Irradiation histories

This is the general object used to define and store the definition of burnup steps as well as the state of the model during irradiation. The top level IrradiationHistory is simply a sequence of IrradiationStep and DecayStep entries, with a number of convenience function to add steps and extract data.

An irradiation history instance has the following parameters:

irr.start_time

: datetime

Calender date and time when the irradiation starts. All applications will set this automatically from it’s time_stamp parameter.

irr.step_type

: Tag

 = `delta`

Indicate if the duration of irradiation steps are specified as absolute or cumulative values. For the latter case, each duration indicates the total time since the start of the irradiation history.

Use the tag delta to indicate that each step will specify its duration since the previous step, and cumulative if step sizes are cumulative.

irr.xenon_mode

: Tag

 = `calculated`

How xenon build up should be treated. There are two options:

  • calculated: The xenon build up should be explicitly calculated, or burned in. This usually requires the use of small irradiation steps to account for the rapid change in material compositions.

  • equilibrium: Set the xenon at its equilibrium value, assuming a constant power (see below).

Attention

Currently the equilibrium option will triggers the relevant option in a target code, and performs no independent equilibrium xenon estimation. It should therefore only be used with target codes that supports this option.

irr.time_stepping_algorithm

: Tag

 = `predictor_corrector`

How the change in material properties during an irradiation step should be estimated. The following options are supported:

  • predictor_corrector: Perform a predictive flux calculation with material properties fixed at their beginning of step values, deplete materials using the flux to estimate reaction rates, then repeat the process with materials at the new state. The final material composition is estimated as a linear combination of the two calculations. Thus, each depletion step requires two flux, and two depletion calculations.

  • backwards: This assumes that the change in material compositions won’t affect the flux distribution. Thus a single flux calculation is used to deplete the materials for the step.

Note

The algorithm used applies to all steps, and can not be changed for individual steps.

Attention

Currently, for multi-step depletion calculations, the predictor_corrector option is only available for target codes that supports it.

irr.base_power

: power

 = Custom

The base (or default) power for the irradiation history. If not specified, the model’s design power will be assumed.

irr.rig_loader

Object used to deduce the rig loading during the irradiation history. It should only be specified if you plan to load, unload or move intra assembly components during the irradiation.

The loader’s function is to interpret rig schedules from the plant data, and return real model elements. Setting up rig loading for you model is described here.

Irradiation steps are added to the irradiation history instance using the following two methods:

irradiation_history.add_decay_step(duration, **kwargs)

Adds a pure decay (zero power) step.

Parameters:

  • duration (time.) – Total duration of the step, either relative to the previous step, or relative to the beginning of the irradiation history if step_type is cumulative.

  • **kwargs –

    Any additional parameters defining a general step.

Returns:

A DecayStep instance.

For example, to add a decay step of two days and save the assembly material compositions at the end of the step:

irradiation_history.add_decay_step(2 * units.days, save=True)
irradiation_history.add_step(duration, **kwargs)

Adds an active irradiation step.

Parameters:

  • duration (time.) – Total duration of the step, either relative to the previous step, or relative to the beginning of the irradiation history if step_type is cumulative.

  • **kwargs –

    Any additional parameters defining a basic,

or active or active step. :returns: An IrradiationStep instance.

For example, to add an irradiation step of two days, with average tep power of 2 mega watt:

irradiation_history.add_step(2 * units.days, power=2 * units.MW)

Note

When required parameters, e.g power or average_bank is not specified, it will be inherited from the previous step added to the irradiation history.

Alternatively, instead of specifying parameters during step addition, they can be set in the returned object:

step = irradiation_history.add_step(2 * units.days)
step.power = 2 * units.MW
step.average_banks = control.percentage_inserted(54.0)

General parameters defining an irradiation step

irr.duration

: time

!

The total duration of the step. This is the delta step time, or the step time since start of the irradiation if step_type was set to cumulative

irr.save

: bool

 = False

Flag indicating if the material compositions at the end of the step should be saved to the inventory.

Note

For calculations that modify an inventory, only the material states at the beginning and end of the irradiation is saved by default. Use this flag if you want additional snap shot states in the irradiation period to be saved.

Attention

This parameter is never inherited from previous steps, and must be explicitly switched on for the desired steps.

irr.critical_power

: power

Optional flag that indicates the real power (as opposed to the average power), at the end of the step. It is used for end of step flux calculations. If these calculations are not going to be performed, this parameter need not be specified.

irr.critical_banks

: dict or travel

Optional flag that indicates the real bank position(s) (as opposed to average_banks), at the end of the step. Either a single travel instance, if all banks have the same position, or a dict instance mapping bank names to positions.

It used for end of step flux or criticality calculations. If these calculations are not going to be performed, this parameter need not be specified.

irr.step_rigs

State of rigs (or inter assembly loadable components), that will be used during the irradiation step (that is, to activate and decay materials). Must be a value that can be interpreted by rig_loader.

irr.critical_rigs

State of rigs (or inter assembly loadable components), at the end of the irradiation step. Must be a value that can be interpreted by rig_loader.

It used for end of step flux or criticality calculations. If these calculations are not going to be performed, this parameter need not be specified.

Note

Parameters related to bank positions (e.g critical_banks, average_banks), are optional, and only makes sense when the underlying model has banks defined.

Additional parameters for depletion steps

Apart from the base parameters, the following must be set for active depletion steps:

irr.power

: power

!

The average core neutronic power used during the irradiation step. This is the value that will be used to scale fluxes when calculating reaction rates.

irr.average_banks

: dict or travel

Position of the banks used when calculating fluxes for the depletion calculation. This is usually taken to be the average bank position for the duration of the step. Either a single travel instance, if all banks have the same position, or a dict instance mapping bank names to positions.

Useful methods

The following lists a number of queries that can be performed on the irradiation history instance:

irradiation_history.duration()

Get the total duration of the entire irradiation history.

Returns:

A quantity with time dimensions.

irradiation_history.total_power_delivered()

The total power delivered for the entire irradiation history.

Returns:

A quantity with power times time dimensions.

irradiation_history.step_frame(step_index)

Get the start and end time of a step.

Parameters:

step_index (int) – The step number.

Returns:

Two datetime values, with the first value the step start time, and the second the step end time.