Burnup and Rod Worth Calculations for Paks-2 Using the Code DYN3D with two Different Group Data Libraries

The AER benchmark problem defined by L. Korpas et al. for the calculation of VVER­440 control rod worth was solved by using the code DYN3D in 1994. The KAB MAGRU library, generated by the NESSEL code was used then as a source of macroscopic group data. Now DYN3D calculations have been repeated with a new group data library created in EGP Prague by the KASSETA code. Burnup calculations have been carried out for the cycles 4 to 7 of Paks­2 NPP. The critical boron concentrations as a function of time, calculated with both data libraries, were compared to the values measured in the progress of the cycles. The results are in good agreement. The comparison of the fuel­element averaged burnup values after calculating 4 full cycles shows a maximum deviation of about 2 percent between the two data libraries. Concerning the control rod efficiencies the relative deviation is higher. This is due to relatively great differences in the macroscopic group data produced for the control rod!
s by NESSEL and KASSETA. The deviations between results calculated by the same code with different group data indicate that using different data libraries by the AER benchmark participants may be a main reason for the high differences between their results.