L-24-066, Response to Request for Additional Information Regarding 10 CFR 50.55a Request Number VR-9, Feedwater Check Valve Exercising Test Frequency
| ML24106A007 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 04/15/2024 |
| From: | Penfield R Vistra Operations Company |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-24-066 | |
| Download: ML24106A007 (1) | |
Text
L-24-066 April 15, 2024 A TIN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Perry Nuclear Power Plant, Unit No. 1 Docket No. 50-440, License No. NPF-58 Perry Nuclear Power Plant Rod L. Penfield Site Vice President 10 Center Road Perry, Ohio 44081 Office: 440.280.5382 10 CFR 50.55a Subject Response to Request for Additional Information Regarding 10 CFR 50.55a Request Number VR-9, Feedwater Check Valve Exercising Test Frequency (EPID L-2023-LLR-0066)
By letter dated December 8, 2023 (Accession No. ML23345A086), Energy Harbor Nuclear Corp. submitted to the Nuclear Regulatory Commission (NRC) Alternative Request VR-9 that proposed an alternative to the Inservice Testing (1ST) Program requirements at Perry Nuclear Power Plant, Unit No. 1 (PNPP), for the testing frequency of certain valves due to hardship or unusual difficulty without compensating increase in level of quality or safety.
Energy Harbor Nuclear Corp. proposed to perform the water leak rate testing of four feedwater header containment isolation check valves in the two feed water lines at PNPP on a staggered basis, such that two check valves of a single feedwater line are tested each refueling outage.
Effective March 1, 2024, the facility operating license for PNPP was transferred from Energy Harbor Nuclear Generation LLC (owner) and Energy Harbor Nuclear Corp. (operator) to Energy Harbor Nuclear Generation LLC (owner) and Vistra Operations Company LLC (operator) (Accession No. ML24057A092). Upon completion of this license transfer, Vistra Operations Company LLC assumed the responsibility for all licensing actions under NRC review at the time of the transfer and requested that the NRC continue its review of these actions (Accession No. ML240,54A498).
By electronic mail dated March 14, 2024, the NRC staff requested additional information in order to complete its review of the proposed alternative. The requested information is attached.
There are no regulatory commitments contained in this submittal. If there are any questions, or if additional information is required, please contact Jack Hicks, Senior Manager, Fleet Licensing, at (254) 897-6725 or jack.hicks@luminant.com.
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Perry Nuclear Power Plant, Unit No. 1 L-24-066 Page 2
Attachment:
Response to Request for Additional Information cc:
NRC Region III Administrator NRC Resident Inspector NRR Project Manager
Attachment L-24-066 Response to Request for Additional Information Page 1 of 6 By letter dated December 8, 2023 (Accession No. ML23345A086), Alternative Request VR-9 was submitted to the Nuclear Regulatory Commission (NRC) that proposed an alternative to the Inservice Testing (IST) Program requirements at Perry Nuclear Power Plant, Unit No. 1 (PNPP), for the testing frequency of certain valves due to hardship or unusual difficulty without compensating increase in level of quality or safety. The proposed alternative was to perform the water leak rate testing of four feedwater header containment isolation check valves in the two feedwater lines at PNPP on a staggered basis, such that two check valves of a single feedwater line are tested each refueling outage. By electronic mail dated March 14, 2024, the NRC staff requested additional information to support the review of the proposed alternative.
The requested information is provided below. The request for additional information (RAI) is presented in bold font, followed by the Vistra Operations Company LLC response.
RAI-EMIB-1 In Table 1 of Alternative Request VR-9, the licensee provides the results of leakage testing of the four check valves within the scope of the request from PNPP refueling outage 1R13 (2011) to present. The licensee notes that acceptable testing results have been obtained during refueling outage 1R19 (2023) after having not performed the testing in refueling outage 1R18 (2021) as permitted by authorized request VR-7 (ML21031A002) and supplement (ML21053A010). The licensee asserts that these leakage testing results support the request for a staggered testing frequency of the four feedwater header containment isolation check valves within the scope of Alternative Request VR-9. Please describe the plans to evaluate the trends of the leakage testing results to determine the appropriate feedwater line to select to begin the staggered testing frequency proposed in Alternative Request VR-9.
Response
Review of trend data indicates that both feedwater lines perform in a reasonably equal manner. As such, testing would align with division outage schedules to optimize system drains and As Low As Reasonably Achievable (ALARA) principles. Testing of the A feedwater line would occur in 1R20 (2025) and testing of the B feedwater line in 1R21 (2027).
RAI-EMIB-2 Alternative Request VR-9, Section 4.0, Reason for Change, on page 2 of 5, second paragraph, states that:
The three types of tests for these check valves are exercise open, exercise close, and water leak rate. Exercise open testing is performed by verifying expected feedwater flow into the reactor vessel using control room instruments and is not a part of this request. Water leak rate testing satisfies the exercise close (EC) test requirements of the inservice testing program and can only be performed during prolonged shutdowns when
Attachment L-24-066 Page 2 of 6 other sources of reactor water level control are available and area radiation levels are reduced. As such, testing during a refueling outage is necessary in accordance with ISTC-3522(c).
ASME OM Code, Subsection ISTC, paragraph ISTC-3522, Category C Check Valves, subparagraph (a) states in part that during operation at power, each check valve shall be exercised or examined in a manner that verifies obturator travel by using the methods in paragraph ISTC-5221, Valve Obturator Movement. Explain whether Alternative Request VR-9 proposes any alternative method for verifying valve obturator movement.
Response
Alternative Request VR-9 does not propose an alternative method for verifying valve obturator movement. Water leak rate testing is the method currently employed at PNPP to verify valve closure and would continue to be used as described in the request. This request seeks only to change the frequency of the exercising testing required by ISTC-3510, Exercising Test Frequency.
RAI-EMIB-3 Alternative Request VR-9, Section 4.0, Reason for Request, on page 2 of 5, last paragraph, states that:
Performance of the water leak rate test requires qualified leak rate contractors, as well as carpenters to erect scaffolding. Depending on the leakage results, supplemental visual inspections may be required to support testing. This test is performed via test rig by routing an air supply to each of the feedwater check valve (FWCV) inspection appendages.
When air is admitted through the FWCVs, personnel can perform a visual inspection of the disc and seating surfaces using a borescope that is inserted through a drain connection on the bottom of each valve. The total accumulated dose for all testing and maintenance activities for these evolutions is estimated at 4,000 mrem. Testing during refueling will require additional dose resulting in a hardship without a compensating increase in the level of quality and safety.
The PNPP Fourth 10-Year Interval IST Program (ML20045E972) includes containment isolation valves 1B21-F032A/B and 1N27-F559A/B with testing to be performed every refueling outage with Refueling Outage Justification (RO-12). RO-12 states these valves are the feedwater inboard and outboard containment isolation valves. The Feedwater System is the normal method of level control for the reactor vessel. Testing of these valves can only be performed during prolonged shutdowns when other sources of level control are available and area radiation levels are reduced. Therefore, quarterly or cold shutdown testing is impractical due to prolonged system shutdowns and unnecessary exposure to radiation.
Attachment L-24-066 Page 3 of 6 Please clarify and explain the change of philosophy at PNPP from Refueling Outage Justification (RO-12) to the proposed alternative testing as described in the Alternative Request VR-9.
Response
The purpose of Refueling Outage Justification RO-12 is to document the justification for performance of the testing during a refueling outage in lieu of quarterly (online) or during a cold shutdown in accordance with ISTC-3522(c). There is no change in this philosophy. This Refueling Outage Justification would still be utilized to document that performance of this testing occurs only during refueling outages. Alternative Request VR-9 would still require performance of this test during refueling outages but alters the frequency from every refueling outage to every other refueling outage for a feedwater line. As clarified in the response to RAI-EMIB-1 above, testing of the A feedwater line would occur in 1R20 (2025) and testing of the B feedwater line in 1R21 (2027).
RAI-EMIB-4 PNPP Fourth 10-Year Interval IST Program (ML20045E972), Inservice Testing for the Check Valves B21-F032A/B and 1N27-F559A/B (Page 3.4-81, Note 13 (Page 3.5-2) states:
The 200 gpm [gallons per minute] leak rate test on Feedwater check valves F032A/B and F559A/B is based on Appendix A to Calculation 3.2.15.7 Feedwater Line Break Accident; letter PY-CEI/NRR-2370L dated March 4, 1999; the NRC Safety Evaluation for Amendment 105 dated March 26, 1999 (PY-NRR/CEI-0964L); an NRC Clarification Letter on Amendment 105, dated April 27, 1999 (PY-NRR/CEI-0976L); the Exception to Regulatory Guide [RG]
1.163 Performance Based Containment Leak-Test Program provided for the Feedwater check valves (see USAR Table 1.8-1 and Technical Specification 5.5.12); and Calculation N27-054 Feedwater Check Valve Leak Test Acceptance Criteria. If the check valves do not pass the water leak test acceptance criteria curve within Calculation N27-054 which was developed to meet the intent of OM Code, paragraph ISTC-3630(b)(4), then a visual examination using a fiberscope is performed to verify significant orifice seat defect(s) do not exist. This inspection includes lifting the check valve disc up off its seat. Significant observed defects or any leak rate test results equivalent to more than 200 gpm at 1.1 Pa require additional investigation/repair and retest per ISTP program requirements.
- a. Check valves 1B21-F032A/B and 1N27-F559A/B are containment isolation valves.
Please clarify and explain the use of ASME OM Code, paragraph ISTC-3630, subparagraph (b)(4), which is for Leakage Rate for Other Than Containment Isolation Valves.
Attachment L-24-066 Page 4 of 6
Response
Technical Specification (TS) 5.5.12, Primary Containment Leakage Rate Testing Program, requires a program to be established to implement the leakage rate testing of primary containment as required by 10 CFR 50.54(o) and 10 CFR 50, Appendix J, Option B as modified by approved exemptions. TS 5.5.12 also lists program exceptions. One of the program exceptions identified is that the containment isolation check valves in the Feedwater penetrations are tested per the IST Program. This exception was made by Amendment 105.
These containment isolation valves are not tested under the Appendix J program. Therefore, Paragraph ISTC-3630, subparagraph (b)(4), is used to show that the valves close, meeting their safety function.
- b. The current PNPP technical specification (TS) does not include RG 1.163. Please clarify and explain the basis for taking exception to RG 1.163, which has been changed in PNPP TS 5.5.12 to NEI 94-01, Revision 3-A, with conditions and limitations in NEI 94-01, Revision 2-A.
Response
IST Program Note 13 provides the historical basis for the leak rate test acceptance criteria, listing a series of submittals that resulted in Amendment 105 to the PNPP Technical Specifications and the historical exception taken to RG 1.163.
The reference to RG 1.163 was subsequently replaced by the reference to Nuclear Energy Institute (NEI) 94-01, Revision 3-A, with the conditions and limitations specified in NEI 94-01, Revision 2-A when Amendment 185 (Accession No. ML19022A324) was implemented at PNPP. Amendment 185 removed two program exceptions from TS 5.5.12 but did not impact the exception for the containment isolation check valves in the Feedwater penetrations.
RAI-EMIB-5 Alternative Request VR-9, Section 5, Proposed Alternative and Basis for Use, second paragraph, states in part:
By letter dated March 26, 1999 (ML021840396), the NRC staff approved Amendment 105 for the Perry Nuclear Power Plant. The amendment revised TS 5.5.12, Primary Containment Leakage Rate Testing Program, to state that the feedwater check valves will be tested in accordance with the Inservice Testing Program (TS 5.5.6).
The referenced Safety Evaluation for Amendment 105 dated March 26, 1999 (ML021840396), Section 1, Introduction, third paragraph states:
The licensees letter of January 6, 1999, included a proposed exemption to the leak rate testing requirements of Appendix J to 10 CFR Part 50, for the feedwater system check valves. The licensee proposed to conduct a visual examination of the check valves in lieu of leak rate testing. During the
Attachment L-24-066 Page 5 of 6 review process, the staff and the licensee concluded that performance of a leak rate test of the check valves was a superior method to demonstrate valve operability as opposed to a visual examination. Performance of a leak rate test would satisfy the requirements of Appendix J and preclude the need for an exemption. In the licensees letter of March 4, 1999, the licensee committed to conduct leak rate testing of the check valves consistent with Appendix J requirements and acknowledged that an exemption to Appendix J was no longer necessary.
Please clarify and explain that Alternative Request VR-9 and PNPP Fourth 10-Year IST Program (ML20045E972) do not mention meeting Appendix J for containment isolation check valves 1B21-F032A/B and 1N27-F559A/B, whereas the last sentence in the above paragraph states that the licensee committed to conduct leak rate testing of check valves per Appendix J.
Response
As described in the above response to RAI-EMIB-4.a, these containment isolation check valves are not leak rate tested under the Appendix J program. However, the leak rate testing is consistent with Appendix J requirements.
The following commitment was made in the March 4, 1999, letter (PY-CEI/NRR-2370L, Accession No. ML20207K094):
Generic Letter (GL) 89-04 Position 3 Back Flow Testing of Check Valves notes that tests on check valves that perform a safety function in the closed position to prevent reversed flow should be performed. Category C tests on such safety function check valves were described as needing to prove that the disc closes on its seat. Two example methods discussed in GL 89-04 for such safety function Category C tests are visual observations or leak rate testing. It is proposed that the Feedwater containment isolation check valves be Category C tested for their safety function at an appropriate frequency as determined by the Inservice Testing Program (ISTP). Leak rate testing will satisfy the exercise closed (EC) test requirements of the ISTP. The EC testing will include a water leak rate test, with an acceptance criteria of 200 gallons per minute per Feedwater penetration, when tested at 1.1 Pa.
This commitment was assigned an internal tracking number of L02424, which is listed in the IST Program under Section 1.4. This provides a link between the IST Program and the commitment.
In Section 3.1, Impact on Containment Isolation Provisions, of the safety evaluation (SE) for Amendment 105, the NRC staff described the review related to leak rate testing of the feedwater check valves. The staff found the proposed leak rate testing of the feedwater check valves acceptable because it is consistent with the requirements of Appendix J to 10 CFR 50.
The SE referred to Option A of Appendix J in this discussion; however, by letter dated April 27,
Attachment L-24-066 Page 6 of 6 1999 (Accession No. ML021840380), the NRC staff issued a clarification to the SE for Amendment 105 that included the following paragraph:
Finally, discussions with your staff identified concerns about our SE referencing Option A, Prescriptive Requirements, of 10 CFR 50, Appendix J. The staff understands that Perry has adopted Option B, Performance-Based Requirements, of 10 CFR 50, Appendix J. The references are intended to describe the adequacy of the Perry seal water system and do not limit, or restrict, your use of the performance-based testing requirements of Option B.
Table 3.1-1 of the IST Program identifies that containment isolation valves will be seat leak tested in accordance with 10 CFR 50, Appendix J, Option B, with exceptions as detailed in TS 5.5.12. One of the exceptions noted in TS 5.5.12 relates to the containment isolation check valves in the Feedwater penetrations. As stated in the response to RAI-EMIB-4.a, TS 5.5.12 provides an exception that allows containment isolation check valves in Feedwater penetrations to be tested in accordance with the IST program.
Therefore, the Alternative Request VR-9 and PNPP Fourth 10-Year IST Program do not mention Appendix J for containment isolation check valves 1B21-F032A/B and 1N27-F559A/B.
RAI-EMIB-6 PNPP Feedwater Containment Isolation Check Valves 1B21-F032A/B and 1N27-F559A/B are piston check valves. Table 1 of Alternative Request VR-9 provides Leakage Acceptance Criteria for these containment isolation check valves as 200 gpm, which is in the high range. The licensee is requested to provide the maintenance history of these check valves.
Response
Amendment 105 revised the design and licensing basis of containment isolation valves in the feedwater system. Since the implementation of Amendment 105, no maintenance has been required on the feedwater containment isolation check valve internals.