Information Notice 1997-74, Inadequate Oversight of Contractors During Sealant Injection Activities
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UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
September 24, 1997
NRC INFORMATION NOTICE 97-74: INADEQUATE OVERSIGHT OF CONTRACTORS
DURING SEALANT INJECTION ACTIVITIES
Addressees
All holders of operating licenses for nuclear power reactors except those who have
permanently ceased operations and have certified that fuel has been permanently removed
from the reactor vessel.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert
addressees to the consequences of inadequate oversight of contractors during sealant
injection activities. It is expected that recipients will review the information for applicability to
their facilities and consider actions, as appropriate, to avoid similar problems. Suggestions
contained in this information notice are not NRC requirements; therefore, no specific action or
written response is required.
Description of Circumstances
Beaver Valley
The head vent system (HVS) at Beaver Valley Unit 2 removes noncondensable gases from
the reactor vessel head and is designed to mitigate the consequences of inadequate core
cooling or impaired natural circulation resulting from the accumulation of noncondensable
gases in the reactor coolant system (RCS).
In November 1996, with Unit 2 in Mode 5 (cold shutdown) near the end of an extended
refueling outage, operators noted a leak at a blind flange downstream of a normally shut
1-inch flow-gauge isolation valve located in a dead-leg portion of the HVS. The leak
measured approximately 15 drops per minute. On December 2, 1996, sealant was injected
into an upstream valve to temporarily stop the leakage. Following the sealant injection, the
reactor was restarted on December 3, 1996. Subsequently, as a result of concerns raised by
the NRC regarding the leaktightness of several valves upstream of the valve where sealant
was injected, Unit 2 was shut down and the valves were tested for leaks. During this post- maintenance testing, it was discovered that some sealant had migrated to other portions of
the HVS, clogging two HVS flow control valves and causing one of these valves to become
bound and unable to fully stroke.
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IN 97-74 September 24, 1997 As a result of this event, the plant manager issued a stop-work order and also ordered (1) a
review of the leak repair process at the plant, (2) a check of all existing leak repairs, and (3)
a review of vendor oversight practices.
Several factors contributed to the event at Beaver Valley Unit 2:
(1)
Licensee engineering provided improper information to the vendor performing the
repair. Engineering specified normal RCS operating pressure and temperature
conditions (610°F and 2235 psia) to the vendor instead of the actual conditions under
which the repair would be made (close to ambient). As a result, the wrong sealant
material was used.
(2)
The licensee did not review vendor procedures adequately and did not exercise
sufficient monitoring and control of vendor activities. Specifically, there was no
monitoring of the quantity of sealant injected, the injection pressure of the sealant, or
the location of the injection port.
(3)
Significant weaknesses were found in work instructions, quality assurance and quality
control involvement, sealant material selection, injection port location, and direct
vendor oversight. Work instructions, prebriefings, and overall vendor oversight were
inadequate.
As a result of inadequate licensee control of the injection of sealant material into the HVS at
Unit 2, twice as much sealant was injected into the valve as was specified in the
maintenance work package. The sealant failed to harden properly, migrated to unintended
portions of the HVS, and degraded the HVS flow control valves when it accumulated on the
valve seats. One of the valves became bound and was unable to fully stroke. Because the
valves were inoperable, the HVS would. not have been able to perform its gas-removal
function".
LaSalle
On June 19, 1996, with both units operating at 100 percent power, nonessential service water
(SW) system discharge pressures began to decrease because of the high differential pres- sures across the in-line strainers. The operators backwashed the strainers, restoring
the normal discharge pressures. On June 24, 1996, the problem recurred, causing high
temperature in a diesel fire pump during routine surveillance testing.
The licensee's root cause determination following the initial event focused on material
generated from sandblasting performed on the exterior of the lake screenhouse. The
licensee initially believed that some of the sandblasting material had become entrained in the
IN 97-74 September 24, 1997 SW, fouling the strainers. After the June 24 event, the licensee determined that both events
had been caused by the injectable sealant that had been used to repair cracks in the floor of
the service water building, which is also the roof of the SW intake tunnel. The tunnel
provides a common water source for both the SW and emergency service water (ESW)
systems of Unit 1 and Unit 2. As a result of the crack repair activities, a large amount of
sealant entered the tunnel and a portion of it was drawn into the SW strainers.
Following the June 19 and June 24 events, the licensee erroneously concluded that the
material that fouled the SW system strainers could not affect the ESW systems. On June 28,
1996, during operations to clean the SW intake tunnel, divers found sealant in the tunnel in a
place that could compromise the operability of the ESW systems. Subsequently, the licensee
declared the ESW system inoperable and shut down both reactors.
An Augmented Inspection Team (AIT) was sent to the site to investigate the sealant injection
event. It concluded that the root cause of the strainer fouling was poor control of work on a
safety-related structure. The licensee staff responsible for assigning and controlling this work
did not know enough about the facility to appreciate the potential consequences of this work.
Therefore, a contractor, who was permitted to seal cracks in the safety-related SW intake
tunnel structure, had no knowledge of the potential impact of the work, no approved
procedures, and inadequate licensee oversight. The AIT also concluded that an inadequate
assessment of the root cause of the June 19 and June 24 events, as well as the failure to
develop an initial inspection and recovery plan that was comprehensive and thorough, permitted repeated challenges to key safety systems and threatened the availability of the
ultimate heat sink (UHS). Loss of the function of these safety systems, and the resultant loss
of the UHS, would have significantly affected the licensee's ability to respond to analyzed
accidents. Had the root cause for the initial event been thoroughly evaluated, the event of
June 24 could have been avoided, reducing the time that the ESW system for both units was
threatened.
Conclusion
These events illustrate the consequences and the possible safety impact of inadequate
oversight of contractors during sealant injection activities. Such activities can adversely
impact on the ability of safety-related systems to perform their intended safety function if
called upon.
Related Generic Communications
U.S. Nuclear Regulatory Commission, Information Notice (IN) 82-06, "Failure of Steam
Generator Primary Side Manway Closure Studs," dated March 12, 1982.
U.S. Nuclear Regulatory Commission, IN 85-90, "Use of Sealing Compounds in an Operating
System," dated November 19, 1985.
U.S. Nuclear Regulatory Commission, IN 93-90, "Unisolatable Reactor Coolant System Leak
Following Repeated Applications of Leak Sealant," dated December 1, 1993.
IN 97-74 September 24, 1997 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.
Hi Jack W.
,Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
William F. Burton, NRR
301-415-2853 E-mail: wfb@nrc.gov
T. Jerrell Carter, Jr.
301-415-1153 E-mail: tjc@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
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Attachment
September 24, 1997 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
97-73
97-72
Fire Hazard in the Use
of a Leak Sealant
Potential for Failure
of the Omega Series
Sprinkler Heads
Inappropriate Use of
10 CFR 50.59 Regarding
Reduced Seismic Criteria
for Temporary Conditions
Potential Problems with
Seals
09/23/97
09/22/97
09/22/97
09/19/97
97-71
97-70
All holders of OLs for
nuclear power reactors
except those who have
permanently ceased
operations and have
certified that fuel
has been permanently
removed from the
reactor vessel
All holders of OLs or
CPs for nuclear power
reactors and fuel
cycle facilities
All holders of OLs for
nuclear power reactors
except those who have
permanently ceased
operations and have
certified that fuel
has been permanently
removed from the
reactor vessel
All holders of OLs for
nuclear power reactors
except those who have
permanently ceased
operations and have
certified that fuel has
been permanently removed
from the reactor vessel
OL = Operating License
CP = Construction Permit
IN 97-74 September 24, 1997 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 D.B. Matthews for
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
William F. Burton, NRR
301-415-2853 E-mail: wfb@nrc.gov
T. Jerrell Carter, Jr.
301-415-1153 E-mail: tjc@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
Tech Editor has reviewed and concurred on 913/97 DOCUMENT NAME: 97-74.IN *SEE PREVIOUS CONCURRENCES
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OFFICE
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DATE
09/05/97
09/08/97
09/11/97
091//97
OFFICIAL RECORD COPY
IN 97-xx
September xx, 1997 This information notice requires no specific action or written response. If you have any
questions about the infornation in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
William F. Burton, NRR
301-415-2853 E-mail: wfb@nrc.gov
T. Jerrell Carter, Jr.
301-415-1153 E-mail: tjcenrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\WFBXBVSEAL.IN
- SEE PREVIOUS CONCURRENCES
To receive a copy of this document, Indicate In the box: SC" = Copy without enclosures "E! - Copy with enclosures "N" - No copy
OFFICE
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CONTACT
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NAME
JCarter*
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DATE
09/05/97
09/08/97
109/11/97
109/
/97
OFFICIAL RECORD COPY
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- IN97-xx
August xx, 1997 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.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical Contacts:
William F. Burton, NRR
301-415-2853 E-mail: wfb@nrc.gov
T. Jerrell Carter, Jr.
301-415-1153 E-mail: tjc@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\WFB\\BVSEAL.IN
To receive a copy of this docwnent. Indicate In the box: "C" = Copy without enclosures
"EF - Copy with enclosures "N" a No copy
OFFICE
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