This paper presents a thorough APT study of VVER-440 RPVs WM and BM samples cut out from the inner RPV surface. The features of phase formation (number densities, sizes and composition) in VVER-440 RPV steels under primary irradiation, recovery annealing, re-irradiation, recovery re-annealing and subsequent accelerated re-irradiation are identified to justify its lifetime extension up to 60 years by recovery re-annealing.

It is shown that primary and re-irradiation is accompanied by formation of radiation-induced Cu-P-based precipitates whereas recovery annealing leads to their partial dissolution and coarsening of the undissolved ones. At this, for both WM and BM under primary annealing, Cu dissolves in the matrix, while under re-annealing Cu almost doesn't return to the matrix. In WM P fully dissolves in the matrix under annealing while in BM there is gradual matrix P depletion under operation (including recovery annealing) due to formation of P grain boundary segregation. Under the third irradiation cycle, Cu almost doesn't contribute to precipitation: in WM radiation-induced precipitates are P-based, enriched with Si, Ni and Mn, while in BM there are Si-based precipitates, enriched with Ni and Mn. In BM number density of precipitates is lower than in WM during all operation stages that causes its lower radiation embrittlement.

本文对从内部RPV表面切出的VVER-440 RPV WM和BM样品进行了详尽的APT研究。确定了VVER-440 RPV钢在一次辐照，恢复退火，再辐照，恢复再退火和随后的加速再辐照下的相形成特征（数量密度，尺寸和组成），以证明其寿命可延长至60年通过恢复重新退火。

结果表明，初次辐射和再辐射伴随着辐射诱导的基于Cu-P的沉淀物的形成，而恢复退火导致它们的部分溶解和未溶解物的粗化。在这种情况下，对于WM和BM，在一次退火下，Cu都溶解在基体中，而在再退火下，Cu几乎不会返回基体中。在WM中，退火过程中P完全溶解在基体中，而在BM中，由于P晶界偏析的形成，在运行中（包括恢复退火）P逐渐耗尽。在第三个辐照周期下，Cu几乎不参与沉淀：在WM辐射诱导的沉淀物中，P为主，富含Si，Ni和Mn，而在BM中，Si为主的沉淀物中富含Ni和Mn。