Verification of the nTRACER/CTF code system for full core high resolution cycle analysis with the OECD/NEA TVA Watts Bar Unit 1 benchmark

This study aims to develop and verify the multi-physics high-resolution coupled code system nTRACER/CTF for full core depletion calculations in Cartesian geometry. The verifications are conducted on the basis of the OECD/NEA TVA Watts Bar 1 benchmark (TVA WB1), using multi-physics high-resolution results from the Virtual Environment for Reactor Applications (VERA), which includes MPACT and CTF. The paper presents the development of the nTRACER/CTF coupled system for depletion calculations in PWRs, which are based on the Cartesian geometry. The nTRACER/CTF model is verified under the Hot Zero Power Condition (HZP) at the beginning of the first cycle and the HFP case of TVA WB1. The Critical Boron Concentration (CBC) differences are less than 17 ppm in both cases, while the RMS differences in pin-wise power distributions are less than 0.7 % in both cases. The impacts of discrepancies between the nTRACER/CTF and VERA models are also quantified. nTRACER/CTF depletion calculations are performed for the full first cycle of TVA WB1 according to the simplified power curve presented in the benchmark specifications. The system is verified with VERA results for every burnup step of the cycle, in terms of CBC, axially averaged pin power distribution, outlet temperature distribution and axial power profile. The RMS of CBC differences after achieving a full power condition is 25 ppm. The RMS differences in pin-wise power and outlet temperature distributions are less than 1.12 % and 0.4 °C, which are within the target accuracies of 1.5 % and 2 °C for all depletion steps.