Can a Fissile Material Cut-Off Treaty be Effectively Verified?

Published with some editorial changes in Arms Control Today, January/February 2005, pages 25-9.


Negotiation of a fissile material cut-off treaty (FMCT) has been blocked for several years by the failure of the Conference on Disarmament (CD) to agree on its program of work. At this stage therefore we can only speculate about the likely substantive provisions of an FMCT. The negotiating mandate for the CD, drawn from a 1993 UN General Assembly Resolution[1], has the following elements:

  • the treaty is to ban “the production of fissile material for nuclear weapons and other nuclear explosive devices”;
  • the treaty is to be “non-discriminatory, multilateral and internationally and effectively verifiable”.

The US has recently concluded that effective international verification of an FMCT is not realistically achievable. The US supports the early conclusion of an FMCT to establish “cut-off” as an international norm, but is concerned that negotiation of a verification regime will seriously delay the treaty.

This raises two issues: the practicability of effective verification; and whether the detailed verification system must be specified in the principal treaty instrument.

Verification Considerations

Is there anything in the FMCT concept that makes it inherently incapable of effective verification? This depends on the objectives of the FMCT, as reflected in its substantive provisions, yet to be negotiated. We must take care that questions of verifiability are not confused with differences over objectives, or issues of treaty architecture.

For example, the generally held FMCT concept does not proscribe production of additional nuclear weapons from unsafeguarded stocks of fissile material existing prior to the FMCT’s entry-into-force (EIF). Rather, the objective is to ensure these stocks are not added to. Some may question whether the existence of large stocks of fissile material outside the FMCT reduces the treaty’s usefulness - but this is an issue relating to the appropriateness of the FMCT’s objectives, not its verifiability.

The maxim underlying nuclear “peaceful use” treaties - the principal one being the NPT - is “trust but verify”. The subject matter of the NPT is of such fundamental importance to national and international security that no state would be prepared to rely on trust alone. The existence of a credible verification mechanism - in the form of IAEA safeguards - is essential to maintaining confidence in the effectiveness of the NPT and reinforcing the commitment of treaty parties.

Most states approach the FMCT with a similar perspective - the FMCT would not be considered credible without a verification mechanism. Here, we are not starting with a clean slate - there is already a highly developed verification regime for nuclear material and activities. We have over 40 years experience with IAEA safeguards. In addition, there is considerable experience with bilateral verification and confidence-building mechanisms (CBMs), some directly applicable to nuclear weapons and sensitive materials.

Treaty Architecture

In the area of multilateral verification treaties, there are two alternative precedents. One is for a single treaty containing both the basic treaty objectives and commitments and the details of the verification system – the approach taken with the Chemical Weapons Convention (CWC). The disadvantages of this approach include the time required to negotiate the treaty – a US concern in the case of the FMCT – and the degree of inflexibility in the verification system. Updating the verification system would be a major political exercise.

The alternative approach – demonstrated very successfully by the NPT – is to have the basic political commitments in a principal treaty, and to set out the verification system in a secondary agreement (or series of agreements – in the NPT’s case each party concludes a safeguards agreement with the IAEA based on the model in IAEA document INFCIRC/153). This approach separates largely political from largely technical subject matters, and allows for an adaptable verification system.

The NPT was concluded in 1968 and entered into force in 1970. The model safeguards agreement, INFCIRC/153, was not concluded until 1972. The negotiation of the model Additional Protocol (INFCIRC/540), agreed in 1997, illustrates how this basic approach allows flexibility for major updates of the verification system. Another advantage of having separate negotiations on the technical details is that such negotiations can proceed quite expeditiously – despite their complexity, INFCIRC/153 and INFCIRC/540 each took only about 18 months to conclude.

Given the commonalities in subject matter between IAEA safeguards and FMCT verification, it would seem sensible to follow the NPT route, thus enabling the political commitment – the international norm – to be established quickly, and the details of the verification system to follow.

Objectives and Scope of FMCT

The basic objective of FMCT will be to proscribe production of fissile material for nuclear weapons or other nuclear explosive devices. Accordingly, upon EIF each party would undertake:

  • not to produce fissile material for nuclear weapons;
  • to accept international verification on relevant facilities and nuclear material to verify this commitment;
  • not to use any fissile material subject to verification under FMCT for nuclear weapons - i.e. the principle of irreversibility would apply, “subject material” could not be withdrawn for weapons use.

For the purposes of the FMCT, it is expected that “fissile material” would encompass separated (unirradiated) plutonium, uranium-233, and highly enriched uranium (HEU). It would probably also need to include separated neptunium, which is recognised by the IAEA as a material of potential proliferation significance.

Non-proscribed activities Production of fissile material for civil purposes, and for non-explosive military purposes such as naval propulsion, would be permitted, but only under verification to ensure fissile material is not diverted to weapons. Recycle (or clean-up) of plutonium from weapons - an established stockpile stewardship practice – which does not involve new production of fissile material, would also be permitted.

States affected The FMCT would apply to three groups of states:

  • non-nuclear weapon states (NNWS) party to the NPT;
  • the five NPT nuclear weapon states (NWS);
  • the three “nuclear capable” states outside the NPT - India, Israel and Pakistan[2].

NNWS party to the NPT are already committed not to produce or use nuclear material for weapons purposes, and to accept IAEA safeguards on all their nuclear material and activities to verify this commitment (comprehensive safeguards[3]). In principle therefore the FMCT should not involve any additional commitments from NNWS that are implementing both an NPT safeguards agreement and an Additional Protocol. The principal effect of the FMCT - and its verification task - relate mainly to the NWS and the non-NPT states.

Scope of the FMCT A major issue to be resolved in the negotiations is the scope of the FMCT - the facilities and material to which verification would apply. In broad terms the basic options are:

  • a treaty of wide scope, covering all nuclear facilities and nuclear material - other than non-proscribed military activities, i.e. naval propulsion, and subject to the issue of stocks (discussed below); or
  • a treaty of focused scope, concentrating on the most proliferation-sensitive fissile material production facilities - i.e. reprocessing and enrichment facilities - and relevant production from those facilities.

There would be substantial problems in trying to extend the comprehensive safeguards system to the NWS and non-NPT states:

  • truly comprehensive safeguards covering all nuclear material cannot apply in the NWS and non-NPT states while they have nuclear weapons and therefore will retain, outside verification, nuclear material existing at the FMCT’s EIF;
  • the cost of verification on the comprehensive model in the NWS would be very high.

Taking these and related considerations into account, Australia has concluded that a separate, distinct FMCT verification regime would be required for the NWS and non-NPT states. The FMCT commitment to be verified would be the same as that verified by IAEA safeguards in the NNWS - i.e. that fissile material is not being produced for nuclear weapons purposes – but the verification approach would be more appropriate to the circumstances of the NWS and non-NPT states.

Australia has proposed a focused approach, involving:

  • the monitoring of facilities that can produce fissile material (production facilities) – i.e. enrichment and reprocessing plants;
  • verification of fissile material subject to the FMCT (subject material) - separated plutonium, U-233, HEU and separated neptunium produced after EIF. This would require verification measures at downstream facilities handling these materials.

In addition, the FMCT verification regime will need to include measures aimed at detection of possible undeclared production facilities - see below.


A major issue - fundamental both to the substance of the FMCT and to the prospects of successful negotiation - is how to treat past production of fissile material, i.e. stocks existing at EIF.

The issue of stocks does not arise in the case of states which have accepted comprehensive safeguards under the NPT. All holdings of nuclear material in these states are subject to IAEA safeguards. The issue relates to those states which are outside comprehensive safeguards and have the capability to produce fissile material, i.e. the NWS and the non-NPT states.

The term “stocks” can have a wide meaning, ranging from fissile material in weapons, to bulk material declared surplus to defence needs, and to civil stocks of fissile material. Essentially, the FMCT could not apply to all pre-existing stocks held by the NWS and the three non-NPT states, as this would amount to instant disarmament – clearly an unrealistic objective. The FMCT will cap future production, but it must be recognised that past production in the NWS and non-NPT states would be outside verification.

If the parties so wished, however, the FMCT could contain a mechanism by which parties could place surplus and civil stocks under the treaty in accordance with the principle of irreversibility. Some parties may wish to do this as a mutual CBM.

Verification Methods

It is envisaged that verification under the FMCT would comprise three basic elements: routine verification activities for declared facilities and material; verification activities aimed at detection of possible undeclared fissile material production; and complementary measures aimed at transparency and confidence-building.

Declared activities In concept this aspect would be very similar to IAEA safeguards. FMCT parties would be required to declare all relevant facilities – enrichment and reprocessing facilities, and downstream facilities handling subject material.

Declared facilities would be monitored – through inspections, containment and surveillance, and other measures – to verify there is no undeclared production of fissile material, and that declared fissile material is not diverted to nuclear weapons (or purposes unknown).

For enrichment plants, verification would be applied to all facilities, including those producing low enriched uranium (LEU), to ensure there is no undeclared production of HEU. In principle verification would not be applied to LEU – but in view of the advantages of LEU as a feedstock for undeclared HEU production, some verification measures for LEU may need to be considered, particularly in the case of states with smaller arsenals.

For reprocessing plants, verification would be applied to verify throughput. Verification would be applied to separated plutonium, and to facilities in which separated plutonium is present, sufficient to ensure the plutonium remains under treaty commitments. Verification would cease to apply once plutonium has been returned to a reactor as fuel and irradiated, since irradiated plutonium is of no further strategic value until it has been reprocessed.

Undeclared activities Here, two broad forms of verification activity are envisaged: routine activities aimed at evaluating the completeness and correctness of FMCT declarations; and inspections based on suspicion of a breach of FMCT commitments.

A major challenge for IAEA safeguards is the detection of undeclared nuclear facilities, particularly - because of the limited observable indicators - centrifuge enrichment facilities. In the past, for IAEA safeguards, techniques for the detection of undeclared facilities were limited, and detection of undeclared nuclear material was seen as the major indicator of the existence of undeclared facilities. Now, the increasing availability and capability of techniques for detection of undeclared facilities has led to a revolutionary change in safeguards. In the ongoing program to strengthen IAEA safeguards, emphasis is being given to detection of undeclared facilities.

A whole suite of new measures is being established, including: more effective information collection and analysis (including sharing of intelligence information); satellite imagery; and - through the Additional Protocol - wide-ranging complementary access to apply verification measures such as environmental sampling. Another technique under study is wide-area environmental monitoring – there is practical experience with this technique from UNSCOM/UNMOVIC activities in Iraq. It can be expected that methods similar to these would apply under the FMCT.

An issue raised for the FMCT is, how to recognise non-compliance. Since the NWS and non-NPT states have “undeclared material” - fissile material pre-existing EIF – how can it be determined whether particular material is the result of undeclared production post-EIF? There are techniques to resolve this question – nuclear material can be dated – but, as is increasingly the case with IAEA safeguards, the principal focus of FMCT verification to counter undeclared activities will be the detection of undeclared enrichment and reprocessing facilities.

As with IAEA safeguards, detection of undeclared enrichment and reprocessing facilities will also be a challenge for FMCT verification – but in some respects the problem is more manageable for the FMCT, because of extensive intelligence information held by the relevant states on each other, and the limited motivation to cheat for states that have nuclear arsenals they consider adequate – and in some cases are actively reducing. The more difficult cases might be states with small arsenals - India and Pakistan - where bilateral CBMs could have an important role in complementing international verification.

Similar to the Additional Protocol, under FMCT the verification agency would have the right to request access to locations to resolve questions and inconsistencies arising from information analysis. In addition to access initiated by the verification agency, FMCT parties may require a verification mechanism they can initiate directly, along the lines of the CWC’s challenge inspection mechanism.

National security aspects The NWS and non-NPT states are concerned to protect national security and proliferation-sensitive information relating to past nuclear weapons programs and ongoing stockpile stewardship activities. Hence, verification methods and procedures will need to be carefully defined. Managed access provisions will be essential, probably elaborated in greater detail under the FMCT than in the Additional Protocol.

Other verification methods, and transparency/confidence building measures In addition to measures drawn from IAEA safeguards experience, other approaches that could be relevant to FMCT include “open skies” (flight corridors available for verification purposes), and bilateral or regional access arrangements. Such measures could have an important confidence-building role, complementing international verification, e.g. between India and Pakistan, or in the Middle East.

Verification of HEU produced for naval propulsion This is often raised as a problem for the FMCT, because the design of naval fuel is highly classified. Appropriate verification is required to ensure this does not become a route for diversion. This is complex but not insurmountable – the Trilateral Initiative between the US, Russia and the IAEA demonstrates the practicability of innovative approaches to verifying fissile material of sensitive composition, shape and mass.

Verification Intensity

Although some of the methods of IAEA safeguards are readily applicable to FMCT verification, the treaty objectives are very different. This would be reflected in the design of the FMCT verification regime.

Comprehensive safeguards are designed to provide assurance against horizontal proliferation, i.e. the acquisition of one or more nuclear weapons by a NNWS. The acquisition of just one or two nuclear weapons would be a dramatic change in the strategic status of such a state. The sensitivity of IAEA safeguards, reflected in technical parameters such as goal quantities (e.g. the significant quantity of 8 kg plutonium), detection probability, timeliness goals, and inspection frequency, has been set accordingly.

On the other hand, with states outside comprehensive safeguards, the concern is essentially vertical proliferation, i.e. additions to existing arsenals. The FMCT would address this by providing assurance that stocks of fissile material held outside international verification will not increase. For states that already hold nuclear weapons, their concern will be with treaty violations that could substantially alter strategic relativities: for states with thousands of weapons, a strategically significant violation might involve hundreds of weapons. Thus the design of verification approaches to deter vertical proliferation could be qualitatively different to those directed at horizontal proliferation.

A major development in IAEA safeguards implementation is a move away from uniformity to safeguards based on a “state-level approach”, taking into account appropriate state-specific considerations. This development remains a work in progress[4] – but the concept is readily applicable in the FMCT context. Applying a risk-informed approach, decisions on verification intensity could take account of considerations such as the following.

Since the NWS will retain military stocks outside the FMCT, it is reasonable to assume they have concluded, before joining the treaty, that those stocks are sufficient for their foreseeable needs. Hence they should have little incentive to cheat. This is especially the case for the US and Russia, which are dramatically reducing nuclear weapon numbers and are committed to irreversibly transferring substantial quantities of fissile material out of weapons programs. In these circumstances rigorous verification is not required. On the other hand, for states with small arsenals, verification intensity will need to reflect the fact that small-scale violations could have a serious effect on strategic relativities.


The US, Russia, France and UK have announced cessation of fissile material production for nuclear weapons, and it is understood China has also ceased such production. The FMCT would make an important contribution to nuclear non-proliferation, by formalising this situation and making it irreversible. A further important contribution would be capping the fissile material available in the non-NPT states, which are otherwise under no restraint. The FMCT would also help establish conditions under which further nuclear disarmament, involving all relevant states, would be possible – a significant consideration in the context of the NPT review process.

To achieve these benefits will require the treaty to be effective, and this requires a credible verification regime. There is a substantial foundation to build on, drawing on experience from IAEA safeguards and bilateral verification arrangements.

Undue delay in concluding a normative treaty can be avoided by separating negotiation of the principal treaty from negotiation of the verification system. The latter would be a largely technical negotiation, which can commence in parallel with the principal negotiation but be concluded subsequently.

Whether a particular verification regime provides the degree of assurance required by the parties - hence is considered “effective” - is a matter for judgment, based on many factors: the verification objectives; the verification methods and standards; related CBMs; other information (including intelligence) available to the parties; incentives/deterrents reinforcing compliance; and so on. Only when we have defined the objectives and main features of FMCT verification will it be possible to design the verification system and to judge whether it will be sufficiently effective – but there seems no in-principle reason why this should not be the case.

John Carlson is Director General, Australian Safeguards and Non-Proliferation Office. He is also Chairman of SAGSI, the IAEA’s Standing Advisory Group on Safeguards Implementation. This paper reflects the personal views of the author and does not necessarily represent the views of the Australian Government, nor of SAGSI.


[1] UNGA Resolution A/RES/48/75/L of 16 December 1993.

[2]. In 2003 the DPRK announced its withdrawal from the NPT. However the validity of this has not been determined, and for the purposes of this discussion it is assumed the DPRK is still bound by the NPT.

[3]. NPT safeguards used to be termed full scope safeguards, but the usual term now is comprehensive safeguards.

[4]. For a discussion of some ideas in this area see Assessing Motivation as a Means of Determining the Risk of Proliferation, Annette Berriman, Russell Leslie and John Carlson, 2004 Annual Meeting of the Institute of Nuclear Materials Management.

Last Updated: 24 September 2014