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Kanamori, Masashi
JNC TN8440 2001-018, 50 Pages, 2001/12
JNC-TN8440-2001-018.pdf:1.31MB
On September 30 at around 10:35 AM, criticality accident occurred at the JCO's conversion building in Tokai-mura. Since criticality accident had not been anticipated, neither devices for termination of criticality accident nor neutron detectors were available. Immediately after the information of the accident, our emergency staff (Japan Nuclear cycle development institute staff) went to JCO site, to measure the intensity of neutrons and gammas. There were four main tasks, first one was to measure the radiation intensity, second one was to terminate the criticality accident, third one is to alert the residents surrounding the JCO site, fourth one is to evacuate the employees in the site. These tasks were successfully performed until October 1. This paper describes about how these operations were performed by the relevant staffs.
; Aoyama, Makoto; ; Yamanouchi, Takamichi
PNC TN8410 97-319, 143 Pages, 1997/10
The fire and explosion incident occurred at Bituminization Demonstration Facility of PNC Tokai Works on March 11, 1997. In order to ascertain the cause of incident, the investigation has been pushed forward. During investigation, we obtained essential information from operators, such as softness of bituminized product, white smoke generated from bituminized product. This condition has never been observed comparing past normal operation. Therefore, we assumed that temperature of bituminized product had increased more than expected. In order to confirm above assumption, we made experiment for obtaining the relationship between temperature and fluidity of bituminized product. Simulated bituminized product was heated up to each temperature (210, 230, 250, 270
C) in a pot and poured down into an another pot. We observed the fluidity of bituminized product when it flowing down into a pot. The fluidity of bituminized product increased with high temperature. The fluidity of bituminized product at 270C looked similar to fluidity of bituminized product that had ignited itself at the incident. White smoke generated from bituminized product and amounts of white smoke increased with high temperature. The smoke was considered to be gas that generated through thermal decomposition or volatilization of bitumen.
Sekio, Yoshihiro; Sato, Isamu*; Kawashima, Masatoshi*; Morita, Koji*
no journal, ,
A proposed passive reactor shutdown device contains pins with fuels that are kept in the solid state during normal operation but melt into the liquid when its temperature exceeds a prescribed value under severe accidents. The device leads reactor to subcritical state by liquid fuel migration to low positions in the pins. In this study, the device structure for fast reactor core was proposed based on safety evaluation results. The liquid fuel is needed to migrate before the accident occurs, and the migration time would depend on the fuel viscosity. To obtain basic acknowledge for determination of fuel chemical components, the effect of material viscosities on fuel migration time was evaluated through visualization experiments using liquid samples with different viscosities.
Sekio, Yoshihiro; Sato, Isamu*; Kawashima, Masatoshi*; Morita, Koji*
no journal, ,
A proposed passive reactor shutdown device contains pins with fuels that are kept in the solid state during normal operation but melt into the liquid when its temperature exceeds a prescribed value under severe accidents. The device leads reactor to subcritical state by liquid fuel migration to low positions in the pins. In this study, for the purpose of obtaining basic knowledge for evaluating the engineering feasibility of the proposed device structure, we made a simulated device pin using a simulated solid fuel, a thin pipe and so on. The melting and migrating behaviors of the solid fuel in the pin were evaluated through visualization experiments.