M Uchida

Compatibility between Be12Ti and SS316LN

Abstract Beryllides have good properties and are one of the candidate materials for the neutron multiplier of the DEMO reactor in which good performance is required at 600–800 °C. Therefore, a good compatibility with structural materials is expected for the beryllides. In this study, a compatibility test between Be12Ti and SS316LN was carried out as first step to evaluate the compatibility between beryllides and structural materials. The thickness of the reaction layer between Be12Ti and SS316LN at 800 °C after 1000 h was approximately 30 μm, whereas that of beryllium metal was 300 μm. At 600 °C after 1000 h, the thickness of the reaction layers as to Be12Ti and Be was less than 10 and 100 μm, respectively. The compatibility between Be12Ti and SS316LN was evaluated and Be12Ti was perfectly better than that between beryllium metal and SS316LN at high temperature (600–800 °C). The advantage of beryllides as a neutron multiplier in the Demo reactor was proved.

Improvement of sintered density of Li2TiO3 pebbles fabricated by direct-wet process

Abstract The application of Li2TiO3 pebbles (diameter: 0.2–2 mm, density: 80–85%T.D., grain size:

Tritium release properties of neutron-irradiated Be12Ti

Abstract Be 12 Ti has a high melting point and good chemical stability and is a promising advanced material for the neutron multiplier of the DEMO reactor that requires temperatures higher than 600 °C in a blanket. To evaluate the tritium inventory in the breeding blanket, a tritium release experiment of neutron-irradiated Be 12 Ti with a total fast fluence of about 4×10 20 n/cm 2 ( E >1 MeV) was carried out at 330, 400 and 500 °C. It was clear that tritium could be released easier than from beryllium, and the apparent diffusion coefficient in Be 12 Ti was about two orders larger than that in beryllium at 600–100 °C. In addition to the good tritium release property, the swelling calculated from the density change of the specimens up to 1100 °C in this test was smaller than that of beryllium.

Thermal conductivity of neutron irradiated Be12Ti

Beryllides are expected to be used as the advanced neutron multiplier for the DEMO blanket owing to their peculiar properties like higher melting point, high oxidation resistance, etc. which can improve the blanket design. In this study, thermal conductivity of neutron irradiated Be 12 Ti was measured. The Be 12 Ti specimens were fabricated by HIP process using beryllium and titanium powder, and were irradiated in the JMTR up to a fast neutron fluence (E > I MeV) of 4 × 10 20 n/cm 2 at temperatures of 330, 400 and 500 °C. Thermal diffusivity and specific heat of un-irradiated and irradiated specimens were measured up to 1000 °C by laser flash method. Then, the thermal conductivity was evaluated from these data. The effective thermal conductivity in the pebble bed of fusion blanket was also estimated and interesting prospects for blanket design were obtained.

Preliminary neutronic estimation for demo blanket with beryllide

Abstract In preliminary neutronic assessment was conducted for the design of the DEMO blanket with neutron multiplier and tritium breeder materials packed in a multi-layered area of a blanket container. Beryllium metal and beryllides (Be 12 W, Be 12 Ti, Be 12 V, etc.) are suggested as candidate neutron multiplier materials and material property evaluations of each candidate neutron multiplier materials under neutron irradiation have been carried out. This study estimates the effect of neutron multiplier materials and the effect of the packing configuration on the TBR of the SSTR-based blanket. This work shows that the tritium-breeding ratio (TBR) in a mixed type blanket is about 1.2 times greater than that of separated type blanket. This study shows that TBR of mixed type blanket using Be 12 Ti or Be 12 V will be about 1.2 (required TBR is about 1.3), which is 90% of the TBR for a mixed type blanket using Be. It is concluded that Be 12 Ti and Be 12 V are the most promising neutron multipliers from the view of the tritium breeding.

Elementary development for beryllide pebble fabrication by rotating electrode method

Abstract Beryllides (Be 12 Ti, Be 12 V, etc.) are expected to be promising candidates for advanced neutron multipliers for the DEMO blanket. However, it has been difficult to fabricate beryllide pebbles by rotating electrode method (REM) that is the standard fabrication process for the beryllium (Be) pebbles, because of the brittleness of beryllide electrode rod. In this study, the chemical composition of the materials and the fabrication process of the electrode were surveyed. Then the small-scale electrode was fabricated and preliminary trials of pebbles production were conducted by REM. The electrode of the improved material withstood the thermal stress under arc heating and a certain amount of pebbles were obtained. These pebbles by REM were dense and had fine structure. The feasibility of the production of beryllide pebbles by REM was confirmed.

Heat load test of Be/Cu joint for ITER first wall mock-ups

Abstract Bonding by hot isostatic pressing with an interlayer has been developed as a joining technology of beryllium (Be)/alumina dispersion strengthened copper, a candidate for the ITER first wall. Heat removal and thermal cycle tests with a heat flux of 5 MW/m 2 for 1000 cycles were carried out to evaluate the heat removal performance and the durability of these joints for two types of mock-up that were fabricated with an interlayer of either Al/Ti/Cu or pure Cu. These tests were carried out at OHBIS (Oarai Hot-cell electron Beam Irradiation System) in JAERI. Both mock-ups showed good heat removal performance at conditions simulating the ITER-FEAT operation. It became clear that the interlayer of Al/Ti/Cu excelled pure Cu from the point of cracking at the interface