Abstract As a key severe accident management strategy for light water reactors (LWRs), in-vessel retention (IVR) through external reactor vessel cooling (ERVC) has been the focus of relevant studies for decades. However, previous studies only investigated the molten pool configurations considered to be in a final steady state mainly for reactors of such as AP600 and AP1000. Furthermore, most of studies performed in the past dealt with analysis for an isolated IVR-ERVC process, without considering the strong coupling between the internal and external reactor pressure vessel (RPV) conditions. This paper addresses the IVR-ERVC issues from a transient perspective using the severe accident code MELCOR for a large advanced passive power plant: a three-loop, 5000 MWt scale pressurized water reactor with passive safety features. The analysis is mainly focused on the severe accident transients including core degradation and relocation, molten pool formation and growth, and heat transfer within a molten pool. Furthermore, internal and external RPV conditions are combined together in the IVR-ERVC analysis. MELCOR calculations for lower head heat flux are then compared with critical heat flux (CHF) to assess the effectiveness of IVR-ERVC. The results suggest that lower head heat flux is below the CHF value. Therefore, the IVR-ERVC strategy for this large PWR is considered to be feasible. It was also found that as the reactor power is raised to large scale PWR, new accident sequences may occur during the severe accident evolution, thus leading to a proposal of a completely new molten pool configuration for future studies.
[1]
K. G. Condie,et al.
Late-phase melt conditions affecting the potential for in-vessel retention in high power reactors
,
2004
.
[2]
G. L. Thinnes,et al.
Potential for AP600 in-vessel retention through ex-vessel flooding
,
1997
.
[3]
C. M. Allison,et al.
Design report on SCDAP/RELAP5 model improvements - debris bed and molten pool behavior
,
1994
.
[4]
D. Dropkin,et al.
Natural-Convection Heat Transfer in Liquids Confined by Two Horizontal Plates and Heated From Below
,
1959
.
[5]
T. G. Theofanous,et al.
The first results from the ACOPO experiment
,
1997
.
[6]
G. H. Su,et al.
Analysis of safety margin of in-vessel retention for AP1000
,
2010
.
[7]
M. Khatib-Rahbar,et al.
Analysis of likelihood of lower head failure and ex-vessel fuel coolant interaction energetics for AP1000
,
2005
.
[8]
Hans K. Fauske,et al.
External cooling of a reactor vessel under severe accident conditions
,
1993
.
[9]
O. Kymäläinen,et al.
In-vessel coolability and retention of a core melt
,
1997
.
[10]
T. G. Theofanous,et al.
Natural convection for in-vessel retention at prototypic Rayleigh numbers
,
2000
.
[11]
T. G. Theofanous,et al.
In-Vessel Retention Technology Development and Use for Advanced PWR Designs in the USA and Korea
,
2004
.