Fast reactor cores are not operated in their most reactive configuration and material relocations during severe accidents can generate power excursions. A hypothetical core disruptive accident (HCDA) scenario was studied in the past for sodium fast reactors, to ensure that the reactor vessel could sustain the mechanical loads caused by the energetic excursion following fuel compaction reactivity insertions up to 100 dollars/second. This scenario was originally evaluated by an analytical model, the Bethe-Tait model.
MYRRHA is a fast spectrum irradiation facility cooled by liquid lead-bismuth eutectic (LBE) (http://myrrha.sckcen.be/) and its design is under development at SCK•CEN. For the mitigation of severe accidents, an in-vessel retention strategy is adopted as being most effective in limiting radiological consequences to the population.
Starting from postulated configurations of a binary system fuel-LBE, the PhD work will investigate the disassembly mechanisms during a HCDA in the MYRRHA core, doing sensitivity studies on the governing parameters and estimating the mechanical energy released to the vessel after the disassembly phase, by means of the SIMMER best-estimate code and by analytical models.