Detection of failed fuel in a reactor core by using burnup and power peaking factor monitors

One of the most important issues in a reactor core, at the time of radioactive material leakage, is detection and management of failed fuel assembly among all of assemblies. The purpose of this study is to provide a quick and efficient method compared to the non-destructive techniques, and common sipping tests to identify a failed fuel. The current method is based on sampling a coolant passing through the damaged FAs and evaluating the gamma spectrum obtained to measure the activity ratio of desired leaked fission fragments. Using the 134Cs/137Cs activity ratio and considering the history factor of each FA the maximum power peaking factor can be found. Also, by measuring the 133I × 135I /133Xe activity ratio the position of the core where failed-fuel is located can be predicted. In order to investigate the current method, a sample of the cooling water which passes through the failed fuel, located in the test sipping of the Tehran Research Reactor, was studied to measure the activity ratio of the desired isotopes. Then, the gamma spectrum at different cooling times (after leakage time) was studied. Considering the activity ratio of 134Cs/137Cs (0.1212) and the history of the relevant fuel (2.1023), the burnup of damaged-fuel was anticipated to be 33.92%. In addition the code calculations were carried out and we found that the suggested fuel assembly burnup is equal to 33.12%. Comparing the experimental as well as the calculational procedures gives a fairly good consistency of the herein method.