ALLEGRO Core Degradation Study using MELCOR 2.1

Abstract: ALLEGRO is an experimental high-temperature gas (He)-cooled fast reactor (GFR) under development by the European Consortium V4G4 Centre of Excellence on basis of the concept ALLEGRO presented by CEA in 2009. Its main purpose is to demonstrate the viability of GFR in pilot scale and simultaneously serve as a test bed for GFR-related technologies, above all the high-temperature resistant refractory fuel in the conventional oxide fuel driver core. Severe accident studies of the concept with the first core (oxide fuel in stainless steel claddings) are an important part of safety analyses leading to improves in reactor design and safety. This paper extends our previous study using the MELCOR code. Major difference between the previous and this work is decrease of thermal power and power density to 50 MWth and 66,6 MWth/m3 respectively. Analyses are focused on protected scenarios based on total station blackout individually aggravated by loss of primary coolant, water ingress into primary coolant or malfunction of check valves in the decay heat removal system. The results indicate the timing and extent of core degradation and provide valuable data for design of the core catcher in ALLEGRO.