Advanced Designs and Operating Strategies to Enhance the Safety, Operability, and Efficiency of VVER-1000 Reactors

Advanced fuel, burnable absorber, and control rod designs along with advanced fuel management and power distribution control strategies will be implemented in the first operating cycle of the Czech Republic’s Temelin VVER-1000 nuclear power plants. These improvements increase safety margins, enhance operability, and improve fuel efficiency. The Westinghouse WANTAGE 6 fuel assembly design incorporates many proven advanced fuel and core design features used extensively in western pressurized water reactors. The fuel assembly incorporates mixing vane structural grids, radial enrichment zoning, ZrB₂ integral fuel burnable absorbers, axial blankets, and Zircaloy guide thimbles and structural grids. Low-leakage loading patterns are also used to reduce radial neutron leakage. The rod cluster control assembly (RCCA) design incorporates two absorber materials. The absorber tip uses silver-indium-cadmium material while the remainder of the absorber material is B₄C enriched in ¹⁰B. This design increases control rod worth as well as the usable lifetime of RCCA. The Westinghouse constant axial offset control operating strategy, improved RCCA design, modified RCCA overlap, and replacement of part-length RCCA by full-length RCCA are used to improve the axial power distribution control capability for VVER-1000 reactors. These design improvements provide thermal margin benefits, increase shutdown margin by almost 1.0% Ap, reduce fuel cycle costs by nearly 30%, and improve axial power distribution control.