Koichi Tsuda

A small spherical NE213 scintillation detector for use in in-assembly fast neutron spectrum measurements

Abstract A small spherical 14 mm diameter NE213 scintillation spectrometer has been developed. Its linearity, gain stability and pulse shape discrimination were examined through experiments using a 14 MeV neutron field. The pulse responses were analyzed by a Monte Carlo code and compared with the measured ones. The detector proposed by us is superior in in-assembly measurements.

Experimental results for Phase II of the JAERI/USDOE collaborative program on fusion blanket neutronics

As the first period of the Phase II series of the JAERI/USDOE collaborative program, neutronic parameters have been measured for a simulated Li 2 O/Be breeder blanket in closed geometry. The experimental system consists of a lithium-oxide test zone and a lithium carbonate enclosure containing a DT neutron source at the Fusion Neutronics Source (FNS) facility at JAERI. Tested blankets were of three 5 cm thick configurations of beryllium neutron multiplier zone. The experiments were performed to examine spatial distributions of reaction rates and the neutron spectrum in the source cavity, and relative profiles of the tritium production rate (TPR), reaction rates, and neutron spectra between the beryllium configurations. A zonal TPR measuring technique, suitable especially for direct comparison with a Monte Carlo method, was applied to a steep gradient distribution. The experimental results of TPRs showed that the beryllium sandwiched system provided the most effective TBR gain (integrated TPR) of about 20% compared with the non-multiplier system. The reaction rate distributions and neutron energy spectra were also provided to test a calculational code system for nuclear design.

Design and techniques for fusion blanket neutronics experiments using an accelerator-based deuterium-tritium neutron source

The experiments performed in the Japan Atomic Energy Research Institute/U.S. Department of Energy collaborative program on fusion blanket neutronics are designed with consideration of geometrical and material configurations. The general guide that is used to design the engineering-oriented neutronics experiment, which uses an accelerator-based 14-MeV neutron source, is discussed and compared with neutronics characteristics of the reactor models. Preparation of the experimental assembly, blanket materials, and the neutron source is described. A variety of techniques for measuring the nuclear parameters such as the tritium production rate are developed or introduced through the collaboration as a basis of the neutronics experiments. The features of these techniques are discussed with the experimental error and compared with each other. 25 refs., 15 figs., 4 tabs.

Neutronics integral experiments of lithium-oxide fusion blanket with heterogeneous configurations using deuterium-tritium neutrons

Neutronics experiment for two types of heterogeneous blankets are performed in the Phase-IIC experiments of the Japan Atomic Energy Research Institute/U.S. Department of Energy collaborative program on fusion blanket neutronics. The experimental system uses the same geometry as the previous Phase-IIA series, which was a closed geometry that used a neutron source enclosure of lithium carbonate. The heterogeneities selected for testing are the beryllium edge-on and the water coolant channel assemblies that appear in typical blankets. In the former, the beryllium and the lithium-oxide (Li{sub 2}O) layers are piled up alternately in the front part of the test blanket. In the latter, the two simulated water cooling channels are emplaced vertically in the Li{sub 2}O blanket. These channels produce a steep gradient of neutron flux and a significant spectrum change around the material boundary. The calculation accuracy and measurement method for these transient regions are key areas of interest in the experiments. The measurements are performed for the tritium production rate and the other nuclear parameters as well as the previous experiments. The void effect is found to not be negligible around the heterogeneous region for the detector with a low-energy response. At the same time, enhancements of tritium productionmorexa0» are seen near the beryllium and hydrogenous material. However, the current Monte Carlo calculation shows good agreement with the experiment even in such a boundary. 22 refs., 20 figs., 7 tabs.«xa0less

Measurement techniques for fusion blanket neutronics experiments

Abstract A variety of techniques to measure the nuclear parameters, such as tritium production rate, neutron spectrum, reaction rate and gamma-ray heating, in a simulated fusion blanket assembly have been developed or introduced through the JAERI/USDOE Collaborative Program on Fusion Blanket Neutronics. The features of those techniques are summarized and discussed with the experimental error. The present measurement techniques provided data with error ranges of 3–5% for tritium production, 5–10% for the neutron spectrum, 3–6% for the activation reaction and 10–20% for the gamma-ray heating rate.

Neutron source and field characteristic measurements for JAERI/USDOE Phase-II experiments on fusion blanket neutronics

Measurements on the D-T source and field characteristics were carried out to provide data for verifying the calculation of the source term used in subsequent analysis for Phase-II experiments of the JAERI/USDOE collaborative program on fusion blanket neutronics. Neutron flux distributions inside of the Phase-II closed system were measured by activation foils distributed on the Li 2 CO 3 enclosure as well as on the front surface of Li 2 O testing zone. The multi-foil activation technique, a small sphere NE213 spectrometer, and a proton recoil counter were applied to measure the neutron spectrum on the front face of the testing zone. The results showed good symmetry of the neutron flux distribution on the surface of the test region as well as in most parts of the cavity. It was proved that the Li 2 CO 3 enclosure with polyethylene served as a good insulator between fields inside and outside of the system. As an attempt, the neutron source position and strength were estimated utilizing the mapped activation reaction rates. Values estimated were in good agreement with the actual source position and the source strength determined by the associated a particle counting method. It was suggested that this approach based on the foil activation technique is promising for the determination of D-T source strength and mean source position in a plasma.

Measurement of tritium production-rate distribution in a 60 cm-thick Li/sub 2/O slab assembly and its analysis

Tritium production-rate (TPR) distributions were measured in a Li/sub 2/O slab assembly using the FNS. The size of assembly was 31.5 cm in equivalent radius and 61.0 cm in thickness. Enriched /sup 6/Li and /sup 7/Li sintered pellets of Li/sub 2/O were adopted to measure the TPRs of /sup 6/Li and /sup 7/Li, separately. After irradiated pellets were treated chemically, tritium produced in the pellets was measured by a liquid scintillation counting system. Measured TPR distributions have been analyzed by using the three transport codes, DOT3.5, MORSE-DD and BERMUDA-2DN with ENDF/B-4 and JENDL-3PR1 nuclear data files. The JENDL-3PR1 improves the accuracy of calculated TPR very well for both /sup 6/Li and /sup 7/Li.

Neutronics integral experiments of simulated fusion reactor blanket with various beryllium configurations using deuterium-tritium neutrons

Fusion neutronics experiments are performed on a full-coverage blanket with various configurations of a beryllium neutron multiplier. In the basic experimental system, a lithium carbonate enclosure contains a lithium oxide test zone and a deuterium-tritium neutron source to simulate a neutron spectrum in a fusion reactor. Five beryllium configurations are adopted to examine the effects of neutron multiplication and reflection by beryllium. The measurements are carried out along the central line in the test zone. Various measurement techniques are applied to obtain the tritium production rate distribution, which is one of the most important parameters for assessing the total tritium breeding ratio in a fusion blanket. In addition, the reaction rates and the neutron spectrum are measured to provide test data for confirmation of calculation results. These data are compared among six different configurations of the experimental system. Consistency between the different techniques for each measured parameter is also tested among different experimental systems. The experimental results are compared with the calculations by DOT 3.5 using JENDL-3/PRI and /PR2. The calculation differs from the experimental data by <10%, except for the beryllium zone.

Integral test of JENDL-3PR1 through benchmark experiments on Li 2O slab assemblies

Abstract Two types of benchmarck experiments on Li 2O assemblies have been carried out. They were analyzed by using three transport codes with JENDL-3PR1 and ENDF/B-4. The calculation using JENDL-3PR1 predicted tritium production rates of 6Li and 7Li better than those using ENDF/B-4.