Japan Atomic Energy Research Institute

About: Japan Atomic Energy Research Institute is a based out in . It is known for research contribution in the topics: Neutron & Irradiation. The organization has 7707 authors who have published 14471 publications receiving 207688 citations.

Calculation of the effective dose and its variation from environmental gamma ray sources.

Abstract: Effective dose, an indicator of the stochastic effect of radiation, has been widely used in dose evaluation in the environment. Though conversion factors have been used to obtain E from the air kerma or air absorbed dose, the variation of the conversion factors due to the change of exposure conditions has not been sufficiently investigated. This report documents an investigation of the variation of the effective dose per air kerma for environmental gamma rays depending on the exposure conditions using anthropomorphic phantoms and Monte Carlo calculations, taking into account the precise angular and energy distributions of the environmental gamma rays incident on the human body. As causes of the variation, posture of human bodies, biases of environmental source distributions, and body size were considered. The variation of effective dose in a prone position compared with that in a standing position was found to be within 30%. The bias of environmental sources causes the effective dose per air kerma to vary by 20% at maximum, but in some cases for low-energy gamma rays the variation was found to be up to 40% due to the change in the energy spectrum. The effective dose for a new born infant was estimated to be higher than that for an adult by a maximum of 80-90% for low-energy gamma rays from anthropogenic sources because of a lower shielding effect of the smaller body. The variation of the effective dose equivalent shows a similar tendency to the effective dose. Consequently, this study made it possible to estimate the uncertainties of effective dose and effective dose equivalent evaluated from air kerma or absorbed dose in air using the standard available conversion factors.

Extension of quantum molecular dynamics and its application to heavy-ion collisions.

Abstract: In order to treat low-energy heavy-ion reactions, we make an extension of quantum molecular dynamics method. A phenomenological Pauli potential is introduced into effective interactions to approximate the nature of the Fermion many-body system. We treat the widths of nucleon wave-packets as time-dependent dynamical variables. With these modifications, our model can well describe the ground-state properties in wide mass range. Improvements due to the extension are also obtained in the nucleus-nucleus collision calculations.

Mutation induced with ion beam irradiation in rose

Abstract: The effects of mutation induction by ion beam irradiation on axillary buds in rose were investigated. Axillary buds were irradiated with carbon and helium ion beams, and the solid mutants emerged after irradiation by repeated cutting back. In helium ion irradiation, mutations were observed in plants derived from 9 buds among 56 irradiated buds in ‘Orange Rosamini’ and in plants derived from 10 buds among 61 irradiated buds in ‘Red Minimo’. In carbon ion, mutations were observed in plants derived from 12 buds among 88 irradiated buds in ‘Orange Rosamini’. Mutations were induced not only in higher doses but also in lower doses, with which physiological effect by irradiation was hardly observed. Irradiation with both ion beams induced mutants in the number of petals, in flower size, in flower shape and in flower color in each cultivar.

Magnetic Correlation of NaxCoO2 and Successive Phase Transitions of Na0:5CoO2 —NMR and Neutron Diffraction Studies—

Abstract: Data taken by various methods including NMR/NQR and neutron scattering are presented for Na x CoO 2 , particularly Na 0.5 CoO 2 . Attention has also been paid to the x dependence of the electronic nature of this system. The pseudo-gap-like behavior observed in the region of x < x c ∼0.6 is emphasized. For samples with x ≤0.6, signals from two kinds of Co sites with different quadrupole frequencies ν Q of ∼4.1 and ∼2.8 MHz were observed, and the former ν Q , which is nearly equal to that of the superconducting system Na 0.3 CoO 2 · y H 2 O, becomes dominant with decreasing x to 0.3. For Na 0.5 CoO 2 , the Co sites with the larger ν Q have larger magnetic moments. They align antiferromagnetically at T c1 ∼87 K with their direction within the plane, while the Co sites with the smaller ν Q have smaller moments. They align in the direction parallel to the c axis. The ordered moments at the two distinct sites exhibit the same T -dependence, indicating that the existence of these sites is not due to macroscopic ...