1992 Fiscal Year Final Research Report Summary
A Research on the Mechanisms of Radiation Embrittlement of Steels
| Project/Area Number |
02452289
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Nuclear engineering
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| Research Institution | University of Tokyo |
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Principal Investigator |
ISHINO Shiori University of Tokyo, Faculty of Engineering, Professor, 工学部, 教授 (70010733)
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| Co-Investigator(Kenkyū-buntansha) |
KAWANISHI Hiroshi University of Tokyo, Faculty of Engineering Research Associate, 工学部, 助手 (40010970)
SEKIMURA Naoto University of Tokyo, Faculty of Engineering Associate Professor, 工学部, 助教授 (10183055)
IWATA Shuichi University of Tokyo, Research into Artifacts, Center for Engineering, Professor, 人工物工学研究センター, 教授 (50124665)
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| Project Period (FY) |
1990 – 1992
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| Keywords | radiation embrittlement of pressure vessel steels / iron-based model alloys / ion irradiation / positron annihilation / S-parameter / copper effect / copper-vacancy complexes / neutron irradiation |
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| Research Abstract |
Iron based model alloys of which copper and nickel contents are varied have been employed as the specimen. These model alloys were irradiated with 3-4MeV nickel ions from a tandetron and with protons from 3.75MeV van de Graaff at the High Fluence Irradiation Facility of the University of Tokyo (HIT). In parallel with these, neutron irradiations are being carried out using the Japanese Material Testing Reactor (JMTR).
Positron annihilation study in collaboration with Professor Tanigawa's Lab., Institute of Material Science, Tsukuba University was one of the main interests in this fiscal year. The model alloys were irradiated with nickel ions accelerated to 3MeV at 563K.The irradiation dose was 1mdpa at the damage peak depth as calculated by the EDEP-1 code. Monoenergetic positron beams with energies between 0 and 30keV were impinged into the ion-irradiated surface of the sample, and the energy spectrum of the annihilation gamma-rays were detected with a semiconductor detector.These measu
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rements were repeated with various positron accelerating voltages. Each irradiated sample showed the increase of S-parameter in comparison with the unirradiated sample. This may indicate the production of vacancy-type defects. With regard to the effect of the material composition, copper-bearing alloys showed the greater increase of the S-parameter than the alloys containing no copper. Nickel had no effect on the S-parameter increase. It is speculated from the results that there is a strong interaction between copper and vacancies in iron, and that the production of the copper-vacancy complexes occurs. These results were reported at the autumn meeting of the Japan Institute of Metals in October, 1992. Although similar measurements of the 3MeV-proton irradiated samples were attempted, increase of S-parameter was not detected due to the low defect concentration. It seems necessary to increase the irradiation dose or to lower the proton energy for detecting the S-parameter increase caused by proton irradiation.
With regard to the neutron irradiation at the JMTR,two series of irradiations have already started. One series is the irradiation under varied neutron spectrum, another is the irradiation under two neutron flux levels which differ by one order of magnitude. Post irradiation experiments will begin from next year. The results of the ion irradiation would give the profitable fundamental information for the analyzes of the neutron irradiation data. Less
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