AbstractThe decay heat stored in a fusion reactor after a year of operation has the potential to cause at least a partial meltdown of the reactor structure. A narrow outboard sector of the ITER has been modelled in conditions similar to those after a total LOCA (Loss Of Coolant Accident) with the purpose of estimating the temperature histories of the various components after an accidental shutdown. Three structural steels, MANET, AMCR 0033 and IF-B, were considered in place of the reference AISI 316L, in order to check the effect of their thernal, activation and shielding properties on the post accident thermal transient. The reference design, with AISI 316L steel, presents relatively low temperatures during the first weeks (peak after 3.5h). Problems may arise only within a long while after the accident (two months), if absolutely no emergency measures are taken: onlt at that time the temperature will reach a maximum close to its melting point. It was verified that both AMCR 0033 and IF-B steels present potentially dangerous temperature peaks at about 3.5h after the accident ad thus are not a good alternative to the reference steel. By far the best steel is MANET, as far as the post LOCA transient is concerned. It presents a 15% lower short-term temperature peak and, most important, at long term it has about half the temperature (in absolute) of the reference design.
On the potentiality of using ferritic/martensitic steels as structural materials for fusion reactors