ML23349A036
| ML23349A036 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 12/14/2023 |
| From: | Robert Kuntz NRC/NRR/DORL/LPL3 |
| To: | Steinman R Exelon Generation Co |
| References | |
| L-2023-LLA-0171 | |
| Download: ML23349A036 (7) | |
Text
From:
Robert Kuntz Sent:
Thursday, December 14, 2023 6:57 PM To:
rebecca.steinman@constellation.com
Subject:
RE: DRAFT Request for Additional Information RE: Quad Cities Emergency Amendment Related to Unit 1 Diesel Generator Inoperability Ms. Steinman, By letter dated December 13, 2023 (Agencywide Document Access Management System (ADAMS) Accession No. ML23347A217), Constellation Energy Generation, LLC (CEG, the licensee) requested an amendment to the to the Technical Specifications (TS) for Quad Cities Nuclear Power Station Units 1 and 2 (Quad Cities). The proposed amendment would revise required action B.4 of TS 3.8.1, AC Sources - Operating, to allow an extension of the allowed outage time (AOT) to restore an inoperable diesel generator from 7 days to 30 days. The U.S.
Nuclear Regulatory Commission (NRC) staff has determined that additional information is needed to complete its review of the license amendment request (LAR). The NRC staff draft request for additional information is included.
Robert Kuntz Senior Project Manager NRC/NRR/DORL/LPL3 (301) 415-3733 REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST TO REVISE THE TECHNICAL SPECIFICATIONS TO ALLOW EXTENSION FOR TS 3.8.1 REQUIRED ACTION B.4 COMPLETION TIME QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-254 AND 50-265 (EPID NO. L-2023-LLA-0171)
Regulatory Requirements and Guidance Title 10 of the Code of Federal Regulations (10 CFR) Section 50.36, "Technical specifications,"
requires, in part, that the applicants for a license authorizing operation of a production or utilization facility must include in their application proposed TSs in accordance with the requirements of 10 CFR 50.36. 10 CFR 50.36(c) requires that TS include items in five specific categories related to station operation. These categories are (1) Safety limits, limiting safety system settings, and limiting control settings, (2) Limiting conditions for operation (LCOs), (3)
Surveillance requirements (SRs), (4) Design features, and (5) Administrative controls. The proposed change to the Quad Cities TSs relates to the LCO and SRs categories.
10 CFR, Section 50.63, Loss of All Alternating Current Power, requires that each light-water-cooled nuclear power plant to be able to withstand and recover from a station blackout (i.e., loss of the offsite electric power system concurrent with reactor trip and unavailability of the onsite emergency alternating current electric power system) of a specified duration. The 10 CFR 50.63 requirements provide assurance that necessary operator actions can be performed and that
necessary control room -area equipment will be functional under the expected environmental conditions during and following a station blackout, thereby ensuring that the core will be cooled and appropriate containment integrity will be maintained.
NUREG-0800, Branch Technical Position (BTP) 8-8, "Onsite (Emergency Diesel Generators) and Offsite Power Sources Allowed Outage Time Extensions," (ML113640138) provides guidance, from a deterministic perspective, for reviewing an Emergency Diesel Generators (EDGs) outage time extension request up to 14 days. Although the requested extension for the Required Action B.4 completion time exceeds 14 days, for defense-in-depth review purpose, the NRC staff uses the guidance in BTP 8-8 to review the proposed change. It should be noted that the terms allowed outage time (AOT) and completion time (CT) are interchangeable.
Request for Additional Information (RAI) #1 Describe the plant response in case of following scenario:
Total loss of offsite power (LOOP) concurrent with EDG-1 (for connection to Bus 14-1) out of service and the common EDG (EDG-1/2) starts but fails to connect to Bus 13-1, thus resulting in a station blackout (SBO) of Unit 1.
Describe whether the SBO DG-1 can be aligned and connected to Bus 14-1 in requisite time to bring the Unit 1 to Mode 3 or cold shutdown in case of extended LOOP.
RAI #2 Describe the following:
a)
Clarification that the SBO DG will be used as the AAC power source (described in BTP 8-8) during the proposed extended CT.
b)
How frequent the SBO DGs are tested to ensure their availability when required?
c)
When were the most recent SBO DGs successfully tested?
d)
What is the approximate onsite fuel capacity, in terms of days/hours, for operating the EDGs and SBO DGs, before the additional fuel supply from an offsite source is needed?
RAI #3 TS LCO 3.8.1 states, in part:
The following AC electrical power sources shall be OPERABLE:
- d. The opposite unit's DG capable of supporting the equipment required to be OPERABLE by LCO 3.6.4.3, LCO 3.7.4 (Unit 2 only), and LCO 3.7.5 (Unit 2 only).
Describe the impact of the proposed change to the opposite units equipment (Unit 2) supported by EDG-1 (and required to be OPERABLE by LCO 3.6.4.3) during the extended completion time for EDG-1 and how to mitigate such impacts if any.
RAI #4 Section B of BTP 8-8 states, in parts:
The TS must contain Required Actions and Completion Times to verify that the supplemental AC [alternating current] source is available before entering extended AOT.
The availability of AAC [alternate alternating current] or supplemental power source shall be checked every 8-12 hours (once per shift). If the AAC or supplemental power source becomes unavailable any time during extended AOT, the unit shall enter the LCO and start
shutting down within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. This 24-hour period will be allowed only once within any given extended EDG AOT.
The availability of AAC or supplemental power source should be verified within the last 30 days before entering extended AOT by operating or bringing the power source to its rated voltage and frequency for 5 minutes and ensuring all its auxiliary support systems are available or operational.
The TS markup in the LAR does not provide the AAC power source(s) and associated Required Action and Completion Time as a condition to enter the extended CT.
Describe the Required Action and Completion Time of TS 3.8.1, Required Action B.4 when the AAC power source(s) (i.e., SBO DG) becomes unavailable during the extended CT.
RAI #5 Section B of BTP 8-8 states, in part:
Additionally, the staff expects that the licensee will provide the following Regulatory Commitments:
The extended AOT will be used no more than once in a 24-month period (or refueling interval) on a per diesel basis to perform EDG maintenance activities, or any major maintenance on offsite power transformer and bus.
The preplanned maintenance will not be scheduled if severe weather conditions are anticipated.
The system load dispatcher will be contacted once per day to ensure no significant grid perturbations (high grid loading unable to withstand a single contingency of line or generation outage) are expected during the extended AOT.
Component testing or maintenance of safety systems and important non safety equipment in the offsite power systems that can increase the likelihood of a plant transient (unit trip) or LOOP will be avoided. In addition, no discretionary switchyard maintenance will be performed.
TS required systems, subsystems, trains, components, and devices that depend on the remaining power sources will be verified to be operable and positive measures will be provided to preclude subsequent testing or maintenance activities on these systems, subsystems, trains, components, and devices.
Steam-driven emergency feed water pump(s) in case of PWR units, and Reactor Core Isolation Cooling and High Pressure Coolant Injection systems in case of BWR units, will be controlled as protected equipment.
Describe the proposed compensatory actions similar to the above which will be applicable prior to and during the CT extension.
RAI #6 The LAR does not explain why the repairs of EDG-1 needs 30 days to complete. Provide justification for the requested CT extension to 30 days.
RAI #7 The LAR proposed to suspend performance of SRs during the extended EDG AOT. Provide clarification on when the suspended SRs will be completed and describe how the licensee will ensure these SRs are completed as described. For example The proposed TS changes could include the following for each affected SR:
- a. Describe the event or condition where the SR may be suspended.
- b. Describe when past due surveillances will be completed.
(Note: As an example, see precedent 2017 Brunswick amendment (ML17328B072)).
RAI #8 In Attachment 1 of its submittal, the licensee provided risk insights related to the proposed one-time change to the Completion Time in TS Action Statement 3.38.1B. Regulatory Guide (RG) 1.177, Revision 2, Plant-Specific, Risk-Informed Decisionmaking: Technical Specifications, states that changes in CT which result in an incremental conditional core damage probability (ICCDP) of greater than 1 x 10-5 is acceptable if effective compensatory measures of implemented. In its submittal, the licensee provides examples of compensatory measures to protect systems associated with providing AC power. These measures were stated to be recommended and not required.
Provide a list of more specific compensatory measures that shall be performed in order to mitigate any increase in conditional core damage probability (CCDP) with regards to the following systems:
- a. Systems impacting the inoperable EDG, such as SBO or diesel generators. Address maintenance in these systems.
- b. Systems associated with offsite AC power, such as the switchyard. Address maintenance in areas such as the switchyard.
- c. Measures to ensure grid reliability and stability given changing weather conditions.
- d. Systems which provide DC power, such as station batteries, back-up batteries, and any back-up sources of DC power including FLEX and B.5.b.
RAI #9 Provide an analysis of the impact of the extended CT on the risk associated with external hazards, such as seismic activity or weather-related loss of onsite or offsite power.
RAI #10 The proposed note to TS 3.8.1 required action B.4 states, For the Unit 1 DG failure on December 11, 2023, restore the inoperable DG to OPERABLE status within 30 days. This note is missing some pertinent information. Because the DG has already been declared inoperable, the proposed TS note could reflect the actual ending date and time. Additionally, the response to RAIs 1 through 9 above may require identification of compensatory actions. The proposed TS note could include reference to the document that contains the list of compensatory actions required during the extended period. Describe how the proposed changes to the license
(including the proposed note in TS 3.8.1) provide a clearly defined end date of applicability and ensure that any compensatory actions required during the extend completion time are clearly indicated.
RAI #11 In Section 3.2 of the LAR, Risk Insights, the licensee stated that changes would be made within the guidance of Regulatory Guide (RG) 1.177 R2, Plant-Specific, Risk-Informed Decisionmaking: Technical Specifications. In Section 2.3.3.1.d., it is stated that, Component unavailability models should include contributions from random failure, common-cause failure (CCF), test downtime, and maintenance downtime. Common cause failures are also further addressed in Appendix A, Section A-1.3.1.1 which states, contributions from common-cause failures (CCFs) need special attention when calculating the increased risk level R1. If the component is down because of a failure, the common-cause contributions should be divided by the probability of the component being down because of failure since the component is given to be down.
- a. In computing this 30-day completion time for EDG-1, state how CCF is addressed and how it will be adjusted as suggested in the RG 1.177 guidance for component failures.
- b. If it will not be adjusted, justify what methods are to be used to incorporate the potential impact of increased CCF.
Hearing Identifier:
NRR_DRMA Email Number:
2341 Mail Envelope Properties (PH0PR09MB10910DEBC43CABD7A636B6B1A998CA)
Subject:
RE DRAFT Request for Additional Information RE Quad Cities Emergency Amendment Related to Unit 1 Diesel Generator Inoperability Sent Date:
12/14/2023 6:57:02 PM Received Date:
12/14/2023 6:57:00 PM From:
Robert Kuntz Created By:
Robert.Kuntz@nrc.gov Recipients:
"rebecca.steinman@constellation.com" <Rebecca.Steinman@constellation.com>
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