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Proposed License Request, Technical Specification Task Force (TSTF) Traveler TSTF-523, Revision 2, Generic Letter 2008-01, Managing Gas Accumulation, Response to Request for Additional Information
	ML16029A078
Person / Time
Site:	Surry
Issue date:	01/25/2016
From:	Mark D. Sartain; Virginia Electric & Power Co (VEPCO)
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	15-330B, GL-2008-01
	Download: ML16029A078 (11)
	v • d • e

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 January 25, 2016 10CFR50.90 U. S. Nuclear Regulatory Commission Serial No.: 15-330B Attention:

Document Control Desk NL&OS/GDM:

R2 Washington, DC 20555-0001 Docket Nos.: 50-280 50-281 License Nos.: DPR-32 DPR-37 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITSI1 AND 2 PROPOSED LICENSE AMENDMENT REQUEST TECHNICAL SPECIFICATION TASK FORCE (TSTF) TRAVELER TSTF-523.REVISION 2. "GENERIC LETTER 2008-01. MANAGING GAS ACCUMULATION" RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION By letter dated January 14, 2015 (Serial No.14-485), Virginia Electric and Power Company (Dominion) submitted a license amendment request (LAR) to add a Technical Specifications (TS) Surveillance Requirement (SR) to verify the Surry Power Station (Surry) Units 1 and 2 Safety Injection (SI) Systems' locations susceptible to gas accumulation are sufficiently filled with water. The proposed change addresses the concerns discussed in Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems." The proposed amendment is consistent with Technical Specification Task Force (TSTF)Traveler TSTF-523, Revision 2, "Generic Letter 2008-01, Managing Gas Accumulation." By letters dated August 19 and December 3, 2015 (Serial Nos.15-330 and 15-330A, respectively), Dominion responded to requests for additional information (RAI) from the NRC technical review staff. On December 23, 2015, Ms. Karen Cotton Gross (NRC Project Manager for Surry) sent an email to Dominion requesting additional information to facilitate the NRC review of the LAR. The requested information is provided in the attachment.

As discussed during a conference call on January 7, 2016, NRC and Dominion agreed that a response to Question No. 3 was no longer required as it would be adequately addressed by the information being provided in response to the remaining questions.

The information provided in this letter does not affect the conclusions of the significant hazards consideration or the environmental evaluation included in the January 14, 2015 LAR.Sptf1 Serial No. 15-330B Docket Nos. 50-280/281 Page 2 of 3 Should you have any questions or require additional information, please contact Mr. Gary D. Miller at (804) 273-2771.Respectfully, Mark 0. Sartain Vice President

-Nuclear Engineering Commitments contained in this letter: None

Attachment:

Response to NRC Amendment Request, TSTF-523, Revision Accumulation" Request for Additional Information

-License Technical Specification Task Force (TSTF) Traveler 2, "Generic Letter 2008-01, Managing Gas' .NOTAr~y PUBLIC -Comrnonw~lMth or Vir'ginia

_l* ~~Reg. # .140542 .. My Commission 31, 2058 COMMONWEALTH OF VIRGINIA)))COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Mr. Mark D. Sartain, who is Vice President

-Nuclear Engineering, of Virginia Electric and Power Company. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that company, and that the statements in the document are true to the best of his knowledge and belief.Acknowledged before me this d2I"" day * ,t 2016.My Commission Expires: --5 3i I -Notary Public Serial No. 15-330B Docket Nos. 50-280/281 Page 3 of 3 cc: U.S. Nuclear Regulatory Commission

-Region II Marquis One Tower 245 Peachtree Center Avenue, NE Suite 1200 Atlanta, GA 30303-1257 State Health Commissioner Virginia Department of Health James Madison Building -7 th floor 109 Governor Street Suite 730 Richmond, VA 23219 Ms. K. R. Cotton Gross NRC Project Manager- Surry U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G-9A 11555 Rockville Pike Rockville, MD 20852-2738 Dr. V. Sreenivas NRC Project Manager -North Anna U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G-9A 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Surry Power Station Serial No. 15-330B Docket Nos. 50-280/281 Attachment RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST. TECHNICAL SPECIFICATION TASK FORCE (TSTF) TRAVELER TSTF-523.

REVISION 2. "GENERIC LETTER 2008-01, MANAGING GAS ACCUMULATION" Virginia Electric and Power Company (Dominion)

Surry Power Station Units I and 2 Serial No. 15-3308 Docket Nos. 50-280/281 Attachment Page 1 of 7 Response to NRC Request for Additional Information License Amendment Request. Technical Specification Task Force (TSTF) Traveler TSTF-523.

Revision 2. "Generic Letter 2008-01. Managing Gas Accumulation" Surry Power Station Units I and 2 By letter dated January 14, 2015 (Serial No.14-485), Dominion submitted a license amendment request (LAR) to add a Technical Specifications (TS) Surveillance Requirement (SR) to verify the Surry Power Station (Surry) Units 1 and 2 Safety Injection (SI) Systems' locations susceptible to gas accumulation are sufficiently filled with water. By letters dated August 19 and December 3, 2015 (Serial Nos.15-330 and 15-330A, respectively), Dominion responded to requests for additional information (RAI)from the NRC technical staff. On December 23, 2015, Ms. Karen Cotton Gross (NRC Project Manager for Surry) sent an email to Dominion requesting additional information to facilitate the NRC review of the LAR. The requested information is provided below.As discussed during a conference call on January 7, 2016, NRC and Dominion agreed that a response to Question No. 3 was no longer required as it would be adequately addressed by the information being provided in response to the remaining questions.

1. The December 3, 2015 Dominion document stated that the containment spray (CS)suction piping from the refueling water storage tank (RW.ST) involved in the quarterly pump tests consisted of a 4 ft horizontal pipe, a 6 ft vertical downward pipe, a 20 ft horizontal pipe, a 20 ft vertical upward pipe, and a 5 ft horizontal pipe for a total of 43 ft. The stated 43 ft total appears to be inconsistent with the individual lengths.Please explain.Dominion Response The 20 feet vertical upward pipe length noted in the response to Question No. 1 in Dominion's December 3, 2015 letter should have been 8 feet. The corrected configuration of the CS pump suction piping from the RWST is as follows: a horizontal run of 4 feet, a vertical downward run of 6 feet, a horizontal run of 20 feet, a vertical upward run of 8 (versus 20) feet, and a horizontal run of 5 feet for a total of 43 feet. As noted in the December 3, 2015 letter, these dimensions are approximate.

2. The December 3, 2015 Dominion document stated that a Froude number (NFR) >0.55 was sufficient to sweep any gas out of the system during tests. This is consistent with the NRC safety evaluation (SE) of NEI 09-10 for horizontal and connected vertically upward pipes, but is inconsistent for a downcomer, where NEI 09-10 and the SE concluded that NFR < 0.8 may not remove gas. A similar observation applies to the Dominion NFR = 0.75 statement.

Please address these observations with respect to the Dominion conclusions that the CS quarterly tests will sweep gas voids out of the system. See also Item 5, below, and describe the flow path involved in the quarterly tests.

Serial No. 15-330B Docket Nos. 50-280/281 Attachment Page 2 of 7 Dominion Response As stated in Dominion's Nine-Month Response to Generic Letter 2008-01, dated October 14, 2008 (Serial No. 08-0013B), regarding the CS system: "During normal operation the entire CS pump suction line and the discharge line up to the normally closed isolation motor-operated-valve (MOV) are maintained sufficiently full of water at RWST head. Return to service and/or quarterly IST[in-service testing] of the pumps at design basis flow further ensures that the CS pump suction piping is maintained full immediately following return to service and/or quarterly IST flow testing. There are no external sources for gas to be introduced into the CS system on either the pump suction or discharge side during normal operation.

In conclusion, the CS pump suction lines are not susceptible to gas accumulation or entrainment, and the CS pumps are not susceptible to gas intrusion." Since the RWST is not drained below the RWST CS suction downward turned elbow, there is no mechanism for gas to be introduced into the system. Additionally, due to RWST head pressure, there is no degassing, and the solubility effects bound potential temperature increase effects.The return-to-service procedure and system quarterly tests are performed to ensure design functionality and performance.

While the tests provide a minimum NFR of 0.75 in the suction piping, versus the NEI 09-10 acceptance criteria value of 0.80, no gas intrusion mechanism exists for the CS systems, and even if any gas voids were to exist in the system following the return-to-service and/or quarterly tests, they would be of negligible size.A sketch of the general layout of the CS suction piping configuration is shown in Figure 1 below.CS Pump RWST Suction Figure 1 Containment Spray Suction Piping Configuration Serial No. 1 5-330B Docket Nos. 50-280/281 Attachment Page 3 of 7 If a gas intrusion mechanism were present, the only location that voids could plausibly exist would be between the two elbows in the short horizontal piping.However, turbulence would occur inside the piping due to the short horizontal piping connected to the entrance elbow and the subsequent downward turned elbow. Even though the minimum postulated NFR is 0.05 below the NEI 09-10 acceptance criteria value, which equates to ~100 gpm, the void would be negligible following either return-to-service or quarterly testing.A review of the recent CS system test data from November 2015 provided in the table below indicates the CS system flow rate is approximately 1600 gpm (the lowest measured flow rate was 1586.5 gpm, NFR=0.7 9 4), which would be sufficient to sweep gas and prevent gas accumulation.

CS Pump Test Sat Range Total Flow Rate NFR Mark Number (gpm) (gpm) (Dimensionless) 1-CS-P-lA 1520 to 1636 1586.5 0.794 1-CS-P-ilB 1520 to 1640 1596.9 0.799 2-CS-P-l1A 1520 to 1839 1676.0 0.838 2-CS-P-lB 1530 to 1870 1676.0 0.838 3. The December 3, 2015 Dominion document stated that the flow rate during the CS system quarterly test was 1500 gpm with NFR = 0.75. Maximum assumed CS system flow rate from the RWST following a large loss-of-coolant accident (LOCA) is 4500 gpm to which must be added a safety injection (SI) system flow rate of perhaps 2500 gpm for that part of the suction piping where flow is shared from the RWST.This appears to result in a condition where the system quarterly test may not remove a high point void at the RWST exit pipe but flow initiation following a large break L OCA would move the void toward the SI and CS pumps. Please address this potential condition.

Include actions to eliminate the void following an outage that may have resulted in void generation.

Dominion Response As discussed during the January 7, 2016 conference call, NRC and Dominion agreed that a response to Question No. 3 was no longer required as each CS pump has a separate suction tap from the RWST, and the Safety Injection (SI) System has a separate and independent suction tap. This configuration is shown in Figure 2 below.

Serial No. 1 5-330B Docket Nos. 50-280/281 Attachment Page 4 of 7 Figure 2 Refueling Water Storage Tank 4. The flow diagrams and related drawings, including information provided in the December 3, 2015 Dominion document, are not sufficient for the Reactor Systems Branch staff to evaluate the void-related information that Dominion has provided.Therefore, please provide isometric drawings that include all valves and piping high points that are identified in the Dominion documents submitted in relation to the TSTF-523 license amendment request. Include the suction piping configuration inside the RWS T.Dominion Response As discussed during the January 7, 2016 conference call, Dominion's response to GL 2008-01 provided the results of the plant system analyses performed by Dominion for those systems subject to GL 2008-01. The NRC technical staff reviewed the GL 2008-01 response documentation, determined that Dominion had acceptably addressed the GL requests, and indicated the only portion of Serial No. 1 5-330B Docket Nos. 50-280/281 Attachment Page 5 of 7 Question No. 4 requiring a response is the last sentence. (Reference NRC letter dated August 12, 2011; ML110880718)

The suction piping configuration inside the RWST for each CS pump has a downward turned elbow with an enlargement nozzle as shown in the picture provided below.Containment Spray Pump Suction Piping in RWST The SI System pumps' suction piping connection is a pipe welded to the RWST wall with no interior piping.5. Does the normal reactor coolant system (RCS) makeup process result in an SI system pressure that prevents RCS and accumulator back-leakage into the SI system?Dominion Response The SI System lines are designed to independently connect to the RCS System as indicated in the bottom right corner of Figure 3 below. Each RCS loop has a separate accumulator line connection independent of the High Head Safety Injection (HHSI) and Low Head Safety Injection (LHSI) lines connected to the RCS loop.

Serial No. 15-3308 Docket Nos. 50-280/281 Attachment Page 6 of 7 Consequently, the accumulators cannot cause back-leakage into the rest of the SI System.Each accumulator is connected to the RCS by a 12-inch line that includes an MOV and two in-series swing check valves. During normal RCS operation (above 1000 psig), the MOV is opened and its associated breaker is locked open with the power removed. Each accumulator contains a minimum of 975 cubic feet of borated water and is pressurized to at least 600 psia with nitrogen.

The two swing check valves in each accumulator's injection line prevent back-leakage from the higher pressure RCS into the accumulators.

As stated in the response to Question 4 in Dominion letter dated December 3, 2015 (Serial No. 15-330A), accumulator level is trended to verify there is no leakage from the RCS into the accumulators.

The LHSI and HHSI pumps both discharge into each RCS loop through a 6-inch line that includes multiple check valves and MOVs. At Surry, the centrifugal charging pumps also serve as the HHSI pumps. The discharge pressure from the charging pumps is approximately 2500 psig during charging operations to ensure flow can be initiated through the charging lines into the RCS system, which is pressurized to 2235 psig. The HHSI lines are not flowed during normal charging operations because the HHSI isolation valves are closed. Since the normal charging and HHSI lines are pressurized above RCS pressure, RCS back-leakage into these lines cannot occur.The LHSI pumps do not initiate flow into the RCS unless RCS pressure is below 200 psig. Since the LHSI System pressure is maintained below the pressure of the RCS, the LHSI pumps' discharge lines are protected from RCS back-leakage by two in-series swing check valves. Surry performs quarterly ultrasonic testing of the LHSI pumps' discharge lines to check for potential gas accumulation.

The proposed TS surveillance primarily addresses this section of piping.

Serial No. 1 5-330B Docket Nos. 50-280/281 Attachment Page 7 of 7 Hots Logs~-I-~*-k From RHR t -. c Figure 3 Safety Injection System VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 January 25, 2016 10CFR50.90 U. S. Nuclear Regulatory Commission Serial No.: 15-330B Attention: