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; ; Tanimoto, Kenichi
JNC TN9410 99-022, 208 Pages, 1999/09
An estimation for decommissioning of JWTF old structure using decommissioning management system was done to confirm "work term", "work qugntity", "exposure dose", "quantity of radioactive waste", and "cost". Two different decommissioning methods are used in the estimation work. The two methods are as follows. (a)Method A: Cutting work is done in the spot of equipments, waste occurred in the cutting work are stored in a waste container, and the waste is keep in a waste storage place. (b)Method B: In cutting work, equipments are dismantled to container size in the spot of decommissioning place, and also are dismantled in more small size in exclusive waste treatment facility, and are kept in the exclusive store place. The simulation named method B was ended before the waste was bought in the exclusive waste treatment facility, because we have not had the waste treatment facility. Those results are shown in the following. (1)Work term: 732days using the method A, and 517days using the method B. (2)Work quantity: 10,023 man*days using the method , and 6,931 man*days using the method B. (3)Exposure dose: 61,967 man*mSv using the method A, and 37,606 man*mSv using the method B. (4)Quantity of radioactive waste: 69,112kg using the method A, and 68,929kg using the method B. (5)Cost: 696,553 thousand yen using the method A, and 442,533 thousand yen using the method B.
; ; Tanimoto, Kenichi
JNC TN9410 99-019, 57 Pages, 1999/09
The sheet having both the incinerability and the sealability has been developed to decrease an amount of radioactive waste. As results of some experiments, ethylene vinyl acetate copolymer (ECO) was chosen. The material had also an advantage that corrosive gas was not occurred at destruction by fire. However, ECO sheet is inferior to PVC sheet on the point of tensile strength on high temperature environment and transparency. To improve these problems, heat-treating sheet (surface of ECO sheet was treated by heating) was made on an experimental basis. Properties of the trail sheet were examined. Properties of the ECO sheet and the PVC sheet were also examined for putting to practical use. Results of the examine are as following. (1)Properties of heat-treating sheet; The parallel ray penetration of the heat-treating sheet was 6 times better than that of ECO sheet. Other properties of the heat-treating sheet were much the same as ECO sheet. (2)Properties of ECO sheet; Tensile strength of ECO sheet was isotropy (longitudinal direction and sidelong direction). ECO sheet dissolved in xylene and tetrachloroethylene. Softening temperature of ECO sheet were about 70
C. That of PVC sheet was 144C. (3)Properties of PVC sheet; Tensile strength in sidelong direction was 85% the value of longitudinal direction. Tensile strength and the elongation rate were 85 and 40% the value of ECO sheet in low and normal temperature. Tensile strength in high temperature was 55% the value of normal temperature. Temperature dependency of PVC sheet's tensile strength was lower than that of ECO sheet. Gas penetration coefficient was lower than that of ECO sheet.
; ; Tanimoto, Kenichi
JNC TN9410 99-017, 117 Pages, 1999/08
Decontamination methods have been studied for decommissioning of Joyo Waste Treatment Facility whose operation has been stopped in 1994. In this study, we analyzed samples of its system piping, whose dose rate was relatively low, to determine conditions of contamination. We also study appropriate decontamination methods for them. Results are as follows. (1)The inner surfaces of piping were covered with a very thin clad that was less than 1 micrometer in thickness and had many vacancies, looked like particle detachment, that were about 20 micrometers in depth. Something like corrosion product was observed near the surface and it was 440 micrometers in depth. (2)Radioactive contamination was considered to settle on a lower part of the piping and to be buried in the clad. A kind of dominant contamination nuclide was 
Co. (3)Hot nitric acid process will be suitable for system decontamination to reduce dose rate before dismantling. But its feasibility tests are indispensable using samples of main system components that have high dose rate. Rubber lining tanks requires another methods because of its difficulty of decontamination. (4)Analyses and decontamination tests using main system are required to decide through decontamination methods according to the clearance level.
Fukui, Yasutaka; ; ; Tanimoto, Kenichi
JNC TN9410 99-016, 77 Pages, 1999/08
Process of laser decontamination system is as follows. As the material is irradiated by laser beam, its surface is instantaneously heated and ablated. Laser decontamination system is able to decontaminate thoroughly. In this work, the characteristics of laser beam transmission by optical fibers, and decontamination effect of laser beam irradiation to test pieces which are cut down of pipe in the hot facility, are experimented for apply laser decontamination technique to radioactive wastes treatment and decommissioning of nuclear fuel facilities. The results are as follows. (1)Beam transmission. Transmission of Q switch pulse YAG laser's beam by optical fibers are examined. Transmission energy is in proportion to incident energy to fiber. Transmission energy of bundled fiber is 168mJ to 406mJ of incident energy. In the case of incident energy was 425mJ, transmission energy was decrease, because some fibers of bundled fiber were damaged by laser beam. (2)Decontamination test of the hot samples. Counting rate of pipe test piece were decreased more than 90% by first irradiation of Q switch pulse YAG laser. Counting rate of pipe test piece were decreased no more than 4% by on and after second irradiation of Q switch pulse YAG laser. To move the test piece slowly, and to raise the density of irradiation energy, and to use the helium gas for auxiliary gas are effective to increase decontamination effect.
Fukui, Yasutaka; ; ; Tanimoto, Kenichi
JNC TN9410 99-014, 99 Pages, 1999/07
In this work, the characteristics of laser beam transmission by optica1 fibers and decontamination speed by the most suitable condition and improvement of the characteristics of secondary products are experimented for apply laser decontamination technique to radioactive wastes treatment and deco㎜issioning of nuclear fuel facilities. The results are as follows. (1)Beam transmission. For Q switch pulse YAG laser, beam transmission by optical fibers were examined. Transmission energy increase in proportion to diameter of fiber. The maximum transmission energy of optical fiber was 61mJ, which was not damaged. The transmission energy of bundle fiber was more plenty than the energy of single fibers at same numbers. It is able to apply bundle fiber to transmission system of Q switch pulse YAG laser beam. (2)Improvement of decontamination speed. Imitation contaminants were removed perfectly on the condition that, the irradiation frequency was 2 times, move speed of test piece was 3.0mm/sec, beam diameter was 1.2㎜, repetition speed was 10Hz. At this time, the number of beam shots were more 4 in the unit area. The case of fluence is constant, the number of beam shots were increased by spread of beam diameter in the unit area. (3)Measurement of secondary products. Particle diameters of more than 50% secondary products by Q switch pulse YAG laser were less than 0.1
m. Particle diameters of more than 50% secondary products by normal pulse YAG laser were from 0.1m to 1m.
Fukui, Yasutaka; ; ; Tanimoto, Kenichi
JNC TN9410 99-008, 157 Pages, 1999/04
Laser decontamination system is able to decontaminate thoroughly, and it is able to mitigate the secondary waste quantity, and the system is able to operate by remote control. It is advantageously method compared with other decontamination methods. Irradiation by YAG laser beam is competent for decontamination of stainless steel surface. In this paper, using normal and Q switch pulse YAG laser, Experiments to confirm transmission efficiency using mirror and optical fiber, shape dependency at decontamination, and secondary waste size distribution were performed. The results of the work are as follows. (1) The beam energy of normal pulse YAG laser is able to transmit using optical fiber. The beam energy of Q switch pulse YAG laser is difficult to transmit using a single optical fiber. (2) Normal pulse YAG laser has 10
Decontamination Factor (DF) on L-shaped, bolt-shaped, and cylindrical-shaped waste. Q switch pulse YAG laser has over 10 DF on L-shaped and cylindrical-shaped waste, but on the other hand, under 10 DF on bolt-shaped waste. (3) In the case of using the argon gas as auxiliary gas, almost particles of secondary products are dropped as dross. In the case, scattering area is within 1m. On the other hand, in the case of using the atmosphere gas as auxiliary gas, almost particles of secondary products are floated in the air, its diameter are under 3m.
; ; Tanimoto, Kenichi
JNC TN9410 99-007, 117 Pages, 1999/04
In making a plan of decommissioning of nuclear fuel facilities, it is important to optimize the plan on the standpoint of a few viewpoints, that is, the amount of working days, workers, radioactive waste, exposure dose of worker, and cost (they are called evaluation indexes). In the midst of decommissioning, the decommissioning plan would be modified suitably to optimize the evaluation indexes adjusting to progress of the decommissioning. The decommissioning management code (DECMAN), that is support system on computer, has been developed to assist the decommissioning planning. The system calculates the evaluation indexes quantitatively. The system consists of three fundamental codes, facility information database code, technical know-how database code and index evaluation code, they are composed using "Oracle" database and "G2" expert system. The functions of the system are as follows. (1)Fcility information database code Information of decommissioning facility and its rooms, machines and pipes in the code. (2)Technical know-how database code. Technical information of tools to use in decommissioning work, cutting, dose measure, and decontamination are there. (3)Index evaluation code. User build decommissioning program using above two database codes. The code evaluates five indexes, the amount of working days, workers, radioactive waste, exposure dose of worker, and cost, on planning decommissioning program. Results of calculation are shown in table, chart, and etc.
; ; ; Tanimoto, Kenichi
JNC TN9410 99-006, 74 Pages, 1999/04
To decontaminate radioactive waste occurred in nuclear fuel facilities to minimize radiation dose level of the waste, electro-polishing method have been developed in JNC. In this paper, many experiments were performed to get data that were necessary to design electro-polishing equipment. Results of the examinations are as follows. (1)Distance between an electrode and flat board test piece was varied from 10 to 100 mm, electric current density was 0.2A/cm, and executing time was 20 minute. In above case, we measured polishing weight of both sides of the test piece to clear polishing distribution in waste surface. The longer the distance between two electrodes, the nearer weight of reverse side became to front side. In the case, best distance between the test piece with electrode is 100mm. (2)Using flat board, angle, pipe, and bolt, shape dependence test was performed. Over 10min. , all the test piece with any shape got a thickness of 10m or more. (3)The electro-polishing equipment ran 85 hour in our experiments. Because remarkable change was appeared in polishing weight and injection voltage over 50 hour, life time of electrolytic solution was 50 hour.
; ; ; Tanimoto, Kenichi
PNC TN9410 97-071, 69 Pages, 1997/07
In order to decrease radioactivity of high-level radioactive wastes to low-level (lower than 500 Sv/h), the dry-ice blasting method has been developing. This method can decontaminate radioactive wastes up to 10 in decontamination factor, and can minimize the secondary generated wastes. The barrel type method can decontaminate smaller solid wastes with preventing the scattering of the wastes due to blast pressure. In this work, application test was conducted to improve the decontamination capability of the barrel type method, with using the improved barrel device. Results are as follows. (1)Stirring ability of the barrel device was improved by installing plates in the barrel. Four plates with 10mm in height were better for optimal stirring. (2)Reciprocating of the blasting nozzle stabilized decontamination capability of the barrel device. Forty per a minute in reciprocation rate of the nozzle was better. (3)Decontamination capability was examined with using test pieces coated with the cesium molybdate, which was simulating the typical contamination of radioactive waste. As a result, 80% of contamination was removed by the optimized barrel type method. (4)Dust collector was frozen within a few minutes, and exhaust flow rate was decreased by about 15%. However, by exhausting room temperature air, dust collector was unfrozen, and the flow rate could be recovered. (5)Decontamination capabilities of two types of dry ice pellets were compared. They were made by an oil hydraulic pressing or a roller pressing. Former pellet was three times as capable as latter one.
; ; ; Tanimoto, Kenichi
PNC TN9410 97-061, 73 Pages, 1997/05
In order to decrease radioactivity of high-level radioactive wastes to low-level (lower than 500 Sv/h), the dry-ice blasting method has been developing. This method can decontaminate radioactive wastes up to 10 in decontamination factor, and can minimize the secondary generated wastes. However, the method was not applicable to smaller and lighter objects because the objects scatter with the blasting flow. Two types of decontamination method, which are a barrel type- and a vacuum type- dry ice blasting methods, therefore, were planned. The barrel type method can decontaminate smaller solid wastes with preventing the scattering of the wastes by blast pressure. The vacuum type method has advantages to localize and collect the removed contamination from larger wastes. In this work, their basic efficiency on decontamination were investigated experimentally using painted specimens simulating contaminated wastes. Results are as follows. (1)In the experiment on the barrel type method, distance between blast nozzle and specimens, blast pressure, blast duration and rotational speed of barrel were changed within a range of 70
250 mm, 715kgf/cm, 90300 second and 530 r.p.m. respectively. Decontamination efficiencies were determined with measuring differential weight of specimens between before and after the experiment. As the result, it was clarified that the suitable distance was 150mm, that the efficiency wasn't improved in the pressure more than 10kg/cm, that the rotational speed was not so dominant, and that the dominant parameter on the efficiency was the duration. The decontamination efficiency rose up with the duration within 300 sec. (2)In the experiment on the vacuum type method, blast pressure and blast duration were changed within a range of 46kgf/cm, and 60180 second, respectively. Top of a vacuum cover was also opened or closed. Decontamination efficiencies were determined with measuring area of ...
Sasajima, Hideo; Fuketa, Toyoshi; *; Ishijima, Kiyomi; ; Yamahara, Takeshi; ; Ito, Tadaharu
JAERI-Research 95-087, 179 Pages, 1995/12
JAERI-Research-95-087.pdf:12.06MB
no abstracts in English
Nakamura, Takehiko; ; Ishijima, Kiyomi; ; Yamahara, Takeshi; ; Ito, Tadaharu
JAERI-Research 95-080, 92 Pages, 1995/11
JAERI-Research-95-080.pdf:8.22MB
no abstracts in English
Fuketa, Toyoshi; Sasajima, Hideo; *; *; Tanzawa, Sadamitsu; Ishijima, Kiyomi; ; ;
JAERI-Research 95-078, 194 Pages, 1995/11
JAERI-Research-95-078.pdf:17.91MB
no abstracts in English
Fuketa, Toyoshi; *; Sasajima, Hideo; *; Tanzawa, Sadamitsu; Ishijima, Kiyomi; ; Kikuchi, Teruo;
JAERI-Research 95-013, 230 Pages, 1995/03
JAERI-Research-95-013.pdf:24.22MB
no abstracts in English
Fuketa, Toyoshi; Ishijima, Kiyomi; Tanzawa, Sadamitsu; Nakamura, Takehiko; Sasajima, Hideo; Kashima, Yoichi; ;
JAERI-Research 95-005, 53 Pages, 1995/01
JAERI-Research-95-005.pdf:1.96MB
no abstracts in English
Katanishi, Shoji; Ishijima, Kiyomi; ; Kikuchi, Teruo;
JAERI-Research 94-039, 54 Pages, 1994/11
JAERI-Research-94-039.pdf:5.2MB
no abstracts in English
Fuketa, Toyoshi; Sasajima, Hideo; *; *; Tanzawa, Sadamitsu; Ishijima, Kiyomi; ; ; Kikuchi, Teruo;
JAERI-Research 94-006, 96 Pages, 1994/07
JAERI-Research-94-006.pdf:6.19MB
no abstracts in English
Nakamura, Takehiko; ; Sobajima, Makoto; Ishijima, Kiyomi; ; Yamahara, Takeshi; ; Kikuchi, Teruo
JAERI-M 94-030, 103 Pages, 1994/03
no abstracts in English