Fusion-fission hybrid for fissile fuel production without processing

Technical Report · Tue Dec 27 19:00:00 EST 2011

DOI:https://doi.org/10.2172/1034500· OSTI ID:1034500

Fratoni, Massimiliano ^[1]; Moir, Ralph W. ^[1]; Kramer, Kevin J. ^[1]; Latkowski, Jeffery F. ^[1]; Meier, Wayne R. ^[1]; Powers, J. J. ^[1]

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1. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Two scenarios are typically envisioned for thorium fuel cycles: “open” cycles based on irradiation of ²³²Th and fission of ²³³U in situ without reprocessing or “closed” cycles based on irradiation of ²³²Th followed by reprocessing, and recycling of ²³³U either in situ or in critical fission reactors. This study evaluates a third option based on the possibility of breeding fissile material in a fusion-fission hybrid reactor and burning the same fuel in a critical reactor without any reprocessing or reconditioning. This fuel cycle requires the hybrid and the critical reactor to use the same fuel form. TRISO particles embedded in carbon pebbles were selected as the preferred form of fuel and an inertial laser fusion system featuring a subcritical blanket was combined with critical pebble bed reactors, either gas-cooled or liquid-salt-cooled. The hybrid reactor was modeled based on the earlier, hybrid version of the LLNL Laser Inertial Fusion Energy (LIFE) system, whereas the critical reactors were modeled according to the Pebble Bed Modular Reactor (PBMR) and the Pebble Bed Advanced High Temperature Reactor (PB-AHTR) design. An extensive neutronic analysis was carried out for both the hybrid and the fission reactors in order to track the fuel composition at each stage of the fuel cycle and ultimately determine the plant support ratio, which has been defined as the ratio between the thermal power generated in fission reactors and the fusion power required to breed the fissile fuel burnt in these fission reactors. It was found that the maximum attainable plant support ratio for a thorium fuel cycle that employs neither enrichment nor reprocessing is about 2. This requires tuning the neutron energy towards high energy for breeding and towards thermal energy for burning. A high fuel loading in the pebbles allows a faster spectrum in the hybrid blanket; mixing dummy carbon pebbles with fuel pebbles enables a softer spectrum in the critical reactors. This combination consumes about 20% of the thorium initially loaded in the hybrid reactor (~200 GWd/tHM), partially during hybrid operation, but mostly during operation in the critical reactor. The plant support ratio is low compared to the one attainable using continuous fuel chemical reprocessing, which can yield a plant support ratio of about 20, but the resulting fuel cycle offers better proliferation resistance as fissile material is never separated from the other fuel components.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48; AC52-07NA27344
• OSTI ID: 1034500
• Report Number(s): LLNL--TR-522137
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
22 GENERAL STUDIES OF NUCLEAR REACTORS
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BREEDING
CARBON
DESIGN
FISSILE MATERIALS
FISSION
FUEL CYCLE
HYBRID REACTORS
IRRADIATION
LASERS
LAWRENCE LIVERMORE NATIONAL LABORATORY
NEUTRONS
PEBBLE BED REACTORS
PROCESSING
PRODUCTION
PROLIFERATION
RECYCLING
REPROCESSING
THERMONUCLEAR REACTORS
THORIUM
THORIUM 232
TUNING
URANIUM 233