ML20255A024

(Ano), Pre-Submittal Meeting with NRC - Request to Extend Allowable Outage Time (AOT) for the Emergency Cooling Pond (ECP)

ML20255A024
Person / Time
Site:	Arkansas Nuclear
Issue date:	09/11/2020
From:	Entergy Operations
To:	Thomas Wengert Plant Licensing Branch IV
Wengert T
References
Download: ML20255A024 (14)

Text

Arkansas Nuclear One (ANO)

Request to Extend Allowable Outage Time (AOT) for the Emergency Cooling Pond (ECP)

Pre-Submittal Meeting with NRC September 17, 2020 1

Agenda Topic Speaker Introductions NRC/ENTERGY/PUBLIC Licensee Presentation Reason for AOT Extension Contingencies for Loss of Normal Supply Risk Insights ENTERGY Examples of Extended AOTs Deterministic vs Risk-Based Application Proposed Submittal Schedule NRC Discussion NRC Opportunity for Public Comment PUBLIC Meeting Adjournment NRC 2

Introductions

• Licensee Attendees

- ENTERGY/Arkansas Nuclear One (ANO) - Licensee

• Riley Keele, David Bice (Regulatory Assurance)

• Vince Bond, Bob Thweatt, Dan Sojka, Ryan Brumwell, Atwood Browning (Projects)

• Bryan Daiber, Tom Hatfield, Grant Flynn (Engineering)

• Scott Thessing (Operations)

- Zachry Nuclear

• Ron Ploof, Charles DeDeaux, Ricky Summitt

- Structural Technologies

• Chris Burton, Anna Pridmore, Jason Alexander 3

Reason for AOT Extension

• By letter dated July 15, 2020 (ML20218A672), Entergy requested relief from ASME B&PVC Section XI, Rules for In-Service Inspection of Nuclear Power Plant Components, Article IWA-4000, subparagraph IWA-4221(b)(1), in order to proactively use a Carbon Fiber Reinforced Polymer (CFRP)

Composite System wrap on the internal surface of ECP supply piping on both ANO units.

• Each supply pipe is more than 2000 feet in length and will require substantial time to install the CFRP wrap.

• The specifics of installation is provided in the aforementioned request for relief and the installation time is well beyond the time allotted for refueling outages.

• The ANO-1 and ANO-2 Technical Specifications (TSs) do not provide a time in which the ECP may be removed from service for maintenance.

4

Reason for AOT Extension (continued)

• Entergy is proposing a 65-day AOT per unit (only one ECP supply pipe will be removed from service at a time) based on the following high-level schedule with five days of time to address unforeseen circumstances discovered during the installation of the CFRP wrap.

• The installation will occur prior and adjacent to a spring refueling outage such that any further delays will be resolved during the respective refueling outage.

Day 1 Isolate and Drain Day 28 2nd SWS Bay Tie-in Day 3 Install 4 Manways Day 36 3rd SWS Bay Tie-in Day 11 Begin CFRP Wrap Day 47 Quality Assurance Day 11 1st SWS Bay Tie-in Day 60 Final Closeout 5

Contingencies for Loss of Normal Supply

• Each safety related Service Water System (SWS) supporting the ANO units consists of two independent trains (per unit).

• The SWS normally takes suction from Lake Dardanelle, but is designed to take suction from a site reservoir (ECP) should a loss of Lake Dardanelle occur.

• Lake Dardanelle inventory is controlled by the Corps of Engineers via a dam system along the Arkansas River.

• With respect to the Dardanelle Dam, the Safety Analysis Report (SAR) includes the following information:

1. The dam is designed to withstand the probable maximum flood (PMF) and associated wind effects

2. Failure is considered to be practically impossible (although assumed to occur)

3. A written agreement between ANO and the Corps requires notification within 10 minutes if lake level is expected to lower below a specified level. 6

Contingencies for Loss of Normal Supply (continued)

• Although a loss of lake is not expected to occur, Entergy plans to install a temporary above ground pipe and diesel-powered pump from the ECP to the SWS capable of supplying normal flow (greater than accident flow requirements) to support continued operation of both SWS trains (note that the accident analysis only assumes one train is available).

• Coordination will occur with the Corps to ensure no activities will be scheduled during the installation window that may adversely affect the Dardanelle Dam.

• Installation will be planned prior to units spring outage to limit ECP temperature and avoid the time of year of elevated tornado activity in Arkansas.

7

Contingencies for Loss of Normal Supply (continued)

• The temporary pump will be tested bi-weekly during the outage.

• Although the temporary supply will not be designed to safety related seismic and tornado requirements, the design will be robust such that it can withstand lesser seismic (0.12g) and wind events.

• Details of contingencies and compensatory measures described above along with others will be provided in the request.

8

Risk Insights

• The request will follow the guidance in Regulatory Guide (RG) 1.174 and RG 1.177 for risk-informed methodology and acceptance criteria.

• Fire-related risk thresholds will be included as required by ANOs Operating License (adoption of NFPA 805).

• Tornado missile protection of the temporary supply will be afforded where dictated by risk results.

• A detailed discussion of risk assumptions and methods will be provided in the request.

• The current overall risk profile indicates that risk will remain acceptable for over 100 days for each unit.

9

Examples of Extended AOTs

• Surry received a 14-day and 45-day AOT extension (each to be used) for main control room (MCR) and emergency switchgear room (ESGR) air-conditioning system (ACS) chilled water piping replacement (SER dated January 23, 2008, ML073480287)

• Susquehanna received a 14-day AOT extension for emergency service water and residual heat removal service water (SER dated January 17, 2020, ML19248A844)

• Seabrook received a 60-day AOT extension (to be used on each train) for the control room air conditioning subsystem to replace refrigerant (SER dated September 17, 1999, ML011920184) 10

Examples of Extended AOTs

• Brunswick received a 9-week (63-day) AOT extension to support upgrade of the Control Room Emergency Ventilation System while relying on non-seismic temporary coolers and barriers (SER dated February 6, 1988, ML020370049)

• Other than Brunswick (CREVS completely inoperable), one train of a two-train system would be inoperable. Both SWS trains at ANO will remain capable of performing the respective specified safety function (with supply from Lake Dardanelle) during the installation window AND will be supported by a non-seismic temporary pump/piping system capable of supply normal and emergency flow requirements.

11

Deterministic vs Risk-Based Application

• Given the wealth of contingency and compensatory measures planned to be established, Entergy intends to submit a deterministic request which includes risk insights.

Although the request may include risk assessments compared to RG 1.174 and/or RG 1.177, this information is intended to provide risk insights only.

• Discussion?

12

Planned AOT Extension Request Schedule

• Estimated Submittal to NRC: November 2020

• Requested NRC Approval Date: December 2021

• Construction Timeframe: Construction is estimated to begin as early as 2022.

13

NRC Discussion 14