Original scientific paper
NPP Krško 3 inch Cold Leg Break LOCA Calculation using RELAP5/MOD 3.3 and MELCOR 1.8.6 Codes
Vesna Benčik,
; University of Zagreb, Faculty of Electrical Engineering and Computing Unska 3, 10000 Zagrerb, Croatia
Davor Grgić,
; University of Zagreb, Faculty of Electrical Engineering and Computing Unska 3, 10000 Zagrerb, Croatia
Siniša Šadek,
; University of Zagreb, Faculty of Electrical Engineering and Computing Unska 3, 10000 Zagrerb, Croatia
Štefica Vlahović
; University of Zagreb, Faculty of Electrical Engineering and Computing Unska 3, 10000 Zagrerb, Croatia
Abstract
NPP Krško input deck developed at Faculty of Electrical Engineering and Computing (FER)
Zagreb, for severe accident code MELCOR 1.8.6 is currently being tested. MELCOR is primarily
used for the analyses of severe accidents including in-vessel and ex-vessel core melt progression as
well as containment response under severe accident conditions. Accurate modelling of the plant
thermal-hydraulic behaviour as well as engineering safety features, e.g., Emergency Core Cooling
System, Auxiliary feedwater system and various containment systems (e.g., Passive Autocatalytic
Recombiners, Fan Coolers and Containment spray) is necessary to correctly predict the plant
response and operator actions. For MELCOR input data verification, the comparison of the results
for small break (3 inch) cold leg Loss of Coolant Accident (LOCA) for NPP Krško using MELCOR
1.8.6 and RELAP5/MOD 3.3 was performed. A detailed RELAP5/MOD 3.3 model for NPP Krško
has been developed at FER and it has been extensively used for accident and transient analyses. The
RELAP5 model has been upgraded and improved along with the plant modernization in the year
2000. and after more recent plant modifications. The results of the steady state calculation (first
1000 seconds) for both MELCOR and RELAP5 were assessed against the referent plant data. In
order to test all thermal-hydraulic aspects of developed MELCOR 1.8.6 model the accident was
analysed, and comparison to the existing RELAP5 model was performed, with all engineering
safety features available. After initial fast pressure drop and accumulator injection for both codes
stable conditions were established with heat removal through the break and core inventory
maintained by safety injection. Transient was simulated for 10000 seconds and overall good
agreement between results obtained with both codes was found.
Keywords
MELCOR, RELAP5, code comparison, input data verification, small break Loss of Coolant Accident
Hrčak ID:
247095
URI
Publication date:
28.10.2019.
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