Nuclear Science and Engineering / Volume 167 / Number 3 / March 2011 / Pages 230-241
The first application of CASMO-4/MICROBURN-B2 methodology to Westinghouse SVEA-96 Optima2 reload cycle is described in this paper. The first Westinghouse Optima2 reload cycle in the United States is Exelon's Quad Cities Unit 2 Cycle 19 (Q2C19). The core contains fresh Optima2 fuel and once-burned and twice-burned GE14 fuel. Although the licensing analyses for the reload cycle are performed by Westinghouse with Westinghouse methodology, the core is monitored with AREVA's POWERPLEX-III core monitoring system that is based on the CASMO-4/MICROBURN-B2 (C4/B2) methodology. This necessitates the development of a core model based on the C4/B2 methodology for both reload design and operational support purposes. In addition, as expected, there are many differences between the two vendors' methodologies; they differ not only in modeling some of the physical details of the Optima2 bundles but also in the modeling capability of the computer codes. In order to have high confidence that the online core monitoring results during the cycle startup and operation will comply with the technical specifications requirements (e.g., thermal limits, shutdown margins), the reload core design generated by Westinghouse design methodology was confirmed by the C4/B2 model. The C4/B2 model also ensures that timely operational support during the cycle can be provided. Since this is the first application of C4/B2 methodology to an Optima2 reload in the United States, many issues in the lattice design, bundle design, and reload core design phases were encountered. Many modeling issues have to be considered to develop a successful C4/B2 core model for the Optima2/GE14 mixed core. Some of the modeling details and concerns and their resolutions are described. The Q2C19 design was successfully completed, and the 2-yr cycle successfully started up in April 2006 and shut down in March 2008. Some of the operating results are also presented.