Development of Low-Alloy Steel for High Level Radioactive Waste Disposal Container

为了研制高放废物地质处置用低合金钢容器，制备了一系列含0.12%C、能有效抑制Fe_3O_4阴极反应的合金元素的钢，并对其耐腐蚀性能进行了研究. Fe_3O_4和MO_x复合氧化膜（M：用离子束溅射沉积法制备了Cr、Mo、Si、Al、Ti、Cu、Ni、Nb等10种金属离子，研究了它们在膨润土与模拟水接触溶液中的阴极极化特性（5. 72 mM-Na_2SO_4+7. 99 mM-NaHCO）_3实验结果表明，在Fe_3O_4中加入Cr_2O_3、TiO_2、Al_2O_3和MoO_2，能有效地抑制Fe_3O_4的还原溶解。用真空感应熔炼法制备了一系列含有Cr、Mo、Si、Al、Ti、Cu、Ni、Nb等抑制Fe_3O_4还原溶解和提高氢过电压的合金元素的低合金钢。在含0. 5 M-NaCl的膨润土接触水模拟溶液中，对膨润土进行了腐蚀试验。含0.5%Cu、Al、Cr或Ti的钢在无Fe_3O_4膜时具有良好的耐蚀性，而含Cu、Nb或Ti的钢在有Fe_3O_4膜时具有较高的耐蚀性。这表明Cu是最有希望提高耐蚀性的合金元素.在模拟蒙脱石接触水溶液中，测定了所研制的低合金钢的阳极极化曲线和阴极极化曲线。在腐蚀试验中，具有优异耐蚀性的钢表现出高的氢过电压和低的Fe_3O_4还原溶解速率。

In order to develop a low-alloy steel container for use in geological disposal of high-level radioactive wastes, a series of 0.12%C steels containing a small amount of alloying elements, which are effective in inhibiting cathodic reactions on Fe_3O_4, were prepared and their corrosion resistance was examined.1. A series of composite oxide films consisting of Fe_3O_4 and MO_x(M: Cr, Mo, Si, Al, Ti, Cu, Ni, Nb) were prepared by ion-beam-sputter deposition and their cathodic polarization characteristics were examined in a simulated solution of water in contact with bentonite (5.72mM-Na_2SO_4+7.99mM-NaHCO)_3 The results showed that the addition of Cr_2O_3, TiO_2, Al_2O_3 and MoO_2 to Fe_3O_4 is effective in suppressing reductive dissolution of Fe_3O_4.2. A series of low-alloy steels containing alloying elements (Cr, Mo, Si, Al, Ti, Cu, Ni, Nb), which are effective in inhibiting reductive dissolution of Fe_3O_4 and in increasing hydrogen overvoltage, were prepared by vacuum induction melting. The corrosion tests were performed in compressed bentonite exposed to the simulated solution of bentonite-contacting water containing 0.5M-NaCl. In the absence of Fe_3O_4film the steels containing 0.5% Cu, Al, Cr or Ti showed good corrosion resistance, while in the presence of Fe_3O_4film those containing Cu, Nb, or Ti exhibited high corrosion resistance. This suggests that Cu is the most promising alloying element for improving corrosion resistance.3. Anodic and cathodic polarization curves of the low-alloy steels developed in the present study were measured in the simulated solution of bentonite-contacting water. The steels having excellent corrosion resistance in the corrosion tests showed a high hydrogen overvoltage and a low reductive dissolution rate of Fe_3O_4.