ML18153D055
| ML18153D055 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 06/26/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18153D053 | List: |
| References | |
| NUDOCS 9207090296 | |
| Download: ML18153D055 (7) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE TESTING PROGRAM AND REQUEST FOR RELIEF VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 DOCKET NOS. 50-280 AND 50-281
1.0 INTRODUCTION
The Code of Federal Regulations, 10 CFR 50.55a(g), requires that inservice testing (IST) of certain ASME Class 1, 2, and 3 pumps and valves be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable addenda, except where specific written relief has been requested by the licensee and granted by the Commission pursuant to Subsections (a)(3)(i),
(a)(3)(ii), or (g)(6)(i) of 10 CFR 50.55a.
In requesting relief, the licensee must demonstrate that: (1) the proposed alternatives would provide an acceptable level of quality and safety; (2) compliance would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety; or (3) conformance with certain requirements of the applicable Code edition and addenda is impractical.for its facility.
These regulations authorize the Commission to grant relief from ASME Code requirements upon making the necessary findings.
The NRC staff's findings with respect to granting or not granting the relief requested as part of the licensee's IST Program are contained in this Safety Evaluation (SE).
This SE covers relief requests P-16, P-17, and V-46 as described in Virginia Electric and Power Company's (the licensee) letter dated March 22, 1991, as supplemented February 26, 1992.
The licensee's program is based on the requirements of Section XI of the ASME Code, 1983 Edition through the Summer of 1983 Addenda.
2.0 INTERIM RELIEF REQUEST P-16 The licensee has requested interim relief from ASME Code Section XI, IWP-3000 pump test requirements to measure flow, inlet pressure and differential pressure. This interim relief request is for main control room air conditioning pumps 1-VS-P-lA, 1-VS-P-lB, and 1-VS-P-lC.
2.1 Basis for Interim Request No flow or inlet pressure instrumentation exists. According to Technical Specification paragraph 3.23.C.l.b, "if one chiller becomes inoperable, return the inoperable train to an operable status within seven (7) days or bring both
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units to Hot Shutdown with 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, installation of the appropriate flow and pressure instrumentation cannot be completed within the Technical Specification seven (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.
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.
2.2 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 condenser.
The normal operating range is 4 to 7 psid across the chiller condenser.
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.
When differential pre~sure exceeds 7 psid, the ~ondenser 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 IWP requirements.
2.3 Evaluation NRC Inspection Reports 50-280/90-41 and 50-281/90-41 identified components in the control room air conditioning system that were not properly classified and tested in accordance with the requirements of Section XI of the ASME Boiler and Pressure Vessel Code.
The pumps for which relief was requested were identified in the inspection report and have now been incorporated into the licensee's Inservice Testing Program.
Since the pumps do not have the instrumentation needed for the required flow and pressure measurements, interim relief is requested.
The licensee proposes to use the interim period for system modifications and instrumentation installation. A 2 year interim period is requested.
It is proposed to complete the instrumentation
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3 installation by the end of the next Unit 1 (Cycle 12) refueling outage scheduled for the second quarter of 1994.
The instrumentation installation cannot be expedited without imposing an unrealistic burden on the licensee, since (1) the instrumentation cannot be installed with the plant at power, (2) the instrumentation installation cannot be completed within a Technical Specification 7-day action limit, and (3) the air conditioning system is common to Units 1 and 2.
The licensee first plans to modify the system by adding two chillers to eliminate the need for entry into the Technical Specification action statement to install the instrumentation.
The chiller additions will be completed by the end of 1992.
In the interim the licensee proposes to test pump performance and condition quarterly by monitoring flow output and mechanical excitations. The pump output will be assessed by monitoring its flow passing through the chiller condenser.
The flow requirements have been established and the minimum flow will be verified by measuring the differential pressure across the chiller condenser.
A correlation between condenser differential pressure and pump flow was established based on a series of tests conducted on the main control room air conditioning pumps and chiller condensers. Alert and action limits have been set based on differential pressure measurements and flow conditions.
The mechanical condition of the pumps will also be assessed by monitoring the mechanical vibrational response in accordance with the requirements of the ASME Boiler and Pressure Vessel Code,Section XI, Subsection IWP.
2.4 Summary Based on the above, the staff has determined that (1) the proposed alternative testing provides an acceptable level of quality and safety for the interim period, (2) immediate compliance would result in an unrealistic hardship without a compensating increase in safety, and (3) considering the time required to modify the system and install the needed instruments, an interim relief to the end of Unit 1 (Cycle 12) refueling outage scheduled for the second quarter of 1994 is granted pursuant to 10 CFR 50.55a(a)(3)(i) and (a)(3)(ii).
3.0 RELIEF REQUEST P-17 The licensee requests relief from ASME Code Section XI, Subarticle IWP-3110, requirements to establish reference values for a fixed set of measured values and to compare all subsequent test results to these reference values.
3.1 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 unit, which has proven to be a crude flow control
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method.
Having to throttle to a total specific reference flow using the sum of flows from four instruments with gate valves that are not suited for fine flow control is not very practical.
3.2 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 the 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 the path.
The total flow must fall between the two references 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.
For example, given the straight line equation determined from the two reference points for flow and differential pressure:
P rdiff=a+b*Q where Prdiff=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
=l. 02*P rdiff Lower Alert
=0.93*Prdiff Lower Required Action = 0.90*Prdiff The multipliers on P~iff are*taken from Table IWP-3100-2 in Section XI.
The actual recorded differential pressure (Pad"ff) will then be compared to the acceptance criteria determined from (PadifJ. Also, the tests results can be trended from test to test by norma 1 i zing P *tt to P rdif.
For acceptance operation, the ratio of P adiff/P rdjff must fa14 between O. 93 and I. 02.
A decrease in the ratio from test to test indicates a degradation in pump performance.
3.3 Evaluation The system configuration requires total flow from each pump to be determined by summing the recorded flows from instruments placed downstream of the four air handling units in the system train. Test flow is established by throttling gate valves near each air handling unit.
The throttling of several crude control valves in this manner to achieve a specific total reference flow
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is impractical for consistently obtaining the required flow.
Modification of the system to provide suitable flow control valves would place an undue burden on the licensee.
The licensee proposes an alternate test using two sets of reference points for flow and differential pressure for each pump.
The reference points will closely bound the intended nominal total reference flow value.
A straight line approximation will be used to determine a reference differential pressure value as a function of the test flow achieved between the two sets of reference flow points.
The licensee will keep the difference between the two sets of bounding reference points small to justify the validity of the straight line approximation.
During subsequent tests the flow in the train will be throttled to obtain a total flow that falls between the bounding reference points.
The established test flow and corresponding differential pressure will be measured and recorded. A reference differential pressure will then be calculated using the measured flow and straight line equation.
The required test results analysis using the calculated reference differential pressure and measured flow will be performed based on IWP-3200 requirements.
Requiring a modificatiory of the system configuration to provide a finer and more consistent flow control method is impractical and places an unrealistic burden on the licensee.
3.4 Summary Based on (1) the impracticality of requiring the licensee to modify the design and system configuration to meet Code test requirements resulting in an undue burden, and (2) the proposed alternate testing providing adequate assurance of operational readiness, relief is granted pursuant to 10 CFR 50.55a(g)(6)(i).
4.0 INTERIM RELIEF REQUEST V-46 The licensee has requested interim relief from the requirements of ASME Code Section XI, IWV-3520, Tests for Check Valves, to exercise valves I-SW-313, I-SW-333 and 2-SW-333 to the open position every 3 months during plant operation.
4.1 Basis for Interim Relief These check valves cannot be full flow open 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.l.b, "If one chiller becomes inoperable, return the inoperable train to an operable status within seven (7) days or bring 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.
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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 seven (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.
4.2 Interim Alternate Testing Proposed These valves will be grouped together and one valve disassembled and inspected every reactor refueling.
valve will be disassembled every reactor refueling.
partial-stroke open once every 3 months with flow.
from this group will be In addition, a different The valves will also be When flow instrumentation is installed by the second quarter of 1994, flow will be measured directly and the valve will be full flow tested once every 3 months.
4.3 Evaluation NRC Inspection Report 50-280/90-41 ind 50-281/90-41 identified components in the control room air conditioning system that were not properly classified and tested to regulatory and Code testing requirements.
The relief request valves were identified in the inspection report and have been incorporated into the licensee's Inservice Testing Program.
Since the valves and system do not have the instrumentation needed to confirm the valve disk position, interim relief is requested.
The purpose for the interim period is to allow the licensee time to modify the system and install the needed instrumentation.
The completion of the instrumentation installation is scheduled for the end of the next Unit 1 (Cycle 12) refueling outage, which is the second quarter of 1994.
The instrumentation installation cannot be expedited without imposing an unrealistic burden on the licensee, since (1) instrumentation cannot be installed with the plant at power, (2) the installation cannot be completed within the Technical Specification 7 day action limit, and (3) the air conditioning system is common to Units 1 and 2.
The licensee first plans to add two chillers to the system to avoid the need for entry into the Technical Specification action statement. This installation will be completed by the end of 1992.
In the interim the licensee proposed to part-stroke open the valves every 3 months with flow and implement a group disassembly and inspection sampling program.
A different valve in the group will be dissembled and inspected at each refueling.
The staff considers valve disassembly and inspection to be a maintenance procedure that is not equivalent to testing.
However, this method of verifying the open function requirement is an acceptable option when no other
7 method is available.
This is an acceptable interim option to allow the licensee time to modify the system and install appropriate instrumentation.
4.4 Summary Based on (1) the impracticality of confirming the valve disk open position to Code requirements with the current design and system configuration, (2) the burden on the licensee if Code requirements were immediately imposed, (3) the alternate testing provides adequate assurance of operational readiness for an interim period, and (4) consideration of the time required to modify the system and install appropriate instrumentation, interim relief to the end of the Unit 1 Cycle 12 refueling outage scheduled for the second quarter of 1994 is granted pursuant to 10 CFR 50.55a(g)(6)(i).
5.0 CONCLUSION
The staff has reviewed relief requests P-16, P-17 and V-46 as described in the licensee's letters dated March 22, 1991, as supplemented February 26, 1992.
The staff has determined that granting relief, pursuant to 10 CFR 50.55a(a)(3)(i), (a)(3)(ii), and (g)(6)(i), is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest.
In making this determination, the staff has considered the alternative testing being implemented, compliance resulting in a hardship without a compensating increase in safety, and the impracticality of performing the required testing considering the burden if the requirements were imposed.
Principal Contributor:
F. Grubelich Date: June 26, 1992