Measurement of 238U Doppler effect using various samples in FCA XVII-1

238U Doppler effect measurements were carried out using 6 uranium samples with various composition or diameter varying self-shielding factors of 238U. Calculation accuracy of the standard analysis method for fast reactor cores at FCA was investigated. The Doppler effect were measured by the sample-heated and reactivity worth measurement method up to 800degC in the FCA XVII-1 assembly, which simulated Na-cooled MOX fueled FBR. In the analysis, the Doppler effect was calculated using the effective cross sections obtained by the PEACO-X code. The calculated values based on the diffusion theory agreed well with the experiment for the U-metal and UO2 samples. The calculation underestimated the experiment from 10% to 30% for the UO2 samples containing BeO. This underestimation was improved by the use of the transport calculation. The calculation, however, underestimated about 20% for the sample whose background cross section is greater than 300 barns. (author)