title: Reduction of the gamma-ray component from 252Cf fission neutron source--optimization for biological irradiations and comparison with MCNP code.
abstract: Gamma-rays contribute 33% of the absorbed dose from an unfiltered 252Cf fission neutron source. To reduce this gamma-ray component and to enable radiobiological experiments at as high a dose rate as possible, Monte Carlo calculations for several filter materials (Al, Fe, Pb and concrete) have been made using MCNP neutron and photon transport code version 4a. A lead filter of thickness 4 cm was found to reduce the gamma-ray component to 6.7% of the total dose whilst reducing the neutron dose by only about 10%. Such a filter was installed at the MRC 252Cf neutron irradiation facility and dosimetric measurements were made using a TE-TE chamber and a 7LiF(Mg, Cu, P) TLD. Monte Carlo simulations agree with experimental measurements of neutron and gamma-ray doses within 6%. V79-4 Chinese hamster cells were irradiated with lead-filtered and unfiltered neutrons and also with 60Co gamma-rays at two dose rates. The survival fraction obtained for each radiation was consistent with the reduced gamma-ray dose. The relative biological effectiveness for neutrons alone, corrected for gamma-ray effects, was found to be 9.2 +/- 3.4 from the initial slopes and 3.1 +/- 0.5 at 10% survival, both relative to the acute gamma-rays.
authors.affiliation: Research Institute for Radiation Biology and Medicine, Hiroshima University, Japan. endos@ipc.hiroshima-u.ac.jp
authors.forename: S
authors.initials: S
authors.lastname: Endo
authors.forename: D L
authors.initials: DL
authors.lastname: Stevens
authors.forename: P
authors.initials: P
authors.lastname: Bonner
authors.forename: M A
authors.initials: MA
authors.lastname: Hill
authors.forename: H
authors.initials: H
authors.lastname: Nikjoo
authors.forename: M
authors.initials: M
authors.lastname: Dalla Vecchia
authors.forename: K
authors.initials: K
authors.lastname: Komatsu
authors.forename: M
authors.initials: M
authors.lastname: Hoshi
authors.forename: D T
authors.initials: DT
authors.lastname: Goodhead
mesh_terms: D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D002142:Californium; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D005720:Gamma Rays; D009010:Monte Carlo Method; D009502:Neutrons; D011853:Radiobiology; D011874:Radiometry / Q000706:statistics & numerical data; D012062:Relative Biological Effectiveness
chemical_list: D002142:Californium