No abstract

No abstract

No abstract

In 1988 and 1990, the reactor pressure vessels of Units 1 and 2, respectively, of the Greifswald nuclear power station were subjected to heat treatment at 475°C for annealing of irradiation effects. To demonstrate the effect of annealing and to evaluate a new postannealing transition temperature of vessel base metal and weld metal, boat samples were removed by means of electric discharge machining (EDM) from the (unclad) inner surface of the vessel. From these samples, micronotched bar impact test specimens were fabricated and tested at different temperatures. Transition curves were evaluated from the results. By means of correlation tests, the transition temperatures evaluated from the micro-specimen tests are converted to standard Charpy-V transition temperatures. Results are available for the weld metal of Unit 1 after annealing. The transition temperature TK is lower than the value calculated by the designer of the plant. Specimens removed from Unit 2 before and after annealing are in preparation.

Fracture toughness testing in the elastic-plastic temperature range of material behavior is described in the Master Curve standard ASTM 1921-97. The standard allows measurement of valid fracture toughness values up to KJC= 100 MPa√m with clearly smaller than standard CVN-size specimens for the irradiated material condition. However, a relatively small amount of data measured with miniature specimens of cross-sections 5 mm × 5 mm or 3 mm × 4 mm have been published and hence the utilization of such small specimens is generally not accepted even if the universal specimen size criteria are fulfilled. In this study, the fracture toughness transition temperature T0 has been measured for a high phosphorus content WWER 440 weld coded as W502 both in the non-irradiated and in the irradiated and annealed material conditions. Three-point bend specimens of cross-sections 10 mm × 10 mm, 5 mm × 5 mm and 3 mm × 4mm were used in the study.