Session: OAC-01-01 Safety, Reliability, and Risk Management

Paper Number: 123405

123405 - Development and Validation of an Effective Screening Process for Thermal-Hydraulic Phenomena With Relevance to Thermal Loads in Nuclear Power Plants Piping Systems 

In nuclear power plants, there is a series of pipe junctions with a main pipe connected to closed-end branch pipe, in which degradation due to thermal fatigue potentially can occur. Thermal fatigue cracking due to thermal stresses in a branch pipe occurs at the fluctuating boundary created by the turbulent penetration of hot fluid from the main flow into the cold stagnant fluid of the branch line. This is a thermal hydraulic phenomenon also known as “Farley-Tihange”. The most common swirl penetration scenario in nuclear power plants (NPPs) is found in branch lines sealed at one end by a check valve.

Due to numerous potential locations it is highly necessary to develop and apply an effective state-of-the-art screening process. The process consists of two steps: a fast-running thermal hydraulic tool as pre-screening step and a detailed analysis of the 3D flow by means of Computational Fluid Dynamics (CFD) as final step. The pre-screening tool sorts the junctions into those as potential risk locations where thermal fatigue is a possibility and those where thermal fatigue can be conservatively ruled out. The result of the pre-screening process step is a prioritized list of branches where the application of a detailed CFD simulation is required for expert decisions such as design changes.

The developed screening process is validated against available experimental data from the open literature. Its effectiveness and accuracy for the identification of locations in NPP piping systems where the risk of thermal stresses exists and for the prediction of parameters of interest, such as turbulent penetration depth in pipe, is demonstrated.

Presenting Author: Luciana Rudolph Framatome GmbH

Presenting Author Biography: Dr. Luciana Rudolph works at Framatome in the field of Safety Analyses and Fluid Dynamics for more than 12 years. Today she is a Framatome Expert in Numerical Fluid Dynamics supporting many projects worldwide in the area of analysis and optimization of component performance, safety processes, fluid loads on piping systems. She also leads R&D projects developing calculation methodologies, for instance, for prediction of deposition of corrosion products in steam generators.

Authors:

Luciana Rudolph Framatome GmbH
Richard Trewin Framatome GmbH
Robert Buettner Framatome GmbH
Thomas Fuchs Framatome GmbH