ML17164A966
| ML17164A966 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 02/23/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17164A965 | List: |
| References | |
| GL-89-04, GL-89-4, NUDOCS 9903010222 | |
| Download: ML17164A966 (7) | |
Text
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SAFETY EVALUATIONBYTHE OFFICE OF NUCLEAR REACTOR REGULATION RELATEDTO AN INSERVICE TESTING RE VEST FOR RELIEF PP&L INC.
SUS UEHANNASTEAM ELECTRIC STATION UNITS 1 AND 2 DOCKET NOS. 50-387 AND 50-388
1.0 INTRODUCTION
Title 10 of the Code of Federal Re ulations (10 CFR) Section 50.55a, re'quires 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 (ASME Code) and applicable addenda, except where relief has been requested and granted, or proposed alternatives have been authorized by the Commission, pursuant to 10 CFR 50.55a (a)(3)(i), (a)(3)(ii), or (f)(6)(i). In order to obtain authorization or relief, the licensee must demonstrate that: (1) the proposed alternative provides an acceptable level of quality and safety; (2) compliance would result in a hardship or unusual difficulty without a compensating increase in the level of quality and safety; or (3) conformance is impractical for its facility. NRC guidance contained in Generic Letter (GL) 89-04, "Guidance on Developing Acceptable Inservice Testing Programs," provides alternatives to the Code requirements determined acceptable to the staff. Further guidance was given in GL 89-04 Supplement 1, and NUREG-1482, "Guidelines for Inservice Testing at Nuclear Power Plants."
On July 17, 1997, the staff issued a Safety Evaluation (SE) which, in part, requested that PP&L, Inc. (the licensee) revise and resubmit two relief requests for the Susquehanna Steam Electric Station, Units 1 and 2, IST program. These were Relief Requests Nos. 15 and 24, which requested relief from certain ASME Code IST requirements for testing of the Emergency Condenser Water Circulating Water Pumps, and Core Spray Keepfill Check Valves, respectively.
By letter dated November 14, 1997, the licensee submitted the revised relief requests.
A request for additional information, dated July 8, 1998, was subsequently provided to the licensee.
After a conference call on October 26, 1998, the licensee reevaluated the need for Relief Request No. 15 and determined that it is not required. This relief request was retracted as relayed in a letter dated November 17, 1998.
Section 50.55a authorizes the Commission to grant relief from ASME Code requirements or to approve proposed alternatives upon making the necessary findings. The NRC staff's findings with respect to granting or not granting the relief requested or authorizing the proposed alternative as part of the licensee's IST program, for Relief Request No. 24, are contained in this SE.
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PDR Enclosure The licensee is currently in the second 10-year interval program for inservice testing of pumps and valves. This interval began on June 1, 1994, and is scheduled to end on May 31, 2004.
The IST program is based on the requirements of the 1989 Edition,Section XI of the ASME Code, which, by reference, incorporates Operations and Maintenance (OM) Standard, Part 10 (OM-10) "Inservice Testing of Valves in Light-Water Reactor Power Plants."
2.0 BACKGROUND
2.1 Relief Re uest Number 24 The licensee requests relief from the requirements of OM-10, Paragraph 4.3.2.1, which states that check valves shall be exercised nominally every three months, for Units 1 and 2's four Core Spray Keepfill check valves.
The licensee proposes to employ a sample disassembly and inspection program during refueling outages.
2.1.1 The Licensee's Basis for Requesting Relief The licensee states:
Pursuant to 10 CFR 50.55a(f)(i) [sic], relief is requested from the requirements of ASME Code Section XI, OM-1987 Part 10, Paragraph 4.3.2.1. These 2" check valves, located in Keepfill lines for the Core Spray System provide Condensate Transfer System water flow into their respective headers while preventing flow of process water-in the reverse direction during Core Spray System operation.
In the Core Spray (S]ystem, a single test connection exists upstream of the two check valves, which are located very close together.
This configuration would support only. dual testing of each pair of Core Spray System check valves in combination.
Compliance with the Code requirements is impractical because of design limitations, since there is no practical means to verify the operational readiness of each component as intended by the Code.
Additionally, the safety analysis for the plant was reviewed and it was not confirmed that a single check valve was credited for meeting the analysis.
NRC Generic Letter 89-04 Position 2 establishes that disassembly and inspection of check valves may be used as a positive means of determining that a valve's disk will "full-stroke"open or of verifying closure capability, as permitted by ASME Code.
Due to the scope of these inspections, the personnel hazards involved, and system operating restrictions, NRC Generic Letter 89-04 Position 2 established that valve disassembly and inspection may be performed during reactor refueling outages.
The Generic Letter also establishes that sample inspection plan for groups of up to four identical valves in similar applications may be employed within the NRC guidelines specified within Position 2. For these Core Spray keepfill check valves a group of four identical valves willbe used for sampling.
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2.1.2 Alternate Testing The licensee proposes: (as stated)
Full stroke operability willbe verified by inspection during valve disassembly.
The licensee willdisassemble, inspect, verify structural soundness of internal components, and manually exercise the disk through its full stroke for at least one different valve in the group at every refuel cycle until the entire group has been inspected.
The frequency of disassembly for each valve will be at least once every 72 months.
3.0 EVALUATION The licensee requests relief for Unit 1 valves 152F029A, 152F030A, 152F0298, and 152F0308, and Unit 2'valves 252F029A, 252F030A, 252F0298, and 252F0308.
These are 2-inch check valves located in the Keepfill lines of the Core Spray System of each unit. Each unit has two Keepfill lines, each containing two check valves in series, that provide condensate transfer system water flow into their respective headers while preventing flow of process water in the reverse direction during core spray system operation.
OM-10, Paragraph 4.3.2.1 requires that these valves be exercised every three months.
Instead, the licensee proposes to disassemble and inspect one of the four valves during every unit's refueling outage.
The valve to be examined willalternate every refueling outage.
The licensee's request for relief pursuant to 10 CFR 50.55a(f)(6)(i) is based on the impracticality of testing both valves individually, due to limitations in the design, as required by the Code.
- However, as stated in the NRC staff's July17, 1997, SE, testing the valves as a pair during refueling outages is practical, but the testing would not verify that both valves are capable of closing. The staff noted in the SE that the licensee would need to establish a periodic disassembly and inspection program to supplement the periodic testing. As a result, the licensee has opted to establish a sample valve disassembly and inspection program as discussed in Position 2 of GL 89-04. This GL position established that:
(1) valve disassembly and inspection during reactor refueling outages can be used as a positive means of determining that a valve's disk willfull-stroke open or of verifying closure capability, and (2) a sample disassembly and inspection plan for groups of identical valves in similar applications may be employed in instances where the licensee has determined that it is burdensome to disassemble and inspect all applicable valves each refueling outage.
The sample disassembly and inspection plan involves grouping similar valves and testing one valve in each group during each refueling outage.
Guidelines for this plan are stated in Appendix A of NUREG-1482. The sampling technique requires that each valve in the group be the same design and have the same service conditions including valve orientation.
Additionally, at each disassembly the licensee must verify that the disassembled valve is capable of full-stroking and that the internals of the valve are structurally sound, Also, ifthe disassembly is to verify the full-stroke capability of the valve, the disk should be manually exercised.
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L A different valve of each group is required to be disassembled, inspected, and manually full-stroke exercised at each successive refueling outage, until the entire group has been tested.
Ifthe disassembled valve is not capable of being full-stroke exercised or there is binding or failure of valve internal, the remaining valves in that group must also be disassembled, inspected, and manually full-stroke exercised during the same outage.
Once this is complete, the sequence of disassembly must be repeated.
The licensee's submittal did not specifically discuss the corrective actions that would be taken ifthe disassembled valve should fail its inspection or full-stroke exercise.
Ifcorrective actions are not consistent with Appendix A of NUREG-1482, the licensee must seek relief from the requirements of OM-10, Paragraph 4.3.2.6.
Personnel hazards, such as excessive radiation exposure, exist during valve disassembly and inspection.
The staff finds that required inspections for each valve in the sample group during every refueling outage would result in hardship or unusual difficultywithout a compensating increase in the level of quality and safety.
For this reason, relief is authorized under 10 CFR 50.55a(a)(3)(ii). The licensee's proposed alternative is consistent with the guidelines provided in Appendix A of NUREG-1482 and will provide assurance of valve operability.
I Finally, the licensee states that each valve willbe tested once every 72 months.
The staff previously reviewed the impact of changing the test frequency from 72 months (6 years) to 96 months (8 years).
In a letter dated July 27, 1998, the licensee submitted Revision 16 for Unit 1 and Revision 13 for Unit 2 to its IST program in which previously submitted relief requests were revised to extend the testing interval from 6 years to 8 years based on a change of the refueling cycle from 18 months to 24 months. With a 24-month fuel cycle, each valve would be tested once every 8 years.
The staff's SE dated October 5, 1998, determined that it is acceptable for the above-mentioned check valves in the licensee's sample disassembly and inspection program to be tested on an 8-year interval. That conclusion was based both on the staff's acknowledgment in Position 2 of GL 89-04 that, when the refueling cycles are increased to 24 months, each valve in a four-valve sample group would be tested only once every 8 years; and, the check valve failure rate data for the valve groupings.
Hence, the staff finds the proposed inspection interval acceptable.
4.0 CONCLUSION
The proposed alternative to the requirements of OM-10, Paragraph 4.3.2.1 will provide reasonable assurance of operational readiness and, therefore, is authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
Compliance with the specified requirements of this section would result in hardship or unusual difficultywithout a compensating increase in the level of quality and safety.
Principal Contributors:
D. Collins M. Kotzalas Date:
February 2g, 1999
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