onix.Sequence

class onix.Sequence(id_number)

The sequence object contains information about the burnup and time sequence that ONIX will follow during simulations.

With the sequence object, the user can:

• Set the macrosteps for the simultion (points in time or burnup at which ONIX will call OpenMC to update the neutron flux and one-group reaction rates)

• Set the microsteps that divide each macrostep (ONIX depletes the system over each microstep)

• Set the normalization for each macrostep (flux or power density)

• Set operational change during the simulation such as temperature changes, density changes or isotopic changes

Each BUCell is automatically associated with a unique copy of the ‘master’ sequence defined by the user. Each sequence object contains data on the evolution of all relevant quantities (\(k_{inf}\), isomeric branchings, neutron flux spectrum, power, flux, burnup and time).

MC_flux_point(s)

Returns the Monte Carlo neutron flux of the BUCell at macrostep s.

Parameters

s (int) – Macrostep number s.

property MC_flux_seq

Returns the Monte Carlo neutron flux macrostep vector (\(cm^{-2}s^{-1}\) per source particle) for the BUCell.

bucell_bu_point(s)

Returns the burnup level of the BUCell at macrostep s.

Parameters

s (int) – Macrostep number s.

property bucell_bu_seq

Returns the burnup macrostep vector (MWd/kg) for the BUCell.

bucell_bu_subpoint(s, ss)

Returns the burnup level of the BUCell at macrostep s and microstep ss.

Parameters

• s (int) – Macrostep number s.

• ss (int) – Microstep number ss.

property bucell_bu_subseq_mat

Returns a list of burnup microstep vectors (MWd/kg) for the BUCell where each microstep vector corresponds to one macrostep.

property current_pow_dens_subseq

Returns the power density microsequence of current macrostep for BUCell

property current_tot_pow

Returns the current total power of the system.

property density_change_dict

Returns the density change dictionnary set by the user.””

property flux_approximation

Returns the method used for approximating the flux between two microsteps

Note: This method should not be used by the user in version 0.1

flux_point(s)

Returns the neutron flux of the BUCell at macrostep s.

Parameters

s (int) – Macrostep number s.

property flux_seq

Returns the neutron flux macrostep vector (\(cm^{-2}s^{-1}\)) for the BUCell.

property flux_spectrum_seq

Returns a list of 300-group neutron flux arrays, one array per macrostep for the BUCell.

flux_subpoint(s, ss)

Returns the neutron flux of the BUCell at macrostep s and microstep ss.

Parameters

• s (int) – Macrostep number s.

• ss (int) – Microstep number ss.

property flux_subseq_mat

Returns a list of neutron flux microstep vectors (\(cm^{-2}s^{-1}\)) for the BUCell where each microstep vector corresponds to one macrostep.

get_bucell_bu_intvl(s)

Gets the burnup interval for the BUCell between macrostep s-1 and macrostep s.

Parameters

s (int) – Macrostep number s.

get_bucell_bu_subintvl(s, ss)

Gets the burnup interval for the BUCell between microstep ss-1 and microstep ss for macrostep s.

Parameters

• s (int) – Macrostep number s.

• ss (int) – Microstep number ss.

get_system_bu_intvl(s)

Gets the average burnup interval for the whole system between macrostep s-1 and macrostep s.

Parameters

s (int) – Macrostep number s.

get_system_bu_subintvl(s, ss)

Gets the average burnup interval for the whole system between microstep ss-1 and microstep ss for macrostep s.

Parameters

• s (int) – Macrostep number s.

• ss (int) – Microstep number ss.

get_time_intvl(s)

Gets the time interval (seconds) between macrostep s nd macrostep s-1

Parameters

s (int) – Macrostep number s.

get_time_subintvl(s, ss)

Gets the time interval (seconds) between macrostep s and macrostep s-1

Parameters

• s (int) – Macrostep number s.

• ss (int) – Microstep number ss.

property isomeric_branching_ratio_seq

Returns the isomeric branching ratios macrostep vector for the BUCell.

kinf_point(s)

Returns the multiplication factor of the BUCell at macrostep s.

Parameters

s (int) – Macrostep number s.

property kinf_seq

Returns the multiplication factor macrostep vector for the BUCell.

property macrostep_unit

Returns the units of the macrosteps.

property macrostep_vector

Returns the macrostep vector.

property macrosteps_number

Returns the number of macrosteps.

property microstep_vector

Returns the microstep vector

microsteps_number(s)

Returns the number of microsteps for macrostep s.

Parameters

s (int) – Macrostep number s.

property norma_unit

Returns the normalization unit.

property norma_vector

Returns the normalization vector.

pow_dens_point(s)

Returns the power density of the BUCell at macrostep s.

Parameters

s (int) – Macrostep number s.

property pow_dens_seq

Returns the power density macrostep vector (\(kW/l\)) for the BUCell.

pow_dens_subpoint(s, ss)

Returns the neutron flux of the BUCell at macrostep s and microstep ss.

Parameters

• s (int) – Macrostep number s.

• ss (int) – Microstep number ss.

property pow_dens_subseq_mat

Returns a list of power density microstep vectors (\(kW/l\)) for the BUCell where each microstep vector corresponds to one macrostep.

set_density_change(cell, cell_density_change)

Manually changes the total density (in atm per \(cm^{3}\)) of the material of the BUCell for user-specified macrosteps.

Note: This method trumps the other method “onix.Sequence.set_isotopic_change”, i.e., the new isotopic densities set in set_isotopic_change will be renormalized by the new value from set_density_change

Parameters

• cell (onix.Cell) – BUCell in which the density change is to be operated

• cell_density_change (dict) – A dictionnary where keys are macrostep numbers (int) and entries are densities in atm per \(cm^{3}\).

set_isotopic_change(cell, cell_isotopic_change, unit='number density')

Manually changes the isotopic densities of user-specified nuclides in a BUCell for user-specified macrosteps.

Note: If the method onix.Sequence.set_density_change is also used for the same BUCell, the isotopic change set by the user must be in atom fraction.

Parameters

• cell (onix.Cell) – BUCell in which the isotopic change is to be operated

• cell_isotopic_change (dict) – A dictionnary where keys are nuclides’ name and entries are evolution sub-dictionnaries. The sub-dictionnaries contain desired density evolution per macrostep where keys are macrostep numbers (int) and entries are densities (unit specified by the user).

• unit (str) – Specifies the unit for isotopic density evolution. ‘number density’ (default) for density in atm per \(cm^{3}\) ‘atom fraction’ for density as atomic fraction

set_macrostep(macrostep_vector, macrostep_unit)

Sets the macrosteps and its units.

Parameters

• macrostep_vector (list) – List of integers defining the points in time or burnup for which OpenMC will be run to update neutron flux and one-group reaction rates.

• macrostep_unit (str) – ‘MWd/kg’ for burnup units or ‘s’ for seconds, ‘m’ for minutes, ‘d’ for days, and ‘y’ for years.

set_master_bucell()

Sets the BUCell against which macrostep normalization is implemented

This feature allows the user to define the sequence steps with the burnup points of the chosen master BUCell

By default, the macrostep normalization is implemented against the whole system and thus the burunup points defined for the sequence are those of the whole system

set_norma(norma_vector, norma_unit)

Sets the normalization for each macrostep.

Note 1: In version 0.10, in standalone mode, the flux set by the user is going to be used for all BUCells of the system. In other words, all BUCells will have the same neutron flux.

Note 2: The user should specify the power density as the total power divided by the total volume of the system. The total volume of the system should include all regions of the system, even regions that are not BUCells (for example, it should include the water region around the fuel BUCell).

Note 3: In version 0.10, the couple mode can only accept constant power depletion (i.e. the normalization should be against power). The standalone mode can only accept constant flux depletion (i.e. the normalization should be against flux)

Parameters

• norma_vector (list) – List of float defining the value of the normalization (kW/l for power density, \(cm^{-2}s^{-1}\) for neutron flux).

• macrostep_unit (str) – ‘power’ for power density, ‘flux’ for neutron flux

set_temperature_change(cell, cell_temperature_change)

Manually changes the temperature (Kelvin) of the material of the BUCell for user-specified macrosteps

Parameters

• cell (onix.Cell) – BUCell in which the temperature change is to be operated

• cell_temperature_change (dict) – A dictionnary where keys are macrostep numbers (int) and entries are temperature in Kelvin.

system_bu_point(s)

Returns the average burnup level of the whole system at macrostep s.

Parameters

s (int) – Macrostep number s.

property system_bu_seq

Returns the average burnup macrostep vector (MWd/kg) for the whole system.

system_bu_subpoint(s, ss)

Returns the average burnup level of the whole system at macrostep s and microstep ss.

Parameters

• s (int) – Macrostep number s.

• ss (int) – Microstep number ss.

property system_bu_subseq_mat

Returns a list of average burnup microstep vectors (MWd/kg) for the whole system where each microstep vector corresponds to one macrostep.

property temperature_change_dict

Returns the density change dictionnary set by the user.””

time_point(s)

Returns the time (seconds) for macrostep s

Parameters

s (int) – Macrostep number s.

property time_seq

Returns the macrostep vector in time (seconds).

time_subpoint(s, ss)

Returns the time (seconds) for macrostep s and microstep ss

Parameters

• s (int) – Macrostep number s.

• ss (int) – Microstep number ss.

property time_subseq_mat

Returns a list of time microstep vectors (seconds) where each microstep vector corresponds to one macrostep.

tot_pow_point(s)

Returns the total power value for macrostep s

Parameters

s (int) – Macrostep number s.

property tot_pow_seq

Returns the sequence of total power of the system.