Materials and Processing Considerations in the Brazing of Appendages on CANDU Fuel Bundles

It is expected that in the near future, CANDU fuel bundle manufacturing will be confronted with more stringent regulations concerning airborne beryllium particle concentrations (40 time reduction). Two approaches were considered to provide guidance in potential alteration in manufacturing steps involving brazing.;In case future regulations will further constrain the use of beryllium, a pre-study in alternative brazing material was performed. In this study a method was developed to select other metals that may braze Zircaloy at low temperatures to minimize or eliminate the impact of the brazing process concerns on fuel bundle manufacturing. Although the method was tested by means of several experiments involving commercial production facilities, and the impact of the new material on several in-reactor factors was discussed, it is deemed necessary to extend this testing of materials considerably in the reactor environment.;A short term approach focused on the reduction of the current beryllium containing airborne particle levels with minimum impact to existing practices. In this approach, the levels of airborne beryllium were measured and the main processes by which the airborne particles originate were identified. Computational thermodynamics provided insight in the outgassing partial pressures for each identified process. This insight was used to suggest several attainable process improvements which may be immediately implemented. Based on the insight, it is expected that after the implementation of the suggested improvements, the production will be in full compliance with the newly proposed Be airborne regulation.