Micromechanical aspects of constraint effect in steel for containers of spent nuclear fuel

Based on two-parameter fracture mechanical approach to the analysis of brittle fracture initiation the three point bend specimens with different crack lengths were tested at various temperatures. Low carbon manganese cast steel was used for analysis being tested as one of candidate materials for radwaste containers, Although strong dependence of measured fracture toughness on crack tip constraint was observed no evident differences in fracture morphology have been identified except for quantitative ones. Modified approach to Q-parameter calculation has been applied being based on critical value of J-integral as loading parameter instead of fracture load. The cleavage fracture stress has been found to be increasing with loss of crack tip constraint. Toughness scaling model has been applied when transferring the fracture toughness data from small pre-cracked Charpy type specimens to standard ones.