8. Block Parameters

This document lists all of the Block Parameters that are provided by the ARMI Framework. See armi.reactor.parameters for use.

Block Parameters from Framework

Name	Description	Units
orientation	Triple representing rotations counterclockwise around each spatial axis. For example, a hex assembly rotated by 1/6th has orientation (0,0,60.0)	degrees
pinLocation	Location of fuel pins
detailedNDens	High-fidelity number density vector with up to thousands of nuclides. Used in high-fi depletion runs where low-fi depletion may also be occurring. This param keeps the hi-fi and low-fi depletion values from interfering. See core.p.detailedNucKeys for keys.	atoms/(bn*cm)
burnupMWdPerKg	Burnup in MWd/kg of initial heavy metal	MWd/kg
fissileFraction	Ratio of fissile mass to heavy metal mass at block-level
molesHmBOLByPin	Total number of atoms of heavy metal at BOL	mole
newDPA	Dose in DPA accrued during the current time step	dpa
percentBu	Percentage of the initial heavy metal atoms that have been fissioned	%FIMA
percentBuByPin	Percent burnup of the initial heavy metal atoms that have been fissioned for each pin	%FIMA
percentBuMax	Maximum percentage in a single pin of the initial heavy metal atoms that have been fissioned	%FIMA
percentBuMaxPinLocation	Peak burnup pin location (integer)
residence	Duration that a block has been in the core multiplied by the fraction of full power generated in that time.	days
molesHmNow	Total number of atoms of heavy metal	mole
molesHmBOL	Total number of atoms of heavy metal at BOL.	mole
massHmBOL	Mass of heavy metal at BOL	g
initialB10ComponentVol	cc’s of un-irradiated, cold B10 containing component (includes full volume of any components with B10)	cm^3
depletionMatrix	Full BurnMatrix objects containing transmutation and decay info about this block.
cycleAverageBurnMatrix	Integrated burn matrix mapping this block from its BOC to EOC number densities.
envGroup	The environment group letter of this block
envGroupNum	An integer representation of the environment group (burnup/temperature/etc.). linked to envGroup.
buRate	Current rate of burnup accumulation. Useful for estimating times when burnup limits may be exceeded.	%FIMA/days
buRatePeak	Current rate of burnup accumulation at peak location	%FIMA/days
detailedDpa	displacements per atom	dpa
detailedDpaPeak	displacements per atom with peaking factor	dpa
detailedDpaRate	Current time derivative of average detailed DPA	dpa/s
displacementX	Assembly displacement in the x direction	m
displacementY	Assembly displacement in the y direction	m
heliumInB4C	Alpha particle production rate in B4C control and shield material.	He/s/cm^3
powerRx	Power density of the reactor	W/cm^3
timeToLimit	Time unit block violates its burnup limit.	days
zbottom	Axial position of the bottom of this block	cm
ztop	Axial position of the top of this block	cm
nHMAtBOL	Ndens of heavy metal at BOL	atoms/(bn*cm)
z	Center axial dimension of this block	cm
axialExpTargetComponent	The name of the target component used for axial expansion and contraction of solid components.
topIndex	(‘the axial block index within its parent assembly (0 is bottom block). This index withregard to the mesh of the reference assembly so it does not increase by 1 for each block.It is used to keep the mesh of the assemblies uniform with axial expansion.See setBlockMesh, makeAxialSnapList’,)
eqRegion	Equilibrium shuffling region. Corresponds to how many full cycles fuel here has gone through.
eqCascade	Cascade number in repetitive equilibrium shuffling fuel management.
id	Inner diameter of the Block.
height	the block height	cm
xsType	The xs group letter of this block
xsTypeNum	An integer representation of the cross section type, linked to xsType.
type	string name of the input block
rxFuelDensityCoeffPerMass	Fuel density coefficient	Δk/k/k’/kg
rxFuelTemperatureCoeffPerMass	Fuel temperature coefficient	Δk/k/k’/kg
rxFuelVoidedTemperatureCoeffPerMass	Fuel voided-coolant temperature coefficient	Δk/k/k’/kg
rxCladDensityCoeffPerMass	Clad density coefficient	Δk/k/k’/kg
rxCladTemperatureCoeffPerMass	Clad temperature coefficient	Δk/k/k’/kg
rxStructureDensityCoeffPerMass	Structure density coefficient	Δk/k/k’/kg
rxStructureTemperatureCoeffPerMass	Structure temperature coefficient	Δk/k/k’/kg
rxCoolantDensityCoeffPerMass	Coolant density coefficient	Δk/k/k’/kg
rxCoolantTemperatureCoeffPerMass	Coolant temperature coefficient	Δk/k/k’/kg
rxFuelDensityCoeffPerTemp	Fuel density coefficient	Δk/k/k’/K
rxFuelDopplerCoeffPerTemp	Fuel Doppler coefficient	Δk/k/k’/K
rxFuelVoidedDopplerCoeffPerTemp	Fuel voided-coolant Doppler coefficient	Δk/k/k’/K
rxFuelDopplerConstant	Fuel Doppler constant	Δk/k/k’*K^(n-1)
rxFuelVoidedDopplerConstant	Fuel voided-coolant Doppler constant	Δk/k/k’*K^(n-1)
rxStructureDopplerConstant	Structure Doppler constant	Δk/k/k’*K^(n-1)
rxCladDopplerConstant	Clad Doppler constant	Δk/k/k’*K^(n-1)
rxFuelTemperatureCoeffPerTemp	Fuel temperature coefficient	Δk/k/k’/K
rxFuelVoidedTemperatureCoeffPerTemp	Fuel voided-coolant temperature coefficient	Δk/k/k’/K
rxCladDensityCoeffPerTemp	Clad density coefficient	Δk/k/k’/K
rxCladDopplerCoeffPerTemp	Clad Doppler coefficient	Δk/k/k’/K
rxCladTemperatureCoeffPerTemp	Clad temperature coefficient	Δk/k/k’/K
rxStructureDensityCoeffPerTemp	Structure density coefficient	Δk/k/k’/K
rxStructureDopplerCoeffPerTemp	Structure Doppler coefficient	Δk/k/k’/K
rxStructureTemperatureCoeffPerTemp	Structure temperature coefficient	Δk/k/k’/K
rxCoolantDensityCoeffPerTemp	Coolant density coefficient	Δk/k/k’/K
rxCoolantTemperatureCoeffPerTemp	Coolant temperature coefficient	Δk/k/k’/K
avgFuelTemp	Average fuel temperature.	°C
assemNum	Index that refers, nominally, to the assemNum parameter of the containing Assembly object. This is stored on the Block to aid in visualizing shuffle patterns and the like, and should not be used within the code. These are not guaranteed to be consistent with the containing Assembly, so they should not be used as a reliable means to reconstruct the model.
axExtenNodeHeight	Axial extension node height	m
blockBeta	Beta in each block
blockF	Adjoint-weighted fission source in each block	1/cm^5/s^2
breedRatio	Breeding ratio
fissileDestroyed	Fissile atoms destroyed in last depletion step (not net!)	atoms/(bn*cm)
fissileBefore	Fissile atoms at beginning of last depletion step (could be substep!)	atoms/(bn*cm)
fissileAfter	Fissile atoms at end of last depletion step (could be substep!)	atoms/(bn*cm)
buLimit	Burnup limit	%FIMA
cladACCI	The amount of cladding wastage due to absorber chemical clad interaction	µm
convRatio	Conversion ratio
crWastage	Combines ACCI and clad corrosion for control blocks	µm
cyclicNErr	Relative error of the block number density
heightBOL	As-fabricated height of this block (as input). Used in fuel performance. Should be constant.	cm
intrinsicSource	Intrinsic neutron source from spontaneous fissions before a decay period
intrinsicSourceDecayed	Intrinsic source from spontaneous fissions after a decay period
kgFis	Mass of fissile material in block	kg
kgHM	Mass of heavy metal in block	kg
mchan	SASSYS/DIF3D-K (external) channel index assignment
mreg	SASSYS/DIF3D-K radial region index assignment
nPins	Number of pins
newDPAPeak	The peak DPA accumulated in the last burn step	dpa
percentBuPeak	Peak percentage of the initial heavy metal atoms that have been fissioned	%FIMA
powerShapeDelta	Change in power shape when core temperature rises.	W
puFrac	Current Pu number density relative to HM at BOL
smearDensity	Smear density of fuel pins in this block. Defined as the ratio of fuel area to total space inside cladding.

Block Parameters from FuelPerformancePlugin

Name	Description	Units
fuelCladLocked	Boolean to indicate if the fuel is locked with the clad. This is used to determine the expansion constraints for the fuel during thermal and/or burn-up expansion of the fuel and cladding materials.
gasReleaseFraction	Fraction of generated fission gas that no longer exists in the block.
bondRemoved	Fraction of thermal bond between fuel and clad that has been pushed out.
cladWastage	Total cladding wastage from inner and outer surfaces.	µm
totalCladStrain	Total diametral clad strain.	%
axialGrowthPct	Axial growth percentage	%
fpPeakFuelTemp	Fuel performance calculated peak fuel temperature.	°C
fpAveFuelTemp	Fuel performance calculated average fuel temperature.	°C
gasPorosity	Fraction of fuel volume that is occupied by gas pores
liquidPorosity	Fraction of fuel volume that is occupied by liquid filled pores

Block Parameters from NeutronicsPlugin

Name	Description	Units
axMesh	number of neutronics axial mesh points in this block
mgFlux	multigroup volume-integrated flux	n*cm/s
adjMgFlux	multigroup adjoint neutron flux	n*cm/s
lastMgFlux	multigroup volume-integrated flux used for averaging the latest and previous depletion step	n*cm/s
mgFluxGamma	multigroup gamma flux	#*cm/s
mgNeutronVelocity	multigroup neutron velocity	cm/s
extSrc	multigroup external source	#/cm^3/s
mgGammaSrc	multigroup gamma source	#/cm^3/s
gammaSrc	gamma source	#/cm^3/s
mgFluxSK	multigroup volume-integrated flux stored for multiple time steps in spatial kinetics (2-D array)	n*cm/s
pinMgFluxes	The block-level pin multigroup fluxes. pinMgFluxes[i, g] represents the flux in group g for pin i. Flux units are the standard n/cm^2/s. The “ARMI pin ordering” is used, which is counter-clockwise from 3 o’clock.	n/cm^2/s
pinMgFluxesAdj	should be a blank 3-D array, but re-defined later (nPins x ng x nAxialSegments)
pinMgFluxesGamma	should be a blank 3-D array, but re-defined later (nPins x ng x nAxialSegments)	#/cm^2/s
axialPowerProfile	For each reconstructed axial location, a tuple (z,power density) where with axial origin at the bottom of assembly in which the blocks are located.	W/cm^3
axialPowerProfileNeutron	For each reconstructed axial location, a tuple (z, neutron power density) where with axial origin at the bottom of assembly in which the blocks are located.	W/cm^3
axialPowerProfileGamma	For each reconstructed axial location, a tuple (z, gamma power density) where with axial origin at the bottom of assembly in which the blocks are located.	W/cm^3
betad	Delayed neutron beta
chi	Energy distribution of fission neutrons
chid	Energy distribution of delayed fission neutrons
linPow	Pin-averaged linear heat rate, which is calculated by evaluating the block power and dividing by the number of pins. If gamma transport is enabled, then this represents the combined neutron and gamma heating. If gamma transport is disabled then this represents the energy generation in the pin, where gammas are assumed to deposit their energy locally. Note that this value does not implicitly account for axial and radial peaking factors within the block. Use linPowByPin for obtaining the pin linear heat rate with peaking factors included.	W/m
linPowByPin	Pin linear linear heat rate, which is calculated through flux reconstruction and accounts for axial and radial peaking factors. This differs from the linPow parameter, which assumes no axial and radial peaking in the block as this information is unavailable without detailed flux reconstruction. The same application of neutron and gamma heating results applies.	W/cm
linPowByPinNeutron	Pin linear neutron heat rate. This is the neutron heating component of linPowByPin	W/cm
linPowByPinGamma	Pin linear gamma heat rate. This is the gamma heating component of linPowByPin	W/cm
reactionRates	List of reaction rates in specified by setting “reactionsToDB”	#/s
pointsEdgeFastFluxFr	Fraction of flux above 100keV at edges of the block
pointsEdgeDpa	displacements per atom at edges of the block	dpa
pointsEdgeDpaRate	Current time derivative of the displacement per atoms at edges of the block	dpa/s
cornerFastFlux	Neutron flux above 100keV at hexagon block corners	n/cm^2/s
pointsCornerFastFluxFr	Fraction of flux above 100keV at corners of the block
pointsCornerDpa	displacements per atom at corners of the block	dpa
pointsCornerDpaRate	Current time derivative of the displacement per atoms at corners of the block	dpa/s
rateBalance	Numerical balance between particle production and destruction (should be small)	1/cm^3/s
rateExtSrc	Rate of production of neutrons from an external source.	1/cm^3/s
rateFisAbs	Neutron abs. rate in fissile material	1/cm^3/s
rateFisSrc	Fission source rate. This is related to production rate in fissile by a factor of keff	1/cm^3/s
rateLeak	Rate that neutrons leak out of this block.	1/cm^3/s
rateParasAbs	Rate of parasitic absorption (absorption in non-fertile/fissionable material)	1/cm^3/s
rateProdNet	Net production rate of neutrons	1/cm^3/s
rateScatIn	Rate neutrons in-scatter in this block	1/cm^3/s
rateScatOut	Rate that neutrons out-scatter in this block (removal - absorption)	1/cm^3/s
capturePowerFrac	Fraction of the power produced through capture in a block.
fastFluence	Fast spectrum fluence	#/cm^2
fastFluencePeak	Fast spectrum fluence with a peaking factor	#/cm^2
fluence	Fluence	#/cm^2
flux	neutron flux	n/cm^2/s
fluxAdj	Adjoint flux
fluxAdjPeak	Adjoint flux
pdens	Average volumetric power density	W/cm^3
pdensDecay	Decay power density from decaying radionuclides	W/cm^3
arealPd	Power divided by XY area	MW/m^2
fertileBonus	The fertile bonus
fisDens	Fission density in a pin (scaled up from homogeneous)	fissions/cm^3/s
fisDensHom	Homogenized fissile density	1/cm^3/s
fluxGamma	Gamma scalar flux	#/cm^2/s
fluxPeak	Peak neutron flux calculated within the mesh	n/cm^2/s
kInf	Neutron production rate in this block/neutron absorption rate in this block. Not truly kinf but a reasonable approximation of reactivity.
medAbsE	Median neutron absorption energy	eV
medFisE	Median energy of neutron causing fission	eV
medFlxE	Median neutron flux energy	eV
pdensGamma	Average volumetric gamma power density	W/cm^3
pdensNeutron	Average volumetric neutron power density	W/cm^3
ppdens	Peak power density	W/cm^3
ppdensGamma	Peak gamma density	W/cm^3
rateAbs	Total absorption rate in this block (fisson + capture).	1/cm^3/s
rateCap	Parasitic capture rate in this block.	1/cm^3/s
rateProdN2n	Production rate of neutrons from n2n reactions.	1/cm^3/s
rateFis	Fission rate in this block.	1/cm^3/s
rateProdFis	Production rate of neutrons from fission reactions (nu * fission source / k-eff)	1/cm^3/s
powerGenerated	Generated power. Different than b.p.power only when gamma transport is activated.	W
power	Total power	W
powerGamma	Total gamma power	W
powerNeutron	Total neutron power	W
detailedDpaThisCycle	Displacement per atom accumulated during this cycle. This accumulates over a cycle and resets to zero at BOC.	dpa
detailedDpaPeakRate	Peak DPA rate based on detailedDpaPeak	dpa/s
dpaPeakFromFluence	DPA approximation based on a fluence conversion factor set in the dpaPerFluence setting	dpa
enrichmentBOL	Enrichment during fabrication (mass fraction)
fastFlux	Neutron flux above 100keV	1/cm^2/s
fastFluxFr	Fraction of flux above 100keV
pdensGenerated	Volume-averaged generated power density. Different than b.p.pdens only when gamma transport is activated.	W/cm^3

Block Parameters from ThermalHydraulicsPlugin

Name	Description	Units
pressureLossCoeffs	Pressure loss coefficients from form losses outside of bundle region of assembly, e.g. losses through pin attachment hardware, expansion in inlet nozzle.
THhotChannelCladMidwallT	Midwall (average) clad temperature for the hot channel or hot pin.	°C
THhotChannelHeatTransferCoeff	Film heat transfer coefficient for hot channel in the assembly.	W/m^2/K
THhotChannelCladODT	Nominal clad outer diameter temperature of the hot pin	°C
THhotChannelCladIDT	Nominal clad inner diameter temperature of the hot pin	°C
THhotChannelFuelODT	Temperature of the fuel outer diameter	°C
THhotChannelFuelCenterlineT	Nominal hot channel fuel centerline temperature	°C
TH0SigmaCladODT	0-sigma clad outer diameter temperature of the hot pin	°C
TH2SigmaCladODT	2-sigma clad outer diameter temperature of the hot pin	°C
TH3SigmaCladODT	3-sigma clad outer diameter temperature of the hot pin	°C
TH0SigmaCladIDT	0-sigma clad inner diameter temperature of the hot pin	°C
TH2SigmaCladIDT	2-sigma clad inner diameter temperature of the hot pin	°C
TH3SigmaCladIDT	3-sigma clad inner diameter temperature of the hot pin	°C
THdilationPressure	Dilation pressure	Pa
THTfuelCL	Average temperature of the fuel centerline used for neutronic coupling	°C
THTfuelOD	Average temperature of the fuel outer diameter used for neutronic coupling	°C
THaverageCladODT	Block average of the outer clad temperature.	°C
THaverageCladIDT	Block average of the inner clad temperature	°C
THaverageCladTemp	The nominal average clad temperature in the block, which should be used for neutronic and TH feedback.	°C
THaverageGapTemp	The nominal average gap temperature in the block, which should be used for neutronic and TH feedback.	°C
THaverageDuctTemp	The nominal average duct temperature in the block, which should be used for neutronic and TH feedback.	°C
THcoolantAverageT	Flow-based average of the inlet and outlet coolant temperatures.	°C
THcoolantInletT	The nominal average bulk coolant inlet temperature into the block.	°C
THcoolantOutletT	Coolant temperature at the outlet of this block	°C
THcoolantStaticT	Volume-based average coolant temperature, recommended for neutronics	°C
THdeltaPTotal	Total pressure difference in a block	Pa
THhotChannelOutletT	Nominal hot channel outlet temperature	°C
THlocalDTout	Maximum delta-Ts for outlet temperatures of all assemblies	°C
THlocalDToutFuel	Maximum delta-Ts for outlet temperatures of fuel assemblies	°C
THmassFlowRate	Mass flow rate	kg/s
THorificeZone	A list of orificing zones corresponding to the assembly list
THcornTemp	Best estimate duct temperature [degC] for assembly corners	°C
THedgeTemp	Best estimate duct temperature for assembly edges	°C
THhotChannel	Hot channel (highest coolant dT) identifier