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.

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.

In the process of decommissioning a tritium-handling laboratory, direct-immersion and water-extraction methods for measuring tritium contamination in concrete were compared to a heating-cooling method. For this evaluation, concrete pieces chipped from contaminated concrete walls and floors were used. The direct-immersion method was about 2.5 times less sensitive at determining the level of contamination compared to the heating-cooling method. The water-extraction method was comparable with the heating-cooling method if the water extraction time was adequate.

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