title: [Decommissioning of the medical cyclotron in National Center of Neurology and Psychiatry].
abstract: OBJECTIVE
  In Japan, positron emission tomography has prevailed as a useful procedure for detecting malignancy, myocardial viability, and epileptic foci. Consequently, compact medical cyclotrons have been installed in many hospitals. However, reports about the dismantling or decommissioning of compact medical cyclotrons are rare. This report describes the series of steps involved in the decommissioning of a compact medical cyclotron that had been used to produce radioactively tagged substances over a period of fifteen years at the National Center of Neurology and Psychiatry in Japan. Additionally, this report describes the manner in which the radioactive waste was disposed.
  
  
  METHODS
  The plan to decommission the cyclotron was comprised of three phases: a preliminary survey, the dismantling work, and a reports after the dismantling. We complied with the guidelines for the disposal of radioactive waste published by the Ministry of Education, Culture, Sports, Science and Technology.
  
  
  RESULTS
  The most radioactive material was the vacuuming foil used in the window of the target chamber, with a dose rate of 17 microSv/h (gamma rays) and 20 x 10(3) cpm (beta rays). The detected radionuclides were mainly 22Na, 57Co, 60Co and 65Zn. The total numbers of radioactive waste containers were thirteen 200 l containers and one 50 l container. We suspect that the long shutdown period of the cyclotron (more than one year) contributed to the decay of the radioactive waste because the amount of containers was smaller than the initial estimation.
  
  
  CONCLUSIONS
  The shutdown period of a cyclotron may play a significant role in reducing the amount of radioactive waste.
authors: Department of Radiology, National Center of Neurology and Psychiatry.
authors: Kimiteru
authors: K
authors: Ito
authors: Yasuhiro
authors: Y
authors: Nakata
authors: Hiroshi
authors: H
authors: Matsuda
authors: Noriko
authors: N
authors: Sato
mesh_terms: D000046:Academic Medical Centers; D017357:Cyclotrons; D007564:Japan; D009462:Neurology; D049268:Positron-Emission Tomography; D011570:Psychiatry; D011850:Radioactive Waste / Q000032:analysis
chemical_list: D011850:Radioactive Waste