UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555

July 21, 2003

NRC INFORMATION NOTICE 2002-26, Supplement 1: ADDITIONAL FAILURE OF STEAM

DRYER AFTER A RECENT

POWER UPRATE

Addressees

All holders of operating license 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.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to alert

addressees to another failure of the steam dryer at Quad Cities Nuclear Power Station, Unit 2

(QC-2), a boiling water reactor (BWR), during operations following a power uprate. It is

expected 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

The failure of a steam dryer cover plate in June 2002 at QC-2 was discussed in IN 2002-26,

“Failure of Steam Dryer Cover Plate After a Recent Power Uprate” (ML022530291). 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 determined that the failure of the plate was due to high-cycle fatigue. This fatigue was

attributed to excessive vibration caused by the synchronization of the cover plate resonance

frequency, the nozzle chamber standing acoustic wave frequency, and the vortex shedding

frequency. The licensee concluded that the three frequencies synchronized in a very narrow

band of steam flow at or near the steam flow required to reach full power under the power

uprate. Prior to returning the unit to service, the dryer cover plates were replaced with thicker

plates with a higher fundamental frequency to eliminate the resonance of induced pressure

oscillations with the natural frequency of the plate.

In late May 2003, the licensee again noted increasing moisture carryover; however, there were

no discernible changes in other reactor parameters that indicated dryer degradation. On

May 28, 2003, the licensee reduced power on QC-2 to the pre-EPU 100% power level. 

ML031980434
IN 2002-26, Sup 1

Page 2 of 2

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 on 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. A root cause analysis by the licensee is in progress. 

The licensee believes the most probable cause of the failure is low-frequency, high-cycle

fatigue driven by flow-induced vibrations associated with the higher steam flows present during

EPU operating conditions.

Discussion

GE Nuclear Energy and the licensee did not foresee this phenomenon. GE Nuclear Energy,

the licensee, and the NRC are evaluating this event with regard to its generic implications for

plants that are operating with or planning to apply for an extended power uprate. Licensees

should be alert to the possibility of similar unanticipated effects from increasing flow, power, or

differential pressure associated with a major modification such as an extended 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

Fred Lyon, NRR

(301) 415-2296

E-mail: cfl@nrc.gov

Attachment: List of Recently Issued NRC Information Notices