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					 ANS PSA 2008 Topical Meeting - Challenges to PSA during the nuclear renaissance,
 Knoxville, Tennessee, September 6–11, 2008




Implementation of a Concept for a Risk-informed
Diagnosis/Prognosis of Plant States through the
RISARD System




Kwang-Il Ahn
kiahn@kaeri.re.kr

Integrated Safety Assessment
Korea Atomic Energy Research Institute
⊙ Outline


           Motivation & Objectives
           The Concept of RI-SAM
           Computerized Tool SARD
           Demonstrative Application
           Concluding Remarks




  KAERI                                 2
⊙ Motivation

      Key Ways for a Successful Implementation of SAM

     Develop a proper SAM strategy by answering the questions:
          How to reduce uncertainties in implementing the established SAM strategies?
           especially when available resources are limited.
          Which essential safety function was lost at the time of the accident? That is, the root
           cause of the accident; Which safety systems are currently available for SAM?
          What will be important future events? and what will be their evolution?
          What are potential ‘success paths’ for SAM?

     Utilize the computer-based methods & tools for supporting SAM:
      capable of ① diagnosing the functional states of plant safety systems and ② predicting the
      future trends of key plant parameters as possible as quickly:
          The diagnostic capability for plant states at the time of the accident is required to
           reduce the uncertainties in the current plant system state and to have a good basis for
           estimating future plant states.
          Based on the current damage states of the plant, the prognostic capability for the
           possible evolution of the accident gives time enough to take an action for mitigating the
           consequence of the accident.


  KAERI                                                                                                3
⊙ Objectives:               RI-SAM Strategy & Tool


     Our Approach for supporting SAM:

          Utilize a PSA-based and SA phenomenological trends-based database (DB) (e.g.,
           plant-, code-, accident sequence-specific SA analysis results) => SAR DB
                Systematic use of SAM-related information
                Quick & fast retrieval of the SAM-related information (Quick view)

          Provide a computerized platform for a comprehensive use of SAR DB in a simple,
           fast and risk-informing way => RI-SARD
                Proper information about the plant damage states at the time of the accident: the
                 root cause of the accident (Diagnosis)
                Insights on the possible evolution of the accident (critical parameters), based on the
                 current damage states of the plant (Prognosis)

          Develop the best strategy for supporting SAM (especially when available plant
           information is limited) => RI-SAM
                Helpful in finding success paths for intended SAM actions
                Helpful in providing appropriate actions to mitigate the accident




  KAERI                                                                                                   4
⊙ RI-SAM:                        Diagnosis & Prognosis of Plant States


               Monitor Plant Data & Signal:
               Identify the IE & CD states
               Determine the status/availability of             ReSet             AS screening (iteration loop)(2)
                systems needed to mitigate the IE          Plant symptoms
                                                           & accident time
                                                                                                              Yes
 Signal Validation
     Process                                                                         Prioritize                                 Quick view
                                        Determine            Diagnosis                                         More
                        Plant                                                     Frequency-based                               Future trend
                     symptoms         Plant symptoms       Symptom-based                                      Symptoms
                                                            SARD module           potential accident             ?              of symptom
                                                                                     sequences                                  parameters
                                                                                                              No
                Plant
              Conditions
                                                 Auto switch to module for Prognosis of Future Plant Status


                                                                                     Performance
                                                              Prognosis                                                        Decision for
                       Plant             Determine                                1. Key plant safety
                                      Relevant PDS (1)      Scenario-based                                    Success Paths   Implementation
                damage states                                                     parameters for SAM          Countermeas
                                                             SARD module                                                       of the relevant
                                                                                   2. Performance of                ures      SAM strategies
                                                                                        key SSCs
                                  (dynamic loop)(2)         Modification
                                                         Link to SA Simulator
                                                         for Interactive Action

         Note(1): A prescribed accident sequences by which uncertainty can be reduced in taking an action for SAM.
         Note(2): A process by which the prediction can be updated based upon successive data from plant.
     KAERI                                                                                                                                     5
⊙ A Computerized Tool:                         RI-SARD


   RISARD      Key Functions & Modules
             • Code-specific or user-supplied SA accident sequence information:
   SARDB         characterized as system functionality & frequency (probabilistic information)
             • Plant-, sequence-, code-specific predictions of key plant parameters:
                 phenomenological behavior (phenomenological information)
             • Plant-, sequence-, code-specific predictions for key event histories:
                 based on system functionality & phenomena (evolution of plant states)
             • Sensitivity results and a limited number of uncertainty analysis results:
                 based on available systems & different models (code uncertainty)

             • Automatic allocation SAR data sets into the SARDB
   RI-SARD   • PDS scenario-based prognosis of future events
    Menu     • Plant symptom-based diagnosis of plant damage states
   System          - frequency-based ranking of possible accident sequences
                   - functional states of systems for the given accident sequence

             • SAMG-linked module (decision flow chart, entry time for SAMG)
             • SSC performance (CD, support plate, induced RCS/SG, RPV LH, cont. failure)
             • Code-to-code comparison (MAAP-MELCOR predictions)
             • Additional diagnosis for accident initiators (on-going)

  KAERI                                                                                          6
⊙ SARD:           Data Sets Operation


                                                           SAR Information

                                                      - Level 1/2 PSA
                                                      - Accident Analysis
                                                      - SAM Information
                                                      - The other SAR Inform

          Formatted SAR Data Sets                                          SARD System Operation
              Data Set Spec. for SARD
      - Plant/Code/User ID                                   Data Allocation into
      - Accident Sequence Inform(1)
                                                                   SARDB                            Data Search & Retrieval,
      - Sensitivity Information (Plant
        systems & Model parameters)                                                                    Graphical Display
      - Severe Accident Code Analysis
                                                                                                - Scenario-based Plant
        Results(2) (Code Responses)
                                                              SARDB: Databank                     Responses & Behavior
      - Summary of Key Accident
                                                                                                - Plant symptom-based
        Progression Events (Code Result)                       (MS Access DB)
                                                                                                  Potential Accident Sequences
      - Accident Mitigation Options
                                                                                                - Status of Plant System &
      - Data Set & Databank Index
                                                                                                  Containment Systems
      - Commentary Parts
                                                               Database Update &
           Accident Sequence Types                                Modification
      - PSA code-specific plant damage                                                                 SAR-informed
        event trees for graphical use
      - User-specified events sequence
                                                                                                      Decision-making

     (1) Severe Accident Initiators: LOCA (Large, Medium, Small), Loss of Off-site Power (LOOP), Station Blackout (SBO), Loss of
          Feed Water (LOFW), Interfacing System LOCA, Steam Generate Tube Rupture (SGTR), Anticipated Transient w/o Scram (ATWS),
          Loss of AC Bus (125V, 4.16KV), Large Secondary Side Break, General Transient
     (2) Number of Categorized MAAP Response Parameters (Total 883): RCS/SG/ESF Information (134); Behavior
          of Core and Fuel (152); Lower Plenum Debris Behavior (77); Lower Head Failure Information (85); Containment Information (196);
          Source Term Information (229); Hydrogen Generation (10)

  KAERI                                                                                                                                    7
⊙ SARD:              SARDB Generation (1)

    Plant-specific PDS ET    Identify the initiating event & the status and availability of systems
                               and equipment needed to avoid or mitigate the severe accident
                                                     PDS sequence: plant damage
                                                     state + frequency
                                                     SA phenomenological trends
                                                     with time
                                                     Developing trends of key
                                                     events during accident




                             MELCOR
                             HISPLT                                    SARDB
               MELCOR Run

                            KAERI-IPLOT

   Plant-                                                            SARDB:
                                                 SARDB
  specific                                                          MELCOR/
                                             Generation Module
 Accident                                                           MAAP DB
 Scenarios
                MAAP Run     Plot Data


                                                                  Parameter list
                                                                 for comparison


                                                  SARD:
                                                Plant state
                                                Prognosis/                             Typical Form of SARDB
                                                Diagnosis


                    Allocation of Plant-, Code-specific SA Analysis Results into SARDB
     KAERI                                                                                                     8
⊙ SARD:          SARDB Generation (2)


     Key Role of the PDS ET-based Diagnosis & Prognosis
          Provide the status of plant and cont. systems at the time of core damage
          All potential ASs for an IE can be shown at a glance with its graphical form
          Occurrence probability (or frequency) be systematically derived from PSA
          The graphical form of PDS ET can be very useful in specifying a particular AS
           during the data loading and information retrieval process
          Probability can be utilized as a criterion for screening the risk-significant ASs


                       Frequency                       Number of ASs for each IE
                                                  A frequency criterion for AS screening
            OPR1000 IEs
                                   1.0E-11/ry             1.0E-10/ry                       1.0E-9/ry
            All (16)               Several hundreds       -                                95
            LOOP                   120                    12 (99% of total ASs)            -
            LBLOCA                 30                     7 (99% of total ASs)             -



                                         Risk-informed SA Analysis


  KAERI                                                                                                9
⊙ SARD:                                                           SARDB Generation (3)

Dominant accident initiators:                                                                                                                        I.Es (/ry)    Sequences   Contribution   Functional States of Safety Systems
                                                                                                                                                                               (%) to I.E     (success state: ‘/sss’, failed state: ‘sss’)
Frequency-based screening of PDS sequences                                                                                                                         LLOCA-2     17.01          /SIT*/LPI*/HPR*/HPH*CSS
                                                                                                                                                                   LLOCA-3     19.25          /SIT*/LPI*/HPR*HPH*/CSS
                                       LLOCA PDS ET                                                                                 S    S
   Large
   LOCA
               SITs
             Injection
                             LPSIS
                           Injection
                                          HPSIS
                                         Injection
                                                        HPSIS
                                                        Recir-
                                                                    LPSIS
                                                                    Recir.
                                                                                 HPSIS
                                                                                  Hot
                                                                                            Containment
                                                                                             Injection
                                                                                                             Recir.
                                                                                                            Cooling
                                                                                                                          Cavity
                                                                                                                        Flooding
                                                                                                                                    E
                                                                                                                                    Q
                                                                                                                                         T
                                                                                                                                         A
                                                                                                                                              FREQ
                                                                                                                                                                   LLOCA-5     11.50          /SIT*/LPI*HPR*/LPR/*HPH*/CSS
                                                       culation                 Cold Leg       Spray         using       System     #    T
                                                                                 Recir.                       CSS       Injection        E

  LLOCA        SIT             LPI           HPI           HPR          LPR      HPH             CSI            CSR          RFSI                    LLOCA         LLOCA-8     5.9            /SIT*/LPI*HPR*LPR*HPH*CSS
                                                                                                                                    1    OK
                                                                                                                                                     (1.05x10-6)   LLOCA-9     45.36          /SIT*LPI*/HPI*/HPR*/CSS
                                                                                                          CDSQ2                     2    43
                                                                                                                                                                   LLOCA-15    0.46           /SIT*LPI*HPI*HPR*LPR*HPH*CSS
                                                                                                                                    3    27
                                                                              CDSQ3
                                                                                                          CSR                       4    28                        LLOCA-17    0.15           SIT*/LPI*/HPR*/CSS

                                                                                                          CSR
                                                                                                                                    5    27
                                                                                                                                                                   Sub total   99.63
                                                                                                                                    6    28
                                                     CDSQ4


                                                                  LPR
                                                                                                                                    7    29                        MLOCA-2     28.15          /HPI*/HPR*/HPH*CSR
                                                                                                          CSR
                                                                                                                                    8    30
                                                                                                                                                                   MLOCA-3     31.87          /HPI*/HPR*HPH*/CSR
                                                                                                                                    9    27

                                                                                                          CSR
                                                                                                                                    10   28
                                                                                                                                                                   MLOCA-5     10.07          /HPI*HPR*/LPR*/CSR
                                                                                                                                    11   29          MLOCA         MLOCA-8     9.0            /HPI*HPR*LPR*CSR
                                                     HPR
                                                                                                          CSR
                                                                                                                                    12   30
                                                                                                                                                     (6.34x10-7)
                         CDSQ5

                                                                                                                                    13   29
                                                                                                                                                                   MLOCA-9     19.1           HPI*/LPI*/LPR*/CSI*/CSR
                                                                                                          CSR
                                       HPI
                                                                                                                                    14   30
                                                                                                                                                                   MLOCA-19    0.76           HPI*LPI*CSI
                                                                                                                                    15   31
                                                                                           CSI
LLOCA
                                                                                                                      RFSI          16   32
                                                                                                                                                                   Sub total   98.95
                                                                                                                                    17   27
                                                                                                                                                                   SLOCA-11    0.05           /HPI*/AFW*/ADV*HPR*LPR*/CSS
                                                                                                          CSR                       18   28


                                                                                                                                    19   27
                                                                                                                                                                   SLOCA-12    57.79          /HPI*/AFW*/ADV*HPR*LPR*CSS
                                                                                                          CSR
                                                     HPR
                                                                                                                                    20   28
                                                                                                                                                                   SLOCA-13    0.27           /HPI*/AFW*/ADV*HPR*/LPR*/CSS
                                                                                                                                    21   29
                                                                  LPR
                                                                                                          CSR
                                                                                                                                    22   30
                                                                                                                                                                   SLOCA-21    0.08           /HPI*/AFW*ADV*/MSSV*/HPR*BDL*/CSS
           CDSQ6
                                                                                                                                    23   27

                                                                                                                                                     SLOCA         SLOCA-26    0.14           /HPI*/AFW*ADV*/MSSV*HPR*LPR*CSS
                                                                                                          CSR
                                                                                                                                    24   28
                                                                                                                                                     (1.92x10-6)   SLOCA-45    0.19           /HPI*AFW*/LPR*BDE*/CSS
                                                                                                                                    25   29
                                                     HPR


                         LPI
                                                                                                          CSR
                                                                                                                                    26   30
                                                                                                                                                                   SLOCA-55    1.19           HPI*/AFW*ADV*/MSSV*/HPR*BD*/CSS
                                                                                                                                    27   29

                                                                                                          CSR
                                                                                                                                    28   30
                                                                                                                                                                   SLOCA-57    5.12           HPI*/DPI*LPI*CSI
                                       HPI


                                                                                           CSI
                                                                                                                                    29   31
                                                                                                                                                                   SLOCA-59    32.6           HPI*DPI*/LPI*/CSI
                                                                                                                      RFSI
                                                                                                                                    30   32

                                                                                                                                                                   Sub total   97.43

           KAERI                                                                                                                                                                                                                             10
⊙ SARD:           SARDB Generation (5)


                Events history:      SAMPLE: Key Events Summary for LF115 (MAAP)
                                      Time    Events Code   Functional Status
                 Plant system          0.000     157:T        MAIN FW OFF
                status with time       0.000     224:T        MOTOR-DRIVEN AUX FEED WATER FORCED OFF
                                       0.000     232:T        CHARGING PUMPS FORCED OFF
                                      17.836     31:T         PZR SPRAYS ON
     PDS                              37.431     13:T         REACTOR SCRAM
  sequence-                           37.431     156:T        MSIV CLOSED
                                      42.578     153:T        SEC SV(S) FIRST OPEN BROKEN S/G
 specific SA                          42.578     163:T        SEC SV(S) FIRST OPEN UNBROKEN S/G'S
     code                            867.556     161:T        UNBKN S/G DRY
                                     870.375     151:T        BROKEN S/G DRY
   analysis                          1109.376    3:TH         VALVE FIRST OPENED
                                     1109.376    4:TH         VALVE FIRST OPENED
                                     1109.376    5:TH         VALVE FIRST OPENED
               Parameters history:   1113.182    35:T         VOID FRACTION IN PZR < 0.1
               SA code parameter     1728.464    4:T          MAIN COOLANT PUMPS OFF
                                     2584.444    691:T TRUE: CORE HAS UNCOVERED
               behavior with time    4888.784    509:T TRUE: MAX. CORE TEMP EXCEEDS 2200. F
                                     5084.019    690:T TRUE: MAXIMUM CORE TEMPERATURE HAS EXCEEDED 2499 K
                                     5188.688    508:T        TRUE: MAX. CORE EXIT TEMP EXCEEDS 1200. F
                                     5962.269    2:T           RELOCATION OF CORE MATERIALS TO
                                                                   LOWER HEAD STARTED
                                     5987.935    103:T        UPPER COMPT. SPRAYS ON
                                     6778.318    3:T          RV FAILED
                                     6794.329    5:T          HPI ON
                                     6794.329    6:T          LPI ON
                                     6857.934    188:T        ACCUMULATOR WATER DEPLETED
                                     8142.179    1003:T TRUE: 1 TH COMPT BURNING IN PROGRESS
                                     8142.179    1048:T TRUE: 4 TH COMPT BURNING IN PROGRESS
                                     8142.179    1063:T TRUE: 5 TH COMPT BURNING IN PROGRESS
                                     8142.492    1033:T TRUE: 3 TH COMPT BURNING IN PROGRESS
                                     9897.961    5:F HPI OFF
                                     9897.961    181:T        RECIRC SYSTEM IN OPERATION
                                     ….
  KAERI                                                                                                     11
⊙ SARD:                SARDB Generation Module




           SAR Data
      ASQ data      Plant Data

     SA Code data Code results
                                                           Specification of Code Data (Multiple)

        AMP & Summary Data




                                                Specification of Databank Index             Specification of Code Data (Single)
     Specification of the Target Scenario




     Specification of Sensitivity Information
                                                                                              Check of the Allocated Information




                                                          SARDB
                                                       MS Access DB




  KAERI                                                                                                                            12
⊙ SARD:          Two-way information Retrieval


                                                         Set target
                                                    Plant ID & Code ID



                          Scenario Base (1)                                Symptom Base (2)

                            PSA Information:                                 Plant Symptoms:
                          IE & Target Sequence                             - Code Parameters
                                                                           - Time windows
                                                         More symptoms?
                                                          AS Screening
                             Data Search:
                            Plant-/Code-/AS                                Prioritize Accident
                           sequence-specific                              Scenarios (i = 1, n), in
                              Responses                                   a risk-informing way

                                                 Auto
                                                 Switc                      Target Sequence
                          Display                 h
                      -   Plant states
                      -   Base response
                      -   Sensitivity case
                      -   SAMG parameters
                      -   SSC performance                          End
                      -   Events History                            of
                                                                  Searc
                                                                    h
          (1) Retrieval of the specified- accident sequence-based plant/code behavior (Accident Diagnosis)
          (2) Retrieval of plant symptoms-based potential accident sequences (Accident Prognosis)

  KAERI                                                                                                      13
⊙ SARD: Plant Symptom-based Diagnosis


                                                       PDS ET Events Functional Status
           Set Plant & Code information




                                                              The most probable
                                   List of potential          plant system state
                                    plant damage                                          Switch to
                                        states                                           Switch to Module
                                                                                   the Scenario-based
                                                                                  the Scenario-based Module



                                                                Progression
                                                               of key events                            Future trend of
                                                                                                       plant parameters

                                    User- specified
                                   plant symptoms




   KAERI                                                                                                                  14
⊙ SARD:            PDS sequence-based Prognosis




                                                         Display of the Corresponding PDS ET   PDS ET Events Functional Status
          Set Plant & Code information




                                          User- specified
                                         accident conditions




                                   User- specified
                                     code/plant
                                    parameters




                                                                            Future history key events &
                                                                                 plant parameters




  KAERI                                                                                                                          15
⊙ Demo Application: Diagnosis of PDS sequences
                    Target: OPR1000-/MAAP-specific SARDB for 6 Initiating Events
                           (Large/Medium/Small LOCAs, LOOP, SBO, SGTR)
       1. Initial Plant Symptom
       (1) TWCR (temperature of water in core, K) [580-600] for Time Window (Sec.) [110-130]
      Matched PDS Sequences           Freq. (/ry)     Functional States of Safety Systems
       SBLOCA_S012                     1.109E-06      SLOCA*/RT*/HPI*/AFW*/SR1*HPR*/DPR*LPR*CSR
       SBLOCA_S059                     6.256E-07      SLOCA*/RT*HPI*DPI*/LPI*/LPR*/CSI*/CSR
       SBLOCA_S055                     2.281E-08      SLOCA*/RT*HPI*/DPI*LPI*/CSI*/CSR
       LOOP_S053                       1.205E-08      LOOP*/RT*/AFW*SR1*/SR2*MSHR*BD*/LPI*/LPR*/CSI*/CSR
       SBLOCA_S058                     1.150E-08      SLOCA*/RT*HPI*/DPI*LPI*CSI*
       SBLOCA_S013                     5.270E-09      SLOCA*/RT*/HPI*/AFW*/SR1*HPR*DPR*/LPR*/CSR
       SBLOCA_S045                     3.590E-09      SLOCA*/RT*/HPI*AFW*BDE*/LPR*/CSR
       SBLOCA_S026                     2.593E-09      SLOCA*/RT*/HPI*/AFW*SR1*/SR2*HPR*LPR*CSR
       SBLOCA_S021                     1.598E-09      SLOCA*/RT*/HPI*/AFW*SR1*/SR2*/HPR*MSHR*BDL*/CSR
       SBLOCA_S011                     1.058E-09      SLOCA*/RT*/HPI*/AFW*/SR1*HPR*/DPR*LPR*/CSR
       LOOP_S064                       4.141E-10      LOOP*/RT*/AFW*SR1*/SR2*MSHR*BD*LPI*CSI*RFSI
       SBLOCA_S070                     1.759E-12      SLOCA*/RT*HPI*DPI*LPI*CSI*RFSI
    2. Two Additional Plant Symptoms
       (2) PPS (pressure in primary system, MPa) [12.50-12.51] for Time Window (Sec.) [110-130]
       (3) TGUP (temperature of gas in upper plenum, K) [600-620] for Time Window (Sec.) [110-130]
       The corresponding         SBLOCA_S012, SBLOCA_S059, SBLOCA_S055, SBLOCA_S058, SBLOCA_S013,
       PDS Sequences             SBLOCA_S045, SBLOCA_S026, SBLOCA_S021, SBLOCA_S011, SBLOCA_S070
    3. Two Additional Plant Symptoms
       (4) TWCR (temperature of water in core, K) [550-600] for Time Window (Sec.) [1950-2050]
       (5) TWCR (temperature of water in core, K) [435-445] for Time Window (Sec.) [2950-3050]
       The corresponding PDS Sequences                SBLOCA_S012, SBLOCA_S013, SBLOCA_S011
   KAERI                                                                                                   16
⊙ Demo Application: Prognosis of Future Trend

     Future Trends of ‘TWCR’ for the                    After Screening      Diagnostic result: future trend of
     Predicted 11 PDS Sequences                                              ‘TWCR’ for ‘SBLOCA_S012’
                                                                          SBLOCA_S012: SLOCA*/RT*/HPI*/AFW*/SR1*HPR*/DPR*LPR*CSR




                   TWCR: temperature of water in core (K)




                                                                                                SBLOCA_S012: TWCR




   KAERI                                                                                                                           17
⊙ SAM-Decision Flow Chart (DFC)-SAMG entry time
                                                                       Making predictions about future trend of the 7 plant
                   LBLOCA-S03                                        safety parameters to trigger the relevant SAMG and their
                                                                       entry times, based on the user-specified thresholds

                                        S/G Water Level


                                                                                                SAMG Entry Time !
                                                          Entry time: 6.85 sec.




                                                          Entry time:10.4 sec.




                         RCS Pressure



                                                          Entry time: 30.32 sec.




           Containment Pressure




   KAERI                                                                                                                        18
⊙ SAM-SSC Performance-failure time & probability

Making predictions about when core damage, core support
plate failure, induced RCS & SG creep failure, reactor vessel                            SBLOCA-S26
           failure, and containment failure will occur

                                                                                            Water level in RPV




                                                       Core uncover
                                                       at 19876 sec.

                                                                       RCS HL: unbroken                    RCS HL: broken




                                                   No induced creep
                                                        failure         S/G: unbroken                        S/G: broken


                                                  RPV LH Creep at
                                                    37355 sec.


                                                                          PRV LH creep                     P-tube ejection




                                                                         P-tube heatup              Debris jet impingement




      KAERI                                                                                                                19
⊙ Concluding Remarks

     Summary
          Based on a concept of a RI-SAM, the present RI-SARD system explores
                a symptom-based diagnosis of potential PDS sequences in a risk-
                 informing way &
                a plant damage sequence-based prognosis of key plant parameter
                 behavior, in a simple, fast, and efficient way.
          The replicated use of both processes makes it possible to extract
           information required for taking the intended SAM actions, consequently
           leading to an answer about what is the best strategy for SAM.
          An example application through the OPR1000- and MAAP code-specific
           SAR DB has shown that the present approach can
                enhance a diagnostic capability for anticipated plant states,
                give the SAM practitioners more time to take actions for mitigating the accident,
                reduce the still relatively large uncertainty in the field of SAM, and
                consequently, help guide the TSC staffs through a severe accident.




  KAERI                                                                                              20
⊙ Concluding Remarks

     Future Plan for Improvement
          Will involve the ability to link decisions made by RISARD with the SAM
           procedure and SA simulator, so that the impact of the SAM actions on an accident
           progression can be feedback to in an interactive way to a user.
          Will involve the use of a more structured approach capable of ① diagnosing
           the current plant system state, ② predicting the most probable accident pathway during
           the progress of an accident, and ③ taking the best strategy to terminate its progression
           into an undesirable consequence, including a linking with

                a diagnostic logic tree to diagnose effectively potential plant damage states,
                a simplified APET capable of predicting the progress of accidents accurately,
                 and
                a more sophisticated logical rule capable of extracting appropriate SAM
                 strategies for a given plant damage state

          In addition, we will explore increasing the number of accident types recognized
           by RI-SARD (e.g., various spectrum of break sizes for LOCA & SGTR)




  KAERI                                                                                               21
Thank you for your attention !!!

				
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