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Journal Articles

Journal Articles

Radioactive waste management in O-arai Research and Development Center

Maeda, Atsushi; Kowata, Koichi; Yamazaki, Yasuo; Takahashi, Kozo; Okubo, Toshiyuki; Miyazaki, Hitoshi

Dekomisshoningu Giho, (33), p.58 - 66, 2006/03

By the Japan Atomic Energy Agency (JAEA), designed decommissioning of nuclear facility and the treatment and disposal of radioactive waste will be carried out systematically and efficiently as responsibility as the installer of the nuclear power facility and generator of radioactive waste. This paper shows the present status of radioactive waste management in O-arai Research and Development Center, one of the research and development bases of JAEA. The management of low-level radioactive waste, including those accepted from outside operator of O-arai district, is carried out by the major premise of ensuring safety at O-arai Waste Management Facility. Treatment related to volume reduction and stabilization by means such as incineration and compression of solid waste, and solidification of liquid, as well as waste storage management is steadfastly promoted, so that these substances may be adequately stored and managed until they are disposed of.

JAEA Reports

Development of decommissioning management system (10); Improvement of evaluation accuracy and simplification of input work

Kondo, Hitoshi; Miyazaki, Hitoshi*; Okubo, Toshiyuki

JNC TN9410 2005-009, 32 Pages, 2005/03

JNC-TN9410-2005-009.pdf:4.62MB

When the plan of Decommissioning such as nuclear fuel cycle facilities and small-scale research reactor is settled on, it is necessary to optimize the index concerning the decommissioning (such as the cost, the waste and the term of works. etc) by selecting the technology and the process appropriately. In Waste Management section, the development of the Decommissioning Management System (DECMAN) which can calculate these decommissioning indexes from the facilities data and the dismantlement technique automatically is advanced. This report describes the problem found in 2003 and the solution concerning the operation and the evaluation technique.

JAEA Reports

None

Wada, Yusaku; Okubo, Toshiyuki; Miyazaki, Hitoshi; none; Donomae, Yasushi

JNC TN9410 2005-007, 94 Pages, 2005/03

JNC-TN9410-2005-007.pdf:6.07MB

None

JAEA Reports

Development of chemical decontamination method for old Waste Treatment Facility

Fukuda, Seiji; Kondo, Hitoshi; Okubo, Toshiyuki

JNC TN9410 2004-010, 56 Pages, 2004/03

JNC-TN9410-2004-010.pdf:1.53MB

The Old Waste Treatment Facility of JOYO(0ld JWTF), operation of which stopped in 1995, is scheduled to be dismantled starting in 2010. In order to reduce worker's radiation exposure, it is necessary to reduce radiation dose rate of the main equipments by system chemical decontamination before dismantling. In thjs research, the decontamination solutions were selected in view of reduction of consequential waste amount and expense of treatment of decontamination waste. We evaluated decontamination factor (DF) in test with contaminated samples (Hot test). Moreover we performed a conceptual design of the decontamination system using the decontamination solution that obtained the highest DF in hot test. The solution selected in hot test did not achieve the target DF to all equipments. For some equipment more aggressive solutions, which dissolve contaminants and base metal, would be needed, however using these solutions would tend to increase consequential waste amount and expense of treatment of decontamination waste. Therefore, we evaluated the dissolution rate of these solutions for stainless steels in test with non-contaminated samples (Cold test). The main result of obtaining through the hot test and the cold test is shown below.(1)By alternating immersions in sodium hydroxide solution and nitric acid, the highest DF was obtained. (Maximum of DF=10.7, 80 deg-C). (2)The decontamination system is composed of two decontamination solution tanks, a washing water tank, a pump that supplies decontamination solutions and washing water, and filters for removing contaminants. (3)The test samples were immersed in various solutions (HN03 + HF, HCl, H2S04) for 24 hours at room temperature. As a result, it was confirmed that the dissolution rate of HN03 + HF is remarkably large compared with other solutions (7.43 micro-m/day).

JAEA Reports

Development of decommissioning management system (9) -Remodeling to PC system and System verification by evaluation of real work-

Kondo, Hitoshi; Fukuda, Seiji; Okubo, Toshiyuki

JNC TN9410 2004-007, 48 Pages, 2004/03

JNC-TN9410-2004-007.pdf:7.35MB

When the plan of decommissioning such as nuclear fuel cycle facilities and small-scale research reactors is examined, It is necessary to select the technology and the process of the work procedure, and to optimize the index (such as the radiation dose, the cost, amount of the waste, the number of workers, and the term of works, etc.) concerning dismantling the facility. In our waste management section, Development of the decommissioning management system, which is called "DECMAN", for the support of making the decommissioning plan ls advanced. DECMAN automatically calculates the index by using the facility data and dismantling method. This paper describes the remodeling of program to the personal computer and the system verification by evaluation of real work (Dismantling of the liquor dissolver in the old Joyo Waste Treatment Facility (the old JWTF), the glove boxes in Deuterium Critical Assembly (DCA), and the incinerator in Waste Dismantling Facility (WDF)). The outline of remodeling and verification is as follows. (1)Additional function. 1)Equipment arrangement mapping, 2)Evaluation of the radiation dose by using the air dose rate, 3)I/O of data that uses EXCEL (software) (2)Comparison of work amount between calculation value and results value: The calculation value is 222.67 man-hour against the result value 249.40 man- hour in the old JWTF evaluation. (3)Forecast of accompanying work is predictable to multiply a certain coeffient by the calculation value. (4)A new idea that expected the amount of the work was constructed by using the calculation value of DECMAN.

JAEA Reports

Development of JOYO plant operation management expert Tool (JOYPET)

; Terano, Toshihiro; ; ; Okubo, Toshiyuki

JNC TN9410 2000-004, 30 Pages, 2000/03

JNC-TN9410-2000-004.pdf:0.86MB

The Operation and Maintenance Support Systems for JOYO are being developed, with the aim of ensuring the stable and safe operation of JOYO and improving operational reliability of future FBR plants. Plant Operation Management Expert Tool named JOYPET had been developed as one of the Operation and Maintenance Support Systems, which helps plant operation management. The following functions were developed and applied. (1)Papers management (Plant status management) function for maintenance activities (2)Isolation management support function for plant operation (3)Automatically drawing function of plant operation schedule (4)Isolation judgment function for plant operation By use this system, the plant management of JOYO was able to improved reliability and reduced manpower.

JAEA Reports

development of the automatic control rod operation systel for JOYO; Verification of Automatic control rod operation guide system

; ; ; Okubo, Toshiyuki

JNC TN9410 99-021, 51 Pages, 1999/10

JNC-TN9410-99-021.pdf:4.1MB

The automatic control rod operation system was developed to control the JOYO reactor power automatically in all operation modes (critical approach cooling system heat up. power ascent, power descent), development began in 1989. Prior to applying the system verification tests of the automatic control rod operation guide system was conducted during 32nd duty cycles of "JOYO" from Dec.1997 to Feb.1998. The automatic control rod operation guide system consists of the control rod operation guide function and the plant operation guide function. The control rod operation guide function provides information on control rod movement and position, while the plant operation guide function provide guidance for plant operations corresponding to reactor power changes (power ascent or power descent). Control rod insertion or withdrawing are predicted by fuzzy algorisms. The main results obtained via the verification tests are as follows: (1)Control rod operation guide function provided adequate information on control rod operation in all operation modes. (2)Plant operation guide function provided adequate guidance for the plant operation. (3)The technical themes were specificed for the verification tests of the automatic control rod operation system. (4)It was concluded that the automatic control rod operation system can be used to automatically control the JOYO reactor power.

Journal Articles

Performance test of the HTTR

Tanaka, Toshiyuki; Okubo, Minoru; Iyoku, Tatsuo; Kunitomi, Kazuhiko; Takeda, Takeshi; Sakaba, Nariaki; Saito, Kenji

Nihon Genshiryoku Gakkai-Shi, 41(6), p.686 - 698, 1999/00

 Times Cited Count:4 Percentile:34.88(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Present status of the High Temperature engineering Test Reactor (HTTR)

Tanaka, Toshiyuki; Okubo, Minoru; Fujikawa, Seigo; Mogi, Haruyoshi; Suzuki, Hiroshi

Proc. of PBNC'98, 2, p.1203 - 1210, 1998/00

no abstracts in English

Journal Articles

Present status of the High Temperature engineering Test Reactor(HTTR)

Tanaka, Toshiyuki; Shiozawa, Shusaku; Okubo, Minoru; Fujikawa, Seigo; Mogi, Haruyoshi; Suzuki, Hiroshi

Proceedings of European Nuclear Conference (ENC'98), 4, 5 Pages, 1998/00

no abstracts in English

JAEA Reports

Development of operation and maintenance support system for JOYO; Development of JOYO plant operation management expert tool (JOYPET)(2)

; Okubo, Toshiyuki;

PNC TN9410 98-001, 55 Pages, 1997/10

PNC-TN9410-98-001.pdf:1.67MB

The operation and Maintenance Support Systems for JOYO are being developed, with the aim of ensuring the stable and safe operation of JOYO and improving operational reliability of future FBR plants. The operation support system named JOYPET has been developed from FY1989 as one of the systems, which helps plant operation management that require much labor and knowledge on plant. This report discribes the result of developing and using on judgment function of final development this system. A judgment function, which judges permission to do isolation for maintenance activities from the status of the plant and equipments based on the accumlated plant management rules of JOYO, has been developd from FY1994. By using this function from FY1996, it was able to do which strict with isolation management of JOYO. And improvements in this function were obtained.

JAEA Reports

Counter-measure to prevent temperature rise of stand pipe and primary upper shielding in HTTR

Kunitomi, Kazuhiko; Tachibana, Yukio; *; Nakano, Masaaki*; Saikusa, Akio; Takeda, Takeshi; Iyoku, Tatsuo; ; Sawahata, Hiroaki; Okubo, Minoru; et al.

JAERI-Tech 97-040, 91 Pages, 1997/09

JAERI-Tech-97-040.pdf:2.51MB

no abstracts in English

JAEA Reports

A study for leak testing in the fuel handling facility "JOYO"

Ito, Hideaki; ; ; Okubo, Toshiyuki

PNC TN9410 96-298, 177 Pages, 1996/11

PNC-TN9410-96-298.pdf:4.81MB

The fuel handling facility in "JOYO" must maintain an argon atmosphere and be gas tight; this prevents the oxidation of sodium adhering to a fuel assembly and leakage of radioactive gases. Periodic leak testing of the double O-ring gas seal had been performed at increasing pressure to assure its specified leak tightness. The problem with this method was that it took a long time to obtain an accurate measurement. The leak testing methods for the fuel handling facility, the reactor containment vessel, and other vessels were all reexamined. As a consequence, it was determined that alternative devices and methods for improving the leak rate measurements should be studied. Four methods of leak testing were evaluated; the present increasing pressure method, helium leak testing, decreasing pressure method, and a liquid nitrogen decreasing pressure method. A new automatic leak measurement device was used in these evaluations. The results of the utilization and limitations of the four methods of leak testing are summarized as follows. (1) The decreasing pressure leak testing method was efficient with regard to accuracy and stability for use in the fuel handling facility. (2) The automatic leak measurement device used a statistical calculation to measure the leak rate stability and it met the specified measurement requirements. (3) The leak rate measuring time was reduced by half with this new device and it could also simultaneously examine other objects.

Journal Articles

Construction of the HTTR and its testing program

Tanaka, Toshiyuki; Baba, Osamu; ; Shiozawa, Shusaku; Okubo, Minoru

10th Pacific Basin Nuclear Conf. (10-PBNC), 1, p.811 - 818, 1996/10

no abstracts in English

Journal Articles

Construction of the HTTR and its testing program

Tanaka, Toshiyuki; Baba, Osamu; Shiozawa, Shusaku; Okubo, Minoru;

JAERI-Conf 96-010, 0, p.97 - 104, 1996/07

no abstracts in English

JAEA Reports

Experimental fast reactor JOYO operational experience; The operational experiences of JOYO secondary sodium purification system

; Terano, Toshihiro; ; Onuki, Osamu; ; Okubo, Toshiyuki;

PNC TN9410 96-103, 88 Pages, 1996/03

PNC-TN9410-96-103.pdf:2.56MB

This paper describes operational experiences of JOYO Secondary Sodium Purification System which were obtained from April 1990 to March 1995. And, the operational problem of Secondary Sodium Purification System with MK-III core conversion were mentioned in this report. The experience results were as follows. (1)The number of cases of the secondary purification system trouble was 12. Those troubles, however, did not affect to the operation of the plant. (2)As the result of investigation about possibility of using secondary cold trap after MK-III core conversion, amount of trapped impurity was estimated 9.4kg as of January, 1994. In addition, 25.2kg was the estimated amount of trapped impurity at sodium initial purification after MK-III core conversion. It was subtantial excess of original design(18kg). (3)The change of heat transfer characteristics of secondary cold trap economizer occurred about two years after the modification of cold trap control tempereture. It seemed to be led by condition change of sticking impurity to heat transfer tubes which was followed by the modification of set up temperature. When set up temperature had been kept low, heat transfer characteristics was better. (4)A large quantity of sodium vapor was identified on the secondary argon gas system pressure control header. The influence of engulfing of argon gas at over flow line of Secondary Sodium Purification System is concerned.

Journal Articles

Design and present status of high-temperature engineering test reactor

Baba, Osamu; Kunitomi, Kazuhiko; Kawaji, Satoshi; Tanaka, Toshiyuki; Shiozawa, Shusaku; Okubo, Minoru

Proc. of ASME$$cdot$$JSME 4th Int. Conf. on Nuclear Engineering 1996 (ICONE-4), 2, p.281 - 287, 1996/00

no abstracts in English

JAEA Reports

None

; ; ; ; Onuki, Osamu; ; Okubo, Toshiyuki

PNC TN9440 95-014, 75 Pages, 1995/08

PNC-TN9440-95-014.pdf:1.93MB

None

JAEA Reports

Summary of countermeasures for reduction of radiation exposure from radioactive corrosion products(CPs) deposited on fuel cleaning system of "JOYO"

; Ito, Hideaki; Okubo, Toshiyuki;

PNC TN9410 95-105, 85 Pages, 1995/05

PNC-TN9410-95-105.pdf:3.86MB

Many subassemblies have been washed by water in the fuel cleaning system of JOYO, and a large amount of radioactive corrosion products(CPs) was removed from the surface of the subassemblies. These CPs deposited on the wall of piping and components in the system cause radiation exposure of personnel at operation and maintenance of the system. Following countermeasures for the reduction of radiation exposure have been conducted from 1991 to 1994. (1)ldentification of radiation source points by a Radiation image Display(RID). (2)Shielding of components in the system. (3)Rearrangment of water drain lines. (4)Replacement of water circulation piping. (5)lnstallation of a mist trap to the argon gas circulation line. (6)Installatlon of drain piping to valves of the argon gas circulation line. The dose rate in the fuel cleaning equipment room(A-212) was reduced to about one third after conducting the countermeasures. This report discribes the result of the countermeasures for the reduction of radiation exposure of personnel at operation and maintenance of the fuel cleaning system in "JOYO".

33 (Records 1-20 displayed on this page)