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Title: SU-E-T-534: Level of Residual Radioactivity of Activated Parts of a Decommissioned Cyclotron

Purpose: CTI cyclotron RDS-111 was used at the Hong Kong Sanatorium and Hospital (HKSH) to produce radiopharmaceuticals and radioactive tracers for diagnostic scans between 1999 and 2007. During the operation, some machine components became radioactive by activation. For the safety of staff, decommissioning took place in 2009, two years after the cyclotron had stopped operation. This study investigates the residual radioactivity and radionuclides found in different cyclotron components in 2014 in compliance with the local regulations in Hong Kong for transfer of radioactive waste. Methods: A representative sample of each part was counted using a high-purity germanium detector (manufacturer: ORTECT) for at least four hours. GammaVision, a multichannel analyzer software, was used to identify the radionuclides found in the cyclotron components, as well as the associated activities. A standard library and a Mariscotti peak search algorithm were used to identify the present radionuclides. Only radionuclides with half-life greater than 180 days were considered. Results: Among the components, the Havar target foil has the highest specific activity ((4.6±0.6)×10{sup 2} Bq/g), with Co-60 being the most prominent ((3.8±0.5)×10{sup 2} Bq/g). The total activity of the target foil, however, is still low due to its small mass of 0.04 g. Radioisotopes Mn-54 (46±6more » Bq/g), Na-22 (6.8±0.8 Bq/g), Co-57 (7.3±0.9 Bq/g), and Fe-59 (6.0±0.9 Bq/g) have also been detected in the target foil. The target window holder and the vacuum window register a specific activity of 88.3±0.6 Bq/g and 48.6±0.1 Bq/g, respectively. Other components, such as the collimator, the target tube, the valve body and the beamline, are also found with trace amounts of radionuclides. Conclusion: Even seven years after the cyclotron had stopped operation, some components still exhibited residual radioactivity from activation exceeding the IAEA clearance levels. Special consideration for radiological protection may need to be taken in the disposal of the cyclotron parts.« less
Authors:
; ; ; ; ; ;  [1]
  1. Hong Kong Sanatorium and Hospital, Happy Valley (Hong Kong)
Publication Date:
OSTI Identifier:
22496252
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
61 RADIATION PROTECTION AND DOSIMETRY; 07 ISOTOPES AND RADIATION SOURCES; 43 PARTICLE ACCELERATORS; COBALT 57; COBALT 60; COMPUTER CODES; CYCLOTRONS; DECOMMISSIONING; FOILS; HONG KONG; ISOTOPE PRODUCTION; MANGANESE 54; MAXIMUM PERMISSIBLE ACTIVITY; OCCUPATIONAL EXPOSURE; OCCUPATIONAL SAFETY; RADIATION MONITORING; RADIATION PROTECTION; RADIOACTIVITY; RADIONUCLIDE KINETICS; SODIUM 22; TRACER TECHNIQUES