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; ; ; 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 ...
Fukui, Yasutaka; ; Tanimoto, Kenichi; Terunuma, Seiichi
PNC TN9410 94-033, 86 Pages, 1994/01
It is must deceasse the pool risk for the radio active wastes. So it is necessary to decontaminate the wastes low level 
(
500Sv/h) during control the secendry wastes. Exfoliation velocity (aria of exfoliated paint per unit time) was measured on various cndition changed parameter brasting pressure, feed rate, stand off distance between nozzle and waste surface, angle of nozzle, therefore most suitable condition for decontamination was decide on high-pressure ice brasting method, results are as follows. (1)Feeding dry-ice pellets of most suitable condition was decided on that brasting pressure is 15Kgf/cm, feed rate is 30%. Same exfolation ability was gained on condition that brasting pressure is 15Kgf/cm, feed rate is 50%. (2)Brasting dry-ice flow of most suitable condition was dicided on that stand off distance is between 50㎜ and 100㎜ angle of nozzle is 30
with vertical. (3)In case of a pipe form, exfolation ability was gained on condition that angle of nozzle is 60 with vertical after the waste was settled on the turn-table and turning. In case of angle iron form, on condition that angle of nozzle was 0 or 60 with vertical. In case of inner can on condition that angle of nozzle was 45 with axis. When these were such small parts as bolts in the barrel basket which leand 30 with vertical and turned 120rpm, exfolation ability was gained on condition that angle of nozzle was vertical. (4)In decontamination hood designing, negative pressure was maintaind in the cell, and freeze preventing heat capacity of ventilation filter (-78C) was calculated at 73kw.
; ; ; Tanimoto, Kenichi; Enokido, Yuji
PNC TN9410 93-053, 99 Pages, 1993/03
It is must deceasse the pool risk for the radio active wastes. So it is necessary to decontaminate the wastes low level (500Sv/h) during control the secendry wastes. Had been product the decontaminations hood system for scattaring proof. For that, high-pressure ice brasting method tested using the system. The number of the test piece was 12 from MMF. The resultes is as follows; (1)The hood system have good capacity for scattering proof and remort handling. (2)Aa the test condition, the pressure and the flux was used 9kgf/cm and 6m
/min, feed volume was used 2kg/min. From the results, the number of test piece being low level (500Sv/H) was 7, containing of ten several mSv/h wastes, from among. The lesves could not decontaminate. (3)The contamination in the hood was decreased from 87mSv/h to 3mSv/h by nomal pressuer icebrasting (the pressure is 4kgf/cm, 2m/min, the feed volume is 1 kg/min).
