Full-Core Cycle Analysis for the OECD/NEA TVA Watts Bar Unit 1 Benchmark with CMSYS Code System

This study presents a full-core cycle analysis of the Organisation for Economic Co-operation and Development, Nuclear Energy Agency, Tennessee Valley Authority (TVA) Watts Bar Unit 1 (WB1) benchmark using the Paul Scherrer Institute Core Management System (CMSYS), based on the Studsvik codes CASMO-5, CMSLink, and SIMULATE-5. The analysis includes all seven exercises of the TVA WB1 benchmark, covering zero-power physics tests (ZPPTs) and depletion calculations for three consecutive cycles of operation, with cross verification against plant measurements and published KENO-VI, VERA, and nTRACER/CTF results. For the Cycle 1 ZPPT, compared to the measurements, the results predicted by CMSYS have 186 pcm difference for critical eigenvalues, 66 pcm for single control rod worth (CRW), and 119 pcm for total CRW. During Cycle 1 depletion, the critical boron concentration letdown curve agrees with the measurements within 23 ppm; corresponding maximum deviations are within 47 ppm for Cycles 2 and 3. Pin-by-pin radial power comparisons against VERA show generally small discrepancies in the core interior and larger differences near the periphery, while axial peak power differences remain limited to −0.53% at the beginning of cycle, 0.23% at the middle of cycle, and 2.72% at the end of cycle. Overall, the results demonstrate that CMSYS provides accurate and consistent full-cycle predictions for the WB1 benchmark and supports its use for high-resolution pressurized water reactor core analysis.