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Ad-hoc Committee for Investigation on Malfunction of Safety Rod in
JAERI-Review 2005-006, 60 Pages, 2005/03
JAERI-Review-2005-006.pdf:5.09MB
A trouble, malfunction of a safety rod, occurred during transient operation of the Transient Experiment Critical Facility (TRACY) in Japan Atomic Energy Research Institute (JAERI) on June 17, 2004. JAERI organized its specialists into the ad-hoc committee for investigation on malfunction of a safety rod of TRACY on June 23, 2004, to understand the cause of the trouble and take countermeasures to prevent the issue. The ad-hoc committee held 11 meetings and had discussions on the trouble inquiring the situations of the TRACY operation and the results of examination from the division relevant to the TRACY. As the result of investigation the cause of the trouble was attributed to the following reason: The holding capability of the safety rod was temporarily depressed by a small piece of polyethylene sheet put between the electromagnet and armature of the safety rod, the polyethylene sheet which had been used in overhaul activities of the rod. In the present report, the detailed results of investigation and the countermeasures to prevent the trouble are described.
Sono, Hiroki; Tsukamoto, Michio; Aizawa, Eiju; Takeuchi, Masaki; Fukaya, Yuji; Iseda, Hirokatsu*; Ogawa, Kazuhiko; Sakuraba, Koichi; Tonoike, Kotaro
UTNL-R-0446, p.3_1 - 3_10, 2005/03
This report describes an investigation and countermeasures of the unexpected reactor shutdown of the TRACY facility at the Japan Atomic Energy Research Institute on June 17, 2004, caused by a malfunction of a safety rod of the facility. As a result of the investigation, the principal cause of the malfunction was ascribed to a drop in attraction of a binding magnet for the safety rod by a small piece of a foreign material. The following countermeasures were taken against its recurrence: prevention of incidence of foreign materials, reduction of the chance of intrusion of foreign materials into devices, and certain detection of foreign materials. This lesson learned through the experience is expected to be shared with the staffs concerned in reactor operation and maintenance.
; *; Yoshida, Eiichi; Aoto, Kazumi
JNC TN9400 2000-011, 33 Pages, 1999/03
JNC-TN9400-2000-011.pdf:13.45MB
The damage was observed in rupture disk for the A-loop superheater of sodium-water reaction products releasing system for MONJU on March 3, 1998. Low temperature creep and stress corrosion cracking tests were carried out as the causes investigation of the damage. As the result, the followings are clarified. (1)The possibility that low temperature creep is the principal damage is small. (2)The stress corrosion cracking under NaOH environment due to the reaction of Na vapor and moisture condensed on the surface of glass beads as remains is the most probable cause on the damage. (3)Comparatively many glass beads remained in damaged surface. The gap between rupture disk and vacuum support was narrower than other parts, and they were not directly exposed to the Na vapor for a long time. The above factors caused the perfect intergranular cracking by stress corrosion. Since NaOH was chemically changed into the harmless Na
O on the location except for damaged zone by full Na vapor, the stress corrosion cracking was not generated.