ML12248A232

Summary of Meeting with Duke Energy Carolinas, LLC, to Discuss the Installation of Main Steam Isolation Valves at Oconee Nuclear Station, Units 1, 2 and 3 (ONS 1/2/3)

ML12248A232
Person / Time
Site:	Oconee
Issue date:	09/06/2012
From:	Boska J Plant Licensing Branch II
To:	Duke Energy Carolinas
Boska J
Shared Package
ML12254A421	List: ML12248A232
References
TAC ME8504, TAC ME8505, TAC ME8506
Download: ML12248A232 (24)

Text

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• • • • i< September 6, 2012 LICENSEE: Duke Energy Carolinas, LLC FACILITY: Oconee Nuclear Station, Units 1,2, and 3 SUB,JECT:

SUMMARY

OF AUGUST 16, 2012, MEETING WITH DUKE ENERGY CAROLINAS, LLC, TO DISCUSS THE INSTALLATION OF MAIN STEAM ISOLATION VALVES AT OCONEE NUCLEAR STATION, UNITS 1,2, AND 3 (ONS 1/2/3)(TAC NOS. ME8504, ME8505, AND ME8506)

On August 16, 2012, a Category 1 public meeting was held between the U.S. Nuclear Regulatory Commission (NRC) and representatives of Duke Energy Carolinas, LLC (the licensee) at NRC Headquarters, One White Flint North, 11555 Rockville Pike, Rockville, Maryland. The purpose of the meeting was to discuss the licensee's project to add main steam isolation valves (MSIVs) to the six steam generators at ONS 1/2/3. A list of attendees is provided as Enclosure 1, and the licensee's slides are provided as Enclosure 2.

A previous public meeting on this topic was held on May 24,2012. Refer to the meeting summary dated June 14, 2012, Agencywide Document Access and Management System accession number ML12145A705. In this meeting the licensee presented further information about the location of the steam supply lines to the turbine-driven emergency feedwater pump (TDEFWP) and the controls that would be used for ensuring that the MSIVs are functional during plant operation.

The licensee stated that the steam supply lines from the main steam header to the TDEFWP would not be moved, and would now be located downstream of the MSIVs. The licensee stated that they believed this was acceptable, as the TDEFWP will also be automatically supplied from the auxiliary steam header if the auxiliary steam pressure is greater than the supply from the main steam header. The auxiliary steam header can be supplied from any of the three units, although it is normally supplied from only one selected unit at any given time. The licensee also stated that the EFW systems can be cross-tied among units, allowing EFW to the steam generators to be supplied from a different unit, although operators have to perform the cross-tie in the turbine building. The licensee further stated that the MSIVs would be designed to remain open for a loss of all alternating current (AC) power, as long as they did not depressurize to the low pressure setpoint. The MSIVs would have an automatic closure signal from the Automatic Feedwater Isolation System on low steam pressure sensed upstream of the MSIVs. The NRC staff continued to state some concerns with having the TDEFWP steam supply downstream of the MSIVs. The licensee is aware of the NRC staff's concerns. One possible method would be to submit the design for prior NRC approval, so the licensee could be assured of regulatory approval before starting construction. The licensee stated that there would be no partial stroke test during power operations. The NRC staff agrees that such a test is not required by standard technical specifications, NUREG-1430.

- 2 The licensee stated that for now, the MSIVs would not be credited for any design-basis accidents from Chapter 15 of the Oconee Updated Final Safety Analysis Report (UFSAR), but would be credited for events such as tornados, high-energy line breaks (HELBs), and support of the decay heat removal function of the standby shutdown facility (SSF), using the steam generators. Based on that approach, the licensee stated that they believe there is no need to add a plant Technical Specification for the MSIVs. Surveillance requirements designed to verify that the MSIVs are functional would be located in the selected licensee commitment manual, which is the equivalent of a technical requirements manual. The NRC staff is still considering if there is a need for Technical Specifications. The licensee stated that they believe that they only need NRC approval for the methodology changes associated with inadvertent closure of an MSIV at power, and that the remainder of the installation could be done without prior NRC approval. The licensee stated that a preliminary analysis indicates that the inadvertent closure of the turbine stop valves is the bounding condition, as the turbine stop valves close faster than the MSIVs.

No members of the public were in attendance. Public Meeting Feedback forms were not received. Please direct any inquiries to me at 301-415-2901, or by email to John. Boska@nrc.gov.

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~ J n P. Boska, Senior Project Manager lant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287

Enclosures:

1. List of Attendees

2. Licensee Handout cc w/encls: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION MEETING ATTENDANCE FORM

Subject:

Oconee Nuclear Station, Addition of Main Steam Isolation Valves Date: August 16, 2012 Location: OWFN, room 0-7B4 PLEASE PRINT LEGIBLY ORGANIZATION

Main Steam Isolation Valve License Amendment Request Oconee Nuclear Station August 16, 2012 FOR INFORMATION ONLY

Purpose of the Meeting Establish a mutual understanding of Duke Energys Energy s position on the following:

The acceptability p y of installing g MSIVs upstream p of the Turbine Driven Emergency Feedwater Pump (TDEFWP) steam supply Planned controls for ensuring MSIV functionality FOR INFORMATION ONLY 2

Agenda Introductions (Terry Patterson)

Brief Overview of Main Steam Isolation Valve ((MSIV)) modification (David Hunt)

The acceptability of installing MSIVs upstream of the TDEFWP steam supply (Boyd Shingleton)

Planned controls for ensuring MSIV functionality (Boyd Shingleton)

Closing Remarks (Terry Patterson)

FOR INFORMATION ONLY 3

R Reason for f MSIV M Modification difi ti Satisfies HELB and tornado License Amendment Requests commitment to install MSIVs Enhances Main Steam (MS) System integrity to support decay heat removal function of Standby Shutdown Facility (SSF)

Auxiliary Service Water (ASW) System Reduces the area of targets for tornado missiles that damage the main steam lines Facilitates repair of plant equipment in Turbine Building FOR INFORMATION ONLY 4

D Description i ti off MSIV M Modification difi ti Seismic, tornado-protected enclosure (MSIV Enclosure) will be constructed New piping and valves will be installed in the MSIV Enclosure Main Steam Isolation Valves (MSIVs)

Main Steam Relief Valves (MSRVs)

Atmospheric Dump Valves (ADVs)

Power Operated Atmospheric Dump Valves (POADVs)

FOR INFORMATION ONLY 5

Modification Description FOR INFORMATION ONLY 6

MSIV Enclosure FOR INFORMATION ONLY 7

M i Steam Main St Isolation I l ti Valves V l Designed to close automatically against main steam line break (MSLB) conditions in 2 to 5 seconds after receiving a close signal i l Design reduces likelihood of inadvertent actuation Consequences of inadvertent actuation are bounded by inadvertent closure of Turbine Stop Valve (TSV) based on preliminary analysis of event Remotely operated from the Control Room Passive features of valve increase reliability FOR INFORMATION ONLY 8

Current TDEFWP Operation FOR INFORMATION ONLY 9

Current TDEFWP Operation (AFIS)

FOR INFORMATION ONLY 10

Post Post--MSIV Implementation TDEFWP Operation (AFIS)

FOR INFORMATION ONLY 11

Conclusions The Automatic Feedwater Isolation System (AFIS) currently isolates the steam supply to the TDEFWP on low MS header pressure to mitigate RCS overcooling For an MSLB in F i the th Turbine T bi Building, B ildi EFW may b be available il bl ffrom the affected unit or via the cross tie from another unit For an MSLB in the Auxiliary Building, EFW will be available For inadvertent closure of an MSIV, the remaining MS header continues to provide steam to the TDEFWP Based on the above, installation of the MSIVs does not adversely affect mitigation capability of the EFW System FOR INFORMATION ONLY 12

FOR INFORMATION ONLY 13 Pl Planned d M Method th d to t CControl t l MSIV MSIVs The Turbine Stop Valves will remain the credited MS isolation function for Chapter 15 events and will remain in Technical Specifications New MSIVs enhance MS System integrity to support the Secondary Side Decay Heat Removal function of the SSF ASW System and will be controlled by the Selected Licensee Commitment (SLC) Manual Review of the new ONS MSIV function against the four criterion of 10 CFR 50.36(c)(2)(ii) show that the function should be controlled by a SLC FOR INFORMATION ONLY 14

Review against g criteria of 10CFR50.36(c)(2)(ii)

C i i 1 - Installed Criterion I ll d iinstrumentation i thath iis used d to d detect, and d

indicate in the control room, a significant abnormal degradation g of the reactor coolant p pressure boundary.

Discussion: The new MSIVs are not installed instrumentation

Conclusion:

Criterion 1 not applicable to the MSIVs FOR INFORMATION ONLY 15

Review against g criteria of 10CFR50.36(c)(2)(ii)

Criterion 2 - A A process variable variable, design feature feature, or operating restriction that is an initial condition of a design basis accident or transient analysis that either assumes the f il failure off or presents t a challenge h ll tto th the iintegrity t it off a fission product barrier.

Discussion: Examples of Criterion 2 Tech Specs from NUREG-1430 include core limitations in TS Section 3.1 and 3.2 and RCS limits in temperature temperature, pressure pressure, flow flow, and pressurizer level in TS Section 3.4. These are typically baseline assumptions in accident analyses.

Conclusion:

Criterion 2 not applicable to the MSIVs FOR INFORMATION ONLY 16

Review against g criteria of 10CFR50.36(c)(2)(ii)

Criterion 3 - AA structure structure, system, system or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either ith assumes the th ffailure il off or presents t a challenge h ll to the integrity of a fission product barrier.

Discussion: Mitigation strategy of MSLB is not changed by installing the MSIVs. The TSVs are credited and are noted in Oconee TS 3.7.2 3 7 2 as satisfying Criterion 3 3.

Conclusion:

Criterion 3 not applicable to the MSIVs FOR INFORMATION ONLY 17

Review against g criteria of 10CFR50.36(c)(2)(ii)

Criterion 4 - AA structure, system, or component which operating experience or probabilistic risk assessment has shown to be significant to public health and safety.

Discussion: Examples of Criterion 4 TSs from NUREG-1430 include the Remote Shutdown System, RCS Loops in Modes 4 and 5, the Pressurizer PORVs, and DHR in Refueling.

No systems or components are noted as being included in NUREG-1430 due to risk significance. Preliminary PRA results demonstrate that the new MSIVs are not risk significant for Oconee.

Conclusion:

Criterion 4 not applicable to the MSIVs FOR INFORMATION ONLY 18

Regulatory R l t A Approach h Continue to credit the Turbine Stop Valves Valves, required by TS 3.7.2, for design basis accident mitigation Add New Selected Licensee Commitment ((SLC)) to impose p functionality requirements for MSIVs consistent with the other equipment that is controlled by SLC manual Revise TS 3.3.11 & 13 Bases to indicate that AFIS will automatically close the MSIVs on low MS header pressure FOR INFORMATION ONLY 19

Closing Remarks Installation of the MSIVs will not adversely affect mitigation capability of the EFW System MSIV functionality will be assured by inclusion in the Selected Licensee Commitment manual FOR INFORMATION ONLY 20

ML12254A421 Notice ML12213A512 Summary & Slides ML12248A232 OFFICE DORL/LPL2-1/PM DORL/LPL2-1/LA DORL/LPL2-1/BC DORL/LPL2-1/PM NAME JBoska SFigueroa RPascarelli JBoska DATE 9/5/12 9/5/12 9/6/12 9/6/12