American Nuclear Society

Home / Store / Journals / Electronic Articles / Nuclear Technology / Volume 138 / Number 1

Analysis of External Cooling of the Reactor Vessel During Severe Accidents

Jin Ho Song, Sang Baik Kim, Hee Dong Kim

Nuclear Technology

Volume 138 / Number 1 / April 2002 / Pages 79-89


Member Price:$27.00
Member Savings:$3.00

An analysis is presented of the integral behavior of the external cooling of a reactor vessel by natural circulation during a severe accident to investigate the feasibility of the in-vessel retention strategy for a high-power reactor by using the RELAP5/MOD3 computer code. It is shown that two-phase flow instability phenomena, including natural-circulation oscillation and density wave oscillations, affect the local thermal margin at the reactor vessel wall. The heat load on the reactor vessel is simplified as a uniform heat flux load of 600 kW/m2 in the base case. A sensitivity study for the effect of the inlet K factor, nonuniform heat flux distribution, inlet flow area, and subcooling of the pool water is performed to evaluate the local thermal margin. The results of the analysis show that natural-circulation cooling is marginal at this level of heat flux. It also clearly indicates that a system level of analysis for two-phase natural circulation, including the sensitivity study on the design parameters, is necessary to ensure successful implementation of the external cooling.

Questions or comments about the site? Contact the ANS Webmaster.