Omid Safarzadeh - Shahed University, P.O. Box: ۳۳۱۹۱۱۸۶۵۱, Tehran, Iran
Farahnaz Saadatian-Derakhshandeh - Shahid Beheshti University, P.O. Box: ۱۹۸۳۹۶۹۴۱۱, Tehran, Iran

The effective β-fraction has a key role in the dynamic response of the reactor. This study aims to assess the suitability and accuracy of the detailed models of DRAGON۵ and DONJON۵ code for estimation of the effective fraction of delayed neutron for the VVER-۱۰۰۰ reactor core. DRAGON۵ is adopted to homogenize and condense lattice physics constants of fuel assemblies during fuel burnup, followed by DONJON۵, which is used to calculate forward and adjoint flux profiles on the reactor core geometry. A thermal-hydraulic subroutine is developed for VVER-۱۰۰۰ reactor hollow fuel pellets to embody the reactivity feedback raised by changing the reactor power profile. The effective β-fraction is evaluated for each fissile and fertile isotopes in terms of fuel burnup. The results of the coupling scheme are evaluated using the KASKAD code package of Bushehr NPP-I (BNPP-I). The results indicate that the use of SHI and SYBILT modules of DRAGON۵ are essential to achieve reasonably precise resolution.

Effective delayed neutron fraction, VVER-۱۰۰۰, Burnup, DRAGON۵, DONJON۵