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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 ...
Ichijo, Tsubasa; Nakayama, Kazuhiko; Seshimo, Kazuyoshi; Kojima, Kazuki; Sakurai, Momoka
no journal, ,
no abstracts in English
