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The majority of the work for fusion machines concerns design studies, analysis of material properties, and the study of accident progression during projected off-normal situations. In all cases, there is a strong requirement for valuable insight into the situation when only given a limited amount of supporting data.

In order to satisfy this requirement, the FSP employs several analysis computer codes. Each of these codes analyzes a particular physical phenomenon. There are five fusion safety computer codes listed in the table and briefly described below.

ATHENA

The following are an overview of the ATHENA computer code:

• ATHENA/MOD1 is a multi-fluid version of the RELAP5 code (ammonia, helium, hydrogen, lithium, sodium, nitrogen, and water).
• RELAP5 was developed to analyze fluid flow and heat transfer in the core and cooling system of Light Water Reactors.
• Special engineering models are available for abrupt area changes, flow choking, pipe junctions, steam separators, pumps, valves, tees, turbines, and accumulators.
• Transient two-phase, non-equilibrium conservation equations for vapor and liquid mass, momentum and energy are solved by ATHENA for fluid flow.
• Transient conduction equations are included for structure temperatures.
• A full range of surface heat transfer correlations are included in ATHENA such as laminar and turbulent convection, boiling, and condensation.
• The ATHENA/RELAP5 code package has been exhaustively assessed and extensively applied by numerous companies, utilities, reactor vendors and regulatory agencies.

CHEMCON

The following are an overview of the CHEMCON computer code:

• CHEMCON simulates long term temperature transients in fusion reactor first wall, blanket, and shield structures resulting from decay heating.
• CHEMCON is a one-dimensional conduction model in cylindrical geometry that contains material properties for eleven solid materials and two gases.
• Chemical reactions of beryllium, carbon, and tungsten with steam and air are modeled in CHEMCON.
• Special convection, conduction and radiation models are included for heat transfer in voided and partially voided regions that contain gases, and for cryogenic thermal shields.

DSTAR

The following are an overview of the DSTAR computer code:

• Plasma disruptions rapidly release the plasma magnetic and thermal energy, creating significant protective tile erosion, induced structural forces, and high loop voltages that can generate high energy runaway electrons.
• DSTAR is a code that predicts the consequences of plasma disruptions to the structural components of tokamak.
• DSTAR is based on the Tokamak Simulation Code (a tokamak free-boundary plasma physics code developed by the Princeton Plasma Physics Laboratory) that predicts plasma motion and structural eddy currents.
• DSTAR has physics models for wall ablation, impurity transport, impurity emitted radiation, and runaway electron generation, transport and deposition.

MELCOR

The following are an overview of the MELCOR computer code:

• MELCOR models the progression of severe accidents in Light Water Reactor nuclear power plants (Figure 1) and is being developed by Sandia National Laboratories for the U. S. Nuclear Regulatory Commission.
  

  Figrue 1. Features of MELCOR model.
• MELCOR solves non-equilibrium conservation equations for mass, momentum, and energy of a liquid pool and vapor atmosphere (non-condensible gases can be included in the atmosphere).
• Fluid flow includes frictional/momentum form losses and flow choking for an ideal compressible gas, subcooled water, or saturated two-phase water.
• MELCOR has models for: pressure suppression pools, ice condensers, containment sprays, fan coolers, heat exchangers, valves, and hydrogen and carbon monoxide combustion.
• MELCOR solves one-dimensional conduction equations for temperatures in structures.
• MELCOR's heat transfer package considers: single-phase convection (forced or natural, internal or external flow), pool boiling, thermal radiation, and condensation.
• MELCOR's aerosol transport module treats aerosol nucleation and agglomeration, vapor condensation, gravity settling, diffusio-phoresis, thermophoresis, and gaseous/liquid transport.
• MELCOR verification and validation has been an extensive and ongoing effort by the NRC, SNL and other US national laboratories.
• INEEL modifications to MELCOR include the extension of water properties below its triple point temperature for LOCAs into cryostats, chemical oxidation reactions of steam with Be, C, and W, cryogenic helium or air as the primary fluid, HTO transport, convective boiling.
  

  Figrue 2. MELCOR application to ITER.

MSCAP

The following are an overview of the MSCAP computer code:

• The Magnetic System Circuitry Analysis Program (MSCAP) was developed to predict the voltages, currents, and energy dumps associated with magnet shorts, arcs, quenches, and emergency dump transients.
• MSCAP allows for the specification of time, voltage, and current dependent resistors, capacitors, inductors, and the self-mutual inductance characteristics of internal arcs and shorts in a magnet coil.
• The flexibility of MSCAP allows the user to develop very sophisticated models of the electrical and control networks of a magnet system.
• MSCAP provides circuit analysis for the MAGS code developed at Forschungszentrum Karlsruhe, Germany and used for the analysis of the ITER magnet system.
• Rapidly cooled.
• Transported to a thermal desorption analysis station.
• Subjected to programmed thermal transients.

TMAP4

The Tritium Migration Analysis Program (TMAP4) code was developed, verified, and validated at the INEEL. It is unique in its ability to simultaneously model:

• Chemical reactions,
• Convective flows,
• Diffusion,
• Heat transfer,
• Implantation,
• Trapping,
• Recombination,
• Multiple structures and species.,
• It is highly suitable for safety analyses involving tritium movement in fusion facilities and was adopted for use in the ITER project.