Jin Jiang

1
Jin Jiang Sungwhan Cho Department of
Electrical and Computer EngineeringThe
University of Western Ontario,London, Ontario,
N6A 5B9, Canadajjiang_at_eng.uwo.ca
Analysis and Optimization of Surveillance Test
Interval for k-out-of-n Safety Systems with
Applications to SDS1 in CANDU Reactors
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Outline of the Presentation
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CANDU Plant Overview
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Shutdown System 1(SDS1)
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Surveillance Test Effect on Reliability and
Spurious Trip

• Ten Trip Parameters
• High Regional Neutron Power
• Rate Log High Neutron Power
• Heat Transport System High pressure
• Primary Heat Transport Low Flow
• Reactor Building High Pressure
• Pressurizer Low Level
• Steam Generator Low Level
• Moderator High Temperature
• Heat Transport Low Pressure
• SG Feed line Low Pressure

The required unavailability should be less than
10-3 years/year 8.76 hours/year
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3-channel Systems

• Increase Reliability
• Enable On-line Test

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Surveillance Tests

• Benefits of Surveillance Tests
• Increase Overall Reliability

-Recovery
-Detection of Hidden Failure
Test Interval
-Degradation -Wear Out
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Surveillance Tests

• Shortcomings of Surveillance Tests
• Increase Spurious Trip Probability
• Human Resource
• Wear out to System Components

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Methods for Determination of the
Surveillance Test Intervals

• Target Reliability
• - Guides, regulations
• Reliability Analysis Techniques
• - Classical fault tree
• - Dynamic fault tree
• - Markov process models
• Determination of the surveillance test interval
• - Reliability
• - Human resource requirement
• - Cost, wear out
• - Spurious trip probability

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Issues in Determining the Test Intervals

• Test Duration and Recovery Time
• Ignored in classical fault tree models
• Models for Quantifying the Unavailability
• Classical fault tree
• - Describe binary state
• - Cannot model configuration changes
• Dynamic fault tree
• - Configuration changes can be incorporated
• Markov process models
• - Capability of modeling multi-states
• - Mathematical complexity

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State Space Model

• Step 1 Grouping States
• Step 2 Assigning State Transition Rates

- ?f Failure Rate - µTF Test Transition Rate -
µTD Recovery Rate
µTF
?f
µTF
SD Desirable State
SF Undetected Failure State
ST Test State
µTD
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Modeling of states in SDS1
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Probability of normal operation
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Quantification of Risk from Surveillance Test
Performing Surveillance Tests
Decrease Channel Unavailability
Increase Spurious Trip Probability
Quantification of Effect on Core Damage
Probability
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Failure Scenario
Class IV Failure
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CDP with Class IV Power Failure
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Conclusions

• State space models using Markov process
  technique are successfully developed for
  determination of the optimal test frequency
  for redundant emergency shutdown systems.
• The states of a system can be decomposed to (a)
  the desired, (b) the failed, and (c) the test.
• The optimal surveillance test frequency is a
  function of the component failure rates and
  the test duration.
• Progress is underway to study the state
  dependence for common cause failures.

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• THANK YOU!