NMP2L2777, Relief Request Associated with Excess Flow Check Valves
| ML21251A491 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 09/08/2021 |
| From: | David Gudger Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NMP2L2777 | |
| Download: ML21251A491 (6) | |
Text
200 Exelon Way Kennett Square, PA 19348 www.exeloncorp.com 10 CFR 50.55a NMP2L2777 September 8, 2021 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69 NRC Docket No. 50-410
Subject:
Relief Request Associated with Excess Flow Check Valves In accordance with 10 CFR 50.55a, Codes and standards, paragraph (z)(1), Exelon Generation Company, LLC (Exelon), requests NRC approval of a proposed relief request associated with the Inservice Testing (IST) Program for the Nine Mile Point Nuclear Station, Unit 2. This request revises the testing frequency of Excess Flow Check Valves (EFCVs).
The Nine Mile Point Nuclear Station, Unit 2 (NMP2) complies with the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) 2012 Edition with no Addenda.
We request your approval by February 25, 2022.
There are no regulatory commitments contained in this letter.
If you have any questions, please contact Tom Loomis at 610-765-5510.
Respectfully, David T. Gudger Sr. Manager - Licensing and Regulatory Affairs Exelon Generation Company, LLC
Attachment:
Request for Relief GV-RR-10 cc:
Regional Administrator - NRC Region I NRC Senior Resident Inspector - Nine Mile Point NRC Project Manager - Nine Mile Point A. L. Peterson - NYSERDA
ATTACHMENT Request for Relief GV-RR-10
10 CFR 50.55a Relief Request: GVRR-10 Revision 0 (Page 1 of 4)
Request for Relief GV-RR-10 Excess Flow Check Valves In Accordance with 10 CFR 50.55a(z)(1)
- 1. ASME Code Component(s) Affected:
Component ID Class Category System 2CMS*EFV10 2
C Containment Atmosphere Monitoring 2CMS*EFV1A 2
C Containment Atmosphere Monitoring 2CMS*EFV1B 2
C Containment Atmosphere Monitoring 2CMS*EFV3A 2
C Containment Atmosphere Monitoring 2CMS*EFV3B 2
C Containment Atmosphere Monitoring 2CMS*EFV5A 2
C Containment Atmosphere Monitoring 2CMS*EFV5B 2
C Containment Atmosphere Monitoring 2CMS*EFV6 2
C Containment Atmosphere Monitoring 2CMS*EFV8A 2
C Containment Atmosphere Monitoring 2CMS*EFV8B 2
C Containment Atmosphere Monitoring 2CMS*EFV9A 2
C Containment Atmosphere Monitoring 2CMS*EFV9B 2
C Containment Atmosphere Monitoring 2DER*EFV31 2
C Drywell Equipment Drains 2IAS*EFV200 2
C Instrument Air 2IAS*EFV201 2
C Instrument Air 2IAS*EFV202 2
C Instrument Air 2IAS*EFV203 2
C Instrument Air 2IAS*EFV204 2
C Instrument Air 2IAS*EFV205 2
C Instrument Air 2IAS*EFV206 2
C Instrument Air 2ISC*EFV12 2
C Reactor Vessel Instrumentation
10 CFR 50.55a Relief Request: GVRR-10 Revision 0 (Page 2 of 4)
Component ID Class Category System 2ISC*EFV16 2
C Reactor Vessel Instrumentation 2ISC*EFV19 2
C Reactor Vessel Instrumentation 2ISC*EFV9 2
C Reactor Vessel Instrumentation 2RCS*EFV44A 2
C Reactor Coolant System 2RCS*EFV44B 2
The Nine Mile Point Nuclear Station, Unit 2 (NMP2) complies with the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) 2012 Edition with no Addenda.
3. Applicable Code Requirements
ISTC-3510, Exercising Test Frequency, states that Active Category A, Category B, and Category C check valves shall be exercised nominally every 3 months, except as provided by paras. ISTC-3520, ISTC-3540, ISTC-3550, ISTC-3570, ISTC-5221 and ISTC-5222.
ISTC-3522, Category C Check Valves, ISTC-3522(a) states, in part, "During operation at power, each check valve shall be exercised or examined in a manner that verifies obturator travel by using the methods in para. ISTC-5221." ISTC-3522(c) states "If exercising is not practicable during operation at power and cold shutdowns, it shall be performed during refueling outages."
ISTC-3700, Position Verification Testing, state that Valves with remote position indicators shall be observed locally at least once every 2 year to verify that valve operation is accurately indicated. Where practicable, this local observation should be supplemented by other indications such as use of flow meters or other suitable instrumentation to verify obturator position.
- 4. Reason for Request:
In accordance with 10 CFR 50.55a, "Codes and standards," paragraph (z)(1), relief is requested from the requirements of ASME OM Code ISTC-3510, ISTC-3522, and IST-3700 for the subject valves. The basis of the relief request is that the proposed alternative would provide an acceptable level of quality and safety. The ASME OM Code requires these Excess Flow Check Valves (EFCVs) to be exercised quarterly during plant operation, or if valve exercising is not practicable during plant operation and cold shutdown, it shall be performed during refueling outages.
10 CFR 50.55a Relief Request: GVRR-10 Revision 0 (Page 3 of 4)
The twenty-six (26) EFCVs listed are normally open valves which provide flow to Safety Related instrumentation. Low-Pressure EFCVs are safety-related active components designed to go closed in the event of an instrument line break outside of containment. In the Reference 1 Safety Evaluation Report, NRC granted approval of alternate testing of EFCVs in lines containing process fluids.
EFCVs are installed on instrument lines penetrating containment to minimize leakage in the event of an instrument line failure outside the containment in accordance with Regulatory Guide 1.11. The excess flow check valve is basically a spring-loaded ball check valve.
Since the system is normally in a static condition, the valve ball is held open by the spring.
Any sudden increase in flow through the valve (i.e., line break) will result in a differential pressure across the valve which will overcome the spring and close the valve. The valve is designed to allow some leakage past the seat in the closed position. This leakage will act to equalize pressure across the valve in the event the excess flow condition is corrected, thus allowing the spring to reopen the valve.
At NMP2, these low pressure EFCVs have installed position indication. Functional testing of valve closure is accomplished by venting the instrument side of the valve while the process side is under low pressure and observing the position indicator and by verifying that only a small amount of leakage exits through the vent. The testing described above requires the removal of the associated instrument or instruments from service.
EFCVs are required to be tested in accordance with paragraph ISTC-3522, which requires exercising check valves nominally every 3 months to the positions required to perform their safety functions. ISTC-3522(c) permits deferral of this requirement to every reactor refueling outage. EFCVs are also required to be tested in accordance with ISTC-3700, which requires remote position verification at least once every 2 years.
The EFCVs are classified as ASME Code, Category C and are also containment isolation valves. However, these valves are excluded from 10 CFR Part 50, Appendix J, Section III.C., leakage rate testing due to the size of the instrument lines; therefore, these EFCVs have no safety-related seat leakage criterion.
EFCV testing requires equipment setup and system reconfiguration. Testing during refueling is costly and requires additional dose with no increase in safety as compared to the alternative discussed below.
- 5. Proposed Alternative and Basis for Use:
Nine Mile Point Nuclear Station, Unit 2 (NMP2) is presently testing the referenced EFCVs which are connected to the containment atmosphere on a 24-month frequency. NMP2 EFCVs will be tested on a representative sampling basis (i.e., approximately 20 percent every refueling outage), and that all EFCVs will be tested at least once within a ten-year frequency.
Industry experience, as documented in Topical Report NEDO-32977-A, Excess Flow Check Valve Testing Relaxation, dated June 2000, indicates the ECFVs have a very low failure rate. The NMP2 test experience is consistent with the findings in the NEDO document. The NEDO document indicates that many reported test failures at other plants were related to test methodologies and not actual EFCV failures. An evaluation of the maintenance history and a comparison to the acceptance criteria in NEDO-32977-A concludes that NMP2 has
10 CFR 50.55a Relief Request: GVRR-10 Revision 0 (Page 4 of 4) demonstrated that the low-pressure EFCVs are highly reliable and that failures to isolate are very infrequent (4 out of approximately 286 tests in 22 years). The failure rate of the Unit 2 low pressure EFCVs was also confirmed to be below the highest failure rates presented in NEDO-32977-A.
Thus, the EFCVs at NMP2 have exhibited a high degree of reliability, availability, and the alternate sampling approach provides an acceptable level of quality and safety. Therefore, this proposed alternative is requested pursuant to 10 CFR 50.55a(z)(1).
- 6. Duration of Proposed Alternative:
This request, upon approval, will be applied to the NMP2 fourth 10-year interval, which began on January 1, 2019, and is scheduled to end on December 31, 2028.
- 7. Precedent:
None
- 8.
References:
- 1. Letter from P. Tam (U.S. Nuclear Regulatory Commission) to J. H. Mueller (Niagara Mohawk Power Corporation), "Nine Mile Point Nuclear Station, Unit No. 2 - Authorization of Alternative Regarding Excess Flow Check Valve Testing Frequency (TAC No.
MB1491)," dated September 17, 2001 (ADAMS Accession No. ML012340462)
- 2. Letter from M. Markley (U.S. Nuclear Regulatory Commission) to C. R. Pierce (Southern Nuclear Operating Company, Inc.), "Edwin I. Hatch Nuclear Plant, Units 1 and 2 -
Inservice Testing Program Relief Request and Alternatives for Pumps and Valves - Fifth Ten-Year Interval (CAC Nos. M176238, MF6239, MF6240, MF6241, MF6242, MF6243, MF6244, MF6245, MF6246, and MF6247)," dated December 30, 2015 (ADAMS Accession No. ML15310A406)
- 3. Letter from R. J. Laufer (U.S. Nuclear Regulatory Commission) to B. L. Shriver (PPL Susquehanna, LLC), "Susquehanna Steam Electric Station, Units 1 and 2 - Third 10-Year Interval Inservice Testing (IST) Program Plans (TAC Nos. MC3382, MC3383, MC3384, MC3385, MC3386, MC3387, MC3388, MC3389, MC4421, MC4422)," dated March 10, 2005 (ADAMS Accession No. ML050690239)
- 4. Letter from D. Wrona (U.S. Nuclear Regulatory Commission) to B. Hanson (Exelon Generation Company, LLC), "LaSalle County Station, Units 1 and 2 - Relief from the Requirements of the ASME Code for Operation and Maintenance of Nuclear Power Plants (EPID L-2019-LLR-0004)," dated July 3, 2018 (ADAMS Accession No. ML18163A054)