Information Notice 1996-06, Design & Testing Deficiencies of Tornado Dampers at Nuclear Power Plants
Nf UNITED STATES NUCLEAR REGULATORY
COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001 January 25, 1996 NRC INFORMATION
NOTICE 96-06: DESIGN AND TESTING DEFICIENCIES
OF TORNADO DAMPERS AT NUCLEAR POWER PLANTS
Addressees
All holders of operating
licenses or construction
permits for nuclear power reactors.
Purpose
The U.S. Nuclear Regulatory
Commission (NRC) is issuing this information
notice to alert addressees
to the potential
for inoperability
of tornado dampers because of either inadequacies
in damper testing or deficiencies
in damper design. 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.Description
of Circumstances
On March 2, 1994, the licensee for South Texas Project, Unit 1, reported a condition
to the NRC that could result in the rapid depressurization
of heating, ventilation
and air conditioning (HVAC) systems and buildings
in the event of a tornado (Licensee
Event Report No.94-003). The licensee discovered
an interference
between the plant exhaust vent tornado damper and a gusset (duct work stru,..turdi
The gusset limited the closing travel of the damper linkage in one damper section to 40 percent of full stroke, thus preventing
the damper from closing completely.
The interference
was discovered
during stroke testing in response to an NRC inspector observation
that there was no testing evidence to show that tornado dampers would actuate as required.
In response to that observation, the licensee initiated
changes to existing preventive
maintenance
work instructions
for all tornado dampers (15 per unit) to include manual stroking on a periodic basis.Only one of the 30 dampers subsequently
tested was found to be inoperable.
The originally
planned periodic maintenance
of tornado dampers at 10-year intervals
did not include any stroke or motion testing.South Texas stated that rapid depressurization
could result in the collapse of the HVAC duct work and could prevent cooling of safety-related
equipment.
The rapid depressurization
could also cause unanalyzed
internal pressure differential
conditions
that might result in damage to safety-related
structures, systems, or components.
PDfJR A _oo o1 6 s 9601190306
&H b l aog3t 21 IN 96-06 January 25, 1996 The licensee revised the preventive
maintenance
program to require preventive
maintenance
on the tornado dampers every 2 years or at each refueling
outage, depending
on the specific damper function.
The 2 year or refueling
outage check includes inspection, cleaning, lubricating, and stroking of the damper while taking dynamometer
measurements
of the spring forces.On October 22, 1993, the licensee for the River Bend Station reported a design condition
to the NRC (Licensee
Event Report No.93-020) that could result in loss of ventilation
to several buildings
after passage of a tornado. The licensee determined
through static pressure testing, that the air-exhaust
dampers for several buildings
would not reopen after passage of a tornado.The failure to reopen results from inadequate
spring force on dampers to overcome exhaust fan shutoff pressure.
This condition
was applicable
to the diesel generator
building, the auxiliary
building, the control building, the fuel building, and the standby cooling tower.The licensee evaluation
at the River Bend Station revealed that the postulated
tornado event could cause loss of offsite power and could prevent the air-intake
dampers for the diesel generator
from reopening.
Other plant areas were less susceptible
to damage because of design features and/or alarms, followed by operator actions that could mitigate the consequences.
The air-exhaust
tornado dampers in the diesel generator
building were modified by blocking them open. The licensee evaluated
the equipment
in the diesel generator
building and concluded
that it would not be affected by depressurization
resulting
from the tornado.The licensee purchase specification
for dampers required the dampers to be capable of automatically
returning
to their normal operating
position (open)after the tornado passed. However, the specification
did not specify the design-bases
conditions
on the inlet side of the exhaust tornado dampers. The static pressure that the damper counterweights
would have to overcome was not specified.
Discussion
Equipment
such as tornado dampers may have been overlooked
in development
of surveillance
testing programs as tornado dampers are not generally
considered
part of the HVAC system in which they are required to function.
Tornado dampers are more likely to be considered
part of the structure
in which they are installed.
Surveillance
tests in the technical
specifications
may involve damper operations
during HVAC systems testing. However, specific NRC requirements
or guidelines
for damper testing in general are limited and do not extend to tornado dampers. Likewise, industry standards
and guidelines
for testing of tornado dampers are also limited. Unlike other active safety-related dampers that are generally
tested along with the HVAC system in which they function, the licensees
considered
tornado dampers as passive devices until they were called upon to perform their function.
'wO IN 96-06 January 25, 1996 When called on, certain dampers must close to prevent rapid depressurization
within the structures
and HVAC ductwork and then reopen after the tornado passes. In cases for which no redundancy
exists, a single failure of a tornado damper to perform its safety function could result in a loss of safety system function.
Therclore, absence of appropriate
surveillance
testing for tornado dampers could lead to multiple failures in safety systems.This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice, please contact one of the technical
contacts listed below or the appropriate
Office of Nuclear Reactor Regulation (NRR) project manager.4ennr .C r u t Coto d rector Division of Reactor rogram Management
Office of Nuclear Reactor Regulation
Technical
contacts:
William T. LeFave, NRR (301) 415-3285 Internet:wtllenrc.gov
Thomas Koshy, NRR (301) 415-1176 Internet:txk@nrc.gov
Attachment:
List of Recently Issued NRC Information
Notices tr -;1
\ E Attachment
IN 96-06 January 25, 1996 LIST OF RECENTLY ISSUED NRC INFORMATION
NOTICES Information
Date of Notice No. Subject Issuance Issued to 96-05 96-04 96-03 Partial Bypass of Shutdown Cooling Flow from the Reactor Vessel Incident Reporting
Require-ments for Radiography
Licensees Main Steam Safety Valve Setpoint Variation
as a Result of Thermal Effects 01/18/96 01/10/96 01/05/96 All holders of OLs or LPs for boiling water reactors All radiography
licensees and manufacturers
of radio-graphy equipment All holders of OLs or CPs for nuclear power reactors 96-02 Inoperability
of Power-Operated Relief Valves Masked by Downstream
Indications
During Testing 01/05/96 All holders for PWRs of OLs or CPs 96-01 95-58 95-57 Potential
for High Post-Accident Closed-Cycle
Cooling Water Temperatures
to Disable Equipment Important
to Safety 10 CFR 34.20; Final Effective
Date Risk Impact Study Regarding Maintenance
During Low-Power Operation
and Shutdown 01/03/96 12/18/95 12/18/95 All holders of OLs or CPs for PWRs Industrial
Radiography
Licensees All holders of OLs or CPs for nuclear power reactors.OL -Operating
License CP -Construction
Permit
IN 96-06 January 25, 1996 When called on, certain dampers must close to prevent rapid depressurization
within the structures
and HVAC ductwork and then reopen after the tornado passes. In cases for which no redundancy
exists, a single failure of a tornado damper to perform its safety function could result in a loss of safety system function.
Therefore, absence of appropriate
surveillance
testing for tornado dampers could lead to multiple failures in safety systems.This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice, please contact one of the technical
contacts listed below or the appropriate
Office of Nuclear Reactor Regulation (NRR) project manager.original signed by Dennis M. Crutchfield, Director Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical
contacts:
William T. LeFave, NRR (301) 415-3285 Internet:wtl1@nrc.gov
Thomas Koshy, NRR (301) 415-1176 Internet:txk@nrc.gov
Attachment:
List of Recently Issued NRC Information
Notices Tech Editor Reviewed 10/05/95 DOCUMENT NAME: 96-06.IN *SEE PREVIOUS CONCURRENCES
To receive a copy of this document, hIdicate In the box: wC" -Copy without enclosures
'E' -Copy with enclosures "N" -No copy OFFICE SPLB/DSSA
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I DATE 10/11/95 01/04/96 01/17/96 01/9/96 01/ /96 OFFICIAL RECORD COPY
IN 96-xx January xx, 1996 They must then close to prevent rapid depressurization
within the structures
and HVAC ductwork and then reopen after the tornado passes. In cases for which no redundancy
exists, a single failure of a tornado damper to perform its safety function could result in a loss of safety system function.Therefore, absence of appropriate
surveillance
testing for tornado dampers could lead to multiple failures in safety systems.This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice, please contact one of the technical
contacts listed below or the appropriate
Office of Nuclear Reactor Regulation (NRR) project manager.Dennis M. Crutchfield, Director Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical
contacts:
William T. LeFave, NRR (301) 415-3285 Internet:
wtl1@nrc.gov
Thomas Koshy, NRR (301) 415-1176 Internet:
txk@nrc.gov
Attachment:
List of Recently Issued NRC Information
Notices DOCUMENT NAME: G:\IN\IN-DAMP
OFFICE 1SPLB/DSSA
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OFFICIAL RECORD COPY
I i;IN 96-xx January xx, 1996 They must then close to prevent rapid depressurization
within the structures
and HVAC ductwork and then reopen after the tornado passes. In cases for which no redundancy
exists, a single failure of a tornado damper to perform its safety function could result in a loss of safety system function.Therefore, absence of appropriate
surveillance
testing for tornado dampe could lead to multiple failures in safety systems.This information
notice requires no specific action or written r onse. If you have any questions
about the information
in this notice, p ase contact one of the technical
contacts listed below or the appropria
Office of Nuclear Reactor Regulation (NRR) project manager.Dennis M. Cr c hfield, Director Division of eactor Program Management
Office of uclear Reactor Regulation
Technical
contacts:
William T. LeFave, RR (301) 415-3285 Thomas Koshy, R (301) 415-117 Attachment:
List of Recently Issued NRC Info ation Notices N NAME: G:\IN\IN-DAMP
/nnri imrm S.wxua^u .OFFICE SPLB/DSSA
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DATE 11/29/95 4 10/12A5 5 01/ /96 01/ /96* See previous G currence OFFICIAL RECORD COPY
IN 95-xx December xx, 1995 They must then close to prevent rapid depressurization
within the structures
and HVAC ductwork and then reopen after the tornado passes. In cases for which no redundancy
exists, a single failure of a tornado damper to perform its safety function could result in a loss of safety system function.Therefore, absence of appropriate
surveillance
testing for tornado dampers could lead to multiple failures in safety systems.This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice, please contact one of the technical
contacts listed below or the appropriate
Office of Nuclear Reactor Regulation (NRR) project manager.Dennis M. Crutchfield, Director Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical
contacts:
William T. LeFave, NRR (301) 415-3285 Thomas Koshy, NRR (301)415-1176 Attachments:
1. Referenced
Codes and Standards 2 2. List of Recently Issued NRC Information
Notices DOCUMENT NAME: G:\IN\IN-DAMP
OFFICE SPLB/DSSA
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- DATE 10/11/95 110/11/95
10/05/95 10/12/95 / /95 OFFICE .EBDRML SOCB/OPSIE
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Rbe ssel AChaffee DCrutchfield
DATE 11/29/95 ' 10/12/95 / 1 / /95 / /95* See previous Concurrence
I OFFICIAL RECORD COPY zmy-2 See Exhibit 24 for the format to be used when codes or standards
are referenced
in the information
notice.
IN 95-xx December xx, 1995 depressurization
within the structures
and HVAC ductwork and then reopen after the tornado passes. In cases which no redundancy
exists, a single failure of a tornado damper to perform its safety function could result in a loss of safety system function.
Therefore, absence of appropriate
surveillance
testing for tornado dampers could lead to multiple failures in safety systems.This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice, please contact one of the technical
contacts listed below or the appropriate
Office of Nuclear Reactor Regulation (NRR) project manager.Dennis M. Crutchfield, Director Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical
contacts: William T. LeFave, NRR (301) 415-3285 Thomas Koshy, (301)415-1176 NRR Attachments:
1. Referenced
Codes and Standards 2 2. List of Recently Issued NRC Information
Notices DOCUMENT NAME: G:\IN\IN-DAMP
OFFICE jSPLB/DSSA
I E SC:SPLB/DSSA
I N ADM:PUB* I N BC:SPLB/DSSA
I C RIV/DRS I N NAME WTLeFave*
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- DATE 10/11/95 10/11/95 10/05/95 10/12/95 I /95-__ _ __ .-I _ ,21. I. pfi a Ip I I.I nFFTrF DFrR/nfPM
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DATE 11/29/95 I10/12/95
/ /95 \ / /95 5 I / /95_* See previous Concurrence
C)FFICIAL RECORD COPY 2 See Exhibit 24 for the format to be used when codes or standards
are referenced
in the information
notice.
I ..i-A -a -.1-IN 95-xx October xx, 1995 depressurization
within the structures
and HVAC ductwork and then reopen after the tornado passes. In cases which no redundancy
exists, a single failure of a tornado damper to perform its safety function could result in a loss of safety system function.
Therefore, absence of appropriate
surveillance
testing for tornado dampers could lead to multiple failures in safety systems.This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice, please contact one of the technical
contacts listed below or the appropriate
Office of Nuclear Reactor Regulation (NRR) project manager.Dennis M. Crutchfield, Director Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical
contacts: William T. LeFave, NRR (301) 415-3285 Thomas Koshy, NRR (301)415-1176 Attachments:
1. Referenced
Codes and Standards 2 2. List of Recently Issued NRC Information
Notices OFFICE SPLB/DSSA
E SC:SPLB/DSSA
I N ADM:PUB* I N BC:SPLB/DSSA
I C RIV/DRS I N NAME jWTLeFave*
GHubbard
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- DATE 110/11/95
10/11/95 10/05/95 10/12/95 I /95I_--_ -- _ _ Ac _ _- Am- __- _ Ac ._- A m Am __ m _-- A 9 11 OFFICE PECB/DRPM-I
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lDATE nI29i 95 10/12/95 11&& L /91S I / /95 4%, I / /95* See previous Concurrence
OFFICIAL RECORD COPY 2 See Exhibit 24 for the format to be used when codes or standards
are referenced
in the information
notice.