Information Notice 1992-20, Inadequate Local Leak Rate Testing
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555
March 3, 1992
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).
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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.
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
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March 3, 1992
Page 1 of I
LIST OF RECENTLY ISSUED
NRC INFORHATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
92-19 Misapplication of Potter L
03/02/92
All holders of OLs or CPs
Brumfield MDR Rotary Relays
for nuclear power reactors.
92-18 Potential for Loss of Re-
02/28/92
All holders of OLs or CPs
mote Shutdown Capability
for nuclear power reactors.
during A Control Room Fire
92-17 NRC Inspections 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
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
02/18/92
All holders of OLs or CPs
Vehicular Traffic at..
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
O
- Operating License
C '
Construction Permit
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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
1 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
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
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 contact one
below or the appropriate Office of Nuclear
manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical contacts:
M. P.
(708)
Phillips, RIII
790-5530
A. J. Kugler, NRR
(301) 492-0834
F. A. Maura, RIII
(708) 790-5696
J. C. Pulsipher, NRR
(301) 492-0811 Attachment: List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCES
Document Name: LLRT IN
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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
(708) 790-5530
A. J. Kugler, NRR
(301) 492-0834 F. A.
(708)
Maura, RIII
790-5696 J. C.
(301)
Pulsipher, NRR
492-0811 Attachments:
1. List of Recently Issued NRC Information Notices
- SEE ATTACHED PAGES FOR PREVIOUS CONCURRENCES
D/DOEA
C/OGCB:DOEA:NRR
CERossi
CHBerlinger
12/
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12/
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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
(708) 790-5530
A. J. Kugler, NRR
(301) 492-0834
F. A. Maura, RIII
(708) 790-5696
J. C. Pulsipher, NRR
(301) 492-0811 Attachments:
1. List of Recently Issued NRC Information Notices
OGCB:DORA:NRR
AJKugler
12/
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MPPhillips
12/
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12/
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12/
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12/
/91 C/OGCB:DOEA:NRR
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12/
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12/
/91 RIII
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12/
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12/ 5 /91 D/DST: NRR
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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.
Original Signed by
Charles E. Rossi, Director
Charles E.
Rossi
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical contacts:
M. P.
(708)
Phillips, RIII
790-5530
A. J.
(301)
Kugler, NRR
504-2828
F. A. Maura, RIII
(708) 790-5696
J. C. Pulsipher, NRR
(301) 504-2811 Attachment: List of Recently Issued NRC Information Notices
- SEE PRFY1OJ4 CONCURRENCES
D/99E~lX~
- C/OG BDOEA:NRR*RPB:ADM
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CHBerlinger
TechEd
MPPhillips
02/20/92
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AJKugler
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12/09/91
01/30/92
02/05/92 DOCUMENT NAME: IN 92-20
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12/17/91
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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
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
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.
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
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 contact one
below or the appropriate Office of Nuclear
manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical contacts:
M. P. Phillips, RIII
(708) 790-5530
A. J. Kugler, NRR
(301) 504-2828
F. A. Maura, RIII
(708) 790-5696 J. C.
(301)
Pulsipher, NRR
504-2811 Attachment: List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCES
Document Name: LLRT IN
D/DOEA:NRR
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12/09/91
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12/17/91
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12/17/91