Engineering & Projects Organization

Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.1

Engineering & Projects Organization

Finding the best approach for I&C modeling in the PSA

H. BrunelièreAREVA NP SAS PSA teamVienne, 2nd October 2012

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.3

Agenda

Introduction

“Compact model”

Detailed modeling� Elaboration and documentation of the methodology

� Implementation of the I&C signals in the PSA

� Advantages

Conclusion

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.4

Introduction

Methodology for modeling of probabilities of failur e per demand of I&C functions in the PSAs of Nuclear Powe r Plants

Applicable to new and existing plants

I&C reliability analyses (fault trees for modeling I&C in a dedicated model out of the PSA) are not in the scop e of this paper

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Introduction

Need for a modeling consistent with design progress

�From a compact model…

�…to a more detailed modeling

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.6

Introduction

Instrumentation part � I&C level 0

Processing part� I&C level 1

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.7

“Compact model”

� Each I&C signal has three parts• Instrumentation part• “specific processing part”• “non-specific processing part”

� Values for unavailability• Dépend of classification and

architecture of systems

Instrumentation

Processing (Specific)

Processing (non specific)

Actuator

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.8

“Compact model”Instrumentation

Equipment class

E1A E1B, E2 or NC

Redundancy 2/4 2/3 2/4, 2/3 or 1/2

1/1

Unavailability 1E-04 / demand

3E-04 / demand

1E-03 / demand

1E-02 / demand

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.9

“Compact model”“Specific processing part” (specific to a signal)

“Non-specific processing part” (not specific to a sig nal but specific to a platform)

Equipment class

E1A E1B, E2, NC

Unavailability 1E-04 / demand 1E-03 / demand

Equipment class E1A E1B, E2, NC

Unavailability 1E-05 / demand 1E-04 / demand

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.10

“Compact model”

Advantages of this modeling� Accounts of main contributors = common cause failur es

� Possibility of implementation at the beginning of p rojects

� Easy to implement for sensitivity studies on desig n choices

� Easy to read the cutsets involving I&C failures

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.11

Detailed modeling

Elaboration and documentation of the methodology

Implementation of the I&C signals in the PSA

Conclusion

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.12

Elaboration and documentation of the methodology

Methodology based on� Comparison performed at the beginning of 2011 betwe en I&C models in

EPR PSAs

� Expert and engineering judgments based on• Olkiluoto 3, Taishan 1&2 and US EPR PSA models• Detailed I&C reliability studies• Knowledge of the systems behavior

� Work between AREVA NP PSA teams (SAS, Inc and GmbH) during 2011• 4 dedicated meetings• 9 people involved (including EPR I&C PSA practitioners)• All aspects of the comparison addressed

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.13

Elaboration and documentation of the methodology

Methodology document written in parallel� Results of the work.

� Bases for modeling assumptions and reliability data substantiation.

� Details for practical implementation• Examples included

� Modeling recommendations.

Methodology document can be easily used in the fram e of a project as part of PSA documentation.

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.14

Implementation of the I&C signals in the PSA

Instrumentation part

I&C

system 1

I&C

system 2

I&C

system n. . .

Pre-Processing

(optional)

Signal

Multiplication

and distribution

Sensor

Conditioning

I&C System

SENSOR

Link

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.15

Implementation of the I&C signals in the PSA

Instrumentation part modeling� Modeling at sensor level

� Conditioning modules included

Failure of the sensor XXX

XXX

Failure of the conditioning module YYY

XXX_COND

OR

Failure of the instrumentation part

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Implementation of the I&C signals in the PSA

Instrumentation part modeling� Redundant sensors are

required for the elaboration of the signal => logic gate in order to represent failure criterion

� Degradation of voting logics conservatively not considered in the PSA modeling

• Avoid complexity• Conservatism negligible• Addressed in detailed I&C

reliability studies if necessary

Voting logic Number of sensorsLogic gate used in the PSA

(failure criterion)

2/4 4 sensors ≥ 3

2/3 3 sensors ≥ 2

2/2 2 sensors OR

1/2 2 sensors AND

1/1 1 sensor OR

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.17

Implementation of the I&C signals in the PSA

Instrumentation part� Reliability data based on

• Hourly failure rate of sensors• Efficiency of the internal self-tests• Time interval between periodic tests• Mean Time to Repair (MTTR) the component

� Common cause failures applied • For sensors• For conditioning modules when relevant

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.18

Implementation of the I&C signals in the PSA

Processing part� Elementary components used for the modeling of I&C processing parts

are the single processing units

� Based on analyses of I&C systems, specific reliabil ity values are determined for each unit

Unit composed of� Sub racks for mounting the modules

� Processing module(s)

� I/O modules

� Communication modules

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.19

Implementation of the I&C signals in the PSA

Processing part

SIS_DPSAT_TRAIN1

Failure of SIS actuation train 1 on low delta P sat

@SIS_DPSAT_TRAIN1-2

failure of acquisition part (APU + sensors)

>_ 3

@SIS_DPSAT_TRAIN1-5

Failure of ALU division 1 processing part

@SIS_DPSAT_TRAIN1-6

Failure of non-specif ic processing part

SIS_DPSAT_AC_TR1_1

failure acquisition division

SIS_DPSAT_AC_TR1_2

failure of acquisition division 2

SIS_DPSAT_AC_TR1_3

Failure of acquisition division 3

SIS_DPSAT_AC_TR1_4

failure of acquisition division 4

ALUB1_DIV1 ALUB2_DIV1 CCF_TXS

Failure of the w hole TXS platform

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.20

Implementation of the I&C signals in the PSA

Processing part� Reliability data based on

• Inputs from manufacturer- Failure rates for each failure mode

• Periodic tests frequency• Mean Time to Repair

� CCF considered• Between units that perform redundant processing in the same system (application

level)• At platform level (value given for the loss of a whole I&C platform due to hardware or

software CCF)

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Finding the best approach for I&C modeling in the P SA – H. Brunelière – 2nd October 2012 - p.21

Implementation of the I&C signals in the PSA

Methodology for modeling of I&C functions in the PS As of NPPs for which the allocation of functions in the u nits is defined

Principle of the method (except need for modeling s oftware failures) remains applicable for not digital platfo rms

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Advantages

Links between I&C and support systems are easy to implement in the model

Hazards analyses integrate I&C

Detailed modeling of units allows the detection of asymmetries or imbalances in the I&C design (non ad equate allocation of signals in the processing units)

Modeling easily understandable with respect to the PSA cutsets analysis

I&C architecture accurately represented in the PSA

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Conclusion

Two types of modeling� Graduation of the level of detail

� Adequacy to progress of the project

May have to be supplemented by I&C reliability anal yses (out of the PSA) for justification of assumptions