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Yano, Yasuhide; Otsuka, Satoshi; Yamashita, Shinichiro; Ogawa, Ryuichiro; Sekine, Manabu; Endo, Toshiaki; Yamagata, Ichiro; Sekio, Yoshihiro; Tanno, Takashi; Uwaba, Tomoyuki; et al.
JAEA-Research 2013-030, 57 Pages, 2013/11
JAEA-Research-2013-030.pdf:48.2MB
It is necessary to develop the fast reactor core materials, which can achieve high-burnup operation improving safety and economical performance. Ferritic steels are expected to be good candidate core materials to achieve this objective because of their excellent void swelling resistance. Therefore, oxide dispersion strengthened (ODS) ferritic steel and 11Cr-ferritic/martensitic steel (PNC-FMS) have been respectively developed for cladding and wrapper tube materials in Japan Atomic Energy Agency. In this study, the effects of fast neutron irradiation on mechanical properties and microstructure of 9Cr-and 12Cr-ODS steel claddings for fast reactor were investigated. Specimens were irradiated in the experimental fast reactor Joyo using the CMIR-6 at temperatures between 420 and 835
C to fast neutron doses ranging from 16 to 33 dpa. The post-irradiation ring tensile tests were carried out at irradiation temperatures.
Yano, Yasuhide; Sato, Yutaka*; Sekio, Yoshihiro; Otsuka, Satoshi; Kaito, Takeji; Ogawa, Ryuichiro; Kokawa, Hiroyuki*
Journal of Nuclear Materials, 442(1-3), p.S524 - S528, 2013/09
Times Cited Count：14 Percentile：72.14(Materials Science, Multidisciplinary)Friction stir welding was applied to the wrapper tube materials, 11Cr-ferritic/martensitic steel, intended for fast reactors and defect-free welds were successfully produced. Then, the mechanical and microstructural properties of the friction stir welded steel were investigated. The hardness values of the stir zone were about 550 Hv, and they had hardly any dependence on the rotational speed, although they were much higher than that of the base material. However, tensile strengths and elongations of the stir zones were better at 298 K, compared to those of the base material. These excellent tensile properties were attributable to the fine grain formation during friction stir welding. A part of this study is the result of "Friction stir welding of the wrapper tube materials for Na fast reactors" carried out under the Strategic Promotion Program for Basic Nuclear Research by the Ministry of Education, Culture, Sports, Science and Technology of Japan.
Otsuka, Satoshi; Kaito, Takeji; Yano, Yasuhide; Yamashita, Shinichiro; Ogawa, Ryuichiro; Uwaba, Tomoyuki; Koyama, Shinichi; Tanaka, Kenya
Journal of Nuclear Science and Technology, 50(5), p.470 - 480, 2013/05
Times Cited Count：5 Percentile：38.62(Nuclear Science & Technology)Four experimental fuel assemblies (EFAs) containing 9Cr-ODS steel cladding fuel pins were previously irradiated in the BOR-60. One of the EFAs achieved the best data, a peak burn-up of 11.9at% and a neutron dose of 51 dpa, without any microstructure instability or any fuel pin rupture. On the other hand, in another EFA (peak burn-up, 10.5at%; peak neutron dose, 44 dpa), peculiar irradiation behaviors such as microstructure instability and fuel pin rupture occurred. The combined effects of matrix Cr heterogeneity (presence of metallic Cr inclusions) and high-temperature irradiation were concluded to be the main cause of the peculiar microstructure change of 9Cr-ODS steel cladding tubes in the BOR-60 irradiation tests. They contributed to the fuel pin rupture.
Kaito, Takeji; Otsuka, Satoshi; Yano, Yasuhide; Tanno, Takashi; Yamashita, Shinichiro; Ogawa, Ryuichiro; Tanaka, Kenya
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Safe Technologies and Sustainable Scenarios (FR-13) (USB Flash Drive), 11 Pages, 2013/03
The oxide dispersion strengthened (ODS) ferritic steel claddings developed by Japan Atomic Energy Agency were irradiated in Joyo and BOR-60 in order to confirm their irradiation performance and thus judge their applicability to high burnup and high temperature fast reactor fuels. In Joyo, material irradiation tests up to 33 dpa were carried out at in the temperature range of 693 - 1108 K. The irradiation data were obtained concerning mainly mechanical properties and of microstructure stability. In BOR-60, fuel pin irradiation tests were conducted up to burnup of 11.9 at% and neutron dose of 51 dpa. The irradiation data were obtained concerning fuel-cladding chemical interaction, dimensional stability under irradiation and so on. These results showed the superior irradiation performance of the ODS ferritic steel claddings and their application possibility as fast reactor fuels. This paper describes the evaluation of the obtained irradiation data of ODS ferritic steel claddings.
Yano, Yasuhide; Ogawa, Ryuichiro; Yamashita, Shinichiro; Otsuka, Satoshi; Kaito, Takeji; Akasaka, Naoaki; Inoue, Masaki; Yoshitake, Tsunemitsu; Tanaka, Kenya
Journal of Nuclear Materials, 419(1-3), p.305 - 309, 2011/12
Times Cited Count：20 Percentile：80.18(Materials Science, Multidisciplinary)The effects of fast neutron irradiation on ring tensile properties of oxide dispersion strengthened (ODS) steel claddings for fast reactor were investigated. Specimens were irradiated in the experimental fast reactor Joyo using the material irradiation rig at temperatures between 693 and 1108 K to fast neutron doses ranging from 16 to 33 dpa. The post-irradiation ring tensile tests were carried out at irradiation temperatures. The experimental results showed that there was no significant change in tensile strengths after neutron irradiation below 923 K, but the tensile strengths at neutron irradiation above 1023 K up to 33 dpa were decreased by about 20%. On the other hand, uniform elongation after irradiation was more than 2% at all irradiation conditions. The ring tensile properties of these ODS claddings remained excellent within these irradiation conditions compared with conventional 11Cr ferritic/martensitic steel (PNC-FMS) claddings.
Otsuka, Satoshi; Kaito, Takeji; Yano, Yasuhide; Yamashita, Shinichiro; Ogawa, Ryuichiro; Uwaba, Tomoyuki; Koyama, Shinichi; Tanaka, Kenya
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 6 Pages, 2011/12
This paper describes evaluation results of in-reactor integrity of 9Cr and 12Cr-ODS steel cladding tubes and the plan for reliability improvement in homogeneous tube production. A fuel assembly in the BOR-60 irradiation test including 9Cr and 12Cr-ODS fuel pins has achieved the highest burn-up, i.e. peak burn-up of 11.9at% and peak neutron dose of 51dpa, without any fuel pin rupture and microstructure instability. In another fuel assembly containing 9Cr and 12Cr-ODS steel fuel pins whose peak burn-up was 10.5at%, one 9Cr-ODS steel fuel pin failed near the upper end of the fuel column. A peculiar microstructure change occurred in the vicinity of the ruptured area. The primary cause of this fuel pin rupture and microstructure change was shown to be the presence of metallic Cr inclusions in the 9Cr-ODS steel tube, which had passed an ultrasonic inspection test for defects. In the next stage from 2011 to 2013, the fabrication technology of full pre-alloy 9Cr-ODS steel cladding tube will be developed.
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JNC TN9410 2001-029, 47 Pages, 2001/12
JNC-TN9410-2001-029.pdf:1.76MB
The decommissioning evaluation system that evaluated and optimizes the decommissioning scenario (total amount of men and days, period of works, exposure dose, abundance of waste, cost) has been developed. In this report, for test study of old JWTF decontamination using the decommissioning evaluation system, survey work of location and surface dose rate of machines and pipes in old JWTF, calculation using the decommissioning evaluation system, comparing a scenario carrying out a decontamination work and one which did not use the decontamination work were carried out. Results are as follows. (1)The DECMAN calculated that total amount of men and days was 4.5
10
man day, period of works was 490 days, cost was 3.910
yen, abundance of waste was 1.410
ton (radioactive waste was 6.9ton). (2)Total amount of men and days of a scenario using decontamination (scenario A) was nearly 1.3 times as large as one of a scenario which did not use decontamination (scenario B). Cost of "A" was 2.0 times as large as that of "B". Exposure dose of "A" was l/4 times as low as that of "B". (3)The DECMAN overestimated exposed dose. The reason was thought as follows. The exposed dose from each equipments was estimated in 2 dimension. Distance between each equipments in the DECMAN was estimated short compared with actual distance. Workers were moving around the equipment in actual work, and averted stopping at high dose rate points. The system could not add the process in calculation.
; Fukui, Yasutaka; ; Tanimoto, Kenichi
JNC TN9410 2001-028, 62 Pages, 2001/12
JNC-TN9410-2001-028.pdf:6.96MB
On irradiating laser ray to surface of metal, the surface is rapidly heated, melted, and evaporated. Laser decontamination technique has been developed by using the transpire process to radionuclides contaminated machine surface. The decontamination experiments using normal pulse YAG laser and hot sample were carried out. In the experiments, it was understood that even if the surface is ground by 150
m or more, radioactivities could not be completely removed. 0n this account, for the purpose of study the depth where a radioactivities merges in the metal by the laser irradiation, surveys using the hot test specimen were per拓rmed. Results are as follows. (1) Observation of topographic profile suggested that the depth of irregularity by laser irradiation were from 200m to 500m, and there were crud on the surface, which seems reattached melting crud by laser irradiation. (2) Metallic composition analysis with fluorescent X-ray analysis device suggested that there was the segregation of Cr in the test specimen that used Air for the assistance gas, and there were not the segregation that used Ar for the assistance gas. (3) The radioactivity analysis of the test specimen that uses the imaging plate and the radio autograph could not clear the distribution of radioactivities. However, it could be confirmed that a radioactive nuclide exited in a range of 500 m or less. (4) Grounding the test specimen and measurement of the doses of radiation with Ge measuring tool suggested that there were radioactivities up to the depth of 300m in the test specimen which used Air for the assistance gas, and 120m in the test specimen which used Ar for the assistance gas.
; Kondo, Hitoshi; Tanimoto, Kenichi
JNC TN9410 2001-012, 183 Pages, 2000/12
JNC-TN9410-2001-012.pdf:13.06MB
In operation of nuclear fuel cycle facility's decommissioning, it is necessary to decide the decommissioning plan based on 5 evaluation pointers, that is, number of men, period, exposure dose, abundance of waste, cost, and to control the project in proportion to ad hoc in the progress of the plan. The planning works have enormous counting and calculation operation. If you do the work in manual operation, it would be spend enormous labor. The system that evaluated and optimizes the decommissioning scenario has been developed. The system is called DECMAN (Decommissioning management system). DECMAN calculates the 5 evaluation points, which evaluates the decommissioning on the computer. The operator evaluates the decommissioning scenario and optimizes, taking the calculated evaluation index. DECMAN is composed of evaluation code, facilities information database. "G2" and "Oracle" are used for a base application. (1)DECMAN calculates the 5 evaluation points, that is number of men, periods, and exposure dose, abundance of waste, cost in each WBS, and totals the evaluation index all in the scenario. (2)The features of DECMAN are, by dividing the work of decommissioning work into WBS of the work minimum unit, and easily making the scenario by putting these WBS together in the set. This is the report-integrated result of DECMAN development.
; ; Kondo, Hitoshi; Tanimoto, Kenichi
JNC TN9410 2001-007, 105 Pages, 2000/12
JNC-TN9410-2001-007.pdf:7.42MB
Dismantling methods of liquid waste tanks lined with flammable natural rubber for decommissioning of Joyo Waste Treatment Facility. In this development, we researched common mechanical and heat cutting methods and chose appropriate one that was effective to decrease exposure and had no risk to fire the natural rubber lining. We next carried out dismantling tests using the chosen method with rubber lined mock-ups ofthe tanks to obtain cutting conditions and removal conditions of the lining to minimize secondary wastes. Results are follows. (1)We chose abrasive water jet that has an ablity to remove the rubber lining and to be controllable remotely with ease as a cutting method for the natural rubber lined tanks. (2)As a result of cutting tests under parameters of a cutting nozzle speed and a abrasive feed rate, cutting conditions minimizing secondary wastes are 0.4 kg/min abrasive feed rate and 300 mm/min nozzle speed. (3)As a result of a removing test under a parameter of a removing nozzle speed, a removing condition minimizing secondary wastes is 60 mm/min nozzle speed, thus removing speed is 3720 mm/min. (4)Improving the removing method, especially decreasing water feed, and general design of a dismantling system including treatment with secondly waste are required.
Fukui, Yasutaka; ; Kondo, Hitoshi; Tanimoto, Kenichi
JNC TN9410 2000-015, 83 Pages, 2000/09
JNC-TN9410-2000-015.pdf:3.06MB
By irradiating the material surface with the laser beam, it is possible that the surface is rapidly heated, melted and transpired. Laser decontamination technique which applies this process to the removal of the material surface layer contaminated in the radionuclide has been developed. In this report, factual waste laser decontamination experiment using the piping of the old Joyo Waste Treatment Facility was carried out for the purpose of applying laser decontamination technique to decommissioning of nuclear fuel cycle facility. And, secondary product splash prevention test of a normal pulse YAG laser was carried out. Main results are as follows. (1)Factual wast decontamination test It is necessary to decontaminate with the aim of 0.15mm removal depth in order to obtain the decontamination effect to B.G.level, when the pollution piping is decontaminated using a normal pulse YAG laser. Conditions for efficiently obtaining 0.15mm removal depth and l.3kJ/cm irradiation energy density in the irradiation of 2 times with 364W oscillator are 30Hz frequency, duty ratio 50 % in irradiation energy density 1.3kJ/cm, and test piece mobile speed 30mm/s. (2)The splash prevention of the secondary product test For the purpose of the splash prevention of the secondary product, the small hood for splash prevention installed in the decontamination nozzle was made. As a result of the test, the following were confirmed : That it does not scatter for the high position almost, though it horizontally scatters in the wide angle, and that the part of the secondary product scatters in the hood outside by reflecting in the hood. It is necessary to make the hood with wedged structure and attraction mechanism for the purpose of shatter-resistant of secandary products.
; ; 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 70C. 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.
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 0.1m. 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.
