternative plutonium disposal option would cost less than "approximately half" of the remaining costs of building and operating MFFF. In addition, the Secretary would have to commit to remove surplus plutonium from South Carolina and "ensure a sustainable future for the Savannah River Site." Full-year FY2018 appropriations for the federal government have not been enacted. An omnibus FY2018 appropriations bill passed by the House ( H.R. 3354 ) would provide $340 million to continue MFFF construction in FY2018 and prohibit "the use of MOX funding to terminate the project while the Congress is considering an alternative approach for disposing of these materials." The Senate Appropriations Committee's FY2018 Energy and Water Development Appropriations bill ( S. 1609 ) accepted the Administration's request for $270 million to terminate MFFF construction and included $9 million for alternative plutonium disposal planning. The proposals by the Obama and Trump Administrations to cancel the MOX fuel disposition path have led to questions about whether and how the Russian government would need to agree to such a change to the U.S. disposition pathway. The amendments made to Article 3 of the PMDA by the 2010 Protocol may have provided for more flexibility in adjusting the disposition paths chosen by each country in the future. Nevertheless, any future change still would be subject to a written agreement by both parties. Article 3.1 states that the parties may agree "in writing" if they choose "other measures" of disposition: "Disposition shall be by irradiation of disposition plutonium as fuel in nuclear reactors or any other methods that may be agreed by the Parties in writing." Article 12 of the PMDA established a Joint Consultative Commission (JCC) to address implementation issues, and the JCC is the forum where any changes would be decided. The Department of State chairs the JCC on the U.S. side and DOE participates, in coordination with the White House. The Russian Atomic Energy Agency (ROSATOM) and the Russian Ministry of Foreign Affairs participate on the Russian side. U.S. officials appear to interpret the proposed change to a dilute and dispose method as falling under the Article 3.1 category of "any other methods." After a decision has been made about how to proceed with the U.S. program, the U.S. side would bring its proposal, and interpretation of whether it would require an amendment, to the Joint Consultative Commission. The Russian government would then evaluate the proposed change and would render its own interpretation of whether it would require an amendment. If the Russian side determines that a change falls within the scope of the current agreement, then an exchange of diplomatic notes or other written agreement would suffice. If the Russian government determines that the new proposed disposition path does not fall within the agreement's parameters, then it is possible that a new protocol to the PMDA would need to be negotiated. At a hearing held by the Subcommittee on Strategic Forces of the House Committee on Armed Services on October 7, 2015, Lieutenant General Frank G. Klotz, Administrator of the National Nuclear Security Administration (NNSA), testified that Secretary of Energy Ernest Moniz had discussed this issue recently with Rosatom head Sergei Kiriyenko. Lieutenant General Klotz said that in that conversation, the Russians recognized that the United States had been flexible when Russia wanted to change its disposal method in 2010, and said, "When you have a plan, come back to us and we'll sit down and negotiate."