AN ADDENDUM: PROBABILISTIC FAILURE ANALYSIS OF A RESIDUAL HEAT REMOVAL HEAT EXCHANGER DURING POSTULATED LOSS OF COOLANT ACCIDENT

摘要

The previous work analyzed Residual Heat Removal System (RHRS) heat exchanger pressure tube failure probabilities, which were calculated using a Monte Carlo simulation. In the analysis, Probabilistic Fracture Mechanics (PFM) was used along with a Monte Carlo Simulation (MCS) to estimate the failure probability of the pressurized tubes within the heat exchanger. The Monte Carlo simulation was first conducted in MATLAB. It has been rewritten in FORTRAN, now calculating the flow rate for each failed tube out of one million trials and outputs the flow rates with their respective initial flaw dimensions. But more importantly, this program calculates the probability of a single tube failure in the RHR heat exchanger. The results from FORTRAN are consistent with those of the earlier analysis in MATLAB, validating the previous findings. While the earlier study found that tube failure was expected to be improbable for straight tubes, questions remained regarding the model's applicability to curved sections of tubing. This additional analysis addressed those questions. The analysis focused on comparing the stress and displacement developed between the curved section of flawed a U-tube and a flawed straight tube using SolidWorks.The results from this analysis are beneficial for further understanding of the stress distribution in RHR heat exchanger tubing.