Information Notice 1996-06, Design & Testing Deficiencies of Tornado Dampers at Nuclear Power Plants

Design & Testing Deficiencies of Tornado Dampers at Nuclear Power Plants

ML031060290
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Crane
Issue date:	01/25/1996
From:	Crutchfield D Office of Nuclear Reactor Regulation
To:
References
IN-96-006, NUDOCS 9601190306
Download: ML031060290 (10)

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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

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 stiffener).

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.

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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.

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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

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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

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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

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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

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Dennis M. Cr c

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William T. LeFave, RR

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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 Standards2

2. List of Recently Issued NRC Information Notices

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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

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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 Standards2

2. List of Recently Issued NRC Information Notices

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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 Standards2

2. List of Recently Issued NRC Information Notices

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