THE NEUTRONICS OF INCREASED POWER DENSITY PWR CORE BASED ON ANNULAR FUEL RODS USING THE MONTE CARLO METHOD

Abstract

In this study the design parameters of the annular fuel cell are investigated and verified  using  the  Monte  Carlo  method.  The  annular  design  shows  a  comparable neutronic  performance   to  the  solid  fuel  design  as  the  difference  in  the  infinite multiplication factor ( k∞ ) is far less than 1% and the difference from published work is within 1% [1]. This new design concept of annular fuel pins arranged in a 13 by 13 fuel assemblies has been suggested first at the Massachusetts Institute of Technology (MIT) where they have claimed a 150% power increase (3411 to 5111 MWt) without affecting the thermal and safety margins. Having established the confidence in the fuel cell design parameters, a detailed assembly and core model is described. The difficult part of the procedure  is  the  Gadolinium  burnable  poison  management  where  not  all  rods  are poisoned and not all have the same mass fraction besides that some assemblies have highly enriched fuel rods and others have low enrichment ones. This lengthy iterative process is conditioned by less power fluctuations and by having enough amount of negative reactivity to cancel out the excess reactivity required for the fuel to deplete. The remaining 9% of excess reactivity is matched by 370 ppm of soluble boron to make the core critical. Therefore the X-Y fast and thermal flux and power map of the core and assembly  in  addition  to  axial  power  profiles  in  the  core  and  hottest  and  average assembly and the hottest