Overview of PWR Thermal Hydraulics

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					  Overview of PWR Thermal Hydraulics

        NE 116



Professor Jose N. Reyes




                     Nuclear Engineering & Radiation Health Physics
                                            Oregon State University
Nuclear Steam Supply System
                                     The design of an
                                     NSSS depends on
                                     Thermal
                                     Hydraulics
                                     Analysis.




       Nuclear Engineering & Radiation Health Physics
                              Oregon State University
                  Thermal Phenomena
 Thermal Phenomena: Involves the transfer of heat due
  to a temperature difference.
    Convection Heat Transfer: The transfer of thermal energy from a
     surface via the motion of a fluid in direct contact with the
     surface.
    Conduction Heat Transfer: The transfer of thermal energy
     through a substance by molecular interactions. For solids, the
     primary mechanism is relative lattice vibrations.
    Radiation Heat Transfer: The transfer of thermal energy in the
     form of electromagnetic waves emitted at the surface of the heat
     source.



                        Nuclear Engineering & Radiation Health Physics
                                               Oregon State University
                Hydraulic Phenomena
 Involves fluid flow (gases, liquids or mixtures of liquids
  and gases). Requires models for flow regimes (laminar
  and turbulent), flow patterns, and pressure drop.




                      Nuclear Engineering & Radiation Health Physics
                                             Oregon State University
         Thermal-Hydraulic Phenomena
 Many hydraulic phenomena, such as turbulence, can
  have a significant impact on heat transfer. Therefore
  thermal hydraulics is the study of the coupled effects of
  heat transfer in fluid environments.
 Neutronic Analyses are also coupled to reactor thermal-
  hydraulics. Moderator temperature and boiling will
  affect neutron slowing down and thus the fission rate.




                     Nuclear Engineering & Radiation Health Physics
                                            Oregon State University
Reactor Vessel
         Convection Heat
         Transfer from the fuel
         rods to the surrounding
         fluid.

         Conduction Heat
         Transfer through the
         steel vessel walls.




 Nuclear Engineering & Radiation Health Physics
                        Oregon State University
PWR Fuel




Nuclear Engineering & Radiation Health Physics
                       Oregon State University
Steam Generator
                Convection heat transfer from
                the fluid inside the tubes to
                the steel tube walls.

                Conduction heat transfer
                through the steel tube walls.

                Convection heat transfer from
                the steel tube walls to the
                fluid outside the tubes.




 Nuclear Engineering & Radiation Health Physics
                        Oregon State University
Steam Generator




 Nuclear Engineering & Radiation Health Physics
                        Oregon State University
Reactor Coolant Pump
                   Convection heat transfer
                   is used to cool the
                   reactor coolant pumps.

                   6000 hp reactor coolant
                   pumps are used to raise
                   primary loop fluid
                   temperature to near
                   operating conditions
                   during plant start-up.


    Nuclear Engineering & Radiation Health Physics
                           Oregon State University
 Pressurizer
               Convection heat transfer
               is used to produce the
               steam bubble in the
               pressurizer to raise
               system pressure.

               Convection heat transfer
               is used to condense the
               steam bubble to reduce
               system pressure.


Nuclear Engineering & Radiation Health Physics
                       Oregon State University
Spent Fuel Element
                  Natural Convection is
                  used to remove decay
                  heat from spent fuel
                  assemblies.




   Nuclear Engineering & Radiation Health Physics
                          Oregon State University
Reactor Containment Building
                       Containment Design relies on
                       calculating the peak
                       containment pressure during
                       potential accidents.

                       The distribution of steam,
                       hydrogen and fission product
                       gases inside containment
                       must be calculated for severe
                       accidents.




        Nuclear Engineering & Radiation Health Physics
                               Oregon State University
Containment Building




    Nuclear Engineering & Radiation Health Physics
                           Oregon State University
Containment Spray Nozzles
                     Determining the size of
                     the containment spray
                     requires calculating
                     peak containment
                     pressures and spray
                     condensation rates.




      Nuclear Engineering & Radiation Health Physics
                             Oregon State University
High Pressure & Low Pressure Turbines
                           Designing the high pressure
                           and low pressure turbines
                           relies on calculations of
                           steam pressures and
                           temperatures.

                           Designing the moisture
                           separator reheaters for the
                           low pressure turbines
                           depends on T/H calculations.




            Nuclear Engineering & Radiation Health Physics
                                   Oregon State University
Turbine Blades
                Droplets in the steam
                flow can destroy turbine
                blades. The design of
                steam separators and
                dryers depends on T/H
                calculations.




 Nuclear Engineering & Radiation Health Physics
                        Oregon State University
      Advanced Thermal-Hydraulic Computer Codes

 Thermal Hydraulic Codes usually model systems

   RELAP5/MOD3: 1-Dimensional Systems Analysis Code (NRC)
   TRAC: 3-Dimensional Systems Analysis Code (NRC)
   RETRAN: 1-Dimensional Systems Analysis Code (Industry)
   NUCLEAR PLANT ANALYZER: 1-Dimensional Systems Analysis
    Code (NRC) with input and output processors for visualization
   COBRA: 1-Dimensional Subchannel analysis code
   GOTHIC: Containment Analysis Code




                      Nuclear Engineering & Radiation Health Physics
                                             Oregon State University
          Basic Conservation Equations
 Thermal Hydraulic Codes function by subdividing the
  system to be analyzed into relatively small control
  volumes or “nodes.”
 Each Node solves the basic conservation equations for
  each fluid and phase (gas or liquid) present in the node:
    Mass
    Momentum
    Energy
 The output of one node serves as the input to the next
  node. In this way, a model for the entire loop can be
  constructed.

                     Nuclear Engineering & Radiation Health Physics
                                            Oregon State University
           Mass Conservation Equation
Transient Conditions:
            dM
                              
                               min         
                                            mout
             dt

        mass change         mass flow       mass flow
        with time           rate in         rate out

Steady-State Conditions:
                          dM
                               0
                           dt


 So:
                               
                          min  mout

                      Nuclear Engineering & Radiation Health Physics
                                             Oregon State University
RELAP5 APEX Nodalization




      Nuclear Engineering & Radiation Health Physics
                             Oregon State University
  Computational Fluid Dynamics (CFD) Codes
(Steam Generator Lower Plenum Temperature and Velocity Profile)




                      Nuclear Engineering & Radiation Health Physics
                                             Oregon State University
              The Next Generation T/H Codes

 In the near future, Best-Estimate T/H Computer Codes
  will be used for licensing purposes.
    3-D with multiple fluids and fluid phases
    Uncertainty estimates for all models used in the codes
    Possibly CFD codes for turbulence and mixing modeling for
     phenomena of safety significance.




                       Nuclear Engineering & Radiation Health Physics
                                              Oregon State University