ML11255A191

Voluntary Special Report - Seismic Monitoring Instrumentation Actuation

ML11255A191
Person / Time
Site:	Limerick
Issue date:	09/02/2011
From:	Maguire W Exelon Nuclear
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TRM 3.3.7.2
Download: ML11255A191 (8)

Text

Exelono, Limerick Generating Station www.exeloncorp.com 3146 Sanatoga Rd.

NuClear Pottstown, PA 19464 TRM 3.3.7.2 September 2, 2011 U.S. Nuclear Regulatory Commission Attn.: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Units 1 and 2 Facility Operating License Nos. NPF-39 and NPF-85 NRC Docket Nos. 50-352 and 50-353

Subject:

Voluntary Special Report - Seismic Monitoring Instrumentation Actuation This voluntary Special Report is being submitted due to an actuation of seismic monitoring instrumentation during a seismic event. The event did not exceed the 0.01 g Technical Requirements Manual 3.3.7.2 Seismic Monitoring Instrumentation surveillance requirement 4.3.7.2.2 threshold for reporting.

Technical Requirements Manual 3.3.7.2 Seismic Monitoring Instrumentation surveillance requirement 4.3.7.2.2 states the following:

Each of the above required seismic monitoring instruments which is accessible during power operation and which is actuated during a seismic event greater than or equal to 0.01g, and which does not self-reset, shall be restored to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and a CHANNEL CALIBRATION performed within 5 days following the seismic event. Data shall be retrieved from actuated instruments and analyzed to determine the magnitude of the vibratory ground motion. A Special Report shall be prepared and submitted to the Nuclear Regulatory Commission pursuant to Specification 6.9.2 of the Technical Specifications within 10 days describing the magnitude, frequency spectrum and resultant effect upon unit features important to safety.

Seismic Event Description On Tuesday, August 23, 2011, Unit 1 and Unit 2 were operating at full power when the "Seismic Monitor System Recording Activated" alarm annunciated among numerous other alarms. Also, the licensed operators in the main control room felt the vibrations.

The licensed operators entered procedure SE-5, Earthquake.

Seismic Event Magnitude The magnitude of the earthquake of August 23, 2011 was 5.8 (Moment Magnitude) at the epicenter in Mineral, Virginia.

Seismic Monitoring Instrumentation Actuation Docket Nos. 50-352 and 50-353 September 2, 2011 Page 2 The Peak Ground Acceleration values (See Attachment 1) recorded for the Primary Containment Foundation Sensor Array (XE-VA-102) located on the Unit 1 Elevation 177' HPCI Pump Room floor were:

Longitudinal Axis = -0.0049 g Vertical Axis = -0.0061 g Transverse Axis = -0.0048 g The OBE criteria was not exceeded (0.075g horizontal and 0.050g vertical)

Seismic Event Frequency Spectrum The spectral acceleration analysis was performed by the Seismic Monitoring System response spectrum analyzer (XR-VA-109) and reviewed by Engineering.

The operating basis design response spectrum was not exceeded. Attachment 2 illustrates that the response spectra generated from the ground motion time history (solid line discernable from the x-axis) was significantly lower than the operating basis design limit (dashed-line).

Resultant effect upon unit features important to safety Limerick safety system inspections and accessible area walkdowns were performed in accordance with station event response guidelines, severe weather and natural disaster guidelines and post transient walkdown procedures. No indications of adverse effects on features important to safety were identified. Event identification and actions taken are documented in the Limerick Corrective Action Process system under Issue Report 1254561.

There are no regulatory commitments contained in this letter.

If you have any questions, please contact John Hunter at (610) 718-3400.

Sincerely, William F. Maguire Vice President - Limerick Generating Station Exelon Generation Company, LLC Primary Containment Foundation Peak Acceleration Primary Containment Foundation Frequency Spectrum cc: Administrator, Region I, NRC NRC Senior Resident Inspector, Limerick Primary Containment Foundation Peak Acceleration

_CORDER A (S/N 31241)

PEAKS (g):

1: -0.0049 2: -0.0061 3: -0.0048 ent #002: 08/23/2011 12:54:13 PRIMARY CONTAINMENT FOUNDATION 0.0 0 7

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