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JAEA Reports

Review of design data for safety assessment of Tokai reprocessing plant; Control of hydrogen gas produced by radiolysis of reprocessing solutions at Tokai reprocessing plant

; ; ; ; 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 ...

Journal Articles

An Investigation of the Cause of the Fire and Explosion Incident at Bituminization Demo

; Koyama, Tomozo; Maki, Akira; Yamanouchi, Takamichi

Proceedings of International Conference on Future Nuclear Systems (GLOBAL '99) (CD-ROM), 0 Pages, 1999/08

None

JAEA Reports

Evaluation of pressure transient of the facility by FIRAC code

Kosaka, Ichiro; Nojiri, Ichiro; Yamanouchi, Takamichi

JNC TN8410 99-017, 302 Pages, 1999/03

JNC-TN8410-99-017.pdf:13.87MB

For the purpuse of the analysis the loss of the containment of the gas, the pressure transients had been caluculated, using FIRAC Code, caused by the first fire incident in the Bitiminization filling cell, R152, and by the corst down of the cell exhaustion, limited operation of the ventilation system, begining at 1006, 11th, March, 1997. The FIRAC Code calculates the pressure and temperature of the cell and ventilation system at the fire incident. The all of the facility was modeled in the calculations. The heat generation rate and other unknown terms were taken into as the caluculational parameters, and the process of the incident were evaluated by attention to the different results by each parameter. In the results, the constraction of the ventilation system affected the process of the fire incident, and in the case taking account of exhausting to Z-facility, abnormal reverse flow occurred in the system.

JAEA Reports

Safety evaluation of Tokai Reprocessing Plant (TRP); Report of safety evaluation of Tokai Reprocessing Plant

Maki, Akira; Nojiri, Ichiro; ; ; Yamanouchi, Takamichi

JNC TN8440 99-002, 366 Pages, 1998/11

JNC-TN8440-99-002.pdf:27.42MB

The fire and explosion incident of the bituminization facility happened in March 1997 although JNC had taken enough care of the safety of TRP. JNC reflected on it and decided to evaluate the safety of TRP voluntarily. This evaluation has included five activities, that is, (1)confirmation of the structure and organization of TRP, (2)research of the data for operation, radiation and maintenance of TRP, (3)research of reflection of the accidents and troubles which have happened at the past, (4)evaluation on the prevention system, (5)evaluation on the mitigation system. We publish this report to contribute to inheritance of accumulated knowledge and techniques from generation to generation, and remind us of lesson from the fire and explosion incident of the bituminization.

JAEA Reports

Assessment of basic data for criticality safety and shielding design of Tokai reprocessing plant

Sudo, Toshiyuki; ; ; Nojiri, Ichiro; Maki, Akira; Yamanouchi, Takamichi

JNC TN8410 99-003, 69 Pages, 1998/11

JNC-TN8410-99-003.pdf:5.49MB

As a part of the safety confirmation work of Tokai Reprocessing Plant, the appropriateness was checked on the basic data used in criticality safety and shielding design of early-designed facilities in the plant on the basis of recent knowledge and safety evaluation methods. In the criticality safety design, it was confirmed that critical and subcritical values concerning mass and concentration of U and Pu and equipment dimension were appropriate. In the shielding design, it was found that the relation between shielding thickness and permissible radioactivity might give underestimated results of shielding thickness necessary to limit dose rate to the designated one on some condition. In this cases, however, it was confirmed that necessary shielding thickness has been secured because of the conservative calculation conditions for the real conditions except the operation test laboratory (OTL). However, the amount of radioactivity handled at OTL needs to be limited. From a viewpoint of criticality safety, operational control for U and Pu transfer was also investigated, As a result of it, at the transfer route where erroneous batch-wise transfer of process solution might lead to a criticality accident, the reliability of U and Pu concentration measurement needs to be improved by multiple measurements. At other transfer routes, it was confirmed that single failure of equipment or operation error would not lead to a criticality problem.

JAEA Reports

Damage of cell ventilation filters in the fire and explosion incident of bituminization demonstration facility

Shigetome, Yoshiaki; ; Yamanouchi, Takamichi; Oda, Yoshihiro;

PNC TN8410 98-088, 48 Pages, 1998/05

PNC-TN8410-98-088.pdf:3.74MB

At the fire and explosion incident of Bituminization Demonstration Facility, the fault of cell ventilation system (plugging of the HEPA filter) occurred in a short time. In addition the breakdown of the filter occurred at the explosion which happened ten hours after the extinguishment of the fire. Investigation of filter damage was conducted in order to know the extent of the breakdown, the contamination by radioactivity and soot mass gain of HEPA filter. Scanning electron micrograph (SEM) was also used to observe the appearance of soot adhesion on the filter media. This report shows the result of the investigation.

Journal Articles

None

; ; ; Kosugi, Kazumasa; Kikuchi, Naoki; Yamanouchi, Takamichi

Topical Meeting on Safety of the Nuclear Fuel, p.128 - 146, 1998/04

None

JAEA Reports

Calculation of the reverse air flow rate to cells from the vessel ventilation system

Kosaka, Ichiro; Yamanouchi, Takamichi;

PNC TN8410 98-027, 114 Pages, 1998/02

PNC-TN8410-98-027.pdf:2.72MB

At 11th, March, 97, the fire incident happened, and after the fire incident, the explosion happened in the Bitiminization Demonstration Facility. It has been suspected that the reverse air flow to filling room(R152) from the vessel ventilation system made the explosive atmosphere after the fire incident. The calculation of the reverse flow rate to the cell was therfore carried out, using FIRAC computer code. The FIRAC is designed for the calculation of a fluid temperature, pressure and flow rate, using lumped-parameter method. In the FIRAC, the network system is modeled as nodes and branches. As the results of calculation, the reverse air flow rate to R152 from vessel ventilation system is about 94 m$$^{3}$$/h and the reverse air flow rate to the other cells are slight, assuming that the leak rate from R152 is 650 m$$^{3}$$/h and others are 1 vol%/h when the pressure difference is 40 mmAq. On the other hand, the reverse air flow rate to R152 is about 34m$$^{3}$$/h, the reverse air flow rate to the cells in the underground stairs is about 39 m$$^{3}$$/h and to the others are from 5 to 10 m$$^{3}$$/h, assuming that the leak rate from all cells are 1 vol%/h when the pressure difference is 40 mmAq.

JAEA Reports

None

*; *; *; *; Yamanouchi, Takamichi*

PNC TN8440 98-001, 159 Pages, 1998/01

PNC-TN8440-98-001.pdf:23.08MB

None

JAEA Reports

Facility damages by the explosion

; 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

Journal Articles

An Investigation of the Cause of the Fire and Explosion Incident at Bituminization Demonstration Facility

; Koyama, Tomozo; Maki, Akira; Yamanouchi, Takamichi

7th International Conference on Radioacti, 0 Pages, 1998/00

None

Journal Articles

The Fire and Explosion Incident at Bituminization Demonstration Facility of PNC Tokai Works

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:15.05(Nuclear Science & Technology)

None

JAEA Reports

None

Yamanouchi, Takamichi; Kyue, Tadashi; Nagai, Toshihisa

PNC TN8410 97-368, 135 Pages, 1997/12

PNC-TN8410-97-368.pdf:7.9MB

None

JAEA Reports

Evaluation of pressure added to room boundaries by explosion at bituminization facility; Fracture strength analysis of damaged fixtures

Kikuchi, Naoki; Yamanouchi, Takamichi;

PNC TN8410 98-040, 68 Pages, 1997/11

PNC-TN8410-98-040.pdf:4.92MB

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.

JAEA Reports

Test on the flowing down of simulated bituminized product

; Aoyama, Makoto; ; Yamanouchi, Takamichi

PNC TN8410 97-319, 143 Pages, 1997/10

PNC-TN8410-97-319.pdf:36.19MB

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$$^{circ}$$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 270$$^{circ}$$C 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.

JAEA Reports

Pressure analysis in ventilation ducts at Bituminization Facility

Kikuchi, Naoki; Iimura, Masato*; Takahashi, Yuki*; Omori, Eiichi; Yamanouchi, Takamichi

PNC TN8410 97-310, 117 Pages, 1997/09

PNC-TN8410-97-310.pdf:5.43MB

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.

Journal Articles

Facility outline and construction status of recycle equipment test facility (RETF)

; Yamanouchi, Takamichi; *; Shikakura, Sakae; Kawata, Tomio; *

Proceedings of 5th International Conference on Nuclear Engineering (ICONE-5), 0 Pages, 1997/05

None

JAEA Reports

None

; Maki, Akira; Yamanouchi, Takamichi; ; Ogata, Yoshiaki; ;

PNC TN8440 97-020, 111 Pages, 1997/03

PNC-TN8440-97-020.pdf:35.99MB

None

Journal Articles

Outline of Recycle Equipment Test Facility (RETF) Project

; Yamanouchi, Takamichi; *; Shikakura, Sakae; Kawata, Tomio; *

Proceedings of International Conference on Future Nuclear Systems (GLOBAL'97), 0 Pages, 1997/00

None

Journal Articles

Facility outline and construction status of Recycle Equipment Test Facility

; Yamanouchi, Takamichi; ; Shikakura, Sakae

Proceedings of International Conference on Future Nuclear Systems (GLOBAL'97), 0 Pages, 1997/00

None

27 (Records 1-20 displayed on this page)