Investigation and evaluation of the cause about the loss of split pin which was set to pipe support system of the primary cooling system of Monju

Ichikawa, Shoichi; Kawanago, Sho; Nishio, Ryuichi; Wakimoto, Fumitsugu; Fujimura, Tomofumi; Kobayashi, Takanori; Sakamoto, Tsutomu

JAEA-Review 2015-009, 210 Pages, 2015/07

JAEA-Review-2015-009-01.pdf:60.82MB
JAEA-Review-2015-009-02.pdf:63.6MB
JAEA-Review-2015-009-03.pdf:66.2MB
JAEA-Review-2015-009-04.pdf:62.99MB

The loss of the retaining split pins (four pieces) for clevis pin were confirmed at the inspection of the pipe supports in the Monju prototype fast-breeder reactor in May, 2014. The split pins (two pieces) of ROD RESTRAINT and CONSTANT HANGER were fallen off. The split pins (two pieces) of MECHANICAL SNUBBER were broken at both ends of them. As a result of investigation, a dimple pattern was observed in a fracture surface of broken split pin. This observation result showed that fracture morphology is ductile fracture. A reproduction test, whether split pin was broken by loading the external force to the clevis pin, also gave the same fracture morphology. As the result of all cause investigation, the reason of the broken split pins is that the split pins were loaded shearing stress by the external force loaded to the clevis pin axial direction. The result of the cause investigation and a recurrence prevention measure of this trouble was be reported by this report.

Liquid leakage from the sea release pipe of the Tokai reprocessing plant; Cause investigation of the leak, 1; Progress from mechanical damage to the leak

Wakimoto, Fumitsugu; Morimoto, Kenji; Terunuma, Tomohiro; Ozeki, Tatsuya; Iwasaki, Shogo; Inami, Shinichi

no journal, , 

To investigate the cause of the leak phenomenon from the sea release facilities of the Tokai reprocessing plant, the part of the pipe having the leak point was collected, and the investigations such as surface observation, chemical analysis etc. were performed. As a result, following things were shown as estimated causes; the leak point of the release pipe was mechanically damaged during the construction, breaking occurred on the damaged part by a successive change; and the leak occurred. This paper reports the details of the identified cause that the initial damage by external force would affect the leak phenomenon of the sea release piping.

Material test and bursting test of used rupture disk in Monju

Ichikawa, Shoichi; Ito, Kenji; Wakimoto, Fumitsugu; Tone, Kohei; Watanabe, Yusuke; Kobayashi, Takanori; Uekura, Ryoichi

no journal, , 

To establish an exchange frequency of a rupture disk (hereinafter called "RD") installed in a evaporator and a superheater (hereinafter called "ED", "SH") of the prototype fast-breeder reactor MONJU (hereinafter called "MONJU"), the purpose of this study is to estimate the aging degradation of used RD in MONJU and material test and bursting test of used RD were carried out. When massive Na-HO reaction occurred in the ED, SH, RD is the equipment which was installed for the purpose of the case that the pressure in the secondary heat transportation system is opened and opening of the pressure is detected. From the result of the examination, material characteristics were not a significant degradation. On the other hand, the bursting pressure was slightly changed. However the change was in the reach of the request value of the secondary heat transportation system. To establish the exchange frequency of the high precision for the RD, expansion of further data is needed.