Results of Qualification Program Performed to Prepare 37M Fuel for Use in Darlington Nuclear Power Stations

Abstract

An out-reactor qualification program was performed in the full scale CANDU® fuel channel facility located at Stern Laboratories to measure the response of Modified 37-element (37M) fuel and compare this to reference 37-element (37R) fuel under flow and acoustic pulsation excitation over the full range of reactor operating conditions. Tests were also performed to ensure the rates of fretting in the 37M fuel and pressure tube were within acceptable limits. The qualification program included a series of acoustic/vibration tests using 3 different fuel strings: 37M, 37R and a mixed string. Also performed were two endurance tests (Test 1 with the modified fuel design string and Test 2 with the reference fuel design string) and a crossflow test to confirm acceptable rates of fretting. The acoustic tests were performed with each fuel string subjected to dynamic pressure pulsations at 210 Hz over a full range of operating temperatures. The fuel strings were also subjected to dynamic pressure pulsations at variable frequency conditions at specific temperatures. The pressure drop was also measured and compared. The endurance tests were conducted at 265 deg C with a flow rate of 28 kg/s, pressure pulsations of 210 Hertz for an elapsed time of 168 hours. The acoustic test results indicated that the pressure patterns and vibration responses of the modified and reference fuel strings were not demonstrably different and no unacceptable bundle wear or deformation was observed in the post-test inspections. Similarly, the Endurance tests indicated no demonstrable differences in the rates of fuel bundle fretting, vibration levels or pressure tube fretting.