Speaker
Mr
Takayuki Nakabayashi
(Japan Environmental Research Co., Ltd.)
Description
In case of the decommissioning of cyclotron facility, it is important to evaluate the induced activity of various components of cyclotron. In this work, two types of cyclotron such as proton acceleration using a deflector and H- acceleration using a carbon stripper foil for beam extraction to target port were selected. The former type was Cyclone10/5 of IBA and the latter type was BC-1710 of JSW. Sample was obtained from yoke, sector magnet, coil, vacuum chamber, pedestal and diffusion pomp by drilling, core boring and cutting. Radioactivity was measured with Ge-detector.
(1) Cyclone 10/5
Major nuclides were 60Co and 54Mn in yoke, 60Co in coil, vacuum chamber, pedestal and diffusion pomp. In case of the sector magnet, 65Zn from surface cooper plating was also detected. Activity of 60Co of inside surface of the yoke was high and gradually decreased with depth. But activity of 54Mn induced by the (n,p) reaction from 54Fe was decreased more rapidly with depth. The ratiso of observed activity to clearance level (ΣD/C) of vacuum chamber, pedestal and major part of coil were lower than 1. The ratios (ΣD/C) of sector magnet, diffusion pomp and inside of yoke were higher than 1.
(2) BC-1710 of JSW
Observed major nuclides were almost same as Cyclone10/5. As sampling was performed three month after shutdown, short-lived nuclides such as 59Fe and 58Co were also observed. Induced activity of 60Co and 54Mn of yoke was high near the deflector (inside part) and the target (outside part). The attenuation curves of 60Co activity in yoke obtained from 10 sampling positions were almost same. The ratios (ΣD/C) obtained from most of the components were higher than 1. In case of yoke, we have to wait for 20 years to reach the clearance level.
In order to obtain the activity in various components, the use of survey meter is very convenient. Therefore it is very important to obtain the relation between dose and activity. Monte Carlo calculation is also important to evaluate the neutron transport and activation inside the components of cyclotron.
Takayuki Nakabayashi, Toshiyuki Yagishita, Hiroyuki Sasaki, Kazuhiro Matsumura, Yoshiyuki Yamaya
Japan Environment Research Co., Ltd., 6-24-1 Nishi-shinjuku, Shinjuku-ku, Tokyo 160-0023, JAPAN
Hiroshi Matsumura, Akihiro Toyoda, Kazuyoshi Masumoto,
High Energy Accelerator Research Organization (KEK)
1-1 Oho, Tsukuba, Ibaraki 305-0801, JAPAN
Primary author
Prof.
Kazuyoshi Masumoto
(High Energy Accelerator Research Organization)
Co-author
Mr
Takayuki Nakabayashi
(Japan Environmental Research Co., Ltd.)
