Information Notice 2002-26, July 2008 Evidentiary Hearing - Intervenor Exhibit NEC-JH 56, NRC Information Notice 2002-26, Supplement 2: Additional Flow-Induced Vibration Failures After a Recent Power Uprate
| ML082340105 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 01/09/2004 |
| From: | Beckner W Office of Nuclear Reactor Regulation |
| To: | |
| SECY RAS | |
| References | |
| 06-849-03-LR, 50-271-LR, Entergy-Intervenor-NEC-JH_56, OARC20080821TJB2=Fix Case Reference, RAS M-222 IN-02-026, Suppl 2 | |
| Download: ML082340105 (5) | |
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H-32Z-
DOCKETED
August 12, 2008 (11:00am)
NEC-JH_56
OFFICE OF SECRETARY
RULEMAKINGS AND
ADJUDICATIONS STAFF
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
January 9, 2004
NRC INFORMATION NOTICE 2002-26, SUPPLEMENT 2:
ADDITIONAL FLOW-INDUCED
VIBRATION FAILURES AFTER A
RECENT POWER UPRATE
Addressees
All holders of an operating license or a construction permit for nuclear power reactors, except
those that have, permanently ceased operations and have certified that fuel has been
permanently removed from the reactor.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this supplement to a previously
issued information notice (IN) to alert addressees to the failure of the steam dryer and other
plant components at Quad Cities Nuclear Power Station, Unit 1 (QC-1), a boiling water reactor
(BWR), during operations following a power uprate. The NRC expects that the 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
As discussed in IN 2002-26, "Failure of Steam Dryer Cover Plate After a Recent Power Uprate"
(ML022530291), a cover plate on the. outside of the steam dryer at Quad Cities Nuclear Power
Station, Unit 2 (QC-2), broke loose in June 2002 and caused pieces of the dryer to be swept
down the main steamline. The failure followed completion of a refueling outage in March 2002 and subsequent implementation of an extended power uprate (EPU) from 2511 MWt to
2957 MWt (17.8% increase). Before the unit was shut down in 2002, steam dryer degradation
was indicated by an increase in moisture carryover and minor perturbations in reactor pressure, water level, and steam flow. The licensee evaluated the cause of the steam dryer cover plate
failure and determined that the failure of the plate was due to high-cycle fatigue. The licensee
recovered all loose dryer pieces and did not identify any additional damage other than minor
scratches and gouges to the main steamline. Prior to returning the unit to service, the licensee
modified the steam dryer by installing thicker cover plates with higher strength welds, and
implemented enhanced monitoring of steam moisture content, reactor steam dome pressure, main steamline flow rates, and reactor water level.
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IN 2002-26, Sup 2 The second failure of the steam dryer in May 2003 at QC-2 was discussed in IN 2002-26, Supplement 1, "Additional Failure of Steam Dryer After a Recent Power Uprate"
(ML031980434). In that case, the licensee again noted increasing moisture carryover in late
May 2003; however, there were no discernible changes in other reactor parameters. On
May 28, 2003, the licensee reduced power on QC-2 to the pre-EPU 100% power level. Moisture
carryover levels remained above normal, and on June 11, 2003, the licensee shut down QC-2 to
inspect the dryer. Inspection of the dryer revealed (1) through-wall cracks (about 90 inches long)
in the vertical and horizontal portions of the outer bank hood, 90-degree side, (2) one vertical
and two diagonal internal braces detached from the outer bank hood, 90-degree side, (3) one
severed vertical internal brace on the outer bank hood, 270-degree side, and (4) three cracked
tie bars on top of the dryer. The licensee believes the most probable cause of the failure of the
steam dryer in QC-2 is low-frequency, high-cycle fatigue driven by flow-induced vibrations
associated with the higher steam flows present during EPU operating conditions.
In late October 2003 at QC-1, the licensee observed changes in main steamline flows, steamline
pressure drop, and increasing moisture carryover measurements. The symptoms observed
were consistent with previous events at QC-2 that resulted in the discovery of damage to the
steam dryer. The licensee subsequently reduced the power level of QC-1 to pre-EPU
conditions. After power was reduced, the moisture carryover was lower than before the power
reduction, but higher than the anticipated level. On November 12, the licensee shut down QC-1 to inspect the steam dryer and identified significant damage to several areas. For example, an
identified crack was determined to have initiated at the top corner portion of the steam dryer
hood and then extended horizontally toward the center of the hood and downward into the
vertical section of the hood. The crack terminated in the vertical section where a portion of the
dryer was missing. This missing piece of the steam dryer outer bank hood is approximately 6.5 inches (16.5 cm) by 9.0 inches (22.9 cm) and 0.5 inches (1.3 cm) thick. The licensee believes
that a piece or pieces the size of this opening or smaller broke off due to fatigue cracking. The
licensee performed an extensive but unsuccessful search for the lost part or parts. However, the licensee did identify impact marks on the impeller of the 1 B recirculation pump that
suggested that the missing part or parts passed through the pump. The licensee concluded that
the missing part or parts migrated to the bottom head region of the reactor vessel. In addition to
damage to the steam dryer at QC-1, the licensee identified significant flow-induced vibration
damage to main steam line tieback supports and a main steam electromatic relief valve
(including its attached drain line, actuator, and support), as well as loose clamps on the main
steam line supports. Before restarting QC-1 on November 29, the licensee repaired the steam
dryer and other damaged plant components identified during its inspections. With respect to the
missing steam dryer metal plate, the licensee performed an operability evaluation for continued
operation with the missing part or parts and will decide, prior to the next refueling outage, whether to continue efforts to locate and retrieve the missing dryer material.
IN 2002-26, Sup 2 Discussion
When operating above the original licensed thermal power (OLTP) level, BWR plants can
experience a significant increase in the velocity of the steam generated from feedwater in the
reactor core and directed through piping to the plant turbine generator. This increased steam
velocity could damage plant components through flow-induced vibration. While major
safety-related components undergo detailed review to demonstrate their capability to perform the
applicable safety functions, nonsafety-related components and safety-related subcomponents
have received less attention by the licensee and the NRC during preparation for nuclear power
plant operation above the OLTP level.
Although performing a nonsafety-related function, the steam dryer in a BWR plant must maintain
its structural integrity to avoid loose dryer parts from entering the reactor vessel or steam lines
and adversely affecting plant operation. Industry representatives say that cracking occurred in
steam dryers during the early operational phase of some BWR plants. The steam dryer failures
at Quad Cities while operating at EPU conditions have led the BWR Owners Group (BWROG) to
ask its 13WR Vessel and Internals Project (BWRVIP) to develop inspection and evaluation
guidelines for BWR steam dryers. In addition, General Electric (GE) Nuclear Energy issued
Service Information Letter (SIL) 644, "BWR/3 steam dryer failure," on August 21, 2002, and
Supplement 1 to SIL 644 on September 5, 2003, to provide monitoring and inspection
recommendations for BWR plants that are operating, or plan to operate, at power levels greater
than the OLTP.
In addition to the BWR steam dryers, flow-induced vibration during nuclear power plant
operation above the OLTP level can potentially damage other plant components. For example, the QC-1 licensee identified significant flow-induced vibration damage to a main steam
electromatic relief valve (including its attached drain line, actuator, and support), as well as main
steam line support clamps and tieback supports. Therefore, information obtained from the
review of the flow-induced vibration damage at QC-1 might also be applicable to other BWR
plants with different steam dryer designs and to pressurized water reactor (PWR) plants
operating at conditions above their OLTP level. The significance of the lessons learned is
increased because operation of a nuclear power plant under conditions above the OLTP level
might place additional reliance on the capability of plant equipment, such as relief valves or
seismic restraints, to perform their intended functions as a result of higher reactor power levels
and steam and feedwater flow rates.
The NRC staff is reviewing plant-specific and industry-wide activities to address the potential for
flow-induced vibration damage to steam dryers and other plant components in BWR plants
operating or planning to operate at conditions above the OLTP level. Although it is very unlikely
that loose parts would adversely affect the safe shutdown of a plant, it is important to understand
I
the extent of damage that might be caused by steam dryer failures and to identify the lessons
learned from recent steam dryer failures for application to steam dryers at other BWR plants. It
is also important to address the potential for similar failures in other plant components in BWR or
PWR plants operating or planning to operate at conditions above the OLTP level.
.1
IN 2002-26, Sup 2 Licensees should be alert to the possibility of unanticipated effects from increasing flow, power, or differential pressure associated with a major modification such as a power uprate. 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.
IRA!
William D. Beckner, Chief
Reactor Operations Branch
Division of Inspection Program Management
Office of Nuclear Reactor Regulation
Technical Contacts:
Karla Stoedter, Region III
(309) 654-2227 E-mail: kkb(&.nrc.gov
Larry Rossbach, NRR
(301) 415-2863 E-mail: lwrP.nrc.gov
Jack Foster, NRR
(301) 415-3647 E-mail: iwfa..nrc.qov
Thomas G. Scarbrough, NRR
(301) 415-2794 E-mail: tgs(a.nrc.gov
Attachment: List of Recently Issued NRC Information Notices
Attachment
IN 2002-26, Sup 2 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
2003-11, Sup 1
2003-22
2003-21
2003-20
Note:
Leakage Found on Bottom-
Mounted Instrumentation
Nozzles
01/08/2004
All holders of operating licenses
or construction permits for nuclear
power reactors, except those that
have permanently ceased
operations and have certified that
fuel has been permanently
removed from the reactor.
All medical licensees and NRC
Master Materials License medical
use permittees.
All medical licensees.
Heightened Awareness for
Patients Containing Detectable
Amounts of Radiation from
Medical Administrations
High-Dose-Rate-Remote-
Afterloader Equipment Failure
12/09/2003
11/24/2003 Derating Whiting Cranes
10/22/2003
All holders of operating licenses
Purchased Before 1980
for nuclear power reactors, except
those who have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
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facilities, and independent spent
fuel storage installations:
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