E110 alloy (Zr-1%Nb) has been the universal fuel cladding in the Voda Voda Energo Reactor (VVER) design, which is a pressurized water reactor (Cox et al. , 2004). In the early VVER-440 (MWe) reactors the fuel assem­blies were hexagonal arrays of 126 E110 clad fuel rods, with 10 or 11 stainless steel grid spacers, enclosed in an E125 hexagonal wrapper (which performs the same function as a BWR channel) (Smirnov et al, 1994) see Fig. 4.6a. In the VVER-1000 type reactors each assembly contains 312 fuel rods, a central E125 alloy support tube and 18 stainless steel guide tubes for control and shut-down rods. Except for the first VVER-1000 (Novo-Voronezh-5) such VVER-1000 fuel assemblies do not have ‘wrappers’.