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We carried out detailed measurement of the double-differential cross sections of fluorine for the emissions of protons, deuterons, tritons, and α-particles with 14.2MeV incident neutrons. An improved charged-particle spectrometer with a pencil DT-neutron beam furnished at the FNS facility of the Japan Atomic Energy Agency enabled us to obtain precise data with a fine energy resolution over a wide energy range and an angular range from 15 to 150°. The present experiment is the first simultaneous measurement of the four different kinds of charged particles and provides useful data to establish a nuclear reaction model of fluorine as well as to confirm previous experimental data. Angular-differential cross sections for several discrete peaks corresponding to excited states of residual nuclei were extracted to discuss the reaction mechanism of charged-particle emission. The obtained data suggest that the charged-particle emission reaction of fluorine has a complicated mechanism in which there are contribution...

6LiF small neutron detectors with an optical fiber have been used to measure 6Li(n,α)T reaction rate distributions at thermal research reactors and accelerator facilities. In the present study, we developed an experimental method for the measurement of tritium production rate (TPR) of 6Li using this small detector in deuterium-tritium (D-T) neutron fields. Reaction rate measurements with the detector were conducted in the D-T neutron fields at the Fusion Neutronics Source (FNS) facility. From the results, we determined that this detector can be used to measure the TPR distribution in soft neutron spectrum fields such as in a Be assembly. It is difficult to obtain 6Li(n,α)T reaction rate separately in hard neutron spectrum fields such as in a Li2O assembly, because many kinds of charged particle production reactions need to be taken into consideration. However, a time-dependent reaction rate measurement method combined with the 6LiF detector and the ZnS detector is effective to separate the 6Li(n,α)T react...

We carried out a detailed measurement of the neutron-induced α-particle emission double-differential cross section of carbon at 14.2MeV, for which there are few measured data in spite of its importance in many applications. In our measurement, a superior S/N ratio, high angular/energy resolutions and a wide detection energy range were realized with a pencil DT neutron beam and a countertelescope system. The obtained cross section for the 12C(n,α0)9Be(ground state) reaction agreed well with the results of previous experiments and evaluated nuclear data. The obtained angular-differential cross section of the 12C(n,n′+3α) reaction for α-particles showed a strong forward-peaked distribution that suggested a significant contribution of the direct reaction process to the 3α breakup. We attempted to calculate the emitted particle spectra by a Monte Carlo method and estimate the branching ratio of the channels that contribute to the 12C(n,n′+3α) reaction. As a result, it was found that the 12C(n,α)9Be* channels p...

A general-purpose transport and burnup code system for precise analysis of subcritical reactors like a fusion-fission (FF) hybrid reactor was developed and used for analyzing their performance. The FF hybrid reactor is a subcritical system, which has a concept of fusion reactor with a blanket region containing nuclear fuel and has been under discussion by author’s group for years because the present burnup calculation system mainly consists of a general-purpose Monte Carlo code MCNP-4B, a point burnup code ORIGEN2. JENDL-3.3 pointwise cross section library and JENDL Activation Cross Section File 96 were used as base cross section libraries to make group constant for burnup calculation.A new method has been proposed to make group constant for the burnup calculation as accurate as possible directly using output data of the neutron transport calculation by MCNP and evaluated nuclear data libraries. This method is strict and a general procedure to make one group cross sections in Monte Carlo calculations, whi...