Neutron irradiation behavior of PNC316 stainless steel, which has been
developed for prototype fast breeder reactor MONJU, was investigated
up to a maximum dose of 185 dpa. Excellent swelling and creep properti
es of PNC316 were confirmed and are believed to be the best among this
class of austenitic stainless steels. Performance of a Monju type fue
l assembly was demonstrated at conditions more severe than those antic
ipated in Monju. Significant improvement in the swelling resistance of
PNC316 was mainly due to the formation of a stable phosphide that tra
ps helium bubbles and retards the conversion of bubbles to voids. Tita
nium or increased silicon addition apparently extended the dose for th
e phosphide dissolution and thus extended the swelling incubation peri
od.