UNDERSTANDING THE MECHANISMS OF FISSION GAS RELEASE - THE ROLE OF LOCAL MEASUREMENTS
Results from several electron microprobe investigations of transient tested water reactor fuel are reviewed. It was found that above 300 Wcm**-1 gas release increased with the power at the transient terminal level (TTL). Increasing the hold time from 24 to 72 h did not significantly increase gas release. Though, at high TTLs (about 400 Wcm**-1) it caused densification and redistribution of the porosity in the central region of the fuel. In addition to radial variations, axial variations in the concentration of xenon were observed. It was established that in dished pellets gas release can be appreciably lower at the pellet ends. Xenon concentration gradients were also measured in single UO-2 grains. At intermediate radial positions the xenon profiles conformed to a parabola. The effective diffusion coefficients derived from the retention data varied from 10**-15 to 10**-12 cm**2s**-1. X-ray fluorescence analysis was used to investigate gas retention at grain boundaries. First results indicate that not all the gas pores are vented at intermediate radial positions. Evidence for the accumulation of gas at boundaries in the outer regions of the release zone was not found.
Bibliographic Reference: HALDEN PROJECT WORKSHOP MEETING ON FISSION PRODUCT RELEASE, HALDEN (NORWAY) SEPT. 19-20, 1985 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 32429 ORA
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Record Number: 1989124052200 / Last updated on: 1987-01-01
Available languages: en