A final report on the first test assembly (77LF-33J) for fuel center temperature measurement experiment

An experiment of fuel center temperature measurement, which is one of the most fundamental experiment for LWR fuel safety, is progressing in the water loop (OWL-1). Three test fuel assemblies were designed and fabricated for the experiments, and the irradiation and post-irradiation examinations (PIE) on the first test assembly were completed. Temperatures of the rods were re-calculated by using FREG-4 and FEMAXI-3 codes due to the plenum gas analysis data. Comparisons between calculated and measured values of the center temperature are in good agreement with a tolerable measurement error. The initial relocation of the tested rods was estimated to be 50% of initial gap from the PIE and comparison results. Some problems on the design and fabrication of instrumentations such as tungsten-rhenium thermocouple, eddy-current type displacement and pressure sensors, and turbine flowmeter are also discussed. (author)