BYRON 2004-0033, Supplemental One to Licensee Event Report (LER) 454-2003-003-00, Licensed Maximum Power Level Exceeded Due to Inaccuracies in Feedwater Ultrasonic Flow Measurements Caused by Signal Noise Contamination

Supplemental One to Licensee Event Report (LER) 454-2003-003-00, Licensed Maximum Power Level Exceeded Due to Inaccuracies in Feedwater Ultrasonic Flow Measurements Caused by Signal Noise Contamination

ML080290408
Person / Time
Site:	Byron
Issue date:	03/31/2004
From:	Kuczynski S Exelon Generation Co, Exelon Nuclear
To:	Document Control Desk, NRC/RGN-III
References
2004-0033, BYRON 2004-0033, FOIA/PA-2008-0046 LER 03-003-01
Download: ML080290408 (5)

Text

Exelon Generation Company, LLC www.exeloncorp.com I::xeltanNUClear Byron Station 4450 North German Church Road

• Byron, IL 61010-9794 March 31, 2004 LTR: BYRON 2004-0033 File: 2.01.0700 United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

, Supplement One to Licensee Event Report (LER) 454-2003-003-00,

• "Licensed Maximum Power Level Exceeded Due to Inaccuracies in Feedwater Ultrasonic Flow Measurements Caused by Signal Noise Contamination" Byron Station,.Unit 1 and Unit 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455 O Enclosed is a supplemental report to an LER involving an overpower condition on Byron Station Unit 1 and Unit 2 as a result of inaccuracies discovered in the measurement of feedwater flow using an ultrasonic flow measurement system. The supplemental information involves the results of a tracer test performed to further determine the accuracy of feedwater flow.

Should you have any questions concerning this matter, please contact Mr. William Grundmann, Regulatory Assurance Manager, at (815) 234-5441, extension 2800.

Respectfully, Stephen E. Kuczynski Site Vice President Byron Nuclear Generating Station Attachment LER 454-2003-003-01 cc: Regional Administrator, Region Ill, NRC O NRC Senior Resident Inspector- Byron Station

NFNC FORM 366 U.S. NUCLEAR REGULATORY APPROVED BY OMB NO. 3150-0104 EXPIRES 7-31-2004 (7-2001) COMMISSION Estimated burden per response to comply with this mandatory information collection request: 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fedý. back to industry. Send comments regarding burden estimate to the Records Management Branch (T-6 E6),

U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to LICENSEE EVENT REPORT (LER) bjslinrc.gov, and to the Desk Officer, Office of nformation and Reulatory Affairs, NEOB-10202 (35-14), Office of Management and Budget, Washington, DC e003 Ifa means used to impose i information collection does not display a currently valid 0MB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

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Byron 9 ~nrk',*I=T MI IMRIPIP14 ~ '.".

Station, Unit 1 05000454[ 1 OF 5

-4;l;,ieinsed Maximum Power Level Exceeded Due to Inaccuracies in Feedwater Ultrasonic Flow Measurements

5. EVENT DATE 6. LER NUMBER j 7. REPORT DATE / 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MO DAY YEAR YEAR NUMBER' NO MO DAY YEAR Byron, Unit 2 0500455 FACILITY NAME DOCKET NUMBER 08 28 2003 2003 003 01 03 31 2004

9. OPERATING 1t. THIR REPOIRT I SIIRMITTED PIIRqIIANT TO THE RIFEtUIREIMENTR IF 4r0 CFR 9, r~hek al that arniv\

MODE 1 20.2201 (b) 120.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(ix)(A)

10. POWER 20.2201 (d) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(x)

LEVEL 100 20.2203(a)(1) _50.36(c)(1)(i)(A) 50.73 (a)(2)a(iv) (A) 73.71 (a)(4) 20.2203(a)(2)(i) 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71 (a)(5) 2 a 1 5 Specify in Abstract below or in

• 20.2203(a)(2)(iii) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C NRC Form 366A

.20.2203(a)(2)(v)

~.'~ 20.2203(a)L2)(iV) 50.73(a)(2)(i)(A)

.50.73(a)(2)(i)(B)

__50.73(a)(2) 50.73(a)(2)(vii)

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• 20.2203(a)(2)(vi) 50.73(a)(2)(i)(C) 50.73 a 2 viii) (A) ,

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• 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(B)

12. LICENSEE CONTACT FOR THIS LER NAME TELEPHONE NUMBER (Include Area Code):'

William Grundmann, Regulatory Assurance Manager (815) 406-2800

13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT MANU- . REPORTAL MANU- REPORTABLE CAUSER SYSTEM COMPONENT FACTURE TO EPIX CAUSE SYSTEM COMPONENT FACTURER TO FPIX

14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED MONTH DAY YEAR SUBMISSION 7YES (If yes, complete EXPECTED SUBMISSION DATE) FX INO DATE _

16. ABSTRACT (Umit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

Byron Station Unit 1 and Unit 2 exceeded their licensed maximum power level by 2.62% and 1.88%, respectively.

In May of 2000 an Ultrasonic Flow Measurement System (UFMS) was installed on the main feedwater lines to the steam generators to more accurately measure feedwater flow. This corrected feedwater flow is then used in the reactor power calorimetric calculation. Feedwater flow pressure pulses occurred at frequencies that affected* the UFMS signal and resulted, in a bias in the determinations of the flow correction factors. This resulted in a non-conservative calorimetric calculation. When reactor power was adjusted to match the calorimetric power, an overpower condition was created. When this condition was discovered the UFMS was removed from service.

Implementation of the UFMS has been suspended. Analyses performed indicated there was no adverse safety impact for the overpower condition on each unit. In accordance with Byron Station Unit 1 License Condition 2.F and Byron Station Unit 2 License condition 2.G, a notification was made to the NRC at 1355 CST on August 28, 2003, due to the violation of license condition 2.C(1) of each license, "Maximum Power Level."

(K:\BYR_DOCS\ LERS\2003lers\454-2003-OO3-00.doc)

.NRQ; FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (7-2001) EXPIRES 0713112004 Estimated burden per response to comply with this mandatory information collection request: 50 hrs. Reported lessons learned are incorporated into the licensing process and fed back to industry. Forward comments regarding burden LICENSEE EVENT REPORT (LER) estimate to the information and Records Management Branch (t-6 f33), U.S.

TEXT CONTINUATION Nuclear Regulatory Commission, Washington, PC 20555-0001, and to the Paperwork Reduction Project (3150-0104), Office Of Management And Budget, Washington, DC 20503. Ifan information collection' does not display a currently 1

valid OMB control number, the NRC may not conduct orsponsor, and a person is not required to respond to, the information collection.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR SEQUENTIAL REVISION STN 05000454 NUMBER NUMBER Byron Station, Unit 1 2003 - 003 - 01 i 3 of 5 (If more space is required, use additional copies of NRC Form 366A)(1 7)

A broader test plan was developed in early 2003 to continue the investigation. In May 2003, a flow comparison test with the common main feedwater header UFMS flow to the sum of the UFMS measurement in the four main feedwater loops was conducted on Braidwood Station Unit 1. The results of this test were within the acceptance criteria. In August 2003, this test was re-performed at Byron Station Unit 1. The difference between the sum of the UFMS measurements in the four main feedwater loops and the common main feedwater header was outside the acceptance criteria (1.572% compared to a maximum allowable statistical limit of 0.70%). With this test outside of its acceptance criteria, Byron Station reduced power and returned the correction factors to 1.0 on both units, pending resolution of the issue.

Upon investigation by site and vendor personnel, it was determined that signal noise affected the flow velocity calculations, which in .turn affected the determination of the correction factors. With the noise contaminated correction factors used in the calorimetric calculation, a non-conservative or lower power measurement resulted. When reactor power was adjusted to match the calorimetric power, an overpower condition was created. An overpower condition on Unit. 1 and Unit 2 potentially existed since initial implementation in May 2000.

As part of the UFMS independent review, a flow measurement utilizing a radioactive tracer was performed on the Unit 1 and Unit 2 main feedwater systems. The tracer results indicated there was a non-conservative bias in the UFMS installed on the common main feedwater header. This test also validated the accuracy of the installed venturi flow measurement system.

The originally reported worst-case overpower conditions on Unit 1 and Unit 2 (Sept. 2003) were based on the premise that the UFMS on the common main feedwater header was providing accurate flow measurements. Based on the results of the tracer test on Unit 1 and Unit 2 validating the accuracy of the venturi flow measurement, the worst-case overpower is now based on the maximum UFMS correction factor applied to the venturi flow measurement. The worst-case overpower conditions are 102.62% for Unit 1 and 101.88% for Unit 2.

In accordance with Byron Station Unit 1 License Condition 2.F and Byron Station Unit 2 License condition 2.G notification was made to the NRC at 1355 CST on August 28, 2003, due to the violation of License Condition 2.C(l) of each license, Maximum Power Level."

C. Cause of Event:

The initial root cause of this event was determined to be noise contamination of the UFMS ultrasonic signal.

Feedwater flow pressure pulses occurred at frequencies that affected the UFMS signal and resulted in a bias in the determinations of the flow correction factors. This noise caused the UFMS to indicate a lower than actual feedwater flowrate which resulted in a non-conservative calorimetric calculation.

(K:\8YR..POCS%.LERS\2031ers\454-2003-003-00.doc)'

,NRrFORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (7-2001) EXPIRES 0713112004 Estimated burden per response to comply with this mandatory information collection request: 50 hrs. Reported lessons learned are incorporated into the licensing process and fed back to industry. Forward comments regarding burden LICENSEE EVENT REPORT (LER) estimate to the information and Records Management Branch (t-6 f33), U.S.

TEXT CONTINUATION Nuclear Regulatory Commission, Washington, DC 20555-0001, and to the Paperwork Reduction Project (3150-0104), Office Of Management And Budget, Washington, DC 20503. Ifan information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

FACILITY NAME (1), DOCKET NUMBER (2 LER NUMBER (6) PAGE (3)

YEAR SEQUENTIAL I REVISION Byron Station, Unit I STN 05000454NUER NUMBER UMR NUMBER 2003 - 003 - 01 4 of 5 (If more space is required, use additional copies of NRC Form 366A)(17)

Contributing causes were a lack of questioning attitude during the implementation and subsequent evaluations and the failure to use the diagnostic tool which could have identified the noise.

Based on the result of the tracer test mentioned above, the initial root cause for inaccuracies in the feedwater ultrasonic measurement is incomplete. The UFMS vendor is currently investigating the performance issues associated with the UFMS.

D. Safety Consequences:

The evaluations below envelope the revised overpower condition discussed in section B.

The safety significance of the overpower issue for Byron Station Units 1 and 2 has been evaluated by I Westinghouse and Exelon Nuclear Fuels. The evaluations considered a conservatively bounding overpower value of 102.62% plus a 2% of the Byron uprated power limit (i.e., 3586.6 Mwt) calorimetric uncertainty.

Byron station implemented a 5% power uprate in May 2001. The impact of the overpower condition was evaluated for pre and post power uprate operations. The following areas were reviewed:

Design Transients Operating Margin to Reactor Trip Neutron Fluence Projections, Reactor Vessel Integrity, and Low Temperature Overpressure Protection Loss of Coolant Containment Integrity Steamline Break Containment Integrity All Updated Final Safety Analysis Report Chapter 15 accidents Fuel Evaluation The acceptance criteria were met for all the evaluated events.

This event did not result in a safety system function failure.

E. Corrective Actions:

Byron Station Units 1 and 2 reduced reactor power to ensure the licensed thermal power limit was not being exceeded. Additionally, the correction factors for the feedwater flow venturis were reset to 1.0.

The implementation of the UFMS has been suspended.

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- -NR6 FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (7-2001) EXPIRES 0713112004 Estimated burden per response to comply with this mandatory information collection request: 50 hrs. Reported lessons learned are incorporated into the licensing process and fed back to industry. Forward comments regarding burden

• I It "ENSEE EVENT REPORT (LER) estimate to the information and Records Management Branch (t-6 f33), U.S.

TEXT CONTINUATION Nuclear Regulatory Commission, Washington, DC 20555-0001, and to the Paperwork Reduction Project (3150-0104), Office Of Management And Budget, Washington, DC 20503. If an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not reauired to resoond to. the information collection.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) I PAGE (3)

YEAR SEQUENTIAL REVISION 1STN 05000454 NUMBER NUMBER 2003 - 003 - 01 5 of 5 (Ifmore space is required, use additional copies of NRC Form 366A)(17)

F. Previous Occurrences:

There were no previous occurrences of a violation of licensed maximum power level due to the UFMS system noise. Byron reported an overpower of 0.12% on Unit 1 and 2 due to personnel error while using the UFMS system (LER 2001-001-01 dated June 14, 2001.)

G. Component Failure Data:

N/A

(

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