Nuclear Engineering and Technology

  • 제56권3호
  • /
  • Pages.873-879
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  • 2024
  • /
  • 1738-5733(pISSN)
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  • 2234-358X(eISSN)
한국원자력학회 (Korean Nuclear Society)
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SIMMER-IV application to safety assessment of severe accident in a small SFR

  • H. Tagami (Japan Atomic Energy Agency) ;
  • Y. Tobita (Japan Atomic Energy Agency)
  • 투고 : 2023.05.24
  • 심사 : 2023.10.16
  • 발행 : 2024.03.25
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초록

A sodium-cooled fast reactor (SFR) core has a potential of prompt criticality due to a change of core material distribution during a severe accident, and the resultant energy release has been one of the safety issues of SFRs. In this study, the safety assessment of an unprotected loss-of-flow (ULOF) in a small SFR (SSFR) has been performed using the SIMMER-IV computer code, which couples the models of space- and time-dependent neutronics and multi-component, multi-field thermal hydraulics in three dimensions. The code, therefore, is applicable to the simulations of transient behaviors of extended disrupted core material motion and its reactivity effects during the transition phase (TP) of ULOF, including a potential of prompt-criticality power excursions driven by fuel compaction. Several conservative assumptions are used in the TP analysis by SIMMER-IV. It was found out that one of the important mechanisms that drives the reactivity-inserting fuel motion was sodium vapor pressure resulted from a fuel-coolant interaction (FCI), which itself was non-energetic local phenomenon. The uncertainties relating to FCI is also evaluated in much conservative way in the sensitivity analysis. From this study, the ULOF characteristics in an SSFR have been understood. Occurrence of recriticality events under conservative assumptions are plausible, but their energy releases are limited.

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과제정보

The authors express their sincere gratitude to Mr. Masaaki Sugaya and Mr. Masahiro Mizuno of NESI Inc. for their unvaluable programming and computational assistance.

참고문헌

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