Article

Distortion of neutron field during mice irradiation at Kinki University reactor UTR-KINKI.

Research Institute for Radiation Biology and Medicine, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
Applied Radiation and Isotopes (Impact Factor: 1.18). 10/2007; 65(9):1037-40. DOI: 10.1016/j.apradiso.2007.04.018
Source: PubMed

ABSTRACT A dosimetry study of mice irradiation at the Kinki University nuclear reactor (UTR-KINKI) has been carried out. Neutron and gamma-ray doses at the irradiation port in the presence of 0, 1, 2, 4 and 6 mice were measured using the paired chamber method. The results show that neutron dose is reduced with increasing numbers of mice. In the six-mice irradiation condition, neutron dose is about 15% smaller compared to a case where no mice were placed in the irradiation port. To investigate the distortion of the neutron spectrum during mice irradiation at UTR-KINKI, a Monte Carlo calculation using the MCNP4C code has been carried out. The measured variation in dose with respect to the total mouse mass was closely reproduced by the calculation results for neutron and gamma-ray dose. Distortion of the neutron spectrum was observed to occur between 1 keV and 1 MeV.

0 Bookmarks
 · 
56 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Morphology and function (secretion of thyroid hormone) of human thyroid tissues from Graves' disease patients are well maintained in C57BL/6J-scid mice. Serum level of thyroid hormone was reduced by fission neutrons from the nuclear reactor UTR-KINKI, and changes in thyroid hormone by fission neutrons were bigger than those by low LET radiations, X-rays and (137)Cs gamma-rays, suggesting high relative biological effectiveness (RBE; 6.5) of fission neutrons. Microarray analyses revealed that about 3% of genes showed more than 4-fold change in gene expression in the unexposed thyroid tissues against surgically resected thyroid tissues from the same patient, probably due to the difficult oxygen and nutrient supply shortly after transplantation. Dose-dependent changes in gene expression against unexposed concurrent controls were observed with increasing doses of fission neutrons (0.2-0.6Gy) and (137)Cs gamma-rays (1.0-3.0Gy) and showed high RBE (4.2). Furthermore, there were some specific genes which showed more than 4-fold change in gene expression in all the thyroid tissues exposed to higher doses of radiation, especially neutrons (0.4 and 0.6Gy), but none at lower doses (0.2Gy of neutrons and 1.0 and 2.0Gy of gamma-rays). These genes related to degeneration, regeneration, apoptosis, and transcription, respond specifically and very sensitively to neutron injury in human thyroid tissues. This is the first experimental report that fission neutrons can induce some morphological and functional disorders in human tissues, showing high RBE against gamma-ray exposure. These results are useful to evaluate the risks of fission neutrons and cosmic rays to humans.
    Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 02/2010; 696(2):107-13. · 3.90 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Microdosimetry study has been carried out at the education and research mini-reactor of Kinki University (UTR-KINKI) using a tissue equivalent gas proportional counter (TEPC). The microdosimetric single event spectra for 0.5, 1, 2, 3 and 5 microm site sizes were obtained in the lineal energy range from 1 to 1000 keV/microm. Neutron and gamma-ray fractional doses were estimated from the single event spectra. The neutron dose fraction was varied from 35 to 55% for 0.5 to 5 microm site size. The averaged lineal energy, y(D), for each site size was likewise estimated and found to be dependent on the site size. The averaged lineal energy for neutron was slightly larger than that of the fission neutrons from (252)Cf, and the averaged lineal energy for gamma-ray had similar site-size-dependence of 25 keV gamma-rays and 250 kV X-rays. Relative biological effectiveness was found to be 4.1 +/- 0.13 for UTR-KINKI using Tilikidis's 2 Gy-response function. The estimated RBE for UTR-KINKI neutrons is quite close to the previous biological experimental value of 4.3 +/- 0.6 for micronucleated cells in gill cell of Medaka and 4.6 +/- 0.5 for induction of lymphocyte apoptosis in the thymus of ICR mice.
    Journal of Radiation Research 02/2009; 50(1):83-7. · 1.45 Impact Factor

Full-text

View
1 Download
Available from
Jul 16, 2014