| Project/Area Number |
05508003
|
|---|
| Research Category |
Grant-in-Aid for Developmental Scientific Research (A)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
環境影響評価(含放射線生物学)
|
|---|
| Research Institution | KYOTO UNIVERSITY |
|---|
Principal Investigator |
UTSUMI Hiroshi Kyoto Univ., Research Reator Institute, Professor, 原子炉実験所, 教授 (20025646)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
S.SASAKI M Kyoto Univ., Radiation Biology Center, Professor, 放射線生物研究センター, 教授 (20013857)
HOSHI M Hiroshima Univ., Res.Inst.Nucl.Med.Biol., Professor, 原爆放射能医学研究所, 教授 (50099090)
KOBAYASI K Kyoto Univ., Research Reator Institute, Professor, 原子炉実験所, 助教授 (80027466)
FUJITA Y Kyoto Univ., Research Reator Institute, Professor, 原子炉実験所, 教授 (60027422)
UTSURO M Kyoto Univ., Research Reator Institute, Professor, 原子炉実験所, 教授 (50027421)
生島 隆治 京都大学, 原子炉実験所, 助教授 (80027458)
斉藤 真弘 京都大学, 原子炉実験所, 助教授 (40027454)
|
|---|
| Project Period (FY) |
1993 – 1994
|
| Project Status |
Completed (Fiscal Year 1994)
|
| Budget Amount *help |
¥36,800,000 (Direct Cost: ¥36,800,000)
Fiscal Year 1994: ¥13,100,000 (Direct Cost: ¥13,100,000)
Fiscal Year 1993: ¥23,700,000 (Direct Cost: ¥23,700,000)
|
|---|
| Keywords | monoenergetic intermediate neutron / Fe-filtered neutrons / chromosome aberrations / 24 keV neutron / Twin chamber / 毛細血管拡張性運動失調症 / 中性子フイルター |
|---|
| Research Abstract |
Very little direct measurements have been made of the biological effects of neutrons below 100 keV.Recently, an iron-filtered 24 keV neutron beam of Harwell Materials Testing Reactor, PLUTO,was reported to be highly efficient in inducing chromosome aberrations : the efficiency being comparable to that of fission neutrons. This results could have serious repercussions for radiation protection standards as the ICRP assume a decrease in neutron RBE below 100keV.The investigations reported here have as their primary purpose the production of neutron beams at the 24keV iron window energy, using the B-1 experimental facility of the Kyoto University Research Reactor (KUR) at the Research Reactor Institute, Kyoto University (KURRI). The filtered neutron filed for biological applications is designed to maximized the contributions of neutrons with other energies and gamma rays. The characteristics of the radiation field were obtained by the simple transmission calculations for Fe (45cm), Al (35cm) andS (20cm) filters by using the Monte Carlo code MCNP,and by the measurement of nuclear heating for Fe and Al filter pieces. The 24keV neutron flux and gamma-ray dose rate were measured using Twin chamber. The measured findings are as follows : The 24keV neutron dose rate was approximately 5.5 rad/h, and the gamma-ray dose rate was 2.3 rad/h at the irradiation field at the distance of 46cm from the surface of the B-1 plug. Kerma contribution of neutrons under an energy of 100 keV is approximately 75% of total neutron dose. Human peripheral blood lymphocytes were irradiated and types and rates of induced chromosome aberrations (dicentrics and rings) were analyzed in their first post-irradiation mitosis. RBE of Fe-filtered neutrons were efficient as Uranium fission neutrons (Heavy water facility of KUR) and 14 MeV d (T,n) neutrons. The high RBE value and high radiation weighting factor of Fe-filtered neutrons contradict to the prediction of ICRP (1991), and remain to be elucidated.
|
