Investigation on integrity of JMTR reactor pressure vessel

Ide, Hiroshi  ; Kimura, Akihiro ; Miura, Hiroshi; Nagao, Yoshiharu  ; Hori, Naohiko ; Kaminaga, Masanori  

Visual observation of inner side of a reactor pressure vessel (RPV) of JMTR was carried out using an underwater camera before the JMTR refurbishment work, because the RPV of the JMTR will be used continuously after restart of the JMTR. As a result of the visual observation, the harmful wound was not confirmed. Moreover, there was no loosening of the bolts and the screws. On the other hand, adhesion materials which can be easily removed were observed in a top closure. A major component of the adhesion materials is an iron as a result of the componential analysis. However, no significant problem affecting the integrity of the RPV was observed, and then the integrity of the RPV was confirmed. From view points of the stress corrosion cracking, fast neutron fluence and fatigue, it became clear that the RPV of the JMTR can be used for more than 20 years. The visual observation by the underwater camera is to be carried out periodically to confirm the integrity of the RPV in future.