Start-up fuel and power flattening of sodium-cooled candle core

Conference · Mon Jul 01 04:00:00 EDT 2013

OSTI ID:22264112

Takaki, Naoyuki; Sagawa, Yu; Umino, Akitake ^[1]; Sekimoto, Hiroshi ^[2]

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1. Department of Nuclear Safety Engineering, Tokyo City University 1-28-1 Tamazutsumi, Setagaya, Tokyo 158-8557 (Japan)
2. University of California, Berkeley, CA 94720 (United States)

The hard neutron spectrum and unique power shape of CANDLE enable its distinctive performances such as achieving high burnup more than 30% and exempting necessity of both enrichment and reprocessing. On the other hand, they also cause several challenging problems. One is how the initial fuel can be prepared to start up the first CANDLE reactor because the equilibrium fuel composition that enables stable CANDLE burning is complex both in axial and radial directions. Another prominent problem is high radial power peaking factor that worsens averaged burnup, namely resource utilization factor in once-through mode and shorten the life time of structure materials. The purposes of this study are to solve these two problems. Several ideas for core configurations and startup fuel using single enrichment uranium and iron as a substitute of fission products are studied. As a result, it is found that low enriched uranium is applicable to ignite the core but all concepts examined here exceeded heat limits. Adjustment in enrichment and height of active and burnt zone is opened for future work. Sodium duct assemblies and thorium fuel assemblies loaded in the center region are studied as measures to reduce radial power peaking factor. Replacing 37 fuels by thorium fuel assemblies in the zeroth to third row provides well-balanced performance with flattened radial power distribution. The CANDLE core loaded with natural uranium in the outer and thorium in the center region achieved 35.6% of averaged burnup and 7.0 years of cladding life time owing to mitigated local fast neutron irradiation at the center. Using thorium with natural or depleted uranium in CANDLE reactor is also beneficial to diversifying fission resource and extending available term of fission energy without expansion of needs for enrichment and reprocessing.

• Research Organization: American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
• OSTI ID: 22264112
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
22 GENERAL STUDIES OF NUCLEAR REACTORS
BURNUP
CLADDING
DEPLETED URANIUM
ENRICHED URANIUM
ENRICHMENT
FAST NEUTRONS
FISSION
FISSION PRODUCTS
FUEL ASSEMBLIES
FUEL CANS
IRON
ISOTOPE SEPARATION
NATURAL URANIUM
NEUTRON SPECTRA
NUCLEAR FUELS
POWER DISTRIBUTION
REPROCESSING
SODIUM
START-UP
THORIUM