NL-14-0308, Southern Nuclear Operating Company Response to the Request for Additional Information Regarding ISI Program Alternative VEGP-ISI-ALT-10, Version 1

Southern Nuclear Operating Company Response to the Request for Additional Information Regarding ISI Program Alternative VEGP-ISI-ALT-10, Version 1

ML14059A352
Person / Time
Site:	Vogtle
Issue date:	02/28/2014
From:	Pierce C Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-14-0308, VEGP-ISI-ALT-10, Version1.
Download: ML14059A352 (11)

Text

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

40 Inverness Center Parkway Post Office Box 1295 Birmingham, Alabama 35201 Tel 205.992.7872 Fax 205.992.7601 SOUTHERN << \

February 28, 2014 COMPANY Docket Nos. : 50-424 NL-14-0308 50-425 U.S. Nuclear Regulatory Commission A TIN: Document Control Desk Washington , D. C. 20555-0001 Vogtle Electric Generating Plant - Units 1 & 2 Southern Nuclear Operating Company Response to the Request for Additional Information Regarding lSI Program Alternative VEGP-ISI-ALT-10. Version 1 Ladies and Gentlemen:

By letter dated January 16, 2014, (Agency-Wide Documents Access and Management System (ADAMS) Accession Number ML14016A488) Southern Nuclear Operating Company (SNC) submitted a request for approval of an American Society of Mechanical Engineers (ASME)Section XI code alternative for the leakage examination of the Class 2 reactor vessel flange leak-off piping for both Units 1 and 2 of the Vogtle Electric Generating Plant (VEGP).

Subsequently, by letter dated February 19, 2014, (ADAMS Accession Number ML14042A416}, the U. S. Nuclear Regulatory Commission (NRC) submitted a Request for Additional Information (RAI) to enable completion of their review. to this letter provides SNC's response to the RAI. Enclosure 2 and to this letter includes piping isometric drawings and a sketch representative of the reactor pressure vessel leak-off piping layout, respectively, to aid understanding of the response.

This letter contains no NRC commitments. If you have any questions, please contact Ken McElroy at (205) 992-7369.

Respectfully submitted ,

Cl?.~

C. R. Pierce Regulatory Affairs Director CRP/CLN/Iac

U. S. Nuclear Regulatory Commission NL-14-0308 Page2

Enclosures:

1. Response to Request for Additional Information

2. Unit 1 and Unit 2 Piping Isometric Drawings

3. Representation of RPV Leak-Off Piping Layout cc: Southern Nuclear Operating Company Mr. S. E. Kuczynski, Chairman, President & CEO Mr. D. G. Best, Executive Vice President & Chief Nuclear Officer Mr. T. E. Tynan , Vice President- Vogtle 1 & 2 Mr. B. L. lvey, Vice President- Regulatory Affairs Mr. D. R. Madison, Vice President- Fleet Operations Mr. B. J. Adams, Vice President-Engineering RType: CVC7000 U.S. Nuclear Regulatory Commission Mr. V . M. McCree, Regional Administrator Mr. R. E. Martin, NRR Senior Project Manager- Vogtle 1 & 2 Mr. L. M. Cain , Senior Resident Inspector- Vogtle 1 & 2

Vogtle Electric Generating Plant- Units 1 & 2 Southern Nuclear Operating Company Response to the Request for Additional Information Regarding lSI Program Alternative VEGP-ISI-ALT-1 0, Version 1 Enclosure 1 Response to Request for Additional Information to NL-14-0308 Response to Request for Additional Information This enclosure contains the response to the NRC request for additional information (RAI) regarding SNC's request for approval of an American Society of Mechanical Engineers (ASME)Section XI Code alternative for the leakage examination of the Class 2 reactor vessel flange leak-off piping for both Units 1 and 2 of the Vogtle Electric Generating Plant (VEGP). The response is formatted so that the NRC RAI is quoted first with the SNC response immediately following.

NRC RAI1 Describe any incidents of significant RPV flange 0-ring leakage at the VEGP.

SNC Response Vogtle has not experienced any incidents of significant RPV flange o-ring leakage in its previous years of operation.

NRC RAI2 In order for a VT-2 visual examination for leakage to be effective, the lines must be purged of air. Describe the procedure for ensuring that the lines are water-solid prior to the beginning of the four hour pressurization hold time.

SNC Response There are no vents near the top elevation of the piping that would allow venting of air in the pipe. The only location to permit venting without performing a design modification, is located on the lowest section of the piping. The 089 valve is the only location where venting can be performed. This valve and location can be seen within Enclosure 2 and Enclosure 3 of the proposed alternative submittal dated January 16, 2014 (ADAMS Accession Number ML14016A488), in coordinates A5 and A3, respectively. Additionally, this valve is circled on the drawings in Enclosure 2 to this letter.

To ensure the piping is water solid prior to the beginning of the four-hour pressurization hold time, the blind flange downstream of the 089 valve will be removed and the 089 valve will be opened allowing water to flow from the piping.

The flow of water will be allowed for approximately five minutes. Once a steady stream of water is obtained, the 089 valve will be closed and the blind flange will be reinstalled. This evolution is expected to purge the piping of air since this will draw water from the refueling cavity to flush out air. In addition, in the time it takes to fill the refueling cavity to 23ft above the RPV flange, the flow of water through the pipe, coupled with air's buoyancy, will allow air to exit the piping through the top of the RPV flange, which is open to the atmosphere.

With this process, there is the potential for small pockets of air to be trapped in the piping. However, if a through-wall indication exists at the same location of an air pocket, eventually the air would leak out, allowing the water to leak out as well.

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Enclosure 1 to NL-14-0308 Response to Request for Additional Information The above process for filling the RPV flange leak-off piping will help ensure the piping is water solid prior to the four hour pressurization hold time.

NRC RAI3 When there is leakage past the inner 0-ring and the valve on the inner 0-ring leakage line closed, the inner 0-ring leakage line between the RPV flange and the closed valve will be pressurized to the reactor operating pressure, 2235 psig, and a VT-2 visual examination could be performed at that time. Describe plans for performing an examination of the subject line while pressurized to reactor operating pressure. If an examination is not planned , provide justification, including description of any hardship associated with performing an examination.

SNC Response As indicated in the proposed alternative submitted with a letter date of January 16, 2014 (ADAMS Accession Number ML14016A488), if leakage through the inner o-ring leak-off piping is confirmed, operators will close the valve to the inner o-ring leak-off piping and open the isolation valve on the outer o-ring piping to permit the detection of the leakage past the outer o-ring gasket. The operation of these valves is controlled through VEGP Annunciator Response Procedure 17012-1/2.

There is approximately 16 feet of piping on both units that is visually accessible outside the bioshield. This piping can be visually examined with relative ease while at power operations. This section of piping contains the two valves that must be manipulated to isolate or un-isolate the o-ring leak-off piping.

Annunciator Response Procedures 17012-1 and 17012-2 are being revised to have Operations personnel perform a visual examination (non-VT-2) for leakage of the accessible portions of the line ten minutes after line isolation. This section of piping is highlighted in blue under Enclosure 2 and 3 of the proposed alternative submittal (ADAMS Accession Number ML14016A488).

Qualified VT-2 examiners will also perform a VT-2 examination after a minimum hold time of four hours. The VT-2 examination will be limited to those portions of the boundary outside the bioshield and to those portions of the piping which can be viewed from the entrance to inside the bioshield, which is a locked cage door.

Methods of examination described in IWA-5241 (b) will be utilized for the areas that can be seen through the cage doors for observance of any evidence of leakage. The cage doors will not be opened for the examinations. Dose rates inside the bioshield are expected to be greater than 1 REM/hr gamma and 1REM/hr neutron during power operations. Taking ALARA principles into consideration, entry into the bioshield is not justified for the performance of the VT-2 examination. A representation of the layout for the RPV leak-off piping ,

along with references to the bioshield wall and cage doors, which is typical for both units 1 and 2, has been included in Enclosure 3 to aid in the understanding of the piping's layout.

To summarize , if a time arises when RPV flange leakage is experienced through the inner o-ring leak-off piping and isolation valve manipulation is required ,

E1- 2 to NL-14-0308 Response to Request for Additional Information Operations personnel will perform a non-qualified visual examination of the piping outside the bioshield ten minutes after completion of valve manipulation.

Following examination by Operations personnel, qualified VT-2 examiners will perform a visual examination of the accessible piping outside the bioshield and will perform a visual exam through the cage doors looking for evidence of leakage utilizing methods described in IWA-5241 (b). VT-2 examiners will perform examinations after a minimum hold time of four hours.

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