Research and Development of Long-life Target for Spallation Neutron Source

本研究从材料生产到优化靶系研制，选择钨作为高中子性能、长寿命的靶材作为MW级高功率散裂中子源的候选材料。主要研究结果如下：(1)靶材生产：采用粉末冶金技术，研制出由钨和不锈钢组成的新型重金属，目的是研制一种高韧性、高耐蚀性的钨合金。其热性能不如预期，但该技术对粉末冶金有很大的指导意义。(2)包覆技术：包复金属对钨靶具有良好的耐腐蚀性。开发了热等静压、钎焊和熔盐电化学法三种制备方法。建立了热等静压方法的发展，并成功地应用于更新靶模…的钨靶块的制备高能加速器研究机构KENS的更多反射器-反射器组件。材料性能测试：考察了各种钨合金和靶材的材料性能。特别是，腐蚀试验提供了许多科学上有趣的数据：温度和水流的参数依赖关系，以及用于解释腐蚀机理的数据。(4)应用计算机模拟研究了固体靶的核和热工水力研究：中子和热工水力。设计了兆瓦级散裂中子源的固体靶系统，其性能优于2兆瓦以下的液体靶系统。作为补充，进行了热工水力学实验，对已用于设计的关联式进行了评估。(5)材料辐照效应研究：靶材受到高能质子和中子的严重照射，辐射损伤将决定靶材的寿命。我们参与了国际合作实验(STIP实验)，将放置在PSI(瑞士波利谢勒研究所)SINQ装置散裂靶上的靶材料照射并将许多钨合金、铂和结构材料的样品送到那里。现在，这些样品正在接受辐照。STIP实验的辐照样品将于2005年和2007年归还。因此，即使在科学研究补助金(A)(1)之后，我们也要继续研究，进行辐照后的实验。此外，对于加速器驱动系统将长寿命核废料同位素转化为较短核素和聚变反应堆的更高功率散裂源来说，迫切需要新的抗辐射材料。计划进一步研究建立开发新材料的技术、熔覆技术等。较少

This research has been made by selecting tungsten as a candidate of target materials having a high neutron performance and a long life for MW-class high power spallation neutron source in the wide field covering from material production to optimum target system development. The main results are as follows :(1) Target material production : New heavy metal composed of tungsten and stainless steel was developed by means of powder metallurgical technique, aiming at developing a high tough and corrosion-resistant tungsten alloy. Its thermal property was not as expected but the technique will be much instructive for powder metallurgy.(2) Cladding technique : Tantalum clad gives a corrosion-resistance to tungsten target. Three kinds methods such as hot-isostatic press method, brazing technique and molten-salt electro chemical method were developed. The development of HIP method has been established and successfully applied to fabrication of the tungsten target block for renewal of target-mode … More rator-reflector assembly of KENS at High Energy Accelerator Research Organization. The latter two methods were examined and their applicability was confirmed.(3) Measurement of material properties : Material properties of various tungsten alloys and target materials were investigated. Especially, corrosion tests gave a lot of scientifically interesting data : parameter dependence on temperature and water flow and data for interpretation of corrosion mechanism.(4) Nuclear and Thermo-hydraulic study of solid target : Neutron and Thermo-hydraulic performance was studied by applying computer simulation. The solid target system for MW-class spallation neutron source was designed and its performance was clarified to be superior to that of liquid target system up to 2 MW. As a complemented study, thermo-hydraulic experiments were made to evaluate the correlation formula to have been used for designs.(5) Study on material irradiation effects : Target is heavily exposed by high-energy protons and neutrons, and radiation damage will determine the target life. We have participated in the international collaboration experiments (STIP Experiments) to irradiate the target materials put in the spallation target of SINQ facility at PSI (Polly-Sheller Institute in Switzerland) and send the many specimen of tungsten alloys, platinum and structural materials to there. Now, the specimens are under irradiation.The irradiated specimen of the STIP Experiments will be returned in 2005 and 2007. Therefore, we have to continue the research to make post irradiation experiments even after this Grant-in-Aid for Scientific Research (A) (1). Additionally, new irradiation-resistant material is urgently needed for higher power spallation sources for the Accelerator-Driven System to transmute long-lived nuclear waste isotopes to shorter nuclides and for fusion reactor. Further research is planed to establish the techniques to develop new materials, cladding technique and so on. Less