ML20043G873

Discusses Evaluation of ASME Section XI Testing for Outside Recirculation Spray Pumps

ML20043G873
Person / Time
Site:	North Anna
Issue date:	06/14/1990
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
90-247A, NUDOCS 9006210218
Download: ML20043G873 (3)

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• 1 VIHOINIA El.I;CTHIC ANI) POWi!H COMI'ANY HIrllMONI),YIHulNI A 200 61 June 14,1990 U.S. Nuclear Regulatory Commission Serial No.

90 247A Attention: Document Control Desk NES/lSI/EWT R2 Washington, D.C. 20555 Docket No. 50 338 50 339 License No. NPF 4 NPF-7 ~ Gentlemen: VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITC 1 AND 2 OUTSIDE RECIRCULATION SPRAY PUMP TESTING EVALUATION OF ASME SECTION XI TESTING REQUIREMENTS Our letter (Serial No. 90 247),- dated April 30,1990, identified concerns with the approved ASME Section XI testing program for the outside recirculation spray pumps. Correspondingly, we committed to perform an evaluation of the effects of flow testing the pumps on their recirculation test loops. Four areas of concern were evaluated. The first area of concern was that flow testing the pumps using the recirculation test loop produces a pressure surge-which is thought to be linked to damage found in the - expansion joint on the discharge side of the pump. A pressure surge occurs when the pump is started. As part of our evaluation, two recirculation flow tests have been-performed on the Unit 2 pumps. In preparatien for the first test, the test loop was filled and vented to a high point vent in an effort to eliminate as much air as possible from-the test loop. Also, the throttle valve on the test line was opened two turns prior to pump startup. The test results demonstrated a significant reduction in the pressure surge (from a peak pressure of 265 psig recorded during an earlier test in which the test loop was vented at a lower point to 191 psig). For the second test, the test loop was verified filled and vented to the high point vent and.the throttle valve was fully opened prior to pump startup. This test resulted in a peak pressure of 158 psig. By carefully filling and venting the test loop and starting with a full open throttle valve, . flow-testing the pumps using the recirculation test loop should not-damage the expansion joints. Therefore, we will perform quarterly testing on these pumps utilizing this testing procedure. The expansion joints,will continue to be monitored for damage.

If damage is detected as the result of the quarterly testing, a design modification will be considered.

The second area of concern was whether the benefits of quarterly Section XI testing are outweighed by the risks of pump degradation through frequent testing of a system that is maintained dry during normal plant operation; This issue is being addressed by (1 90062102'18 900614 i PDR ADOCK 0500o338 P PDC l\\\\

3 :%. 9 L the OM 6 working group on pump testing. There may be a Code change to allow less frequent testing for this type of pump system. We will continue to monitor the progress of the OM 6 working group. The third concern was associated with the limited inventory within the test loop. If the pump is allowed to run too long, excessively high pressures due to heatup can be produced in the closed test loop. Reducing the hydraulic stabilization period from five-r minutes, as required by the Code, to two minutes will help ensure that heatup problems do not occur. Also, because of the limited Inventory, the system stabilizes quickly and a five minute period is not necessary. Therefore, Relief Request P 7 has been revised to request a two minute stabilization period. A copy of Relief Request P-7 is attached for your review and approval, t Except for the two minute stabiltation period, the testing procedures for the outside recirculation spray pumps will be revised in accordance with Relief Request P 7 prior to the next scheduled test. When NRC approval is obtained for the two minute. stabilization period, the procedure will be changed appropriately. The final area of concern is associated with commonality of the testing programs for the outside recirculation spray pumps between the stations. Surry Power Station is currently performing the quarterly testing in accordance with Section XI. Accordingly, Surry is running the pumps for five minutes for stabilization prior to taking data. We are continuing to evaluate the need for a relief request for Surry to reduce the five minute stabilization period. Also, if the frequency of testing is decreased by changes to the OM-6 Code, we will consider submitting a program change for Surry Power Station. Should you require any additional information or have any questions regarding this submittal, please contact us. Very truly yours, s . W. L. Stewart Senior Vice President - Nuclear . Enclosure cc: U.S. Nuclear Regulatory Commission Region ll 101 Marietta Street, N.W. Suite 2900 Atlanta, Georgia 30323 Mr. M. S. Lesser NRC Senior Resident inspector North Anna Power Station

y Q p Q$ W ~ t ~ RELIEF REQUEST P-7 1. IDENTIFICATION OF COMPONENTS

System.

Recirculation Spray. Pump (s) 1-RS-P-2AT 1-RS P-2B 2-RS-P 2A 2 RS P-28 y Class'- 2 ~ ; -i ' 11. IMPRACTICAL COD'E REQUIREMENTS

Each pump shall be run at least five minutes under conditions as stable as the a

' system permits prior to measuring the test quantities.

Measure inlet pressure and differential pressure.

6 -111. BASIS FOR RELIE'F ~' The test loop for these pumps contains a small volume of water. A four inch test recirculation line branches off the ten inch pump discharge line a short distance from the pump. The recirculation line discharges into the sump which is a - cylinder approximately 50 feet deep and two feet in diameter. Because of the small volume in the test loop, the hydraulic' parameters stabilize quickly.

Therefore, a five minute stabilization period is not necessary to achieve repeatable test results.-

~ L-In addition,'if the pump is run for too long of a period, the water will heatup due to - the limited water volume. This heatup can lead to excessive pressures in the test - loop'. The recirculation path will be filled with water to establish ~ lnitial conditions for' testing. Inlet pressure remains constant for the test loop from test to test, therefore, any change in differential pressure will'be directly indicated by -h mondoring pump discharge pressure. [ IV. ALTERNATE TESTING gJ (' These pumps will be flow tested on their recirculation paths every quarter. After a two minute stabilization period, discharge pressure (instead of differential l pressure), flow rate and vibration measurements will be taken. f; p 'o l { ; ' } :. ' ' ,1/1 i ,}}