ML13238A054

Meeting Summary - Category 1 Public Meeting Regulatory Conference, H.B. Robinson Steam Electric Plant, Docket No. 50-261

ML13238A054
Person / Time
Site:	Robinson
Issue date:	08/23/2013
From:	Hopper G Division Reactor Projects II
To:	William Gideon Duke Energy Carolinas
References
EA-13-129
Download: ML13238A054 (56)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION REGION II 245 PEACHTREE CENTER AVENUE NE, SUITE 1200 ATLANTA, GEORGIA 30303-1257 August 23, 2013 EA-13-129 Mr. William R. Gideon Vice President Duke Energy H. B. Robinson Steam Electric Plant, Unit 2 3581 West Entrance Rd Hartsville, SC 29550

SUBJECT:

MEETING

SUMMARY

- CATEGORY 1 PUBLIC MEETING - REGULATORY CONFERENCE, H.B. ROBINSON STEAM ELECTRIC PLANT, DOCKET NO.

50-261

Dear MR. Gideon,

This refers to the meeting conducted at your request at the NRC Region II Office on August 19, 2013, at 10:30am, Eastern Time. The purpose of this Regulatory Conference was for you to present to the NRC your perspectives on the facts and assumptions used by the NRC to arrive at the finding and the significance stated in the Inspection Report (IR) 05000261/2013008. This meeting also provided you an opportunity to provide other information you believe the NRC should take into consideration before making an enforcement decision. Enclosed are a list of attendees (Enclosure 1) and the presentation handouts (Enclosure 2).

The topics discussed included Duke Energys position with regard to the preliminary White finding documented in IR 05000261/2013008. This preliminary White finding was associated with an apparent violation (AV) of 10 CFR 50.63, Loss of All Alternating Current Power, as a result of the licensees failure to inspect the dedicated shutdown diesel generator radiator fan belts in accordance with the vendors recommended maintenance guidelines. We will consider the information you provided prior to making an enforcement decision.

In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter and its enclosure will be available electronically for public inspection in the NRC Public Document Room (PDR) or from the Publicly Available Records (PARS) component of NRC's Agency-wide Document Access and Management System (ADAMS). ADAMS is accessible from the NRC Web site at http://www.nrc.gov/NRC/ADAMS/index.html (the Public Electronic Reading Room).

W. Gideon 2 Should you have any questions concerning this conference, please contact me at 404.997.4645.

Sincerely,

/RA By James Dodson For/

George Hopper, Chief Reactor Projects Branch 4 Division of Reactor Projects Docket No.: 50-261 License No.: DPR-23

Enclosures:

1. List of Attendee

2. Duke Energy Presentation Slides cc: Distribution via Listserv

___ML13238A054______ SUNSI REVIEW COMPLE FORM 665 ATTACHED OFFICE RII:DRP RII:DRP SIGNATURE /RA/ /RA/

NAME SHerrick JDodson DATE 8/20/2013 8/20/2013 E-MAIL COPY? YES NO YES NO YES NO YES NO YES NO YES NO YES NO W. Gideon 3 Letter to William R. Gideon from George Hopper dated August 23, 2013

SUBJECT:

MEETING

SUMMARY

- CATEGORY 1 PUBLIC MEETING - REGULATORY CONFERENCE, H.B. ROBINSON STEAM ELECTRIC PLANT, DOCKET NO.

50-261 DISTRIBUTION:

OEMAIL OEWEB Region II Regional Coordinator NRR Enforcement Coordinator Enforcement Officer and Regional Counsel, RII Public Affairs Officer, RII Chief, Resource Management Branch, RII Region II Administrator's Secretary DRP Division Secretary Region II Division Directors and Deputies Region II Receptionist Headquarters Operations Officer NRR DISP/PIPB (reactor cases)

L. Douglas, RII, EICS RIDSNRRDIRS RidsNrrPMRobinson Resource PUBLIC

List of Attendees NRC L. Wert, Deputy Regional Administrator, RII C. Evans, Regional Counsel, RII S. Sparks, Senior Enforcement Specialist, RII R. Croteau., Director, Division of Reactor Projects (DRP)

W. Jones, Deputy Director, DRP H. Christensen, Deputy Director, Division of Reactor Safety (DRS)

G. Hopper, Chief, DRP, Reactor Projects Branch (RPB) 4 C. Scott, Acting Senior Resident Inspector, Robinson, RII J. Hickey, Chief, Division of Fuel Facility Inspection, Fuel Facility Branch 2, RII J. Dodson, Senior Project Engineer, DRP, RPB 4 S. Herrick, Project Engineer, DRP, RPB 4 G. MacDonald, Senior Reactor Analyst, RII J. Circle, Senior Reliability and Risk Analyst, HQ Call-in attendees:

M. Halter, Office of Enforcement, HQ L. Casey, Office of Enforcement, HQ K. Ellis, Senior Resident Inspector, Robinson, RII DUKE / Robinson P. Gillespie, Senior Vice President Nuclear Operations R. Gideon, Site Vice President T. Cosgrove, Plant General Manager J. Kammer, Director, Engineering K. Holbrook, Manager, Operations D. Douglas, Manager, Maintenance B. Rishel, Manager, Probabilistic Risk Analysis J. McCrory, Senior Engineer, Probabilistic Risk Analysis R. Hightower, Supervisor, Licensing C. Nolan, Director, Corporate Regulatory Affairs Call-in attendee:

D. Cummings, Associate General Counsel Public (call-in)

R. Thomas S. Cownoley S. Threatt, State of SC T. McKinney, State of SC Enclosure 1

Robinson Nuclear Plant Dedicated Shutdown Diesel Fan Belt Performance Deficiency August 19, 2013 Regulatory Conference

Duke Participants

Preston Gillespie Senior Vice President, Nuclear Operations

Randy Gideon Site Vice President

Mike Glover Director, Site Operations

Tom Cosgrove Plant General Manager

Jim Kammer Director, Engineering

John Little Manager, Shift Operations

Donnie Douglas Manager, Maintenance

Bob Rishel Manager, Probabilistic Risk Analysis

Richard Hightower Supervisor, Licensing

Chris Nolan Director, Regulatory Affairs 2

Agenda

Opening Remarks R. Gideon

DSDG Design and Timeline J. Kammer

Operations Response J. Little

Maintenance Response D. Douglas

Significance Determination B. Rishel

Cause Analysis & Corrective Actions T. Cosgrove

Regulatory Perspective M. Glover

Closing Remarks P. Gillespie 3

Opening Remarks

Robinson agrees with the apparent violation described in the NRCs letter dated July 1, 2013

Robinson understands the importance of the Dedicated Shutdown Diesel-Generator (DSDG)

Performance did not meet our expectations for maintaining the DSDG

Root Cause Evaluation performed

Key drivers contained in the Probability Risk Assessment (PRA):

Mitigation measures to maintain secondary side cooling

High probability of success for fan belt replacement

Postulated damage from arc faulting in 480V cabinets

Duke Energys analysis concludes that the Finding is of very low safety significance 4

Dedicated Shutdown Diesel Generator Design and Timeline Jim Kammer Robinson Engineering Director 5

Robinson Design Topics

DSDG Design

Relevant Robinson Design Features

DSDG Belt Failure Timeline

Postulated Events affected by DSDG Belt Failure

Overall Postulated Event Timeline 6

DSDG Design

DSDG installed in 1981

The DSDG provides a source of electrical power to bring the plant safely to a hot shutdown condition in the event of a fire

DSDG automatically provides an emergency source of electrical power in the event of a simultaneous loss of all off-site power and both EDGs Fan Belt Guard 7

Design Features

Emergency AC Power

480V Emergency Power System versus more typical 4160V systems

Amptectors are installed on Emergency Bus E1 and E2 Supply Breakers

Spatial separation results in Emergency Bus E1 High Energy Arc Fault (HEAF) not directly impacting Emergency Bus E2 and vice versa

In the Cable Spread and Emergency Switchgear Rooms, fire retardant coating is applied to cables in tray that are not flame spread rated

Instrumentation

Instrumentation required for Operators to assess and maintain secondary side heat removal does not rely on power from Dedicated Shutdown (DS) Bus

Steam Driven Auxiliary Feedwater Pump flow indication does not rely on power from the DS Bus

Radio communications do not rely on power from the DS Bus 8

DSDG Belt Failure Timeline Started DSDG Closed DSDG DSDG unloaded breaker automatic successfully from the 52/32B and shutdown on tested per DSDG loaded the high OST-910 enclosure per DSDG temperature monthly OST-910 Aug 28 Oct 2 Oct 2 Oct 2 1808 1623 1648 1703 9

Postulated Fire Events Affected by DSDG Belt Failure

Postulated large fire affecting onsite power distribution

Dominates both Duke and NRC Risk Significance Analysis

Postulated loss of Offsite and Emergency AC power internal to power block only

Support facilities would continue to receive AC power from retail distribution system 10

Postulated Fire Event Timeline 0 Minutes 78 Minutes 150 Minutes 255 Minutes Core Inventory Makeup Operations Event Initiation Required Recovery Normal DS Indications DS Battery Depleted Maintenance Repair of DSDG Radiator Fan Belt 11

Operations Response John Little Robinson Manager - Shift Operations 12

Operations Response - Overview

Operators would maintain adequate heat sink capability for core decay heat removal

Procedural Direction

Training

Periodic Examinations

Operator Fundamentals

Operators would respond to the fire using AOP-041, Response to a Fire Event and DSP-001, Alternate Shutdown Diagnostic

Based on postulated fire location or procedural progression, both emergency buses and offsite power are assumed to be unavailable 13

Operations Response - Overview

Depending on the limiting event, Operators would respond with

DSP-002, Dedicated Shutdown Procedure - Hot Shutdown Using the Dedicated/Alternate Shutdown System

EPP-1, End Path Procedure - Loss of All AC Power

For the purposes of this discussion, DSP-002 response is more limiting

Cooldown rate

DSP-002 - 25°F/hr

EPP 100°F/hr

DSP-002 exposes RCP seals to elevated temperature for a longer period of time

Other factors

Requires control of the plant from local control stations

Communications and direction via radio 14

Operations Response - Procedural Requirements

Operators will maintain Auxiliary Feedwater flow ensuring the critical safety function for heat sink - 300 gpm Auxiliary Feedwater (AFW) flow or minimum of 8% SG narrow range (60% wide range) level

Procedure steps direct maintaining heat sink early in response:

EOP-E-0, Reactor Trip or Safety Injection, steps 6 through 8 (prior to entry into DSP-002)

EPP-1, step 7

DSP-002, Attachment 1, Turbine Building Operator, steps 6 and 7 15

Operations Response - Anticipating Plant Response

Stable cooldown rate with valve position procedurally established via DSP-002 prior to DS battery depletion

DSP-002 implements DSP-007, Cold Shutdown Using DS System

DS Battery Depletion occurs in One Hour

Included in procedural basis in multiple procedures

EOP-E-0

OP-602, Dedicated Shutdown System

Operators would expect effects of depletion of DS battery after trip of the DSDG and would have one hour to prepare

Based on related procedures

Feedwater flow will continue for heat sink 16

Operations Response - Reinforced by Training

Dedicated Shutdown (DS) Procedural Strategy included as part of Operator Initial Training Curriculum

Continuing Training Backbone

Prior to DSDG Belt Failure

DSP-002, last completed August 2011

EPP-1, last completed June 2012 17

Operations Response - Reinforced by Training

Importance of DS strategy including DSDG reflected by frequency they appear in Licensed Operator Job Performance Measure (JPM) annual exams:

2009 - Local SG PORV control

2009 - Energizing DS Bus using DSDG per DSP-002

2010 - Deenergizing Emergency Buses per DSP-002

2010 - Manual Start of the DSDG per EPP-1

2012 - Manual Start of DSDG per DSP-002 (after AUTO start mod)

2012 - Respond to a loss of all AC Power EPP-1 (AFW Flow)

2013 - Start CCW Pump A, Control Charging Pump A locally per DSP-002 18

DSP-002, Alternate Hot Shutdown System Procedure

Operations personnel proceed to the pre-arranged muster location 19

DSP-002, Alternate Hot Shutdown System Procedure

Radios, portable lights and controlled procedures maintained in the muster location

Radio communication between operators has been demonstrated

Channel 2 does not require use of repeater

Successfully Tested at NRC request - 2007 Triennial Fire Protection Inspection (IP 71111.05); from Muster Location to Charging pump room on channel 2 without need for repeater (11/07/07)

Functionality tested monthly per OST-639, Fire Equipment Inventory

Test successfully repeated on 08/07/13:

Muster location to Secondary Control Panel, Charging Pump Room, and SI Pump Room

If Shift Manager goes to Work Control, communicates to Charging Pump Room via Secondary Control Panel Operator 20

Secondary Control Station

Operators control the plant at the secondary control station

Location where cooldown established

Natural circulation including subcooling checked at step 10 of DSP-002, Att. 1 21

AFW Flow Control Valves

Operators control AFW flow using valves adjacent to the control panel to maintain the secondary heat sink

A stable cooldown rate with associated valve position via DSP-002 would have been attained by the time of DS battery depletion 22

Indications Used for Control

Secondary Control Station - Multiple indications available at the start of the postulated scenario and for one hour on the DS batteries after DSDG trip

SG Level (all three SGs)

Pressurizer (PZR) Level

Pressurizer Pressure

Condensate Storage Tank Level

A RCS Cold Leg Temperature

A RCS Hot Leg Temperature

Indications remaining after battery depletion

AFW flow via FT-6416 - 1st level Turbine Building

SG Pressure - Secondary Control Station 23

Secondary Control Station Operators use the indication of SG pressure (left) and the curve from DSP-002 (right) to correlate and control RCS cold leg temperature and ensure decay heat removal

Indications of pressure for all three steam generators would remain available

purely mechanical, no electrical power necessary

SG level indication not necessary FT-6416 - Local Feed Flow indication, first level turbine building (center), remains available, electrical power not required 24

Response to DSDG High Temperature Trip

Operators will maintain feedwater flow ensuring critical safety function of heat sink for decay heat removal

AFW flow procedurally driven to 300 gpm minimum

SG levels procedurally established and maintained between 60 and 68%

Stable cooldown rate of 25°F/hour after entry into DSP-002

Operator have the procedures, training, indications, and fundamental knowledge to successfully maintain decay heat removal

Performance of DSP-002 provides a success path

Flow rates to the SG are relatively stable when DS Battery is depleted

Vapor volume of SGs sufficient to prevent overfill after loss of level indication

SG Overfill will not occur in the postulated scenario 25

Operations Success Credit

Operator actions will succeed

Procedures direct continued flow to the steam generators

Available indications will be used to ensure SGs remain viable as a heat sink throughout the postulated scenario

Operator actions to maintain flow have been in progress prior to the loss of SG indication and will continue after the loss

Required only to continue feed flow and steaming monitoring SG pressure

Training and examinations reinforce continued flow to the steam generators

Effective Radio communications demonstrated 26

Maintenance Response Donnie Douglas Robinson Maintenance Manager 27

Maintenance Response

Personnel will respond to the ERO notification

Parts needed to repair the DSDG are readily obtained with or without computer resources or other support

Emergent Work Order using station process is designed for this type of situation

DSDG repair will succeed in required timeframe

Straightforward tasks

Simple, readily available tools 28

Maintenance Response Strategy to Postulated Fire Event 0 Minutes 18 Minutes 30 Minutes 60 Minutes 120 Minutes 150 Minutes Start of Belt Installation Core Inventory Makeup Team 1 Event Initiation ERO Notification Remove Guard Combined Team Personnel Arriving Travel to Site DSDG Trip Install Belts Team 2 Obtain Belts Operations Diagnosis of Trip 29

Maintenance Response Maintenance actions start to recover DSDG:

Within 60 minutes of the start of the scenario:

Maintenance personnel arrive on site

Missions to locate replacement belts and remove belt guard underway 30

Maintenance Response Within 120 minutes of the start of the scenario, Maintenance have obtained the replacement belts 31

Maintenance Response Within 120 minutes of the start of the scenario, Maintenance would have the guard off and the belts removed 32

Maintenance Success Credit

High Probability of Success

Emergency Response to fill two teams

Identifying/Acquiring Parts

core skill

trial scenarios

day and night acquisition

Emergent Work Order process practiced in Emergency drills/exercises

Belt replacement is a simple and frequent task

181 Work Order tasks performed over past 5 years associated with belt replacements or adjustments with one condition report for rework 33

Significance Determination Bob Rishel PRA Manager 34

Significance Determination - Overview

Robinson Basis for Very Low Safety Significance

1. Plant design and configuration of DS cables/HEAF sources make loss of DS Bus unlikely

Impact of 480V HEAF is smaller when compared to a 4160V HEAF

2. Recovery Credit

Operators establish/maintain SGs feed and cool down rates before DS battery depletion occurs

Operators maintain heat sink after DS battery depletion

Maintenance recovery of DSDG

The belt repair straightforward with simple tools 35

HEAFs in Robinson E1 Switchgear

Robinson 480V HEAF considerations

1. 480V E1 and E2 switchgear robust cabinet construction

Solid tops

Cabinets are secured with thread fasteners in corners

Supply breakers are in lower half of cabinet

Outgoing load breakers are protected with Amptectors

2. E2 cables and DS Bus cables are outside the Zone of Influence (ZOI) for E1 HEAF from supply breakers

3. No E2 damage from E1 HEAF

No loss of DS Bus due to E1 HEAF 36

Emergency Bus Configuration - Looking South Emergency Emergency Bus E1 Bus E2 37

Significance Determination Contributions

Robinson Incremental Conditional Core damage Probability (ICCDP) contribution from the E1 HEAF is <1E-08

This is based on:

E1 Switchgear energetic phase HEAF zone of influence does not cause a loss of DS Bus power or E2 Bus

Per NUREG/CR-6850 Appendix M and FAQ 06-0017, 480V HEAFs have not caused damage beyond the switchgear itself

FAQ 06-0017 limits 480V HEAFs to feeder breakers

The 480V HEAF ZOI is smaller than the NUREG/CR-6850 Appendix M for medium voltage switchgear 38

Significance Determination Recovery Credit

Full recovery credit (defined as 92.5%) should be applied

DSP-002 establishes initial success for SG feed with SDAFW

Maintaining feed leads to success

No diagnosis required by the operator

Stress - high

Complexity - nominal

Training - nominal

Procedures - available

Indications - available

Expansive time is available

Tech Support Center provides oversight

Fan Belt replacement is straightforward

Robinson ICCDP evaluation is approximately 6.5E-07 39

Causes and Corrective Actions Tom Cosgrove Robinson Plant Manager 40

Evaluation Results: Causes

Root Cause - A time based preventative maintenance basis prescribing fan belt replacement did not exist

Primary Contributing Causes

Belt Procedure steps not prescriptive

Degraded motor sheave condition

Contributing Causes

Did not exhibit the behaviors needed to achieve high standards of reliability and availability of the DSDG

Belt guard design precluded routine monitoring

Lack of maintenance rigor in use of vendor information (used qualitative vice quantitative inspection techniques) 41

Corrective Actions: Immediate / Interim

Immediate Actions Taken

Replaced the radiator fan belts

Modified the radiator fan belt guard

Interim Actions Taken

Implemented additional short term motor, fan and belt monitoring actions

Conducted leadership and maintenance briefs

Completed system expectation sessions with maintenance, engineering, work management, operations and station leadership 42

Corrective Actions: To Address Causes

Corrective Actions to Preclude Recurrence

Implemented a time based DSDG belt replacement frequency of 2 years

Other Key Corrective Actions to Address Causes

Replaced sheaves and modified the DSDG fan motor mounting

Revised maintenance procedures to include quantitative sheave exam, belt inspection, and tensioning criteria (Programmatic)

Integrated DSDG into the stations Reliability Improvement Plan (Organizational)

Conduct Training for Performance Improvement (Includes Continuing and Initial Training) 43

Corrective Actions: Extent of Condition

Emergency Diesel Generators (EDGs) A&B supply/exhaust fan belts replaced

Preventive Maintenance (PM) for EDGs supply/exhaust fan time based replacement

PM for time based replacement - Engine Driven Fire Pump/alternator

Security DG radiator fan and alternator drive belts replaced

PM for replacement of Instrument Air compressors A/B drive belts on 4 year frequency 44

Corrective Actions: Extent of Cause

Identify new PMs for belts

Flex equipment

4th Train AFW DG

Deep Well DG

Identify new PMs for elastomerics

AFW

Service Water

Fire Protection

CVCS

Expand scope of systems if 4 or more new PMs are needed

Single Failure study - DSDG and support systems 45

New Sheaves and Mounting System for DSDG Radiator Fan 46

Radiator Fan Belt Guard with New View Port View Port 47

Regulatory Perspectives Mike Glover Director - Site Operations 48

Regulatory Perspectives

Apparent violation of 10 CFR 50.63 (Blackout Rule) for failure to perform adequate preventative maintenance on the Dedicated shutdown Diesel Generator (DSDG) cooling system.

Robinson agrees with the Apparent Violation from the aspect that no time based replacement activity was in place for the DSDG radiator fan belts

Corrective Actions to restore compliance were completed on October 3, 2012

Comprehensive actions have been taken to prevent recurrence

Other corrective actions are taken or planned

In summary, despite the temporary loss of the DSDG, the combination of the above along with the other actions described in this presentation serve to ensure mitigation necessary to prevent core damage

Duke Energys analysis concludes that the Finding is of very low safety significance 49

Closing Remarks Preston Gillespie Senior Vice President, Nuclear Operations 50

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