On thermal annealing of irradiated PWR pressure vessels

Small-angle neutron scattering study of neutron-irradiated and post-irradiation annealed VVER-1000 reactor pressure vessel weld material

“…Such kind of studies may advantageously be accompanied by computer simulations (Chiapetto et al, 2015;Ke et al, 2017;Konstantinović et al, 2019). Second, large-scale annealing treatments of the RPV belt line region (Pelli and Törrönen, 1998;Brumovsky, 2015;Server and Nanstad, 2015) of operating nuclear power plants have been carried out to date or are envisaged in order to mitigate embrittlement and extend the duration of safe reactor operation. This kind of benefit is based on a partial or complete recovery of both the as-irradiated nanostructure and the mechanical properties of the RPV material.…”

“…This kind of benefit is based on a partial or complete recovery of both the as-irradiated nanostructure and the mechanical properties of the RPV material. In this context, studies of the annealing behavior formed the basis to identify optimum post-irradiation annealing regimes in terms of temperature and time (Popp et al, 1989) (e.g., 475 °C/152 h for VVER-440 reactors) or to demonstrate the success of realized high-temperature dry annealings (Pelli and Törrönen, 1998;Viehrig et al, 2009). Alternatively, less demanding and more cost-efficient procedures such as low-temperature (e.g., 343 °C) wet annealing within the RPV design limits (Pelli and Törrönen, 1998;Krasikov, 2012) might give rise to partial recovery possibly allowing for some limited but worthwhile lifetime extension.…”

SCK·CEN contribution to the IAEA Round Robin exercise on WWER-440 RPV weld material: irradiation, annealing and re-embrittlement

“…This annealing treatment was proven in the past to be the most effective in terms of Charpy-V transition temperature recovery for WWER-440 pressure vessel steels: the lower boundary ( -2 a ) of the recovery percentage is about 80% [6,7].…”