A model of radiative heat-exchange, based on the Rosseland approximation, in a gas cavity was introduced into the HEFEST computational code designed for modeling the interaction of the core melt with NPP structures during a serious accident in VVER. This approach is admissible for optically dense gas and supplements the zonal heat exchange model, already existing in the code, for a cavity with a transparent gas. The conditions for using these two approaches in modeling radiative heat transfer at different stages of an accident are discussed. The numerical implementation of the diffusion model and its verification are described. The model was tested on the problem of radiative heat exchange during melt retention at the bottom of the vessel of a VVER-1000 reactor and the results are reported.

中文翻译：

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严重事故中反应堆堆芯上方气体腔内的辐射热交换

HEFEST计算代码中引入了基于Rosseland近似的气腔内辐射热交换模型，该模型设计用于对VVER发生严重事故时芯熔体与NPP结构的相互作用进行建模。这种方法适用于光密性气体，并补充了代码中已经存在的带透明气体腔的区域热交换模型。讨论了在事故的不同阶段使用这两种方法对辐射热传递进行建模的条件。描述了扩散模型的数值实现及其验证。对模型进行了测试，以研究在VVER-1000反应堆容器底部熔体保留期间的辐射热交换问题，并报告了结果。