Three surveillance programs of the JPDR pressure vessel have been performed to date. From the assessment of both the shift of NDT temperature and the reduction of upper shelf energy in the pressure vessel steel due to irradiation, it was concluded that the pressure vessel could be used with safety for about ten years at equivalent full power (45 MWt) operation.

A reference test was also performed on two potential steels for pressure vessel use, namely a Mn-Mo-0.4∼0.7Ni steel (A533B Class 1) and a 2 1/4Cr1Mo (A542 Class 1) steel, following the completion of the surveillance test. The latter steel was found to be much less sensitive to irradiation than the former. The weld metal and heat affected zone are somewhat more sensitive to irradiation than the base metal for the 2 1/4Cr-1Mo steel submerged arc weldment.