L-PI-24-030, Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specification 3.8.1
| ML24143A198 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 05/22/2024 |
| From: | Conboy T Northern States Power Co, Xcel Energy |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-PI-24-030, EPID L-2023-LLA-0135 | |
| Download: ML24143A198 (1) | |
Text
1717 Wakonade Drive Welch, MN 55089 May 22, 2024 L-PI-24-030 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 License Amendment Request to Revise Technical Specification 3.8.1 (EPID L-2023-LLA-0135)
References:
- 1) Letter L-PI-23-025, License Amendment Request to Revise Technical Specification 3.8.1, Surveillance Requirement 3.8.1.2, Note 3, dated September 28, 2023. (NRC ADAMS Accession No. ML23271A205)
- 2) Letter L-PI-23-033, Supplement to License Amendment Request to Revise Technical Specification 3.8.1, Surveillance Requirement 3.8.1.2, Note 3, (EPID L-2023-LLA-0135), dated December 5, 2023. (NRC ADAMS Accession No. ML23339A060)
- 3) NRC Email Re: Advanced Listserv Prairie Island Nuclear Generating Plant, Units 1 and 2 - Final Request for Additional Information for LAR to Revise SR 3.8.1.2 Note 3 (EPID: L-2023-LLA-0135), dated April 25, 2024. (NRC ADAMS Accession No. ML24116A253)
In Reference 1 as supplemented by Reference 2, 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 Note 3 of TS Surveillance Requirement (SR) 3.8.1.2 to remove detail that is not needed to ensure operability.
In Reference 3, the NRC identified additional information necessary to complete its review. to this letter responds to the NRC request for additional information. Enclosure 2 to this letter provides a revision to the proposed TS Bases markups provided with Reference 2.
May 22, 2024.
Document Control Desk L-Pl-24-030 Page2 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.
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 penalty of perjury, that the foregoing is true and correct.
Executed on Thomas A. Conboy Site Vice President, Prairie Island
- ar Generating Plant
~orthern States Power Company - Minnesota Enclosure cc:
Administrator, Region 111, USNRC Project Manager, Prairie Island, USN RC Resident Inspector, Prairie Island, USNRC State of Minnesota
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 Section 3.8.1 NRC Request for Additional Information The NRC staff has reviewed the application and supplement and determined that additional information is necessary to complete its review.
Current SR 3.8.1.2 states: Verify each DG starts from standby conditions and achieves steady state voltage > 4084 V and < 4400 V, and frequency > 59.5 Hz and < 60.5 Hz.
Current SR 3.8.1.2 Note 3 states: A modified DG start involving idling and gradual acceleration to synchronous speed may be used for this SR in consideration of manufacturers recommendations. When modified start procedures are not used, the time, voltage, and frequency tolerances of SR 3.8.1.6 must be met.
Revised SR 3.8.1.2, Note 3 would state: A modified DG start may be used for this SR. When modified start procedures are not used, the time, voltage, and frequency tolerances of SR 3.8.1.6 must be met.
In the supplement dated December 5, 2023, the licensee proposed to relocate the details of a modified DG start test to the proposed revised TS Bases and includes the underlying reason and intent of Note 3 and its effect on SR 3.8.1.2 in the revised TS Bases.
Revised TS Bases for SR 3.8.1.2 would state: Note 3 of SR 3.8.1.2 allows for a modified (slow) DG start procedure, which could include idling and/or a longer time for acceleration, that may be used to reduce long-term stress and wear on diesel engines.
LAR section 2.3, Reason for Proposed Changes, states: SR 3.8.1.2, Note 3, contains details that are not necessary to ensure operability; therefore, these details are not required to be in the TS to provide adequate protection of the public health and safety.
LAR section 3.0, Technical Evaluation, states:
The proposed change to SR 3.8.1.2, Note 3, will remove detail from TS that is not necessary to ensure operability. Detail to provide consistent implementation of the TS is located in other licensee-controlled documents. NSPM considers manufacturers recommendations as part of operating and testing procedures and proposed design modifications.
L-PI-24-030 Page 2 of 4 NSPM operating and testing procedures are informed by design specifications, vendor technical manuals, and the operating experience program that has diverse inputs including NRC generic correspondence, notifications from the Institute of Nuclear Power Operations (INPO), and technical bulletins from manufacturers. Therefore, it is not necessary to specify consideration of manufacturers recommendations for DG starting in SR 3.8.1.2, Note 3. The details of what constitutes a modified start, such as idling and acceleration, are more appropriately located in other licensee-controlled documents.
The supplement dated December 5, 2023, states:
The modified start of SR 3.8.1.2 is intended to reduce the stress and wear on the diesel engines by allowing more time for starting than the fast start of SR 3.8.1.6, which requires that the DG starts from standby condition and achieves voltage of at least 3740 V and frequency of at least 58.8 Hz within 10 seconds. The procedures for a modified start (referred to as the slow start surveillance procedures) for the Unit 1 and Unit 2 DGs are different because the DGs were provided by different manufacturers. The most notable difference is that the Unit 1 DG modified start is manually controlled and the Unit 2 DG modified start is built into the DG controls. Specifically, the Unit 1 DG slow start procedures include approximately one minute idling time before manually raising engine speed and the Unit 2 DG slow start procedures include a built-in slow test mode with a slower acceleration as part of the governor control system. There are no planned changes to the Unit 1 or Unit 2 slow start surveillance procedures associated with the proposed license amendment.
In light of recent modifications developed to improve the Unit 2 DGs control systems, it became apparent to NSPM that the level of procedural detail in the TS SR note is not necessary to achieve the intent of the TS SR. The intent of SR 3.8.1.2 is to demonstrate that the DG can be started and achieve the required steady-state voltage and frequency; no time limitations apply. SR 3.8.1.6 is the test that ensures availability of the standby electrical power supply within ten seconds. In addition, the current Note 3 could hinder the incorporation of industry and site operating experience related to DG reliability and could become unintentionally restrictive to future improvements.
The staff notes the following:
- The modified DG start in Note 3 is part of the SR 3.8.1.2 that must be met to ensure the operability of the DG. The modified DG start that the TS allows for SR 3.8.1.2 to ensure the operability of the DG is the one that considers the recommendations of the manufacturer.
Thus, the words in consideration of the manufacturers recommendations, are details that help ensure an adequate modified DG start for SR 3.8.1.2.
- Including the words in consideration of the manufacturers recommendations, in SR 3.8.1.2 Note 3 does not preclude the licensee from considering the diverse inputs that informed NSPM testing procedures, but it is consistent with the use of those words or similar ones in the application and supplement. In addition, including those words in SR 3.8.1.2 Note 3 does not add time limitations to the SR 3.8.1.2 and it still allows meeting the intent of SR 3.8.1.2, which
L-PI-24-030 Page 3 of 4 is to demonstrate that the DG can be started and achieve the required steady-state voltage and frequency.
- The words in consideration of manufacturers recommendations, are included in Prairie Island current SR 3.8.1.3 Note 1.
- In the supplement, the first paragraph quoted above states that the DG modified start includes idling and/or a longer time for acceleration but the terms could in the proposed revised TS Bases seems to indicate the modified DG start does not have to include idling and/or a longer time for acceleration. Also, the supplement states that the modified start of SR 3.8.1.2 is intended to reduce the stress and wear on the diesel engines, but the term may in the proposed revised TS Bases seems to indicate that the intent of the modified start can be something other than to reduce long-term stress and wear on diesel engines.
The staff has the following questions:
RAI-1
As stated above, Section 3.0 of the LAR states NSPM considers manufacturers recommendations as part of operating and testing procedures. Explain why the words in consideration of manufacturers recommendations for the modified DG start in the current SR 3.8.1.2 Note 3 are removed from the TS and not relocated to the TS Bases.
RAI-2
Clarify the use of words could and may in the revised TS Bases for SR 3.8.1.2. Indicate if the modified DG start for each DG has other main steps and outcome that are not captured in the revised TS Bases.
NSPM Response to RAI 1 NSPM concurs that manufacturers recommendations for the specific steps for modified (slow) start of DGs are one of the factors that should inform the DG modified start procedure. Other factors, for example operating experience and DG subject matter expertise, will also inform slow start surveillance procedure steps. To this end, NSPM proposes to revise the Bases markups as shown in Enclosure 2.
NSPM Response to RAI 2 NSPM proposes to modify the Bases markups as shown in Enclosure 2 in order to clarify the wording to better match the intent of the proposed Bases changes.
L-PI-24-030 Page 4 of 4 References
- 1. Letter L-PI-23-025, License Amendment Request to Revise Technical Specification 3.8.1, Surveillance Requirement 3.8.1.2, Note 3, dated September 28, 2023. (NRC ADAMS Accession No. ML23271A205)
- 2. Letter L-PI-23-033, Supplement to License Amendment Request to Revise Technical Specification 3.8.1, Surveillance Requirement 3.8.1.2, Note 3, (EPID L-2023-LLA-0135), dated December 5, 2023. (NRC ADAMS Accession No. ML23339A060)
- 3. NRC Email Re: Advanced Listserv Prairie Island Nuclear Generating Plant, Units 1 and 2 - Final Request for Additional Information for LAR to Revise SR 3.8.1.2 Note 3 (EPID:
L-2023-LLA-0135), dated April 25, 2024.
ENCLOSURE 2 PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specification 3.8.1, Surveillance Requirement 3.8.1.2, Note 3 TECHNICAL SPECIFICATION BASES PAGES (Marked-Up)
(Provided for Information Only)
(2 pages follow)
AC Sources-Operating B 3.8.1 Prairie Island Units 1 and 2 B 3.8.1-13 Revision 261 BASES SURVEILLANCE associated safeguards bus: load rejection; voltage restoration; and REQUIREMENTS load restoration. The voltage restoration portion of the sequence will (continued) connect the DG to the bus if no viable offsite source is available.
The load restoration is accomplished by a series of start permissives separated by 5 second steps. The 5 second steps allow for the starting of the load and voltage recovery prior to starting the next loads which ensures that voltage does not fall below the degraded voltage setting of the bus. The PLC program has the capability to have up to 9 programed load steps which total 45 seconds. Along with a 15 second allowance for the DG to start and come up to rated speed and voltage gives a total transient time of 60 seconds. After 60 seconds the DG is determined to be in a steady state condition.
SR 3.8.1.1 This SR ensures proper circuit continuity for the required offsite AC electrical power supply to the onsite distribution network and availability of offsite AC electrical power. The breaker alignment verifies that each breaker is in its correct position to ensure that distribution buses and loads are connected to their offsite power source, and that appropriate independence of offsite circuits is maintained.
The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.
SR 3.8.1.2 and SR 3.8.1.6 These SRs help to ensure the availability of the standby electrical power supply to mitigate DBAs and transients and to maintain the unit in a safe shutdown condition. The steady state voltage requirement is to allow the DG to accept loads and to maintain the unit in a safe shutdown condition.
To minimize the wear on moving parts that do not get lubricated when the engine is not running, these SRs are modified by a Note
AC Sources-Operating B 3.8.1 Prairie Island Units 1 and 2 B 3.8.1-14 Revision 261 BASES SURVEILLANCE SR 3.8.1.2 and SR 3.8.1.6 (continued)
REQUIREMENTS (Note 2 for SR 3.8.1.2) to indicate that all DG starts for these Surveillances may be preceded by an engine prelube period and followed by a warmup period prior to loading.
In order to reduce stress and wear on diesel engines, some manufacturers recommend a modified start in which the starting speed of DGs is limited, warmup is limited to this lower speed, and the DGs are gradually accelerated to synchronous speed prior to loading. These start procedures are the intent of Note 3, which is only applicable when such modified start procedures are recommended by the manufacturer.
Since SR 3.8.1.6 requires a 10 second start, it is more restrictive than SR 3.8.1.2, and it may be performed in lieu of SR 3.8.1.2. This is the intent of Note 1 of SR 3.8.1.2.
The Surveillance Frequencies are controlled under the Surveillance Frequency Control Program.
SR 3.8.1.3 This Surveillance verifies that the DGs are capable of synchronizing with the offsite electrical system and accepting loads greater than or equal to 90% of the continuous rating of the DG (Ref. 2). The Unit 1 and Unit 2 diesel generators have different loading requirements since their individual loads are different. As an example, the Unit 2 diesel generators supply emergency power to the cooling water pump whereas the Unit 1 diesel generators do not. A minimum run time of 60 minutes is required to stabilize engine temperatures, while minimizing the time that the DG is connected to the offsite source.
The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.
Note 3 of SR 3.8.1.2 allows for a modified (slow) DG start procedure. The slow DG start procedure is intended to reduce long-term stress and wear on the diesel engines and will be informed by manufacturer's recommendations, operating experience, DG subject matter expertise, and other factors. The slow DG start can include idling, a longer time for acceleration, and/or other steps that are different than the fast DG start procedure of SR 3.8.1.6.