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					Behavior of Containment Emergency Systems:
Behavior of Containment Emergency Systems:
        A Review of State of the Art
         A Review of State of the Art

                 Mamoru Ishii

   Thermal-Hydraulics and Reactor Safety Laboratory
            School of Nuclear Engineering
                  Purdue University
              West Lafayette, IN 47907

• Introduction
• PUMA-PCCS Separate Effect Test
• PANDA ISP-42 Test
• JAEA’s Research Project on Horizontal Heat Exchanger
  for PCCS
• Code Evaluations for PUMA Integral Test Including
  PCCS Performance
• Code Capabilities
• Summary

    Phenomenon 4: Behavior of Containment Emergency Systems
•   Focus of Phenomenon 4
    – Natural Circulation Cooling and Heat Transfer in Various Containment
      Passive Cooling Systems under Accident Conditions to Remove the
      Energy out of the Containment by Natural Circulation and Condensation
      Heat Transfer
    – Typical Systems are the Tube Condensers Such As the PCCS in
      SBWR/ESBWR and External Air Cooling Systems in AP600/1000
•   Purpose of the Containment Safety Systems
    – To Protect the Containment under Both DBAs and Severe Accidents
    – To Prevent the Significant Release of Radioactive Materials to the
•   Requirements for the Containment Safety Systems
    – To Remove the Load on the Containment under Accidents
    – Most of the Load Comes from the Released Steam from the Reactor
      Primary Coolant System
    – Noncondensable Gases will Affect the Condenser Efficiency
                              Definition of Phenomenon 4
Nuclear power reactor containments are equipped with safety systems which protect the containment
integrity under various accident conditions. The focus of Phenomenon 4 is the natural circulation
cooling and heat transfer in various containment passive cooling systems under accident conditions to
remove the energy out of the containment by natural circulation and condensation heat transfer.
Typical systems are the tube condensers such as the Passive Containment Cooling System (PCCS)
and external air cooling system or external liquid film cooling and internal condensation of steam in
the containment by natural circulation. The major purpose of these containment systems is to protect
the containment under both Design Basis Accidents (DBAs) and severe accidents involving serious
core damages and to prevent the significant over pressurization and release of radioactive materials
to the atmosphere. These systems are required to remove the load on the containment from the Loss
of Coolant Accidents (LOCAs) and other accidents by removing the heat but containing the mass
within the structure. Most of the load comes from the released steam from the primary coolant system
due to the LOCA or venting of the pressure relief valves. The major part of the noncondensable (NC)
gases consists of the original containment atmosphere such as air or nitrogen, however with the core
damage, hydrogen or fission gases can also be released into the containment atmosphere. The
thermal-hydraulic phenomena of importance are tube surface condensation with NC gases, natural
circulation of steam and NC gases, degradation of condensation by the accumulation of NC gases
and purging of NC gases from condenser systems. The PCCS can be vertical or horizontal tube
condensers in external water pool, exposed condenser tube system in the containment cooled by
natural circulation water through the tubes from the external pool or by external air circulation and

•   The Final Barrier Against the Release of Radioactive Materials into
    the Environment

       ESBWR Containment
       Figure Comes from
                  Passive Safety Systems for Containment
Passive Safety System for Containment Utilize Natural Circulation and Condensation
Heat Transfer to Suppress the Pressure and Temperature of the Containment

•Vertical PCCS Condenser (GE’s SBWR/ESBWR); Leonardi et al., 2006
•Horizontal PCCS Condenser (Japan); Kondo et al., 2006
•External Air Cooling System (Westinghouse’s AP600/1000); Sha et al., 2004

                                         Test Facilities
    Full height, 1/400 volume ratio test facility simulates GE’s SBWR;
    Performed separate effects and system response tests;
    Full height, 1/25 volume ratio test facility simulates GE’s SBWR;
    Performed tests to check the effects of the NC concentration and pool inventory;
    Performed tests to investigate the PCCS start-up and long-term capabilities;
    Full size prototypic heat exchangers;
    Performed tests under the same thermal hydraulic conditions as GIRAFFE and PANDA;
•   PUMA
    1/4 height ratio, 1/400 volume ratio test facility simulates GE’s SBWR/ESBWR;
    Performed separate effects tests to check the effects of the NC concentration;
•   LSTF
    Full height, 1/48 volume ratio test facility simulates Westinghouse PWR;
•   Horizontal Heat Exchanger Test Facility in JAEA
    Halved full height, prototypical-scale bundle to represent one of four HEXs in ABWR-II;
    Single-tube test and tube bundle test have been performed;

                Contributions from the CRP Participants
•   PUMA-PCCS Separate Effect Test
    Purdue University, USA; 3rd RCM
•   Overview on PANDA Test Facility and ISP-42 PANDA Tests Data
    Paul Scherrer Institute, Switzerland; 2nd RCM
•   JAEA’s Research Project on Horizontal Heat Exchanger for PCCS
    Japan Atomic Energy Agency, Japan; 2nd RCM
•   Code Evaluations for PUMA Integral Test Including PCCS
    Purdue University, USA; 2nd RCM

            PUMA-PCCS Separate Effect Test

•   To study the effect of noncondensable gas concentration on PCCS
    performance using PUMA for three operational modes:
     – Bypass Mode
     – Cyclic Venting Mode
     – Long-Term Cooling Mode
•   To study the effect of PCCS inlet (Drywell) pressure
•   To study the effect of PCCS inlet flow rate
•   To study the effect of PCCS pool water level
•   To compare the test results with other data

PUMA-PCCS Separate Effect Test
           Test Facility

                    PUMA-PCCS Separate Effect Test
                                     PCCS Operational Modes


                                                    Venting Frequency Decreases
                         Vent Line

       Drain Line


                          SP                            SP                       SP

       •      Blowdown period           •   After GDCS water        •   Final phase of LOCA
              before GDCS water             injection and restart   •   Low NC gas fraction
              injection to RPV              boiling in RPV              (< 1%)
       •      Continuous flow           •   NC gas                  •   Venting frequency
              through NC gas                accumulation in the         approaches zero
              vent line                     PCCS                        (ideal case)

            PUMA-PCCS Separate Effect Test
                             Test Matrix
             Steam Mass               Saturation NC Gas Mass     PCCS Pool
  Test        Flow Rate   Pressure
                                     Temperature Flow Fraction   Water Level
  Mode          (kg/s)     (kPa)
                                         (oC)        (%)            (m)
                            200         120
 Cooling                    230         124           <1         0.92, 0.60
              ~ 0.028
                            260         128

                            220         123
 Venting                    240         126        0.3, 2, 4     0.92, 0.60
              ~ 0.042
                            260         128

                            220         123
 Bypass         0.060
                            260         128        0, 10, 15        0.92
  (BY)        ~ 0.075
                            300         133

PUMA-PCCS Separate Effect Test
                    Energy Balance

                                    •   Energy Balance

   Pure Steam

                                         •   NC Gas Effect on Energy
                Steam-Air Mixture
                                              – As NC gas fraction
                                                 increases, àNC gas
                                                 purging with steam
                                                 increaseà increase of
                                                 mass and energy
                                                 discrepancies between
                                                 PCCS inlet and outlet

         PUMA-PCCS Separate Effect Test
               NC Effect on Heat Transfer Coefficient

                                      •   NC Gas Effect on Average HTC
  Cyclic Venting
                                           – As NC gas fraction increases,
                                             HTC decreases due to the
                                             increase of thermal
                                             resistance in the gas phase.
                                           – As NC gas fraction increases,
                                             the discrepancies between
                                             PUMA, Kuhn and Vierow’s
                                             data decrease, because the
                                             NC venting condition is
                                             getting closer to a single-tube
                                             experiment (flow-through
                                             mode) as NC gas fraction

PUMA-PCCS Separate Effect Test
   Combined Correlated Test Results

                        •   Combined correlated data
                            compared with PUMA-PCCS
                            test data

                             – Both cyclic venting and
                               bypass with continuous
                               venting follow the same
                               trends as other research

                             – PUMA and PANTHERS
                               data fall on the same heat
                               transfer coefficient trend
PANDA ISP-42 Test Review

JAEA’s Horizontal Heat Exchanger Test Review

Code Evaluation for PUMA Integral Test
              PUMA Facility

Code Evaluation for PUMA Integral Test
           RELAP5 Nodalization

Code Evaluation for PUMA Integral Test
               MSLB Test

Code Evaluation for PUMA Integral Test
       Test Data vs. RELAP5 Simulation

          Downcomer Collapsed Water Level

Code Evaluation for PUMA Integral Test
          Test Data vs. RELAP5 Simulation

  Drywell Pressure            GDCS Loop A Injection Flow Rate

 Code Evaluation for PUMA Integral Test
               Test Data vs. RELAP5 Simulation

Decay Heat Removal, Test Data      Decay Heat Removal, RELAP5 Prediction

        Code Evaluation for PUMA Integral Test
                          Summary of Code Evaluation
•   RELAP5 was Evaluated
    PUMA Model of RELAP5

•   Code Modeling Problems
    –    Suppression Pool Condensation Model
         1-D Model Insufficient
         Recirculation Pass ® Instability
         Artificial Flow Restriction Required
    –    Suppression Pool Over Stratified
         1-D Model Insufficient
         Containment Pressure Affected
    –    Film Condensation Model (PCCS & ICS)
         Insufficient Modeling Accuracy
         Effect of Noncondensable Gas not Certain
         Containment Pressure Affected

•   Overall Performance
    All Major Events and Trends Predicted
    Facility and Code Scaling Capability are Good
    PCCS Condensation Rate Improvement Desired
    RELAP-5 appears Adequate for DBA Analysis

                             Code Capabilities
      Heat Transfer Models in Thermal Hydraulic System Code
•   TRACE Mode 4.0
    – Wall Vapor HTC: Nusselt and empirical model

    – Wall Liquid convention HTC: flow factor F:Chen correlation

    – Interfacial Heat Transfer: Empirical model of Sklover & Rodivilin
       Developed for cross-flow of gas-vapor mixtures on liquid jets

•   RELAP Mode 3.3 Beta
    – Default Model: Saha, Nusselt

    – Alternative model: UCB model

                Code Capabilities
RELAP5 Calculation Comparing with PUMA Experimental Data

                                  •Default Model: Under predict

                                  •UCB model: over predict and

                                  •Kuhn Correlation: Fluctuation

                                  •One of main reason of
                                  disagreement is caused by
                                  limitation of NC gas venting
                                  phenomenon in SP water in the
                                  code calculation

                              Code Capabilities
       Code Calculation Comparing with PUMA Experimental Data

Table. Cooling Capability Comparison •      When steam with NC flow àmore discrepancy
(inlet steam flow/condensate water flow)    between experimental data and code
                                            calculation in terms of condensate water flow
  Test Mode      PUMA   RELAP   TRACE       and temperatures inside condenser tubes; It
   (NC %)         (%)    (%)     (%)        may be caused by condensation model
                                            limitation in calculating NC gas profile in the
 Long Term        93     96      62         condenser tubes and venting of gas to
   (0.5%)                                   suppression pool water.
Cyclic Venting    83     71      43
   (2.5%)                               •   Saturation temperatures of inlet, outlet and
 Blow Down        56     28      27         condenser tubes are over-predicted compared
 Mode (15%)                                 to experimental data when the NC gas exiting.

                                        •   Code couldn’t simulate cyclic venting of the NC

                         Code Capabilities
        Code Calculation Comparing with PANDA ISP-42 Data
•   Overall Best Results were Obtained by the Lumped Parameter Code
•   System Codes like CATHARE and RELAP5 Produced Acceptable Results;
•   Containment Code COCOSYS Produced Acceptable Results;
•   CATHARE and RELAP5 have the Flexibility to Simulate Special
    Components, like the PCCS;
•   Strict QA Procedure for Nodalization and Input Deck Generation should be
•   Appropriate Input Parameters should be Given in the Code Analysis;
•   Lumped Parameter Approach should be Chosen for Simple Physical
    Situations (i.e., PCCS Start-up Phase);
•   Further Assessment of the 3-D Models and Advanced Modeling Features
    are Necessary;
•   No CFD Codes Calculation has been Submitted.

                              Code Capabilities
    Code Calculation and Development in JAEA’s Research Project
•   Code Development
     –   RELAP5 for Primary Side Calculation
     –   ACE-3D was Developed for Secondary Side Calculation
     –   RELAP5 and ACE-3D Coupled at the Condenser Tube Surface
     –   Calculation Successfully Predicted the Distribution of the Quality in the Condenser
         Tubes and the Void Fractions in the Bundle Side
•   RELAP5 MOD3 Modification
     – Heat Transfer Package was Developed for Modeling the Horizontal Heat
     – Model Predicted Well the Total Heat Removal Rate and the Pressure Drop Across
       the Heat Exchanger

• Introduction to Phenomenon 4
• Review of the Recent Research Results on PCCS
   – PUMA Separate Effect Test (Vertical PCCS for SBWR/ESBWR)
   – PANDA ISP-42 Test (Vertical PCCS for SBWR/ESBWR)
   – Horizontal Heat Exchanger Test in JAEA (Horizontal PCCS for
• Review of the Code Capabilities
   – System Code (RELAP5, TRACE)
   – System Code Coupled with 3-D CFD Code (RELAP5/ACE-3D)


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