Calculation accuracy analysis of core design code for ATR (Advanced thermal reactor) demonstration plant

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The calculation accuracy of the WIMS-ATR/LAIMON-2A codes, or a core design code for the ATR Demonstration Plant was evaluated on the basis of the experimental data from the first to the eighth cycle of the FUGEN. The major results obtained in this study are shown below; (1)The calculation accuracy evaluation based on the data of the type-A fuel cores (from the first to the third cycle). (a)The calculation errors of power distribution are about 3.0% 3.9% in terms of the RMS (Root Mean Square) of the relative errors for the segment power, and 1.1% 1.9% in terms of the RMS of the relative errors for the channel power. Therefore, the calculation values are in good agreement with experimental values. (b)The relative calculation errors of the channel power peaking factors are as small as -0.9% 0.1%, Whereas the relative calculation errors of the hottest segment powers are large as -4.0% -0.7%. This is caused by the disagreement between measured and calculated axial power distributions. (c)The critieal eigen values of the LAYMON-2A code are 0.982 0.992, which are underestimated about 1.8%k compared with the experimental value Keff=1.0. (d)The relative calculation errors of neutron flux distribution based on the PCM readings are 3.6% 5.2%. Therefore, the calculation values are relatively in good agreement with experimental values. (e)The calculation accuracy based on WIMS-ATR for power distributions, especially channel power distributions, channel power peaking factors and neutron flux distributions, has been improved in comparison with METHUSELAH-II. However, the calculation errors of the hottest segment powers have been increased. The reason is that the agreement of calculated and measured axial power distributions by WIMS-ATR is deteriorated in comparison with METHUSELAH-II. (2)The calculation accuracy evaluation based on the data of the type-B fuel cores (from the fourth to the eighth cycle). (a)The ...