An expert system for fuel failure diagnosis in EBR-2

Since 1977, a program has been under way at Experimental Breeder Reactor 2 (EBR-2) to evaluate the performance of metal and mixed-oxide fuel elements after clad failure (breach). The motivation for this activity, called run-beyond-cladding-breach testing, is to continue safe operation of EBR-2 after occurrence of single or multiple clad failures. An expert system has been designed for identifying and surveying breached elements in EBR-2. It contains as a knowledge base (a) the already developed and validated analytical models (i.e., tag gas, delayed neutron, and fission gas analyses), (b) rules obtained from inductive learning, and (c) rules obtained from new data. In the design of the expert system, the analytical models used by the domain experts as diagnostic tools (i.e., interpreting tag gas, delayed neutron, and fission gas) were incorporated in the knowledge base. Gas tagging consists of the addition of small amounts of gas that has a unique isotopic composition to fuel pins of each subassembly. When a fuel element fails during subsequent irradiation, the unique composition of tag gas added to the fuel elements allows identification of the subassembly. This is done by a mass spectrometric analysis of the reactor cover gas into which the gas from themore » failed fuel is incorporated. By using this method, the subassembly that contains the failed fuel element can be identified.« less