Prediction of the effects of thermal ageing on the embrittlement of reactor pressure vessel steels

On the Modelling of Thermal Aging through Neutron Irradiation and Annealing

“…Such segregations hardly affect material hardening [10]. e proposed method [7] consists in determining material embrittlement after the following two-stage treatment. At the first stage, accelerated neutron irradiation for short time with high neutron flux is conducted at T � T oper , which hardly changes the value of equilibrium P segregation and, at the same time, accelerates the formation of P segregations due to radiation-enhanced diffusion.…”

“…At the second stage, the irradiated material is annealed at a temperature which deletes material hardening caused by neutron irradiation and leads to P dissociation from the intragranular interphase boundaries, but, at the same time, does not lead to P dissociation from GBs. For the WWER-1000 RPV materials, this annealing temperature T anneal � 450°S [7]. In addition, for the effective P diffusion coefficient to be determined, thermal aging should be carried out at the temper brittleness temperature [7].…”

“…For the WWER-1000 RPV materials, this annealing temperature T anneal � 450°S [7]. In addition, for the effective P diffusion coefficient to be determined, thermal aging should be carried out at the temper brittleness temperature [7].…”

“…According to the [7] time dependence of transition temperature shift due to P thermal aging, ΔT k (t) is determined on the basis of the following considerations. e dependence ΔT k (t) has been deducted when using the McLean equation [6], the theory of radiation-induced diffusion [11][12][13][14][15][16][17][18][19][20][21][22], and the introduced relation between the transition temperature T k and P concentration on the interphase boundaries and/or GBs at the current moment of time (C t p ) [7].…”

“…e dependence ΔT k (t) has been deducted when using the McLean equation [6], the theory of radiation-induced diffusion [11][12][13][14][15][16][17][18][19][20][21][22], and the introduced relation between the transition temperature T k and P concentration on the interphase boundaries and/or GBs at the current moment of time (C t p ) [7]. e transition temperature is taken as the temperature at which the Charpy impact strength equals 47 J or fracture toughness for specimens with thickness of 25 mm equals 100 MPam 1/2 for the fracture probability of 50%.…”