The Role of Verification in Supporting Irreversible Nuclear Disarmament

Figures & data

Figure 1. Highly irreversible disarmament over time and reversible disarmament over time.

Table 1. IND scenarios related to weapons dismantlement with our estimates of confidence in verification.

Disarmament scenario	Description and examples	Confidence in verification
Unilateral nuclear weapons dismantlement with no external observers	This is the model followed by South Africa. South Africa conducted its disarmament and dismantlement of its weapons before declaring the stockpile (Von Wielligh and Von Wielligh-Steyn 2015).	All states have high confidence that South Africa did disarm (Perkovich and Acton 2009; Von Baeckmann, Dillon, and Perricos 1995).
Dismantlement with NWS verification only	The INF follows this model.	High for the other bilateral NWS party, lower for other parties.
Multi-party nuclear weapons dismantlement with NNWS observers	Since the UK-Norway initiative, NNWS-NWS collaboration has evolved and this is the current model for the IPNDV (Hinderstein 2018; IPNDV 2020).	Highest currently available for all states.

Table 2. Activities that could be conducted under IND for the endpoint of fissile material with our estimates of confidence in verification.

Fissile material activity	Description and examples	Confidence in verification
HEU downblending	Used in Megatons to Megawatts program (Laurence Livermore National Laboratory 2013) and the JCPOA.^6	Very high for parties involved. Third parties have indicated high confidence in all processes so far.
HEU transport to another state	Used in the disarmament of Libya (Davenport 2018), and Project Sapphire which HEU was removed from former Soviet states (Tirpak 1995).	Requires a credible host state.
Placing HEU under safeguards	South Africa has retained HEU under safeguards (Stott 2022; Von Wielligh and Von Wielligh-Steyn 2015).	Material is continuously monitored.
Pu burning in MOX	Mixed Oxide (MOX) reactors use plutonium oxide from spent fuel mixed with reprocessed plutonium. After being burned up, products are immobilised and put in geological disposal. MOX has been irradiated but none has been placed in a geological disposal site.	Requires MOX reactor programme in place. MOX fuel cycles have proved difficult to maintain and operate.
Direct geological disposal of Pu	Immobilisation (Nuclear Decommissioning Authority 2019) and geological disposal. This has occurred in the United States at the Waste Isolation Pilot Plant facility (Schramke, Santillan, and Peake 2020).	Material can be continuously monitored.
Pu storage overseas	The UK and France currently have Japanese civil Pu that was reprocessed there under safeguards.	Requires a credible host state.

Table 3. IND activities related to decommissioning and dismantlement with our estimates of confidence in verification.

Decommissioning and dismantlement Activity	Description and examples	Confidence in verification
IAEA decommissioning/decommissioning with third party oversight	The IAEA has a model for decommissioning civilian facilities (Hogue, Hale, and Cooley 2022).	High
Other decommissioning without third party oversight	NWS have unilaterally decommissioned older weapons-related facilities. Voluntary offer agreements with IAEA and bilateral arms control agreements have not covered some facility/building decommissioning.	This could be very challenging for older, complicated facilities with incomplete operational records.
Removal and transport of key equipment overseas	Used in the disarmament of Libya (Tobey 2017).	Requires a credible host state.
Repurposing of facility for civilian use	Used in the JCPOA as a plan for Fordow to be converted into a stable isotope production facility and science and technology centre (Albright et al. 2019).	Depends on the facility and the degree of dual use potential.
Disablement of key equipment	Used in the DPRK during the Six-party talks at the 5 MWe Magnox-type reactor and the reprocessing facility (Nikitin 2013).	Depends on the specific action taken. During the 6-party talks most disablement activities were designed to be reversible, and some such as the demolition of the cooling tower did not significantly alter operation of the 5MWe Magnox type reactor.

Table 4. IND activities related to knowledge transfer and tacit knowledge with our estimates of confidence in verification.

Disarmament Activity	Description and examples	Confidence in verification
Destruction of documents/files	South Africa destroyed many documents prior to IAEA verification	It can be difficult to verify “completeness” and that no documents are being saved, stored or have been copied.
Handover of documents/files	The “plastic bag” of weapons designs passed to the USA in the disarmament of Libya (Tobey 2017).
Long-term employment of key personnel in other industries	Post-Cold War arrangements for former Soviet Scientists	It can be difficult to verify “completeness” and that no documents are being saved, stored or have been copied.

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