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Abstract: Lithium in a breeding blanket is burned up through neutron nuclear reactions in fusion DEMO reactors. Effects of decrease of solid breeder materials due to lithium burn-up on tritium breeding ratio (TBR) are not systematically calculated in the past. For the SlimCS blanket design, TBR is calculated taking into account the lithium burn-ups by one dimensional Sn radiation transport calculation code ANISN in this study. The 6Li burn-ups are 8–79% after 10-year operation. TBR due to 6Li decreases to 40% of the initial one in some layer, while it increases in some layers. The TBR integrated over all the blanket decreases to around 96% of the initial one. The study makes it clear that the reduction of the TBR due to the lithium burn-up is not so large. [Copyright &y& Elsevier]

The stilbene neutron detector which has been used for neutron emission profile monitoring in JT-60U has been improved, to respond to the requirement to observe the high-frequency phenomena in megahertz region such as toroidicity-induced Alfvén Eigen mode in burning plasma as well as the spatial profile and the energy spectrum. This high-frequency phenomenon is of great interest and one of the key issues in plasma physics in recent years. To achieve a fast response in the stilbene detector, a Flash-ADC is applied and the wave form of the anode signal stored directly, and neutron/gamma discrimination was carried out via software with a new scheme for data acquisition mode to extend the count rate limit to MHz region from 1.3×105 neutron/s in the past, and confirmed the adequacy of the method. [ABSTRACT FROM PUBLISHER]

Magnetic coils are indispensable for plasma position control in tokamaks. For ITER, non-inductive voltages generated under irradiation have to be reduced to well below 1 μV in order to support long pulse (3000 s) operation. In situ measurements of the differential voltage between the ends of two magnetic coils wound with mineral-insulated (MI) cable have been carried out at the JMTR fission reactor. The MI cables of the two magnetic coils had copper center conductor with diameter 0.5 and 0.8 mm, respectively, stainless steel outer sheath and MgO insulation. The measured differential voltage for the two MI cables increased with neutron fluence, reaching 4.5 and -0.7 μV in the two coils, at a fast neutron fluence of 1.26 × 1023 n/m2. The magnitude of the measured voltage can be explained by thermoelectric potentials, enabled mainly by non-uniform transmutation and displacement damages of the copper core of the cable. [Copyright &y& Elsevier]

Describes the development of a vacuum sealing method on a V-shaped elastic ring for the International Thermonuclear Experimental Reactor (ITER) diagnostic windows. Compression of the ring by two valves; Examination of the performance of the seals to inner pressure rise resistance, heat cycle and acceleration at the level expected in the ITER environment.

Describes the design of microfission chambers and gas counters with fissile material inside, to be installed in the vacuum vessel as neutron flux monitors for the International Thermonuclear Experimental Reactor. Computation of the neutron and gamma flux around the shielding blanket; Unsuitability and problems of the [sup 238]U microfission chambers.

Describes the design of the divertor impurity monitoring system of the International Thermonuclear Experimental Reactor. Main functions of the system; Wavelength range; Three different types of spectrometer; Optimization of the optics by a ray trace analysis.

Analyzes the expected performance of several neutron camera arrangements for the International Thermonuclear Experimental Reactor. Examination of proposed cameras wherein neutron fluxes are inferred from [sup 16]N decay gammas in dedicated flowing water loops; Accuracy of the measurements; Sufficiency of the spatial sampling provided by the reference designs.

Describes the design of a radial neutron spectrometer using a type deuterium-tritium neutron spectrometer base on a recoil proton counter-telescope technique aiming ion temperature measurement for the International Thermonuclear Experimental Reactor. Installation of the neutron spectrometer on the well collimated neutron beam line; Monte Carlo calculation.

Discusses neutron diagnostic techniques for the control and evaluation of thermonuclear plasmas in an ignition device to test engineering concepts, the International Thermonuclear Experimental Reactor (ITER). Principal features of the ITER design; Neutron flux monitors; Neutron activation system; Radial and vertical neutron cameras.

Microfission chambers (MFCs) will measure the total neutron source strength in ITER. The MFCs will be installed behind blanket modules in the vacuum vessel (VV). Triaxial mineral insulated (MI) cables will carry signals from the MFCs. The joint connecting triaxial MI cables in the VV must be considered because the MFCs and the MI cables will be installed separately at different times. Vacuum tight triaxial connector of the MI cable has been designed and a prototype has been constructed. Performance tests indicate that the connector can be applied to the ITER environment. A small bending-radius test of the MI cable indicates no observed damage at a curvature radius of 100 mm. [ABSTRACT FROM AUTHOR]

A ³He ionization chamber was used to measure neutron spectra on TFTR during 1987. The ion temperature was deduced for one set of Ohmically heated plasmas and agreed within 20% with that measured by other diagnostics. The absolute efficiency was calibrated using a d-d neutron generator. [ABSTRACT FROM AUTHOR]

Examines the irradiation effects on potential diagnostic materials and components of the International Thermonuclear Experimental Reactor. Radiation-induced electrical damage and conductivity in potential insulators; Radiation-induced absorption and radio luminescence in potential optic materials; Changes to reflectivity and surface properties of bulk metal mirrors.

Abstract: We developed a CAD/MCNP interface program prototype to easily perform Monte Carlo fusion nuclear design calculation with high accuracy using detailed calculation geometry. Usually, there is only CAD data on the solid region. However, CAD void region data must be input to MCNP. Our newly developed CAD/MCNP interface program creates the void region data automatically. The void region data is created by subtracting the solid region data using Boolean operations. The program has also the function of uniformly dividing the overall data into small cubes to simplify the void region data. It has been applied to create 3D CAD data in the ITER benchmark model. It was demonstrated that data of the void region in the ITER model were successfully created using our program. [Copyright &y& Elsevier]

Abstract: SlimCS is the conceptual design of a compact fusion DEMO plant assuming technologies foreseeable in 2020–2030s. For continuity of blanket technology from the Japanese ITER-TBM, the prime option of blanket is water-cooled solid breeder with Li2TiO3 (or Li4SiO4) and Be. A reduced-activation ferritic–martensitic steel (RAFM) and subcritical water are chosen as the structural material and coolant, respectively. The reactor has somewhat complex torus configuration with a sector-wide conducting plate slipped in between the replaceable (front) and permanent (back) blanket. In order to allow flexibility of maintenance in such a complex configuration, sector transport hot cell maintenance scheme is adopted. This paper describes characteristics of SlimCS with a focus on materials selection. [Copyright &y& Elsevier]

Abstract: A series of breeding blanket neutronics experiments were carried out with DT neutrons in the Japanese ITER test blanket module at JAEA Fusion Neutronics Source (FNS), and tritium production rates (TPRs) inside different blanket mock-ups were measured in detail. Most of calculations made using FENDL-2.1 and MCNP agreed well with the measured TPRs. On the other hand, there were overestimations of the calculation for the TPR in the experiment with a reflector and the TPR around the boundary between the rear part of the breeder layer and the beryllium in the pebble bed mock-up experiment. In this study, we investigated the possibility of improvement of the calculation by modifying the part of angular distributions in backward directions in FENDL-2.1. By uniformly decreasing the backward elastic scattering cross-sections of 56Fe by 20% below the original data for incoming neutrons in the energy range from 0.5234MeV up to 15.0MeV, the overestimation of the calculations for the TPR in the enriched breeding blanket experiment with a reflector was reduced. Also, by uniformly decreasing the backward elastic scattering cross-sections of 9Be by 20% and 30% below the original data for the incoming neutrons in the energy range from 0.93MeV up to 14.94MeV, and by 20% for those from 0.62MeV up to 14.94MeV, the overestimation of the calculations for the TPR around the boundary between the rear part of the breeder layer and the beryllium was lessened. [Copyright &y& Elsevier]

Abstract: Sequential charged particle reactions, that is, reactions induced by secondary charged particles generated due to neutron reactions, may cause non-negligible radioactivity in low activation material. A computer code ACT4, which had been developed to calculate radioactivity, decay heat and gamma ray source for fusion reactors was supplemented an ability to deal with the reactions. Experiments conducted with Fusion Neutronics Source in Japan Atomic Energy Research Institute for the radioactivity by sequential charged particle reactions were analyzed with the newly revised code of ACT4. As the result, the activations via sequential reaction in LiF showed reasonable agreement with experimental data, which means that the ACT4 program will work well. However, the other activations in vanadium and low activation ferritic steel did not. The disagreement must be caused by incorrectness in neutron cross sections, charged particle cross sections, charged particle emission spectra, etc., and they need to be fully reviewed for the detailed and reliable design analysis of fusion reactors. [Copyright &y& Elsevier]

Abstract: For the evaluation of the damages, nuclear heating, and also tritium inventory in the fusion materials, the precise information of the energetic charged particles produced in the materials by nuclear reactions is important. Fusion neutronics source in Japan Atomic Engineering research Association, JAERI/FNS, has started the measurements of the double differential cross-sections (DDXs) and the angular differential cross-sections (ADXs) for the candidate materials of fusion reactors using the collimated D–T neutron beam system and the precise results of the DDXs and ADXs for the 9Be(n,αx) and 9Be(n,t) reactions have been obtained. Also, from the comparison of the evaluated nuclear data for the beryllium, it was found that the calculated DDX of 9Be(n,α) above about 3MeV was underestimated and the total 9Be(n,t) cross-section obtained with the measurement of the DDX and ADX was in good agreement with the evaluated nuclear data. In the following sections, the details of the measurement methods for the charged particles and the obtained DDX and ADX for the beryllium are described. [Copyright &y& Elsevier]

This paper addresses the particular need to develop suitable fabrication techniques of glasses to improve the radiation-resistance and extend the lifetime of optical fibres in high radiation background. Two radiation hardening techniques based on hydrogen and fluorine doping of glass have been applied on step index pure silica core optical fibres. The radiation-induced optical absorption and luminescence have been measured in gamma and fission reactor irradiation conditions at SCKCEN, Mol Belgium. The experimental results show that the lowest optical absorption is achieved in the hydrogen-treated fibre sample. However, the luminescence effect remains significant in any type of fibre and cannot be reduced by the investigated radiation hardening techniques. [Copyright &y& Elsevier]

This paper presents an overview of ITER-supporting materials R&D activities and major achievements in Japan during the period from the Co-ordinated Technical Activities to date. In view of the completed engineering design of ITER during the Engineering Design Activities period, R&D efforts since then have been focused on: those for reduction of component fabrication cost; those in support of domestic preparations of a structural technical code for construction; and those necessary for operation, and been extended to component-level testing rather than pure material testing. They cover materials R&D for in-vessel components, vacuum vessel, cryogenic steels of superconducting magnets and diagnostics components. Major achievements in each R&D area are highlighted and their impact or implication to the design, construction and operation of ITER is presented. [Copyright &y& Elsevier]