VEGAS: A fuel cycle simulation and preconditioner tool with restricted material balances

This paper introduces VEGAS, a lightweight and fast-executing fuel cycle simulator primarily intended to augment higher-fidelity fuel cycle simulators. VEGAS can act as a preconditioner as well as a platform for implementing endogenous decision making within these simulators. In preconditioner mode, VEGAS offers an iterative method for accelerating the convergence of fuel cycle optimization problems while ensuring that material balance and other constraints are met. The methodology utilized by VEGAS, particularly its mass balance and reactor deployment algorithms, is presented here. Unique to the VEGAS simulator is a rollback feature that undoes reactor build decisions if material balance constraints are violated. Included in the VEGAS code is an economics package, also documented here, that calculates the evolving levelized cost of electricity. Benchmark comparisons against the VISION (Verifiable Fuel Cycle Simulation Model) simulator are also presented, along with an example of VEGAS's preconditioning capability in which the objective is to achieve a target system transuranics inventory while installing as little reprocessing capacity as possible.