ML23032A466

ANS Riep Wg - EP Planning Basis - February 2023

ML23032A466
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Issue date:	02/01/2023
From:	Tanya Smith NRC/NSIR/DPR
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Planning Basis for Radiological Emergency Preparedness American Nuclear Society (ANS)

Risk-informed Emergency Preparedness (RIEP) Working Group February 1, 2023 Todd Smith, PhD Senior Level Advisor for Emergency Preparedness and Incident Response Office of Nuclear Security and Incident Response U.S. Nuclear Regulatory Commission

The NRC employs a graded approach to EP

• A graded approach is a process by which the safety requirements and criteria are set commensurate with several factors including magnitude of hazards involved, characteristics of a facility, the balance between radiological and nonradiological hazards.

• EP regulations employ a graded approach, which is a risk-informed process Power reactors (low-power testing, power operations, decommissioning)

Research and test reactors Fuel Fabrication Facilities Independent Spent Fuel Storage Installations Monitored Retrievable Storage

Objective of Radiological EP

• The objective of emergency preparedness (EP) is to provide dose savings for a spectrum of accidents that could produce doses in excess of the Environment Protection Agency (EPA) protective action guides (PAG)

• Meeting NRC EP regulations provides reasonable assurance that adequate protective measures can and will be taken in the event of a radiological emergency Reasonable assurance finding is made before a nuclear facility is licensed Inspected over the lifetime of that facility

Reasonable assurance is not absolute assurance Our emergency planning requirements do not require that an adequate plan achieve a preset minimum radiation dose saving or a minimum evacuation time for the plume exposure pathway emergency planning zone in the event of a serious accident.

It is implicit in this concept of adequate protective measures that a determination that a particular EPZ size will provide adequate protective measures does not in fact mean that emergency planning will eliminate, in every conceivable accident, the possibility of serious harm to the public.

[Shoreham CLI-86-13, 24 NRC 22, 30 (1986)]

Plans are useless, but planning is indispensable

- Dwight D. Eisenhower Emergency Planning:

• Reduces complex decision-making in an emergency

• Simplifies the choice of possible responses

• Allows for:

- Consistent and practiced approaches

- Addressing a spectrum of challenges irrespective of causes

What should be used as a basis for EP?

In the 1970s, the Conference of Radiation Control Program Directors (CRCPD) asked, What is the accident we should be planning for? What is the planning basis?

A combined NRC and EPA Task Force considered different bases:

• Risk

- Not used as a basis for planning for other hazards

- Public has subjective perception of risk (intuitive vs. quantitative)

- Would require setting an acceptable level of risk (out of scope)

• Probability

- Society tolerates more probable events without specific planning

- However, accident probability provides perspective

• Cost effectiveness

NUREG-0396 Planning Basis for EP The consequences from a spectrum of accidents, tempered by probability considerations, should be considered to scope the planning efforts for:

• The distance to which planning for predetermined protective actions is warranted

• The time dependent characteristics of a potential release

• The type of radioactive materials The planning basis included a recommended 10 mile plume exposure path emergency planning zone (EPZ) and a 50 mile ingestion pathway zone NUREG-0396, Planning Basis for the Development of State and Local Government Radiological Emergency Response Plans in Support of Light Water Nuclear Power Plants, November 1978

EP EPZ Planning Distance The distance to which planning for predetermined protective actions is warranted

• The EPZ is a planning tool it was the consensus of the Task Force that emergency plans could be based upon a generic distance out to which predetermined actions would provide dose savings beyond the generic distance it was concluded that actions could be taken on an ad hoc basis The EPZ guidance does not change the requirements for emergency planning, it only sets bounds on the planning problem.

NUREG-0396, Planning Basis for the Development of State and Local Government Radiological Emergency Response Plans in Support of Light Water Nuclear Power Plants, November 1978

EPZ simplifies decisions PAG for a prompt response PAR PAD Protective Action Guide (PAG) projected dose to an individual member of the public that warrants protective action Protective Action Recommendation (PAR) PAG recommended protective measure from the nuclear power plant to offsite response PAD PAR organizations (OROs)

Protective Action Decision (PAD) measures taken in response to an actual or anticipated radiological release

The EPZ is scalable

• EPZ size based on the consequences from a spectrum of accidents, tempered by probability considerations.

• NRC regulations provide for scalable EPZs

• Reactors have been approved for a 5 mile EPZ in the past

• Depending on facility type, the EPZ may be at the site-boundary or have no EPZ

• Considerable number of studies since the 1980s on sizing EPZs for passive and advanced reactor designs, many based on the NUREG-0396 methodology

Considerations for EPZ size The size of the EPZ is based on the following considerations:

a. Projected doses from traditional design basis accidents would not exceed Federal PAG levels outside the EPZ

b. Projected doses from most core melt sequences would not exceed Federal PAG levels outside the EPZ

c. For the worst-case core melt sequences, immediate life-threatening doses would generally not occur outside the EPZ

d. Detailed planning within [the EPZ] would provide a substantial base for expansion of response efforts in the event that this proved necessary NUREG-0396, Planning Basis for the Development of State and Local Government Radiological Emergency Response Plans in Support of Light Water Nuclear Power Plants, November 1978

The EPZ size is risk-informed Design Basis Accidents Beyond Design Basis NUREG-0396, Planning Basis for the Development of State and Local Government Radiological Emergency Response Plans in Support of Light Water Nuclear Power Plants, November 1978

EP is a matter of judgment A reading of the Report [NUREG-0396] indicates clearly that the margins of safety provided by the recommended 10-mile radius were not calculated in any precise fashion but were qualitatively found adequate as a matter of judgment.

[55 FR 5605, Feb 16, 1990]

EPZ size methodology can be applied to any facility EPRI TR-113509, Technical Aspects of ALWR Emergency Planning, Final Report, September 1999

Whats the likelihood of events considered?

NUREG-075/014 (WASH-1400), Reactor Safety Study: An Assessment of Accident Risks in U.S. Commercial Nuclear Power Plants, October 1975

down to 1 chance in 10 lifetimes of the universe NUREG-075/014 (WASH-1400), Reactor Safety Study: An Assessment of Accident Risks in U.S. Commercial Nuclear Power Plants, October 1975

Shouldnt you be planning for the worst-case?

Regulation does not require dedication of resources to handle every possible accident that can be imagined. The concept of the regulation is that there should be core planning with sufficient planning flexibility to develop reasonable response to those very serious low probability accidents which could affect the public.

[SONGS CLI-83-10, 17 NRC 528, (1983)]

Capabilities are available at State and Federal level The Task Force believes that it is not appropriate to develop specific plans for the most severe and most improbable Class 9 events.

The Task Force, however, does believe that consideration should be given to the characteristics of Class 9 events in judging whether emergency plans based primarily on smaller accidents can be expanded to cope with larger events.

The planning basis recommended by the Task Force therefore includes some of the key characteristics of very large releases to assure that site specific capabilities could be effectively augmented with general emergency preparedness (response) resources of the Federal government should the need arise.

NUREG-0396, Planning Basis for the Development of State and Local Government Radiological Emergency Response Plans in Support of Light Water Nuclear Power Plants, November 1978

Response capabilities are coordinated across levels Licensee State Federal

Planning Time The time dependent characteristics of a potential release NUREG-0396, Planning Basis for the Development of State and Local Government Radiological Emergency Response Plans in Support of Light Water Nuclear Power Plants, November 1978

Effectiveness of protective actions related to timing The guidance cannot be very specific because of the wide range of time frames associated with the spectrum of accidents considered.

Therefore, it will be necessary for planners to consider the possible different time periods between the initiating event and arrival of the plume and possible time periods of release in relationship to time needed to implement protective actions.

NUREG-0396, Planning Basis for the Development of State and Local Government Radiological Emergency Response Plans in Support of Light Water Nuclear Power Plants, November 1978

Conservatively bounds timing of severe accidents NUREG-075/014 (WASH-1400), Reactor Safety Study: An Assessment of Accident Risks in U.S. Commercial Nuclear Power Plants, October 1975

Time basis informs functional requirements

• nuclear power reactor licensees shall establish and maintain the capability to assess, classify, and declare an emergency condition within 15 minutes after the availability of indications to plant operators that an emergency action level has been exceeded

• A licensee shall have the capability to notify responsible State and local governmental agencies within 15 minutes after declaring an emergency

• The design objective of the prompt public alert and notification system shall be to have the capability to essentially complete the initial alerting and initiate notification of the public within the plume exposure pathway EPZ within about 15 minutes Appendix E to 10 CFR Part 50

Release Characteristics The type of radioactive materials NUREG-0396, Planning Basis for the Development of State and Local Government Radiological Emergency Response Plans in Support of Light Water Nuclear Power Plants, November 1978

WASH-1400 informed early understanding NUREG-075/014 (WASH-1400), Reactor Safety Study: An Assessment of Accident Risks in U.S. Commercial Nuclear Power Plants, October 1975

Our understanding of accidents has evolved NUREG/BR-0359, Revision 3, Modeling Potential Reactor Accident ConsequencesState-of-the-Art Reactor Consequence Analyses: Using decades of research and experience to model accident progression, mitigation, emergency response, and health effects, October 2020

and will continue to evolve Commission Policy Statement on Advanced Reactors the Commission expects, as a minimum, at least the same degree of protection of the environment and public health and safety and the common defense and security that is required for current generation light-water reactors (LWRs)

The Commission also expects that advanced reactor designs will comply with the Commissions safety goal policy statement.

In addition, the Commission expects that the safety features of these advanced reactor designs will be complemented by the operational program for Emergency Planning (EP). This EP operational program, in turn, must be demonstrated by inspections, tests, analyses, and acceptance criteria to ensure effective implementation of established measures.

US NRC, Final Policy Statement: Policy Statement on the Regulation of Advanced Reactors, [NRC-2008-0237];

73 FR 60612, October 14, 2008.

EP is a final, independent layer of defense in depth DID is an approach to designing and operating nuclear facilities that prevents and mitigates accidents that release radiation or hazardous materials. Defense in depth includes the use of access controls, physical barriers, redundant and diverse key safety functions, and emergency response measures.

CAUTION! Some references do not clearly differentiate DID of design from siting and EP.1 NEI 18-04, Rev. 1, Risk-Informed Performance-Based Technology Inclusive Guidance for Non-Light Water Reactor Licensing Basis Development August 2019.

IAEA approach provides similar considerations IAEA. Addressing the issue of EPZ sizing for SMR, Technical Meeting on Challenges in the Application of the Design Safety Requirements for Nuclear Power Plants to Small and Medium Sized Reactors, September 4th, 2017

The planning basis informs EP planning functions Ensure capabilities exist to detect, classify, notify, assess, mitigate, and effectively respond to an emergency Planning Basis Emergency Planning Needs and Functions EPZ size, exposure pathways, protective Distance action strategies Spectrum Timeliness of classification and notification, of Time protective action strategies, mitigation Accidents Detection and assessment capabilities, Materials radiological protection, mitigation

Emergency preparedness is evidence-based Protective Action Decisionmaking in the Intermediate Phase (NUREG/CR-7248)

Evacuation Time Estimate Study (NUREG/CR-7269)

Emergency Planning Zone (EPZ) Size Methodology Sensitivity of Dose Projections to Weather Analysis of the Effectiveness of Sheltering-in-Place Use of Heating and Ventilation Systems while Sheltering-in-Place Dose Reduction Effectiveness of Masks Nonradiological Health Impacts of Evacuations and Relocations (NUREG/CR-7285)

MACCS Consequence Model Improvements Impact on Protective Action Strategies

Roles and Responsibilities FEMA - Technical NRC State / Local Hazards Division Review Set EP standards &

Responsible for emergency reviews and approves Reviews State and local planning and response for Review Findings licensee plans radiological emergency the community plans against planning Considers FEMA findings of Assess their own standards offsite plans in reasonable Assist capabilities and needs assurance determinations Can assist State & locals in Voluntarily participate in planning, if asked licensee planning NRC Licensee Develops and maintains radiological emergency plans.

(NRC review and approval)

Examples of Risk-Informed Approaches to EP Regulatory Basis for Decommissioning Rule The overall objective of EP is to provide dose savings for a spectrum of accidents that could produce offsite doses in excess of PAGs EPZs are areas for which planning is needed to assure that prompt and effective actions can be taken to protect the public in the event of an accident For a facility in decommissioning:

• The spectrum of accidents are significantly fewer than at an operating plant

• Design Basis Accidents will not exceed 1 rem offsite

• At least 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> available to mitigate or initiate protective actions

Levels of Decommissioning Applying the planning basis to regulation Proposed rule for power reactors based on the reduction in risk at four levels of decommissioning, including the time when spent fuel has sufficiently decayed such that it would not reach self-ignition temperature in 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> under adiabatic heatup conditions 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> Initiating Event Mitigate or (Severe Earthquake) Initiate Response Time Federal Register NoticeProposed Rule, Regulatory Improvements for Production and Utilization Facilities Transitioning to Decommissioning: Proposed Rule, 87 FR 12254 March 3, 2022

Conservatively assumes spent fuel pool damaged and drains instantaneously NUREG-2161, Consequence Study of a Beyond-Design-Basis Earthquake Affecting the Spent Fuel Pool for a U.S.

Mark I Boiling Water Reactor, September 2014

Conservatively assumes unfavorable heat transfer Transmittal of Reports to Inform Decommissioning Plant Rulemaking for User Need Request NSIR-2015-001, dated May 31, 2016 (ADAMS Accession No. ML16110A416)

Conservatively assumes instantaneous release Transmittal of Reports to Inform Decommissioning Plant Rulemaking for User Need Request NSIR-2015-001, dated May 31, 2016 (ADAMS Accession No. ML16110A416)

Risk-informed regulations cover uncertainty Proposed regulatory criteria Minimum time margin: + 8.5 hr Median time margin: + 24 hr Realistic time margin: + days 10 hr Margin in 10 hr criteria Time

Key Takeaways Emergency Preparedness EP ensures protective actions can and will be taken EP regulations are risk-informed and commensurate to the potential hazards presented by the class of facility Informed by characteristics of a spectrum of accidents Guidance and tools to support planning functions are informed by insights from PRAs EP is not based on risk or probability of an accident occurring Requires judgmentbacked by evidence