A Research on the Mechanisms of Radiation Embrittlement of Steels

采用铜和镍含量不同的铁基模型合金作为试样。这些模型合金在东京大学（HIT）的高通量辐照装置（High Fluence radiation Facility）用3-4MeV的镍离子和3.75MeV的范德格拉夫（van de Graaff）质子进行辐照。与此同时，正在利用日本材料试验反应堆（JMTR）进行中子辐照。与谷川教授实验室合作进行的正电子湮灭研究。筑波大学材料科学研究所是本财政年度的主要兴趣之一。模型合金在563K下用加速至3MeV的镍离子辐照。辐照剂量为1mdpa，损伤峰深度按EDEP-1规范计算。将能量在0 ~ 30keV之间的单能正电子束撞击到样品的离子辐照表面，用半导体探测器检测湮灭伽马射线的能谱。在不同的正电子加速电压下重复了更多的测量结果。与未辐照样品相比，每次辐照样品的s参数都有所增加。这可能表明产生了空缺型缺陷。在材料成分的影响下，含铜合金的s参数增大幅度大于不含铜合金。镍对s参数的增加没有影响。由此推测，铜与铁中的空位之间存在很强的相互作用，从而产生了铜-空位配合物。1992年10月，日本金属研究所的秋季会议报告了这些结果。虽然对3mev质子辐照样品进行了类似的测量，但由于缺陷浓度低，没有检测到s参数的增加。为了检测质子辐照引起的s参数增加，似乎有必要增加辐照剂量或降低质子能量。至于在港铁进行的中子辐照，两组辐照已经开始。一个系列是不同中子谱下的辐照，另一个系列是两个中子通量水平相差一个数量级的辐照。辐照后实验将从明年开始进行。离子辐照的结果将为中子辐照数据的分析提供有益的基础信息。少

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 … More 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