The Prometey local approach of cleavage fracture has been applied within the TACIS R2.06/96 project: “Surveillance Program for VVER 1000 Reactors”, sponsored by the European Commission. The main tasks are: • perform special experiments on smooth cylindrical and pre-cracked Charpy (PCC) specimens for VVER 1000 RPV material in initial, embrittled and irradiated state; • perform fracture toughness tests on 2T-CT specimens for RPV steel in initial and embrittled state; • predict the KJC(T) curves by this model; • compare the calculated and experimental results with the Master Curve results. The local approach of cleavage fracture is applied to predict KJC(T) curves in the transition regime of RPV materials in the initial state, embrittled by thermal heat treatment and irradiated, samples in the latter cases taken from surveillance capsules of a VVER 1000 NPP. The test data of large fracture mechanics specimens (2T-CT) could be well described over a wide temperature range for the initial state and the embrittled material, when the test results of PCC specimens at one temperature are used for the calibration of the model parameters. It is recommended for future application cases to use PCC specimens for the calibration of the parameters. A comparison of the Prometey local approach with the Master Curve approach lead to a good agreement for all investigated materials apart from the thermally embrittled material which has a very high embrittlement level (DBTT shift). The KJC(T) curves of VVER1000 RPV steels with low and moderate embrittlement level could be well predicted by both methods. Because the Master Curve method is already accepted as an international standard, it might be easier to apply in more routine cases. The Prometey probabilistic model may be also used for the prediction of KJC(T) curves of RPV steels with a high embrittlement level.
Dissimilar metal welds (DMW) are used in nuclear power plants between the nozzles of main components in low alloy steel and stainless steel pipes, or safe-ends connected to the main coolant line pipes. AREVA proposes for EPR™ an improved design of DMW involving narrow gap welding without buttering between the low alloy steel nozzles and the stainless steel safe-ends, and the use of a corrosion resistant weld filler metal (Alloy 52).
AREVA performed a thorough characterization of this type of welds, which shows a particular microstructure close to the fusion line between the low alloy steel and the nickel base alloy, where the heat affected zone of the low alloy steel is decarburized.
This paper presents results of fracture toughness tests performed with the crack tip located in this area, in the ductile to brittle transition in the as post-welded heat treated condition and after thermal ageing. The results show an excellent fracture toughness behavior of this particular area, compared to that of low alloy steel parent metal.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.