ML18152B421

Forwards Rev 1 to Relief Request P-11 to Clarify Original Intent of Request by Specifically Requesting Relief from Requirements of Section 6.1 of OM-6

ML18152B421
Person / Time
Site:	Surry
Issue date:	05/25/1999
From:	Hartz L VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
99-255, NUDOCS 9906030296
Download: ML18152B421 (6)

Text

e e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261

. '* May 25, 1999 United States Nuclear Regulatory Commission Serial No.: 99-255 Attention: Document Control Desk NL&OS/GDM: R1' Washington, D. C. 20555 Docket No.: 50-280 License No.: DPR-32 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 1 ASME SECTION XI RELIEF REQUEST By letter dated December 18, 1998, the NRC provided a Safety Evaluation that authorized incorporation of revised Relief Request P-11, Revision 1, into the Virginia Electric and Power Company Surry Unit 1 lnservice Testing (1ST) Program for Pumps and Valves.

After reviewing the Safety Evaluation, we have determined that a revision to Relief Request P-11 is required to clarify the original intent of the request. Specifically, the NRC stated in Section 3.3 of the referenced Safety Evaluation that since the request for relief did not specifically identify that we were requesting relief from the requirements of Section 6.1 of OM-6, we were required to comply with these Code requirements "using the revised test frequency and hydraulic acceptance criteria approved by this SE."

Section 6.1 of OM-6 requires that the pump test frequency be doubled if deviations fall within the "alert" range. The nominal Code test frequency requirement for the Emergency Service Water (ESW) pumps is once every three months. Consequently, doubling the test frequency if a pump falls into the "alert" range would require testing the pump once every one and one-half months. However, in the approved Relief Request P-11, we had already committed to testing the ESW pumps every month, which is more frequent than the accelerated 1:Y2 month test frequency required by the Code when pump flow or vibration measurements fall within the "alert" range. Pursuant to the NRC Safety Evaluation, we are required to double the monthly test frequency if deviations fall within the "alert" range. Testing the ESW pumps twice a month is unnecessary since

1) we are already testing the pumps more frequently than required by Code for "alert" conditions, and 2) we are effectively trending test data and performing corrective actions, (e.g., cleaning suction bells, impellers and diffusers) to ensure an acceptable level of pump performance and safety is maintained.*

Therefore, pursuant to 10 CFR 50.55a(a)(3)(ii), Relief Request P-11, Revision 1, has been revised and is resubmitted herein for your review and approval. The revised 9906030296 990525 PDR ADOCK 05000280 p PDR __;

request specifically requests relief from the requirements of Section 6.1 of OM-6.

Revrsion* bars located in the right margin indicate the revisions. This request has been approved by the Surry Station Nuclear Safety and Operating Committee.

Very truly yours, L. N. Hartz Vice President- Nuclear Engineering and Services Attachment Commitment Contained in this Correspondence

1. Tests will be conducted every month within the tide level limits of the pump reference curve, and flow will be compared to acceptance criteria based on the reference curve and the ranges provided in this correspondence. For flow rates that fall into the alert range, the test data will be trended and corrective action taken if the trend evaluation determines that the flow will fall below the required action range before the next monthly test.

cc: U.S. Nuclear Regulatory Commission Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. R.A. Musser NRC Senior Resident Inspector Surry Power Station Robert Smith Authorized Nuclear Inspector Surry Power Station I_

RELIEF REQUEST P-11

- ......._ l '

System: Service Water Pump(s): 1-SW-P-1A 1-SW-P-18 1-SW-P-1C Class: 3 OM Part 6 Code Requirements for Which Relief Is Requested OM Part 6, Paragraph 4.3 requires reference values to be points of operation readily duplicated during subsequent tests. All subsequent test results shall be compared to these initial reference values.

OM Part 6, Table 3b, establishes acceptance criteria for vertical line shaft pumps where the acceptable range is (0.95 to 1.10 times the reference flow rate Or), the alert range is (0.93 to <0.950r), and the required action range is (<0.930r and >1.100r).

OM Part 6, Paragraph 6.1 requires that the frequency of testing specified in paragraph 5.1 (i.e., nominally every three months) shall be doubled if deviations fall within the alert range of Table 3.

Basis for Relief from Paragraph 4.3 The emergency service water pumps take suction from the James River and discharge into the intake canal. The James River near the plant is subject to a tide level variation of approximately five feet. Therefore, the total static head for the system can vary from test to test. There are no valves in the lines to throttle flow and to compensate for the change in system static head. The only way to duplicate flow and differential pressure from test to test is to perform the test at the same tide level each time. Trying to perform this test within a small enough tide level range to produce repeatable results has proven impractical. To compensate for the change in total system head, a pump reference curve will be prepared based on test results taken at different tide levels.

Tests will be conducted within the tide level limits of the curve, and results will be compared to acceptance criteria based on the reference curve and the ranges given in OM Part 6, Table 3b. Inlet pressure will be calculated from tide level.

3-18 Revision 1 S1 PVl3R1 March 25, 1999

RELIEF REQUEST P-11 (Cont.)

Basis for Relief from Table 3b The emergency service water pumps are standby pumps that are only operated during periodic tests. The pumps operate at adjusted speeds from 880 to 900 RPM and are driven by diesel engines. The suction bells containing the impellers for these pumps are submerged in the James River to a depth of approximately 9.8 feet. The brackish water of the James River provides a favorable environment for the growth of biological organisms. Between tests, organisms such as hydroids and barnacles attach to the inside of the suction bell and the pump impeller. As these organisms grow the hydraulic performance of the pumps degrades. The period of greatest growth occurs from mid-summer through early fall. During other portions of the year, biological growth does not cause significant degradation.

Surry Power Station has aggressively addressed this problem by coating the inside of the suction bells with antifouling material, by testing the pumps each month and by cleaning the suction bells and impellers when performance is projected to degrade to unacceptable levels before the next monthly test. Divers using specialized equipment clean the inside of the suction bells, the impellers and portions of the diffuser. This cleaning process restores the pumps to almost peak hydraulic performance levels.

In the past, the pumps have been completely removed for cleaning. However, frequent removal of the pumps is not practical because installation and realignment is a difficult and complex evolution. The suction bay has also been drained to allow cleaning of the pumps. This process involved construction of scaffolding, and removal of the suction bell and impeller. Also, any work that is being performed on the pump suction makes the circulating water pump sharing the suction bay with the emergency service water pump unavailable. Draining the suction bay and removal of the pump takes several days. During certain summer periods, all eight circulating water pumps are needed to maintain both units at 100% electric power.

Currently, if the flow rate falls into the alert range of {0.93 to <0.950r) a trend of the degradation rate is performed to determine if the performance will decrease to (<0.930r) before the next monthly test. If so, the divers are called in to clean the suction bell and impeller at a cost of approximately $4,000 per pump.

3-19 Revision 1 S1 PVl3R1 March 25, 1999 I_

RELIEF REQUEST P-11 (Cont.)

\ ',

Experience has shown that when fouling occurs and the pumps degrade to the minimum acceptable limit there is still substantial margin between the minimum acceptable flow rate of 0.930r and the design basis flow rate of 14,020. Changing the acceptable range to (0.93 to 1.1 OOr), the alert range to (0.90 to <0.930r), and the required action range to (<0.900r and > 1.1 OOr) for the monthly test would eliminate the need for at least one cleaning per pump during the high growth period, while maintaining adequate margin between pump performance and the design basis flow rate.

Given that 1) the mechanism of degradation is understood and can be trended, 2) the pumps are tested monthly as opposed to the Code required frequency of every three months, and 3) adequate performance margin exists, Surry Power Station believes that changing the acceptance criteria as described above will provide a sufficient level of safety while reducing the burden of maintaining the emergency service water pumps.

Basis for Relief from Paragraph 6.1 The pumps are tested every month instead of once every three months as required by the Code. The monthly test is performed more frequently than that required by paragraph 6.1 if deviations fall within the alert range and the frequency of testing as specified in paragraph 5.1 (i.e., nominally every three months) is doubled.

For vibration measurements that fall within the alert range, maintaining the monthly test frequency is adequate for providing a sufficient level of safety. The monthly testing coupled with the trending and corrective actions described above if flow deviations fall within the alert range, are adequate for providing a sufficient level of safety without doubling the monthly test frequency.

3-20 Revision 1 S1PVl3R1 March 25, 1999

RELIEF REQUEST P-11 (Cont.)

... ....... ' '~

Alternate Testing Proposed Tests will be conducted every month within the tide level limits of the pump reference curve, and flow will be compared to acceptance criteria based on the re'ference curve and the ranges given below. For flow rates that fall into the alert range, the test data will be trended and corrective action taken if the trend evaluation determines that the flow will fall below the required action range before the next monthly test. If either flow or vibration measurements fall into the alert range, the monthly test frequency will not be doubled.

Required Required Acceptable Alert Range Alert Range Action Range Action Range RanQe Low HiQh Low High 0.93 to 1.1 OOr 0.90 to ... <0.900r >1.100r

<0.930r 3-20a Revision 1 S1 PVl3R1 March 25, 1999