ML11279A253
| ML11279A253 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 10/06/2011 |
| From: | Duke Energy Carolinas |
| To: | Office of Nuclear Reactor Regulation |
| Stang J | |
| Shared Package | |
| ML11279A250 | List: |
| References | |
| Download: ML11279A253 (7) | |
Text
Tornado strikes site resulting in three unit blackout with loss of TDEFDWP (Assumed worst case scenario)
Maintain unit(s) at HSB from SSF for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Perform assessment and repair of HPI components within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Transition from SSF RCMU to HPI and perform natural circ cool down to 250 deg. F Secure HPI and maintain unit(s) at 250 deg. F with SSF ASW (long term safe and stable condition)
Tornado Event Overview Notes All units operating @ 100% prior to event Tornado committed plant modifications installed Detailed flow charts provided on pages 2 - 5 Event timeline provided on page 6 Acronym definitions provided on page 7 Duke Energy / NRC Pre-submittal Meeting 1
Tornado Watch Declared Crew enters AP/06:
Makes PA Announcement Notifies Security and Keowee Hydro Station OSM evaluates need to preemptively staff SSF Tornado Warning Declared Yes No Crew Goes To Severe Weather Enclosure Crew Goes To Tornado Warning
Enclosure:
Dispatch one Unit 1 or Unit 2 LO to SSF to establish communication with Control Room All Ops personnel report to control room Prep for tornado Tornado strikes site resulting in three unit blackout with loss of TDEFDWP (Assumed worst case scenario)
All three units trip:
CR SROs enter EOP ROs perform IMAs and Symptoms Check and determine loss of function LO at SSF is directed to perform AP/25, SSF EOP LOs from other two affected units proceed to SSF Page 3 Tornado Event Details Duke Energy / NRC Pre-submittal Meeting 2
Control Room Actions Natural circulation hot standby (HSB) conditions are established from the SSF:
LO at SSF transfers control to SSF LO at SSF powers SSF from SSF D/G LO at SSF starts SSF ASW pump LO at SSF establishes RCP seal cooling via RCMU pump for one unit 1 LO at SSF aligns SSF ASW for each affected unit 1 LO at SSF establishes SG feed via SSF ASW pump for one unit Additional LOs arrive and establish SG feed via SSF ASW and RCP seal cooling via RCMU pump 1 LO for each unit stabilizes unit in natural circulation hot standby (HSB) conditions SPOC deploys SSF submersible pump in intake canal SSF Actions Assessment and recovery actions are initiated:
CR SRO transfers to the Blackout tab of the EOP.
CR SRO and OATC attempt to restore power OSM enters E Plan and TSC is activated TSC initiates RP/1000/022 to coordinate assessment
& repair activities 1 CR SRO enters AP/
1700/035, Loss of SFP Cooling If required, TSC arranges for local fire department to provide pumper truck to replenish SFP inventory per RP/1000/022 Page 2 Page 4 Page 4 Tornado Event Details 1 Tornado procedure revision not yet in development.
Duke Energy / NRC Pre-submittal Meeting 3
At direction of TSC, OP/1102/024, Plant Damage Assessment, is performed to verify the availability of systems/components needed to transition to hot shutdown conditions 1:
13.8KV line from PSW substation to PSW building is restored 4KV power is restored to PSW booster pump and pump configured for local starting 4KV power is restored to credited HPI pump and pump configured for local starting Damaged A & B HPI discharge header piping is repaired or isolated, as necessary Damaged RCP seal injection piping repaired as necessary.
Portable valve control panel installed and connected to RV head vents, PORV and CFT isolation valves PSW power aligned to SSF and SSF D/G is secured Damage assessment/repair completed 72 hrs Page 3 Page 3 Page 5 Page 5 Tornado Event Details 1 Tornado procedure revision not yet in development.
Duke Energy / NRC Pre-submittal Meeting 4
Operating crew initiates plant cool down per OP/1102/025 1:
Reactor vessel head vents are opened Crew initiates RC cool down by throttling open ADVs Crew initiates RC de-pressurization via PORV At 800 psig, core flood tanks are isolated Unit is stabilized in natural circulation hot shutdown conditions (250°F/300 psig)
Reactor vessel head vents are closed HPI system is secured Upon completion of assessment and repairs operating crew transitions HPI functions from SSF to local control per OP/1102/025 1:
HPI pump cooling provided by PSW booster pump RCP seal cooling/makeup provided by HPI system and SSF RCMU system is secured SG feed provided by SSF ASW system SSF powered from PSW Page 4 Page 4 Tornado Event Details Long term DHR provided by SGs being fed with SSF ASW 1 1 Tornado procedure revision not yet in development.
Assessment/repair of LPI DHR components performed per OP/1102/024 and RP/1000/022 1 Transition to LPI DHR per OP/1102/025 1 Duke Energy / NRC Pre-submittal Meeting 5
T=0, Event Initiation (Loss of Function)
T=14 min, SSF ASW flow established to SGs*
T=20 min, SSF RCMU flow established*
T=75 min, TSC activated T=1.75 hrs, Diversion of SSF D/G service water flow to yard initiated*
T=2.00 hrs, Diversion of SSF D/G service water flow to yard completed*
T=3hr 20 min, SSF submersible pump deployed*
T=36 hours, Maximum time to initiate replenishment of SFP T=72 hrs, Assessment/repairs needed to transition to hot shutdown completed.
T=72 hrs, Transition from hot standby to hot shutdown initiated.
- Previously established SSF activation time Event Timeline Duke Energy / NRC Pre-submittal Meeting 6
ADV - Atmospheric Dump Valve AP - Abnormal Procedure ASW - Auxiliary Service Water System CFT - Core Flood Tank CR SRO - Control Room SRO/Procedure Director D/G - Diesel Generator DHR - Decay Heat removal EOP - Emergency Operating Procedure E Plan - Emergency Plan HPI - High Pressure Injection System HSB - Hot Standby IMAs - Immediate Manual Actions LO - Licensed RO or SRO LPI - Low Pressure Injection System OATC - Operator At The Controls Reactor Operator OPS - Operations Department OSM - Operations Shift Manager PA - Public Address PORV - Power Operated Relief Valve PSW - Protected Service Water System RC - Reactor Coolant RCMU - Reactor Coolant Make Up System RCP - Reactor Coolant Pump RO - Reactor Operator RP - Response Procedure RV - Reactor Vessel SG - Steam Generator SPOC - Maintenance Single Point of Contact SRO - Senior Reactor Operator SSF - Standby Shutdown Facility TDEFDWP - Turbine Driven Emergency Feedwater Pump TSC - Technical Support Center Acronyms Duke Energy / NRC Pre-submittal Meeting 7