Numerical model of characteristics of a particulate debris bed coolability with single phase flow

Abstract

Designed on the basis of defense-in-depth concept, liquid metal cooled fast reactor, such as KALIMER-600 (Korea Advanced Liquid Metal Reactor) is unlikely to undergo the HCDA (hypothetical core disruptive accident). Because of its inherent safety features, most of the incidents of abnormal operation end with reactor trip and no further progression. Under a postulated, very low probable core meltdown scenario without reactor trip, however, there exists a possibility of re-criticality and vessel melting and the status of debris generated plays an important role. For this reason, the analysis on the ability of post-accident heat removal (PAHR) should be preceded. As a part of this, single phase flow coolability analysis of the particulate debris bed formed at the top of core catcher has been performed to achieve in-vessel fuel retention. The analysis is based on the Ergun equation and Macdonald’s work that describe the phenomena of flow through a porous media with Hardee and Nilson’s study of temperature relationship of the debris beds. The forming process of particulate debris bed is described and single phase cooling model with numerical results are presented. The analysis was conducted in the condition of three cases, inner and inner+middle and whole core meltdown case. It was proved that the inner and inner+middle core meltdown case could be cooled down with single phase flow. The whole core meltdown case will need some other management. Also, parameter sensitivity test was done.