Abstract
Due to cost effective and simplicity homogeneous reactors have been widely used for experimental and research purposes. Parameters which are difficult to get from a heterogeneous reactor system can be easily obtained from a homogeneous reactor system and can be applied in the heterogeneous reactor system if the major parametric differences are known. In this study, homogenization effects of VVER (Water Water Energetic Reactor)-1000 fuel assembly on neutronic parameters have been analyzed with the universal probabilistic code MCNP (Monte Carlo N-Particle). The infinite multiplication factor (k∞) has been calculated for the reconfigured heterogeneous and homogenous fuel assembly models with 2 w/o U-235 enriched fuel at room temperature. Effect of mixing soluble boron into the moderator/coolant (H2O) has been investigated for both models. Direct and fission detected thermal to higher energy neutron ratio also has been investigated. Relative power distributions of both models have been calculated at critical and supercritical states. Burnup calculations for both the reconfigured cores have been carried out up to 5 years of operation. Effective delayed neutron fraction (βeff) and prompt removal lifetime (ℓ) also have been evaluated. All the results show significant differences between the two systems except the average relative power.
Highlights
A nuclear reactor can be classified into: (a) homogeneous (HOM) system, and (b) heterogeneous (HET) system according to placements of fuel material into the active core
The effects of homogenization on neutronic parameters of VVER-1000 fuel assembly geometry are systematically estimated through comparisons between reconfigured HET and HOM models
In order to find out all the neutronic parameters, the universal computer code MCNP has been used
Summary
A nuclear reactor can be classified into: (a) homogeneous (HOM) system, and (b) heterogeneous (HET) system according to placements of fuel material into the active core. A HOM and a HET VVER-1000 fuel assembly models have been developed to investigate the homogenization effects on the criticality calculations. The radial power peaking factor is calculated for both the systems The kinetic parameters such as effective delayed neutron fraction (βeff) and prompt neutron lifetime (l) play an important role in the reactivity transient analysis, safety, and control of nuclear reactors. Prompt neutron lifetime is the average time from the emission of a prompt neutron in fission to the removal of the neutron by some physical process such as escape, capture, or fission Both of these parameters have been calculated for MCNP VVER-1000 fuel assembly models at the BOC
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