Effect of Flow Rate on Fission-Product Deposition from High-Temperature Gas Streams

Abstract

Abstract The deposition behavior of solid fission products has been studied. Experiments were made in an in-pile helium loop for gas flow with Reynolds number ranging from 1,300 to 13,000 at a gas temperature of about 500°C. The distributions of the fission products deposited along stainless steel tubes which had been exposed to the flow were obtained from γ-ray spectra measured with a Ge(Li) detector. The nuclides of the deposited fission products can be classified into three groups according to the distribution patterns: (a) 96Zr-Nb, 97Zr, 99Mo, 103103Ru, 132Te, (b) 91Sr, 140Ba-La, 141Ce and (c) 131 and 133I. Cesium-137 shows features of both groups (b) and (c). The deposition coefficients were obtained for the nuclides of group (a), which gave exponentially decreasing distributions. The effect of the flow rate (Reynolds number) on the deposition coefficients is discussed. For a stream with Reynolds number below 13,000, the deposition rate of metallic fission products is largely determined by the mass t...