DETERMINATION OF CORROSIVE CONDITION IN COOLING SYSTEM OF HIGH IRRADIATION DOSE RATE AND HIGH HEAT LOADING COMPONENT AND ESTABLISHMENT OF ITS MODIFICATION TECHNIQUES

大功率加速器靶、核裂变堆和聚变堆冷却系统中结构材料的应力腐蚀开裂（SCC）主要由罐尖周围的局部溶解菌浓度决定。研究的主要目的是确定腐蚀决定物质，确定当地水化学对SCC裂纹扩展速度的影响，从而提出适当的水化学控制措施，例如弱碱控制以减轻SCC。辐照下裂纹尖端局部水化学的测定。在模拟裂纹尖端测量了能量沉积速率。裂纹尖端的水化学性质可以用裂纹辐射分解模型进行理论估计。高温高压过氧化氢（H_2O_2）水循环的设计与构造。H_2O_2的浓度可控制在任意浓度。裂纹扩展速率（CGR）可以测量。辐照条件下CGR的测定CGR…More是在模拟辐照条件下（由H_20O_2浓度控制）进行的。讨论了H_2O_2和o_2_2条件下CGR的差异。结果表明，测定CGR的主要参数是腐蚀电流，而不是电化学腐蚀电位。辐照和弱碱水化学条件下CGR的测定(1)在模拟辐照条件下，pH < 8.5下测量CGR。(2)评价了裂纹尖端pH值对CGR的影响。(1)提出了适宜的G值和反应速率常数设置。(2)提出了包含合适常数集的理论模型。(3)提出了由裂缝辐射分解模型和裂纹扩展模型组成的SCC - CGR评价模型，不仅适用于裂变反应堆冷却系统，也适用于加速器和聚变反应堆冷却系统。(4)弱碱水化学不仅适用于裂变反应堆的冷却系统，也适用于加速器和聚变反应堆的冷却系统。少

Stress corrosion cracking (SCC) of structural materials in cooling systems of high power accelerator targets, nuclear fission reactors and fusion reactors reactor are determined mainly by local concentrations of rodiolytic species around crock tips. Major purposes of the studies are to confirm the corrosion determining species, to determine the effects of local water chemistry on SCC crack growth rate and then so propose suitable water chemistry control, e.g.,weak alkali control for mitigation of SCC.1.Determination of local water chemistry of crack tips under irradiation.Energy deposition rate was measured in a simulated crack tip. Water chemistry in a crack tip could be theoretically estimated with the crevice radiolysis model.2.Design and construction of high temperature high pressure hydrogen peroxide (H_2O_2) water loopThe concentration of H_2O_2 could be controlled at any desired concentration. Crack growth rate (CGR) could be measured.3.Determination of CGR under irradiationCGR … More was measured under simulated irradiation conditions (controlled by H_20O_2 concentration). Difference in CGR under H_2O_2 and O_2conditions was discussed. It was confirmed that the major parameter to determine CGR was corrosion current rather than electrochemical corrosion potential.4.Determination of CGR under irradiation and weak alkali water chemistry(1)CGR was measured under simulated irradiation condition and under pH less than 8.5.(2)The effects of crack tip pH on CGR was evaluated.5.Feed back of measured date to crevice radiolysis model and corrosion condition evaluation procedures for operation plants(1)Suitable sets far G values and reaction rate constants was proposed.(2)Theoretical model containing the suitable constant sets was proposed.(3)SCC CGR evaluation model which consisted of the crevice radiolysis model and the crack growth model, was proposed not only for fission reactor cooling systems but also cooling systems of accelerators and fusion reactors.(4)Weak alkali water chemistry was proposed to prevent SCC not only for fission reactor cooling systems but also cooling systems of accelerators and fusion reactors. Less