Attarian: NRC Fukushima Response

George Attarian
Fukushima Response
• Timeline:
• March 11: Event occurred
• March 18: INPO IER 11-1 issued (April 15)
• March 23: NRC TI 2515/183 issued (May 13)
• April 25: INPO IER 11-2 issued (September 20)
• April 19: NRC TI 2515/184 issued (June 30)
• May 11: NRC Bulletin 2011-01 issued (July 11)
• June 8:
NEI The Way Forward issued
• July 12: NRC NTTF issued
• August 1: INPO IER 11-4 issued (January 28)
• August 1: INPO Equipment Survey issued (November 4)
Fukushima Response
• Timeline
• September 1: INPO IER 11-1 Supplement issued (March)
• September 9: NRC SECY-11-0124 issued, SRM issued
October 18
October 3:
NRC SECY-11-0137 issued, SRM issued
November 8
December 14: NRC holds first public, issue specific meetings on
January 18-19:NRC holds second public issue specific meetings
and presents draft 50.54(f) letter with enclosures
March 9:
50.54(f) letter and enclosures and Orders issued to
the Licensee for Tier I NTTF’s
Fukushima Response
• NRC Near Term Task Force (NTTF) Recommendations (12)
• Clarifying The Regulatory Framework (1)
• Ensuring Protection (2)
• Enhancing Mitigation (5)
• Strengthening Emergency Preparedness (3)
• Improving the Efficiency of NRC Programs (1)
Fukushima Response
• NTTF Impact
• NTTF 2.1 Flood and Seismic
• 50.54(f) letter to licensee
• New flood analysis beyond design basis
• Seismic currently following GI 199
• NTTF 2.3 Walkdowns
• 50.54(f) letter to licensee
• Walk down the site for all external design basis events: flood; seismic, other
external events
• NTTF 4.1 SBO
• Rule making
Fukushima Response
• NTTF Impact
• NTTF 4.2
• By order
• Additional pumps and related equipment
• FLEX approach
• NTTF 5.1 Harden Vents
• By order
• BWR Mark I & II only
• Filtration system not in order
• NTTF 7.1 Spent Fuel Pool Instrumentation
• By order
• Level only
• Primary and backup
• Control Room or Alternate Shutdown monitoring
• Qualifications
Fukushima Response
• NTTF Impact
• NTTF 8 EDMG EOP SAMG integration
• Rule making
• NTTF 9.3 Emergency Preparedness Staffing
• 50.54(f) letter to licensee
• Extension of the EP Rule
• Staffing impact to multiple Unit plant sites
• Communication guidance
Station Blackout Definition
• 10CFR50.2 Definition
• The complete loss of alternating current (ac) electric
power to the essential and nonessential switchgear buses
in a nuclear power plant.
• Station blackout does not include the loss of available
buses fed by station batteries through inverters or by
alternate ac sources as defined, nor does it assume a
concurrent single failure or design basis accident.
Alternate AC Sources
• An alternating current (ac) power source that is available
to and located at or nearby a nuclear power plant and
meets the following requirements:
• Is connectable to but not normally connected to the offsite or onsite
emergency ac power systems;
• Has minimum potential for common mode failure with offsite power
or the onsite emergency ac power sources;
• Is available in a timely manner after the onset of station blackout;
• Has sufficient capacity and reliability for operation of all systems
required for coping with station blackout and for the time required to
bring and maintain the plant in safe shutdown (non-design basis
Current NRC Rule
• 10CFR 50.63 Loss of all alternating current power
• (a) Requirements. (1) Each light-water-cooled nuclear power plant
licensed to operate must be able to withstand for a specified duration
and recover from a station blackout as defined in § 50.2. The
specified station blackout duration shall be based on the following
• (i) The redundancy of the onsite emergency ac power sources;
• (ii) The reliability of the onsite emergency ac power sources;
• (iii) The expected frequency of loss of offsite power; and
• (iv) The probable time needed to restore offsite power.
Current NRC Rule (cont’d)
• (2) The reactor core and associated coolant, control, and
protection systems, including station batteries and any
other necessary support systems, must provide sufficient
capacity and capability to ensure that the core is cooled
and appropriate containment integrity is maintained in the
event of a station blackout for the specified duration.
• The capability for coping with a station blackout of
specified duration shall be determined by an appropriate
coping analysis. Licensees are expected to have the
baseline assumptions, analyses, and related information
used in their coping evaluations available for NRC review.
Regulatory Guide 1.155
• Reg. Guide 1.155, Station Blackout
• Specifies a method acceptable to the NRC staff for
complying with 10CFR50.63
Twenty four pages of detailed guidance
EDG Target Reliability Levels
Restoration of Offsite Power
Ability to Cope with a Station Blackout
Quality Assurance Guidance for Non-Safety Systems and
NUMARC 87-00
• Guidelines and Methodologies for Implementing the
Nuclear Management an Resources Council (NUMARC)
Station Blackout Initiatives
• Three Hundred Pages of Detailed Guidance, Examples,
Topical Reports, and Questions & Answers
• Endorsed by Reg. Guide 1.155 as Acceptable Guidance
for Compliance to 10CFR50.63
• Contains Detail Beyond Reg. Guide 1.155
Typical Results
• Plant Specific SBO Coping Analyses Produced
• Specifies How Long You Have to Cope Without AC Power
• Typically 4 or 8 hours
• Specifies How Coping is Achieved
• Batteries, alternate ac power, RCS leak rates, water sources,
pumps, instrumentation & control, etc.
• Requires Containment Isolation
• Typically Addresses Pre- Hurricane Preparations for
Coastal Plants
• Excludes Concurrent Design Basis Events
• Assumes Restoration of at Least One Source of Offsite or
Onsite AC Power is Successful Before the Coping Period
Typical Limitations Beyond SBO Coping
• Battery Depletion
• Water Sources Run Out – CST Inventory
• RCS Inventory Losses - PWR RCP Seal Leakage
• BWR Suppression Pool Heat-up & Saturation
• Emergency Lighting Battery Packs Deplete
• Increasing Manual Actions for Available Personnel as
SBO Time Increases
Beyond SBO Coping Strategies
• Medium Size Generators to Re-Energize Battery Chargers
• Emergency Engine Driven Pumps to Replenish Water Sources
– CST Make-up
Medium Size Generators and Pumps to Restore RCP Seal
RCP Shutdown Seal Package Designs to Limit Leakage
BWR Hardened Wetwell Venting Systems and Suppression
Pool Make-up with Cool Water
Helmet Mounted LED Lights for Personnel or Longer Lasting
LED Emergency Lights
Pre-Plan and Pre-Stage More Emergency Equipment to Make
Manual Actions Easier and Train More Personnel to Use it
What is FLEX?
• Response to NRC Mitigating Strategies Order (EA 12-
• Provides a diverse and flexible means to prevent fuel
damage while maintaining containment function in beyond
design basis external event conditions resulting in an:
• Extended Loss of AC Power, and
• Loss of Normal Access to the Ultimate Heat Sink
• Objective:
• Establish an essentially indefinite coping capability by relying upon
installed equipment, onsite portable equipment, and pre-staged
offsite resources
Diverse & Flexible Coping Capability (FLEX)
Prevention of
Fuel Damage
Protection of
Plant Equipment
Diverse & Flexible
SBO Coping
Design Basis
External Events
SBO Coping
Design Basis
External Events
Current plus FLEX
Tier 1 FLEX Approach
Mitigation of
Loss of Ultimate
Heat Sink
(Other Items in
Mitigation of
Beyond Design
Seismic Event
(Tier 1)
Extended Station
Blackout Coping
sufficient to allow
initiation of FLEX
Mitigation of
Loss of
Spent Fuel Pool
includes Diverse
(Tier 1)
Diverse &
Flexible Mitigation
Mitigation of
Beyond Design
Basis Flooding
(Tier 1)
Mitigation of
Other Beyond Design
Bases External Events
(Tier 1 Support)
Reliable &
BWR Containment
(Tier 1)
Mitigation of Large
Fires & Explosions
(Security Related)
(Tier 1)
Additional Support
Equipment from other
plants and Regional
Support Centers
Seismic &
(Tier 1)
Process for
Identifying &
Impact of New
(Tier 3)
& Multi-Unit
(Tier 1)
FLEX Mitigation Strategies
• FLEX employs a three phase approach:
Phase 1 - Initially cope by relying on installed plant
Phase 2 - Transition from installed plant equipment
to onsite FLEX equipment,
Phase 3 - Obtain additional capability and
redundancy from offsite equipment until
power, water, and coolant injection
systems are restored or commissioned.
• Diverse and flexible to enable deployment of the
strategies for a range of initiating events and plant
Representative High-level Example
• Phase 1 Initial Coping Capability
• Use RCIC for RPV makeup from suppression pool
• Rely on DC Power for key instrumentation and controls
• Phase 2/3 Extended Coping Capability
• Charge battery to maintain DC power
• Use Reliable Hardened Vent for containment heat removal
• Provide extended RPV makeup with portable pump
Representative High-level Example
• Phase 1 Initial Coping Capability
• Turbine-driven AFW for SG makeup from Condensate Storage
• Rely on DC Power for key instrumentation and controls
• Phase 2/3 Extended Coping Capability
• Charge battery to maintain DC power
• Provide extended SG makeup with portable pump
• Provide RCS makeup with portable pump, as needed
NRC Advance Notice of Rule Making
• Rule Making Objectives
• What specific objectives should the SBO rule be designed to
• How should actions taken in the NTTF 4.2 be used?
• What regulatory approach to SBO mitigation that follows the
conceptual approach outlined in NTTF 4.1?
• How can regulatory action in NTTF 8.0 be best integrated with
• How can regulatory action in NTTF 5.1 be best integrated with
• How can regulatory action in NTTF 7.1 be best integrated with
NRC Advance Notice of Rule Making
• Relationship between 10CFR 50.63 and the new SBO
• Keep existing rule and supplement with scenarios that go beyond
the existing rule.
• Integrate existing rule with new requirements into a new rule for
• Supersede the existing SBO rule with an enveloping rule.
• Comments have been submitted, ACRS meeting to be
• Ball in NRC court.

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