| Although relatively rare in CANDU plants, fuel defects have always been an important operating concern for CANDU fuel operation and behaviour, and play a critical role in health, safety, and the economics of an operating reactor. A fuel defect occurs when a fuel element has a breach in its sheath resulting in fission product (FP) release and/or uranium fuel loss into the reactor primary heat transport system (PHTS). The unintended release of FP and fuel material into the PHTS creates elevated radiation fields and hazards for the reactor operator. The intent of this thesis is to develop an online real-time system that can analyse PHTS activity and infer information relating to otherwise unknown defect(s) in the reactor core.;A MATLABRTM based Graphical User Interface (GUI) programme called COLDD (CANDU On-Line Defected fuel Diagnostic) has been developed to provide detailed diagnostics of PHTS activities. COLDD is based on new techniques, a new empirical diffusion coefficient, new algorithms, and refinement of existing techniques. Several techniques are based on detailed mechanistic models that are presented in detail, while other techniques are based on empirical rules from experimental and commercial experience; the diversity of techniques are shown to be self-consistent. The techniques employed by COLDD are compared to techniques used internationally by other defected fuel diagnostic tools for non-CANDU type reactors.;The ability for COLDD to perform successful defected fuel diagnostics is dependent on the quality of the data provided. A detailed sensitivity analysis is performed to determine key measurement parameters. Techniques are also developed to allow operators to perform robust error checking of data to ensure consistency.;COLDD is validated against theoretical, experimental, and commercial reactor data, and shown to be stable and consistent in all cases. The plethora of analysis modes are shown to be self-consistent. The version of COLDD described in this thesis is considered a Beta version ready for testing at a commercial station, and for development to add and improve algorithms and the user interface. There are several possible improvements discussed, including gaps in defected fuel understanding that require further research. COLDD is highly stable and has been demonstrated to be effective; it is a new powerful tool in the arsenal ofa reactor operator faced with defected fuel in core.;Key words: Defected fuel, CANDU, Nuclear, Fission Product Release, Diagnostic. |
