Design Study to Increase Plutonium Conversion Ratio of HC-FLWR Core

• Published in: Nuclear Technology Vol. 179; no. 3; pp. 309 - 322
• Main Authors: Yamaji, Akifumi, Nakano, Yoshihiro, Uchikawa, Sadao, Okubo, Tsutomu
• Format: Journal Article
• Language: English
• Published: La Grange Park, IL Taylor & Francis 01.09.2012; Informa UK Limited; American Nuclear Society
• Subjects: Applied sciences; Conversion ratio; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Light water reactors; Nuclear engineering; Nuclear fuels; Nuclear power generation; Nuclear reactor components; Nuclear reactors; Plutonium; Preparation and processing of nuclear fuels; Uranium; Enrichment; Breeder; HC-FLWR; Fuel cycle; Nuclear fuel; Burnup; FLWR/MIX fuel assembly; Standards; Light water reactor; Nuclear reactor; Boiling water reactor; Reactivity; Mixed fuel; Fuel rod; Plutonium; Uranium dioxide; Uranium oxide; Performance; Uranium 235; BWR; Reactor core
• ISSN: 0029-5450; 1943-7471
• DOI: 10.13182/NT12-A14165

The innovative water reactor for flexible fuel cycle (FLWR) is an advanced reactor concept based on the well-developed light water reactor (LWR) technology. It is to be introduced in two stages to achieve effective and flexible utilization of the uranium and plutonium resources. In the first stage, the high-conversion-type reactor concept (HC-FLWR) is to be introduced, with a core that achieves a fissile Pu conversion ratio of 0.84. Then, in the second stage, the reduced-moderation water reactor (RMWR) concept can be introduced, with a breeder-type core that achieves a fissile Pu conversion ratio of 1.05. From the viewpoint of effective introduction of the high-conversion-type reactor, such as the introduction capacity of the reactor, HC-FLWR is required to further raise the fissile Pu conversion ratio to [approximately]0.95. This study aims to develop a new core design concept for the high-conversion-type core, HC-FLWR + , to achieve the higher fissile Pu conversion ratio of [approximately]0.95 under the framework of UO 2 and U-Pu mixed-oxide (MOX) fuel technologies for LWRs. For raising the fissile Pu conversion ratio and controlling the void reactivity characteristics of the core, the concept of FLWR/MIX fuel assembly, which uses MOX and enriched UO 2 fuel rods, is utilized. The relationships between the main design parameters and the core performance index parameters are clarified in this study. When the fuel rod diameter and the clearance range from 1.23 to 1.28 cm and 0.25 to 0.20 cm, respectively, under the same pitch of 1.48 cm, the fissile Pu conversion ratio and the core average discharge burnup range from 0.89 to 0.94 and 53 to 49 GWd/tonne, respectively (the fissile Pu conversion ratio and the burnup are subject to a trade-off). Furthermore, when 235 U enrichment in the UO 2 fuel rods is increased from 4.9 to 6 wt%, the fissile Pu conversion ratio improves to 0.97. From these relationships, two representative core designs with fissile Pu conversion ratios of 0.91 and 0.94 and one optional design with a ratio of 0.97 were obtained. Hence, the flexibility of HC-FLWR + concept to achieve a higher fissile Pu conversion ratio of [approximately]0.95 has been revealed. Together with the standard HC-FLWR design, the concept covers a wide range of needs on fissile Pu conversion ratio from 0.84 up to 0.97, with design variations that are expected to be within the scope of current boiling water reactor and MOX fuel technologies.