Fujio Maekawa

AMATERAS: A Cold-Neutron Disk Chopper Spectrometer

AMATERAS is a new disk-chopper-type spectrometer installed at Materials and Life Science Experimental Facility (MLF) of J-PARC. AMATERAS is equipped with an extra chopper for pulse shaping at the upstream position, in addition to a monochromating chopper, which conventional chopper spectrometers at pulsed source have. Owing to the use of these choppers and the high peak intensity from a coupled moderator source at MLF, the AMATERAS design realizes high-intensity and high-energy-resolution measurements in quasielastic and inelastic neutron scattering experiments. The spectrometer had the first neutron beam in May 2009. During the course of commissioning, the performance of the spectrometer was confirmed by conducting test experiments. AMATERAS is now open to users and is producing scientific outputs.

JENDL High Energy File

Nuclear Data Center at Japan Atomic Energy Research Institute is developing the JENDL High Energy File in cooperating with Japanese Nuclear Data Committee. The JENDL High Energy File includes neutron and proton nuclear data 20 MeV to 3 GeV. In this report, reported are evaluation methods and results of the evaluation and benchmark tests for the JENDL High Energy File.

Fusion Neutronic Source deuterium–tritium neutron spectrum measurements using natural diamond detectors

Two natural diamond detectors (NDDs) operating at room temperature were used for Fusion Neutronics Source (FNS) deuterium–tritium (DT) neutron spectra measurements at different points around the tritium target and for different deuteron beam energies. Energy resolution of both NDDs were measured, with values 1.95% and 2.8%. Due to the higher energy resolution of one of the two NDDs studied it was possible to measure the shape of the DT neutron energy distribution and its broadening due to deuteron scattering inside the target. The influence of pulse pileup on the energy resolution of the combined system (NDD+electronics) at count rates up to 3.8×105 counts/s was investigated. A 3.58% energy resolution for the spectrometric system based on NDD and a 0.25 μs shaping time amplifier has been measured at a count rate of 5.7×105 counts/s. It is shown that special development of a fast pulse signal processor is necessary for NDD based spectrometry at count rates of approximately 106 counts/s.

Phase III experimental results of JAERI/USDOE collaborative program on fusion neutronics

Abstract A pseudo-line D–T neutron source has been developed with new experimental techniques. This line source was applied in sophisticated neutronics experiments for an annular blanket arrangement simulating the tokamak geometry, as a new series in the JAERI/USDOE collaborative experimental program on fusion neutronics. The source characteristics of the present line source and the measurements for an annular assembly are described. The discussion on the experimental results focuses on the tritium production rate measured in an annular blanket and comparisons were made with the previous point source experiment, and also between the annular blankets with and without an armor reflector of graphite.

Windows of Cold Nuclear Fusion and Pulsed Electrolysis Experiments

This paper discuses the electron screening effect and the excitation of deuteron harmonic oscillators in a palladium lattice, possible explanations of cold fusion phenomena and the possibility of nuclear heating. A narrow window is proposed to reach the {approximately}10 W/cm{sup 3} required nuclear heating for three-body fusion by a hypothetical excitation-screening model. A relatively wide window is feasible to reach a few fusion events per second per cubic centimetre under the non-stationary conditions of deuteron charging and discharging. Cold fusion is not feasible under stationary lattice conditions.

Measurement and Analysis of Nuclear Heat Depositions in Structural Materials Induced by D-T Neutrons

AbstractNuclear heat deposition rates in ten different materials, Li2CO3, Graphite, Ti, Ni, Zr, Nb, Mo, Sn, Pb and W, subjected in D-T neutrons have been measured by a microcalorimetric technique in the frame work of JAERI/USDOE collaborative program on fusion neutronics. A great improvement in accuracy of experimental data was achieved by introducing a high sensitivity voltmeter and applying constant current on the thermal sensors. The measured heating rates were compared with calculations to verify the adequacy of the currently available data base relevant to the nuclear heating process. In general, calculations with data of JENDL-3 and ENDL-85 libraries gave excellent agreements with experiments for all materials except Zr. The calculation with the MBCCS suffered large discrepancy from measurement.

Photon emission induced by fusion neutrons on optical window materials

Abstract In situ 14 MeV neutron, 60 Co gamma-ray and ion beam irradiation experiments were performed to analyze photons emitted from sapphire and quartz. Wavelength spectrum of photons emitted from sapphire during 14 MeV neutron irradiation had luminescence peaks around 330, 410 and 690 nm, and the spectrum from quartz had luminescence peaks around 450 and 650 nm. These spectra were compared with those measured for gamma-ray and ion beam irradiations. The luminescence intensity was proportional to the 14 MeV neutron flux. As for window materials at low damage levels, it has been found from the comparison of the spectra that there is no large difference in the luminescence mechanism between 14 MeV neutron, gamma-ray and ion beam. However, the number of photons per unit absorbed energy for 14 MeV neutrons in the visible range was one order smaller than that for 60 Co gamma-rays. The data on the luminescence of window materials for 14 MeV neutron and gamma-ray irradiations should be useful for the design of D–T fusion plasma diagnostic system.

An investigation of the activation of water by D-T fusion neutrons and some implications for fusion reactor technology

Abstract Several fundamental aspects of the activation of water by neutrons in D-T fusion systems have been investigated in this work. The basic physical principles involved and the status of pertinent nuclear cross-section and radioactivity data were reviewed. The integral response of the dominant 16 O(n,p) 16 N reaction was calculated using several evaluated differential cross-section representations and characteristic D-T fusion neutron spectra. The impact of cross-section uncertainties was also assessed in this context. Two integral experiments were carried out at a D-T neutron generator facility to investigate the production and transport of 16 N radioactivity in a D-T fusion neutron environment. Radioactivity yield data were acquired in one of these integral experiments (IE-1) and the measured results were compared with values obtained from calculations which employed both analytical and Monte-Carlo techniques. Measurements on the shielding of high-energy gamma rays from 16 N decay by stainless steel (SS-304) and copper were performed in an additional integral experiment (IE-2) and these data were interpreted by a combination of analytical calculations and Monte-Carlo simulation. Some consequences of neutron-induced 16 N radioactivity in the cooling water of a fusion reactor were examined for two contemporary conceptual designs of the International Thermonuclear Experimental Reactor (ITER). This analysis benefitted from insight acquired through the present integral studies. It was found that this radioactivity generating process would lead to significant biological doses outside the reactor containment vessel and could also deliver potentially damaging radiation doses to superconducting magnet insulators unless care is taken to provide adequate shielding when designing a fusion reactor.

Research Activities on Neutrorics under ASTE Collaboration at AGS/BNL

A series of experiments on a mercury spallation target using high-peak-power GeV proton-beam from the Alternating Gradient Synchrotron (AGS) of Brookhaven National Laboratory (BNL) has been performed under an international collaboration among the laboratories in Japan, U.S. and Europe, namely the ASTE (AGS Spallation Target Experiment) collaboration. This paper reviews the current status of the experiments on neutronic performance of the mercury target.

Benchmark experiment on silicon carbide with D–T neutrons and validation of nuclear data libraries

Abstract Silicon carbide (SiC) is one of the low activation structural materials for fusion reactors. A benchmark experiment on SiC was conducted at the deuterium–tritium (D–T) neutron source facility FNS in JAERI, and the validity of the cross section data for SiC was investigated. An experimental assembly made of sintered SiC (457×457 mm, and 711 mm in thickness) was bombarded by D–T neutrons, and neutron spectra, gamma-ray spectra, dosimetry reaction rates and gamma-ray heating rates were measured in the assembly. Computational analyses of the experiment were performed by Monte Carlo transport calculations with the MCNP-4B code and several recent evaluated nuclear data files. The following findings were pointed out. The calculations with JENDL Fusion File and JENDL-3.2 predicted adequately the neutron fluxes from 14 MeV to 0.3 eV as well as the gamma-ray fluxes at any positions up to ∼600 mm depth in the SiC assembly. Results for the calculation with FENDL/E-2.0 were similar to those with the two JENDL calculations, but the neutron fluxes in the energy range from 1 to 14 MeV were calculated slightly smaller. The cross section data for silicon in FENDL/E-1.0 were found inadequate for nuclear design calculations.