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A description is given of an out-of-pile experiment which simulated fission-gas release in current-design uranium-oxide fuel subassemblies of liquid- metal-cooled fast breeder reactors (LMFBR's) and which was performed to evaluate the potential for pin-to-pin failure propagation due to thermal transients induced in adjacent fuel pins. A sodium-cooled test section containing three electrically heated pins was used. Gas (angon or xenon), injected as a jet through a needle protruding into the flow cross-sectional area of the test section, was made to impinge on one of the heater pins. Data are presented regarding the measured cladding-temperature rise and the calculated local heat- transfer coefficient in the impingement area, with the following parameters: gas type, needle internal diameter, heat flux, coolant flow rate, gas-plenum pressure and temperature, and axial location with respect to the gas jet. The cladding- temperature rises measured represent upper values, since the conditions under which they were obtained are conservative. There are two reasons for this: (a) The gasrelease rates correspond to those that would prevail if the internal resistance to the flow of gas, between the gas plenum and the point of release of the fuel pin, were negligibly small; (b) the tests were performed under steady- statemore » conditions, whereas, under actual reactor conditions, the gas-release rates would be decreasing with time because of the fixed fission-gas inventory. For a narrow range of gas-release rates under subsonic and near-subsonic conditions, cladding-temperature rises were found to occur in the impingement area, for the above conservative conditions, of up to approximates 240 deg C at a heat flux of 250 W/cm/sup 2/. (auth)« less |
