Modelling and verification of the PWR burnable poison designs by ELCOS code system

A PWR core of a current design was used as a test problem for a verification of the ELCOS computational system. The chosen core was relatively complex, including 11 fuel types, differing by fuel enrichment and Burnable Poison (BP) design. Two main BP designs were modelled: WABA and IFBA as well as a combination of both. Results of the calculations were compared with utility data, and demonstrated the adequacy of the ELCOS system. The modelling of the BP designs was carried out by performing a series of calculations with different time-step lengths and poison spatial representation. It was found that relatively simple models are sufficiently accurate in simulating core behaviour with accuracy of about 1 mK. Comparison of the depletion rate of two BP designs indicated potential benefits in using a combination of both designs in a single fuel assembly.