================================================================================ Nomenclature ================================================================================ .. list-table:: :header-rows: 1 :align: center :widths: 1,3,1 * - Symbol - Definition - Units * - :math:`l` - Linear - * - n - Time step n - * - ' - Prime always indicates that a quantity refers to a unit of generalized smear volume - * - Subscripts - - * - ac - Acoustic - * - an - Annular - * - bb - Bubbly or bubble - * - bk - Lower boundary of node K - * - ca - Cavity - * - ch - Coolant channel - * - cl - Cladding - * - co - Condensation - * - deet - De-entrainment - * - drag - Drag - * - ej - Ejected or ejection - * - et - Entrained or entrainment - * - fc - Fuel/clad interface - * - ff - Frozen fuel - * - ffcl - Frozen fuel on cladding - * - ffsr - Frozen fuel on structure - * - fi - Free fission gas in coolant channel - * - fica - Free fission gas in molten pin cavity - * - ficaxx - Used for special fission gas volume fraction calculation (see :eq:`14.2-38a`) - * - fm - Film (stationary liquid sodium film or moving annular fuel film) - * - fr - Friction - * - friction - Friction - * - FR1 - Flow regime 1 - particulate fuel flow - * - FR3 - Flow regime 3 - partially or fully annular flow - * - FR4 - Flow regime 4 - bubbly fuel flow - * - fsca - Dissolved fission gas in the molten pin cavity - * - fs - Dissolved fission gas in the coolant channel - * - fu - Liquid and/or mobile solid fuel in the coolant channel - * - fuca - Mobile fuel in the molten pin cavity - * - fuch - Mobile fuel in the coolant channel (including fuel vapor) - * - fufi - Fuel and fission gas - * - fv - Fuel vapor in the coolant channel - * - fvca - Fuel vapor in the molten pin cavity - * - fz - Freezing, frozen - * - hoop - Hoop (stress) - * - Ht - Heat transfer - * - i - Axial coolant channel index, specific enthalpy - * - IB - Uppermost slug segment of lower sodium slug - * - if - Interface - * - in - Inner (middle) clad node or structural node facing neighboring hexan wall - * - inlet - Subassembly inlet - * - IT - Lowermost slug segment of upper sodium slug - * - K - Axial pin or cavity index - * - k - Material component k; this can also be cladding or structure - * - l - Dummy index - * - liq - Liquidus - * - ls - Lower slug - * - m - m = 1 indicates upward flow, m = 2 downward flow - * - me - Melting, melt-in - * - mi - Mixture of sodium and fission gas - * - min - Minimum - * - mv - Moving - * - mx - Maximum - * - Na - Sodium - * - Nl - Liquid sodium - * - Nm - Moving sodium liquid and sodium vapor - * - node - Node - * - Nv - Sodium vapor - * - op - Open channel - channel volume or cross section remaining open after plateout has occurred - * - or - Orifice - * - os - Outer surface of clad or structure of fuel film or fuel crust. All these surfaces are facing the coolant channel. - * - outlet - Subassembly outlet - * - p - Subscript of specific heat for constant pressure - * - Pa - Fuel particle - * - pin,pi - Pin - * - PL - PLUTO2 - * - power - Power - * - radial - Radial - * - rl - Dissolved fission-gas release - * - S' - Sink or source per unit of generalized smear volume - * - sol - Solidus - * - sonic - Sonic - * - sr - Structure - * - un - Uncompressed - * - us - Upper liquid sodium slug - * - UTS - Ultimate tensile strength - * - vg - Vapor and gas - * - vi - Viscous - * - x - Auxiliary subscript - * - z - Axial location z - * - zi - Designates bottom of a liquid sodium slug segment - * - **Greek Symbols** - **Definition** - **Units** * - :math:`\alpha` - Void fraction - * - :math:`\beta` - Delayed neutron fraction - * - :math:`\gamma` - C\ :sub:`p`/C\ :sub:`v` - * - :math:`\delta` - Partial derivative - * - :math:`\Delta` - Derivative in finite differences - * - :math:`\kappa` - Compressibility - * - :math:`\pi` - Circumference of a circle divided by its diameter - * - :math:`\rho` - Theoretical density - * - :math:`\rho'` - Generalize linear density - * - :math:`\sigma` - Surface tension - * - :math:`\theta` - Generalized volume fraction - * - **Regular Symbols** - **Description** - **Units** * - A - Cross section area - * - A' - Interaction or surface area per unit of generalized smear volume - * - AFR - Input, liquid sodium friction coefficient - * - AFRV - Input, sodium vapor friction coefficient - * - AHELP - Auxiliary quantity in momentum conservation - * - AMIIN - Auxiliary quantity in momentum conservation - * - ARCH - Cross section area of coolant channel per pin - * - ARCL - Cladding surface area per unit of generalized smear volume - * - AREA - Area - * - ARFF - Cross section area of plated-out fuel pin - * - ARMF - Cross section area of moving fuel per pin - * - ARSR - Structure surface area per unit of generalized smear volume - * - AXMX - Input, reference cross section area; recommended input value is subassembly cross section area - * - BFR - Input, exponent of liquid friction coefficient - * - BFRV - Input, exponent of vapor friction coefficient - * - BHELP - Auxiliary quantity in the momentum equation - * - BMIIN - Auxiliary quantity in the momentum equation - * - C - Specific heat - * - CDFU - Input, fuel conductivity - * - CDNL - Input, liquid sodium conductivity - * - CDVG - Input, conductivity of sodium vapor - * - CFCOFV - Input, fuel vapor condensation coefficient - * - CFFFCL - Fraction of channel perimeter covered by plated-out fuel - * - CFFRMF - Friction coefficient for annular fuel - * - CFFUCL - Fraction of cladding and structure covered by moving or plated-out fuel - * - CFMELT - Fraction of frozen fuel remelting per PLUTO2 time step - * - CFMFCL - Fraction of channel perimeter covered by moving fuel - * - CFMFFF - Fraction of plated-out fuel covered by moving fuel - * - CFNACL - Fraction of channel perimeter that is in contact with sodium - * - CFNACN - Input, sodium vapor condensation coefficient - J/(m\ :sup:`2`\ ·s·K) * - CFNAEV - Input, sodium evaporation coefficient - J/(m\ :sup:`2`\ ·s·K) * - CIANIN - Input, determines when a complete annular fuel flow begins - * - CIA1 - Input, constant in the fuel particle-to-sodium heat transfer - * - CIA2 - Input, constant in the fuel particle-to-sodium heat transfer - * - CIA3 - Input, constant in the Deissler heat-transfer correlation - * - CIA4 - Input, controls range of interpolation between boiling heat transfer coefficient and single-phase gas heat-transfer coefficient - * - CIA5 - Input, controls drag dependence in void fraction in the particulate flow regime - * - CIA6 - Input, controls drag in the bubbly flow regime - * - CIBBIN - Input, controlling onset of bubbly flow regime - * - CIETFU - Input, controls effect of fuel particles on sodium film entrainment - * - CIFRFU - Input, part of the fuel friction calculation - * - CIFUFZ - Input, controls mode of fuel freezing - * - CIFUMO - Input, controls axial fuel momentum low on ejection from pin - * - CINAFO - Input, initial and maximum sodium film fraction - * - CIREFU - Input, Reynolds number above which fully turbulent fuel flow is assumed for friction calculation - * - CIRTFS - Input, controls dissolved gas release - 1/s * - CIVOID - Input, controls liquid sodium fraction below which single-phase heat-transfer and friction laws are used - * - CMFU - Input, liquid fuel compressibility - 1/Pa * - CMNL - Input, liquid sodium compressibility - 1/Pa * - COFICH - Convective fission-gas mass flux in coolant channel - kg/(s·m\ :sup:`2`) * - COFUCH - Convective fuel mass flux in coolant channel - kg/(s·m\ :sup:`2`) * - COFUOS - Convective fuel energy flux in the channel - J/(s·m\ :sup:`2`) * - CONACH - Convective sodium mass flux in coolant channel - kg/(s·m\ :sup:`2`) * - CPFU - Input, fuel heat capacity - J/(s·m\ :sup:`2`) * - CTFRFU - Fraction of the moving fuel that is in contact with clad or plated-out fuel - * - C1 - Input, part of liquid sodium heat-transfer correlation - * - C2 - Input, part of liquid sodium heat-transfer correlation - * - C3 - Input, part of liquid sodium heat-transfer correlation - * - C1VIPR - Input, used for the artificial viscous pressure calculation in the pin - * - C2VIPR - Input, used for the artificial viscous pressure calculation in the pin - * - D - Diameter, hydraulic diameter - m * - DEFICH - Generalized smear density of free fission gas in the coolant channel - kg/m\ :sup:`3` * - DEFUCH - Generalized smear density of the moving fuel in the coolant channel - kg/m\ :sup:`3` * - DEFVCH - Generalized smear density of fuel vapor in the coolant channel - kg/m\ :sup:`3` * - DENACH - Generalized smear density of sodium in the coolant channel - kg/m\ :sup:`3` * - DENMCH - Generalized smear density of moving sodium in the coolant channel - kg/m\ :sup:`3` * - DZPLIN - Input, minimum length of a Lagrangian edge cell - m * - e - Internal energy - J/kg * - EGBBLY - Input, internal fuel energy below which fuel freezing begins - J/kg * - EGFULQ - Input, internal fuel energy at the solidus - J/kg * - EGFUSO - Input, internal fuel energy at the solidus - J/kg * - EGMN - Input, internal fuel energy below which fuel cannot switch from the particulate to a continuous flow regime - J/kg * - EPCH - Input, controls use of advanced pressure in in-pin calculation - * - f - Factor used in interphase drag term - * - F - Friction factor - * - FF - Mass of fuel ejected per time step and per unit of generalized smear volume - kg/m\ :sup:`2` * - FIFNGB - Input, fraction of fission gas on grain boundaries which becomes available as free gas upon fuel melting - * - FNARME - Input, cross section area of pin cavity/cross section area of fuel above which failure of this node is allowed to occur - * - FNFUAN - Input, controls when annular fuel flow in molten pin cavity is assumed - * - FNMECA - Fraction of node width of radial heat-transfer node on cavity boundaries which melts in pure PLUTO2 time step - * - FNMELT - Input, controls locus of cavity boundary - * - FNPI - Fraction of all the pins in a subassembly which have failed - * - FNPOHE - Relative power level - * - FN - Fraction of the molten fuel in a ejection cell which is ejected per PLUTO2 time step - * - FUELMS - Initial fuel mass in a radial fuel-pin mode - kg * - FUMASS - Initial total fuel mass in an axial fuel node - kg * - FUMS - Current fuel mass in the radial fuel pin node on the cavity boundary - kg * - F.R. 1 - Particulate fuel flow regime - * - F.R. 3 - Partially or fully annular flow regime - * - F.R. 4 - Bubbly fuel flow regime - * - g - Gravity - m/s\ :sup:`2` * - GAMSS - Input, fraction of power going into direct heating of structure - * - GAMTNC - Input, fraction of power going into direct heating of coolant - * - GAMTNE - Input, fraction of power going into direct heating of cladding - * - h - Heat-transfer coefficient - J/(m\ :sup:`2`\ ·s·K) * - H - Heat-transfer coefficient times heat-transfer area - J/(s·K) * - HCCLMI - Input, heat-transfer coefficient between hot cladding and a two-phase sodium/gas mixture - J/(m\ :sup:`2`\ ·s·K) * - HCFFMI - Input, heat-transfer coefficient between frozen fuel crust surface and two-phase sodium/gas mixture - J/(m\ :sup:`2`\ ·s·K) * - HCFUBB - Input, heat-transfer coefficient between the interior of the molten fuel and bubble surface - J/(m\ :sup:`2`\ ·s·K) * - h1 - Auxiliary heat-transfer coefficient - J/(m\ :sup:`2`\ ·s·K) * - h2 - Auxiliary heat-transfer coefficients - J/(m\ :sup:`2`\ ·s·K) * - I - Axial node index in coolant channel - * - IB - Channel zone in which the uppermost segment of the lower slug is located - * - IDIFF - Offset between pin and channel grid. The first pin node is at the same elevation as channel node IDIFF + 1 - * - IFLAG - Pointer array which gives the flow regime number for each axial channel node - * - IMAX - Uppermost slug segment of upper sodium slug - * - IT - Channel zone in which the lowermost segment of the upper slug is located - * - k - Conductivity - J/(m·s·K) * - K - Axial index in the pin - * - KKMX - Uppermost node in the molten pin cavity - * - KZPIN - Coolant channel zone which contains the fuel pins - * - KK1 - Lowermost node in the molten pin cavity - * - L - Length - m * - L1 - Length of the Lagrangian node at one end of the interaction region - m * - L2 - Length of Lagrangian node at the other end of the interaction region - m * - N' - Number per unit of generalized smear volume - * - NCPLEV - Input, number of cladding nodes which have to be molten in to lead to switch to LEVITATE - * - NGRDSP - Input, number of grid spacers in the channel zone containing fuel pins - * - NRPI - Number of pins per subassembly - * - NT - Number of radial fuel pin nodes - * - Nu - Nusselt number - * - P - Pressure - Pa * - PECH - Perimeter of the coolant channel associated with one pin - M * - PORFR - Porosity fraction - * - POW - Input, power in highest rated axial fuel pin node - W * - POWCOF - Exponent in the exponential function which give the power history during main time step - * - PRFAIL - Input, failure pressure for non-mechanistic clad failure Propagation - Pa * - Pr - Prandtl number - * - PSHAPE - Input, axial pin power shape - * - PSHAPR - Input, radial power shape in a pin - * - Q - Fission heat source - W/kg * - r - Radius - M * - R - Gas constant or radius - J/(kg·K) * - RAFPLA - Input, radius of large particles - m * - RAFPSM - Input, radius of small particles (which have been generated due to the decay of the larger particles after TIFP seconds) - kg * - RETFG2 - Retained fission-gas mass in the original radial fuel-pin node at the cavity boundary before it began melting into the cavity - * - Re - Reynold's number - * - RGAS - Input, gas constant for fission gas - J/(kg·K) * - RGNA - Sodium vapor gas constant which is a calculated quantity in PLUTO2 - J/(kg·K) * - S - Mass sink or source - kg/s * - S' - Mass sink or source per unit of generalized smear volume - kg/(s·m\ :sup:`3`) * - St - Stanton number - * - t - Time - s * - T - Temperature - K * - TECLMN - Input, cladding temperature above which frozen fuel will not stick to the cladding - K * - TECLRL - Input, cladding temperature above which the frozen fuel crust will be released - K * - TEFAIL - Input, cladding failure temperature in nonmechanistic failure criteria - K * - TESOL - Input, steel solidus temperature - K * - TIFP - Input, time delay for fragmentation of large particles into small ones - s * - TKFF - Thickness of frozen fuel crust - m * - u - Velocity - m/s * - UFCH - Fuel velocity in the channel - m/s * - UMCH - Sodium/gas mixture velocity in the channel - m/s * - VCONST - Auxiliary quantity in the sodium film entrainment calculation - * - VFNALQ - Input, liquid sodium fraction below which a particulate flow regime can become a continuous one - * - VFNARE - Input, liquid sodium fraction below which a particular flow regime can become a continuous one - * - VIFG - Input, viscosity of sodium vapor - kg/(m·s) * - VIFULQ - Input, viscosity of liquid sodium - kg/(m·s) * - VOLUME - Volume - m\ :sup:`3` * - w - Width - m * - W - Mass flow rate - kg/s * - x - Sodium quality - * - XKORGD - Input, orifice coefficient of a single grid spacer - * - XKORV - Input, expansion, contraction, or orifice coefficient - * - z - Axial coordinate - m