Measurement of doppler effect up to 2000degC at FCA

For the improvement of the Doppler effect calculation accuracy in high temperature range, new experimental devices were developed to measure Doppler effect up to 2000degC and measurements were carried out at Fast Critical Assembly of JAERI. For the measurements, two methods were used: the one is a sample reactivity measurement and the other is a foil activation measurement with laser heating. In the analyzing the experimental data, a new cell calculation code of ultra-fine groups, PEACO-X, was used to generate effective cross sections of the Doppler sample, which took into account the resonance overlapping effect between the 238U of the Doppler sample and the tungsten structural material of experimental devices. The calculation of the Doppler effect underestimated the measured Doppler reactivity worths for the sample reactivity method, while it showed a good agreement with the measured Doppler ratio for the foil activation method. (author)