Robert Bari

Quantitative risk assessment has been used successfully to estimate safety risks, for example, at nuclear power plants. However, more research is needed before proliferation and terrorism risks can be effectively esti­mated using such a methodology. Such risk assessment methods are easier to apply to safety, for several reasons:

• The likelihood of an accident is more easily estimated than the like­lihood of a deliberate attack. A deliberate attack depends on the choices of an intelligent adversary, making likelihoods and methods of failure difficult to estimate.

• Inherent features and engineered systems with known character­istics provide safety, whereas both intrinsic (i. e., barriers intrinsic to the technologies themselves) and extrinsic (e. g., guns, guards, gates, safeguards) systems provide security. The effectiveness of some extrinsic measures, par­ticularly those that involve human action, can be difficult to estimate.

• For safety, defense in depth and safety margins are universally embraced.

Workable proliferation risk models still need significant development.

The methodology summarized here is one of several possible ap­proaches and is analogous to the approach developed for the Generation IV Forum: Proliferation Risk and Physical Protection (PR&PP).

To perform an effective risk assessment, it is important to gather a great deal of information about the research reactor facility as well as the country in which it is located. There are many countries with research reactors, each having its own national and geopolitical interests that could impact the potential for proliferation. In addition, a number of key assumptions need to be considered in the analysis. These include assumptions about potential threats, such as diversion, misuse, breakout, theft, and sabotage; extrinsic factors such as sources of fresh fuel supply, spent fuel disposition, and fuel transportation; and facility design and operational information that impact proliferation risk.[79]

The assessment itself involves building a range of scenarios by which proliferation could occur; analyzing specific scenarios to determine whether an attempted proliferation was successful and the barriers that were en­countered along the way; then using the responses to construct a risk estimate.

The key elements of an effective proliferation risk assessment include:

• Gather information on facility design.

• Define country (or countries) context.

• Establish/define international safeguards design.

• Establish/define physical protection design.

• Define adversary mission success.

• Identify facility targets (for adversary).

• Perform pathway analysis to define potential scenarios for proliferation.

• Evaluate pathways for each threat and measure.

• Assess and interpret results.

Further research will be needed before this type of analysis can be car­ried out in a dependable way for research reactors. The range of possible scenarios has not been explored in much detail. In addition, combining the information produced by each stage of the analysis described above to pro­duce an overall understanding of risk remains challenging. However, such a risk assessment process can still be worthwhile to perform. In particular, the process itself can provide useful insights, not just the final result.

Discussion

Many measures that can be taken to reduce the risk of proliferation from research reactors are already well known. Some measures mentioned by symposium attendees included avoiding the use of HEU fuel where possible in favor of LEU fuel; maintaining adequate nuclear materials protection control and accountability (MPC&A) and physical protection measures; and using appropriate insider prevention methods, as practical.

Many of the participants at the symposium observed that the principal means of reducing proliferation risk is conversion of research reactors to LEU; however, as noted previously, this may not be possible in all cases. Other participants noted that some risk also accompanies the use of LEU. Consequently, appropriate MPC&A and physical protection measures will continue to be needed, although to a lesser extent than with HEU fuel.

A symposium participant posed a question about the relative priorities between conversion to LEU and better physical protection. In particular, is it possible to compensate for HEU use through improved security? Robert Bari’s reply was that one cannot separate conversion from physical protec­tion. Clearly, maintaining HEU fuel poses a greater risk, but LEU use does not mean zero risk. Richard Meserve clarified that at a gross overview level, conversion lowers risks as well as the costs for physical protection.