Issue 36

T. Fekete, Frattura ed Integrità Strutturale, 36 (2016) 99-111; DOI: 10.3221/IGF-ESIS.36.10 100 the model, the structure and the key aspects of a more proper description of the PTS Calculation methodology were presented, as follows:  Objective of the study;  Codes and guides used during the project definition;  Geometry definition: o Parts of the RPV modeled during the study and the geometric model, • locations selected for Fracture mechanics analyses; o Flaw-size and geometrical distribution at selected locations; • relation of postulated flaws vs. detected flaws;  Description of neutron-transport calculations;  Materials: o Description of materials; o Description of constitutive models: • thermo-mechanics model and its parameters description of ageing; • fracture model and its parameters; description of ageing; o Qualification of material test methods;  Thermal-hydraulics: o Selection of overcooling sequences; o Thermal-hydraulic assessments;  Modeling of physical fields: o Kinematical model; o Physical fields; o Fracture mechanics model;  Integrity criteria. Applying the results mentioned above, these points will be discussed in the course of this review concerning the evolution of PTS Calculation Methodologies in Hungary. Considering the changing context, the objectives of the study, as well as the codes and guides used during the problem definition and solution will also be presented. P HASE 0.: D ESIGNER ’ S AND M ANUFACTURERS PTS S TRUCTURAL I NTEGRITY C ALCULATIONS Designer’s and Manufacturers PTS Structural Integrity Calculations he VVER-440 V213-type RPV design was developed by OKB Gidropress without PTS assessments in the first half of the 1970s; as at that time the PTS safety evaluations of the RPVs were not part of the design requirement. Normal operating events and anticipated emergency events were addressed in the loading specifications. Calculations of protection against brittle fracture were part of the original strength calculations, and followed the rules set by the Russian standard valid at the time. According to the rule, brittle fracture resistance was analyzed on the basis of the material’s static strength properties, but did not use fracture mechanics criterion. The Integrity of the RPV met the brittle fracture requirements if:  T wall ≥ T k , where T wall is the component’s wall temperature, T k is the critical temperature of brittleness of the component’s material, or  when T wall < T k and σ red < R p0,2 T /n, where σ red denotes Mohr’s reduced stress, R p0,2 T is yield stress of the material at the component’s wall temperature, n is the safety factor; n =2 if the component is regularly examined by non-destructive tests (NDT), otherwise n =4 [14]. Later, starting in the mid-80s, several PTS calculations were performed by OKB Gidropress and by other institutes, but in most cases, these studies assumed a generic RPV; so plant-specific conditions were neglected. The Manufacturer’s PTS Structural Integrity Calculations As part of the manufacturer’s strength-calculation documentations, Škoda provided a PTS analysis for a few accidental situations chosen based on engineering judgments, using linear elastic fracture mechanics. T