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The effect of temperature on the nature of oxide formed from uranium oxidizing in air is pronounced, there being an increase in particle size wtth increasing temperatare over the range 400 to 800 deg C. At 1000 deg C and above the oxide formed remains largely intact, giving rise to few-micron size particles during the heating period. In relating these facts to fission product release, it would be anticipated that the effect of air velocity on the release of fission products would be more pronounced at lower temperatures. Only a fraction of those oxide particles of apparert entrainable size become airborne, emphasizing the possible effects of fuel elemert geometry and orientation. This stability of a mass of fine particles is an importart factor to consider in a system where localized high air velocities or explosions might occur. This material once dispersed by a sudden rise in air stream velocity could remain suspended for extended periods of time. Deposition of uranium oxide and fission products on experimental apparatus points out the importance of the location of the fuel element during an overheating incident. In conclusion, particulate entrainment and deposition, fuel element geometry, oriensations and location are variables which may have anmore » important effect on fission product release. These variables along with effects of temperature, fuel elemert composition, cladding, air velocities, and irradiation level compose a very complex system. Since little research to date has dealt with deposition parameters, this area merits added consideration. (auth)« less |
