Determining Resilience Thresholds for Nuclear Power Plants

DETERMINING RESILIENCE
THRESHOLDS FOR NUCLEAR POWER
PLANTS
Pamela Fran Nelson
UNAM
27 abril 2015
Objective

Develop
a
robust
tool
for
monitoring
organizational resilience.

Implement the tool at a nuclear power plant to
measure and follow human performance events
including organizational performance.

Track trends in order to identify time periods
where
the
likelihood
of
consequential events increases.
occurrence
of
Scope
Human and Organizational Errors
Pre-initiators
Maintenance
Post-initiators
Preventive
Corrective
Calibration
Operations
Surveillance
Normal
Off-Normal
Typical organization process flow of
work activities at an NPP.
Corrective Action Program
(CAP)
Low level CAP (“Soft” and “hard”)
High level CAP
10,000 – 15,000 per year
Condition Reports
SCAQ
Significant Condition Adverse to Quality (includes
LERs)
CAQ-L1
Condition Adverse to Quality at a station
level
CAQ-L2
Condition Adverse to Quality at a department
level
CNAQ
Condition Not Adverse to Quality
Events per week
Tool: Probability of an SCAQ
depending on the number of days
since the last occurrence
Tool: Probability of an SCAQ
depending on the number of CRs
since the last occurrence
Organizational factors

Responsible
organizations or
departments

CRs

Actions

Interdepartmental
factors

Actions generated for
other departments

Communications
between departments
Interdepartmental factors
Departments creating CRs
Departments receiving actions
Number of SCAQs for departments
responsible for more than one SCAQ.
Number of actions from SCAQs
Resilience Scheme
Compensatory
measure
Materials Science Analogy:
Stress-Strain Curve
Resilience curve and threshold
Resilience curves per year
Conceptual Performance Indicator
Time series: 2005-2015
Forecasting
Summary
 A proposed leading performance indicator was developed to predict
increased likelihoods of consequential events
 Organizational resilience can be modeled based on a stress-strain
analogy
 Data represents actual plant events and operating history for
consequential events
 Plant to plant variability would be expected and plant specific analysis is
needed to determine resilience thresholds
 Additional work is needed to collect more data to determine the level of
robustness of the approach and to begin developing organization
specific consequential events and associated organizational specific
thresholds
Distribution fitting