SPECTRA - Thermal-Hydraulic System Code
SPECTRA is a thermal-hydraulic system code. SPECTRA is designed for thermal-hydraulic analyses of nuclear power plants. The code main applicability is the area of Light Water Reactors, High Temperature Reactors, Liquid Metal Fast Reactors, Molten Salt Reactors, as well as conventional plants and chemical reactors. The code can be used for analyzing accident scenarios, including loss-of-coolant accidents (LOCAs), operational transients, and other accident scenarios in nuclear power plants. The code structure is based on Packages, which contain models on a given topic. The available models include multidimensional two-phase flow, non-equilibrium thermo-dynamics, transient heat conduction in solid structures, general heat and mass transfer package, with natural and forced convection, condensation, boiling.
In the past SPECTRA was used in South Africa at for independent verification of FLOWNEX analyses of PBMR and dust and fission product behavior during accidents. Currently it is used in China (INET) for safety analyses of HTR-PM and HTR-10. In Canada (Terrestrial Energy) it is being used for safety analyses of the Integral MSR.
SPECTRA is a thermal-hydraulic system code. SPECTRA is designed for thermal-hydraulic analyses of nuclear power plants. The code main applicability is the area of Light Water Reactors, High Temperature Reactors, Liquid Metal Fast Reactors, Molten Salt Reactors, as well as conventional plants and chemical reactors. The code can be used for analyzing accident scenarios, including loss-of-coolant accidents (LOCAs), operational transients, and other accident scenarios in nuclear power plants. The code structure (Fig. 1) is based on Packages, which contain models on a given topic. The available models include multidimensional two-phase flow, non-equilibrium thermo-dynamics, transient heat conduction in solid structures, general heat and mass transfer package, with natural and forced convection, condensation, boiling. Detailed description of the code is available.
Built-in fluids: Built-in fluid property tables consist of the properties of water, steam, and several non-condensable gases, all of them treated as real gases. The steam properties were obtained using the NRC/NBC steam tables program, covering the range from 270 K to 3070 K, and from virtually 0.0 Pa to 2.1E+7 Pa.
User-defined gases: Non-condensable gases can be added as user-defined gases, these are treated as perfect gases.
User-defined liquids: User-defined liquid properties can be applied as an alternative fluid. This can be used to liquid metal reactors, molten salt reactors, etc.
Heat conduction is calculated by the 1-D (Fig. 2) and 2-D Solid Heat Conductor (Fig. 3) Packages, using a general transient heat conduction equation. The heat transfer at the boundaries of the Solid Heat Conductors is obtained from the Heat and Mass Transfer Package, which provides models for natural and forced convection, condensation with and without non-condensable gases, boiling curve (Fig. 4), including nucleate boiling, critical heat flux (CHF), transition boiling, film boiling, heat transfer in two-phase flow, as well as non-equilibrium boiling and condensation (“flashing” and “fogging”). The heat and mass transfer models include correlations valid for wall-fluid, pool-atmosphere, atmosphere-droplets, and pool-bubbles interfaces.
A detailed thermal radiation model is provided, including grey enclosure models, with and without participating gas. The gas radiation model is based on the Hottel gas approach.
Point kinetics and nodal kinetics models are available, with reactivity feedbacks from control rods, fuel and moderator temperature, void fraction, as well as changes in isotope concentrations. The Isotope Transformation model allows computing core composition changes (due to fuel burn-up, production of poisons, such as Xe-135, fuel reload, etc.), and their effect on reactivity as well as decay heat production. For molten salt reactor applications, the reactor kinetics model has been extended to account for delayed neutron precursor drift, characteristic for molten salt reactors with circulating fuel. The model was validated based on MSRE data (Fig. 5)
The Radioactive Particle Transport Package deals with release of fission products, aerosol transport, deposition, and resuspension. Radioactive chains of fission products (Fig. 6) are tracked. The models for the transport and deposition of aerosols include Brownian diffusion, thermophoresis, and gravitational settling. For turbulent flow conditions, turbulent deposition models for the diffusional deposition, turbulent eddy impaction, and inertia impaction regime are included. Moreover, gravitational, Brownian, and turbulent coagulation are modeled.
Two state-of-the-art dynamic resuspension models are available. Alternatively, resuspension can be modeled using a parametric model with user-defined coefficients directly obtained from resuspension experiments. The following fission product models are included:
FP release models (CORSOR, CORSOR-M, user-defined functions)
Condensation of FP vapors
Sorption of FP on surfaces
Sorption of FP vapors on aerosol particles
A hydrogen burn model is available, which includes temperature-dependent flammability limits for slow deflagrations, fast turbulent deflagrations and detonations (Fig. 7) as well as ignition criteria.
An oxidation model is available, which consists of
- Built-in oxidation models
- Zr oxidation by steam, (Cathcart or Urbanic-Heidrich)
- Steel oxidation by steam, (White)
- Zr oxidation by O2, (Benjamin et al.)
- Graphite oxidation by O2, (Roes)
User-defined oxidation
A general oxidation equation with user-defined coefficients is available. Practically any oxidation reaction can modeled. Multiple reactions (e.g. simultaneous oxidation of Zr by steam and air) are possible. Recent additions:
- reactions occurring during water ingress into HTR were implemented and tested.
- A new correlation for air oxidation (Fig. 8) in spent fuel pools (SFP), including the effect of nitrogen, has been proposed, implemented and tested. The new model results were compared with the results of correlations available in MELCOR and ASTEC.
full list of validation based experiments
In the past SPECTRA was used in South Africa at for independent verification of FLOWNEX analyses of PBMR and dust and fission product behavior during accidents. Currently it is used in China (INET) for safety analyses of HTR-PM and HTR-10. In Canada (Terrestrial Energy) it is being used for safety analyses of the Integral MSR.
System code
SPECTRA is a thermal-hydraulic system code. SPECTRA is designed for thermal-hydraulic analyses of nuclear power plants. The code main applicability is the area of Light Water Reactors, High Temperature Reactors, Liquid Metal Fast Reactors, Molten Salt Reactors, as well as conventional plants and chemical reactors. The code can be used for analyzing accident scenarios, including loss-of-coolant accidents (LOCAs), operational transients, and other accident scenarios in nuclear power plants. The code structure (Fig. 1) is based on Packages, which contain models on a given topic. The available models include multidimensional two-phase flow, non-equilibrium thermo-dynamics, transient heat conduction in solid structures, general heat and mass transfer package, with natural and forced convection, condensation, boiling. Detailed description of the code is available.
Fluid Properties
Built-in fluids: Built-in fluid property tables consist of the properties of water, steam, and several non-condensable gases, all of them treated as real gases. The steam properties were obtained using the NRC/NBC steam tables program, covering the range from 270 K to 3070 K, and from virtually 0.0 Pa to 2.1E+7 Pa.
User-defined gases: Non-condensable gases can be added as user-defined gases, these are treated as perfect gases.
User-defined liquids: User-defined liquid properties can be applied as an alternative fluid. This can be used to liquid metal reactors, molten salt reactors, etc.
Basic Heat Transfer
Heat conduction is calculated by the 1-D (Fig. 2) and 2-D Solid Heat Conductor (Fig. 3) Packages, using a general transient heat conduction equation. The heat transfer at the boundaries of the Solid Heat Conductors is obtained from the Heat and Mass Transfer Package, which provides models for natural and forced convection, condensation with and without non-condensable gases, boiling curve (Fig. 4), including nucleate boiling, critical heat flux (CHF), transition boiling, film boiling, heat transfer in two-phase flow, as well as non-equilibrium boiling and condensation (“flashing” and “fogging”). The heat and mass transfer models include correlations valid for wall-fluid, pool-atmosphere, atmosphere-droplets, and pool-bubbles interfaces.
Thermal Radiation
A detailed thermal radiation model is provided, including grey enclosure models, with and without participating gas. The gas radiation model is based on the Hottel gas approach.
Reactor Kinetics
Point kinetics and nodal kinetics models are available, with reactivity feedbacks from control rods, fuel and moderator temperature, void fraction, as well as changes in isotope concentrations. The Isotope Transformation model allows computing core composition changes (due to fuel burn-up, production of poisons, such as Xe-135, fuel reload, etc.), and their effect on reactivity as well as decay heat production. For molten salt reactor applications, the reactor kinetics model has been extended to account for delayed neutron precursor drift, characteristic for molten salt reactors with circulating fuel. The model was validated based on MSRE data (Fig. 5)
Radioactive Particle Transport
The Radioactive Particle Transport Package deals with release of fission products, aerosol transport, deposition, and resuspension. Radioactive chains of fission products (Fig. 6) are tracked. The models for the transport and deposition of aerosols include Brownian diffusion, thermophoresis, and gravitational settling. For turbulent flow conditions, turbulent deposition models for the diffusional deposition, turbulent eddy impaction, and inertia impaction regime are included. Moreover, gravitational, Brownian, and turbulent coagulation are modeled.
Two state-of-the-art dynamic resuspension models are available. Alternatively, resuspension can be modeled using a parametric model with user-defined coefficients directly obtained from resuspension experiments. The following fission product models are included:
FP release models (CORSOR, CORSOR-M, user-defined functions)
Condensation of FP vapors
Sorption of FP on surfaces
Sorption of FP vapors on aerosol particles
Hydrogen Burn
A hydrogen burn model is available, which includes temperature-dependent flammability limits for slow deflagrations, fast turbulent deflagrations and detonations (Fig. 7) as well as ignition criteria.
Oxidation Models
An oxidation model is available, which consists of
- Built-in oxidation models
- Zr oxidation by steam, (Cathcart or Urbanic-Heidrich)
- Steel oxidation by steam, (White)
- Zr oxidation by O2, (Benjamin et al.)
- Graphite oxidation by O2, (Roes)
User-defined oxidation
A general oxidation equation with user-defined coefficients is available. Practically any oxidation reaction can modeled. Multiple reactions (e.g. simultaneous oxidation of Zr by steam and air) are possible. Recent additions:
- reactions occurring during water ingress into HTR were implemented and tested.
- A new correlation for air oxidation (Fig. 8) in spent fuel pools (SFP), including the effect of nitrogen, has been proposed, implemented and tested. The new model results were compared with the results of correlations available in MELCOR and ASTEC.
Validation Based on Experiments
Click here to download the SPECTRA LEAFLET FILE for full list of validation based experiments
Vol.1 Program Description (PDF)