DYMOND (Dynamic Model of Nuclear Deployment) is an Argonne National Laboratory developed and maintained nuclear fuel cycle systems code (NFCS) first developed in 2001, with DYMOND version 6 being the latest stable version (2019). DYMOND simulates the time-dependent behavior and evolution of the entire nuclear fuel cycle including mining, enrichment, fueling, reactors, reprocessing, waste management, disposal, etc. It utilizes a hybrid approach of using agent-based modeling for reactors and fuel batches and system dynamics-based modeling for fuel cycle processes. Given user-specified information about the nuclear fleet and deployment or transition scenario (simulation duration, initial reactors, reactor retirement profile, energy demand, available reactor and fuel technologies, recycling strategies, reactor deployment and fuel use priorities, etc.), DYMOND will calculate the amount of reactors and facilities constructed and retired and all fuel cycle mass flows at each time step to reveal any facility or resource bottlenecks, shortfalls, and surpluses, as well as inventories of materials in storage. DYMOND explicitly tracks 25 nuclides - actinides that have the greatest impact on fuel recycling in advanced reactor concepts - and a lumped material composite of all fission products.

The ORIGEN code is coupled to DYMOND to perform depletion calculations of each fuel batch to provide the detailed isotopics at discharge and after a cooling period that includes radioactive decay using pre-generated reactor-specific depletion libraries in ORIGEN2. These calculations determine the fuel composition after irradiation and cooling from a reactor based on the reactor power and cycle specifications. Decay of materials in all parts of the fuel cycle is also accounted for through a simplified Bateman equation solver for the explicitly tracked nuclides that recalculates material compositions at each month of a simulation. DYMOND also allows the definition of depletion and fuel fabrication recipes if ORIGEN is not available to the user or the additional physics is not required for the model.

The coupling of ORIGEN is also utilized in DYMOND for a more advanced feature - determination of fresh fuel composition requirements through a criticality search - as an alternative to fuel “recipes” or approximate nuclide reactivity worth (i.e., ²³⁹Pu equivalence). This feature more accurately determines fuel requirements from reprocessed material streams for a wider range of reactor designs with minimal approximations and material-stream composition feedback mechanisms. Though the use of these more physically accurate modeling capabilities is more computationally expensive, DYMOND has been made compatible with both concurrent execution and multiple-processor parallelism to off-set the computational cost.

DYMOND v6 allows for a maximum of 5 reactor types with up to 5 fuel batches per core and 3 reprocessing plant types. The simulation can also at most be 300 total years in simulated time. Also, all attributes of a reactor type or reprocessing type (power, capacity factor, final burnup, total capacity, etc.) are fixed for a simulation. However, there have been input strategies developed and implemented to circumvent these restrictions in most cases.

To better understand the models that are being simulated and the result of these uncertainties, DYMOND allows for sensitivity analysis and uncertainty quantification (SA&UQ) via its external coupling with DAKOTA (Design Analysis Kit for Optimization and Terascale Application). These approaches can reveal how the system performance changes as either a single or group of uncertain parameters change. This relationship can be studied through either direct sampling methods and surrogate models to calculate a distribution on system performance measures (i.e., response metrics) and to understand which parameters contribute most to the variance of the response and the synergistic relationships between parameters.