ML061390034
| ML061390034 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 05/16/2006 |
| From: | Exelon Nuclear |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML061390034 (15) | |
Text
Nuclear Bwron Unit l and Braidwood Unit 2 Request for Deferment of Downstream Effects Related Modifications May 16,2006 Page 1
Exelon Attendees Bruce Rash - Corporate Engineering Design Director Brian Davenport - Corporate Engineering John Panici Braidwood Design Engineering Joseph Bauer - Corporate Licensing Douglas Walker Corporate Licensing Dan Brush - Project Manager Ivo Garza - Sargent and Lundy Presenter: Brian Davenport Corporate Engineering Page 2
AGENDA
> Request for Deferment of Downstream Effects related plant changes until Spring 2008 for Bryron Unit 1 and Braidwood Unit 2, only.
) Summarize GSI-1 91 Analyses & Testing
> Plant Change Implementation Plans
> Downstream Effects Analyses Performed
> Downstream Effects Plant Changes Needed
> NRC Decision Requested Page 3
GSI -191 Resolution Schedule Full Scope:
> Byron Unit 2 (Spring 2007)
) Braidwood Unit 1 (Fall 2007)
Sump Screen ReplacementlDefer Downstream only:
) Byron Unit 1 (Fall 2006)
- Braidwood Unit 2 (Fall 2006)
Replacing all Sump Scre ens prior 12/31/07 in accordance w-lith GL schedule.
Page 4
Decision R e quest
> Approval to Defer Downstream Effects related plant changes until Spring 2008 Refueling Outages, for Byron Unit 1 and Braidwood Unit 2, only,
) Work Scope to be Deferred
> ECCS Throttle Valve / Orifice Work
> CS Pump Cyclone Separator Removal / Modification
> Proposed Schedule
> Byron Unit 1 Spring 2008 Refueling Outage
> Braidwood Unit 2 -
Spring 2008 Refueling Outage Page 5
ANALYSIS STATUS:
Analysis/testing performed to ensure adequate NPSH for ECCS Pumps
) NEI 02-01 Walkdowns (all 4 units complete)
I Debris Generation Analysis performed
- Containment Transport Analysis performed
> Includes Computational Fluid Dynamics (CFD) model H
Head Loss Analysis (per GR/SER) performed
) Vendors Strainer, Head Loss Testing performed (wlo chemical effects)
> Bypass testing performed
> Downstream Effects analysis performed (per WCAP 16406-P)
) Scheduled testing
> Chemical Effects Testing (completion June 2006)
- Supplemental head loss testing (completion June 2006)
Performing analyses in accordance with recommended NEI and GRISER Guidelines Page 6
Plant Change Implementation
) Install new replacement sump strainers in each sump (2 sumps per unit)
> New strainer size approximately 3000 sq.fti/sump; current total strainer area - 150 sq.ft.
> New screen mesh size will be smaller than current (1/1 2" versus 3/16" currently)
> Remove fiberglass insulation on mid-section of steam generators & connecting piping within ZOI, replace with Reflective Metal Insulation (RMI) (Unit 1 at each plant)
> Alleviates fiber debris load at sump screen
> Unit 2 at each plant is virtually all RMI insulation
> Install trash racks for debris interception
> Upstream of new sump screens Minimizing fiber, debris load mainly RMI, Coatings, and Latent debris.
Installing maximum strainer area that fits inside plant sumps.
Page 7
At.creen.nstallation i~~~Pg le Nl m
Screen Installation
- w
- . :.k I
I I
Downstream Effects Analysis
> Analysis performed based on WCAP 1 6406-P
> Equipment Evaluated for wear and plugging
> Residual Heat Removal (RHR) Pumps and Heat Exchangers
> Safety Injection (SI) Pumps
> Charging I Safety Injection (CV) Pumps
> Containment Spray (CS) Pumps, Spray Eductors and Nozzles
> Flow Orifii (restricting and flow element)
> Throttle Valves
> Instrumentation
> Piston Check Valves
- Relief Valves
> Reactor fuel and vessel internals l component wear is minimal for 30 day mission time. l Page 1 0
Downstream Effects Plant Change Implementation
> Identified two plant changes due to possible plugging issues
> ECCS Throttle valves (8/Unit)
> Replacement of trim and some pressure retaining parts on 8 valves/unit and downstream orifii
> CS Pump Cyclone Separator removal from the seal purge line
> Flowserve preliminary solution replaces separator with a pressure breakdown device.
Changes to ECCS throttle valves needed; removal of cyclone separator preliminary scope determined with pump seal vendor.
Page 1 1
Downstream Effects Challenges GSl-1 91 Full Scope Schedule I
GSHl91 Full Scope ScheduleI Full evaluation and shop testing needed to confirm acceptable impact on ECOS systems. Insufficient time to ensure proper requirements are met.
Safet Impact o Margin Improvements
> Removing fibrous insulation from ZOI areas and replacing with RMI
<(Unit 1 at both Byron & Braidwood )
> New Strainers Size Approximately 3000 sq.ft./sump; 2 sumps/unit; current strainer area - 150 sq.ft.
> New screen mesh size will be smaller than current (1/12" versus 3/1 6' currently)
> Adding trash racks upstream of new sump screens for large debris interception
> Mitigating Factors (Bulletin 2003-01 measures)
> Existing FME controls
) Improvements to the loose debris surveillances
> EOP changes to speed up cooldown in the event of a Small Break (SB) LOCA Planned Improvements increase margni and lower risk.
Page 13
Safet Impact
> RSik Perspective
> Short duration (12/31/07 - Spring 2008) from Generic Letter required implementation schedule
> Large Break LOCA generates/transports max. debris to sumps
> S1 and CV are only really needed for smaller LOCA's
> Sensitivity study of potential flow blockage indicates that 50% flow reduction of Si cold leg injection still provides adequate core cooling.
> Qualitative Risk assessment indicates a small incremental increase in risk.
> Cyclone separator concern much less likely due to reduction of fibrous insulation in ZOI inside containment o Not likely to significantly impact CS Pump operation.
I Additional 4 months results in very small incremental risk increase l
Page 14
Closing Remarks
) Bruce Rash-Exelon Corporate Engineering Design Director
> Approval to Delay Downstream Effects related plant changes until Spring 2008 Refueling Outages for Byron Unit 1 and Braidwood Unit 2, only,
> Work Scope to be Deferred
> ECCS Throttle Valve / Orifice Work
> CS Pump Cyclone Separator Removal / Modification D Proposed Schedule
> Byron Unit 1 Spring 2008 Refueling Outage
> Braidwood Unit 2 -
Spring 2008 Refueling Outage Page 15