# UOvar element = document.getElementById("moose-equation-4003a859-f150-4ed9-af0d-f21865185eb4");katex.render("_2", element, {displayMode:false,throwOnError:false}); Axial Relocation Eigenstrain

This model accounts for the in the effective diameter of a crumbled layer of fuel during axial relocation under Loss of Coolant Conditions.

## Description

The UO2AxialRelocationEigenstrain computes a strain to be applied in the radial direction in axial layers of fuel that have crumbled determined by the AxialRelocationUserObject. The strain is calculated using the current inner cladding radius and original pellet radius for the layer.

When a layer crumbles the effective diameter of the fuel moves into contact with the cladding. To ensure the domain on which the heat equation is applied is correct, the mesh must be moved. This is accomodated by this eigenstrain. Note that the inclusion of a ficticious strain does not affect the solution because after crumbling the stress and strain state within the fuel is meaningless. The eigenstrain is calculated by: (1) where is the cladding inner radius, is the residual gap size (default is 2), and is the fuel outer radius at the time fuel gain is first calculated to occur. The definition of the residual gap is illustrated in Figure 1:

Figure 1: Change in fuel geometry and effective fuel density following fuel pellet collapse in the ballooned region of the cladding. A residual gap is assumed to remain.

## Example Input Syntax


[./axial_relocation_strain]
type = UO2AxialRelocationEigenstrain
axial_relocation_object = axial_relocation
eigenstrain_name = axial_relocation
[../]
(test/tests/axial_relocation/axial_relocation_eigenstrain.i)

## Input Parameters

• axial_relocation_objectName of the AxialRelocationUserObject that determines whether the fuel has crumbled.

C++ Type:UserObjectName

Description:Name of the AxialRelocationUserObject that determines whether the fuel has crumbled.

• eigenstrain_nameMaterial property name for the eigenstrain tensor computed by this model. IMPORTANT: The name of this property must also be provided to the strain calculator.

C++ Type:std::string

Description:Material property name for the eigenstrain tensor computed by this model. IMPORTANT: The name of this property must also be provided to the strain calculator.

### Required Parameters

• computeTrueWhen false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the Material via MaterialPropertyInterface::getMaterial(). Non-computed Materials are not sorted for dependencies.

Default:True

C++ Type:bool

Description:When false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the Material via MaterialPropertyInterface::getMaterial(). Non-computed Materials are not sorted for dependencies.

• base_nameOptional parameter that allows the user to define multiple mechanics material systems on the same block, i.e. for multiple phases

C++ Type:std::string

Description:Optional parameter that allows the user to define multiple mechanics material systems on the same block, i.e. for multiple phases

• boundaryThe list of boundary IDs from the mesh where this boundary condition applies

C++ Type:std::vector

Description:The list of boundary IDs from the mesh where this boundary condition applies

• axial_axis1Coordinate axis of the axial direction of the fuel stack (0, 1, or 2 for x, y, or z

Default:1

C++ Type:unsigned int

Description:Coordinate axis of the axial direction of the fuel stack (0, 1, or 2 for x, y, or z

• blockThe list of block ids (SubdomainID) that this object will be applied

C++ Type:std::vector

Description:The list of block ids (SubdomainID) that this object will be applied

### Optional Parameters

• enableTrueSet the enabled status of the MooseObject.

Default:True

C++ Type:bool

Description:Set the enabled status of the MooseObject.

• use_displaced_meshFalseWhether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

Default:False

C++ Type:bool

Description:Whether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

• control_tagsAdds user-defined labels for accessing object parameters via control logic.

C++ Type:std::vector

Description:Adds user-defined labels for accessing object parameters via control logic.

• seed0The seed for the master random number generator

Default:0

C++ Type:unsigned int

Description:The seed for the master random number generator

• implicitTrueDetermines whether this object is calculated using an implicit or explicit form

Default:True

C++ Type:bool

Description:Determines whether this object is calculated using an implicit or explicit form

• constant_onNONEWhen ELEMENT, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps.When SUBDOMAIN, MOOSE will only call computeSubdomainProperties() for the 0th quadrature point, and then copy that value to the other qps. Evaluations on element qps will be skipped

Default:NONE

C++ Type:MooseEnum

Description:When ELEMENT, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps.When SUBDOMAIN, MOOSE will only call computeSubdomainProperties() for the 0th quadrature point, and then copy that value to the other qps. Evaluations on element qps will be skipped

• output_propertiesList of material properties, from this material, to output (outputs must also be defined to an output type)

C++ Type:std::vector

Description:List of material properties, from this material, to output (outputs must also be defined to an output type)

• outputsnone Vector of output names were you would like to restrict the output of variables(s) associated with this object

Default:none

C++ Type:std::vector

Description:Vector of output names were you would like to restrict the output of variables(s) associated with this object