Toshihisa Hatano

Design and technology development of solid breeder blanket cooled by supercritical water in Japan

This paper presents results of conceptual design activities and associated RD neutronics experiments and analyses; and development of the blanket module fabrication technology. Upon developing the fabrication technology for the first wall and box structure, a hot isostatic pressing bonded F82H first wall mock-up with embedded rectangular cooling channels was successfully fabricated. It withstood the high heat flux test at 2.7 MW m−2. Also, a correlation parameter of the Li2TiO3 pebble bed made by the sol–gel method was verified by measurement of the thermal conductivity of the breeder pebble bed, which is one of the most important design data.

Optimization of HIP bonding conditions for ITER shielding blanket/first wall made from austenitic stainless steel and dispersion strengthened copper alloy

Abstract Optimum bonding conditions were studied on the Hot Isostatic Pressing (HIP) bonded joints of type 316L austenitic stainless steel and Dispersion Strengthened Copper alloy (DSCu) for application to the ITER shielding blanket / first wall. HIP bonded joints were fabricated at temperatures in a 980–1050°C range, and a series of mechanical tests and metallurgical observations were conducted on the joints. Also, bondability of two grades of DSCu (Glidcop Al-25 ® and Al-15 ® ) with SS316L was examined in terms of mechanical properties of the HIP bonded joints. From those studies it was concluded that the HIP temperature of 1050°C was an optimal condition for obtaining higher ductility, impact values and fatigue strength. Also, SS316L/Al-15 joints showed better results in terms of ductility and impact values compared with SS316L/Al-25 joints.

High heat flux test of a HIP-bonded first wall panel of reduced activation ferritic steel F-82H

Abstract Reduced activation ferritic steel F-82H is a primary candidate structural material of DEMO fusion reactors. In fabrication technology, development of the DEMO blanket in JAERI, a hot isostatic pressing (HIP) bonding method, especially for the first wall structure with built-in cooling tubes has been proposed. A HIP-bonded F-82H first wall panel was successfully fabricated with selected manufacturing parameters. A high heat flux test of the HIP-bonded F-82H first wall panel has been performed to examine the thermo-mechanical performance of the panel including the integrity of the HIP-bonded interfaces and the fatigue behavior. A maximum heat flux of 2.7 MW/m 2 was applied to accelerate the fatigue test up to 5000 cycles in test blanket inserted ITER. The maximum temperature of the panel was ∼450°C under this heat flux. Through this test campaign, no damage such as cracks was observed on the surface of the panel, and no degradation in heat removal performance was observed either from the temperature responses. The thermal fatigue lifetime of the panel was found to be longer than the fatigue data obtained by mechanical testing.

Nuclear and Thermal Analyses of Supercritical-water-cooled Solid Breeder Blanket for Fusion DEMO Reactor

Within a design study of a fusion DEMO reactor aiming at demonstrating technologies of fusion power plant, supercritical water is applied as a coolant of solid breeder blanket to attain high thermal efficiency. The blanket has multi-layer composed of solid breeder pebbles (Li2O) and neutron multiplier pebbles (Be) which are radially separated by cooling panels. The first wall and the breeding region are cooled by supercritical water below and above the pseudo- critical temperature, respectively. Temperature distribution and tritium breeding ratio (TBR) have been estimated by one-dimensional nuclear and thermal calculations. The local TBR as high as 1.47 has been obtained after optimization of temperature distribution in the breeder region under the following conditions: neutron wall loading of 5 MW/m2, 6Li enrichment of 30% and coolant temperature at inlet of breeder region of 380°C. In the case of the higher coolant temperature 430°C of the breeder region the local TBR was reduced to be 1.40. This means that the net TBR higher than 1.0 could be expected with the supercritical-water-cooled blanket, whose temperature distribution in the breeder region would be optimized by following the coolant temperature, and where a coverage of the breeder region is assumed to be 70%.

High heat flux testing of a HIP bonded first wall panel with built-in circular cooling tubes

Abstract A HIP bonded DS-Cu/SS first wall (FW) with built-in circular cooling tubes was fabricated under the optimized HIP conditions. High heat flux testing of the panel was carried out on electron beam facility, JEBIS , at JAERI. The objective of this test is to examine the thermomechanical performance of the panel, including the integrity of the HIP bonded interfaces and also to examine the relation between the design fatigue curve and experimental results. Test conditions applied during these tests were 5.0–7.0 MW/m 2 in average, much higher than the ITER normal operation condition of 0.5 MW/m 2 , to accelerate the fatigue test with a repetition cycle up to 2500 cycles in total. High heat flux tests consisted of two test campaigns. Throughout these tests, no damages such as cracks were observed and no degradation in heat removal performance was also observed from temperature responses measured with thermocouples embedded within the panel. Thermomechanical integrity of the panel was confirmed within the parameter tests and the fatigue lifetime of the panel was found to be much longer than the design fatigue curve of this material, or even beyond the raw fatigue data.

Effective thermal conductivity of a Li2TiO3 pebble bed for a demo blanket

ABSTRACT In development of the ceramic breeder blanket, the effective thermal conductivity of pebble beds is an important design parameter. For thermo-mechanical design of blanket, pebble beds were investigated used for Li2TiO3 that was a candidate for tritium breeder. Li2TiO3 pebble beds, whose size was 0.28-1.91 mm diameter, were measured on load under no neutron irradiation. The effective thermal conductivity was increased with load increasing was obtained.

Development of joining technology for Be/Cu-alloy and Be/SS by HIP

Joining of Be/DSCu and Be/SS by using HIP technique with and without various interlayers were investigated as a screening test for selecting optimum joining method and conditions. Metallurgical observation and shearing tests were performed for basic characterization of the bonded joints. For Be/DSCu, the use of Ag interlayer with 700°C HIP temperature would be a prime candidate if Cd formation under neutron irradiation would not seriously affect plasma operation and joint performance. Other than the Ag interlayer, a Cr/Cu interlayer gave relatively high joint strength in the present screening test. The lower HIP temperature, 550°C, for this joint contributes to prevent sensitization of stainless steel (SS) structural material. As for Be/SS, the highest joint strength was obtained with a Ti interlayer. The HIP temperature of 800°C or a little higher would be applied for this joint to avoid SS sensitization.

Application of HIP bonding to first wall panel fabrication made from reduced activation ferritic steel F82H

Abstract As a course of fabrication technology development of DEMO breeding blankets, fabrication of small-scaled first wall panels made from reduced activation ferritic steel F82H has been attempted by applying HIP (Hot Isostatic Pressing) method. By applying the conditions identified in the previous studies, two flat panels with ten cooling channels each have been fabricated. One of the fabricated panels was destructively tested to examine metallurgically sound HIP bonding and to characterize the change of the micro-structure of the F82H steel due to the HIP process. Destructive examination has confirmed sound bonding for all of the HIP interfaces and satisfactory dimensional tolerance, and applicability of HIP bonding to the complex component made from this steel has been demonstrated.

Fracture strengths of HIPed DS-Cu/SS joints for ITER shielding blanket/first wall

Abstract Fracture toughness and crack propagation tests were performed to investigate the effect of HIP temperature and fracture behavior of HIPed DS-Cu/SS joints. Test specimens of DS-Cu/SS HIPed joints were manufactured by bonding flat plates of DS-Cu and SS under HIP temperatures of 980°C, 1030°C and 1050°C. J Q of the joint at HIP temperature of 1050°C was larger than the other two joints. For the crack propagation test, two types of test specimens were prepared. One had a notch along the HIPed interface and the other in DS-Cu and normal to the interface. The crack in the former specimen propagated along the interface. On the other hand, the crack in the latter specimen propagated in the DS-Cu perpendicular to the loading direction, stopped at the interface, and then exfoliated along the HIPed interface. In the fracture tests, the crack was observed propagating in DS-Cu side at approximately 5–10 μm away from the interface.

Development of first wall/blanket structure by hot isostatic pressing (HIP) in the JAERI

Abstract In the ITER shielding blanket design, first wall coolant tubes of type 316LN stainless steel (SS) are embedded in a heat sink of Al2O3 dispersion-strengthened Cu (DSCu), which are joined to a SS shield block. Development of fabrication technology using hot isostatic pressing (HIP) for this structure, including testing, is currently being performed at JAERI. Recent progress in this development is reviewed in this paper. A simultaneous joining of DSCu/DSCu, DSCu/SS and SS/SS, especially at the first wall and the first wall to the shield block, by a solid HIP technique, has been pursued. Following the optimization of HIP conditions, mechanical tests of the HIP joints and fabrication of first wall mock-ups were performed. High heat flux tests of the first wall mock-ups resulted in their sufficient heat removal capability and integrity of the HIP joints. Small- and medium-scale mock-ups of the shielding blanket, integrated with the first wall, were fabricated to examine the applicability of the HIP technique and develop a fabrication route. As a result of these activities, fabrication technologies and the route to be applied for the ITER shielding blanket and sufficient thermo-mechanical performance of the HIP bonded structure were foreseen.