Procedures for Interpreting the Structural Implications of Radiation-Damage Surveillance Results on Nuclear Pressure Vessels

摘要

The structural implications of radiation effects to nuclear reactor pressure vessels are assessed primarily through surveillance programs in which the properties of the vessel are projected from an evaluation of small specimens of the vessel steel. In the USA, the current fracture-safe criterion requires that the vessel operating temperature, at certain stress levels, be at the FTE (Fracture Transition Elastic) temperature, defined as NDT+60F(33C), derived from surveillance measurements. Review of available data from five reactor surveillance programs indicates that this criterion is adequate for the vessels concerned. Complete assurance of fracture-safe operating conditions can be attained through a limit-analysis procedure that considers and integrates the effects of five factors: (a) the radiation-induced shift in transition temperature, (b) the initial shelf energy, (c) the radiation-reduced ductile shelf energy, (d) the effects of the fluence (and toughness) gradient through a thick vessel wall, and (3) the effects of thickness-induced mechanical constraint. (Author)