[2H11-15] Non-destructive Inspection

[2H15] Measurements for residual activities in the self-shield of PET-cyclotron (HM-12S), and non-destructive activation assessment

*Go Yoshida¹, Hiroshi Matsumura¹, Akihiro Toyoda¹, Kiyokazu Tsugane¹, Ayumi Yamamoto², Iwane Komura³, Masahiko Kozaki², Hajime Nakamura¹, Kazuyoshi Masumoto¹, Taichi Miura¹ (1. KEK, 2. ATEX, 3. Sumitomo Heavy Industries)

Keywords:PET-cyclotron, Self shield, Activation measurement, Decommissioning

The activation status of the self-shielded cyclotron HM-12S manufactured by Sumitomo Heavy Industries was investigated experimentally. Residual nuclides and their radioactivity on the self-shield surface were revealed non-destructively with the CeBr₃ detector. Direct sampling from the self-shield was conducted to determine the depth profile of the radionuclides. Only two nuclides; 54Mn and 60Co, were identified on the self-shield surface. Although ⁵⁴Mn was distributed locally near the target, ⁶⁰Co was found throughout the surface. From the surface to the inside of the self-shield, activities of ⁵⁴Mn and ⁶⁰Co are decreased with the same attenuation rate. From the experimental results of the other facility, we have found the ⁶⁰Co activity is almost the same level between the surface to 20 cm depth in the ordinary concrete at the PET-cyclotron vault due to the build-up phenomenon, though the depth distribution in the heavy concrete of the self-shield was different from this.