05000335/LER-2011-001, For St. Lucie, Unit 1, Regarding Unit 1 Manual Reactor Trip Due to High Condenser Backpressure Caused by Severe Influx of Jellyfish Into the Intake Structure

For St. Lucie, Unit 1, Regarding Unit 1 Manual Reactor Trip Due to High Condenser Backpressure Caused by Severe Influx of Jellyfish Into the Intake Structure

ML11301A071
Person / Time
Site:	Saint Lucie
Issue date:	10/20/2011
From:	Richard Anderson Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2011-454 LER 11-001-00
Download: ML11301A071 (4)

LER-2011-001, For St. Lucie, Unit 1, Regarding Unit 1 Manual Reactor Trip Due to High Condenser Backpressure Caused by Severe Influx of Jellyfish Into the Intake Structure

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)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 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)(B), Loss of Safety Function - Remove Residual Heat 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)(B), Prohibited by Technical Specifications
3352011001R00 - NRC Website

text

FFPL Florida Power & Light Company, 6501 S. Ocean Drive, Jensen Beach, FL 34957 October 20, 2011 L-2011-454 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Re:

St. Lucie Unit I Docket No. 50-335 Reportable Event: 2011-001 Date of Event: August 22, 2011 Unit 1 Manual Reactor Trip Due To High Condenser Backpressure Caused by Severe Influx of Jellyfish into the Intake Structure The attached Licensee Event Report 2011-001 is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event.

Very truly yours, Richard L. Anderso Site Vice President St. Lucie Plant RLA/dlc Attachment an FPL Group company

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 11o-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 learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the FOIA/Privacy Section (T-5 F53), U.S. Nuclear LICENSEE EVENT REPORT (LER)

Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to infocollects.resourse@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an 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.

3. PAGE St. Lucie Unit 1 05000335 1 OF 3

4. TITLE Unit 1 Manual Reactor Trip Due To High Condenser Backpressure Caused by Severe Influx of Jellyfish into the Intake Structure

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

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

M IFACILITY NAME DOCKET NUMBER 08 22 2012 2011 -

001 -

00 10 20 2011j

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)

[] 20.2201(b)

[l 20.2203(a)(3)(i)

[E 50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii)

[1 20.2201(d)

El 20.2203(a)(3)(ii)

El 50.73(a)(2)(ii)(A)

El 50.73(a)(2)(viii)(A)

El 20.2203(a)(1)

El 20.2203(a)(4)

[] 50.73(a)(2)(ii)(B)

[3 50.73(a)(2)(viii)(B)

__ 20.2203(a)(2)(i)

E] 50.36(c)(1)(i)(A)

El 50.73(a)(2)(iii)

El 50.73(a)(2)(ix)(A)

10. POWER LEVEL El 20.2203(a)(2)(ii)

El 50.36(c)(1)(ii)(A)

Z 50.73(a)(2)(iv)(A)

El 50.73(a)(2)(x)

El 20.2203(a)(2)(iii)

El 50.36(c)(2)

[I 50.73(a)(2)(v)(A)

El 73.71(a)(4) 89 20.2203(a)(2)(iv)

[I 50.46(a)(3)(ii)

El 50.73(a)(2)(v)(B)

[3 73.71(a)(5) 89%

El 20.2203(a)(2)(v)

El 50.73(a)(2)(i)(A)

[E 50.73(a)(2)(v)(C)

El OTHER El 20.2203(a)(2)(vi)

El 50.73(a)(2)(i)(B)

El 50.73(a)(2)(v)(D)

Specify in Abstract below or in Analysis of Safety Significance All safety related systems functioned as designed.

The plant response to the event was a manual reactor trip due to high backpressure-low vacuum.

The automatic turbine vacuum trip set point was never reached and conservative measures were taken before reaching automatic set points.

The plant was not at full power when the events occurred and a complete loss of condenser cooling did not occur.

There were no safety system actuations as a result of the trip.

Given the response of the plant and actions taken, the health and safety of the public was not affected by this event.

Over a period of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> upon reactor trip, the conditional core damage probability (CCDP) and conditional large early release probability (CLERP) would reach 1.81E-09 and 1.55E-11, respectively.

These values are significantly below the threshold required by Regulatory Guide 1.174 for the risk to be "small" where CDP is below 1.OE-06 and LERP is below 1.OE-07.

This event is reportable under the requirements of 10 CFR 50.73(a) (2) (iv) (A) due to manual reactor protection system (RPS) actuation.

Corrective Actions

The corrective actions and supporting actions listed below are entered into the site corrective action program.

Any changes to the actions will be managed under the corrective action program.

1. Revise the circulating water off normal procedures to establish that the station will conduct a pre-emptive rapid downpower to the affected unit(s) in the event of a jellyfish, sea grass, or intake intrusion event that is occurring and meeting the specific criteria.

2.

Implement a design change to both St. Lucie units to upgrade existing traveling water screens to increase the capacity to help prevent future unplanned downpowers due to jellyfish and sea grass intrusion.

3.

Revise the intake intrusion monitoring and mitigation procedural guidance to include additional mitigation equipment checks and revise the threat assessment guideline to update action levels and response direction to reflect risk levels associated with the intrusion rate.

Similar Events

A search was performed using an industry database from 2006 to present.

Results identified five events similar to the circumstances of this jellyfish intrusion event.

A similar theme was challenges to traveling water screens required the tripping of circulating water pumps and down powering or tripping of the unit as a result of the decreased flow of circulating water.

Common corrective actions included procedure upgrades to reflect risk and actions to mitigate such a threat, increased monitoring and sampling.

Failed Components lB main feed pump lB condensate pump discharge check valve 1A2 traveling water screen