title: Radiation safety management of residual long-lived radioactivity distributed in an inner concrete wall of a medical cyclotron room.
abstract: The depth distribution of residual long-lived radioactivity in the inner concrete wall of a medical cyclotron room was measured by assaying concrete cores. Seven long-lived radioactive nuclides ((46)Sc, (60)Co, (65)Zn, (134)Cs, (152)Eu, (22)Na and (54)Mn) were identified by gamma-ray spectrometry of the concrete samples. It was confirmed that the gamma-ray-emitting radionuclides induced by thermal neutrons through the (n, γ) reaction are dominant, and that the activity induced by thermal neutrons is greater at a depth of 10-30 cm, rather than at the surface of the concrete, and decreased exponentially beyond a depth of ~40 cm. Although the specific activity at the surface was greater than the clearance level for radioactive waste indicated in IAEA RS-G-1.7, the mean specific activities in the walls and floor were less than the clearance level.
authors.affiliation: Department of Environmental Health, National Institute of Public Health, 2-3-6 Minami, Wako, Saitama 351-0197, Japan. drhyama@niph.go.jp
authors.forename: Ichiro
authors.initials: I
authors.lastname: Yamaguchi
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Kimura
authors.forename: Toshioh
authors.initials: T
authors.lastname: Fujibuchi
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Kyoko
authors.initials: K
authors.lastname: Saito
authors.forename: Hidenori
authors.initials: H
authors.lastname: Otake
mesh_terms: D003252:Construction Materials; D017357:Cyclotrons; D005720:Gamma Rays; D006801:Humans; D009502:Neutrons; D011868:Radioisotopes / Q000032:analysis*; D017751:Safety Management; D013997:Time Factors
chemical_list: D011868:Radioisotopes