4. Parameters Report

This document lists all 263 Parameters in ARMI:

• 8 Reactor Parameters.

• 46 Core Parameters.

• 39 Assembly Parameters.

• 148 Block Parameters.

• 22 Component Parameters.

Users of the ARMI Framework are not required to use all of these parameters. And the system is easy to extend to add new Parameters for your use-cases. These are simply the default Parameters that come with ARMI. See armi.reactor.parameters for use.

4.1. Reactor Parameters

This is a list of all of the Reactor Parameters that are provided by the ARMI Framework.

Reactor Parameters from Framework

Name	Description	Units
cycle	Current cycle of the simulation (integer)
cycleLength	Length of the cycle, including outage time described by availabilityFactor	days
stepLength	Length of current step	days
availabilityFactor	Availability factor of the plant. This is the fraction of the time that the plant is operating.
capacityFactor	The fraction of power produced by the plant this cycle over the full-power, 100% uptime potential of the plant.
time	Time of reactor life from BOL to current time node	yr
timeNode	Integer timeNode
maxAssemNum	Max number of assemblies created so far in the Reactor (integer)

4.2. Core Parameters

This is a list of all of the Core Parameters that are provided by the ARMI Framework.

Core 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
maxAssemNum	Maximum assembly number
numMoves	numMoves
crMostValuablePrimaryRodLocation	Core assembly location for the most valuable primary control rod.
crMostValuableSecondaryRodLocation	Core assembly location for the most valuable secondary control rod.
crTransientOverpowerWorth	Reactivity worth introduced by removal of the highest worth primary control rod from the core, starting from its critical position	pcm
axialMesh	Global axial mesh of the reactor core from bottom to top.	cm
referenceBlockAxialMesh	The axial block boundaries that assemblies should conform to in a uniform mesh case.	cm
fissileMass	Fissile mass of the reactor	g
heavyMetalMass	Heavy Metal mass of the reactor	g
keffUnc	Uncontrolled k-effective for the reactor core (with control rods fully removed).
maxDPA	Maximum DPA based on pin-level max if it exists, block level max otherwise	dpa
maxGridDpa	Grid plate max dpa	dpa
maxProcessMemoryInMB	Maximum memory used by an ARMI process	MB
minProcessMemoryInMB	Minimum memory used by an ARMI process	MB
minutesSinceStart	Run time since the beginning of the calculation	min
peakGridDpaAt60Years	Grid plate peak dpa after 60 years irradiation	dpa
power	Thermal power of the reactor core. Corresponds to the nuclear power generated in the core.	W
powerDensity	BOL Power density of the reactor core, in units of Watts pergrams of Heavy Metal Mass. After the BOL, the power parameter will be set, and this will entirely overridden by that.	W/g
maxdetailedDpaPeak	Highest peak dpa of any block in the problem	dpa
maxFlux	Max neutron flux in the core	n/cm^2/s
maxDetailedDpaThisCycle	Max increase in dpa this cycle (only defined at EOC)	dpa
dpaFullWidthHalfMax	Full width at half max of the detailedDpa distribution	cm
elevationOfACLP3Cycles	minimum axial location of the ACLP for 3 cycles at peak dose	cm
elevationOfACLP7Cycles	minimum axial location of the ACLP for 7 cycles at peak dose	cm
maxpercentBu	Max percent burnup on any block in the problem	%FIMA
rxSwing	Reactivity swing	pcm
maxBuF	Maximum burnup seen in any feed assemblies	%
maxBuI	Maximum burnup seen in any igniter assemblies	%
keff	Global multiplication factor
peakKeff	Maximum keff in the simulation
fastFluxFrAvg	Fast flux fraction average
maxpdens	Maximum avg. volumetric power density of all blocks	W/cm^3
maxPD	Maximum areal power density of all assemblies	MW/m^2
jumpRing	Radial ring number where bred-up fuel assemblies shuffle jump from the low power to the high power region.
beta	Effective delayed neutron fraction
betaComponents	Group-wise delayed neutron fractions
betaDecayConstants	Group-wise precursor decay constants	1/s
rxFuelAxialExpansionCoeffPerTemp	Fuel Axial Expansion Coefficient	Δk/k/k’/K
rxGridPlateRadialExpansionCoeffPerTemp	Grid Plate Radial Expansion Coefficient	Δk/k/k’/K
cyclics	The integer number of cyclic mode equilibrium-cycle iterations that have occurred so far
axialExpansionPercent	Percent of axial growth of fuel blocks	%
coupledIteration	Pre-defined number of tightly coupled iterations.

Core Parameters from NeutronicsPlugin

Name	Description	Units
eigenvalues	All available lambda-eigenvalues of reactor.
kInf	k-infinity

4.3. Assembly Parameters

This is a list of all of the Assembly Parameters that are provided by the ARMI Framework.

Assembly 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
arealPd	Power in assembly divided by its XY cross-sectional area. Related to PCT.	MW/m^2
buLimit	buLimit
chargeBu	Max block-average burnup in this assembly when it most recently entered the core. If the assembly was discharged and then re-charged, this value will only reflect the most recent charge.	%FIMA
chargeCycle	Cycle number that this assembly most recently entered the core. If the assembly was discharged and then re-charged, this value will only reflect the most recent charge.
chargeFis	Fissile mass in assembly when it most recently entered the core. If the assembly was discharged and then re-charged, this value will only reflect the most recent charge.	kg
chargeTime	Time at which this assembly most recently entered the core. If the assembly was discharged and then re-charged, this value will only reflect the most recent charge.	yr
multiplicity	The number of physical assemblies that the associated object represents. This is typically 1, but may need to change when the assembly is moved between containers with different types of symmetry. For instance, if an assembly moves from a Core with 1/3rd symmetry into a spent-fuel pool with full symmetry, rather than splitting the assembly into 3, the multiplicity can be set to 3. For now, this is a bit of a hack to make fuel handling work; multiplicity in the 1/3 core should be 3 to begin with, in which case this parameter could be used as the primary means of handling symmetry and fractional domains throughout ARMI. We will probably roll that out once the dust settles on some of this SFP work. For now, the Core stores multiplicity as 1 always, since the powerMultiplier to adjust to full-core quantities.
daysSinceLastMove	daysSinceLastMove
kInf	kInf
maxDpaPeak	maxDpaPeak	dpa
maxPercentBu	maxPercentBu	%
numMoves	numMoves
timeToLimit	timeToLimit	days
guideTubeTopElevation	Elevation of the top of the guide tube relative to the bottom of the duct.	cm
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.	atoms/(bn*cm)
notes	A string with notes about the assembly, limited to 1000 characters. This parameter is not meant to store data. Needlessly storing large strings on this parameter for every assembly is potentially unwise from a memory perspective.
crCriticalFraction	The insertion fraction when the control rod assembly is in its critical configuration. Note that the default of -1.0 is a trigger for this value not being set yet.
crCurrentElevation	The current elevation of the bottom of the moveable section of a control rod assembly.	cm
crInsertedElevation	The elevation of the furthest-most insertion point of a control rod assembly. For a control rod assembly inserted from the top, this will be the lower tip of the bottom-most moveable section in the assembly when fully inserted.	cm
crRodLength	length of the control material within the control rod	cm
crWithdrawnElevation	The elevation of the tip of a control rod assembly when it is fully withdrawn. For a control rod assembly inserted from the top, this will be the lower tip of the bottom-most moveable section in the assembly when fully withdrawn.	cm
THdeltaPNoGrav	Total pressure difference minus gravity; it can be thought of as being ‘total pressure loss’	Pa
THdeltaPPump	Pumping pressure rise required to pump the given mass flow rate through the rod bundle	Pa
THdeltaPTotal	Total pressure difference across the assembly	Pa
THcoolantOutletT	The nominal average bulk coolant outlet temperature out of the block.	°C
THlocalDTout	Maximum delta-Ts for outlet temperatures of all assemblies	°C
THlocalDToutFuel	Maximum delta-Ts for outlet temperatures of fuel assemblies	°C
THorificeZone	orifice zone for assembly; should be location specific
THmassFlowRate	The nominal assembly flow rate	kg/s
type	The name of the assembly input on the blueprints input
ringPosHist	Ring and position history for this assembly written at BOC. Index 1 corresponds to position at BOC1.
nozzleType	nozzle type for assembly
THcoolantInletT	Assembly inlet temperature in C (cold temperature)	°C
assemNum	Assembly number
dischargeTime	Time the Assembly was removed from the Reactor.	yr
hotChannelFactors	Definition of set of HCFs to be applied to assembly.
AziMesh	Number of points in the Azimuthal mesh.
RadMesh	Number of points in the Radial mesh.

4.4. Block Parameters

This is a list of all of the Block Parameters that are provided by the ARMI Framework.

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
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.	atoms/(bn*cm)
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
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
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 with regard 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.
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
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.
breedRatio	Breeding ratio
buLimit	Burnup limit	%FIMA
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
kgFis	Mass of fissile material in block	kg
kgHM	Mass of heavy metal in block	kg
nPins	Number of pins
percentBuPeak	Peak percentage of the initial heavy metal atoms that have been fissioned	%FIMA
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 ThermalHydraulicsPlugin

Name	Description	Units
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
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
THaverageCladTemp	The nominal average clad 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
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	Mid-wall duct temperature for assembly corners	°C
THedgeTemp	Mid-wall duct temperature for assembly edges	°C
THhotChannel	Hot channel (highest coolant dT) identifier

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
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
chi	Energy distribution of 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
rateProdNet	The total neutron production including (n,2n) source and fission source.	1/cm^3/s
capturePowerFrac	Fraction of the power produced through capture in a block.
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
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
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

4.5. Component Parameters

This is a list of all of the Component Parameters that are provided by the ARMI Framework.

Component Parameters from Framework

Name	Description	Units
volume	Volume of this object.	cm^3
area	Cross sectional area of this component.	cm^2
mult	The multiplicity of this component, i.e. how many of them there are.
mergeWith	Label of other component to merge with
type	The name of this object as input on the blueprints
temperatureInC	Component temperature in °C	°C
numberDensities	Number densities of each nuclide.	#/(bn*cm)
nuclides	Nuclide names corresponding to numberDensities array.
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.	atoms/(bn*cm)
pinNDens	Pin-wise number densities of each nuclide.	atoms/(bn*cm)
percentBu	Burnup as a percentage of initial (heavy) metal atoms.	%FIMA
pinPercentBu	Pin-wise burnup as a percentage of initial (heavy) metal atoms.	%FIMA
buRate	Current rate of burnup accumulation. Useful for estimating times when burnup limits may be exceeded.	%FIMA/days
enrichmentBOL	Enrichment during fabrication (mass fraction)
massHmBOL	Mass of heavy metal at BOL	g
customIsotopicsName	Label of isotopics applied to this component.
modArea	A (component, operation) tuple used to add/subtract area (in cm^2) from another components area. See c.getArea()
zrFrac	Original Zr frac of this, used for material properties.
pinNum	Pin number of this component in some mesh. Starts at 1.
theoreticalDensityFrac	Fractional value between zero and one, inclusive, for the theoretical density of the material stored on this component.
molesHmBOL	Total number of moles of heavy metal at BOL.	mole
pinIndices	Indices within data arrays where values for this component are stored. The array is zero indexed and structured such that the j-th pin on this component can be found at Block.getPinLocations()[pinIndices[j]].