Experimental assessment of the effectiveness of recovery annealing of VVER-1000 vessels

An experimental assessment of the effectiveness of recovery annealing of VVER-1000 vessels on the basis of mechanical tests and structural studies of control samples of the main metal and the weld-seam metal with high nickel content (>1.65%) in the No. 1 unit of the Balakovo nuclear power plant in states after primary irradiation in the control sample channels, annealing in a chosen regime, and repeat accelerated irradiation in the IR-8 research reactor to fluence corresponding to extended service to 60 yr and longer is presented. The mechanical tests and structural studies showed a high degree of recovery of the structure and properties for the chosen temperature–time regime of annealing as well as a lower rate of repeated after the recovery annealing embrittlement as compared with the rate of embrittlement with primary irradiation.