Development of high-pressure dry ice blasting method for decontamination (IV); Application test for barrel type dry ice blasting method

not registered; not registered ; not registered; Tanimoto, Kenichi

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.