ML15112A768
| ML15112A768 | |
| Person / Time | |
|---|---|
| Site: | Oconee, Peach Bottom  |
| Issue date: | 09/20/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML15112A767 | List: |
| References | |
| NUDOCS 9909230007 | |
| Download: ML15112A768 (7) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE TESTING PROGRAM, THIRD 10-YEAR INTERVAL DUKE ENERGY CORPORATION OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 DOCKET NUMBERS 50-269, 50-270, AND 50-287
1.0 INTRODUCTION
The Code of Federal Regulations, 10 CFR 50.55a, requires that inservice testing (IST) of certain American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 pumps and valves be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code (the Code) and applicable addenda, except where alternatives have been authorized or relief has been requested by the licensee and granted by the Commission pursuant to paragraphs (a)(3)(i), (a)(3)(ii), or (f)(6)(i) of 10 CFR 50.55a. In proposing alternatives or requesting relief, the licensee must demonstrate that: (1) the proposed alternatives 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 is impractical for its facility. Section 50.55a authorizes the Commission to approve alternatives and to grant relief from ASME code requirements upon making the necessary findings. NRC guidance contained in Generic Letter (GL) 89-04, "Guidance on Developing Acceptable Inservice Testing Programs," provides alternatives to the Code requirements which are acceptable. Further guidance is-given in GL 89-04, Supplement 1, and NUREG-1482, "Guidelines for Inservice Testing at Nuclear Power Plants."
In a letter dated May 26, 1999, Duke Energy Corporation, licensee for the Oconee Nuclear Station, Units 1, 2, and 3, submitted Revision 25 of the Pump and Valve Inservice Testing Program for the station. The revision contained four new relief requests. A conference call was held on August 24, 1999, to discuss relief request ON-SRP-LPI-06. As a result, the licensee submitted revised relief request ON-SRP-LPI-06 in a letter dated August 26, 1999.
Oconee Nuclear Station, Units 1, 2, and 3, are currently implementing their third 10-year IST interval. This interval began on July 1, 1992, and is scheduled to end on June 30, 2002. The IST program for pumps was developed in accordance with the 1986 Edition of ASME Code,Section XI, Subsection IWP; for valves, in accordance with ASME OM-1 987 Standard OM-1 988 Part 10; and for safety and relief valves, in accordance with the 1987 Edition of ASME OM-1.
The NRC's findings with respect to authorizing alternatives and granting or denying the IST program relief requests are given below.
9909230007 990920 PDR ADOCK 05000269 PDR
-2 2:0 VALVE RELIEF REQUESTS 2.1 Relief Request ON-GRV-12 The licensee requests relief from the minimum elapsed time requirements of OM-1, Paragraphs 8.1.2.8, and 8.1.3.7 for all safety and relief valves that are tested at ambient conditions using a test medium at ambient conditions.
2.1.1 Licensee's Basis for Requesting Relief The licensee states:
This is a generic request for relief for safety and relief valves in compressible fluid service (other than steam) and liquid service applications, tested under ambient conditions using a test medium at ambient conditions. For these valves, the requirement for verifying temperature stability (by waiting 10 minutes between successive openings) is inappropriate and of no value. There is negligible affect on valve setpoint due to minor temperature deviations that might occur at these ambient conditions.
The net result of having to wait 10 minutes between successive openings is an increase in manpower and time to perform the tests and an increase in radiation exposure when located in radiation areas, without a commensurate increase in test accuracy.
[Note: This issue has been identified by the ASME Code Committees along with safety and relief valve industry experts and is reflected in a change made to the 1995 version of the code (Appendix 1). In addition, NUREG-1482, 4.3.9 (6) states "Thermal equilibrium need not be verified for liquid service valves tested at ambient temperature using a test medium (at ambient) temperature."]
2.1.2 Alternative Testing The licensee proposes:
For safety and relief valves tested under ambient conditions using test medium at ambient conditions,,the 10 minute hold requirement between successive openings will be deleted.
2.1.3 Evaluation The safety and relief valves function to provide over-pressure protection to their associated systems. The Code (Paragraphs 8.1.2.8, and 8.1.3.7 of OM-1) requires that a minimum of 10 minutes elapse between successive valve openings. The licensee proposes to delete the 10 minute hold time requirement for valves tested under ambient conditions using a test medium at ambient conditions.
The purpose of the hold time requirement between successive openings is to allow time for the valve to return to thermal equilibrium. This is not necessary for valves that are tested under
-3 ambient conditions using a test medium at ambient conditions since only minor temperature deviations occur during testing. Therefore, the staff had determined that deleting the hold time requirement between successive valve openings is acceptable.
Modifications were made to the 1995 Edition of the OM Code, Paragraphs 1-8.1.2(d) and 1-8.1.3(d), which no longer require verification of thermal equilibrium for valves that are tested at ambient temperature using a test medium at ambient temperature. The staff has reviewed these provisions of the 1995 Edition of the Code and found them to be acceptable. Endorsement of the 1995 Edition of the Code is expected in September 1999.
The licensee's alternative test method will provide an acceptable level of quality and safety. The staff finds this method acceptable in that it offers equivalent protection as provided by OM-1, Paragraphs 8.1.2.8, and 8.1.3.7.
2.1.4 Conclusion The proposed alternative to the minimum elapsed time requirements of OM-1, Paragraphs 8.1.2.8, and 8.1.3.7 for all safety and relief valves that are tested at ambient conditions using a test medium at ambient conditions is authorized pursuant to 10 CFR 50.55a(a)(3)(i). The licensee's alternative test method will provide an acceptable level of quality and safety.
2.2 Relief Request ON-GRV-13 The licensee requests relief from the minimum elapsed time requirements of OM-1, Paragraphs 8.1.1.8, 8.1.2.8, and 8.1.3.7 for all safety and relief valves which are tested at other than ambient conditions.
2.2.1 Licensee's Basis for Requesting Relief The licensee states:
This is a generic request for relief for all safety and relief valves. The 1995 version of the code, Appendix I has adopted a 5 minute hold time for steam, compressible fluid, and water service applications rather than the 10 minute hold time. This change was based on actual test data that revealed an insignificant effect on valve setpoint by reducing the hold time between successive openings to 5 minutes.
2.2.2 Altemative Testing The licensee proposes:
For safety and relief valves tested at other than ambient conditions, a 5 minute hold time will be used between successive valve openings.
2.2.3 Evaluation
-4 The safety and relief valves function to provide over-pressure protection to their associated systems. The Code (Paragraphs 8.1.1.8, 8.1.2.8, and 8.1.3.7 of OM-1) requires that a minimum of 10 minutes elapse between successive valve openings. The licensee proposes an alternative test method in which 5 minutes elapse between successive valve openings.
Test data has shown that reducing the hold time requirements has had an insignificant effect on the setpoint of valves. Therefore, the staff has determined that the licensee's proposed alternative test method will provide an acceptable level of quality and safety.
Modifications were made to the hold time requirements in the 1998 Edition of the OM Code, Appendix I, Paragraphs 1-8110(h), I-8120(h) and I-8130(g). The minimum elapsed time between successive valve openings was shortened from 10 to 5 minutes. The licensee's alternative is consistent with this provision of the 1998 Edition of the OM Code. However, authorization of the licensee's proposed alternative does not imply staff endorsement of the 1998 Edition of the Code.
The licensee's alternative test method will provide an acceptable level of quality and safety. The staff finds this method acceptable in that it offers equivalent protection as provided by OV-M1, Paragraphs 8.1.1.8, 8.1.2.8, and 8.1.3.7.
2.2.4 Conclusion The proposed alternative to the minimum elapsed time requirements of OM-1, Paragraphs 8.1.1.8, 8.1.2.8, and 8.1.3.7 for all safety and relief valves that are tested at other than ambient conditions is authorized pursuant to 10 CFR 50.55a(a)(3)(i). The licensee's alternative test method is consistent with the 1998 Code requirements and will provide an acceptable level of quality and safety.
2.3 Relief Request ON-GRV-14 The licensee requests relief from the temperature stability requirements of OM-1, Paragraphs 8.1.2.4 and 8.1.3.4 for all safety and relief valves that are tested under ambient conditions using a test medium at ambient conditions.
2.3.1 Licensee's Basis for Requesting Relief The licensee states:
This, is a generic request for relief for all safety and relief valves tested under ambient conditions using a test medium at ambient conditions. For these valves, the requirement for verifying temperature stability (by ensuring no change in measured temperature of more than 10 OF in 30 minutes) is inappropriate and needlessly adds time to the test activity. Since the valves will be tested at ambient conditions, no temperature differential exists and the valves would already be considered stable per the test requirement above. There is negligible affect on valve setpoint associated with any minor temperature deviations at these ambient conditions.
-5
[Note: This issue has been identified by the ASME Code Committees along with safety and relief valve industry experts and is reflected in a change made to the 1995 version of the code, Appendix I ("Verification of thermal equilibrium is not required for valves which are tested at ambient temperature using a test medium at ambient temperature").]
2.3.2 Alternative Testing The licensee proposes:
For safety and relief valves tested at ambient conditions using test medium at ambient conditions, the Temperature Stability requirements of OM-1, 1987 Sections 8.1.2.4 and 8.1.3.4 will be replaced by the Thermal Equilibrium requirements in the 1995 edition of the code.
2.3.3 Evaluation The safety and relief valves function to provide over-pressure protection to their associated systems. The Code (Paragraphs 8.1.2.4 and 8.1.3.4 of OM-1) requires that temperature stability be achieved prior to starting set pressure testing. It states that the test method shall be such that the temperature of the valve body shall be known and stabilized before commencing set pressure testing, with no change in measured temperature of more than 10 'F in 30 minutes.
The licensee proposes to replace the temperature stability requirements with the thermal equilibrium requirements of the 1995 Edition of the OM Code.
Changes made in the 1995 Edition of the Code, Paragraphs I 8.1.2(d) and I 8.1.3(d) no longer require verification of thermal equilibrium for valves that are tested at ambient temperatures using a test medium at ambient temperatures. Under these conditions, there is no significant difference in temperature between the valves and the surroundings and, therefore, the temperature of the valve body is stable. For this reason, the staff has determined that the licensee's proposed alternative is acceptable.
The staff has reviewed this provision of the 1995 Edition of the OM Code and found it to be acceptable. Endorsement of the 1995 Code is expected in September 1999.
The licensee's alternative will provide an acceptable level of quality and safety. The staff finds this method acceptable in that it offers equivalent protection as provided by OM-1, Paragraphs 8.1.2.4, and 8.1.3.4.
2.3.4 Conclusion The proposed alternative to the temperature stability requirements of OM-1, Paragraphs 8.1.2.4 and 8.1.3.4 for all safety and relief valves that are tested under ambient conditions using a test medium at ambient conditions is authorized pursuant to 10 CFR 50.55a(a)(3)(i). The licensee's alternative is consistent with the 1995 Code requirements and will provide an acceptable level of quality and safety.
3.0 PUMP RELIEF REQUEST
-6 3.1 Relief Request ON-SRP-LPI-06 The licensee requests relief from the requirements of IWP-31 00 for the "A" low pressure injection pumps. When the system resistance cannot be varied, the Code requires that the flow rate and pressure be determined quarterly and compared with the reference values. The licensee proposes to test the pumps at minimum flow conditions quarterly and at design flow during refueling outages.
3.1.1 Licensee's Basis for Requesting Relief The licensee states:
The 1A, 2A, and 3A Low Pressure Injection (LPI) pumps are tested during power operation through a recirculation flow path to the Borated Water Storage Tank (BWST).
The "A" pump for each unit can only be tested using a line-up that contains a section of 3-inch pipe. Other flow alignments are physically possible, but are prohibited by our Technical Specifications due to the necessity of having both trains of the system
- inoperable simultaneously. From past test data, the recirculation line of the A train pumps is only capable of passing approximately 1200 gallons per minute (gpm). Due to a smaller recirculation line on the A train, it is not desirable to throttle these pumps below this point. During the performance testing, the system resistance is not varied and all valves in the flow path are full open; however, the flow is specified as the fixed parameter and the differential pressure is examined for degradation. Examining past performance data, the flow rate during the pump performance testing varies +/-6% from the fixed reference flow. From examination of the manufacturer's pump curve for the 1A, 2A, and 3A LPI pumps, the developed head is constant between 500 and 1300 gpm. Thus, the acceptable range for the differential pressure is unaffected by variations in the pump flow rate between 500 and 1300 gpm. Therefore, a tolerance of +/-6% of the reference flow is acceptable as long as the allowable flow range remains between 500 and 1300 gpm.
3.1.2 Alternative Testing The licensee proposes:
During quarterly testing at power operation, the 1A, 2A, and 3A Low Pressure Injection Pumps will be tested at less than required accident flows. A tolerance of +/-6% of the reference flow will be allowed as described above. During refueling outages, the 1A, 2A, and 3A Low pressure Injection Pumps will be tested per the requirements of the ONS Inservice Test Program at the accident design flow rate.
3.1.3 Evaluation The low pressure injection pumps provide emergency core cooling flow from the borated water storage tank directly to the reactor vessel in the event of a large break loss of coolant accident.
They also provide long term post-accident containment sump recirculation cooling. The Code requires that an inservice test be performed every 3 months and the flow rate and pressure be measured and compared with reference values. The licensee proposes to test the pumps
-7 quarterly at minimum flow conditions during plant operations and at full flow conditions during refueling outages. During the quarterly testing, a tolerance of +/-6 percent of the reference value is proposed.
Measuring the pumps' flow rate while operating on the minimum flow recirculation line is not as meaningful a test for pump operability as a full flow test because the low flow rate may cause excess turbulence and cavitation within the pump. In addition, it may not provide accurate and repeatable information for evaluation of pump degradation. Testing these pumps using injection during power operation is impractical because the pumps are not designed to develop sufficient head to inject into the reactor pressure vessel.
During the quarterly testing through the minimum flow lines, the flow rate varies +/-6 percent from the fixed reference flow rate. The Code does not allow for variance from a fixed reference value. However, Position 9 of GL 89-04 addresses the issue of pump testing using minimum flow return lines. Minimum flow lines are not designed for pump testing and rarely have flow measuring devices that meet code requirements. In cases where flow can only be established through a minimum flow path during quarterly pump testing, and a path exists at cold shutdown or refueling outages to perform a test of the pump under full or substantial flow conditions, the staff has determined that the increased interval is an acceptable alternative to the Code requirements provided that pump differential pressure, flow rate, and bearing vibration measurements are taken during this testing, and that quarterly tests (that also measure at least pump differential pressure and vibration) are continued. -The licensee's proposed alternative is consistent with Position 9 of GL 89-04 and will provide reasonable assurance of the pumps' operability.
3.1.4 Conclusion Relief from the requirements of IWP-31 00, for the 1A, 2A, and 3A LPI pumps, is granted pursuant to 10 CFR 50.55a(f)(6)(i). This alternative testing provides reasonable assurance of operational readiness. Based on the impracticality of complying with the Code and the burden on the licensee if those requirements were imposed, relief is granted.
4.0 CONCLUSION
Relief is granted for ON-SRP-LPI-06 pursuant to 10 CFR 50.55a(f)(6)(i). In making this determination, the staff has considered the impracticality of performing the required testing and the burden on the licensee if the requirements were imposed.
The alternatives to the Code requirements as proposed in ON-GRV-12, ON-GRV-13, and ON-GRV-14 will provide an acceptable level of quality and safety and are authorized pursuant to 10 CFR 50.55a(a)(3)(i).
Principal Contributor: M. Kotzalas Date:
September 20, 1999