Evaluation and demonstration of methods for improved fuel utilization. Second semi-annual progress report, April 1, 1980-September 30, 1980

Demonstrations are being performed in the Fort Calhoun reactor. The current program consists of two parts, one to demonstrate low leakage fuel management (SAVFUEL - Shimmed And Very Flexible Uranium Element Loading) and the other to demonstrate high burnup. The first part will demonstrate that the power duty cycle which is characteristic of SAVFUEL does not have a deleterious effect on fuel performance, while the second part will demonstrate that the peak rod average burnup of the current 14 x 14 fuel design can be increased to 45 GWD/T. A visual examination conducted at poolside was completed on four fuel assemblies which are scheduled to demonstrate the SAVFUEL power cycle and seventeen fuel assemblies which are scheduled to provide high burnup fuel performance data. Results of visual examinations, shoulder gap closure, fuel assembly growth, and fuel rod channel width measurements are reported which show excellent fuel performance for the high burnup; demonstration assemblies after four exposure cycles. These results support an additional exposure cycle for the high burnup demonstration assemblies which currently have an assembly average burnup up to 37 GWD/T