Speaker
Description
Recently, many cyclotrons used for the production of [F-18] FDG in Korea is in the phase of dismantling. While many studies, such as the assessment of activation levels, have been conducted for cyclotron decommissioning, the research on survey-based clearance method has not been carried out domestically. Therefore, this study aims to discuss the feasibility of developing a survey-based method for Yoke steel of the self-shielded RDS Eclipse cyclotron, which has been out of operation for 9 years.
Since the Yoke steel of the cyclotron are bulky, they are suitable for applying survey-based clearance methods. A FHZ512 BGO(1.5 x 1.5-inch BGO) and FHZ512A(1.5 x 1.5-inch NaI(Tl)) scintillation-based rate meter, which have high detection efficiency, were considered as measurement equipment. First, detection limits according to ISO 11929-1 were obtained through background measurements for each detector. When the measurement time for the background and the Yoke steel was set to 60 seconds, the detection limits for the BGO detector and the NaI(Tl) detector were found to be 9 cps and 7.7 cps, respectively. Using the FLUKA 4-5.2 code, information on radionuclides of interest within Yoke steel was obtained through cyclotron activation calculations that reflected operational history. Subsequently, the expected count rate when measuring Yoke steel with scintillation-based rate meter was obtained using the FLUKA code, and if the count rate is greater than the detection limit, it is evaluated that survey-based clearance method is feasible. Based on results of FLUKA code calculation and field measurement at the cyclotron facility, it was found that it is reasonable to set the radionuclide of interest to a single nuclide, Co-60, rather than multiple nuclides, and that survey-based clearance method can be sufficiently applied to Yoke steel even considering the short measurement time.
| Topics | T5. Induced radioactivity and decommissioning |
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