Information Notice 1992-20, Inadequate Local Leak Rate Testing

Inadequate Local Leak Rate Testing
	ML031200473
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, Three Mile Island, 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
Issue date:	03/03/1992
From:	Rossi C; Office of Nuclear Reactor Regulation
To:	;
References
	IN-92-020, NUDOCS 9202260208
	Download: ML031200473 (9)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 March 3, 1992 NRC INFORMATION NOTICE 92-20: INADEQUATE LOCAL LEAK RATE TESTING

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 problems involving local leak rate testing

(LLRT) of containment penetrations under Part 50 of Title 10 of the

Code of Federal Regulations (10 CFR 50), Appendix J. 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

Quad Cities Station, Unit 1

On February 26, 1991, the Commmonwealth Edison Company (the licensee) performed

a Type B LLRT on the containment penetration bellows for penetration X-25 at

Quad Cities Station, Unit 1, and found an acceptable measured leakage rate of

6 standard cubic feet per hour (scfh). The licensee performed this LLRT by

pressurizing the volume between the two plies of the bellows through a test

connection. On February 28 while performing the primary containment inte- grated leak rate test (ILRT5 under 10 CFR 50, Appendix J, the licensee found

excessive air leakage from the penetration. The licensee recognized the

inconsistencies between the LLRT data for the penetration and the ILRT results

and began a test program to determine the source of the error. Using a blank

flange on the containment side of the bellows, the licensee pressurized the

bellows for a "local ILRT," which yielded a leak rate of 137 scfh. The licensee

also repeated the Type B LLRT with holes drilled in the bellows. This LLRT

result (8 scfh) was only slightly higher than the previous LLRT result. The

results of this test program led the licensee to conclude that it is not

possible to perform a valid Type B LLRT on this type of bellows assembly. The

licensee replaced the bellows for penetration X-25 due to cracks identified by

the tests. Commonwealth Edison is also investigating alternative test methods

that would provide accurate LLRT results for bellows penetration assemblies.

This problem was reported to the NRC under Title 10 of the

Code of Federal Regulations, Part 21 (10 CFR 21).

920226020

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IN 92-20

March 3, 1992 Dresden Nuclear Power Station, Unit 2 On December 17, 1990, the Commonwealth Edison Company (the licensee) found a

leakage rate significantly greater than the maximum allowed during the pressur- ization phase of its ILRT. The licensee identified the source of the leak as

the inboard flange of the torus purge exhaust inner isolation valve with an

estimated leakage rate of approximately 25 weight percent per day at 15 psig.

The licensee had last performed maintenance on this valve during the previous

outage. Although a LLRT had been performed on the valve following the mainte- nance, the test did not challenge the inboard flange.

Perry Nuclear Power Plant, Unit 1 On July 7, 1989, the Cleveland Electric Illuminating Company (the licensee)

discovered a leak through the inboard flange of the seal leakoff line on a

relief valve for the residual heat removal system during the plant's first

periodic ILRT. The licensee had performed maintenance on the valve three times

from 1986 to 1989. In each case, the licensee had performed a LLRT following

the maintenance. However, the LLRT did not challenge the inboard flange.

Clinton Power Station, Unit 1 On December 18, 1990, the Illinois Power Corporation (the licensee) found that

lines from the residual heat removal system relief valves were not-water-sealed

under post-accident conditions as previously indicated in its safety analysis

report. These lines were intended to terminate below the suppression pool

minimum drawdown level, allowing the water to maintain a seal on the contain- ment isolation valves under accident conditions. The problem was first identi- fied when it was discovered that a line, considered to be water-sealed, included a vacuum breaker. The vacuum breaker would open following an acci- dent, bypassing the water seal. The licensee investigated this condition and

found that a number of other lines that empty into the suppression pool either

contained flanges or terminated above the pool minimum drawdown level. Since

these lines would have been open to the containment atmosphere following an

accident, the associated isolation valves should have been tested for leakage

using Type C air tests. To correct this problem, the licensee removed the

vacuum breaker connections and the flanges and extended the pipes to ensure

that a water seal would be maintained.

Discussion

Steel expansion bellows are used on piping penetrations in many plants as part

of the containment isolation scheme. A Type B LLRT is performed on the bellows

periodically to verify that containment integrity is being maintained. The

event at Quad Cities revealed that the LLRT performed between the two plies

could not be used to accurately measure the leakage rate that would occur

through the bellows under accident conditions. The two plies of the bellows

were in contact with each other, restricting the flow of the test medium to the

crack locations. The NRC staff investigated and found that this problem is not

isolated to the bellows manufactured by the vendor involved at Quad Cities.

Any two-ply bellows of similar construction may be susceptible to this problem.

IN 92-20

March 3, 1992 The NRC granted an exemption from the Type B testing requirements of 10 CFR 50,

Appendix J, to Commonwealth Edison for Quad Cities and Dresden on

February 6, 1992. The exemption covers the testing of the two-ply bellows

discussed in this information notice because no valid Type B LLRT can be

performed on these bellows. The exemption specifies an alternative program of

bellows testing and replacement that involves testing with air at a reduced

leakage limit, testing any leaking bellows with helium (sniffer testing),

replacing bellows that are unacceptable, and performing an ILRT each refueling

outage until all of the bellows have been replaced with testable bellows.

The two events involving leaking flanges occurred because the licensees failed

to consider all possible leakage paths when they established their leak rate

test programs. Both licensees identified the valves involved in the events as

containment isolation barriers, but they failed to consider the gasketed

flanges as leakage paths. Both licensees tested the isolation valves in the

reverse direction which did not challenge the flanges properly. Any contain- ment isolation valve could have this problem, particularly if the valve is

tested in the reverse direction or if both valves on a penetration are outside

of containment.

Appendix J to 10 CFR Part 50 requires all licensees to perform local leak rate

testing on containment isolation valves. The licensees for some plants, including Clinton, have received credit from the NRC for maintaining a water

seal on the valves instead of performing local leak rate testing using air as

the test medium. One requirement for a valid water seal is that the pene- tration have no potential air leakage paths, such as flanges or vacuum

breakers. For those lines that depend on the minimum water level in the

suppression pool to prevent leakage, it is expected that the lines terminate

below the minimum suppression pool level in the actual plant configuration.

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.

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts: M. P. Phillips, RIII A. J. Kugler, NRR

(708) 790-5530 (301) 504-2828 F. A. Maura, RIII J. C. Pulsipher, NRR

(708) 790-5696 (301) 504-2811 Attachment: List of Recently Issued NRC Information Notices

2 C

Attachment

mz IN 92-20 /

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rmC

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21 Ca LIST OF RECENTLY ISSUED

NRC INFORHATION NOTICES

< C

I a cog Information Date of

) m Notice No. Subject Issuance Issued to

I

Cn

mO(a

92-19 Misapplication of Potter L 03/02/92 All holders of OLs or CPs

Brumfield MDRRotary Relays for nuclear power reactors.

H0 o 92-18 Potential for Loss of Re- 02/28/92 All holders of OLs or CPs

mote Shutdown Capability

during A Control Room Fire

for nuclear power reactors. (

2

92-17 NRCInspections of Pro- 02/26/92 All holders of OLs or CPs

grams being Developed at for nuclear power reactors.

Nuclear Power Plants in

Response to Generic

Letter 89-10

92-16 Loss of Flow from the 02/25/92 All holders of OLS or CPs

Residual Heat Removal for nuclear power reactors.

Pump during Refueling

Cavity Draindown

92-15 Failure of Primary System 02/24/92 All holders of OLs or CPs

Compression Fitting for nuclear power reactors.

92-14 Uranium Oxide Fires at Fuel 02/21/92 All fuel cycle and uranium

Cycle Facilities fuel research and development

licensees.

92-02, Relap5/Mod3 Computer Code 02/18/92 All holders of OLs or CPs

Supp. I Error Associated with the for nuclear power reactors.

Conservation of Energy

Equation

92-13 Inadequate Control Over

Vehicular Traffic at..

02/18/92 All holders of OLs or CPs

for nuclear power reactors.

(

Nuclear Power Plant Sites

92-12 Effects of Cable Leakage 02/10/92 All holders of OLs or CPs

Currents on Instrument for nuclear power reactors.

Settings and Indications

a O

Operating License

C' Construction Permit

a

B

IN 92-XX

February XX, 1992 The NRC granted an exemption from the Type B testing requirements of 10 CFR 50,

Appendix J, to Commonwealth Edison for Quad Cities and Dresden on

1992.

1 The exemption covers the testing of the two-ply

bellows discussed in this information notice because no valid Type B lLRT can

be performed on these bellows. The exemption specifies an alternative program

of bellows testing and replacement that involves testing with air at a reduced

limit, testing leaking bellows with helium (sniffer testing), replacing bellows

that are unacceptable, and performing an ILRT each refueling outage until all

of the bellows have been replaced with testable bellows.

The two events involving leaking flanges occurred because the licensees failed

to consider all possible leakage paths when they established their leak rate

test programs. Both licensees identified the valves involved in the events as

containment isolation barriers, but they failed to consider the gasketed

flanges as leakage paths. Both licensees tested the isolation valves in the

reverse direction which did not challenge the flanges properly. Any contain- ment isolation valve could have this problem, particularly if the valve is

tested in the reverse direction or if both valves on a penetration are outside

of containment.

All licensees have identified the valves that require Type C testing in accor- dance with Appendix J to Part 50 of Title 10 of the Code of Federal Regula- tions. The licensees for some plants, including Clinton, take credit for

maintaining a water seal on the valves instead of performing a Type C air test.

This is a valid criterion for excluding isolation valves from the Type C

testing requirement only if the lines have no potential leakage paths, such as

flanges or vacuum breakers. Those lines that depend on the minimum water level

in the suppression pool to prevent leakage must terminate below the minimum

suppression pool level in the actual plant configuration.

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.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts: M. P. Phillips, RIII A. J. Kugler, NRR

(708) 790-5530 (301) 492-0834 F. A. Maura, RIII J. C. Pulsipher, NRR

(708) 790-5696 (301) 492-0811 Attachment: List of Recently Issued NRC Information Notices

SEE PREVIOUS CONCURRENCES Document Name: LLRT IN

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-N 91-XX

December XX, 1991 The two events involving leaking flanges occurred because the licensees

failed to consider all possible leakage paths when they established their

leak rate test programs. Both licensees identified the valves involved in

the events as containment isolation barriers, but they failed to consider the

gasketed flanges as leakage paths. Both licensees tested the isolation

valves in the reverse direction which did not challenge the flanges properly.

Any containment isolation valve could have this problem, particularly if the

valve is tested in the reverse direction or if both valves on a penetration

are outside of containment.

All licensees have identified the valves that require Type C testing in

accordance with Appendix J to Part 50 of Title 10 of the Code of Federal

Regulations. The licensees for some plants, including Clinton, take credit

for maintaining a water seal on the valves instead of performing a Type C air

test. This is a valid criterion for excluding isolation valves from the Type

C testing requirement only if the lines have no potential leakage paths, such

as flanges or vacuum breakers. Those lines that depend on the minimum water

level in the suppression pool to prevent leakage must terminate below the

minimum suppression pool level in the actual plant configuration.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contact(s): M. P. Phillips, RIII A. J. Kugler, NRR

(708) 790-5530 (301) 492-0834 F. A. Maura, RIII J. C. Pulsipher, NRR

(708) 790-5696 (301) 492-0811 Attachments:

1. List of Recently Issued NRC Information Notices

SEE ATTACHED PAGES FOR PREVIOUS CONCURRENCES

D/DOEA C/OGCB:DOEA:NRR *RPB:ADM

CERossi CHBerlinger TechEd

12/ /91 12/ /91 12/05/91 OGCB:DOEA:NRR SPLB:DST:NRR SPLB:DST:NRR C/SPLB:DST:NRR D/DST:NRR

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IN 91-XX

December XX, 1991 The two events involving leaking flanges occurred because the licensees

failed to consider all possible leakage paths when they established their

leak rate test program. Both plants identified the valves involved in the

events as containment isolation barriers, but they failed to consider the

gasketed flanges as leakage paths. In both cases, the isolation valves were

tested in the reverse direction such that the flanges were not properly

challenged. This situation could exist for any containment isolation valve, particularly if the valve is tested in the reverse direction or if both

valves on a penetration are outside of containment.

All licensees, either as part of their initial licensing, or in their initial

response to the issuance of 10 CFR Part 50, Appendix J, identified those

isolation valves that required Type C testing. Some plants, including

Clinton, take credit for the maintenance of a water seal on the valves in

lieu of the performance of a Type C air test. This is a valid criterion for

the exclusion of isolation valves from the Type C testing requirement only if

there are no possible leakage paths, such as flanges or vacuum breakers, in

the lines. In addition, for those lines that depend on suppression pool

minimum water level to prevent leakage, it is critical that htese lines

terminate below the minimum suppression pool level in the actual plant

configuration.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate NRR project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contact(s): M. P. Phillips, RIII A. J. Kugler, NRR

(708) 790-5530 (301) 492-0834 F. A. Maura, RIII J. C. Pulsipher, NRR

(708) 790-5696 (301) 492-0811 Attachments:

1. List of Recently Issued NRC Information Notices

D/DOEA C/OGCB:DOEA:NRR RPB:ADM

CERossi CHBerlinger TechEd 5Main 9P\

12/ /91 12/ /91 12/ 5 /91 OGCB:DORA:NRR SPLB:DST:NRR SPLB:DST:NRR C/SPLB:DST:NRR D/DST: NRR

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