ML23135A226

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ETEs and Protective Actions_55th CRCPD Meeting_May 2023
ML23135A226
Person / Time
Issue date: 05/11/2023
From: Tanya Smith
Office of Nuclear Security and Incident Response
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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 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

ETE Study provides insights into effective evacuation 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 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 Demand Variables Mobilization Time Background and Heavy Vehicle Traffic Roadway Impact Supply Variables Free-flow Speed Adverse Weather Process Variables Processing Time Step Random Seed Uncertainty

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?

ETE distribution is lognormal, as expected

  • Mathematically, multiplying a Distribution of 2012 10-Mile ETE Data series of random variables, will 200 produce a new random variable 160 Number of ETEs which tends to be lognormal.

120

  • Conversely, normal statistics arise from additive variables. 80 40 0

0 200 400 600 800 1000 1200 ETE (minutes)

Real world evacuation times are lognormal Evacuation Data 100%

Natural Disasters 80%

Technological Hazards Cumulative Percentage

& Local Emergencies 60%

40%

20%

A few blocks Mills, et al., Study of Evacuation Times Based on General 0%

Accident History, SAND 95-2696C (Sandia 1995) 0 200 400 600 800 1000 1200 1400 1600 Evacuation Time (minutes)

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 100%

80%

2012 ETEs - 90%

Cumulative Percentage 2012 ETEs - 90%

60% 2012 ETEs - 100%

2012 Evacuation ETEs Data - 100%

(Subset) 40%

20%

90% ETE is used to inform protective actions 0%

0 200 400 600 800 1000 1200 1400 1600 Evacuation Time (minutes)

Comparison of 2 Mile ETE and community evacuations 100%

2012 ETEs - 90%

80% 2012 ETEs - 100%

Evacuation Data (Subset)

Cumulative Percentage 60%

Evacuation ETE Numerical Comparison Data Data 40% Average Population 5223 5055 Median Population 2275 1649 Max Population 40000 36769 Average Distance (miles) 1.0 1.3 20%

Average Evacuation Time (min) 123 119 Median Evacuation Time (min) 120 113 0%

0 100 200 300 400 500 600 Evacuation Time (minutes)

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

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

Source term characteristics are key drivers of risk estimates PAR Study examined rapidly progressing scenario Accident timing and release characteristics have large Other realistic accident scenarios progress more slowly impact on potential consequence estimates

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

NRC research provides key insights into evacuation

- 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

- 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

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