Radiation hardening/embrittlement was investigated for clad-heat affected zone (clad-HAZ)) of reactor pressure vessel (RPV) of Hamaoka unit-1 boiling water reactor (BWR) under decommissioning process. The neutron irradiation fluence in the HAZ of the RPV steel was 1.5 × 10²² n/m² (E > 1MeV). The shift in ductile-brittle transition temperature, ΔDBTT, was measured to be +26 °C using 1/3-sized Charpy specimens, while the increase in Vickers hardness, ΔHv, was 19 HV in the clad-HAZ of 1.6 mm depth from the clad boundary. Atom probe tomography (APT) was conducted at the locations 0.1, 0.8, 1.6. 4 and 10 mm away from the clad boundary, and revealed that solute clusters were formed in both clad-HAZ and base metal (10 mm depth), and the clusters were rich in Mn, Ni, Si, Cu with the averaged diameter of about 2.5 nm and the number density of 2 × 10²²/m³, being almost independent of depth location. As for the chemical compositions of the clusters, Mn content increased with decreasing Cu content. This suggests that there might be site completion between Mn and Cu for clustering. Radiation hardening of clad-HAZ induced by the formation of solute clusters was estimated on the bases of the dispersed barrier hardening (DBH) model in terms of $\sqrt{N·d}$, and well interpreted with α = 0.06–0.08. The ΔDBTT-$\sqrt{V_f}$ plot, of which the data was measured with 1/3 size specimens sampled from the clad-HAZ at 1.6 mm depth, agreed with the previous surveillance test results measured in surveillance tests with standard size specimens of base metal.

研究了退役过程中滨冈 1 号沸水反应堆 (BWR) 反应堆压力容器 (RPV) 的包层热影响区 (clad-HAZ)) 的辐射硬化/脆化。RPV 钢 HAZ 中的中子辐照注量为 1.5 × 10 ²² n/m ² ( E > 1MeV)。使用 1/3 尺寸的夏比试样测得的韧脆转变温度的变化 Δ DBTT为 +26 °C，而维氏硬度的增加 Δ Hv，在距包层边界 1.6 毫米深度的包层热影响区中为 19 HV。在位置 0.1、0.8、1.6 处进行原子探针断层扫描 (APT)。距包层边界 4 和 10 毫米处，表明在包层热影响区和母材（10 毫米深度）均形成溶质簇，簇中富含 Mn、Ni、Si、Cu，平均直径约为2.5 nm 和数密度 2 × 10 ²² /m ³，几乎与深度位置无关。至于团簇的化学成分，Mn含量随着Cu含量的降低而增加。这表明 Mn 和 Cu 之间可能存在用于聚集的位点完成。由溶质簇的形成引起的复合热影响区的辐射硬化是根据分散的屏障硬化 (DBH) 模型估计的$\sqrt{N·d}$，并且很好地解释了 α = 0.06–0.08。Δ DBTT -$\sqrt{{伏}_F}$ 图，其中的数据是用 1/3 尺寸样本从包层热影响区在 1.6 毫米深度取样测量的，与之前的监督测试结果一致。