BWR fuel channel experience

Use of fuel channels for periods exceeding one fuel bundle lifetime requires that the dimensions of the channels must not change excessively during service and that corrosion of the channel material must not lead to heavy spalling of oxides and significant thinning of the channel walls. To manufacture channels with good dimensional stability, residual stresses imposed by bending and welding operations must be eliminated. This is done by ASEA-ATOM in a sizing operation where the channels are uniformly and plastically deformed at high temperature (≥ 600 deg. C). Processing of the Zircaloy channel material is important. Introduction of a high temperature anneal and quenching operation at either final or intermediate size in the channel strip fabrication route has proved beneficial for the material corrosion resistance. The main in-pile dimensional changes are channel bowing and channel bulging