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Numerical Investigation of Dryout Heat Flux and Heat Transfer Characteristics in Core Debris Bed of SFR After Severe Accident

Bin Zhang, Mengwei Zhang, Cheng Peng, Jianqiang Shan, Baowen Yang, Yonggang Cao, Lixia Ren

Nuclear Science and Engineering / Volume 193 / Number 1-2 / January-February 2019 / Pages 115-130

Technical Paper - Selected papers from NURETH 2017 /

Received:April 27, 2018
Accepted:August 17, 2018
Published:December 21, 2018

Nuclear reactor severe accidents can lead to the release of a large amount of radioactive material and cause immense disaster to the environment. Based on a heat conduction model, the DEBRIS-HT program for analyzing the heat transfer characteristics of a debris bed after a severe accident of a sodium-cooled fast reactor was developed. The basic methodology of the DEBRIS-HT program is to simplify the complex energy transfer process in the debris bed to a simple heat transfer problem by solving the equivalent thermal conductivity in different situations. In this paper, the models of the DEBRIS-HT code are explained in detail. The comparison between the simulation and experimental results shows that the DEBRIS-HT program can correctly estimate the heat transfer process in the debris bed. In addition, the DEBRIS-HT code is applied to model the core catcher of the China fast reactor. The calculated dryout heat flux of the postulated accident, in which 100% of core melts and drops on the core catcher, agrees well with the prediction result of the Lipinski’s zero-dimensional model. And the error between them is about 10%. The calculated dependence of dryout heat flux on particle size is also in good consistence with the prediction by Lipinski’s zero-dimensional model. Then, the temperature distribution and the temperature excursion of the debris bed during a likely accident are analyzed, which provides significant reference to the severe accident analysis.

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