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Okano, Masanori; Akiyama, Kazuki; Taguchi, Katsuya; Nagasato, Yoshihiko; Omori, Eiichi
Dekomisshoningu Giho, (57), p.53 - 64, 2018/03
The construction of Tokai Reprocessing Plant (TRP) was initiated in June 1971, and its hot test using spent fuel started in September 1977. Thereafter TRP had been operated to reprocess 1,140 tons of spent fuel for approximately 30 years until May 2007, according to the reprocessing contract with domestic electric power companies. JAEA announced a policy of TRP in report of JAEA reform plan published in September 2014. The policy shows that TRP will shift to a decommissioning stage by economic reasons. Based on the policy, application of approval for TRP decommissioning plan was submitted to Nuclear Regulation Authority (NRA) in June 2017. This plan provides basic guidelines such as procedures for decommissioning and specific activities for risk reduction, and implementation divisions of decommissioning, management of spent fuels and radioactive wastes, decommissioning budget, and decommissioning schedule. The process of TRP decommissioning is planned to continue for approximately 70 years until the release of controlled areas of approximately 30 facilities.
Kawaguchi, Yoshihito; Morimoto, Kazuyuki; Kitao, Takahiko; Oyama, Koichi; Omori, Eiichi
Nihon Genshiryoku Gakkai Wabun Rombunshi, 8(3), p.221 - 229, 2009/09
30% Tributyl phosphate (TBP)/n-dodecane is used on PUREX process in Tokai Reprocessing Plant (TRP). TBP is degraded to di-butyl phosphate (DBP), mono-butyl phosphate (MBP) etc. mainly caused by radiation, extracted element and hydrolysis. In this study, we studied TBP degradation kinetic equation, Pu concentration in high DBP concentration solution after stripping Pu from the solution by diluted HNO
, DBP concentration in mixer-settler and effect for process while MOX spent fuel was reprocessed and operation was stopped with Pu loaded on solution for 20 days. As a result of this study, we obtained the equation of TBP degradation. Moreover, the maximum DBP concentration in mixer-settler while reprocessing MOX spent fuel was 91 ppm, DBP concentration while stopping operation was 2000 ppm and we found out there was nothing out of the ordinary on the process after the process was restarted.
Nomura, Shigeo; Kikuchi, Ko; Omori, Eiichi; Inano, Masatoshi
Enerugi, 38(6), p.59 - 62, 2005/00
None
; ; ; Omori, Eiichi
JNC TN8410 2001-021, 33 Pages, 2001/09
JNC-TN8410-2001-021.pdf:4.37MB
Carbon-14 released from the nuclear facilities is an important radionuclide for the safety assessment, because it tends to accumulate in environment through food chain and has as a significant impact to personal dose. Carbon-14 has been monitored routinely as one of the main gaseous radionuclides exhausted from the Tokai Reprocessing Plant (TRP) since OCtober of 1991. Furthermore, behavior of carbon-14 in TRP has been investigated through the reprocessing operation and the literature survey. This report describes the result of investigation about the behavior of carbon-14 in TRP as followings. (1)Only a very small amount of carbon-14 in the fuel was liberated into the shear off-gas and most of it was liberated into the dissolver of-gass. Part of the carbon-14 was trapped at the caustic scrubber installed in the of-gas treatment process, and untrapped carbon-14 was released into the environment from the main stack. Amount of carbon-14 released from the main stack was about 4.1
6.5GBq every ton of uranium reprocessed. (2)Carbon-14 trapped at the caustic scrubbers installed in the dissolver off-gas and in the vessel off-gas treatment process is transferred to the low active waste vessel. Amount of carbon-14 transferred to the low active waste vessel was about 5.4 9.6GBq every ton of uranium reprocessed. (3)The total amount of carbon-14 input to TRP was summed up to about 11.915.5 GBq every ton of uranium reprocessed considering the released amount from the main stack and the trapped amount in the off-gas treatment devices. The amount of nitrogen impurity in the initial fuel was calculated about 1522ppm of uranium metal based on the measured carbon-14. (4)The solution in the low active waste vesselis concentrated at the evaporator.Most of the carbon-14 in the solution was transferred into concentrated solution. (5)Tokai vitrification Demonstration Facility (TVF) started to operate in 1994. Since then, carbon-14 has been measured in the ...
Ishida, Michihiko; Sudo, Toshiyuki; Omori, Eiichi; Nojiri, Ichiro
Vol.1 No.040, 1(40), 0 Pages, 2001/00
None
;
Nenryo Saikuru Anzensei Kokusai Wakushoppu, 0 Pages, 2000/00
None
Koyama, Tomozo; ; Omori, Eiichi; ; ; Shibata, Atsuhiro; Shigetome, Yoshiaki
JNC TN8410 99-027, 423 Pages, 1999/12
The bituminization demonstration facility of Tokai Reprocessig Plant had a fire and explosion incident. The cause of the incident was investigated. Also, the facility condition and release of radioactive materials were evaluated. The cause of the fire and subsequent explosion was determined in a two year investigation. The main cause of the fire was that the temperature of the bituminized product rose to an unusually high temperature by a physical heating phenomena inside the extruder, which was caused by the lowering the feed rate of liquid waste. A moderate chemical reaction in the bituminized product continued and consequently the bituminized product overheated and ignited. The cause of the explosion was the accumulation of flammable gases generated from insufficiently extinguished bituminized product in the filling room in which the ventilation system had been shut down. The flammable gas was ignited by another bituminized product that overheated to the flash point temperature. This report details the condition of the facility before and after the incident, cause of the incident, and an evaluated amount of released radioactive materials.
Omori, Eiichi; ; ; ; Maki, Akira; Yamanouchi, Takamichi
JNC TN8410 2000-003, 93 Pages, 1999/10
JNC-TN8410-2000-003.pdf:4.92MB
Radioactive materials in aqueous solution at a nuclear fuel reprocessing plant causes radiolytic generalion of several gases including hydrogen. Hydrogen accumulating in equipment can be an explosion hazard. In such plants, though the consideration in the design has been fundamentally made in order to remove the ignition source from the equipment, the hydrogen concentration in the equipment should not exceed the explosion threshold. It is, therefore, desired to keep the hydrogen concentration lower than the explosion threshold by diluting with the air introduced into equipment, from the viewpoint which previously prevents the explosion. This report describes the calculation of hydrogen generation, evaluation of hydrogen concentration under abnormal operation and consideration of possible improvement at Tokai Reprocessing Plant. The amount of hydrogen generation was calculated for each equipment from available data on radiolysis induced by radioactive materials. Taking into consideration for abnormal condition that is single failure of air supply and loss of power supply, the investigation was made on the method for controlling so that the hydrogen concentration may not exceed the explosion threshold. Possible means which can control the concentration of hydrogen gas under the explosion threshold have been also investigated. As the result, it was found that hydrogen concentration of most equipment was kept under the explosion threshold. It was also shown that improvement of the facility was necessary on the equipment in which the concentration of the hydrogen may exceed the explosion threshold. Proposals based on the above results are also given in this report. The above content has been described in "Examination of the hydrogen produced by the radiolysis" which is a part of "Review of Design Data for Safety Assessment of Tokai Reprocessing Plant" (JNC TN8410 99-002) published in February 1999. This report incorporates the detail evaluation so that operation ...
; ; Omori, Eiichi
JNC TN8410 99-038, 76 Pages, 1999/09
This report describes the observation results of facility damages caused by the fire and explosion that occurred in March 11, 1997 at Bituminization Development Facility of Tokai Reprocessing Plant, JNC. Following to the recently published report ; "Facility damages by the explosion" PNC TN8410 98-013, this report focused on the other red cells than the filling room (R152) and extruder room (R151), and detail of the extruder and inside the filling room that can be observed in accordance with the facility clearing after September 1997. There were little damage in the other cells except the filling room and extruder room, those were only covered with the soot that may be transfered through the ventiration ducts. There was no damage in the body of the extruder except some damages on the discharge nozzle that may be caused by the blown off shielding panel. The detailed damages were also observed inside the filling room. Also the explosion pressure was estimated through the measurement of compressed drum, the results was almost same as the recent estimation.
; ; ; Omori, Eiichi; ; Maki, Akira
JNC TN8410 99-049, 94 Pages, 1999/08
Through the safety evaluation of Tokai Reprocessing Plant, chemical reaction of hydrazine used in some chemical processes was evaluated. The evaluation includes identification of hydrazine decomposition products and reaction velocity under the boiled hydrazine and nitric acid system through the analytical results of chemical test, analysis of ammonium concentration in the recovered plutonium solution in Tokai Reprocessing Plant, investigation of ammonium related phenomena in Germany Reprocessing Plant and evaluation of hydrazine decomposition under the solvent extraction system. It was almost identified that the reaction equation and reaction velocity under the boiled hydfazine and nitric acid system without plutonium. But ammonium concentration of recovered plutonium solution was lower than that of cold solution. That needs chemical test with plutonium. The concentration of azide acid and ammonium nitrate was estimated below the explosion limit. But the analyzed concentration in the process was different from the calculated concentration. That also needs verification in the actual plant.
Omori, Eiichi; Sudo, Toshiyuki; ; Kosaka, Ichiro; ; ;
JNC TN8410 99-005, 274 Pages, 1999/02
Through the investigation of the cause of the fire and explosion incident at Bituminization Demonstration Facility of JNC Tokai Works, the lesson learned is that the safety assessment is necessary even for the licensed facilities by recent knowledge. The safety assessment has been conducted for the facilities in Tokai Reprocessing Plant by recent knowledge and operational experience. This report describes the evaluation results of the incident mitigation systems and the hypothetical accidents. In the evaluation of the incident mitigation system, supposed incidents were solvent fire, rapid reaction of hydrazine decomposition, leakage of radioactive material and loss of power supply. The evaluation was focused on the integrity of the filters in case of the fire and the rapid leaction, the availability of the recovery system in case of the radioactive leakage, and so on. As a result of evaluation, several improvements were pointed out to be necessary for the prevention of incident magnification. In the evaluation of the hypothetical accidents, criticality at a dissolver and fire at solvent extraction mixer-settlers were hypothesized. It was confirmed that the Tokai Reprocessing Plant is still distant enough from the population.
Omori, Eiichi; Sudo, Toshiyuki; ; ; ; ; Maki, Akira
JNC TN8410 99-002, 205 Pages, 1998/11
Through the investigation of the cause of the fire and explosion incident at Bituminization Demonstration Facility of JNC Tokai Works, the lesson learned is that the safety assessment is necessary even for the licensed facilities by recent knowledge. The safety assessment has been conducted for the facilities in Tokai Reprocessing Plant by recent knowledge and operational experience. This report describes the review of the design data for safety assessment of Tokai Reprocessing Plant. The spent fuel inventory, the radio activity balance in the processes, the inventory contained in each equipment, and the evaluation method of public dose were evaluated with the recent data, the new calculation method and the data obtained through the plant operation. The important equipments were selected for safety assessment as for the public dose. The hydrogen generation from radiolysis of solution was also evaluated, and the hydrogen concentration in each equipment was kept lower than the flammable limit except several equipments that are to be improved.
Omori, Eiichi; Suzuki, Hiroshi; Kato, Yoshiyuki; Kitatani, Fumito; Kosugi, Kazumasa; Kikuchi, Naoki
NO.107 P.55-64, (107), p.55 - 64, 1998/09
None
; ; ; Kosugi, Kazumasa; Kikuchi, Naoki; Yamanouchi, Takamichi
Topical Meeting on Safety of the Nuclear Fuel, p.128 - 146, 1998/04
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; Omori, Eiichi; Kato, Yoshiyuki; Suzuki, Hiroshi; Shimoyamada, Tetsuya; Tomiyama, Masahiro; Shimokura, Mitsuharu; Sakuraba, Terumi; Morimoto, Kyoichi; Hagiwara, Masayoshi; et al.
PNC TN8410 98-013, 1028 Pages, 1998/01
PNC-TN8410-98-013.pdf:143.04MB
None
Koyama, Tomozo; ; ; Omori, Eiichi; ; ; Kitatani, Fumito; Kosugi, Kazumasa; Sudo, Toshiyuki; Kikuchi, Naoki; et al.
Nihon Genshiryoku Gakkai-Shi, 40(10), p.740 - 766, 1998/00
Times Cited Count：1 Percentile：15.03(Nuclear Science & Technology)None
Kikuchi, Naoki; Yamanouchi, Takamichi; Omori, Eiichi
PNC TN8410 98-040, 68 Pages, 1997/11
This report describes the results of evaluation of pressure added to room boundaries by explosion at bituminization facility where the fire and explosion accident occured, for the purpose of investigating the cause of the accident. Concerning the fixtures such as shielding door and hatch which were installed on the boundaries between the rooms, the pressure necessary to destroy them was calculated in order to estimate the scale of explosion. Summary of the above results were shown in pressure evaluation drawings. In accordance with the evaluation, we can explain the explosion damage of the facilities quantitatively, and it will be able to estimate the pressure added to room boundaries.
Kikuchi, Naoki; Iimura, Masato*; Takahashi, Yuki*; Omori, Eiichi; Yamanouchi, Takamichi
PNC TN8410 97-310, 117 Pages, 1997/09
Pressure analysis in cell ventilation ducts at bituminization facility where the fire and explosion accident occured was carried out. This report also describes the results of bench mark calculations for computer code EVENT84 which was used for the accident analysis. The bench mark calculations were performed by comparing the analytical results by EVENT84 code with the experimental data of safety demonstration tests of ventilation system which were carried out by JAERI. We confirmed the applicability of EVENT84 code with the conservative results. The pressure analysis in cell ventilation ducts at bituminization facility were performed by comparing the analytical results of duct pressure by EVENT84 code with the yield stress of destroyed ducts by explosion, in order to estimate the scale of explosion. As a result, we could not explain the damage of ducts quantitatively, but we found the local pressure peaks analytically in downstream ducts where the serious damages were observed.
Omori, Eiichi
PNC TJ8124 97-011, 62 Pages, 1997/08
no abstracts in English
Omori, Eiichi; ;
Proceedings of 4th International Conference on Nuclear Fuel Reprocessing and Waste Management (RECOD '94), 0 Pages, 1994/00
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