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NEI Response to NRC Review Comments on NEI 24-05 for 6/23/25 Public Meeting
	ML25175A055
Person / Time
Site:	Nuclear Energy Institute
Issue date:	06/23/2025
From:	; Nuclear Energy Institute
To:	; Office of Nuclear Reactor Regulation
References
	NEI 24-05
	Download: ML25175A055 (1)
	v • d • e

The team thanks the NRC staff for the detailed review and thoughtful comments

Also appreciate the multiple interactions to clarify intent, meaning, etc.

NRC Review of NEI 24-05

Schrader 2.2: formatting error

Schrader 4.2.1: Reference error (53 FR 36955)

Bucholtz 4.2.3: event vs. accident terminology

Schrader 5.3.1: and vs of

Team Response:

NEI 24-05 will be updated to address comments Typos, Formatting Errors, Text Clarifications

Three comments regarding preliminary LBE screening step of EPZ determination:

Definition of very low doses

Details of bounding dose analysis

Timing screening criteria

Team Response:

It is incumbent on the applicant to determine the specific criteria and justification for preliminary LBE screening, based on their site and plant characteristics

However, the text in NEI 24-05 will be updated to include possible criteria based on previously NRC-accepted values, such as:

2.5 mrem (10% of background TEDE), utilized by LMP and in NLWR PRA standard NRC Comment - Buchlotz 4.2.1

Part of preliminary LBE screening includes consideration of time available for protective actions for members of the public, including those on site. Clarify how the screening would be performed for the time available for the implementation of protective measures for personnel within the site boundary.

Team Response:

The 2nd PEP EPZ criteria in §50.33(g)(2)(i)(B) states that the EPZ is the area within which pre-determined, prompt protective measures are necessary

Pre-determined prompt protective measures are actions taken by OROs in offsite locations to protect the public; therefore, this term is not relevant when examining the timing or measures that a licensee will take within the site boundary.

Protective measures for onsite members of the public and plant workers are taken by the licensee using actions developed under the requirements of

§50.160(b)(1)(iii)(B)

NEI 24-05 text will be updated to provide greater clarity NRC Comment - Buchlotz 4.2.1

How can the determination that security events can be eliminated from detailed consideration be made as applicable to all future implementations to support specific licensing applications?

Team Response:

Through compliance with regulatory requirements for protection against the design basis threat and beyond design basis threats, an applicant can establish a basis that security events are adequately considered for EPZ determination

Consistent with NuScale and TerraPower EPZ topicals

Security events explicitly considered within the emergency plan

If an alternative pathway is utilized that does not provide protection against the DBT, such as the draft § 53.860(a)(2)(i), then explicit consideration of security events for EPZ determination may be necessary

NEI 24-05 text will be updated to provide greater clarity NRC Comment - Hart 4.2.3

Clarify dose metrics utilized for 1 rem and 200 rem assessments conducted as part of EPZ determination

Team Response:

The 1 rem analysis is conducted utilizing 96-hour TEDE

For the 200-rem analysis, to promote consistency with NUREG-0396 and other NRC-approved methods, the NEI 24-05 will be updated to clarify the usage of 24-hour acute whole-body dose (or acceptable surrogate, such as red bone marrow)

NRC Comment - Bucholtz 4.3.1 & Hart 4.3.1/4.3.2/App C

As part of the EPZ determination, frequency criteria are utilized for the evaluation of the 1 rem and 200 rem dose versus distance curves. The selected values were derived from NUREG-0396 Appendix I. What is the technical basis for applying the proposed frequency metrics which are representative of older large light water reactor data, to new reactor designs, instead of identifying the distance at which the likelihood of exceeding the dose level of interest dropped substantially directly from the cumulative dose-versus-distance curves?

Team Response (Part 1/2):

The LMP LBE identification and categorization process includes events with frequencies as low as 5E-7 per year, with consideration of uncertainties.

To ensure the efficient and effective allocation of resources, the frequency of events must be considered and is explicitly referenced in §50.33(g)(2)(i)(A).

Recent NRC EO emphasizes thresholds to ensure a focus on credible, realistic risks

Since the LBEs extend to frequencies of 5E-7, examining the shape of dose versus distance curves for EPZ determination without a consideration of frequency could result in EPZ determination based on very infrequent events and an inefficient allocation of EP resources NRC Comment - Bucholtz 4.3.2

Team Response (Part 2/2):

EPZ determination based on dose versus distance curves without frequency considerations could result in EPZs that are inconsistent with §50.33(g)(2)(i)(A).

Plants with very different risk profiles having similar EPZs

Dose versus distance curves do not always have clear drop-offs, which could cause subjective results (see 1 rem curve of Figure I-11 from NUREG-0396)

Use of frequency metrics consistent with TerraPower EPZ method, although applied in slightly different manner NRC Comment - Bucholtz 4.3.2

Section 4.3.2 states that the Criterion B evaluation aligns with the approach in NUREG-0396 and ensures an equivalent level of protection for radiological emergencies that may result in early health effects. What is meant by an equivalent level of protection, and how is this accomplished?

Team Response:

NEI 24-05 will be updated to clarify that the approach and metrics align with those utilized in NUREG-0396 Appendix I (rather than produce a numerically equivalent result) and is sufficient to ensure an adequate level of protection NRC Comment - Hart 4.3.2

The methodology in NEI 24-05, section 4.3.3 does not appear to direct a cliff-edge evaluation be performed if potential cliff-edge behavior is identified. Provide the technical basis for not confirming that there are no cliff-edge effects and that there is adequate defense in depth, if potential cliff-edge behavior is identified, or revise NEI 24-05.

Team Response:

The uncertainty and cliff-edge evaluations are insightful regarding available margin to the established criteria

Specific quantitative thresholds are not provided for the cliff-edge evaluation, as it includes both quantitative and qualitative aspects

The available margin and impact of uncertainties, including confidence in the modeling results, are reviewed as part of the integrated decision-making process (IDP) and defense-in-depth analysis. The IDP review determines the final EPZ size when considering available information.

NEI 24-05 text will be updated to clarify the role of IDP in the assessment of margin and aspects considered for the uncertainty and cliff-edge analysis NRC Comment - Bucholtz 4.3.3

Is prompt protective measures intentionally left out of section 4.4.2, Derived Distance at or within the Site Boundary?

Team Response:

Yes, it was intentionally not included. Section 4.4.2 addresses EPZs at or within the site boundary. Protective measures for onsite members of the public and plant workers are taken by the licensee using actions developed under the requirements of §50.160(b)(1)(iii)(B) and not a consideration of

§50.33(g)(2)(i)(B).

NRC Comment - Schrader 4.4.2

Regarding reasons for a non-uniform EPZ, meteorological conditions listed as a possibility. Considering that the actual meteorological conditions during an event are unknown for the determination of the PEP EPZ size, how would this potential consideration be included in the analyses? Are there examples of the meteorological and site conditions would always reduce the dose in certain directions such that it may lead to consideration of non-uniform PEP EPZs?

Team Response:

NEI 24-05 text will be updated to remove meteorological conditions as a potential factor.

NRC Comment - Hart 4.6.2

How close is this section intended to get an applicant to an approved EAL scheme?

Team Response:

A technology-inclusive ECL development framework is proposed - it provides high-level guidance on developing an emergency classification scheme based on the LBEs and the RSF structure from LMP and TICAP

An applicant could develop a site-specific emergency classification scheme based on the guidance and submit it to the NRC for review NRC Comment - Schrader 5.3

How would this guidance address a situation where an event > 1 rem/96 hrs is known but the accident progression time slow enough to allow ad hoc protective actions?

Team Response:

Assuming the comment is directed at protective measures for onsite personnel

For ad hoc situations, the licensee could implement plans developed for other scenarios, or depending on the available time, release onsite personnel early from assigned shifts

NEI 24-05 text will be updated to provide further clarity NRC Comment - Schrader 5.3

Is section 5.3.5, Staffing and Operations, intended to be enough guidance for an applicant to determine appropriate staffing levels?

Team Response:

The applicant would determine appropriate staffing levels based on the needs of the developed emergency plans

The staffing requirements are determined as a result of a performance based analyses of response specific to the site. Section 5.3.5 attempts to provide insights as to what elements may be desired to be included when performing the performance based analyses.

Welcome any specific feedback or suggestions from the NRC on how this guidance might be improved or clarified to better support applicants in this area.

NRC Comment - Schrader 5.3.5

Why is Planning Activities - §50.160(b)(1)(iv) described as only centers on onsite and offsite (if necessary) planning activities?

Team Response:

Sentence is currently poorly worded and will be revised.

§50.160(b)(1)(iv) includes requirements that would not be applicable if the licensee had a site boundary EPZ.

NRC Comment - Schrader 5.4

Onsite Planning Activities, why are planning activities for Public information, Coordination with safeguards contingency plan, Communication with NRC, and Site familiarization training considered largely outside the scope of this project?

Team Response:

These are aspects of the emergency plan that are largely not informed by LMP information and existing guidance elsewhere is adequate

NEI 24-05 text will be updated to provide reference to examples of existing guidance on these topics, such as:

NUREG/CR-7032, "Developing an Emergency Risk Communication (ERC)/Joint Information Center (JIC) Plan for a Radiological Emergency NUREG/CR-7033, "Guidance on Developing Effective Radiological Risk Communication Messages: Effective Message Mapping and Risk Communication with the Public in Nuclear Plant Emergency Planning Zones" NRC Bulletin 2005-02, Emergency Preparedness and Response Actions for Security-Based Events NEI 06-04, Conducting a Hostile Action-Based Emergency Response Drill, Rev. 3 NRC Comment - Schrader 5.4.1

Consequence Analysis Methodology, states that the consequence assessment described in NEI 24-05, section 4.3.1, should use mean meteorology (or mean results of sampled meteorology). What is meant by mean meteorology? Also, in the parenthetical statement is mean results referring to the mean dose results calculated using sampled meteorological data (e.g., through a MACCS calculation), a set of meteorological data (e.g., wind speed, wind direction, stability class, etc.), or a set of atmospheric dispersion factors?

Team Response:

Given the technology-inclusive nature of NEI 24-05, the guidance may be used by plants with vastly different attributes (a single microreactor versus a plant with many larger reactors). The attributes of the plant will impact the level of detail necessary for their analyses, such a single calculations using mean inputs versus sampling of distributions.

In general, trying to avoid prescribing analysis details, given the variety of use cases

Current wording was meant to emphasize that the analysis utilizes mean or best-estimate values in comparison to 95th percentile or similar metrics.

NEI 24-05 text will be updated to clarify the intention NRC Comment - Hart Appendix B

The document should be clear on any differences in the methodology when used to support construction permit applications vs. operating license or combined license applications (e.g., selection of events).

Team Response:

Existing guidance available from NRC in DANU-ISG-2022-01 Appendix C:

As such the CP applicant should describe its EPZ sizing analysis methodology and the preliminary analysis results, including the radius of the plume exposure pathway EPZ.

The team is hesitant to further detail what EP information is necessary at each stage of licensing, as it is dependent on the strategy of the applicant

If applicants are seeking early resolution of EP topics, such as during CP review, they may need to note limitations of the analysis, such as PRA scope or the use of bounding assessments NRC Comment - Hart General

The document should provide guidance on needed documentation for the PEP EPZ size determination, including determination of the spectrum of events, consequence analyses, protective measure evaluation, and final determination of the PEP EPZ, and compliance with the regulatory criteria. It should be clear what information will be provided in the license application.

Team Response:

As discussed with preceding question, SAR would note EPZ methodology (or reference approach) and EPZ determination results, as would the emergency plan

The details of the EPZ determination analysis, including technical assessments and calculations, would not be included in the SAR or emergency plan, but would be available for NRC audit and inspection

Consistent with staffing analysis required by Appendix E

NEI 24-05 text will be updated to clarify the intention NRC Comment - Hart General

ML25175A055

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