Problems of fabricating fuel elements for WWER-1000 water cooled reactors for operation during manoeuvring modes and elevated burnup

The operating conditions of nuclear power plant fuel elements during power cycling are examined. The negative effect of certain fission products on the zirconium cladding of the fuel elements and the possible consequences of this, particularly in transient modes, are discussed. A comparison is made between the effects of various transient modes on fuel element performance. In order to increase fuel element efficiency during cycling operations, the use of bimetallic zirconium cladding and fuel with elevated plasticity and creep properties is considered. The results of reactor tests on experimental WWER fuel assemblies during burnup of more than 75,000 MW·d/t uranium are briefly discussed. (author). 1 ref., 5 figs, 2 tabs