Destructive analyses for five spent fuel samples taken from a Gd bearing fuel assembly were done. The measured amounts of actinides of zs4-zssU, zs7Np, 23*-z4zP~, z41~242m~z43Am and , and fission products of Is4Cs and 1 5 4 E~ were used for evaluating the accuracy of calculation made by CASMO-MICBURN and ORIGEN-2 codes. T h e effect of Gd on the neutron spectrum was taken into account in the CASMO-MICBURN calculation.The amounts of 235U, 239Pu and 241Pu calculated by CASMO-MICBURN agreed well with the observed values within about 3%. On the other hand, the amounts obtained from ORIGEN-2 calculation showed lower values than those observed, especially by -12% in average in 236ufor Gdz03-U02 fuel. 'The main cause of this large difference may be attributed to the effect of Gd on the neutron spectrum. The amounts of the other actinides by both calculation codes revealed no significant difference in nearly 10% except for 24zmAm, in which a large fluctuation among the samples was observed. About 10% difference between the measured values and the calculated values was also observed for Is4Cs, but the calculated values for IS4Eu showed a significant difference from measured values. 242,244Cm

Two-point coupled reactor equations are derived for the analysis of stability of xenon oscillation of coupled thermal reactor by the nodal method with use of Green's function. A simple formula for the stability criteria is obtained as a function of coupling coefficient. As coupling coefficient becomes smaller, xenon oscillation becomes more unstable as expected. Some numerical examples for a coupled slab reactor are given. The present method may be used also for usual thermal reactors by regarding them as coupled reactors by dividing them into appropriate two regions.

No abstract

Two-point coupled reactor equations are derived for the analysis of stability of xenon oscillation of coupled thermal reactor by the nodal method with use of Green's function. A simple formula for the stability criteria is obtained as a function of coupling coefficient. As coupling coefficient becomes smaller, xenon oscillation becomes more unstable as expected. Some numerical examples for a coupled slab reactor are given. The present method may be used also for usual thermal reactors by regarding them as coupled reactors by dividing them into appropriate two regions.