Thermal stratification and reactor piping integrity

LES benchmark study of high cycle temperature fluctuations caused by thermal striping in a mixing tee

“…Outside the core region, components where hot and cold streams come in contact, such as tee junctions, elbows, and leakage from valves, may also be affected. The focus of thermal striping studies shifted to light water reactors (LWRs) after several incidents of piping failure at some nuclear power plants (Kim et al, 1993;Claude, 2003;Fukuda et al, 2003). The piping systems that are most susceptible to thermal striping fatigue cracking are mixing tees of the residual heat removal (RHR) systems in both BWR and PWR.…”

Numerical simulation of temperature fluctuation reduction by a vortex breaker in an elbow pipe with thermal stratification

“…In a nuclear piping system, thermal stratification is produced by mixing or natural convection of cold and hot fluids; thermal stratification can appear in the hot leg, cold leg, valve, elbow pipe and T-pipe and induce thermal fatigue of the pipe, which can affect the normal operation of a nuclear power plant (Kim et al, 1993). Therefore, finding ways to reduce the thermal fluctuations and minimize thermal fatigue has become an important security issue in the nuclear power field.…”

Thermal fatigue estimation due to thermal stratification in the RCS branch line using one-way FSI scheme

“…[19] Most notably, it has been shown that a swirling, vortical flow structure, as opposed to turbulence penetration, can be established in a dead-ended branch line due to the flow in the RCS line. [14,17] In this study, thermal fatigue estimation due to thermal stratification in the RCS branch line of KSNPP (Korea Standard Nuclear Power Plant) is performed using one-way FSI (fluid and structure interaction) scheme. Detailed thermal loading due to thermal stratification and cycling is evaluated based on temperature distributions with time, which is calculated by the CFD analysis.…”

“…The thermal stratification, cycling, and stripping (TASCS) program identified several critical parameters and offered predictive tools to assist in assessing fatigue loadings for thermal-structural analysis. [6] Other studies pursued experimental investigation into the thermal cycling phenomena based on scaled experiments [14][15][16][17][18] or full-scale plant operation. [19] Most notably, it has been shown that a swirling, vortical flow structure, as opposed to turbulence penetration, can be established in a dead-ended branch line due to the flow in the RCS line.…”