Dry Cask Storage Systems (DCSS) Heat Flux BC

Applies a boundary condition that models fuel rod in a dry cask storage system. The rod is assumed to be the center rod in an assembly of identical rods so that the peak cladding temperature is reached. This uses the Manteufel and Trodreas correlations inside the assembly and models the assembly-to-ambient flux using a single parameter.

Description

Lifecycle analyses for Zircaloy-clad fuel rods includes estimation of cladding integrity during dry storage and transport in storage casks. Decay heat from radioactive nuclides increases the rod internal pressure and hoop stress and causes the cladding to reach temperatures up to 400C. These conditions can lead to precipitation of zirconium hydride in radial orientations, reducing the ductility of the cladding. DryCaskHeatFlux calculates the worst-case heat flux and peak clad temperatures.

Predicting the heat loss from a rod located inside an assembly which is packaged with many other assemblies inside of a single dry storage cask is difficult for several reasons. The emissivities and axial power profiles of the fuel rods have large uncertainties. In addition, the spatial distribution of power from the multiple rod assemblies is often unknown ahead of loading. The composition of the fill gas in the cask can also be difficult to predict.

These considerations lead to simplified calculations to predict worst-case heating and peak clad temperatures using homogenized models of the interior of the assembly (Manteufel and Todreas, 1994). The calculation includes terms for heat flux from the (homogenized) interior of the assembly to the edge of the rod bundle, from the edge of the rod bundle to the wall of the assembly, and from a single assembly to the exterior of the cask: (1) where heat flux, lumped heat conductivities, temperature at middle of assembly (hottest rod), temperature at edge of rod bundle, temperature at of assembly wall, and temperature outside cask (ambient). Manteufel and Todreas (1994) tabulate values of for common geometries for PWR and BWR fuel assemblies using He and N fill gases. depends on the cask type and loading and is specified by the user in Bison.

Example Input Syntax


variable = temperature
boundary = right
bwr_or_pwr = 'pwr'
fill_gas = 'nitrogen'
ambient_temperature = 298
cask_effective_htc = 6.857 # W/K per assembly, from: 1200 W/assembly, 298 K ambient, 200 C wall
start_time = 0
drying_duration = 0 # no drying
[../]

Input Parameters

• variableThe name of the variable that this boundary condition applies to

C++ Type:NonlinearVariableName

Description:The name of the variable that this boundary condition applies to

• fill_gasFill gas in cask after drying process.

C++ Type:MooseEnum

Description:Fill gas in cask after drying process.

• 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

• bwr_or_pwrCask assembly type: BWR or PWR

C++ Type:MooseEnum

Description:Cask assembly type: BWR or PWR

• cask_effective_htcEffective heat transfer coefficient from assembly to ambient [W/K]

C++ Type:double

Description:Effective heat transfer coefficient from assembly to ambient [W/K]

Required Parameters

• start_time0Time to begin the drying process

Default:0

C++ Type:double

Description:Time to begin the drying process

• ambient_temperature298Temperature outside of cask [K]

Default:298

C++ Type:double

• drying_duration0Duration of the drying process before storage

Default:0

C++ Type:double

Description:Duration of the drying process before storage

Optional Parameters

• enableTrueSet the enabled status of the MooseObject.

Default:True

C++ Type:bool

Description:Set the enabled status of the MooseObject.

• save_inThe name of auxiliary variables to save this BC's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

C++ Type:std::vector

Description:The name of auxiliary variables to save this BC's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

• 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

• diag_save_inThe name of auxiliary variables to save this BC's diagonal jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

C++ Type:std::vector

Description:The name of auxiliary variables to save this BC's diagonal jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

• 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

• vector_tagsnontimeThe tag for the vectors this Kernel should fill

Default:nontime

C++ Type:MultiMooseEnum

Description:The tag for the vectors this Kernel should fill

• extra_vector_tagsThe extra tags for the vectors this Kernel should fill

C++ Type:std::vector

Description:The extra tags for the vectors this Kernel should fill

• matrix_tagssystemThe tag for the matrices this Kernel should fill

Default:system

C++ Type:MultiMooseEnum

Description:The tag for the matrices this Kernel should fill

• extra_matrix_tagsThe extra tags for the matrices this Kernel should fill

C++ Type:std::vector

Description:The extra tags for the matrices this Kernel should fill

References

1. Randall D Manteufel and Neil E Todreas. Effective thermal conductivity and edge conductance model for a spent-fuel assembly. Nuclear Technology, 105(3):421â€“440, 1994.[BibTeX]