ML23135A226
| ML23135A226 | |
| Person / Time | |
|---|---|
| Issue date: | 05/11/2023 |
| From: | Tanya Smith Office of Nuclear Security and Incident Response |
| To: | |
| References | |
| Download: ML23135A226 (1) | |
Text
Evacuation Time Estimate Updates and Protective Action Strategies 55th National Conference on Radiation Control May 8-11, 2023 Todd Smith, PhD Senior Level Advisor for Emergency Preparedness and Incident Response Office of Nuclear Security and Incident Response
NRC standards for protective actions require ETEs
- NPP operators must consider a range of protective actions, including evacuation and sheltering
- Guidelines for the choice of protective actions, consistent with Federal guidance, are developed and in place
- Evacuation time estimates (ETEs) have been developed by NPPs and are used in the formulation of protective action strategies
- ETEs are updated on a periodic basis
Evolution of Evacuation Time Estimate (ETE) Policy ETE Regulations In 1980, ETEs required as part of emergency plan, but updates not required In 2011, NRC published regulatory requirements for use of ETEs to inform protective actions and to require updates after every decennial census ETE Guidance Guidance updates reflected advancements in state-of-the-art and state-of-practice
- 1980: NUREG-0654/FEMA-REP-1
- 1992: NUREG/CR-4831, State of the Art in Evacuation Time Estimate Studies for Nuclear Power Plants
- 2004: NUREG/CR-6863, Develop of Evacuation Time Estimate Studies for Nuclear Power Plants
- 2011: NUREG/CR-7002, Criteria for Development of Evacuation Time Estimate Studies
- 2021: Revision 1 to NUREG/CR-7002
NUREG/CR-7269, Enhancing Guidance for Evacuation Time Estimate Studies State-of-the-art traffic simulation models used to better understand evacuation dynamics and to develop insights for protecting the public and first responders ETE Study provides insights into effective evacuation
ETE study models support detailed analyses
Shadow evacuation has minimal impact on those closest to release point Example Results for Large Population Site Model for various shadow participation rates (by percent)
Model boundary conditions capture relevant features Example Results for Medium Population Site Model Medium Population Site Model Model Extent (Miles)
Automated traffic control (ATC) as effective as manual traffic control (MTC)
Example Results for Large Population Site Model Large Population Site Model
The sensitivity of important parameters is known Population Mobilization Time Background and Heavy Vehicle Traffic Roadway Impact Free-flow Speed Adverse Weather Processing Time Step Random Seed Uncertainty Demand Variables Supply Variables Process Variables
Key insights from the ETE Study
- Shadow evacuation is appropriately modeled in ETE studies
- Tradeoffs on use of manual traffic control should be considered
- Important Demand parameters
- Population
- Mobilization time (including adverse weather)
- Important Supply (capacity) parameters
- Traffic control (intersections, traffic lights, etc.)
- Roadway impacts
- Useful measures of effectiveness (MOEs) to demonstrate model performance were identified
Revisions to guidance in NUREG/CR-7002 New Guidance
- Scalable Emergency Planning Zone (EPZ)
- Model boundary conditions
- Application of microsimulation models
- Modeling adverse weather
- Use of ETEs for siting analyses Revised Guidance
- Manual Traffic Control (MTC)
- Parameter importance
- Updated measures of effectiveness U.S. NRC. NUREG/CR-7002, Revision 1, Criteria for Development of Evacuation Time Estimate Studies, January 2021.
https://www.nrc.gov/reading-rm/doc-collections/nuregs/contract/cr7002/r1/index.html
NRC verifies ETEs are acceptable for use
- ETEs submitted to the NRC are reviewed for completeness
- Comprehensive checklist in Appendix B of NUREG/CR-7002
- Completeness review provides verification of model development
- Validation of ETEs against real world data is desirable
- however, since the accident at Three Mile Island in 1979, there have been no evacuations due to an incident at a nuclear plant in the United States How can we know ETEs are valid?
- Mathematically, multiplying a series of random variables, will produce a new random variable which tends to be lognormal.
- Conversely, normal statistics arise from additive variables.
ETE distribution is lognormal, as expected 0
40 80 120 160 200 0
200 400 600 800 1000 1200 Number of ETEs ETE (minutes)
Distribution of 2012 10-Mile ETE Data
Real world evacuation times are lognormal Mills, et al., Study of Evacuation Times Based on General Accident History, SAND 95-2696C (Sandia 1995) 0%
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0 200 400 600 800 1000 1200 1400 1600 Cumulative Percentage Evacuation Time (minutes)
Evacuation Data Natural Disasters Technological Hazards
& Local Emergencies A few blocks NUREG/CR-6864 Identification and Analysis of Factors Affecting Emergency Evacuations ( NRC 2005)
ORNL/TM-11908, Evacuation Research: A Reassessment, ORNL/TM-11908 (ORNL 1992)
ETEs compare well to real world evacuations 0%
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0 200 400 600 800 1000 1200 1400 1600 Cumulative Percentage Evacuation Time (minutes) 2012 ETEs - 90%
2012 ETEs - 100%
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0 200 400 600 800 1000 1200 1400 1600 Cumulative Percentage Evacuation Time (minutes) 2012 ETEs - 90%
2012 ETEs - 100%
Evacuation Data (Subset) 90% ETE is used to inform protective actions
Comparison of 2 Mile ETE and community evacuations 0%
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0 100 200 300 400 500 600 Cumulative Percentage Evacuation Time (minutes) 2012 ETEs - 90%
2012 ETEs - 100%
Evacuation Data (Subset)
Evacuation Data ETE Data Average Population 5223 5055 Median Population 2275 1649 Max Population 40000 36769 Average Distance (miles) 1.0 1.3 Average Evacuation Time (min) 123 119 Median Evacuation Time (min) 120 113 Numerical Comparison
Current NRC guidance for protective action strategies is based on a study completed in 2010 PAR Study Guidance
Different actions provide different benefits
- NUREG/CR-6953 studied alternative evacuation strategies to reduce public dose during severe accidents.
Radial Lateral Staged NUREG/CR-6953, Review of NUREG-0654, Supplement 3, Criteria for Protective Action Recommendations for Severe Accidents, https://www.nrc.gov/reading-rm/doc-collections/nuregs/contract/cr6953/index.html
Scoping Analysis of MACCS Model Improvements for Study of PARs https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML22096A090 How would MACCS model updates impact the performance of a PAR Study?
Updated models
- Added keyhole evacuation model
- Capability to model up to 500 plume segments
- Added HYSPLIT Atmospheric Transport and Dispersion Model (ATD) in addition to Gaussian
- Enhanced nearfield modeling for building wake effects
- Economic model update
- Release from multiple sources Parameter input selection
- Source terms (non-light-water reactor)
- Timing of protective actions and cohort selection
- Dose coefficients, shielding and exposure factors
Source term characteristics are key drivers of risk estimates PAR Study examined rapidly progressing scenario Other realistic accident scenarios progress more slowly Accident timing and release characteristics have large impact on potential consequence estimates
Scoping Analysis of MACCS Model Improvements for Study of PARs https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML22096A090 Analysis Conclusions Not recommending changes to current protective action strategy guidance Scoping analysis showed fewer potential health consequences than the original PAR study Choice of source term had largest impact Source term coupled with keyhole evacuation model impacted the number of displaced individuals Minimal impact of updated shielding parameters Analysis provides assessment of updated MACCS modeling capabilities and insights into parameter sensitivity to inform future efforts
NRC research provides key insights into evacuation NUREG/CR-6864 Identification and Analysis of Factors Affecting Emergency Evacuations ( NRC 2005)
- Evacuations are effective NUREG/CR-6981 Assessment of Emergency Response Planning and Implementation for Large Scale Evacuations (NRC 2008)
- Effectiveness in implementing evacuations is directly related to the level of preparedness NUREG/CR-7285 Nonradiological Health Consequences of Evacuation and Relocation (NRC 2021)
- Displaced populations are more likely to experience negative health outcomes following an emergency event
NRC regulations and guidance on protective actions provide for protection of public health and safety
- Evacuations remain major element of protective action strategies
- Evacuations are effective, but do carry risk
- ETE studies enhance evacuation planning
- ETEs support implementation of protective action strategies
- NRC continues to evaluate the basis for protective action strategies to ensure our understanding reflects the state of knowledge
Contact Information Todd Smith, PhD Senior Level Advisor for Emergency Preparedness &
Incident Response todd.smith@nrc.gov 301-287-3744