Information Notice 1993-35, Insights from Common-Cause Failure Events
II
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
May 12, 1993
INSIGHTS FROM COMMON-CAUSE FAILURE EVENTS
Addressees
All holders of operating licenses or construction permits for nuclear power
plants (NPPs).
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to inform addressees about the publication of an NRC report on common- mode and common-cause failure events that could occur at nuclear power plants.
It is expected that recipients will review the information for applicability
to their facilities and consider actions, as appropriate, to avoid similar
problems. However, suggestions contained In this information notice are not
NRC requirements; therefore, no specific action or written response is
required.
Discussion
The Office for Analysis and Evaluation of Operational Data (AEOD) published a
report, 'Insights from Common-Mode Failure Events," AEOD/E92-02, in June 1992 and issued Supplement 1 in February 1993.* The staff reviewed 62 selected
licensee event reports that discussed actual or potential common-cause
failures. Of the 62 events reviewed, 16 also were identified as precursors in
the accident sequence precursor program (ASP). Common-cause failures may
significantly degrade safety since they can defeat the additional benefit
normally provided by redundant systems. Furthermore, common-cause failure has
been cited as a major uncertainty in probabilistic risk assessments of nuclear
power plants.
Most of the reports used in the AEOD study were prompted by events that
occurred in 1990. In the study, the staff used reports of events where the
failed equipment was considered neither 'recoverable' nor .self-revealing.' A
failure that is recoverable is one in which the plant condition could be
restored by taking a corrective action during the event. However, failure in
a location inaccessible during an accident, such as inside the containment; a
failure of equipment needed for a rapidly developing event such as a loss-of- coolant accident; a challenge to pressure vessel integrity; or a backwards
installation of a necessary valve are considered failures that are not
recoverable. For a self-revealing condition, the licensee would presumably
- Coples of this report and its supplement are available for inspection
and copying in the NRC Public Document Room, 2120 L Street N.W.,
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May 12, 1993 correct the situation before the event occurred that required the equipment.
The staff excluded such conditions from this study.
The AEOD report attempted to identify the actions that would be most effective
in precluding or reducing the likelihood of common-cause failures at operating
nuclear power plants.
Each of the events was reviewed against a set of eight
potential actions:
comprehensive testing, staggered testing, post-maintenance
testing, using equipment from different manufacturers in redundant trains
(diverse equipment), using equipment with larger design margin, increasing
frequency of testing, providing adequate separation of trains, and using
different maintenance personnel'on separate trains.
No single action would
have alleviated all the common-cause failures in the study.
Considering all
the events, the action that had the highest potential benefit was using
equipment with larger design margins. This action alone would have corrected
about 56 percent of the situations examined in the AEOD study. Performing
comprehensive systems tests, ensuring adequate train separation, and using
diverse equipment each had a potential benefit in about 27 percent of the
cases. The use of staggered surveillance testing would have benefited
20 percent of the events.
The staff noted that about two-thirds of the events were related to design, fabrication, and installation errors that may be undetected for long periods
of time. The remaining events were associated with maintenance deficiencies, either preventive or corrective. The major alleviating action identified for
these maintenance-related events was staggered survelillance-testing, iwhich- is- assumed to result in a shorter time during which the common-mode failure is
undetected.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please call one
of the technical contacts listed below or the appropriate Office of Nuclear
Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact: S. Israel, AEOD
(301) 492-4437 Attachment:
List of Recently Issued NRC Information Notices
-4
Attachment
May 12, 1993 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
93-34, Supp. 1
93-34
93-33
93-32
Potential for Loss of
Emergency Cooling
Function Due to A
Combination of
Operational and Post- Loca Debris in Contain- ment
Potential for Loss of
Emergency Cooling
Function Due to A
Combination of
Operational and Post- Loca Debris in Contain- ment
Potential Deficiency
of Certain Class IE
Instrumentation and
Control Cables
Nonconservative Inputs
for Boron Dilution
Event Analysis
X Training of Nurses
Responsible for the
Care of Patients with
Brachytherapy Implants
NRC Requirements for
Evaluation of Wipe
Test Results; Cali- bration of Count Rate
Survey Instruments
Problems with the Use
of Unshielded Test Leads
in Reactor Protection
System Circuitry
04/06/93
04/26/93
04/28/93
04/21/93
04/13/93
04/12/93
04/12/93
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for pressurized water
reactors (PWRs).
All U.S. Nuclear Regulatory
Commission medical
licensees.
All U.S. Nuclear Regulatory
Commission medical
licensees.
All holders of OLs or CPs
for nuclear power reactors.
93-30
93-29 OL -'Operating License
CP = Construction Permit
tj
V IN 93-35 May 12, 1993 correct the situation before the event occurred that required the equipment.
The staff excluded such conditions from this study.
The AEOD report attempted to identify the actions that would be most effective
in precluding or reducing the likelihood of common-cause failures at operating
nuclear power plants.
Each of the events was reviewed against a set of eight
potential actions: comprehensive testing, staggered testing, post-maintenance
testing, using equipment from different manufacturers in redundant trains
(diverse equipment), using equipment with larger design margin, increasing
frequency of testing, providing adequate separation of trains, and using
different maintenance personnel on separate trains. No single action would
have alleviated all the common-cause failures in the study. Considering all
the events, the action that had the highest potential benefit was using
equipment with larger design margins. This action alone would have corrected
about 56 percent of the situations examined in the AEOD study.
Performing
comprehensive systems tests, ensuring adequate train separation,/ and using
diverse equipment each had a potential benefit in about 27 percent of the
cases.
The use of staggered surveillance testing would have benefited
20 percent of the events.
The staff noted that about two-thirds of the events were related to design, fabrication, and installation errors that may be undetected for long periods
of time. The remaining events were associated with maintenance deficiencies, either preventive or corrective. The major alleviating action identified for
these maintenance-related events was staggered surveillance testing, which is
assumed to result in a shorter time during which the common-mode failure is
undetected.
This information notice requires
you have any questions about the
of the technical contacts listed
Reactor Regulation (NRR) project
no specific action or written response. If
information in this notice, please call one
below or the appropriate Office of Nuclear
manager.
Original sIgned Uy
Brian K.
Grimeg
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact:
S. Israel, AEOD
(301) 492-4437 Attachment:
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OGCB:DORS:NRR
- TECH ED
- ROAB:AEOD
CVHodge
RSanders
03/
/93
03/11/93
03/11/93
- C:OGCB:DORS:NRR
GHMarcus
( Sii~
03/31/93
05/X /93
- C:ROAB:AEOD
JERosenthal
03/19/93
- D:DSSA:NRR
ACThadani
03/24/93 DOCUMENT NAME: 93-35.IN
IN 93- May
, 1993 presumably correct the situation before the event occurred that required the
equipment. The staff excluded such events from this study.
The AEOD report attempted to identify the actions that would be most effective
in precluding or reducing the likelihood of common-cause failures at operating
nuclear power plants. Each of the events was reviewed against a set of eight
potential actions: comprehensive testing, staggered testing, post-maintenance
testing, using equipment from different manufacturers in redundant trains
(diverse equipment), using equipment with larger design margin, increasing
frequency of testing, providing adequate separation of trains, and using
different maintenance personnel on separate trains.
No single action would
have alleviated all the common-cause failures in the study.
Considering all
the events, the action that had the highest potential benefit was using
equipment with larger design margins. This action alone corrected about
56 percent of the situations examined in the AEOD study.
Performing
comprehensive systems tests, ensuring adequate train separation, and using
diverse equipment each had a potential benefit in about 27 percent of the
cases.
The use of staggered surveillance testing would have benefited
20 percent of the events.
The staff noted that about two-thirds of the events were related to design, fabrication, and installation errors that may be undetected for long periods
of time.
The remaining events were associated with maintenance deficiencies, either preventive or corrective.
The major alleviating action identified for
these maintenance-related events was staggered surveillance testing, which is
assumed to result in a shorter time during which the common-mode failure is
undetected.
This information notice requires no specific action or written response.
If
you have any questions about the information in this notice, please call one
of the technical contacts listed below or the appropriate Office of Nuclear
Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact: S. Israel, AEOD
(301) 492-4437 Attachment: List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OGCB:DORS:NRR
- TECH ED
- ROAB:AEOD *C:ROAB:AEOD
- D:DSSA:NRR
CVHodge
RSanders
JERosenthal
ACThadani
03/
/93
03/11/93
03/11/93
03/19/93
03/24/93 C:OGCB:DORS:NRR
D:DORS:NRR
GHMarcus
BKGrimes
03/31/93
03/ /93 DOCUMENT NAME: COMMMOD3.INF
IN 93- March
, 1993 the licensee would presumably correct the situation before the event occurred
that required the equipment. The staff excluded such events from this study.
The AEOD report attempted to identify the actions that would be most effective
in precluding or reducing the likelihood of common-cause failures at operating
nuclear power plants. Each of the events was reviewed against a set of eight
potential actions: comprehensive testing, staggered testing, post maintenance
testing, using equipment from different manufacturers in redundant trains
(diverse equipment), using equipment with larger design margin, increasing
frequency of testing, providing adequate separation of trains, and using
different maintenance personnel on separate trains.
No single action would
have alleviated all the common-cause failures in the study.
Considering all
the events, the action that had the highest potential benefit was using
equipment with larger design margins. This action alone corrected about 56 percent of the situations examined in the AEOD study.
Performing
comprehensive systems tests, ensuring adequate train separation, and using
diverse equipment each had a potential benefit in about 27 percent of the
cases. The use of staggered surveillance testing would have benefited 20
percent of the events.
The staff noted that about two-thirds of the events were related to design, fabrication, and installation errors that may be undetected for long periods
of time. The remaining events were associated with maintenance deficiencies, either preventive or corrective. The major alleviating action identified for
these maintenance-related events was staggered surveillance testing, which is
assumed to result in a shorter time during which the common made failure is
undetected.
This information notice requires no specific action or written response.
If
you have any questions about the information in this notice, please call one
of the technical contacts listed below or the appropriate Office of Nuclear
Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact: S. Israel, AEOD
(301) 492-4437 Attachment:
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OGCB:DORS:NRR
- TECH ED
- ROAB:AEOD *C:ROAB:AEOD
- D:DSSA:NRR
CY}odge:mkm
RSanders
JERosenthal
ACThadani
&//03/93
03/11/93
03/11/93
03/19/93
03/24/93 C:OGCB:DORS:NRR
D:DORS:NRR
GHMarcus
BKGrimes
03/31/93
03/ /93 DOCUMENT NAME:
COMMMOD3.INF
IN 93- March
, 1993 the licensee would presumably correct the situation before the event occurred
that required the equipment. The staff excluded such events from this study.
The AEOD report was prepared to identify the corrective actions that would be
most effective in precluding or reducing the likelihood of common-cause
failures at operating nuclear power plants. Each of the events was reviewed
against a set of eight corrective actions.
No single corrective action can
minimize all the potential causes of common-cause failures. Considering all
the events, the corrective action that had the highest potential impact was
using equipment with larger design margins. This action alone corrected about
56 percent of the situations examined in the AEOD study.
Performing
comprehensive systems tests, ensuring adequate train separation, and using
diverse equipment each had a potential impact on about 27 percent of the
cases. The use of staggered surveillance testing impacted 20 percent of the
events.
The staff noted that about two-thirds of the events were related to design, fabrication, and installation errors that may be undetected for long periods
of time. The AEOD study also showed that the major corrective action for
these situations was using equipment with larger design margins. The
remaining one-third of the events was associated with maintenance
deficiencies, either preventive or corrective. The major corrective action
for these maintenance- related events was staggered surveillance testing.
This information notice requires
you have any questions about the
of the technical contacts listed
Reactor Regulation (NRR) project
no specific action or written response. If
information in this notice, please call one
below or the appropriate Office of Nuclear
manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact:
S. Israel, AEOD
(301) 492-4437 Attachment: List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OGCB:DORS:NRR D*TECH ED
- ROAB:AEOD
CVHodge:mkm 4 RSanders
03/31/93
03/11/93
03/11/93
- C:ROAB:AEOD
JERosenthal
03/19/93
- D:DSSA:NRR
ACThadani
03/24/93 C:OGCB:DORS:NRR
GHMarcus U
03/D
C M/9ENT
DOCUMENT NAME:
D:DORS:NRR
BKGrimesok
03/
/93IN
COMMMOD3.INF
v>
IN 93- March
, 1993 cause a failure event, the licensee
before the failure event occurred.
study.
would presumably correct the situation
The staff excluded such events from this
The AEOD report was prepared in order to identify dominant corrective actions
that would preclude or reduce the likelihood of common-cause failures at
operating nuclear power plants. Each of the events was reviewed against a set
of eight corrective actions. No single corrective action can minimize all the
potential causes of common-cause failures. Considering all the events, the
corrective action that had the highest potential impact was using equipment
with larger design margins, this action alone corrected about 56 percent of
the situations examined in the AEOD study.
Performing comprehensive systems
tests, ensuring adequate train separation, and using diverse equipment each
had a potential impact on about 27 percent of the cases. The use of staggered
surveillance testing impacted 20 percent of the events.
The staff noted that about two-thirds of the events were related to design, fabrication, and installation errors that go undetected for long periods of
time. The AEOD study showed that the major corrective action for these
situations was using equipment with larger design margins. The remaining one- third of the events was associated with maintenance deficiencies, either
preventive or corrective. The major corrective action for these maintenance- related events was staggered surveillance testing.
This information notice requires
you have any questions about the
of the technical contacts listed
Reactor Regulation (NRR) project
no specific action or written response. If
information in this notice, please call one
below or the appropriate Office of Nuclear
manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact: S. Israel, AEOD
(301) 492-4437 Attachment: List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCEC&A OA
c
ve
OGCB:DORS:NRRn
- TECH ED
ROAB:AfBDA C:ROAB:AEOgf&h
CVHo ge:mkm6RK
RSanders
JERosenthal
03//D/93
03/11/93
03/11/93
03/19/93 D:DSSA:NRR
ACThadani
03 VI/93 C:OGCB:DORS:NRR
GHMarcus
03/ /93 DOCUMENT NAME:
D:DORS:NRR
BKGrimes
03/ /93
COMMMOD3.INF
-1 Technical Contacts:
S. Israel, AEOD
(301)492-4437 Attachment: List of Recently Issued NRC Information Notices
OGCB:DORS:NRR
CVHodge:mkm
03/ /93 TECH ED
03/ 1l/93 ROAB:AEOD
03/ /93 C:ROAB:AEOD
JERosenthal
03/ /93 D:DSSA:NRR
ACThadani
03/ /93 CM:UOFS:NM
GHMarcus
03/ /93 D:DORS:NRR
BKGrimes
03/
/93