05000321/LER-2013-001, Regarding Unplanned RPS Actuation in Response to Reactor Coolant Chemistry Event Caused by a Condenser Tube Leak

Regarding Unplanned RPS Actuation in Response to Reactor Coolant Chemistry Event Caused by a Condenser Tube Leak

ML13095A153
Person / Time
Site:	Hatch
Issue date:	04/04/2013
From:	Pierce C Southern Nuclear Operating Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
NL-13-0652 LER 13-001-00
Download: ML13095A153 (6)

LER-2013-001, Regarding Unplanned RPS Actuation in Response to Reactor Coolant Chemistry Event Caused by a Condenser Tube Leak

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(8) 10 CFR 50.73(a)(2)(viii)(8) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(8) 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(8)
3212013001R00 - NRC Website

text

Charles R. Pierce Southern Nuclear Regul atory Affairs Director Operating Company, Inc.

40 Inverness Center Parkway Post Offi ce Box 1295 Birmingham, Alabama 35201 Tel 205 9927872 Fax 2059927601 SOUTHERNA.

COMPANY April 4, 2013 Docket Nos.: 50-321 NL-13-0652 U. S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant Licensee Event Report 2013-01 Unplanned RPS Actuation in Response to Reactor Coolant Chemistry Event Caused by a Condenser Tube Leak Ladies and Gentlemen:

In accordance with the requirements of 1 OCFR50. 73(a)(2)(iv)(A), Southern Nuclear Operating Company hereby submits the enclosed Licensee Event Report concerning a reactor coolant chemistry event caused by a condenser tube leak.

This letter contains no NRC commitments. If you have any questions, please contact Doug McKinney at (205) 992-5982.

Respectfully submitted, C. R. Pierce Regulatory AHairs Director CRP/sb/lac Enclosures: LER 1-2013-01

U. S. Nuclear Regulatory Commission NL-13-0652 Page 2 cc:

Southern Nuclear Operating Company Mr. S.

Kuczynski, Chairman, President &

Mr.

G. Bost, Executive Vice President &Chief Nuclear Officer Mr.

R. Madison, Vice President - Hatch Mr. B. L. Ivey, Vice President - Regulatory Affairs Mr.

J. Adams, Vice President -

Operations Mr. M. A. Dowd -

Coordinator RTYPE: CHA02.004 U. S. Nuclear Regulatorv Commission Mr. V. M. McCree, Regional Administrator Mr. R.

Martin. NRR Senior Project Manager Hatch Mr. E. D. Morris, Senior Resident Inspector Hatch

Licensee Event Report 1-2013-01 Unplanned RPS Actuation in Response to Reactor Coolant Chemistry Caused by a Condenser Tube Leak

NRC FORM 366 U.S. NUCL.EAR REGUL.ATORY COMMISSION APPROVED BY OMB: NO. 3150*0104 EXPIRES: 10/31/2013 1 (}2010)

Estimated burden per response to comply with this mandatory COllection]

request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons leamed are Incorporated into the licensing process and fed back to industry. Send comments re~arding burden estimate to the Records and FOIAlPrivacy Service Branch ( *5 F53), U.S.

LICENSEE EVENT REPORT (LER)

Nuclear Re~ulatOry Commission, Washington, DC 20555*0001, or by internet a-mail 10 in ocoilects.resources@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Mana~ement and Budget, Washington, DC 20503. If a means used to impose an in ormation collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to resoond to. the information collection.

13. PAGE Edwin 1. Hatch Nuclear Plant 05000321 1 OF 3

14. TITLE Unplanned RPS Actuation in Response to Reactor Coolant Chemistry Event Caused by a Condenser Tube Leak

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER SEQUENTIAL REV MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NO.

05000 FACILITY NAME DOCKET NUMBER 02 10 2013 2013 - 001 -

0 4

4 2013 05000

19. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) o 20.2201 (b) o 20.2203(a)(3)(i) o 50.73(a)(2)(i)(C) o 50.73(a)(2)(vii)

Mode 1 o 20.2201 (d) o 20.2203(a)(3)(ii) o 50.73(a)(2)(ii)(A) o 50.73(a)(2)(viii)(A) o 20.2203(a)(1) o 20.2203(a)(4) o 50.73(a)(2)(ii)(8) o 50.73(a)(2)(viii)(8) o 20.2203(a)(2)(i) o 50.36(c)(1)(i)(A) o 50.73(a)(2)(iii) o 50.73(a)(2)(ix)(A)

10. POWER LEVEL o 20.2203(a)(2)(ii) o 50.36(c)(1)(ii)(A) 181 50.73(a)(2)(iv)(A) o 50.73(a)(2)(x) o 20.2203(a)(2)(iii) o 50.36(c)(2) o 50.73(a)(2)(v)(A) o 73.71 (a)(4) o 20.2203(a)(2)(iv) o 50.46(a)(3)(ii) o 50.73(a)(2)(v)(8) o 73.71 (a)(5) 100 o 20.2203(a)(2)(v) o 50.73(a)(2)(i)(A) o 50.73(a)(2)(v)(C)

D OTHER o 20.2203(a)(2)(vi) o 50.73(a)(2)(i)(8) o SO.73(a)(2)(v)(O)

Specify in Abstract below or in NRC Form 366A

12. LICENSEE CONTACT FOR THIS LER FACILITY NAME I~ELEPHONE NUMBER (Indude Area Code)

Edwin 1. Hatch / Steven Tipps - Principal Engineer - Licensing 912-537 -5880 MANU-REPORTABLE MANU-REPORTABLE

CAUSE

SYSTEM COMPONENT

CAUSE

SYSTEM COMPONENT FACTURER TO EPIX FACTURER TO EPIX X

SG COND F175 Y

14. SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED SUBMISSION 05 30 2013 181 YES (If yes, complete 15. EXPECTED SUBMISSION DATE)

DNO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

On February 10, 2013 at 0536 Eastern Standard Time (EST), while operating at 99.8 percent rated thermal power (RTP), a system operator reported that the "System Inlet High Conductivity" alarm had been received I at the local Condensate Polishing System panel. This annunciator is set to alarm when conductivity reaches 0.239 micro mhos per cm. Control room instruments immediately began to indicate that conductivity levels I were slowly increasing for the condenser and the reactor vessel coolant. The crew entered the abnormal operating procedure for Condenser Tube Leaks/Chemical Intrusion and began decreasing power to 88 percent at 0555 EST. The crew continued to reduce power to 47 percent RTP. Inlet conductivity reached 5 micro mhos per cm and the shift supervisor directed the crew to enter the abnormal operating procedure for a manual SCRAM at 0700 EST. The unplanned manual RPS actuation was initiated as a protective action for the reactor vessel, as the increasing water chemistry conductivity indicated a possibly serious condition in which circulating water tube(s) were damaged within the condenser and were leaking into the hot well.

NRC FORM 366 (9-2007)

PRINTED ON RECYCLED PAPER

PLANT AND SYSTEM IDENTIFICATION

General Electric - Boiling Water Reactor Energy Industry Identification System codes appear in the text as (EllS Code XX).

DESCRIPTION OF EVENT

On 2/1012013 at 0536 EST, while operating at 99.8 percent RTP, a system operator reported that the "System Inlet High Conductivity" alarm had been received at the local Condensate Polishing System panel. The setpoint for this annunciator is 0.239 micro mhos per cm. At 0540 EST, control room instruments indicated that conductivity levels were increasing for the condenser and the reactor vessel coolant. The conductivity was greater than 0.3 micro mhos per cm in the condensate, while still under 0.1 micro mho per cm at the inlet to the reactor.

The shift supervisor entered the abnormal operating procedure for Condenser Tube Leaks/Chemical Intrusion and directed the crew to decrease power to 88 percent RTP. After verifying conductivity levels, the crew continued to reduce power under the direction of shift management to 47 percent RTP at 0647 EST. Inlet conductivity reached 5 micro mhos per cm and the shift supervisor ordered the crew to enter the abnormal operating procedure for a manual SCRAM at 0700 EST.

The unplanned RPS actuation was initiated as a protective action for the reactor vessel pressure boundary, as increasing water chemistry conductivity indicated the possibility of long term degradation of pressure boundary materials. This condition could have increased the potential for stress corrosion cracking of internal vessel components if it had not been addressed. The Technical Requirements Manual (TRM) 3.4.1 required action statement (RAS) for Condition A directs the shift to return to less than 5.0 micro mhos per cm within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and to restore reactor coolant system (RCS) chemistry to within the limits of the associated table, T3.4.1-1.

The condenser conductivity never exceeded 5 micro mhos per cm prior to the SCRAM or immediately thereafter. Shift management made the conservative decision to enter a manual SCRAM after the power descent, rather than waiting 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Management believed it to be necessary to ensure that degradation of the reactor coolant pressure boundary was not exacerbated by poor chemistry conditions. The orderly shutdown was completed in accordance with the TRM and was not addressed in HNP-1 Technical Specifications.

CAUSE OF EVENT

The root cause report has not been completed at this time, but it has been determined that one circulating water tube contained a through-wall crack and multiple tubes were damaged when a section of the condenser false bottom impacted a tube bundle. Preliminary cause analyses for the damage incurred on the false bottom indicate that the water levels in the 1A and 1B condensers were significantly different and this difference was a causal factor to the false bottom damage. The false bottom of the lA condenser was encapsulated and pressure perturbations developed when steam was introduced and became trapped below the false bottom.

The phase transition of water / steam within a water-solid environment placed a hydraulic load on the false bottom. The root cause analysis will provide additional details on causes and corrective actions.

REPORT ABILITY ANALYSIS AND SAFETY ASSESSMENT The orderly reactor shutdown resulted from conservative actions that are part of an operational strategy laid out in associated abnormal operating procedures that includes the insertion of a manual RPS actuation or SCRAM as a means to limit the potential long term pressure boundary issues that can be created by abnormal I LICENSEE EVENT REPORT (LER) u.s. NUCLEAR REGULATORY COMMISSION (1 ()'2010)

CONTINUATION SHEET

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE SEQUENTIAL IREVISION YEAR NUMBER NUMBER Edwin 1. Hatch Nuclear Plant 05000-321 I

3 OF 3

2013 001 0

reactor coolant chemistry. From this perspective the RPS actuation is an expected culmination of operator actions when the reactor coolant conductivity has a potential to worsen. This event was therefore determined to be reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A): actuation of any of the systems listed in paragraph (a)(2)(iv)(B), which includes any unplanned manual RPS actuation.

This condition occurred at rated power conditions and no monitored safety system parameters were adversely impacted or exceeded.

Based on this information this event is considered to have low nuclear safety significance.

CORRECTIVE ACTIONS

Condenser repairs were completed. Instrumentation was installed to measure flow out of the lA condenser and both Unit 1 condensers were equipped with instrumentation to monitor pressure perturbations. Procedure changes were made to maintain the water levels in the lA and IB condensers in such a way that pressure perturbations would be minimized, if any should occur. Finally, HNP-l was returned to power without further incident. The root cause report will provide more information on immediate, interim, and corrective actions to prevent recurrence.

ADDITIONAL INFORMATION

Other Systems Affected: None

Failed Components Information

HNP I-A Condenser Master Parts List Number: IN61BOOIA EllS System Code: SG Manufacturer: Foster Wheeler Reportable to EPIX: Y Model Number: N/A Root Cause Code: X Type: M EllS Component Code: COND Manufacturer Code: F175 Commitment Information: This report does not create any new permanent licensing commitments.

Previous Similar Events

2005: LER 2005-003-001 was written for HNP-2 when the unit was taken off line due to condenser tube leaks. The root cause was a manufacturer defect in tube plugs installed during the previous refueling outage.

The plugs failed on return to power and were replaced with components supplied by a different manufacturer after the cause was determined. This Unit 2 shutdown event due to condenser tube leaks was considerably different than the recent Unit 1 event. The Unit 1 tube leak developed within the latest fuel cycle and was not previously known to exist. The corrective actions from LER 2005-003-001 could not be expected to preclude the 2013 Unit 1 event reported here.