Irradiation WWER-440 steels

In a manner similar to the effects of irradiation on the CVN impact toughness, the fracture toughness is reduced by irradiation and exhibits a transition temperature shift as well as a reduction in/i and tearing modulus. Examples of these effects are shown in Figs 10.9a (Nanstad et al, 1992) and 10.9b Hiser et al, 1984) for two western RPV steels, while the effects on WWER steels are similar. As with CVN impact toughness, the effects of irradiation on the fracture toughness of RPV steels are dependent on the radiation sensitivity of the material which is primarily determined by the specific chemical composition. 

Amayev A D, Kryukov A M and Sokolov M A (1993), Recovery of the transition temperature of irradiated WWER 440 vessel metal by annealing, pp. 369-379 in Radiation Embrittlement of Nuclear Reactor Pressure Vessel Steels An International Review (Fourth Volume), ASTM STP1170, L E Steele, ed., American Society for Testing and Materials, Philadelphia, PA. 

Original trend curves given in the Russian Code have been updated in the last several years, and the current situation can be found either in the last IAEA VERLIFE procedure or in the leading Russian document. The values of Ap, n and a for specified temperatures of irradiation of materials for WWER-440 RPVs from 15Kh2MFA-type steel are given in Table 5.1. The upper boundary for 15Kh2MFA(A) materials and their welding joints... 

Embrittlement of RPVs in WWER-type reactors 111 Table 5.1 Values of irradiation embrittlement of steel 15Kh2MFA... 

Plots of fracture toughness, /(j, results for irradiated (a) western RPV steels (Sokolov and Nanstad, 1999) and (b) WWER-440 steels (Brumovsky, 2001). The data are normalized to To. 

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