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Thermal-hydraulic performance of primary system of RBMK in case of accidents

2007; Elsevier BV; Volume: 238; Issue: 4 Linguagem: Inglês

10.1016/j.nucengdes.2007.03.005

1872-759X

F. D’Auria, B. A. Gabaraev, V. Radkevitch, A. Moskalev, Eugenijus Ušpuras, Аlgirdas Кaliatka, Carlo Parisi, M. Cherubini, F. Pierro,

Graphite, nuclear technology, radiation studies

Within the framework of an European Commission sponsored activity, an overall assessment of the deterministic safety technology of the ‘post-Chernobyl modernized’ RBMK has been completed. The accident analysis, limited to the area of design basis accident, constituted the key subject for the study; therefore, the notorious Chernobyl unit 4 event was outside the scope of the investigation. The present paper deals with the evaluation of the accident performance of the primary system of the RBMK. Ignalina-2 and Smolensk-3 nuclear power plants (NPP) are considered. The documented activity includes four main parts: (a) description of key features of the primary system for the two NPP; (b) identification and characterization of relevant accident scenarios part of the (DBA) area; (c) key features and qualification level of adopted computation tools primarily including codes and input decks; (d) results from the analysis of selected accident scenarios. In the first part of the paper the layout complexity of the RBMK systems, including the emergency core cooling and related logics is pointed out together with main differences between Smolensk-3 and Ignalina-2 units. Accident scenarios suitable for the analysis, second part of the paper, are derived from recently issued International Atomic Energy Agency (IAEA) reports, from the available Safety Analysis Reports (SAR) of existing RBMK NPP and from the list of bounding accidents derived from the already mentioned EC Project. The features of Korsar and Relap5 thermal-hydraulic system codes developed in Russia and US, respectively, are outlined in the third part of the paper, giving emphasis to the qualification level in the range of parameters of interest to RBMK systems. The adopted nodalisations resembling Ignalina-2 and Smolensk-3 NPP are also described including the demonstration of the qualification level. The results, fourth part of the paper, basically show the overall RBMK system robustness within the DBA area, when the nominal operating conditions constitute the starting conditions for the accident scenarios. However, parallel channel instabilities may trigger dry-out phenomena and consequent rod surface temperature excursion in case of special accident types.