Corrosion Behavior of Steels Composing an Atomic Power Plant and these Protective Methods

对于具有与原子能发电厂的沸水反应堆（BMR）的一次冷却水系统中的环境类似的环境的装置，准备了在高温高压（HT/HP）下使用的直流型装置（10 ml/min，288 ℃和90 kgf/cm ^2），由储备罐、柱塞泵、预热器、高压灭菌器组成（0.38l，Ti）、冷却器、背压阀等。由市售的JIS SUS 304不锈钢、JIS STPT 410碳钢和敏感处理的不锈钢制备试样。所用添加剂为Zn [Zn（NO_3）_2，ZnSO_4和ZnO]，Al [Al（NO_3）_2，Al_2（SO_4）_3]，Zr [ZrO（NO_3）_2]和Si [Na_2SiO_3]化合物。暴露试验在高温高压水中进行，在100 ppb至1 ppm和1 μ M添加剂浓度和< 5至8000 ppb溶解氧浓度下，进行和不进行预膜处理200至600小时。特别地，发现添加Zr（在不锈钢和碳钢中）和Si（在不锈钢中）化合物的系统中的总腐蚀金属的量（或速率）与非添加剂系统中的那些相比趋于降低。暴露试验后钢表面形成氧化物膜。然后，从辉光放电发射光谱（GDS）、X射线光电子能谱（XPS）、二次离子质谱（西姆斯）等的深度分布数据确认，膜具有由富Fe外层和富Cr内层组成的双层结构。通过各种理化测试的系统评价，认为在含Zr化合物体系中，Zr氧化物提高了膜的保护能力，而在含Si化合物体系中，SiO_3 ~+在钢表面的吸附抑制了CrO_4 ~+的外扩散，从而起到了对钢<2-><2->的保护作用。

As for an apparatus having environment similar to that in a primary cooling water system of boiling water reactor (BMR) of atomic power plant, the once-through type apparatus using at high temperature and high pressure (HT/HP) was prepared (10 ml/min, 288ﾟC and 90 kgf/cm^2) and was composed of reserver tanks, plunger pumps, pre-heater, autoclave (0.38l, Ti), cooler, backpressure valve, etc. Test specimens were prepared from commercially available, JIS SUS 304 stainless steel, JIS STPT 410 carbon steel and the stainless steel treated sensitively. The additives used were Zn [Zn(NO_3)_2, ZnSO_4 and ZnO], Al [Al(NO_3)_2 and Al_2(SO_4)_3], Zr [ZrO(NO_3)_2] and Si [Na_2SiO_3] compounds. The exposure tests were carried out in high temperature and high pressure water at 100 ppb to 1 ppm and at 1 muM of additive concentration and at < 5 to 8000 ppb of dissolved oxygen concentration with and without pre-filming treatment for 200 to 600 h. In particular, it was found that the amounts (or rate) of total corroded metals in the systems adding Zr (in stainless steel and carbon steel) and Si (in stainless steel) compounds tended to decrease in comparison with those in non-additive systems. The films of oxide compounds on steel surfaces after exposure tests were formed. And then, it was confirmed that from the depth profile data of glow discharge optical emission spectroscopy (GDS), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), etc. , the films had a double layer structure consisting of a Fe-rich outer layer and Cr-rich inner layer. From the systematic evaluation by various physicochemical measurements, it was thought that the effects of corrosion protections of steels were due to an increase of protective ability of film by Zr oxide in the system adding Zr compound and a depression of outer-diffusion of CrO_4^<2-> by adsorption of SiO_3^<2-> on steel surface in the system adding Si compound.