EVALUATION OF CRITICAL BUCKLINGS OF LIGHT-WATER MODERATED LOW ENRICHED UO2 CORES BY THE VARIABLE LOADING METHOD

Horizontal extrapolated distances lambda(h) and critical bucklings B(c )2 for light-water moderated low enriched UO2 cores were evaluated usi ng the variable loading method. A set of critical height (water levels ) of the cores having various horizontal dimensions was used in this m ethod. Errors of the present method were smaller than the previous one s by the flux shape method in which the horizontal extrapolated distan ce was determined from the horizontal power distribution. The presentl y obtained lambda(h), and B(c)2 reproduced well the change in the crit ical water level for the whole range of the horizontal core size, whil e the previous ones could be used only for a limited range. Moreover, the effective multiplication factors obtained through the cell calcula tion of the SRAC code by using the presently evaluated critical buckli ngs agreed much better with the rigorous ones by the continuous energy Monte Carlo calculation using a full core model, than those by using the previous values. Therefore, it was concluded that the variable loa ding method can give more accurate values for lambda(h) and B(c)2 than the flux shape method for the cores investigated.