MELCOR súlyos baleseti elemző kód validálása gázhűtésű gyorsreaktorra

Az ALLEGRO projekt keretein belül a tervek szerint a közeljövőben megépülhet a negyedik generációs atomerőművekhez tartozó gázhűtésű gyorsreaktor demonstrációs reaktora. Természetesen ezen új típusú reaktoroknak is meg kell felelniük a különböző biztonsági előírásoknak, a biztonsági rendszerek megtervezéséhez pedig ismerni kell a lehetséges baleseti, súlyos baleseti folyamatokat. A hagyományos atomerőműveknél használt súlyos baleseti elemző kódok azonban vízhűtésre lettek megalkotva, így külön vizsgálat nélkül nem alkalmazhatók gázhűtés esetén. A cikkben a MELCOR súlyos baleseti elemző kód tisztán gáz közegben történő alkalmazhatósága kerül bemutatásra. A kód ellenőrzése a HEFUS, héliummal hűtött és elektromosan fűtött kísérleti berendezésen végzett stacioner és tranziens kísérletek alapján történt. Validation of the MELCOR severe accident code for gas cooled reactors The potential, which lies in the 4th generation of nuclear reactors is huge. There are still many R&D work to be done, to be able to use this potential in the future. To accelerate these researches the Generation IV International Forum (GIF) chose six from the many innovative, new reactor types, to be the main target of the developments. This work is about the gas-cooled fast reactor (GFR), which is one of the six chosen reactor types. According to plans, a 75 MW demonstrational GFR is going to be built in the 2020s, called ALLEGRO. There are still many tasks, which have to be done, before the constructions can start. One of the tasks is also the topic of this work: the severe accident codes, which are widely used for water cooled reactors, have to be checked, whether their equations, correlations give correct results in gas cooled cases. To answer this and many other questions, the HEFUS experimental facility was built, in which they modelled the primary circuit of a gas-cooled fast reactor. The nuclear power was simulated by electrically heated rods, which were cooled with high pressure helium. The hot helium transmitted its heat to the environment through heat exchangers. During my work I created the model of the HEFUS experimental facility in the MELCOR 1.86 severe accident code, which was developed by the Sandia National Laboratories. After that, I ran simulations under steady state and transient conditions and compared the simulated results with the measurements. The comparison of the results showed, in several cases quite large deviations. The results of the comparison are described in the work. Only if the validations of the codes are finished can the work on the ALLEGRO project continue.

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