Nuclear Energy for New Europe 2009

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No: 409

Conference: Nuclear Energy for New Europe 2009

Title: ASTEC and ICARE/CATHARE Application to Simulation of a VVER-1000 Large Break LOCA

Theme: Severe Accidents

Author(s): Yury Zvonarev, Vadim Kobzar, Misha Budaev, Patrick Chatelard, Jean-Pierre Van Dorsselaere

Contact : Yury Zvonarev

E-mail: Zvonarev@nsi.kiae.ru

Address: Russian Research Center “Kurchatov Institute”
123182 Moscow

Country: Russia

ASTEC and ICARE/CATHARE are computer codes allowing analysing severe accidents in LWRs. The ASTEC integral code, commonly developed by IRSN (France) and GRS (Germany), is intended for prediction of a whole severe accident sequence from the initiating event up to fission product release out of the containment. The ICARE/CATHARE code, developed by IRSN, is based on a coupling between the IRSN core degradation code ICARE2 and the best-estimate French thermalhydraulics code CATHARE2 (co-developed by CEA, AREVA-NP, EdF and IRSN). The ICARE/CATHARE V2 code aims to analyse a severe accident since the beginning of the accident up to a possible corium transfer into the lower head and to reactor vessel failure. The code applicability to VVER is a clear common IRSN-GRS objective. The current work in collaboration between IRSN and RRC KI (Russia) aims at reaching this objective.
Several actions supporting codes application to VVER have been initiated: Development and optimization of nodalization schemes for VVER reactors, safety systems and containment; Expansion and development of the code material database specific to VVER; Development and implementation into codes of the models specific to VVER safety systems; Validation of codes on experiments specific to VVER conditions.
This paper is devoted to ASTEC and ICARE/CATHARE applications to simulation of a severe accident scenario on a VVER-1000. A Large Break LOCA (850 mm) sequence accompanied with the station blackout was selected for analysis.
ICARE/CATHARE V2.2 successfully predicted main events of the accident: heat up of the core, core degradation, and melt relocation to the lower part of the core. A simulation of a whole accidental sequence was performed with ASTEC V1.3-rev3 code: core heat up, core elements melting, melt relocation, reactor vessel rupture, molten corium/concrete interaction, release and distribution of steam, H2, CO, CO2, fission products and aerosols in the containment. It must be pointed out that, as concerns the thermalhydraulics front-end phase and the in-vessel degradation phase, the ASTEC simulation exhibited consistent results with respect to the best-estimate ICARE/CATHARE ones.
The next stages of the collaboration will consist in formulating the modelling specifications of VVER safety systems, and in parallel to work on validation and reactor applications of the next versions of ASTEC and ICARE/CATHARE codes.

No:	409
Conference:	Nuclear Energy for New Europe 2009
Title:	ASTEC and ICARE/CATHARE Application to Simulation of a VVER-1000 Large Break LOCA
Theme:	Severe Accidents
Author(s):	Yury Zvonarev, Vadim Kobzar, Misha Budaev, Patrick Chatelard, Jean-Pierre Van Dorsselaere
Contact :	Yury Zvonarev
E-mail:	Zvonarev@nsi.kiae.ru
Address:	Russian Research Center “Kurchatov Institute” 123182 Moscow
Country:	Russia

ASTEC and ICARE/CATHARE are computer codes allowing analysing severe accidents in LWRs. The ASTEC integral code, commonly developed by IRSN (France) and GRS (Germany), is intended for prediction of a whole severe accident sequence from the initiating event up to fission product release out of the containment. The ICARE/CATHARE code, developed by IRSN, is based on a coupling between the IRSN core degradation code ICARE2 and the best-estimate French thermalhydraulics code CATHARE2 (co-developed by CEA, AREVA-NP, EdF and IRSN). The ICARE/CATHARE V2 code aims to analyse a severe accident since the beginning of the accident up to a possible corium transfer into the lower head and to reactor vessel failure. The code applicability to VVER is a clear common IRSN-GRS objective. The current work in collaboration between IRSN and RRC KI (Russia) aims at reaching this objective. Several actions supporting codes application to VVER have been initiated: Development and optimization of nodalization schemes for VVER reactors, safety systems and containment; Expansion and development of the code material database specific to VVER; Development and implementation into codes of the models specific to VVER safety systems; Validation of codes on experiments specific to VVER conditions. This paper is devoted to ASTEC and ICARE/CATHARE applications to simulation of a severe accident scenario on a VVER-1000. A Large Break LOCA (850 mm) sequence accompanied with the station blackout was selected for analysis. ICARE/CATHARE V2.2 successfully predicted main events of the accident: heat up of the core, core degradation, and melt relocation to the lower part of the core. A simulation of a whole accidental sequence was performed with ASTEC V1.3-rev3 code: core heat up, core elements melting, melt relocation, reactor vessel rupture, molten corium/concrete interaction, release and distribution of steam, H2, CO, CO2, fission products and aerosols in the containment. It must be pointed out that, as concerns the thermalhydraulics front-end phase and the in-vessel degradation phase, the ASTEC simulation exhibited consistent results with respect to the best-estimate ICARE/CATHARE ones. The next stages of the collaboration will consist in formulating the modelling specifications of VVER safety systems, and in parallel to work on validation and reactor applications of the next versions of ASTEC and ICARE/CATHARE codes.