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.

ML040080392
IN 2002-26, Sup 2

Page 2 of 4

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 flowinduced 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 1B 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

Page 3 of 4

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 BWR 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 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.
IN 2002-26, Sup 2

Page 4 of 4

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.

/RA/

William D. Beckner, Chief

Reactor Operations Branch

Division of Inspection Program Management

Office of Nuclear Reactor Regulation

Technical Contacts: Karla Stoedter, Region III Jack Foster, NRR

(309) 654-2227 (301) 415-3647

E-mail: kkb@nrc.gov E-mail: jwf@nrc.gov

Larry Rossbach, NRR Thomas G. Scarbrough, NRR

(301) 415-2863 (301) 415-2794

E-mail: lwr@nrc.gov E-mail: tgs@nrc.gov

Attachment: List of Recently Issued NRC Information Notices
____________________________________________________________________________________

OL = Operating License

CP = Construction Permit

Attachment 

IN 2002-26, Sup 2

Page 1 of 1

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

____________________________________________________________________________________

Information Date of 

Notice No. Subject Issuance Issued to

____________________________________________________________________________________

2003-11, Sup 1 Leakage Found on BottomMounted 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.

2003-22 Heightened Awareness for

Patients Containing Detectable

Amounts of Radiation from

Medical Administrations

12/09/2003 All medical licensees and NRC

Master Materials License medical

use permittees.

2003-21 High-Dose-Rate-RemoteAfterloader Equipment Failure11/24/2003 All medical licensees.

2003-20 Derating Whiting Cranes

Purchased Before 1980

10/22/2003 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; applicable

decommissioning reactors, fuel

facilities, and independent spent

fuel storage installations.

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