Kentaro Ochiai

New Production Routes for Medical Isotopes 64Cu and 67Cu Using Accelerator Neutrons

We have measured the activation cross sections producing 64Cu and 67Cu, promising medical radioisotopes for molecular imaging and radioimmunotherapy, by bombarding a natural zinc sample with 14 MeV...

R&D of a Li2TiO3 pebble bed for a test blanket module in JAEA

At JAEA, a test blanket module (TBM) with a water-cooled solid breeder is being developed. This paper presents recent achievements of research activities for the TBM, particularly addressing the pebble bed of the tritium breeder materials and tritium behaviour. For the breeder material, the chemical stability of Li2TiO3 was improved using Li2O additives. To analyse the pebble bed behaviour, thermomechanical properties of the Li2TiO3 pebble bed were assessed experimentally. To verify the pebble beds nuclear properties, the activation foil method was proposed and a preliminary experiment was conducted. To reduce the tritium permeation, the chemical densified coating method was developed and the coating was attached to F82H steel. For tritium behaviour, the tritium recovery system was modified in consideration of the design change of the TBM.

Effect of neutron energy and fluence on deuterium retention behaviour in neutron irradiated tungsten

Deuterium (D) retention behaviours for 14 MeV neutron irradiated tungsten (W) and fission neutron irradiated W were evaluated by thermal desorption spectroscopy (TDS) to elucidate the correlation between D retention and defect formation by different energy distributions of neutrons in W at the initial stage of fusion reactor operation. These results were compared with that for Fe2+ irradiated W with various damage concentrations. Although dense vacancies and voids within the shallow region near the surface were introduced by Fe2+ irradiation, single vacancies with low concentration were distributed throughout the sample for 14 MeV neutron irradiated W. Only the dislocation loops were introduced by fission neutron irradiation at low neutron fluence. The desorption peak of D for fission neutron irradiated W was concentrated at low temperature region less than 550 K, but that for 14 MeV neutron irradiated W was extended toward the higher temperature side due to D trapping by vacancies. It can be said that the neutron energy distribution could have a large impact on irradiation defect formation and the D retention behaviour.

Measurement of tritium production rate in water cooled pebble bed multi-layered blanket mockup by DT neutron irradiation experiment

For the first time, tritium production rates in the water cooled pebble bed blanket are experimentally examined by using DT neutrons with two partial mockups; multi-layered mockup with water and pebble bed mockup. Tritium production rates (TPRs) are calculated by numerical analyses using Monte Carlo code MCNP-4C with nuclear data libraries FENDL-2.1 and JENDL-3.3. For experimental analysis on the pebble bed mockup, precise modelling method is proposed using the hexagonal close-packed heterogeneous geometry. Prediction uncertainties of TPRs are clarified through the experimental analyses. Ratios of the calculation results to the experimental results on local TPRs are 0.89–1.10 in the multi-layered mockup, and 0.95–1.13 in the pebble bed mockup. The calculation results on integrated tritium productions agree well with the experimental ones in both mockups. It is clarified that integrated tritium productions can be accurately evaluated.

Successful labeling of 99mTc-MDP using 99mTc separated from 99Mo produced by 100Mo(n,2n)99Mo

We have for the first time succeeded in separating 99m Tc from a MoO 3 sample irradiated with accelerator neutrons free from any radioactive impurities and in formulating 99m Tc-methylene diphosphonate ( 99m Tc-MDP). 99 Mo, the mother nuclide of 99m Tc, was produced by the 100 Mo( n ,2 n ) 99 Mo reaction using about 14 MeV neutrons provided by the 3 H( d , n ) 4 He reaction at the Fusion Neutronics Source of Japan Atomic Energy Agency. The 99m Tc was separated from 99 Mo by sublimation and its radionuclide purity was confirmed to be higher than 99.99% by γ-spectroscopy. The labeling efficiency of 99m Tc-MDP was shown to be higher than 99% by thin-layer chromatography. These values exceed the United States Pharmacopeia requirements for a fission product, 99 Mo. Consequently, a 99m Tc radiopharmaceutical preparation formed by using the mentioned 99 Mo can be a promising substitute for the fission product 99 Mo, which is currently produced using a highly enriched uranium target in aging research reactors. A ...

Neutronics Experiments Using Small Partial Mockups of the ITER Test Blanket Module with a Solid Breeder

Abstract In order to evaluate the impacts of the incident neutron spectrum and the tungsten armor on the tritium production, integral experiments have been performed with small partial mockups relevant to the ITER test blanket module using DT neutrons at FNS of JAERI. The Monte Carlo calculation results for the integrated tritium productions agree well with the experimental data within 2 and 11 % for the mockups without the armor in the experiments without and with the neutron reflector, respectively. It is clarified that the tritium production can be very accurately predicted in the experiment without the reflector. In the mockups with the 12.6 and 25.2 mm thick tungsten armors, it is experimentally clarified that the integrated tritium productions are reduced by 3 and 6 % relative to the case without the armor, respectively.

Progress in development of the neutron profile monitor for the large helical device.

The neutron profile monitor stably operated at a high-count-rate for deuterium operations in the Large Helical Device has been developed to enhance the research on the fast-ion confinement. It is composed of a multichannel collimator, scintillation-detectors, and a field programmable gate array circuit. The entire neutron detector system was tested using an accelerator-based neutron generator. This system stably acquires the pulse data without any data loss at high-count-rate conditions up to 8 × 10(5) counts per second.

Methods for tritium production rate measurement in design-oriented blanket experiments

Direct and indirect methods have been developed for measurements of tritium production rates on different Li isotopes. The methods are mainly intended for design-oriented blanket experiments and are based on the activation of thin diagnostic pellets. In the direct method, the tritium activity bred from Li isotopes can be evaluated separately using two activated Li-containing pellets, measured by liquid scintillation counting. The method allows precise measurements of tritium activity in the pellet at a level of 2 Bq/g. The indirect method is based on the use of model activation reactions, 35Cl(n,α)32P and 31P(n,γ)32P, that possess a similar neutron spectrum sensitivity as direct tritium production reactions on 7Li and 6Li, respectively, and an effective measurement of the activation product of model reactions, 32P, by Cherenkov radiation counting. The reaction rate of model reactions can be calibrated in order to obtain the TPR.

Measurement and Analysis of Neutron-Induced Alpha Particle Emission Double-Differential Cross Section of Carbon at 14.2 MeV

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 play an important role in generating the experimental double-differential cross section both of emitted α-particles and neutrons. The estimated ratio of the 12C(n,α)9Be* channels was approximately 40%, somewhat larger than those evaluated in previous studies.

Development of CAD-to-MCNP Model Conversion System and Its Application to ITER

Abstract We developed a conversion system from three-dimensional computer-aided design (CAD) drawing data to MCNP geometry input data. This system consists of programs of “void creation” and “conversion into MCNP input data.” By using this system, it is possible to convert large and complicated CAD drawing data such as a fusion reactor into MCNP geometry input data. We applied this system to ITER CAD drawing data and created MCNP input data for ITER nuclear analysis. We calculated the neutron flux and nuclear heating using this input data. The calculation results agreed well with those by the other parties participating in this ITER research and development.