CONTROL OF HYDROGEN PEROXIDE CONCENTRATION IN HIGH TEMPERATURE WATER AND DETERMINATION OF ITS EFFECTS ON STRESS CORROSION CRACKING OF STAINLESS STEEL

沸水堆堆内构件的应力腐蚀开裂主要是由高温水中的不稳定辐解物种H_2O_2引起的。本研究的主要目的是建立高温高压H_2O_2水回路，以控制H_2O_2的浓度，并使O_2共存最少，以确定H_2O_2对SCC裂纹扩展速率的影响，然后提出一个腐蚀条件指数来确定反应堆堆内构件的剩余寿命.基于鲁米诺荧光的流动池型过氧化氢检测器的研制.高温高压H_2O_2水回路的设计与施工.电化学腐蚀电位（ECP）与裂纹扩展速率（CGR）关系的测定. (1)测定了ECP和CGR随H_2O_2和O_2浓度的变化关系。(2)在H_2O_2条件下，得到了高抗氧化性的富赤铁矿氧化膜。(3)考察了表面性质对氧化剂浓度、ECP和CGR关系的影响.基于理论估计和测量结果的比较，确定测量结果的合理性。(1)根据水辐解分析得到的H_2O_2浓度，对ECP和CGR进行了理论评价。(2)对于（1）中所示的模拟腐蚀条件测量ECP和CGR。(3)通过比较结果（1）和（2）证明评价程序的合理性。(4)讨论了ECP和CGR评价程序在电厂应用的未来课题.反应堆内构件新定义腐蚀指数的推导。(1)反应堆内构件新定义腐蚀指数的建议。(2)腐蚀指数和弱碱控制在日本BWR堆内构件SOC降低中的积极应用及其对剩余寿命评估的改进。

Stress corrosion cracking (SCC) of BWR reactor internals are determined mainly by hydrogen peroxide (H_2O_2), an unsteady radiolytic specie in high temperature water. Major purposes of the studies are to construct high temperature high pressure H_2O_2 water loop which can control H_2O_2 concentration with minimal O_2 co-existence, to determine the effects of H_2O_2 on SCC crack growth rate and then to propose an index for corrosive condition to determine residual lifetime of reactor internals.1. Development of a flow cell type hydrogen peroxide detector based on luminol chemiluminescence.2. Design and construction of high temperature high pressure H_2O_2 water loop.3. Determination of relationship of electrochemical corrosion potential (ECP) and crack growth rate (CGR).(1) The relationship between ECP and CGR as a function of H_2O_2 and O_2 concentrations was determined.(2) High resistant hematite rich oxide film was confirmed under H_2O_2 condition.(3) The effects of surface properties on the relationship of oxidant concentration, ECP and CGR were evaluated.4. Justification of the measured result based on comparison of theoretical estimation and measurement.(1) ECP and CGR were evaluated theoretically based on H_2O_2 concentration obtained water radiolysis analysis.(2) ECP and CGR were measured for simulated corrosive conditions shown in (1).(3) Evaluation procedures was justified by comparing the results (1) and (2).(4) Future subject for application of ECP and CGR evaluation procedures to power plants were discussed.5. Derivation of newly defined corrosion index for reactor internals.(1) Proposal of newly defined corrosion index for reactor internals.(2) Positive application of the corrosion index and weak alkali control to mitigate SOC of reactor internals in Japanese BWRs and their improvement for residual lifetime evaluation.