ML11279A252
| ML11279A252 | |
| 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: ML11279A252 (6) | |
Text
Turbine Building HELB Event Overview Notes All units operating @ 100% prior to event HELB committed plant modifications installed Detailed flow charts provided on pages 2 - 4 Event timeline provided on page 5 Acronym definitions provided on page 6 HELB occurs in Turbine Building resulting in unit blackout(s) with failure of TDEFDWP.
(Assumed worst case scenario)
Maintain unit(s) stable in HSB from MCR with HPI/
PSW Maintain unit(s) stable in HSB from SSF Perform assessment/repair of failed HPI/PSW 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 to HPI/PSW Perform natural circ cool down to 250 deg F and secure HPI (long term safe and stable condition)
Perform assessment/repair of LPI DHR components Transition to LPI DHR Duke Energy / NRC Pre-submittal Meeting 1
HELB occurs in Turbine Building resulting in unit blackout(s) with failure of TDEFDWP.
(Assumed worst case scenario)
Affected unit(s) trip:
CR SROs enter EOP ROs perform IMAs and Symptoms Check and determine loss of RCP seal cooling and/or loss of SG DHR CR SRO directs a LO to perform AP/25, SSF EOP LO proceeds to SSF.
CR SRO directs OATC to perform EOP enclosure to align PSW power to HPI and PSW pumps 1 CR SRO directs OATC to perform EOP enclosure to re-establish RCP seal cooling with HPI and SG DHR with PSW pump 1 Page 3 A HELB in the Turbine Building will not affect PSW or SSF Turbine Building HELB Event Details 1 PSW modification related procedure revision currently in development.
Duke Energy / NRC Pre-submittal Meeting 2
Control Room Actions Natural circulation hot standby (HSB) conditions are established from the SSF:
LO transfers control to SSF LO powers SSF from SSF D/G LO starts SSF ASW pump LO establishes RCP seal cooling via RCMU pump for each affected unit.
LO establishes SG feed via SSF ASW pump for each affected unit.
LO cycles PZR heaters to control RC pressure SPOC deploys SSF submersible pump in intake canal SSF Actions Natural circulation hot standby (HSB) conditions are established from the main control room:
OATC verifies offsite power available to PSW building or aligns power from Keowee hydro if necessary 1 OATC starts the PSW booster pump and primary pump 1 OATC establishes SG feed via PSW pump 1 OATC transfers credited HPI components to PSW power 1 OATC establishes RCP seal cooling via PSW powered HPI 1 PSW power is locally aligned to PZR heaters 1 PZR heaters maintain RC pressure 1 SPOC deploys SSF submersible pump in intake canal 2 Page 2 Page 4 Page 4 If PSW/HPI is successful, OATC directs LO to terminate AP/25 1 Turbine Building HELB Event Details Single failure criteria 2 HELB related procedure revision not yet in development.
1 PSW modification related procedure revision currently in development.
Duke Energy / NRC Pre-submittal Meeting 3
At direction of TSC an assessment and repair of nonfunctioning HPI /
PSW components is performed 1 Page 3 Page 3 Upon completion of assessment and repairs operating crew transitions RCP seal cooling and/or SG DHR functions from SSF to main control room 1 Operating crew initiates plant cool down per Blackout tab of EOP 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 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 Affected units are prepared for natural circulation cool down from main control room:
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 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 PSW power aligned to SSF and SSF D/G is secured Portable valve control panel installed and connected to CFT isolation valves per RP/
1000/022 Turbine Building HELB Event Details Long term DHR provided by SGs being fed with PSW 1 1 HELB related procedure revision not yet in development.
Duke Energy / NRC Pre-submittal Meeting 4
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 back to HPI/PSW completed T=72 hrs, Transition from hot standby to hot shutdown initiated
- Previously established SSF activation times Event Timeline Duke Energy / NRC Pre-submittal Meeting 5
Acronyms 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 E Plan - Emergency Plan EOP - Emergency Operating Procedure HELB - High Energy Line Break HPI - High Pressure Injection System HSB - Hot Standby IMAs - Immediate Manual Actions LO - Licensed RO or SRO LPI - Low Pressure Injection System MCR - Main Control Room OATC - Operator At The Controls Reactor Operator OSM - Operations Shift Manager PORV - Power Operated Relief Valve PSW - Protected Service Water System PZR - Pressurizer RC - Reactor Coolant RCMU - Reactor Coolant Make Up System RCP - Reactor Coolant Pump RO - Reactor Operator RP - Response Procedure SG - Steam Generator SPOC - Maintenance Single Point of Contact SFP - Spent Fuel Pool SRO - Senior Reactor Operator SSF - Standby Shutdown Facility TDEFDWP - Turbine Driven Emergency Feedwater Pump TSC - Technical Support Center Duke Energy / NRC Pre-submittal Meeting 6