ML16021A345
| ML16021A345 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 01/29/2016 |
| From: | Jeffrey Whited Plant Licensing Branch II |
| To: | Markley M Plant Licensing Branch II |
| Whited J, NRR/DORL/LPLII-1 | |
| References | |
| TAC MF6365, TAC MF6363, TAC MF6364 | |
| Download: ML16021A345 (5) | |
Text
UNITED STATE$
NUCLEAR REGl.JLATORY COMMISSION IJl.IASHINGTON, D.C. 20555-0001 January 29, 2016 MEMORANDUM TO:
Michael T. Markley, Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation FROM:
Jeffrey A. Whited, Proj.ect Manager~ A ~
Plant Licensing Branch 11-1 WV '
SUBJECT:
Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3, DRAFT REQUEST FOR ADDITIONAL INFORMATION RE: LICENSE AMENDMENT TO ADD HIGH FLUX TRIP FOR 3 REACTOR COOLANT PUMP OPERATION (TAC NOS. MF6363, MF6364, AND MF6365)
The attached draft request for additional information (RAI) was transmitted on January 21, 2016, to Duke Energy Carolinas, LLC (Duke, the licensee). This information was tral'")smitted in order to clarify the licensee's license amendment request (LAR) submitted by letter dated May 19, 2015, as supplemented by letter dated August 20, 2015, for Oconee Nuclear Station Units 1, 2, and 3 (ONS). In the proposed LAR the licensee requested to add a High Flux trip for 3 reactor coolant pump operation to the ONS Technical Specifications. During a clarification call on January 28, 2016, the NRC staff agreed to re-word RAl-3 to provide clarification. The revised RAl-3 is included in the attachment.
The draft RAls were sent to the licensee to ensure that the questions are understandable, the regulatory basis for the questions are clear, and to determine if the information was previously docketed. Duke intends to respond to these RAls by March 4, 2016. This memorandum and the attachment do not convey or represent an NRC staff position regarding the licensee's request.
Docket Nos. 50-269, 50-270, and 50-287
Attachment:
Draft RAI cc w/attachment: Distribution via Listserv
DRAFT REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST HIGH FLUX TRIP FOR 3 RCP OPERATION OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 DOCKET NOS. 50-269. 50-270, AND 50-287 By letter dated May 19, 2015, 1 as supplemented by letter dated August 20, 2015,2 Duke Energy Carolinas, LLC., (Duke) requested a license amendment to add a High Flux trip for three reactor coolant pump (RCP) operation to the Technical Specifications (TS) for the Oconee Nuclear Station, Units 1, 2, and 3 (ONS). The request for additional information (RAI) questions listed below are needed to support U.S. Nuclear Regulatory Commission (NRC) staff's continued technical review of the proposed TS change.
RAI- 01 The proposed Nuclear Overpower-High Setpoint Trip function allowable value in TS Table 3.3.1-1 has a trip setpoint valid for four RCP operation (s105.5 percent(%) Reactor Thermal Power (RTP)) and a trip setpoint for three RCP operation (s80.5% RTP). After going to three RCP operation, overpower protection is initially provided by the Nuclear Overpower
- Flux/Flow/Imbalance trip function until su_ch a time that the three RCP allowable value is manually entered as the trip setpoint. In its Technical Evaluation provided in Section 4 of the license amendment request (LAR), Duke states, in part, that:
The existing overpower protection for three RCP operation is the Nuclear Overpower Flux/Flow/Imbalance trip function. However, if [Reactor Coolant System] RCS flow were to increase, as it would for an overcooling event such as a steam line break accident described in UFSAR Chapter 15.17, the flux/flow/imbalance trip setpoint would increase. This increase would result in either a delayed reactor trip or avoidance of a reactor trip altogether.
If the RCS flow situation is such that there could be an "avoidance of a reactor trip altogether,"
what are the current alternate trip protection functions available?
RAI- 02 In its LAA, Duke proposed Limiting Condition for Operation (LCO) 3.4.4.b, which restricts thermal power to S75% when only three RCPs are operating and requires the allowable value of the Nuclear Overpower-High,Setpoint Trip function to be reset for three RCPs operating. Duke also proposed a new Condition A to TS 3.4.4 which specifies a 10 hour1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> COMPLETION TIME to perform this reset. The 10 hour1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> COMPLETION TIME is consistent with the Davis-Besse Nuclear Power Station Unit 1 TS, which was referenced as a precedent in Duke's LAR.
1 Agencywide Doc;uments Access and Management System (ADAMS) Accession No. ML15146A056.
2 ADAMS Accession Number ML152398290.
Attachment Other than the precedent discussed above, please provide additional specific factors considered in the bases for the selection of this 1 O hour COMPLETION TIME.
RAl-03 In its response to Information Request-4, provided by letter dated August 20, 2015, Duke provided an explanation for the proposed TS allowable value setpoint of 80.5% RTP, by stating, in part, that:
The 5.5% RTP delta is simply added to the maximum power level allowed for three RCP operation, which is 75% RTP. Adding 5.5% RTP to 75% RTP results in the proposed high flux trip setpoint of 80.5% RTP.
Duke also provided the following formula:
<t>m ;? <t>sp +trip setpoint uncertainty allow~nce Where
<t>m =flux measured at excore detectors adjusted for transient effects (e.g.,
downcomer attenuation) and excore detector calibration tolerances,
<t>sp =Technical Specification allowable value trip setpoint Trip setpoint uncertainty = current analysis assumes 1.0% RTP for convenience since that is the old analog RPS trip bistable uncertainty and it bounds the uncertainty on the setpoint in the digital RPS. There is no uncertainty on the trip setpoint in the digital RPS.
Please provide information (such as an uncertainty calculation) to demonstrate that instrument uncertainty has been accounted for in the establishment of this setpoint. The information provided should show how associated instrument Total Loop Uncertainty (TLU) was considered for the new setpoint.
RAl-04 In Section 2 of the LAR, Duke states, in part, that:
The three (3) RCP trip will provide protection for power excursion events initiated from three (3) RCP operation, most notably the small steam line break *accident Please provide a list of accidents discussed in the UFSAR that are initiated from three RCP operation (not including the small steam line break (SSLB) since it's thoroughly discussed in the
- application). Please also briefly describe the impact on these accidents once the new three RCP Nuclear Overpower-High setpoint trip is implemented.
RAl-05 In its response to NRC Information Request-3, provided by letter dated August 20, 2015, Duke states, in part, that:
The analysis of the three RCP SSLB with the proposed high flux trip setpoint for when three RCPs are operating demonstrates that true core power is significantly reduced before reactor trip occurs.
With the new trip implemented, please estimate the time when the trip is expected to occur and the maximum actual core power for the current limiting case in the UFSAR. Would changing any of the initial conditions cause a significant delay or avoid exceeding the new trip setpoint completely? If so, would any of these cases be the limiting DNB case for 3 RCP operation?
January 29, 2016 MEMORANDUM TO:
Michael T. Markley, Chief
. Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation FROM:
Jeffrey A. Whited, Project Manager /RA/
Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
SUBJECT:
OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3, DRAFT REQUEST FOR ADDITIONAL INFORMATION RE: LICENSE AMENDMENT TO ADD HIGH FLUX TRIP FOR 3REACTOR COOLANT PUMP OPERATION (TAC NOS. MF6363, MF6364, AND MF6365)
The attached draft request for additional information (RAI) was transmitted on January 21, 2016, to Duke Energy Carolinas, LLC (Duke, the licensee). This information was transmitted in order to clarify the licensee's license amendment request (LAR) submitted by letter dated May 19, 2015, as supplemented by letter dated August 20, 2015, for Oconee Nuclear Station Units 1, 2, and 3 (ONS). In the proposed LAR the licensee requested to add a High Flux trip for three reactor coolant pump operation to the ONS Technical Specifications. During a clarification call on January 28, 2016, the NRC staff agreed to re-word RAl-3 to provide clarification. The revised RAl-3 is included in the attachment.
The draft RAls were sent to the licensee to ensure that the questions are understandable, the regulatory basis for the questions are clear, and to determine if the information was previously docketed. Duke intends to respond to these RAls by March 4, 2016. This memorandum and the attachment do not convey or represent an NRC staff position regarding the licensee's request.
Docket Nos. 50-269, 50-270, and 50-287
Attachment:
Draft RAI cc w/attachment: Distribution via Listserv DISTRIBUTION:
PUBLIC RidsNrrDorlDpr Resource RidsNrrDorllpl2-1 Resource RidsNrrDssStsb Resource EEagle, NRR MChernoff, NRR Accession No.: ML16021A345 OFFICE LPL2-1/PM NAME JWhited DATE 01 /29/16 LPL2-1 R/F RidsNrrPMOconee Resource RidsNrrDeEicb Resource RidsNrrDssSrxb Resource JBorromeo, NRR OFFICIAL RECORD COPY