Embrittlement evaluating fracture toughness

While neutron irradiation results in some reduction in fracture toughness at the center of the top guide and the midplane of the core shroud, fracture toughness remains high. Further consideration of irradiation embrittlement of RPVIs is not required. However, for cracked components, a fracture mechanics evaluation of material that has been exposed to high neutron fluence should be performed to assure crack stability on a component specific basis. 

The widespread use of Izod and Charpy impact tests to evaluate plastics is, to an unprejudiced eye, rather difficult to justify. Many structural polymers us in load-bearing applications do show a range of fracture behaviour from ductile to brittle . Most thermoplastics can show either kind of behaviour, and may suffer an abrupt tough-to-brittle transition with any of a number of parameters — one of which is the rate of loading at a notch. In order to select a polymer for a specific application it may be important to know its sensitivity to this kind of impact embrittlement. However, it is difficult to see how one might learn this fiem conventional impact strength data. 

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