EARLY HEARING DETECTION AND INTERVENTION VIRTUAL CONFERENCE
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5/17/2017 | 3:55 PM - 4:20 PM | The Thermal Properties Of Fresh And Spent U-Mo Fuels: An Overview | 1

The Thermal Properties Of Fresh And Spent U-Mo Fuels: An Overview

Currently, research reactors that are operated with high enriched uranium fuel, are in the process to convert to lower enriched uranium fuels. Therefore, a new kind of fuel, based on high density uranium-molybdenum (U-Mo) alloys, has been developed. For the fuel qualification it is mandatory to know the heat fluxes and the overall temperature in the fuel element during reactor operation. Thus, the thermal conductivity becomes a key quantity to simulate the safe cooling of a reactor core built up by high density fuel. The thermal conductivity of fresh and irradiated U-Mo dispersion and monolithic fuel has been measured. The thermal conductivity of fresh dispersion fuel at a temperature of 200°C decreases from 61W/mK down to 19W/mK at a burn-up of 4.9·1021f/cc and down to 10W/mK at a burn-up of 6.1·1021f/cc. Fresh monolithic fuel has a low thermal conductivity of 17W/mK. Consequently, its decrease during irradiation is less steep than for the dispersion fuel. It decreases at a temperature of 200°C from 17W/mK before irradiation to 13W/mK at a burn-up of 3.5·1021f/cc. The difference of the decrease of both fuels originates from effects in the matrix that occur during irradiation, like the growth of an interaction layer (IDL) between U-Mo fuel particle and Al matrix and matrix hardening. The growth of fission gas bubbles and the decomposition of the U-Mo crystal lattice affect both dispersion and monolithic fuel. The measured data were successfully reproduced with the model of Hsu which was combined with empirical models, describing the effects from irradiation.

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Presenters/Authors

Tanja Huber (), Technische Universität München / FRM II, tanja.huber@frm2.tum.de;