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; ; Matsumoto, Yoshihiro; ; Kato, Noriyoshi; Miyazaki, Hitoshi; Tanimoto, Kenichi
JNC TN9410 2002-010, 62 Pages, 2002/11
JNC-TN9410-2002-010.pdf:2.37MB
The vaporizer in extinguishing of Large Equipment Dismantling Facility (LEDF)that cost is considering as a plan to cut down as part of a rationalization design highly. When the vaporizer is deleted, it becomes here where liquefied carbon dioxide is emitted in the direct cell, it is necessary to grasp the action and extinguishing performance of the pressure change in the cell by rapid evaporation test of the emitted liquefied carbon dioxide. So pressure action inside the fire laboratory in liquefied carbon dioxide release and a putting out the fire tests due to the combustion time of the combustible were enforced by using the general fire laboratory with Demonstration Test on Extinguishing of the cell (I) in the llth year of Heisei. However, since these tests are after laboratory without airtightness, it needs to grasp the pressure action at the time of liquefied carbon dioxide discharge under the airtight high conditions of having assumed the still more nearly actual cell. The cell (II) Demonstration Test on Extinguishing using the vessel of Sodium Leak Fire and Aerosol test rig (SOLFA-2) container inside of OEC was carried out. The results were as follows. (1)In order to grasp the pressure action of the vessel, the internal pressure of SOLFA-2 was set as -50mmH
O, and emitted liquefied carbon dioxide. Consequently, the tendency for the pressure in the vessel to descend rapidly immediately after liquefied carbon dioxide discharge, and to descend gently-sloping through the process which goes up gradually after that and goes abruptly up for a short time was seen. (2)The process which goes abruptly up in an above-mentioned short time is considered to be the factors with main what some liquefied carbon dioxide emitted in the vessel changed to dry ice, and was deposited taken and sublimating surrounding heat, and evaporating again. (3)It sets to total flooding system and the average minimum temperature in the vessel becomes about -48
C, and at ...
; Matsumoto, Yoshihiro; ; ; Kato, Noriyoshi; Miyazaki, Hitoshi; Tanimoto, Kenichi
JNC TN9410 2002-008, 68 Pages, 2002/07
JNC-TN9410-2002-008.pdf:2.89MB
In order to rationalize for Large Equipment Dismantling Facility (LEDF), the plan of removing vaporizer belong to Cell-fire-extinguishing-system was investigated. When a vaporizer is cut down, It is necessary to grasp a fire-extinguishing performance. The fire-extinguishing performance check examination by liquefaction carbon dioxide in the cell fire-extinguishing examination (I) was carried out in 1999 fiscal year. As the result, The good performance was obtained to polyethylene. But there was the deep-seated fire about a piece of wood. Then, The check items were carbon dioxide (CO) concentration and CO concentration holding time for the deep-seated fire in the cell fire-extinguishing examination (III). The results were as follows; (1)By use of the combustion model in which a piece of wood and cotton were put is lit, temperature inside model, mass reduction, and combustion situation were examined. The model burned remarkably in 30
60 min. The peak temperature rise to 680 C(MAX), and attained smoldering after (ignition) 70 min. Moreover, in order to determine the generating conditions of a deep-seated fire, the situation of CO extinguishing after ignition by the time lag of 5090 min were examined. The model around ignition 50 minutes was the most difficult to extinguish, and it turned out that they are the conditions which were most suitable for the deep-seated fire examination model of an exam. (2)In order to decide on CO concentration and concentration holding time required for fire extinguishing of the deep-seated fire in LEDF, The fire-extinguishing performance was investigated by 40 65% of CO concentration. Consequently, CO concentration required for deep-seated fire extinguishing was understood that 60% or more was required when safety was taken into consideration at 50% or more. Moreover, when it was 50% or more of CO concentration and the holding time of CO concentration ...
; ; ; Kato, Noriyoshi; Miyazaki, Hitoshi; Tanimoto, Kenichi
JNC TN9410 2002-006, 49 Pages, 2002/07
JNC-TN9410-2002-006.pdf:1.84MB
Construction of LEDF (Large Equipment Dismantling Facility) is being planned by Waste Management Section. This purpose of LEDF is the melting treatment of the radioactive waste in OEC (O-arai Engineering Center) and the waste package in JAERI (O-arai Japan Atomic Energy Research Institute). It is also considered about the disposal plan of the future. Therefore LEDF has the sorting process of waste because of the removal of problematic substances. But that process is conducted using its human eyes. This process needs automatic operation because of high classification accuracy, high reliability, burden reduction of a worker. Then we select EXFS (Energy dispersive X-ray Fluorescence Spectrometer), and conducted the measurement of waste (a sample) with this device. That purpose is to confirm an application as the sorting device. A confirmation result is shown in the following. (1)Sorting performance Measurement is possible without pretreatment, if it is metal. However, sorting is difficult when paint, plating, impurities, etc. are shown in the surface. (2)Measurement position It is necessary to set a gap of the measurement thing from a measurement position to 4㎜ or less. (3)Radiation influence Because the background had risen by the influence of a radiant ray, the distinction of Fluorescence X-ray became difficult. Therefore the distinction of materials became impossible. Aluminum is influenced specially by it. As a conclusion, the application nature of EXFS thing Sorting System is high. But there is a bad influence by radiation. Therefore, difficult is installation into the cell. In order to apply EXFS to LEDF, it is necessary to place it outside the cell and to use as the help of the visual inspection.
Donomae, Yasushi; Matsumoto, Yoshihiro; Kikuchi, Yutaka; Kato, Noriyoshi; Miyazaki, Hitoshi; Tanimoto, Kenichi
JNC TN9410 2001-021, 73 Pages, 2002/01
JNC-TN9410-2001-021.pdf:3.91MB
In order to rationalize for Large Equipment Dismantling Facility (LEDF), the plan of removing vaporizer belong to Cell-fire-extinguishing-system was investigated. In this test, in order to study the behavior of pressure in cell, when the liquefaction carbon dioxide (liq-CO) is emitted, and the performanee of extinguishing fires, the test of behavior of pressure and the extinguishing fires take effect. Also the extinguishing fires test used water-mist take effect for complement liq-CO. The results as follows; (1)In the test of behavior of pressure, Liq-CO was emitted test room under -40mmAq negative pressure. Room pressure was increase about 0.8mmAq/sec at first. After 29sec, the pressure was increase slowly about 0.1mmAq/sec. After 120sec, the increase was drastic about 1.5mmAq/s. (2)In the test of extinguishing fires by liq-CO, under -40mmAq, Polyethylene and wooden chips + cotton (crib) was burn. Polyethylene was extinguished perfectly, but the embers remained in cribs. While the room pressure was increase about 1.3mmAq/sec for 10sec at first. After 30 sec, the pressure was increase about 1mmAq/sec. On the other hand, the drastic increase of pressure disappeared between 100sec to 120sec by change the nozzle size from 14mm
to 10mm. (3)In the test of extinguishing fires by water-mist, Cribs was extinguished perfectly, but Polyethylene was extinguished difficulty under the same condition of liq-CO test. (4)Therefore the results, It's coped with the fire extinguishing and the keeping negative pressure for LEDF cells. Therefore nozzle size is fitted cell volume as changing 14mm to 10mm. (5)As the performance of extinguishing fires by liq-CO, It is necessity the concentration of above 50% CO for combustibles as cribs, remaining the embers. (6)On the other hand, It is necessity most study for the adoption of water-mist. Therefore water-mist was not effective for polyethylene, and it needed water ...
; 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.
; ; Tanimoto, Kenichi; Kondo, Hitoshi; Hazama, Taira;
JNC TN9410 2001-027, 136 Pages, 2001/12
Deuterium Critical Assembly (DCA) is a critical facility with 1 kW maximum themmal output used for development of an Advanced Thermal Reactor and a subcriticality measurement technique for criticality safety management of nuclear fuel facilities since its initial criticality in 1969. DCA operations were stopped on 26
September 2001, then it has been planed to submit a legal application for decommissioning of DCA and to shift to decommissioning phase. In this work, we have evaluated an amount of materials in all controlled areas, activated inventories and activated radioactive wastes to make a document on estimation of the inventories and the wastes et.al. in the legal application. Results are as follows. (1)Total amounts of materials in the controlled areas are 9,464 tons. An amount of concrete is 9,162 tons and greater than 97% of all materials in weight. (2)The radioactive inventories of metals et.al and a biological shield will be respectively l.39
10
Bq and 4.9010
Bq in about 2008 when actual dismantling of components will be started. (3)We classified decommissioning materials according to clearance level that has been discussed to be legalized. An amount of low level radioactive wastes will be 36 tons. Amounts of clearanced or nonradioactive waste will be 9,428 ton and greater than 99% of all wastes in weight. 7,005 tons of concrete will be nonradioactive waste.
; Kondo, Hitoshi; ; Tanimoto, Kenichi
JNC TN9410 2001-011, 124 Pages, 2001/12
JNC-TN9410-2001-011.pdf:6.73MB
Deuterium Critical Assembly (DCA) is a critica facility with 1 kW maximum thermal output used for development of an Advanced Thermal Reactor and a subcriticality measurement technique for criticality safety management of nuclear fuel facilities since its initial criticality in 1969. It has been planed to stop DCA operation in 2001 and shift to decommissioning phase. In this study, we evaluated activated inventories being primary data for study of an amount of radioactive wastes, dismantling method and cost which are indispensable for a decommissioning plan and a draft of a legal application for decommissioning. The evaluation was carried out for components in Reactor room and a DO handling room irradiated with neutron flux. Results are as follows. (1)Each amounts of components and a building related with Reactor room and D2O handling room are 108 tons and 6,039 tons respectively. They are classified into 28 tons of aluminum, 37 tons of stainless steel, 73 tons of carbon steel, 6,004 tons of concrete and 5 tons of the others. (2)The activated inventories are very little due to a low neutron flux in DCA. Thus, radioactive materials concentrations in most of matelials except 37 tons of stainless steel and 12 tons of carbon steel will be lower than that of proposed clearance level in 7 years after the end of operation. The inventories of the components and the shield will be respectively 4.2510Bq and l.7110
Bq.
; Kato, Noriyoshi; Miyazaki, Hitoshi; Tanimoto, Kenichi
JNC TN9410 2001-018, 114 Pages, 2001/09
JNC-TN9410-2001-018.pdf:12.35MB
Construction of LEDF (Large equipment dismantling facility) which has the in-can type incineration-melting furnace is planned. The in-can type incineration-melting furnace performs incineration and melting solidification of radioactive waste within the canister made from ceramics, and is characterized by discarding the canister. On the other hand, as for this furnace, the amount of incineration is restrained to canister capacity, Therefore, how to repeat incineration and melting can be considered as a method of increasing the amount of incineration. However, we were anxious about the contact time of the melt and a canister extending, the amount of wear of canister base material increasing, or the heat load (heat cycle) to a canister increasing, and the material intensity of canister base material falling, in order that this method may repeat incineration and melting. then, the tests used imitation waste, are the conditions which repeat (1,3, 10 bathes) the incineration temperature of 1000 C, and the melt temperature of 1500 C, and investigated change of the amount of wear of canister base material and high temperature bend strength. The result is as follows. (1) The amount of wear of canister base material was 0.09 mm/h at the maximum. This result was a sufficiently few value, even if compared with the conventional result (1.0 mm/h). Moreover, the high temperature bend strength of canister base material is about 3 Mpa on an average, and change was seen before and after the examination to which heat load is applied. (2) These tests showed that the factor which spoils the soundness of a canister was oxidization degradation of the canister base material by peeling from the base material of Glaze (glass coating material). The portion embrittlement by oxidization degradation is locally worn down by contact of the melt. (3)Heat-resistant temperature of Glaze is about 1300 C. At the melting operation temperature of 1500 C, and ...
; 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.
Kondo, Hitoshi; ; Namekawa, Takashi; ; Miyazaki, Hitoshi; Tanimoto, Kenichi
JNC TN9410 2001-006, 43 Pages, 2000/12
JNC-TN9410-2001-006.pdf:1.49MB
In order to make a contribution to the clearance level decision work of the research facility which handle radioisotope (RI), fuel and so on, the amount of waste from decommissioning the facility was investigated. The investigation were the estimation of the amount of decommissioning waste and the evaluation of the amount of clearance level waste for four facilities which are Fuel Monitorring Facility (FMF), Alpha-Gamma Facility (AGF), Materials Monitoring Facility (MMF), and Waste Dismantling Facility (WDF). The result of estimation and valuation are as follows. (1)The amount of the decommissioning waste for FMF is about 71500 tons. (Concrete is about 67500 tons, metal is about 3,600 tons, and others is about 300 tons.) (2)The amount of the decommissioning waste for AGF is about 14200 tons. (Concrete is about 13300 tons, metal is about 600 tons, and others is about 200 tons.) (3)The amount of the decommissioning waste for MMF is about 18000 tons. (Concrete is about 17100 tons, metal is about 700 tons, and others is about 100 tons.) (4)The amount of the decommissioning waste for WDF is about 28600 tons. (Concrete is about 27900 tons, metal is about 700 tons, and others is about 20 tons.) (5)All concrete waste and over 70% of metal waste is included the clearance level or non-radioactive waste. (6)By excluding a waste under the clearance level from a disassembly waste, the radioactive waste for the decommissioning the facility can be drastically reduced.
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.
; ; Kato, Noriyoshi; Miyazaki, Hitoshi; Tanimoto, Kenichi
JNC TN9410 2000-002, 149 Pages, 1999/12
JNC-TN9410-2000-002.pdf:23.51MB
LEDF (Large Equipment Dismantling Facility) is the solid waste processing technology development facility that carries out high-volume reduction and low dosage processing. The high-volume reduction processing of the high dose 
-waste configured with combustible waste, pvc & rubber, spent ion exchange resin, and noncombustible waste have been planned the incinerating and melting facility using the in-can type high frequency induction heating in LEDF. This test is intended to clarify the design data. It was confirmed that the incinerating and melting performance, molten solid properties and exhaust gas processing performance with pilot testing equipment and bench scale equipment. The result of this test are as follows. (1)Processing speed is 6.7kg/h for the combustible waste, 13.0kg/h for the ion exchange resin, and 30.0kg/h for the noncombustible waste. For above optimum processing conditions are as follows. (a)Operating temperature is 1000C for the combustible waste, 1300C for the ion exchange resin, 1500C for the noncombustible waste. (b)Air flow is 90Nm
/h. Air temperature is 300C. Air velocity is 20m/s. (2)Incineration time per day is 5h. Warm-up time and incineration time from the stop of waste charging is 0.5h. Melting time per day is 5h inconsideration of heating hold time of incinerated ash and melting of quartz. Warm-up time is 0.5h. (3)The system decontamination factor in Co, Cs and Ce with pilot testing equipment is 10
or more. (4)Design data of the iron doped silica gel judged to be have a applicability as RuO
gas absorber is as follows. (a)Its diameter distribute in the range of 0.8-1.7mm. (b)To have a decontamination factor of 10 can achieve for retention time of 3 seconds and its life time is about 1 year. (5)In terms of the distribution of the nuclear species in molten solid is evenly distributed. It was also confirmed that the distribution of main elements in ceramic layer is ...
; ; 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.
; ; 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 0.1m. 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.