Molten-salt reactor concepts with reduced potential for proliferation of special nuclear materials

Abstract

This study examines design alternatives for molten-salt breeder reactors (MSBRs) with breeding ratios near 1.0 to evaluate their nonproliferation characteristics. Only those systems are examined for which sufficient information exists to describe adequately the power plant system characteristics in terms of both practicality as a source of electricity and susceptibility to diversion of special nuclear material (SNM). In this precursory study evaluating performance and nondiversion features, various candidate systems have been examined with the following results: (1) molten-salt reactors could eliminate the transport requirements of SNM to or from the reactor for long periods of time and make the extraction of SNM from the reactor inventory difficult; (2) two candidate MSR configurations, the CeF 3 processing scheme and the scheme with no chemical processing, can be highly resistant to diversion but cannot be classed as diversion-proof; (3) two additional systems, less resistant than the two above, are the reductive-extraction process without Pa isolation and the salt distillation process; and, (4) the system based on the reference MSBR, requiring salt fluorination is significantly less resistant to diversion than a system without fluorination. Diversion-resistant MSBRs, if developed, might afford resistance to diversion of SNM comparable to solid-fueled reactors without fuel reprocessing and would require less uranium for deployment and operation. * Note Added in Proof: Since this report was written, a molten-salt system was identified that may be remarkably resistant to materials diversion as well as having a conversion ratio near 1.0. This system uses a denatured fuel mixture of 233 U-238 U; processing consists only of removing fission products. These results are only tentative and require more analysis before the described properties can be confirmed. * Plutonium, if any, in the fuel will exist as PuF 3 and will also be retained on the column. It may be economical to recover this when the CeF 3 is ultimately returned with the spent fuel from the reactor facility. ** UF 3 and EuF 3 will be partially removed by the column; UF 4 and EuF 2 will not. * The process would probably leave any oxide contamination in the still bottoms, but this oxide may be combined with (and render undistillable) some uranium and protactinium.

Molten-Salt Reactors for Efficient Nuclear Fuel Utilization Without Plutonium Separation

“…Because of the perceived proliferation sensitivity of the reference design MSBR, a brief study 12 was undertaken in the fall of 1976 to determine whether the basic concept could be modified to make it sufficiently proliferation resistant for wide deployment as a power producer. The requirement for a positive breeding gain was eliminated, but the highenrichment fuel composition was retained to completely avoid the need to deal with plutonium.…”

Thorium Fuel Cycle for a Molten Salt Reactor: State of Missouri Feasibility Study

“…Thus, a thorium process is less suitable for development of plutonium-based weapons. If developed, the MSBR could prove resistant to diversion of special nuclear materials in direct comparison to that of solid-fueled reactors without fuel reprocessing [34] . The MSR probably does not offer significant advantages over other reactor systems as a single, stand-alone diversion-proof reactor to warrant development for that purpose only.…”

“…However, in a broader sense in terms of diversion of plutonium from US reactors, the MSBR offers an attractive option to limit the total plutonium buildup. The end Page 24.1261.25 products of plutonium charged in a MSBR would be essentially free of 239 Pu, 240 Pu and 241 Pu with about 12% of the original mass remaining as 242 Pu or higher-mass capture products [34] .…”