The 4S (super-safe, small and simple) reactor is a sodium-cooled small fast reactor. The core reactivity is controlled by moving the reflectors installed around the core, and the reactor has a fixed absorber at the core center to accomplish a long core lifetime. To evaluate core bowing behavior and the resulting reactivity feedback in the 4S reactor, an analytical evaluation was conducted under various core power to flow ratios (P/F). The core bowing reactivity under the BOC (beginning of core life) condition becomes increasingly negative with increasing P/F up to 2.0, then becomes less negative with increasing P/F from 2.0 to 3.0, and finally becomes positive at P/F = 3.0. The bowing reactivity under the EOC (end of core life) condition becomes increasingly negative with increasing P/F up to 1.5, then becomes less negative then positive with increasing P/F from 1.5 to 3.0; the core bowing reactivity is positive when P/F ≥ 2.0. These results are mainly caused by the following two mechanisms originating from the structural characteristics of the 4S reactor: - a decrease in neutron absorption by the fixed absorber due to the radial displacement of the inner core subassemblies (under the BOC condition); - a decrease in neutron streaming caused by the small gaps between the outer core subassemblies and the reflectors due to core radial expansion (under the EOC condition).
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17th International Conference on Nuclear Engineering
July 12–16, 2009
Brussels, Belgium
Conference Sponsors:
- Nuclear Engineering Division
ISBN:
978-0-7918-4352-9
PROCEEDINGS PAPER
Analytical Evaluation of Core Bowing Reactivity in the 4S Reactor
Satoshi Nishimura,
Satoshi Nishimura
Central Research Institute of Electric Power Industry, Komae, Tokyo, Japan
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Hirokazu Ohta,
Hirokazu Ohta
Central Research Institute of Electric Power Industry, Komae, Tokyo, Japan
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Nobuyuki Ueda
Nobuyuki Ueda
Central Research Institute of Electric Power Industry, Komae, Tokyo, Japan
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Satoshi Nishimura
Central Research Institute of Electric Power Industry, Komae, Tokyo, Japan
Hirokazu Ohta
Central Research Institute of Electric Power Industry, Komae, Tokyo, Japan
Nobuyuki Ueda
Central Research Institute of Electric Power Industry, Komae, Tokyo, Japan
Paper No:
ICONE17-75223, pp. 403-411; 9 pages
Published Online:
February 25, 2010
Citation
Nishimura, S, Ohta, H, & Ueda, N. "Analytical Evaluation of Core Bowing Reactivity in the 4S Reactor." Proceedings of the 17th International Conference on Nuclear Engineering. Volume 2: Structural Integrity; Safety and Security; Advanced Applications of Nuclear Technology; Balance of Plant for Nuclear Applications. Brussels, Belgium. July 12–16, 2009. pp. 403-411. ASME. https://doi.org/10.1115/ICONE17-75223
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