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Miura, Akihiko;
JNC TN8410 99-044, 189 Pages, 1999/10
This report includes several results that were made by calculation with several methods to clarify the cause of the fire and explosion incident. In the early times, we didn't have exact information of chemicaI property, reaction rate and any physical constants that we needed. But because the only data that indicate the cooling process of bituminized product was reported, we made heat-transporting calculation with taking this data. Based on the theory of the thermal hazard evaluation that was called Semenov theory or Frank-Kamenetskii theory, the amount of heat generation was estimated using the heat transporting calculation. Common theories were introduced in first section. In the second section, several results of heat transporting calculation were indicated. Calculations were made as follows. First, the model of bituminized product that was filled in the drum was created with the data of cooling process. Second, when the heat was generated in the drum, time-dependent temperature distribution was calculated. And last, judging from the balance of heat generation and heat radiation the critical heat rate was estimated.
; Miura, Akihiko; ;
JNC TN8410 99-043, 135 Pages, 1999/10
All result of chemical analysis and operators observation suggest non-chemical mechanism raised the filling temperature of the bituminized product at the incident. We, Tokai reprocessing plant safety evaluation and analysis team, performed the experiment using laboratory scale extruder and viscosity measurement to explain the high temperature of mixture. The result of the experiment using laboratory scale extruder showed that the phenomena of salt enrichment and salt accumulation oceured and they raised mixture temperature at the decreased feeed rate. These phenomena depend on the feed rate and they have large contribution of heat transportation and rise of operational torque due to the friction between screw and mixture. Based on the experiment result and all information, we investigated the operation procedure, operational records and machine arrangement to try to explain the behavior of the mixture in the extruder. Judging from each torque and temperature behavior, we succeeded in explaining a sequential behavior in the incident. It is estimated that mixture temperature was raised by physical heat generation in the extruder and this report explains each operation, investigated result and estimated event sequences.
; 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.
