ML042790480
| ML042790480 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/23/2004 |
| From: | Rosalyn Jones Duke Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML042790480 (5) | |
Text
Duke RON A.
JONES r SPower Vice President A Duke Energy Company Oconee Nuclear Site Duke Power ONOI VP / 7800 Rochester Highway Seneca, SC 29672 864 885 3158 864 885 3564 fax September 23, 2004 U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Document Control Desk
Subject:
Oconee Nuclear Station Docket Numbers 50-269, 270, and 287 Followup to Meeting on Defense in Depth and Diversity Assessment Associated with the Digital Upgrade of Oconee's Reactor Protective System and Engineered Safeguards Protective System On July 1, 2003, Duke Energy Corporation (Duke) met with the Nuclear Regulatory Commission (NRC) to discuss Duke's March 20, 2003, submittal of a defense-in-depth and diversity (D-in-D&D) assessment associated with the planned digital upgrade of the reactor protective system (RPS) and the engineered safeguards protective system (ESPS) at Oconee Nuclear Station (ONS).
Duke requested the NRC to review and approve the D-in-D&D assessment associated with a future License Amendment Request (LAR) for the RPS/ESPS digital modification in advance of the LAR to allow Duke to finalize design requirements for the modification. At the time of the submittal, Duke planned to implement the modification on Unit 3 during the Fall 2004 outage and had requested a June 30, 2003, approval date.
However, at about the time of the July 1, 2003, meeting, Duke deferred the modification.
The first implementation of this modification is now scheduled for Unit 1 during the Fall 2006 outage.
During the July 1, 2003, meeting Duke presented the results of the D-in-D&D assessment which demonstrated that the Oconee design has significant defense-in-depth and diversity to withstand an assumed software common mode failure (SWCMF) of the digital RPS and the ESPS.
The existing Diverse Scram System (DSS) successfully mitigates many of the transients and accidents of concern.
The acceptance criteria were met for all transients and accidents with the exception of the Large Break Loss of Coolant Accident (LBLOCA).
For the LBLOCA, the assumed SWCMF of the automatic ESPS actuation of the Low Pressure Injection (LPI) System causes an
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September 23, 2004 Page 2 unacceptable delay in the delivery of the emergency core coolant.
Rather than add a diverse LPI actuation to mitigate this beyond design basis event, Duke justified the elimination of the LBLOCA event from consideration for this assessment.
This justification takes credit for leak detection capability, as discussed in BTP HICB-19, along with the low probability of occurrence of a SWCMF to the Teleperm XS system concurrent with the LBLOCA event.
During the July 1, 2003, meeting, the NRC staff requested Duke to docket information provided during the meeting and provide additional information subsequent to the meeting.
The additional information was provided via phone conversations or electronic mail within two months of the meeting. The Attachment dockets the information previously provided.
By letter dated July 25, 2003, NRC stated that it intended to complete its review of Duke's March 20, 2003, submittal by September 30, 2003.
However, due to the RPS/ESPS modification deferral, Duke no longer needed the review completed by then and did not press the NRC to meet this date.
Duke has been frequently checking on the progress of this review and is aware that the only issue that needs to be resolved is Duke's request to eliminate the need to evaluate the LBLOCA in the D-in-D&D assessment.
Duke requests approval of the D-in-D&D assessment by October 31, 2004.
Duke has delayed design work associated with adding a diverse LPI actuation until after this date.
Therefore, approval by this date would allow Duke to avoid unnecessary design work.
The first digital RPS/ESPS replacement modification is scheduled for the Fall 2006 outage for Unit 1. Duke plans to submit the LAR for the digital RPS and ESPS upgrade by December, 2004.
If there are any additional questions, please contact Boyd Shingleton at (864) 885-4716.
Very truly yours,
/
4//4-t R. A. Jones, Vice President Oconee Nuclear Site
September 23, 2004 Page 3 cc:
Mr. L. N. Olshan, Project Manager Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-14 H25 Washington, D. C.
20555 Mr. W. D. Travers, Regional Administrator U. S. Nuclear Regulatory Commission -
Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. M. C. Shannon Senior Resident Inspector Oconee Nuclear Station Mr. Henry Porter, Director Division of Radioactive Waste Management Bureau of Land and Waste Management Department of Health & Environmental Control 2600 Bull Street Columbia, SC 29201
Attachment September 23, 2004 Page 1 Attachment Response to Request for Additional Information (RAI)
NRC RAI 1 -
The ratio of the critical crack size to the leakage crack size.
Duke Response - The ratio of the critical flaw size to the postulated initial flaw size for a 10 gpm leak are given below for the base metal and weld metal respectively.
These values are given for the location at the straight 28" ID cold leg pipe adjacent to the Reactor Vessel.
Base Metal:
2.2 Weld Metal:
4.0 These values can be obtained from the BAW 1847 Rev. 1 report page 4-12 (B&W Owners Group Leak-Before-Break Evaluation of Margins against Full Break for RCS Primary Piping in B&W-Designed NSS, September, 1985).
This information was provided by telephone conversation in July, 2003.
NRC RAI 2 - A clarification of the capability of the leakage detection systems and a docketed statement that 2 of the 3 systems meet Regulatory Guide 1.45, "Reactor Coolant Pressure Boundary Leakage Detection Systems."
Duke Response -
This information was docketed in Duke letter dated July 22, 2003, Attachment 1, Duke Response to RAI-13 starting on page 13.
NRC's evaluation of this information was provided in Section 3.3 (starting on page 10) of NRC Safety Evaluation dated September 29, 2003, related to Duke's request to apply Leak Before Break for the Low Pressure Injection (LPI) cross connect modification for Oconee Unit 1.
NRC RAI 3 -
A docketed statement that the times assumed for operator actions are calculated from the initiation of the event.
Duke Response -
The times assumed for operator actions in the Defense-in-Depth and Diversity (D-in-D & D) Assessment were calculated from the initiation of the event evaluated.
This information was provided verbally during the July 1, 2003, meeting.
Attachment September 23, 2004 Page 2 NRC RAI A discussion of the relevant differences between the Babcock and Wilcox Emergency Procedure Guidelines and the Oconee Emergency Operating Procedures.
The relevant differences between the Babcock and Wilcox Emergency Procedure Guidelines (referred to as Technical Basis Document below) and the Oconee Emergency Operating Procedures (referred to as EOPs below) are described below for those operator actions that have differences.
Manual Rx Trip within 2 minutes due to a SB LOCA The Technical Basis Document (TBD) and the EOP have tripping the Reactor as Step 1 of Immediate Manual Actions and have the same Entry Conditions.
In addition to the EOP, Oconee operators have memory items documented in Operations Management Procedures to manually trip the Reactor when RPS fails to do so, as well as, abnormal procedures that state to trip the Reactor due to excessive leakage.
Manually initiate High Pressure Injection (HPI) and LPI within 5 minutes during SB LOCA and Rod Ejection Accident Manually initiate Reactor Building Cooling System (RBCS) and Reactor Building Spray (RBS) within 8 minutes during SB LOCA and Rod Ejection Accident There are several differences in the Oconee's EOP and the Technical Basis Document (TBD) related to manually initiating ES.
The differences are mainly based on how we implement the EOP.
In the TBD, checking for ES actuation is in Step 11 of the Vital Systems Status Verification (VSSV) section. After Immediate Manual Actions, the VSSV section is performed. An equivalent step is located in the Oconee EOP at Step 9, however, ONS implements a routing technique called the "Parallel Action Page".
Once Immediate Manual Actions are performed, the "Parallel Action Page" is reviewed by the SRO with feedback from the RO's.
The SRO compares plant status and feedback from the RO's to the "Parallel Action Page".
Based on this, he has an RO initiate the ES Actuation Checklist which will initiate ES channels that have not actuated and should have (Steps 1 & 2 of the ES Actuation Checklist).
In parallel, when Subcooling Margin (SCM) is lost, one RO will perform Rule 2 (Loss of SCM) which will trip RCPs and initiate full HPI.
Performing the Loss of SCM rule (Rule 2) is the same as the TBD.