openmc.deplete – Depletion¶
The two primary requirements to perform depletion with
A transport operator
A time-integration scheme
The former is responsible for calculating and retaining important information
required for depletion. The most common examples are reaction rates and power
normalization data. The latter is responsible for projecting reaction rates and
compositions forward in calendar time across some step size \(\Delta t\),
and obtaining new compositions given a power or power density. The
CoupledOperator class is provided to obtain reaction rates via tallies
through OpenMC’s transport solver, and the
IndependentOperator class is
provided to obtain reaction rates from cross-section data. Several classes are
provided that implement different time-integration algorithms for depletion
calculations, which are described in detail in Colin Josey’s thesis,
Development and analysis of high order neutron transport-depletion coupling
Deplete using a first-order predictor algorithm.
Deplete using the CE/CM algorithm.
Deplete using the CE/LI CFQ4 algorithm.
Deplete using the CF4 algorithm.
Deplete using the EPC-RK4 algorithm.
Deplete using the LE/QI CFQ4 algorithm.
Deplete using the SI-CE/LI CFQ4 algorithm.
Deplete using the SI-LE/QI CFQ4 algorithm.
Each of these classes expects a “transport operator” to be passed. OpenMC provides the following transport operator classes:
Transport-coupled transport operator.
Transport-independent transport operator that uses one-group cross sections to calculate reaction rates.
IndependentOperator class requires a set of fluxes and microscopic
cross sections. The following function can be used to generate this information:
Generate a microscopic cross sections and flux from a Model
A minimal example for performing depletion would be:
>>> import openmc
>>> import openmc.deplete
>>> geometry = openmc.Geometry.from_xml()
>>> settings = openmc.Settings.from_xml()
>>> model = openmc.model.Model(geometry, settings)
# Representation of a depletion chain
>>> chain_file = "chain_casl.xml"
>>> operator = openmc.deplete.CoupledOperator(
... model, chain_file)
# Set up 5 time steps of one day each
>>> dt = [24 * 60 * 60] * 5
>>> power = 1e6 # constant power of 1 MW
# Deplete using mid-point predictor-corrector
>>> cecm = openmc.deplete.CECMIntegrator(
... operator, dt, power)
Internal Classes and Functions¶
When running in parallel using mpi4py, the MPI intercommunicator used can
be changed by modifying the following module variable. If it is not explicitly
modified, it defaults to
MPI intercommunicator used to call OpenMC library
During a depletion calculation, the depletion chain, reaction rates, and number densities are managed through a series of internal classes that are not normally visible to a user. However, should you find yourself wondering about these classes (e.g., if you want to know what decay modes or reactions are present in a depletion chain), they are documented here. The following classes store data for a depletion chain:
Full representation of a depletion chain.
Decay mode information
Decay modes, reactions, and fission yields for a single nuclide.
Transmutation reaction information
Energy-dependent fission product yields for a single nuclide
Mapping for fission yields of a parent at a specific energy
Chain class uses information from the following module variable:
Dictionary that maps transmutation reaction names to information needed when a chain is being generated: MT values, the change in atomic/mass numbers resulting from the reaction, and what secondaries are produced.
The following classes are used during a depletion simulation and store auxiliary data, such as number densities and reaction rates for each material.
Stores local material compositions (atoms of each nuclide).
Microscopic cross section data for use in transport-independent depletion.
Result of applying transport operator
Reaction rates resulting from a transport operator call
Results from a depletion simulation
Result of a single depletion timestep
The following class and functions are used to solve the depletion equations,
cram.CRAM48() being the default.
CRAM depletion solver that uses incomplete partial factorization
Solve depletion equations using IPF CRAM
Solve depletion equations using IPF CRAM
Deplete materials using given reaction rates for a specified time
Boolean switch to enable or disable the use of
multiprocessingwhen solving the Bateman equations. The default is to use
multiprocessing, but can cause the simulation to hang in some computing environments, namely due to MPI and networking restrictions. Disabling this option will result in only a single CPU core being used for depletion.
The following classes are used to help the
compute quantities like effective fission yields, reaction rates, and
total system energy.
Class that computes fission yields based on average fission energy
Computes normalization using fission Q values from depletion chain
Class that uses a single set of fission yields on each isotope
Class for generating one-group reaction rates with direct tallies
Class responsible for obtaining system energy via a tally score
Helper that computes fission yields based on a cutoff energy
Class that generates one-group reaction rates using multigroup flux
openmc.deplete.IndependentOperator uses inner classes subclassed
from those listed above to perform similar calculations.
The following classes are used to define transfer rates to model continuous removal or feed of nuclides during depletion.
Class for defining continuous removals and feeds.
Specific implementations of abstract base classes may utilize some of the same methods and data structures. These methods and data are stored in intermediate classes.
Methods common to tally-based implementation of
are stored in
Abstract class for computing fission yields with tallies
Methods common to OpenMC-specific implementations of
are stored in
Abstract class holding OpenMC-specific functions for running depletion calculations.
Abstract Base Classes¶
A good starting point for extending capabilities in
to examine the following abstract base classes. Custom classes can
abc.TransportOperator to implement alternative
schemes for collecting reaction rates and other data prior to depleting
Abstract class defining a transport operator
The following classes are abstract classes used to pass information from
transport simulations (in the case of transport-coupled depletion) or to
simply calculate these quantities directly (in the case of
transport-independent depletion) back on to the
Abstract class for obtaining normalization factor on tallies
Abstract class for processing energy dependent fission yields
Abstract class for generating reaction rates for operators
Custom integrators or depletion solvers can be developed by subclassing from the following abstract base classes:
Abstract class for solving the time-integration for depletion
Abstract class for the Stochastic Implicit Euler integrators
Abstract class for solving depletion equations