IMPROVEMENTS IN TIP AND GAMMA SCAN PREDICTIONS IN THE NEXT GENERATION GNF BWR CORE SIMULATOR AETNA02

摘要

Global Nuclear Fuel (GNF)'s next evolution of advanced Boiling Water Reactor (BWR) simulator is the LANCER02/AETNA02 lattice physics/BWR core simulator. A state-of-the-art lattice physics model using two-dimensional Method Of Characteristics (MOC) from LANCER02 is coupled with a three-group semi-analytic nodal method for core flux solution in the AETNA02 core simulator, which is embedded within a flexible online core monitor system. AETNA02 includes a new model for in-core instrument response calculations accounting for intra-nodal power tilt based on MCNP experience which is able to improve the fidelity of predicted Traversing In-core Probe (TIP) signals, particularly for gamma TIP plants, as well as thermal TIP plants. This TIP response model is described and studied within the advanced lattice-physics and core-simulator system LANCER02/AETNA02. In this paper, several plants from the GNF database will be examined and compared to PANAC11 TIP response predictions. Substantial improvement over the previous TIP response model predictive capability is demonstrated in this paper. In addition, pin-by-pin gamma scan comparisons will be presented which also demonstrate the integral effect of both lattice physics and core physics modeling on fidelity compared to physical measurement. The impact of each new model in AETNA02 including the three-group flux solution, the new thermal hydraulic model, the multi-blade and blade depletion feedback, as well as the new TIP model will be studied separately as well as in combination to see the breakdown of improvement as well as the integral improvement. Accuracy in instrument response predictions is a critical part of the amount of adaption necessary and on the reduction of on-line/off-line biases and operational stability. Accuracy in the pin power predictions is closely related to uncertainties used in the establishment of thermal limits.