ML18153C912
| ML18153C912 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 02/26/1992 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 91-148A, NUDOCS 9203040009 | |
| Download: ML18153C912 (11) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 February 26, 1992 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 Serial No.:
91-148A NS/ETS Docket Nos.: 50-280 50-281 License Nos. :DPR-32 DPR-37 INSERVICE TESTING PROGRAM INTERIM RELIEF REQUESTS FOR THE CONTROL ROOM ENVELOPE AIR CONDITIONING SYSTEM In our letter dated March 22, 1991, (Serial No.91-148) we identified components of the Control Room and Emergency Switchgear Room Air Conditioning System that have been incorporated into the Section XI lnservice Testing Program.
Relief Requests P-16, P-17, and V-46 which are associated with these components were included in the letter. During a telephone conversation on November 5, 1991, your staff requested additional information for the relief requests. The relief requests were revised to include the additional information and are attached.
The instrumentation required to perform the ASME Section XI testing is being procured and installed over the next two years during plant operation and refueling outages. As the instrumentation is installed and the appropriate procedures revised, the Section XI testing will be performed. The two flow elements for the chiller service water pumps, 1-VS-P-1 A, B and C, cannot be installed with the plant at power.
Therefore, one flow element is scheduled for installation in the 1993 Unit 2 refueling outage and the second flow element is scheduled for installation during the Unit 1 1994 refueling outage.
Since the original relief requests were submitted, changes in the Company's overall refueling schedule for the nuclear units have occurred. Due to these changes the Surry Unit 1 Cycle 12 refueling outage has been postponed from the third quarter of 1993 to the second quarter of 1994. Therefore, the schedule identified in our original submittal for completing the installation of the ASME Section XI instrumentation in the Main Control and Emergency Switchgear Room Air Conditioning System is changing from the third quarter of 1993 to the second quarter of 1994.
This schedule is
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predicated on the installation of two additional Main Control Room and Emergency Switchgear Air Conditioning System chillers by the end of 1992.
If you have any further questions, please contact us.
Very truly yours, JL~
W. L. Slewart ~
- Senior Vice President - Nuclear Attachment cc:
U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N.W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station
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e ATTACHMENT SURRY POWER STATION ADDITIONS TO THE INSERVICE TESTING PROGRAM CONTROL ROOM ENVELOPE AIR CONDITIONING SYSTEM
System : Main Control Room Air Conditioning Pump(s): 1-VS-P-1 A 1-VS-P-1 B 1-VS-P-1 C Class:
3 Section XI Code Requirements For Which Interim Relief Is Reguested Measure flow, inlet pressure and differential pressure.
Basis For Interim Reguest No flow or inlet pressure instrumentation is installed.
According to Technical Specification paragraph 3.23.C.1.b, "If one chiller becomes inoperable, return the inoperable train to an operable status within seven (7) days or bring both units to Hot Shutdown within the next six (6) hours and Cold Shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />."
Because the Main Control Room and Emergency Switchgear Room Air Conditioning System is common for both units, the above action statement applies whenever Unit 1 or Unit 2 is operating.
Given the scope of the required instrumentation modifications and the existing system configuration, it is estimated that installation of the appropriate flow and pressure instrumentation cannot be completed within the Technical Specification 7 day action statement. Two additional Main Control Room and Emergency Switchgear Room Air Conditioning System chillers are scheduled for installation by the end of 1992. The additional chillers will eliminate the need for entry into the Technical Specification action statement to install the instrumentation. Also, the flow elements for the chiller service water pumps cannot be installed at power.
Therefore, installation of the additional instrumentation is scheduled to be completed by the end of Unit 1 Cycle 12 refueling outage currently scheduled for second quarter of 1994.
Interim Alternate Testing Proposed The control room chillers are monitored at least once every quarter for adequate performance.
Part of this surveillance verifies that minimum service water flow requirements are being met by the pumps. A flow rate of 240 gpm is the minimum required service water flow for condenser operability. The minimum flow is verified by measuring the differential pressure across the chiller condensers.
The normal operating range is 4 to 7 psid across the chiller condensers. An alert value has been established at 10% above the minimum flow or 264 gpm. This flow equates to a differential pressure of 4 psid. If a differential pressure of at least 3.5 psid (240 gpm) cannot be achieved after any adjustments (i.e., adjusting the backwash valve and cleaning the service water pump Y-strainer) then the pump is declared inoperable.
INTERIM RELIEF REQUEST P-16 (Cont.)
When differential pressure exceeds 7 psid, the condenser tubes require cleaning.
Also, if a pump discharge pressure of 30 psig cannot be achieved with a fully shut backwash isolation valve, then an investigation is initiated to check for possible upstream restriction or a degraded pump. Vibration monitoring has been added to the surveillance and will be performed at least once every quarter. The acceptance criteria for vibration are based upon the Section XI program.
The correlation between condenser differential pressure and flow was established during special tests that were conducted in June of 1989. The special tests consisted of fabricating a temporary instrumented loop of pipe with a straight run long enough to produce stable flow. The permanent piping has no straight runs that are long enough to measure flow. A section of permanent pipe was removed and the temporary section installed. The results of the tests are given in Figure 1 and Table 1.
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INTERIM RELIEF REQUEST P-16 (Cont.)
TABLE 1" FLOW VERSUS CONDENSER D~FFERENTIAL PRESSURE SPECIAL TEST ST-235 RUN 6/15 THRU 17/89 MCR CHILLERS l-VS-E-4A, 4B, AND 4C FLOW RATES CONDENSER DP IN PSI FPS GPM E-4A E-4B E-4C o.o o.o 0.1 o.o o.o 1.0 23.0 0.2 0.1 0.1 2.0 46.0 0.3 0.2 0.2 3.0 69.2 0.4 0.4 0.5 4.0 92.1 0.7 0.6 0.9 5.0 115.1 LO 1.0 1.0 6.0 138.2 1.3 1.3 1.3 7.0 161.2 1.7 1.6 1.7 8.0 184.2 2.2 2.2 2.2 9.0 207.2 2.6 2.8 2.6 10.0 230.3 3.0 3.1 3.1 11.0 253.3 3.8 3.8 3.7 12.0 276.3 4.2 4.3 4.1 13.0 299.3 5.0 5.0 4.9 14.0 322.4 5.7 5.7 15.0 345.4 6.3 6.4
e RELIEF REQUEST P-17 System : Main Control Roo.m Air Conditioning Pump(s): 1-VS-P-2A 1-VS-P-2B 1-VS-P-2C Class:
3 Section XI Code Requirements For Which Relief Is Requested ASME Section XI, Subarticle IWP-311 O requires reference values to be one or more fixed set of measured values. All subsequent test results shall be compared to these reference values.
Basis For Request The chilled water circulating pumps for the main control room air conditioning system service two trains each with four air handling units connected in a parallel configuration. Total flow for each pump is determined by summing the recorded flows from flow instruments placed downstream of the four air handling units in one of the trains. Test flow is controlled by throttling a gate valve near each air handling unit, which has proven to be a crude flow control method. Having to throttle to a specific reference flow using the sum of flows from four instruments with a gate valve that is not suited for fine flow control is not very practical.
Alternate Testing Proposed Two reference points of total flow versus differential pressure will be established from the reference test for each pump.
A straight line approximation will be used to determine differential pressure reference points as a function of flow between the two test points. By keeping the difference between two test points small (a difference of 30 gpm compared to a nominal reference value of 270 gpm), the straight line is a good approximation of the pump curve within the two test points.
During the subsequent tests, flow will be throttled in each parallel path as close as practical to a reference flow value for that path. The total flow must fall between the two reference points used to establish the straight line approximation. The total flow and the corresponding differential pressure will be compared to either graphical and/or tabular acceptance criteria based on the straight line approximation of the reference pump curve.
RELIEF REQUEST P-17 (Cont.)
For example, given the straight line equation determined from the two reference points for flow and differential pressure:
P rdiff = a + b*O where P rdiff = the reference differential pressure based on the test value for flow (Q) recorded during subsequent tests and, a and bare constants, the acceptance criteria for the flow (Q) would be as follows:
Upper Required Action = 1.03*P rdiff Upper Alert
= 1.02*P rdiff Lower Alert
= 0.93*P rdiff Lower Required Action = 0.90*P rdiff The multipliers on P rdiff are taken from Table IWP-3100-2 in Section XI. The actual recorded differential pressure (P adiff) will then be compared to the acceptance criteria determined from P rdiff* Also, the tests results can be trended from test to test by normalizing P adiff to P rdiff" For acceptable operation, the ratio of P adiflP rdiff must fall between 0.93 and 1.02.
A decrease in the ratio from test to test indicates a degradation in pump performance.
System : Service Water Valve(s):
1-SW-313 1-SW-323 2-SW-333 Category: C Class:
3 INTERIM RELIEF REQUEST V-46 Function: Service Water Supply to Main Control Room Air Conditioning System ChillersSection XI Code Requirement For Which Interim Relief Is Requested Exercise valves for operability to the open position every three months.
Basis For Interim Relief These check valves cannot be full flow tested because instrumentation is not installed to directly measure flow or differential pressure across the valve.
No flow or inlet pressure instrumentation is installed.
According to Technical Specification paragraph 3.23.C.1.b, "If one chiller becomes inoperable, return the inoperable train to an operable status within seven (7) days or bring both units to Hot Shutdown within the next six (6) hours and Cold Shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />."
Because the Main Control Room and Emergency Switchgear Room Air Conditioning system is common for both units, the above action statement applies whenever Unit 1 or Unit 2 is operating.
Given the scope of the required instrumentation modifications and the existing system configuration, it is estimated that installation of the appropriate flow instrumentation cannot be completed within the Technical Specification 7 day action statement. Two additional Main Control Room and Emergency Switchgear Room Air Conditioning System chillers are scheduled for installation by the end of 1992. The additional chillers will eliminate the need for entry into the Technical Specification action statement to install the instrumentation. Also, the flow elements for the chiller service water pumps cannot be installed at power. Therefore, installation of the additional instrumentation is scheduled to be completed by the end of Unit 1 Cycle 12 refueling outage currently scheduled for second quarter of 1994.
RELIEF REQUEST V-46 (Cont.)
Interim Alternate Testing Proposed These valves will be grouped together and one valve from this group will be disassembled and inspected every reactor refueling.
A different valve will be disassembled every reactor refueling. They will be partial-stroked open once every three months with flow.
When flow instrumentation is installed by the second quarter of 1994, flow will be measured directly and the valves will be full flow tested once every three months.