A probability of rupture for WWER-1000 main piping was calculated based on the Failure Assessment Diagram (FAD), treating material properties and crack morphology parameters as stochastic values. In order to perform probabilistic calculations, Critical temperature of brittleness and Yield (Ultimate) Stress were fitted by normal distribution, based on experimental data taken from the manufacture documentation found at the Ukrainian NPP. A set of calculations were conducted for Normal Operating(NO) conditions, Safety Shutdown Earthquake (SSE) and several emergency situations like: shaft jamming of a reactor cooling pump and break of the piping’s connected to the considered ones (a set of LOCA events). Based on static and dynamic calculations, the most loaded places were selected, where the cracks were postulated. Crack opening area was calculated according to originally developed procedure, which accounts for membrane and linear stress components thought the wall thickness. The Henry-Fauske flow model is used with modified parameters accounting for crack morphology as a normally distributed random variables. It is an important part of analysis, since different crack types have great differences in friction, bend protrusion and flow length parameters. The rupture probabilities for Main Circulating Piping were calculated with accounting for aging effects. It was proven, that crack morphology parameters highly affect the leak rate and its distribution becomes more scattered. Among the mechanical characteristic, a Fracture toughness has more influence rather than Ultimate of Yield strength.


Probability of Rupture for WWER-1000 Main Piping

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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