The interaction between the PR&PP Working Group and the GIF System Steering Committees (SSCs) has provided insights on the type of reactor system information that is necessary and useful to collect before one begins a PR&PP evaluation. While the focus of the GIF is on six advanced reactor concepts of various designs, some alternative concepts within these designs are potentially SMRs (e. g. there are a sodium fast reactor design of low power as well as a lead fast reactor design of low power). Furthermore all GIF concepts are in the design phase, which is much the same situation as with SMRs.

It is important to include information on major reactor parameters such as power, efficiencies considered, coolant, moderator (if any), power density values, fuel materials (this could be covered under fuel cycles), inlet and outlet conditions, coolant pressure, neutron energy spectrum, etc., for all design options under consideration.

Also useful is a high-level description of the type, or types, of fuel cycles that are unique to the reactor system and its major design options. A material-flow diagram is valuable if available. Discussion should include mention of major waste streams that might contain weapons-usable material or be used to conceal diversion of weapons-usable material.

For a given SMR design, information that is particularly important to PR&PP will include potential fuel types (including high-level characteristics of fresh and spent fuel), fuel storage and transport methods, safety approach and associated vital equipment (for confinement of radioactivity and other hazards, reactivity control, decay heat removal, and exclusion of external events), and approach to physical arrangement as it affects access control and material accounting for fuel (a potential theft target) and access control to vital equipment (a potential sabotage target). Key high-level information to define or develop about the system elements is:

• What material types exist or can exist within a system element?

• What operations are envisioned to occur in a system element, and whether (and how) these

operations can be modified or misused?

• What kind of material movement is envisioned to occur normally in and out of a system

element?

• What safeguards and security are envisioned to exist in the system element?

Potential adversary targets can be identified for the defined system elements. All system elements can be considered or only those that are judged to contain attractive adversary targets. Potential adversary targets are identified by considering material factors, facility factors, and safeguards considerations. Material factors include property attributes that can be determined from process flow sheets, such as isotopic compositions, physical forms, inventories and flow rates, etc. Facility factors include basic characteristics of equipment functions and facility operations, potential for facility/ equipment misuse, facility/equipment accessibility, etc. Safeguards considerations include, for example, the ability of safeguards systems to detect illicit activities, facility accessibility to safeguards inspectors, availability of process information to safeguards inspectors, adequacy of containment and surveillance systems to detect diversion or misuse, and the degree of incorporation of safeguards into process design and operation.

A multi-laboratory team of US subject matter experts, including several members of the PR&PP Working Group, used the PR&PP evaluation methodology as the basis for a technical evaluation of the comparative proliferation potential associated with four generic reactor types in a variety of fuel-cycle implementations. These are a sodium fast reactor, a high temperature gas reactor, a heavy water reactor, and a light water reactor. The evaluation team undertook a systematic assessment, capturing critical assumptions, and identifying inherent uncertainties in the analysis. A summary of the study was presented at the Institute of Nuclear Materials Management (INMM) 51st Annual Meeting (Zentner et al., 2010).

The relevance of the insights varies based on the various stakeholders of a PR&PP evaluation: policy makers, system designers, and the safeguards and physical protection communities.

For policy makers:

• An assessment of the proliferation potential of a particular reactor design in nuclear energy system should consider the system’s overall architecture, accounting for the availability and flow of nuclear material in the front and back end of the fuel cycle.

For designers:

• Of the five PR measures, the designer will directly influence three: detection probability (DP), detection efficiency (DE) and material type (MT).

• To enhance DP and DE, designers can incorporate features in the design to facilitate easier, more efficient and effective safeguards for inspection and monitoring. For example, minimizing the number of entry and exit points for fuel transfer between system elements will enhance material containment, protection and accountancy (MCP&A), thus partially compensating for any lack of knowledge continuity by visual inspection during a fuel transfer.

• Material type for PR is related to the chosen composition of the nuclear material. The designer can optimize the design either to reduce the material’s attractiveness (e. g., increase burnup in the uranium fuel to raise the fraction of Pu-238, thereby lowering the quality of plutonium in the spent fuel), or to make post-acquisition processing of the material more complex, indirectly increasing the technical difficulty for the proliferator.

For safeguards inspectors:

• Augmenting inspections for handling and storing fresh and spent fuel would reduce proliferation potential.

• Enhanced inspection of fresh fuel would reduce the proliferation potential of covert diversion and misuse.

• Optimizing MT and material movement pathways to facilitate accountability measurements can make verification more effective and efficient.

9.2 Future trends

The PR&PP methodology provides a framework to answer a wide variety of non­proliferation and security-related questions for SMRs and to optimize these systems to enhance their ability to withstand the threats of proliferation, theft, and sabotage. The PR&PP methodology provides the tools to assess SMRs with respect to the nonproliferation and security.

PR&PP analysis is intended to be performed, at least at a qualitative level, from the earliest stages of system design, at the level where initial flow diagrams and physical arrangement drawings are developed, and simultaneously with initial hazards identification and safety analysis. The methodology facilitates the early consideration of physical security and proliferation resistance because the structure of the PR&PP methodology bears strong similarity to safety analysis.

The PR&PP methodology adopts the structure of systematically identifying the non-proliferation and security challenges a system may face, evaluating the system response to these challenges, and comparing outcomes. The outcomes are expressed in terms of measures, which reflect the primary information that a proliferant state or an adversary would consider in selecting strategies and pathways to achieve its objectives. By understanding those features of a facility or system that could provide more attractive pathways, the designer can introduce barriers that systematically make these pathways less attractive. When this reduction may not be possible, the analyst can highlight where special institutional measures may be required to provide appropriate levels of security.

Beyond requiring that a systematic process be used to identify threats, analyze the system response, and compare the resulting outcomes, the PR&PP methodology provides a high degree of flexibility to the analyst, subject to the requirement that the results of studies receive appropriate peer review. For this reason, it is anticipated that approaches to performing PR&PP evaluations will evolve over time, as the literature and examples of PR&PP evaluations expand. Different tools for identifying targets, evaluating system response and uncertainty, comparing pathway outcomes, and presenting results can be expected to increase in number, as will the range of questions that can be answered and insights gained from PR&PP studies.

9.3 Sources of further information and advice

The reader is encouraged to see the collection of journal articles on PR&PP that is contained in a special issue of the American Nuclear Society’s Nuclear Technology (Volume 179, Number 1, 2012). This journal issue contains numerous articles on methods and applications of PR&PP and related approaches. The US National Academy of Sciences has issued a review of methods for proliferation risk assessment and its applications to decision making. This report was issued in 2013 and can be obtained at http://www. nap. edu/catalog. php? record_id=18335.

The IAEA has developed manuals for use by member countries on assessment approaches for non-proliferation and security aspects of innovative reactors. It has issued a report on ‘Options to Enhance Proliferation Resistance of Innovative Small and Medium Sized Reactors’ (see IAEA, 2014). Another recently issued report by the IAEA is International Safeguards in Nuclear Facility Design and Construction, IAEA Nuclear Energy Series No. NP-T-2.8, 2013 which discusses how international safeguards concepts can be introduced during the design phase of a nuclear facility.

The IAEA has also developed guidance for proliferation resistance assessments. It can be obtained at: ‘Guidance for the Application of an Assessment Methodology for Innovative Nuclear Energy Systems: INPRO Manual — Proliferation Resistance,’ IAEA-TECDOC-1575 Rev. 1, November 2008

Finally, three major reports on the PR&PP methodology can be found at the website: https://www. gen-4.org/gif/jcms/c_9365/prppProliferation. htm. These are (1) the report on the evaluation methodology itself (Revision 6), (2) the case study for the example sodium fast reactor, which is a four module small reactor, and (3) the joint study performed by the PR&PP working group and the designers of each of the Generation IV designs, some of which are small reactors.