L-PI-24-051, Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specification (TS) Definitions and Adopt Plant Specific Methods for Response Time Testing (Rtt)
| ML24345A206 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/18/2024 |
| From: | Conboy T Northern States Power Company, Minnesota, Xcel Energy |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-PI-24-051, EPID L-2024-LLA-0067 | |
| Download: ML24345A206 (1) | |
Text
1717 Wakonade Drive Welch, MN 55089 December 9, 2024 L-PI-24-051 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant, Units 1 and 2 Docket Nos. 50-282 and 50-306 Renewed Facility Operating License Nos. DPR-42 and DPR-60 Response to Request for Additional Information Regarding Prairie Island 1 & 2 - License Amendment Request to Revise Technical Specification (TS) Definitions and Adopt Plant Specific Methods for Response Time Testing (RTT) (EPID L-2024-LLA-0067)
References:
- 1) Letter L-PI-24-014, License Amendment Request to Revise Technical Specification Definition of REACTOR TRIP SYSTEM (RTS) RESPONSE TIME and Apply Response Time Testing to RTS Trip Functions with Time Delay Assumptions in the Accident Analyses, dated May 22, 2024. (NRC ADAMS Accession No. ML24155A220)
- 2) NRC Email Re: Request for Additional Information RE: Prairie Island, Units 1 and 2 - LAR to Revise TS Definition and Adopt Plant Specific Methods for RTT (EPID: L-2024-LLA-0067), dated November 12, 2024. (NRC ADAMS Accession No. ML24330A050)
In Reference 1, Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter NSPM), submitted a license amendment request (LAR) proposing changes to the Technical Specifications (TS) for the Prairie Island Nuclear Generating Plant (PINGP). The proposed change would revise the definition of REACTOR TRIP SYSTEM (RTS) RESPONSE TIME used in TS Surveillance Requirement (SR) 3.3.1.16 to allow allocation of response times in lieu of testing using the proposed methodology. NSPM also proposes to revise TS Table 3.3.1-1 to apply SR 3.3.1.16 to the RTS trip functions for which the accident analyses include assumptions about time delays.
In Reference 2, the NRC identified additional information necessary to complete its review. to this letter responds to the NRC request for additional information.
The information provided with this letter does not alter the evaluations performed in accordance with 10 CFR 50.92 in Reference 1. In accordance with 10 CFR 50.91(b)(1), a copy of this application, with the enclosure, is being provided to the designated Minnesota official.
Document Control Desk L-Pl-24-051 Page 2 If there are any questions or if additional information is required, please contact Mr. Jeff Kivi at (612) 330-5788.
Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.
I declare under penal y of erjury, that the foregoing is true and correct.
Executed on I'}. 0,
-"J Thomas A Conboy Site Vice President, Prairie Isla Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc:
Administrator, Region Ill, USNRC Project Manager, Prairie Island, USNRC Resident Inspector, Prairie Island, USNRC State of Minnesota
1 of 6 ENCLOSURE 1 PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications (TS) Definition and Adopt Plant Specific Methods for Response Time Testing (RTT)
NRC Request for Additional Information (in italics)
=
Background===
By application of May 22, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24155A220), NSPM, the licensee for Prairie Island Nuclear Generating Plant (PINGP), Units 1 and 2, submitted a license amendment request (LAR) to change Technical Specification (TS). The proposed change would revise the definition of REACTOR TRIP SYSTEM (RTS) RESPONSE TIME used in TS Surveillance Requirement (SR) 3.3.1.16 to allow allocation of response times in lieu of testing using the proposed methodology. NSPM also proposes to revise TS Table 3.3.1-1 to apply SR 3.3.1.16 to the RTS trip functions for which the accident analyses include assumptions about time delays.
Regulatory Basis The regulatory requirements and guidance on which the NRC staff based its acceptance are:
General Design Criterion (GDC) 10 in 10 CFR 50 Appendix A, so far as it relates to fuel integrity during any condition of normal operation, including the effects of anticipated operational occurrences (AOOs).
GDC 15 requirement, so far as it relates to reactor coolant pressure boundary integrity during any condition of normal operation, including the effects of AOOs.
Chapter 15 of the NUREG-0800, Standard Review Plan (SRP) are relevant to the LAR.
Specifically, Chapter 15 discusses the AOOs and postulated accidents and associated criteria for evaluation of transient and accident analyses.
Enclosures 1 and 2 to the LAR provide the transient analysis information for the proposed RTS trip delay times, and addition or removal of SR 3.3.1-1 [sic] for RTS trip delay times testing to applicable RTS trip functions. The information addresses the departure from nucleate boiling ratio (DNBR) acceptance criteria defined in SRP Section 4.4, which includes GDC 10 requirements, and GDC 15 requirements for the reactor coolant pressure boundary limits.
During the review, the NRC staff identified that additional information is needed to complete its review and formulated the following request for additional information (RAI).:
L-PI-24-051 NSPM 2 of 6 RAI-SNSB-1 The table in Section 3.1.5 of Enclosure 1 to the LAR of May 22, 2024, tabulates the proposed reactor trip delay times and the delay times assumed in the accident analyses for nine reactor trip system (RTS) functions. The last sentence in Section 3.1.5 indicates that the proposed delay time in all nine RTS functions is less than the delay time assumed in the accident analyses.
The table in Section 3.1.5 shows that the delay time of the power range high positive rate trip assumed in the accident analysis is 0.60 seconds. This delay time of 0.60 seconds is inconsistent with the equivalent delay time assumed in the design basis accident (DBA) analysis listed on page 14.3-4 of Prairie Island USAR [Updated Safety Analysis Report]
Section 14 (Revision 36), which is 0.50 seconds.
a) Clarify which delay time (0.60 seconds or 0.50 seconds) is assumed in the DBA analysis for the power range high positive rate trip.
b) If the trip delay time assumed in the DBA analysis is 0.50 seconds, the proposed delay time of 0.501 seconds in the table of Section 3.1.5 of the LAR would exceed the value used in the accident analysis. Address acceptability of the proposed trip delay time of 0.501 seconds to meet the GDC 10 requirements for fuel integrity and GDC 15 requirements for the reactor coolant pressure boundary integrity.
NSPM Response to RAI-SNSB-1 a) NSPM recognized the need to analyze a longer assumed trip delay time for the PINGP power range high positive rate trip and contracted Westinghouse Electric to analyze increasing the assumed delay time from 0.50 seconds to 0.60 seconds. This is documented in Letter NSPM-TANL-TM-AA-000005 Rev. 0 which is enclosed with the LAR (Reference 1) as Attachment 7 to the Methodology (Enclosure 2 of Reference 1). NSPM is in the process of updating the PINGP USAR Section 14 discussion of the trip delay time for the power range high positive rate trip to 0.60 seconds.
b) The assumed trip delay time is being updated to 0.60 seconds as noted in a), above.
RAI-EICB-2 In Criterion VI of Document Control of Appendix B to 10 CFR Part 50, it states, in part, that measures shall be established to control the issuance of documents, such as instructions, procedures, and drawings, including changes thereto, which prescribe all activities affecting quality. These measures shall assure that documents, including changes, are reviewed for adequacy and approved for release by authorized personnel. In Criterion III on Document Control of Appendix B to 10 CFR Part 50, it states, in part, that the verifying or checking process shall be performed by individuals or groups other than those who performed the original design, but who may be from the same organization.
L-PI-24-051 NSPM 3 of 6 However, the NRC staff found that the preparer and approver for Enclosure 2 of Proposed Methodology to Eliminate Protection Channel Response Time Testing for Prairie Island Nuclear Generating Plant is the same person. Please clarify if Enclosure 2 was issued and approved according to the licensees quality assurance program to meet Appendix B to 10 CFR Part 50 on Quality Assurance Criteria for Nuclear Power Plants.
NSPM Response to RAI-EICB-2 NSPM contracted Sargent and Lundy (S&L) to develop Enclosure 2 of LAR, which was issued and approved according to quality assurance program requirements to meet Appendix B of 10 CFR Part 50. Namely, the enclosure was performed under the S&L Nuclear Quality Assurance Program (SL-TR-1A) and associated Standard Operating Procedures. The S&L Quality Assurance Program and associated Standard Operating Procedures allow for the Approver to be the same individual as the Preparer if the independence requirements are met for Preparer and Reviewer, which they were for this deliverable. Specifically, S&L procedure allows that the Preparer or the Reviewer may perform the approval function if the individual has been duly authorized by the Process Manager or the Project Manager and the independence requirements for the Reviewer, as applicable, have been met.
RAI-EICB-3 10 CFR 50.36 (3) on surveillance requirements states that surveillance requirements are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the limiting conditions for operation will be met.
On Page 9 of Proposed Methodology to Eliminate Protection Channel Response Time Testing for Prairie Island Nuclear Generating Plant, the NRC staff couldnt locate the basis for the time delays for the Lag Network NM-311 (135 ms) and Bistable Relay Driver NC-303 (65 ms) in Section 4.6 and 4.9 of WCAP-14036-P as stated for the Power Range High Positive Rate.
Please clarify or provide necessary information on delay times for devices which are used in the calculation of delay times in Enclosure 2 but are not included in the LAR itself or WCAP-14036-P.
NSPM Response to RAI-EICB-3 WCAP-14036-P, "Elimination of Periodic Protection Channel Response Time Tests", Section 4.6 (and Table 8-1), identify the response time for level trips as 65 milliseconds (ms) and for flux rate trips as 200 ms. As seen on Attachment 5 to the Methodology (Enclosure 2 of Reference 1), the components making up a level trip and a flux rate trip are identical except that the rate trip includes a lag network (NM-311). The nuclear instrumentation system (NIS) channel is comprised of a detector (response time not applicable), a summing and level amplifier (NM-310; response time <1 ms per WCAP-14036-P Section 4.6), a lag network (only
L-PI-24-051 NSPM 4 of 6 applicable for rate trips), and a bistable relay driver NC-303. The response time of the bistable relay driver (NC-303) is identical to all bistable relay drivers within the NIS and is identified by WCAP-14036-P as a Level Trip Response time of 65ms. Since the only difference between the level trip and the rate trip is the lag network (NM-311), the response time of the lag network can be derived by subtracting the known response time of the level trip from the total response time of the rate trip (200ms - 65ms = 135ms).
RAI EICB-4 10 CFR 50.36 (3) on Surveillance requirements states that Surveillance requirements are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the limiting conditions for operation will be met.
In the Table 5-1 on Page 45 of Attachment 6, Failure Modes & Effects Analysis and on Page 6 of Enclosure 2, the NRC staff found that the rising and falling response times for Baseline for RTL501 Module are not consistent with information provided in Section 5.0 of Attachment 6.
The NRC staff also found that the rising and falling response times for Worst-Case Failures for all modules in Table 5-1 are not consistent with information provided in Section 5.0 of. Please provide adequate additional information to support the calculation results of the final response times listed in Table 5-1.
NSPM Response to RAI-EICB-4 RTL501 The testing documented in Section 4.2 of Attachment 6 (Reference 1) and summarized in Conclusions Section 5.1 apply to a RTL500 mV/I amplifier. PINGP utilizes a RTL501 mV/I amplifier which is similar to the RTL500 with the exception of the absence of the R52/C22 filter present in the RTL500. The summary provided in Table 5-1 has note (20) that indicates the baseline and worst-case failure columns were adjusted to eliminate the response time associated with the absence of the filter circuit.
For the baseline response time for the RTL501 18 ms was removed from the RTL500 baseline to account for the absence of the R52/C22 filter (Rising Time: 56 ms - 18 ms = 38 ms; Falling Time: 35.5 ms - 18 ms =17.5 ms).
For the worst-case failure response time for the RTL501 37 ms was removed from the RTL 500 response time to account for the absence of the R52/C22 filter and the measured additional response time (17 ms Rising Time and 13 ms Falling Time) due to failures of applicable components (C2, C4, C11, C15, C20 and C21) was added (Rising Time: 47 ms -
37 ms +17 ms = 27 ms; Falling Time: 49 ms - 37 ms + 13 ms = 25 ms).
L-PI-24-051 NSPM 5 of 6 The total response time is the summation of the baseline and the worst-case failure columns (Rising Time: 38 ms + 27 ms = 65 ms; Falling Time: 17.5 ms + 25 ms = 42.5 ms)
MTH500 The testing documented in Section 4.3 of Attachment 6 (Reference 1) and summarized in Conclusions Section 5.2 apply to a MTH500 summator. Worst-case failure response time for the MTH500 were due to failures of applicable components (R8 and R7) which added 2.675 ms to the falling transient response and 2.215 ms to the rising transient response. In addition, failures of capacitors (C3.1, C54, C14 and C58) contributed an additional 4.735 ms to the rising response and 5.525 ms to the falling response. The times reported on Table 5-1 for worst-case failures is the sum of the above (Rising Time 2.215 ms + 4.735 ms = 6.950 ms; Falling Time 2.675 ms + 5.525 ms = 8.200 ms).
The total response time is the summation of the baseline and the worst-case failure columns (Rising Time 2.765 ms + 6.950 ms = 9.715 ms; Falling Time 3.215 ms + 8.200 ms = 11.415 ms).
SGU501 The testing documented in Section 4.4 of Attachment 6 (Reference 1) and summarized in Conclusions Section 5.3 apply to a SGU501 function generator. Worst-case failure response time for the SGU501 were due to failures of applicable components (F1.1, R14.1, R8 and RN6) which added 9.8 ms to the falling transient response and 49.6 ms to the rising transient response. In addition, failures of capacitors (VR1.1, R15.1, C3.1, C103, C403, C32, C33, C6 and C29) contributed an additional 49.8 ms to the rising response and 13.6 ms to the falling response. The times reported on Table 5-1 for worst-case failures is the sum of the above (Rising Time 49.6 ms + 49.8 ms = 99.4 ms; Falling Time 9.8 ms + 13.6 ms = 23.4 ms).
The total response time is the summation of the baseline and the worst-case failure columns (Rising Time 41.0 ms + 99.4 ms = 140.4 ms; Falling Time 14.8 ms + 23.4 ms = 38.2 ms).
SAM/DAM503 The testing documented in Section 4.5 of Attachment 6 (Reference 1) and summarized in Conclusions Section 5.4 apply to a SAM/DAM503 comparator. Worst-case failure response time for the SAM/DAM503 were due to failures of applicable components (R104, R105, R107 and R108) which added 1 µs to the falling transient response and 28 µs to the rising transient response. In addition, failures of capacitors (C106) contributed an additional 45.5 µs to the rising response and 0.7 µs to the falling response. The times reported on Table 5-1 for worst-case failures is the sum of the above (Rising Time 28 µs + 45.5 µs = 73.5 µs; Falling time 1 µs
+ 0.7 µs = 1.7 µs).
The total response time is the summation of the baseline and the worst-case failure columns (Rising time 385.0 µs + 73.5 µs = 458.5 µs; Falling time 88.5 µs + 1.7 µs = 90.2 µs).
L-PI-24-051 NSPM 6 of 6 References
- 1. Letter L-PI-24-014, License Amendment Request to Revise Technical Specification Definition of REACTOR TRIP SYSTEM (RTS) RESPONSE TIME and Apply Response Time Testing to RTS Trip Functions with Time Delay Assumptions in the Accident Analyses, dated May 22, 2024. (NRC ADAMS Accession No. ML24155A220)
- 2. NRC Email Re: Request for Additional Information RE: Prairie Island, Units 1 and 2 -
LAR to Revise TS Definition and Adopt Plant Specific Methods for RTT (EPID: L-2024-LLA-0067), dated November 12, 2024. (NRC ADAMS Accession No. ML24330A050)