title: Comparison of neutron fluxes in an 18-MeV unshielded cyclotron room and a 16.5-MeV self-shielded cyclotron room.
abstract: Some medical compact cyclotrons have self-shielding to reduce neutron fluxes. Thermal neutron fluxes in an 18-MeV unshielded cyclotron room and in a 16.5-MeV self-shielded cyclotron room were evaluated. In addition, the radioactivities in concrete and metals due to thermal neutrons in the cyclotron rooms for 30 years were calculated of operation such that the sum of the ratio of the nuclide concentration to the nuclide clearance level was equal to 1. The thermal neutron flux from the unshielded cyclotron was approximately 10(2) cm(-2) s(-1), whereas that from the self-shielded cyclotron was approximately 10(2) cm(-2) s(-1). The thermal neutron fluxes for concrete, stainless steel, vessel steel, and aluminum that reached their clearance levels were 9.80 × 10(4), 2.17 × 10(3), 1.87 × 10(4), and 2.41 × 10(5) cm(-2) s(-1), respectively. The specific activities in the cyclotron room were found to be sufficiently below the clearance level when the self-shield was employed.
authors.affiliation: Department of Radiological Sciences, School of Health Sciences, Ibaraki Prefectural University of Health Sciences, Ami 4669-2, Ami-machi, Inashiki-gun, Ibaraki 300-0394, Japan. fujibuchi@ipu.ac.jp
authors.forename: Toshioh
authors.initials: T
authors.lastname: Fujibuchi
authors.forename: Genki
authors.initials: G
authors.lastname: Horitsugi
authors.forename: Ichiro
authors.initials: I
authors.lastname: Yamaguchi
authors.forename: Akihisa
authors.initials: A
authors.lastname: Eto
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Iwamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Obara
authors.forename: Takashi
authors.initials: T
authors.lastname: Iimori
authors.forename: Yoshitada
authors.initials: Y
authors.lastname: Masuda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watanabe
authors.forename: Jun
authors.initials: J
authors.lastname: Hatazawa
mesh_terms: D017357:Cyclotrons; D006046:Gold; D009502:Neutrons / Q000009:adverse effects*; D011835:Radiation Protection / Q000295:instrumentation*; D012449:Safety; D013696:Temperature
chemical_list: D006046:Gold