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AbstractThe current status and the progress of research and development (R&D) activities for a Fusion DEMO reactor in the National Institutes for Quantum and Radiological Science and Technology (QST) Rokkasho Fusion Institute is reported. In order to advance the Japanese DEMO activity, not only Japanese domestic activity but also international collaborations of Broader Approach activity and ITER-related activities are conducted in the QST Rokkasho Fusion Institute. Activities for DEMO design and relevant R&D; design of a fusion neutron source and development of an accelerator, ITER Test Blanket System; tritium handling technology; and information technology infrastructures, including a supercomputer system and a remote experimentation system, are carried out for a Fusion DEMO reactor.

AbstractThe diameter of pressurized tubes of F82H and B-doped F82H irradiated up to ~6 dpa have been measured by a non-contacting laser profilometer. The irradiation creep strains of F82H irradiated at 573 and 673K were almost linearly dependent on the effective stress level for stresses below 260 MPa and 170 MPa, respectively. The creep strain of 10BN-F82H was similar to that of F82H IEA at each effective stress level except 294 MPa at 573K irradiation. For 673K irradiation, the creep strain of some 10BN-F82H tubes was larger than that of F82H tubes. However, the generation of ∼300 appm He did not cause a large difference in the irradiation creep behavior at 6 dpa.

AbstractTo improve the fatigue properties evaluation of the joint region of the fusion reactor blanket, the effect of the non-uniform distribution of the microstructure and strength on the fatigue properties of the electron beam weld joint of the F82H steel was investigated by the fatigue test and the numerical simulation of the deformation under the test. The fatigue life of the joint was approximately 10–20 % of that of the base metal. The fracture under the fatigue test occurred around the over-tempered heat affected zone (the region with the lowest hardness). One of the reasons of the shorter fatigue life of the joint could be the higher crack growth rate induced by the peak strain around the over-tempered heat affected zone due to the non-uniform deformation.

When fusion welding is conducted on the dissimilar materials between a reduced activation ferritic/martensitic steel F82H steel and an austenite stainless steel SUS 316 steel, δferrite is generally formed and inevitably deteriorates the weld properties. In this study, dissimilar welding of F82H to SUS 316 steel was successfully achieved by friction stir lap welding technique. It revealed that the shape and microstructure of the joint interface can be controlled by controlling the welding temperature, in another word, by changing the applied load. By controlling the welding temperature at ∼710°C, a sound dissimilar joint can be obtained with a smooth joint interface and no mixed microstructure, despite the relative overlapping position of the steel plates. All the dissimilar joints showed high shear tensile strength and fracture in the base metal of F82H steel plate, which has lower strength than the SUS 316 steel plate at room temperature.

AbstractA toughness-improved type of F82H steel called F82H mod3 has been developed, and the material properties and irradiation behavior have been examined. The significant modification of the chemical composition is the reduction of Ti (<10 ppm) and N (<20 ppm) as impurities and the increase of Ta (0.1%) as an alloying element. The ductile-to-brittle transition temperature (DBTT) is improved to -90°C from -45°C for F82H IEA without change in strength. However, the creep rupture time of F82H mod3 was 1/10 of F82H IEA. Another feature of the F82H mod3 is the stability of the material properties. Higher temperature normalization (1080°C) degrades the DBTT only to -80°C due to grain coarsening without large change in strength. It is quite important for large-scale production of the material in high quality. Preliminary neutron irradiation experiments up to 17 dpa showed better irradiation resistance to changes in fracture toughness than F82H IEA.

Dissimilar metal electron beam welding with reduced activation ferritic/martensitic steel, F82H IEA heat, and SUS316L austenitic stainless steel was studied. Mechanical property evaluation at room temperature by bend test, tensile test, Vickers hardness measurement and charpy impact test, and evaluation of irradiation hardening by proton irradiation at 300°C up to 0.5 dpa were carried out. The mechanical properties of the dissimilar weld were improved by the optimization of the electron beam position in the welding (shifted 0.2 mm on 316L side) and the post-weld heat treatment (PWHT) (750°C x 1 hour). The improvement of the mechanical properties might be due to the fact that the weld metal consisted of the austenitic phase. Smaller irradiation hardening than 316L was observed in the weld metal of the F82H/316L dissimilar weld after PWHT at 750°C for 1 hour, where the electron beam was shifted 0.2 mm on 316L side, though the formation of voids and dislocation loops occurred in the grain matrix of the weld metal.

This paper presents the significant progress made in the research and development (R&D) of key technologies on the water-cooled solid breeder blanket for the ITER test blanket modules in JAERI. Development of module fabrication technology, bonding technology of armours, measurement of thermo-mechanical properties of pebble beds, neutronics studies on a blanket module mockup and tritium release behaviour from a Li2TiO3pebble bed under neutron-pulsed operation conditions are summarized.

AbstractIn order to determine the contributions of different microstructural features to strength and to deformation mode, microstructure of deformed flat tensile specimens of irradiated reduced activation F82H (IEA heat) base metal (BM) and its tungsten inert-gas (TIG) weldments (weld metal and weld joint) were investigated by transmission electron microscopy (TEM), following fracture surface examination by scanning electron microscopy (SEM). After irradiation, the fracture surfaces of F82H BM and TIG weldment showed a martensitic mixed quasi-cleavage and ductile-dimple fracture. The microstructure of the deformed region of irradiated F82H BM contained dislocation channels. This suggests that dislocation channeling could be the dominant deformation mechanism in this steel, resulting in the loss of strain-hardening capacity. While, the necked region of the irradiated F82H TIG, where showed less hardening than F82H BM, showed deformation bands only. From these results, it is suggested that the pre-irradiation microstructure, especially the dislocation density, could affect the post-irradiation deformation mode.

ABSTRACTPrevious work reported that a TIG weld joint of F82H exhibited low irradiation hardening in a tensile test, compared to the base metal. Microhardness tests and microstructure observation on the neutron-irradiated TIG weld joint of F82H revealed that the over-tempered zone in the heat-affected zone (HAZ) exhibited this good performance. The region in the HAZ where the prior austenite grain size became very fine during welding also exhibited lower irradiation hardening. Hypotheses for these low-hardening mechanisms were proposed based on the phase diagram and grain size.

ABSTRACTThe effects of irradiation up to 20 dpa on the Charpy impact properties of reduced-activation ferritic/martensitic steels (RAFs) were investigated. The ductile-brittle transition temperature (DBTT) of F82H-IEA shifted up to around 323K. TIG weldments of F82H showed a fairly small variation on their impact properties. A finer prior austenite grain size in F82H-IEA after a different heat treatment resulted in a 20K lower DBTT compared to F82H-IEA after the standard heat treatment, and that effect was maintained even after irradiation. Helium effects were investigated utilizing Ni-doped F82H, but no obvious evidence of helium effects was obtained. ORNL9Cr-2WVTa and JLF-1 steels showed smaller DBTT shifts compared to F82H-IEA.

The combination of charged particle irradiation using MeV energy range accelerators and an ultra-low load indentation is a potential technique to study the mechanical property changes of fusion structural materials due to high-energy neutron irradiation. This work was intended to examine the contribution of various defects to irradiation-induced hardening in an Fe–15Cr–20Ni model alloy by means of single/dual-beam ion irradiation and a micro-indentation. In single/dual ion-irradiated specimens, a significant reduction in Frank loop number density was observed in a region where indentation-induced dislocations evolved. It was observed that only Frank loops with diameters of about 20 nm partially survived in the plastically deformed region. In the dual ion-irradiated specimens, cavities shear-deformed along the mass-flow directions were observed in the region beneath the indent. It was concluded through the indentation hardness determination and post-irradiation indentation micro-structural examination that small Frank loops cause hardening to a larger extent than expected from their actual sizes and induce plastic instability by annihilating by interactions with moving dislocations, while clean cavities produced by ion irradiation are not strong deformation barriers as estimated from neutron data.

To cast light on tumorigenesis in the remnant stomach after distal gastrectomy for peptic ulcer or gastric cancer, 45 cases in gastroduodenostomy (Billroth I, 17 cases) and gastrojejunostomy (Billroth II, 28 cases) groups were compared for a series of parameters. Cancers in Billroth II were significantly more predominant in the anastomosis area and more frequently associated with Epstein-Barr virus infection. Active gastritis, accelerated epithelial cell turnover (as assessed by measurements of apoptosis and cell proliferation), DNA damage, and foveolar cell hyperplasia were all greater in anastomotic areas after Billroth II than in proximal areas after Billroth II or either area after Billroth I. K-ras mutations were rare, but Epstein-Barr virus infection in cancers was seen frequently in anastomosis cases. In conclusion, active gastritis, possibly induced by enterogastric reflux, is linked to tumorigenesis in anastomosis sites in Billroth II cases.

A new type of common path interferometer using a modified zone-plate developed for testing aspheric surfaces is described. The modified zone-plate is made by combining two kinds of zone-plates; the semicricular part of the plate produces the spherical wave, and the remainder the desired aspheric wave. These are synthesized by digital computation. A method of computation for synthesizing the modified zone-plate and some experimental results of the test of parabolic mirrors are given.

The carcinogenicity of N-carboxymethyl-N-nitrosourea (CMNU), a naturally occurring N-nitroso compound, was tested in female Donryu rats. Four groups of female Donryu rats were given 400, 200, 100, or 0 ppm of CMNU solution continuously as drinking water. The incidence of tumors was highest and the mean survival time shortest in the 400 ppm group. A dose-effect relationship was observed in the tumor incidence and the mean survival time and the incidences of tumors in all experimental groups were significantly different from those in the control group. In the 400 ppm group, tumors were detected most frequently in the small intestine, followed by the mammary gland. In contrast, most tumors were observed in the mammary gland in the other two experimental groups, although dose-dependent induction of tumors of the small intestine was also detected in these two groups. The organ specificity of CMNU is compared with that of other N-alkyl-N-nitrosourea derivatives.

The carcinogenic potential of triethanolamine was examined in F344 rats. Triethanolamine was dissolved in distilled water at levels of 0 (control), 1, and 2%, and groups of 50 males and 50 females were given these doses ad libitum as drinking water for 2 yr. The dose levels in females were reduced by half from wk 69, because of associated nephrotoxicity. A variety of tumors developed in all groups, including the control group, and alt tumors observed were histologically similar to spontaneous tumors in this strain of rats. No statistically significant increase of the incidence of any tumor was observed in the treated groups of both sexes by the chi-square test. In this study, however, there was an increase in nephrotoxicity, which appeared to have an adverse effect on the life expectancy of the treated animals, especially of females. Therefore, an age-adjusted statistical analysis on incidences of main tumors or tumor groups of both sexes was also done by methods recommended by Peto et al. (1980). The result showed that a positive trend (p < 0.05) was noted in the occurrence of hepatic tumors (neoplastic nodule/hepatocellular carcinoma) in males and of uterine endometrial sarcomas and renal-cell adenomas in females. These tumors, however, have been observed spontaneously in this strain of rats, and their incidences in the control group of the present study were lower than those of our historical controls. These results may indicate that a positive trend in the occurrence of these tumors is not attributable to triethanolamine administration. Increased incidence of renal tumors in the female high-dose group may have been connected with renal damage. Histological examination of renal damage observed in the treated groups, especially in the female high-dose group, revealed acceleration of so-called chronic nephropathy. In addition, mineralization of the renal papilla, nodular hyperplasia of the pelvic mucosa, and pyelonephritis with or without papillary necrosis were also observed. Thus, it is concluded that under these experimental conditions triethanolamine is not carcinogenic in F344 rats but is toxic to the kidneys.

Male and female F344 rats were continuously administered N-methyl-N-nitrosourea (MNU) in their drinking water at concentrations of 200 or 100 ppm, and both sexes of ACI/N rats were given MNU at a concentration of 200 ppm. By the 42nd week of the experiment, high incidences of brain/spinal cord tumors were observed in both strains of rats. Histologically, many of them were astrocytomas or anaplastic astrocytomas. In addition, malignant neurinomas were also detected in the spinal nerve roots and trigeminal nerves, although their incidences were rather low. There was no difference in the type and incidence of these neurogenic tumors between the two strains of rats. Tumors of the tongue and esophagus were mainly observed in the high-dose group of F344 rats and those of the glandular stomach were observed in the low-dose group of F344 rats. In ACI/N rats, tumors of the heart and renal pelvis were detected. The organ-specific carcinogenicity of MNU in these two strains of rats was compared with that of MNU in Donryu rats. It was demonstrated that organ specificity of MNU given orally was influenced not only by the strain of rats but also by the dose level.

A SiC/SiC composite is an attractive candidate material but it is a challenge to apply it to the practical components because of the inherent brittle-like failure and structural anisotropy. This study aims to evaluate the failure behavior of SiC/SiC composites by various test modes. Comparison between tensile and compressive strengths revealed the clear axial anisotropy of failure strength. The in-plane shear strength by the off-axial tensile method is invalid unless considering the mixed failure modes. Alternatively, it was demonstrated that the in-plane shear strength can successfully be obtained by the Iosipescu method. The true inter-laminar shear strength can be identified by the diametral compression method.

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are investigated in connection with their application to optical data storage media.

Seventeen examples are given for the copper‐promoted Michael addition of organo‐zinc compounds such as (II), (V) or (VIII) possessing an ester, nitrile or amino acid function to α,β‐unsaturated keto compounds such as (III), (VI) or (IX).