Sustaining Resilience of U.S. Nuclear Power Plants to
Extreme Events
Mike Franovich
Director (a), USNRC/JLD
March 27-29, 2017
Lessons Learned:
Near-Term Task Force
• Within weeks of the accident, USNRC created a task force to review the events and provide recommendations to enhance safety at U.S. plants
– Report issued July 2011
– Concluded that a similar sequence of events in the U.S. was unlikely and there were no imminent risks of continued operation and licensing activity
– Identified 12 overarching potential safety enhancements
2
USNRC Leadership
3
• Commission
• Steering Committee – Directorate/Division
– Three Tiers of Actions • (orders, RFI, rulemaking,
evaluations)
– Guiding Principles
– Senior Leadership Reflections – Visit to Japan
– Frequent engagement with U.S. industry leadership and other stakeholders
USNRC Orders and Request for Information
4
• Three Orders were issued – Mitigation strategies for beyond design basis
events
– Spent fuel pool level instrumentation
– Severe accident capable hardened vent for BWR Mark I and II containments
• Request for information was issued – Conduct walkdowns for seismic and flood
protection
– Reevaluate seismic and flood hazards using present day methods
– Evaluate emergency preparedness staffing and communications
Learning the Lessons
5
Continued Oversight of Safety Enhancements
Safety Evaluations and Verification of Compliance
Implementation with NRC-Endorsed Industry Guidance
Three Orders and Request for Information
Near-Term Task Force Report G
ain
ing
in
sig
hts
an
d e
nh
an
cin
g
ap
pro
ac
he
s
2011
Today
2012
Safety has been significantly improved
6
Recommendation Status
Ensuring Protection
from External Events
2.1 – Reevaluation of seismic & flooding hazards Ongoing
2.2 – Periodic reconfirmation of hazards Assessment Complete
2.3 – Seismic & flooding hazard walkdowns Closed
Other – Reevaluate other external hazards Assessment Complete
Enhancing Mitigation of
Beyond-Design-Basis
Events
4.1 – Mitigation of beyond design basis events rulemaking* Draft Final Rule Complete
4.2 – Mitigation of beyond design basis events order Ongoing
5.1 – Severe accident capable hardened vents order Ongoing
5.2 – Vents for other containment designs Closed
6 – Hydrogen control and mitigation Closed
7.1 – Reliable spent fuel pool instrumentation Closed
7.2- 7.5 – Spent fuel pool water makeup capability* Draft Final Rule Complete
Strengthening
Emergency
Preparedness for Multi-
Unit Events
8.1-8.4 – Onsite emergency response capabilities* Draft Final Rule Complete
9.1-9.4 – Rulemaking to enhance emergency plans* Draft Final Rule Complete
10.1-10.2 – Analyze and evaluate other EP considerations* Draft Final Rule Complete
10.3 – Evaluate ERDS capabilities Closed
11.2&11.4 – Decision-making and public education Closed
Regulatory Philosophy 1 – Reassess regulatory framework Closed
12.1 – Include defense in depth requirements within ROP Closed
12.2 – Enhance staff training on severe accidents & SAMGs Closed
Radiological
Consequences
11.3 – Real time radiation monitoring within EPZ Assessment Complete
Other – Containment vent filters/filtering strategies Closed
Other – Expand EPZ size beyond 10 miles Closed
Other – Pre-stage KI to residents beyond 10 miles Closed
Other – Expedited transfer of spent fuel to dry storage Closed
*Integrated into MBDBE rulemaking
Activities substantially complete
7
*For illustrative purposes only Today
Mitigating Strategies
Spent Fuel Pool Instrumentation
Hardened Vents
Walkdowns
Seismic Reevaluations
Flooding Reevaluations
Staffing & Communication
Mitigation of Beyond Design Basis Events
Containment Protection/Release
Reduction
Ord
ers 5
0.5
4(f) R
equ
ests R
ule-
makin
g
2012
85/99 units in compliance
Complete
Phase 1 and 2 ISEs complete
27/61 sites completed 2.1 response
Complete
Draft final rule delivered to Commission
2013 2014 2015 2016 2017 2018 2019 2020
Hazard acceptance letters issued
Complete
Closed
Tier 2&3 Resolution plans delivered to Commission
Mitigating Strategies
Requires a three-phase approach for maintaining or
restoring core cooling, containment, and spent fuel
cooling
8
Phase
Licensee may use
Initial
Installed
equipment
Transition
Portable, onsite
equipment
Final Resources
obtained from offsite
+
+
Fundamental cornerstone of United States approach
Mitigating Strategies – What is FLEX?
• NEI 12-06 (Diverse and Flexible coping strategies (FLEX)
Implementation Guide)
– Endorsed by the USNRC August 2012 to support implementation
of Mitigating Strategies Order
– FLEX provides a means to prevent fuel damage while
maintaining containment function and spent fuel pool cooling
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
9
Establishes an essentially indefinite coping
capability by relying upon installed equipment,
onsite portable equipment, and pre-staged
offsite resources
Mitigating strategies implementation
is nearing completion
• USNRC conducting
inspections confirming
order compliance
• No substantive
inspection findings to
date
• Transition to long-term
oversight plan 10
Working to expedite
BWR vent order closure • Applies to BWRs with certain
designs (Mark I/II)
• Vents help control pressure by
removing heat
• May help prevent core
damage
• Required to work when
normal power is lost
• Must continue to function if
core damage/melting occurs
• Developing inspection
procedure to confirm
compliance 11
• U.S. plants perform probabilistic
seismic hazard analyses following
USNRC guidance (RG 1.208)
• CEUS licensees (94 units/58 sites)
– Regional CEUS seismic source
– Regional CEUS ground motion
– Plant-specific site analyses
• Western licensees (6 units/3 sites)
– Regional source and ground
motion
models developed by each
licensee
– Plant-specific site analyses
12
Development of Seismic Hazard
Seismic – High Frequency (example)
U.S. BWR site
(example)
• SSE ≥ GMRS for frequencies 1-10 Hz
• Above 10 Hz GMRS > SSE
13
Seismic hazard reevaluation
is on schedule
14
Phase 2
Decisions
cost-benefit assessment
Hazard Acceptance
Review
(Complete)
Mitigation Strategies
Assessment
Interim Actions
(complete)
High-Frequency
Evaluation
Spent Fuel Pool
Evaluation
Seismic
Probabilistic
Risk Assessment
(18 sites – 2017-2019) Im
ple
me
nt G
uid
an
ce
Sa
fe
ty E
nh
anc
em
en
ts
Op Ex
Use SPRA technology where insights
would be most useful to safety
Leverage prior seismic risk or margins
studies (e.g., IPEEE)
Consider actual plant performance in
earthquakes – Kashiwazaki-Kariwa,
Onagawa, Fukushima, North Anna
Weigh outcomes against USNRC Safety
Goals, risk metrics
Reevaluated Flood Hazards
15
Consider associated effects:
• Wind waves and run-up effects; • Hydrodynamic loading
(including debris); • Sediment deposition and
erosion;
• Concurrent site conditions; • Groundwater ingress; and
• Other pertinent factors.
Flooding action plan implementation
is on schedule Im
ple
me
nt G
uid
an
ce
Sa
fe
ty E
nh
anc
em
en
ts
16
Phase 2
Decisions
cost-benefit assessment
Hazard Acceptance
Review
(Complete)
Mitigation Strategies
Assessments
Interim Actions
(Complete)
Focused Evaluations
(June 2017) Integrated
Assessments
(6 sites - 2018)
Op Ex
Advanced warning time for plant
preparedness and actions is a key
factor for realistic mitigation
strategies
Leverage insights from plant
walkdowns and inspections (wall
penetration seals installation &
integrity)
Performance-based regulation
enables innovative approaches
18
• Performance-based approach and
broad view
• Captures mitigation strategies Order
• Requires reevaluated seismic and
flooding hazards be addressed
• Flexible scheduling option for plant
implementation
Rule establishes an integrated response capability
19
• Assists operators in executing strategies
• Includes:
– Mitigation strategies (post-Fukushima)
– Reevaluated seismic and flooding
hazards
– Extensive damage mitigation guidelines
(post-9/11 strategies)
• Integration with emergency operating
procedures
Rule ensures equipment supports implementation of strategies
20
• Capacity and capability
• Reasonable protection
• Communications capability
• Maintenance
Rule includes comprehensive approach to
organizational readiness/capability
21
• Sufficient staffing
• Systems approach to training
• Periodic drills or exercises
• Ongoing feedback reflected in updates/revisions to
implementation guidance
• USNRC audits before compliance due dates helped
identified plant-specific and generic items to be
resolved
• Reevaluated seismic and flooding information
reflected in assessment of mitigating strategies
• Frequent interactions between USNRC and industry
• Rulemaking process is a systematic approach and
on a pace that allowed implementation operating
experience to be captured under performance
based and risk-informed requirements
Regulatory guidance incorporates operating experience
22
Leveraging FLEX in safety and
security decision making
• Significant investment in equipment
and implementation
• Substantial risk benefits - Example areas:
• Enhancing safety to reduce risk during outages by
using FLEX as an additional layer of defense
• Using FLEX equipment as an additional layer of
defense when emergency equipment are taken
out-of-service while plants are at-power
• Modifying USNRC internal guidance
23
Station blackout risk reduction
for a spectrum of hazards
24
Post-Fukushima Improvements (Mitigation Strategies for ELAP)
SBO Rule (1989) Maintenance Rule (1996) – SSC reliability and availability
Risk Informed Licensing Actions(1990s - present)
Post-9/11 Requirements (B.5.b measures - 2006)
NFPA-805 Fire Protection Standard (2012 – present)
performance-based, risk-informed approaches
SB
O R
isk
Effective transition to ensure lasting benefit – challenges and opportunities
25
• Considerable achievements to date
• Knowledge management effort underway to
sustain organizational competency
• Transition program to long-term inspection
and oversight under existing programs
• Reflect post-Fukushima improvements in
future risk-informed decisions
• Ongoing confirmation of natural hazards
– Potential enhancements to existing USNRC
internal processes
Independent Reviews
26
• U.S. National Academy of Sciences
– Congressionally mandated study
completed
– Phase 1 Fukushima accident
– Phase 2 Spent fuel pool safety and
security
• Advisory Committee on Reactor
Safeguards
– Ongoing review of USNRC staff
actions
Summary
27
• Considerable progress has been made
• Activities have already resulted in
safety improvements
• Additional information can be found
at:
https://www.nrc.gov/reactors/operating/o
ps-experience/japan-dashboard.html
Acronyms • CEUS – Central and Eastern United States
• ELAP – Extended Loss of Alternating-current Power
• FLEX – Diverse and Flexible coping strategies
• ISE – Interim Staff Evaluation
• LCF – Latent Cancer Fatality
• IPEEE – Individual Plant Examination of External Events
• MBDBE – Mitigation of Beyond Design Basis Events
• NEI – Nuclear Energy Institute
• NFPA – National Fire Protection Association
• Op Ex – Operating Experience
• QHO – Quantitative Health Objective
• RFI – Request for Information
• SBO – Station Blackout
• SFP – Spent Fuel Pool
• SPRA – Seismic Probabilistic Risk Assessment
• SSC – Structure, System, or Component
28
Spent Fuel Pool Instrumentation
• Order requires
installation of water level
instrumentation to
indicate the certain
levels
• Milestones: – Order issued in 2012
– Review and schedule
merged with Mitigating
Strategies
30
BWR CPRR Regulatory Analysis Comparison to NRC Safety Goal
• Frequency-weighted
individual LCF risk is
orders of magnitude
below the NRC Safety
Goal QHO
• High-level conservative
estimate using highest
ELAP frequency and
highest conditional LCF
risk about 30 times below
QHO
• Risk reduction from
regulatory alternatives
are within uncertainty
bounds
31