SUMMARY

A new utility has been developed with extensive capabilities in identifying nuclide decay and transmutation characteristics, allowing for accurate and efficient tracking of the change in isotopic concentrations in nuclear reactor fuel over time. This tool, named the Application Programming Interface for Depletion Analysis (APIDA), employs both a matrix exponential method and a linear chain method to solve for the end-of-time-step nuclide concentrations for all isotopes relevant to nuclear reactors. The Chebyshev Rational Approximation Method (CRAM) was utilized to deal with the ill-conditioned matrices generated during the course of lattice depletion calculations, and a complex linear chain solver was developed to handle isotopes reduced from the burnup matrix due to either radioactive stability or a sufficiently low neutron-induced reaction cross section. The entire tool is housed in a robust but simple application programming interface (API). The development of this API allows other codes, particularly numerical neutron transport solvers, to incorporate APIDA as the burnup solver in a lattice depletion code in memory, without the need to write or read from the hard disk. Specifically, APIDA was developed for coupling with the coarse mesh radiation transport method (COMET) – a numerical transport solver extensively validated and shown to provide efficient and accurate whole core solutions to host of different reactor types. A first order coupling was completed to show the potential of APIDA and COMET as a novel lattice depletion solver. The APIDA code was also benchmarked using numerous decay and transmutation chains. Burnup solutions produced by APIDA were shown to provide material concentrations comparable to the analytically solved Bateman equations - well below 0.01% relative error for even the most extreme cases using isotopes with vastly different decay constants. For further benchmarking, APIDA was coupled with the transport solver in the SERPENT code for a fuel pin cell depletion problem. A sensitivity analysis was also conducted to determine the optimal number of isotopes to track for a typical pressurized water reactor (PWR) problem in order to accurately track the change in eigenvalue of the core. Results show APIDA to be effective and efficient in solving lattice depletion problems, in addition to being successful in terms of portability for users to implement via the API.