Hiroshima Report 2018(11) IRREVERSIBILITY
A) Implementing or planning dismantlement of nuclear warheads and their delivery vehicles
Just like their previous nuclear arms control agreements, the New START obliges Russia and the United States to dismantle or convert strategic (nuclear) delivery vehicles beyond the limits set in the Treaty, in a verifiable way. The New START does not stipulate to dismantle nuclear warheads, but the two states have partially dismantled retired nuclear warheads as unilateral measures.
Neither country has provided comprehensive information regarding the dismantlement of nuclear warheads, including the exact numbers of dismantled warheads. While the United States has publicized some information under the previous administration,176 related, updated information has not been made available by the Trump administration. In May 2017, “the Republican-controlled Congress voted…to prevent the National Nuclear Security Administration (NNSA) from implementing the former administration’s proposal to accelerate the rate of dismantlement of retired nuclear warheads. Congress approved $56 million for nuclear warhead dismantlement and disposition activities, a reduction of $13 million, or 19 percent, from the Obama administration’s proposal of $69 million in its final budget request.”177
Other NWS did not provide any new or updated information regarding the elimination of their nuclear weapons in 2017, though France and the United Kingdom do continue to dismantle their retired nuclear warheads and delivery vehicles.
B) Decommissioning/conversion of nuclear weapons-related facilities
Few remarkable activities or progress were reported in 2017 in terms of decommissioning or conversion of nuclear weapons-related facilities.178
In 1996, France became the only country to decide to completely and irreversibly dismantle its nuclear test sites. They were fully decommissioned in 1998.179
C) Measures for fissile material declared excess for military purposes, such as disposition or conversion to peaceful purposes
In October 2016, Russian President Putin ordered the Presidential Decree on suspending implementation of the Russian-U.S. Plutonium Management and Disposition Agreement (PMDA)180, which entered into force in July 2011. The United States argued in its report on implementation of arms control and nonproliferation, published in April 2017: “Although there is no indication the Russian Federation (Russia) violated its obligations under the PMDA, Russia’s October 2016 announcement of a decision to ‘suspend’ the PMDA raises concerns regarding its future adherence to obligations under this Agreement.”181 On the other hand, Russia refuted that the report’s finding “does not correspond to reality” because Russia only suspended the PMDA in response to U.S. “hostile actions toward Russia” and a “radical change of circumstances”182 since the agreement was signed in 2000.
The Trump administration, like its predecessor, has sought to end construction of the mixed-oxide (MOX) fuel fabrication Facility (MFFF) at the Savannah River Site in South Carolina,183 and to pursue the dilution and disposal approach, due to increasing cost and delaying schedule of the MFFF’s construction. However, the Congress has not approved this approach, and allocated a budget for the construction of the MFFF. It also indicates several conditions on accepting such an approach, including that: the cost of the dilute and dispose option be less than approximately half of the estimated remaining lifecycle cost of the mixedoxide fuel program; the Secretary of Energy must provide the details of any statutory or regulatory changes necessary to complete the option; and that a “sustainable future” is established for the Savannah River Site.184
In the meantime, the United States has stated on several occasions, including the NPT Review Process, that it has made significant reductions in its military stocks of fissile material. At the 2017 NPT PrepCom, the United Stated clarified:
Out of the 95.4 metric tons of plutonium in the U.S. plutonium stockpile most recently reported in 2009, the United States has declared 61.5 metric tons excess to U.S. defense needs. Out of 686 metric tons in the U.S. stockpile of highly enriched uranium most recently reported in 2004, the United States has removed 374 metric tons from weapons programs. More than 153 metric tons removed from the stockpile has been downblended for use as civil reactor fuel. Additionally, under the 1993 U.S.-Russia Highly Enriched Uranium (HEU) Purchase Agreement, 500 metric tons, the equivalent of 20,000 nuclear warheads, of Russian weapons-origin HEU was downblended to LEU and used in U.S. nuclear power plants for over twenty years.185
 See the Hiroshima Report 2017.
 Kingston Reif, “Congress Limits Warheads Dismantlement,” Arms Control Today, Vol. 47, No. 5 (June 2017), p. 31.
 On activities or progress before 2017, see the Hiroshima Report 2017.
 NPT/CONF.2015/10, March 12, 2015.
 Under the agreement, each country is to dispose no less than 34 metric tons of weapon-grade plutonium removed from their respective defense programs by irradiating it as MOX in existing light-water reactors fuel.
 U.S. Department of State, “Adherence to and Compliance with Arms Control, Nonproliferation, and Disarmament Agreements and Commitments,” April 2017, https://www.state.gov/t/avc/rls/rpt/2017/270330.htm.
 Maggie Tennis, “INF Dispute Adds to U.S.-Russia Tensions,” Arms Control Today, Vol. 47, No. 5 (June 2017), pp. 29-30.
 Kingston Reif, “Trump Budget Supports MOX Termination,” Arms Control Today, Vol. 47, No. 6 (July/August2017), p. 30.
 Frank von Hippel, “Fissile Material Issues in the U.S. National Defense Authorization Act for Fiscal Year 2018,” IPFM Blog, December 17, 2017, http://fissilematerials.org/blog/2017/12/fissile_material_issues_i.html.
 “Statement by the United States,” Cluster 1, First Session of the Preparatory Committee for the 2020 NPT Review Conference, May 4, 2017.