Abstract. In order to evaluate the state of activation in a cyclotron facility used for the radioisotope production of PET diagnostics, we measured the neutron flux by using gold foils and TLDs. Then, the spatial distribution of neutrons and induced activity inside the cyclotron vault were simulated with the Monte Calro calculation code for neutron transport and DCHAIN-SP for activation calculation. The calculated results are in good agreement with measured values within factor 3. Therefore, the adaption of the advanced evaluation procedure for activation level is proved to be important for the planning of decommissioning of these facilities.

To establish systematic guidelines for accelerator decommissioning, a large-scale activation survey was conducted at representative synchrotron radiation facilities in Japan. The neutron flux during accelerator operation was measured with various dosimeters. A Monte Carlo simulation was conducted for some facilities to verify the special neutron distribution and their spectra. Beam loss points, reflected as high-dose-rate areas, were identified by a wholebeamline survey with a survey meter, and the generated radionuclides and their activity were determined with a lanthanum bromide (LaBr 3 ) scintillation spectrometer. In all facilities, the activation level was quite low. Whole-beamline tunnels made of concrete were not activated, and no radionuclides were detected except for natural nuclides. In addition, almost all beamline components were either not or minimally activated. Although the acceleration energy is very high for radiation synchrotron facilities, the generation of radioactive waste would be very low.

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Normal-type fluorescent lamps, three-wavelength-type fluorescent lamps, and LED lamps were exposed to secondary particles during machine operation in the four different high-energy accelerator rooms at the Fermi National Accelerator Laboratory (FNAL), USA, and Dokkyo Medical University, Japan. After the exposure of the lamps, we determined the activity produced in the lamps and examined the lighting characteristics of the lamps. In order to compare activity production among the same types of the lamps, total fourteen kinds of the lamps were used for the exposure experiments. The least activity after 25 days of the exposure was exhibited by the LED lamps. In examining the lighting characteristics of the lamps, however, it was found that the LED lamps could not be used at thermal and epithermal neutron fluence exceeding 9.7 × 10 10 cm -2. It was found that normal-type fluorescent lamps are superior to the three-wavelength-type fluorescent lamps from the point of view of activity production. We concluded that normal-type fluorescent lamps are the most suitable for lighting in high-energy accelerator rooms.