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Keywords: NEK, model, APROS 6, Containment, LOCA, accident, blowdown, spray, sump
Abstract
Containment is a combination of a steel shell and concrete shield building enclosure, completely surrounding a nuclear reactor, designed to prevent the release of radioactive material in the event of an accident. The NEK (Krsko Nuclear Power Plant) reactor containment building nodalization in APROS 6 computer code has been developed based on the plant's available documents and GOTHIC nodalization. The heat structure's data are based on USAR (Updated Safety Analyses Report) Chapter 6 passive heat structures. In all other aspects, realistic calculations based on containment geometry have been performed except for the interior concrete, which has been explicitly calculated.
An original containment nodalization based on 10 control volumes is proposed, taking into account the containment layout (well-defined physical boundaries and corresponding communication openings) and accident behaviour. The nodalization is suitable for containment thermal-hydraulic modelling according to design basis accidents. In the end, APROS nodalization is prepared based on the same 10-volume nodalization, for which annulus-volume is also included in the model, connecting the reactor building to the environment. The containment model was tested for transient response for conditions, which occur in a Double-Ended Hot Leg Guillotine Break accident.
Povzetek
Zadrzevalni hram je zgradba, v kateri so komponente znotraj tlacne meje reaktorskega hladila, ki predstavljajo pregrado pred nenadzorovanim sproscanjem radioaktivnosti v okolje. V programu APROS je na podlagi razpolozljivih dokumentov in nodalizacije programa GOTHIC zmodeliran model zadrzevalnega hrama jedrske elektrarne NEK. Podatki za izracune posameznih struktur so povzeti iz dokumenta USAR (posodobljenega varnostenga porocila) - poglavje 6, ki opisuje pasivne toplotne strukture. Model zadrzevalnega hrama, ki je sestavljen iz 10 (fizikalno dobro definiranih) povezanih prostorov, je primeren za simulacijo jedrskih nesrec. APROS model zadrzevalnega hrama vsebuje tudi vmesni prostor, ki povezuje notranjost zadrzevalnega hrama z zunanjim okoljem. Z modelom je bil preverjen odziv modela zadrzevalnega hrama na prehodni pojav, ki nastane pri dvojnem giljotinskem zlomu vroce veje reaktorskega hladilnega sistema.
1INTRODUCTION
Nuklearna Elektrarna Krsko (NEK) containment systems consist of a steel shell containment, concrete shield building, penetrations, and directly associated systems such as the containment isolation system, the containment spray system, the containment air recirculation and cooling system, and the combustible gas control system.
The Containment System is designed for all break...