Development of a Molten Salt Reactor specific depletion code MODEC

Molten Salt Reactor (MSR) has the characteristics of on-line reprocessing and continuously refueling, which bring significant differences from traditional reactors in burnup calculations. To handle its specific burnup characteristics, a Molten Salt Reactor specific depletion code - MODEC has been newly developed. MODEC implements two depletion algorithms to solve the basic burnup equations: the transmutation trajectory analysis (TTA) and the Chebyshev rational approximation method (CRAM). To simulate the on-line reprocessing, the fictive decay constant method is applied. And three different methods are implemented in MODEC to solve the nonhomogeneous burnup equations in the continuously refueling problems. Moreover, it can trace in real time the evolution of the in-stockpile nuclides which is extracted by on-line reprocessing. MODEC has three calculating modes for decay, constant flux and constant power calculations. By comparing with ORIGEN-S, the validity of performance of MODEC in conventional burnup calculations, burnup calculations with on-line reprocessing and burnup calculations with continuously refueling is proved. And a comparison of the three methods of solving nonhomogeneous burnup equations is presented and discussed. Additionally, a detailed analysis of error sources in ORIGEN-S is applied and an unpublished error source is found. Finally, a specific Monte Carlo burnup procedure for actual MSR burnup calculations is developed by coupling KENO-VI with MODEC, and the burnup benchmark of Molten Salt Fast Reactor (MSFR) is calculated to validate the specific Monte Carlo burnup procedure.