ML23324A007

DG-4034 (RG 4.7 Rev 4) Response to Public Comments

ML23324A007
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Issue date:	02/22/2024
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DG-4034 RG 4.7, Rev 4
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Response to Public Comments on Draft Regulatory Guide (DG)-4034 General Site Suitability Criteria for Nuclear Power Stations, Proposed Revision 4 of Regulatory Guide (RG) 4.7 On October 19, 2023, the NRC published a notice in the Federal Register (88 FR 71777) that Draft Regulatory Guide, DG-4034, proposed Revision 4 of Regulatory Guide 4.7 was available for public comment. The Public Comment period ended on November 17, 2023. The NRC received comments from the individuals or organizations listed below. The NRC has combined the comments and NRC staff responses in the following table.

Comments were received from the following:

Kati R. Austgen for Nuclear Energy Institute (NEI) 1201 F Street NW, Suite 1100 Washinton, DC 20004 ADAMS Accession No. ML23326A031 Thomas Griffith Licensing Manger NuScale Power, LLC ADAMS Accession No. ML23326A030 Adam Stein, Ph.D.

Director, Nuclear Energy Innovation Breakthrough Institute ADAMS Accession No. ML23326A032 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution 1

NEI #1 GENERAL The draft continually refers to assessments in regions or discusses surveys without specifics.

Recommend using area of potential effect instead or adding it into areas where direction is given to perform an activity.

The NRC staff does not agree with this comment.

Regions and surveys are well-understood terms.

Replacing them with an ill-defined term such as area of potential effect would not improve clarity of the guidance.

No changes were made in response to this comment.

2 NEI #2 GENERAL Impacts appear to be consistently discussed in a negative manner.

Modify language where appropriate to acknowledge that there are beneficial/positive aspects to nuclear power plants. This is especially true in the area of socioeconomics where there are a number of benefits to a community from the The NRC staff does not agree with this comment.

Although there may be benefits to a community from the presence of a plant, the purpose of NRC guidance is to

2 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution presence of a plant.

provide clarity on the regulations under its jurisdiction, not highlight the benefits of nuclear power.

No changes were made in response to this comment.

3 NEI #3 B.

Discussion, Scope of Regulatory Guide 4.7, Page 4, 1st paragraph Reference to Electric Power Research Institute document No.

3002005435, Site Selection and Evaluation Criteria for New Nuclear Power Generation Facilities (Siting Guide), issued June 2015 is out of date. EPRI issued an update in November 2022.

Update refence on this page and in the REFERENCES list to EPRI document No.

3002023910, Advanced Nuclear Technology: Site Selection and Evaluation Criteria for New Nuclear Energy Generation Facilities (Siting Guide)2022 Revision, which can be found at https://www.epri.com/research/products/0000000030 02023910 The NRC staff agrees with this comment. The proposed update has been made.

3 NEI #4 B.

Discussion, Site Selection, Page 5, 1st paragraph, 1st sentence It is not necessary to state, Selecting a suitable site for a commercial nuclear power station may require a significant commitment of time and resources. Many small modular or advanced reactors may be selected for use in specific locations for very specific purposes. This statement could discourage new potential applicants.

Delete this sentence.

The NRC staff does not agree with this comment.

Experience indicates that the referenced statement is valid for small modular or advanced reactors. The NRC staff does not agree that including this statement would be a significant discouragement to potential new applicants.

No changes were made in response to this comment.

5 NEI #5 B.

Discussion, Population Considerati ons, Page 6, 1st paragraph, 2nd sentence The draft guide currently states, It also reduces potential doses and property damage in the event of a severe accident.

Given that the property damage in view is assumed to be associated with radiological contamination rather than direct physical damage that could occur from other types of events, and the Proposed, It also reduces potential doses and property damage from radiological contamination in the event of a severe accident that results in a significant release of radiological material to the environment.

The NRC staff agrees in part.

The fact that potential doses and property damage result from a radiological release is correct. However, this fact is clear from the context of the discussion and so no changes were made in response to this comment.

3 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution population considerations are also in view of a significant radiological release, recommend adding clarification as shown with redline insertion.

6 NEI #6 B.

Discussion, Population Considerati ons, Page 6, 1st paragraph, last sentence The draft guide currently states, The numerical values in this guide are generally consistent with past NRC practice and reflect consideration of severe accidents for large LWRs.

Per dispersion calculations developed and discussed in the NEI white paper (Advanced Reactor Population-Related Siting Considerations), the proposed 500 ppsm dose criterion of 2x the distance to 1 rem in 1 month for advanced reactors is quite conservative as compared to the current level of protection accepted for large LWR siting. Per NRC discussion during the October 27, 2023, public meeting, the advanced reactor dose criterion is significantly based on the desire to have the dose criterion below that associated with the Environmental Protection Agency (EPA) Protective Action Guides (PAGs) of 1 rem in 4 days and 2 rem in 1 year.

As described in our comments on Appendix A and in the NEI White Paper Advanced Reactor Population-Proposed, For large LWRs, tThe numerical values in this guide are generally consistent with past NRC practice and reflect consideration of severe accidents for large LWRs, as well as the demographic and geographic conditions of the United States. For advanced reactors, the numerical values are conservative with respect to past NRC practice and reflect consideration of EPA protective action guidelines.

The NRC staff disagrees with the comment.

See response to comment NEI #37.

No changes were made in response to this comment.

4 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution Related Siting Considerations, the basis for the proposed dose criterion should be reconsidered. At the very least, clarification on the basis of the currently proposed values for advanced reactors should be added as shown with redline/strikeout.

7 NEI #7 B. Discussion, Hydrology, Page 7, Water Availability Consider adding clarifying language, as shown with redline/strikeout.

Based on plant design (e.g., large light water reactor (LLWR), advanced reactor),

cConsumption of water may necessitate an evaluation of existing and future water uses in the area to ensure adequate water supply during droughts for both station operation and other water users (i.e., commercial nuclear power station requirements versus public water supply).

The NRC staff agrees with this comment. Text has been modified, but the parenthetical has not been added. This is not needed.

8 NEI #8 B. Discussion, Ecological Systems and Biota, Page 9, 2nd paragraph Consider adding clarifying language, as shown with redline/strikeout.

When the ecological sensitivity of a site within the area of potential effect under consideration cannot be established from existing information that would be considered representative of the current ecological system, more detailed studies, as discussed in RG 4.2, Rev. 3, might be necessary.

The NRC staff does not agree with this comment. See response to comment NEI #1. Additional proposed edit is not needed.

No changes were made in response to this comment.

9 NEI #9 B.

Discussion

Noise, Page 9 Consider adding clarifying language, as shown with redline/strikeout.

Based on location, nNoise levels at nuclear stations during both construction and operation could have undesirable impacts. For example, cooling towers (if present), turbines, and transformers contribute to the noise during station operation, and such noise could have varying levels of environmental impact, depending on the site.

The NRC staff agrees with this comment. Text has been modified as proposed.

10 NEI #10 C. Staff Regulatory

Guidance, Page 13, Section It may be useful for an evaluation of the water requirements for the ultimate heat sink to consider a minimum 30-year weather record, but this should not be strictly An evaluation of the water requirements for the ultimate heat sink should consider, if available, a minimum 30-year weather record and should follow the guidance provided in RG 1.27.

The NRC staff agrees with this comment. Text has been modified as proposed.

5 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution 1.2.1.3, 2nd paragraph necessary. In any case, the NRC staff expect the applicability of data to be substantiated. Consider clarification as shown with redline insertion.

11 NEI #11 C. Staff Regulatory

Guidance, Page 16, Section 1.3 Suggest an insertion after the 1st paragraph to provide distinction regarding unique features of advanced reactors.

Some reactor plant designs with relatively small cores, passive safety features, or other design features, which are anticipated to result in smaller postulated accident releases and associated radiological doses, may identify the potential for the exclusion area boundary (EAB) to be smaller than historically determined for LLWRs.

The NRC staff agrees in part.

The suggested text points out that some reactor designs may support smaller EABs and LPZs than have been historically established for large light-water reactors (LLWRs). However, the guidance does not provide historical sizes or expectations for the boundaries and so the discussion of potentially smaller boundaries is not needed. The background discussions in Appendix A adequately address the topics and no changes were made to this section.

12 NEI #12 C. Staff Regulatory

Guidance, Page 17, Section 1.3.3 Suggest an insertion after the 1st paragraph to provide distinction regarding unique features of advanced reactors.

Some reactor plant designs with relatively small cores, passive safety features, or other design features, which are anticipated to result in smaller postulated accident releases and associated radiological doses, may identify the potential for the exclusion area boundary (EAB) to be smaller than historically determined for LLWRs.

The staff agrees in part.

See response to comment NEI #11.

No changes were made in response to this comment.

13 NEI #13 C. Staff Regulatory

Guidance, Page 18, Section 1.4.3, 1st paragraph The draft guide misstates the content of 10 CFR 100.21(h) as follows (emphasis added), As stated in 10 CFR 100.21(h),

reactors are to be located away from very densely populated centers; areas of low population density are generally preferred. The rule text states, reactor sites should.

Correct the statement to reflect the rule text, As stated in 10 CFR 100.21(h), reactors should be located away The staff agrees with the comment.

The sentence has been changed to use the wording from 10 CFR 100.21(h) instead of paraphrasing. The revised sentence reads:

As stated in 10 CFR 100.21(h), reactor sites should be located away from very densely populated centers.

Areas of low population density are, generally, preferred.

6 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution 14 NEI #14 C. Staff Regulatory

Guidance, Page 18, Section 1.4.3, 1st paragraph Insert clarifying text as shown with redline insertion.

...for a site located away from a very densely populated center but not in an area of low density, acceptability will be determined after consideration of safety, environmental, economic, and other factors. Other factors may include reactor plant designs with relatively small cores, passive safety features, or other design features, which are anticipated to result in smaller postulated accident releases and associated radiological doses.

The staff agrees in part.

The consideration of design attributes that could influence the area in which population density is assessed is described in Appendix A. No changes were made to this section, which mentions the factors identified in 10 CFR 100.21(h) for potentially siting any reactor in an area other than one of low population density.

15 NEI #15 C. Staff Regulatory

Guidance, Page 18, Section 1.4.3, 2nd paragraph The draft guide currently states, The numerical values in this guide are generally consistent with past NRC practice and reflect consideration of severe accidents for large LWRs.

Per dispersion calculations developed and discussed in the NEI white paper (Advanced Reactor Population-Related Siting Considerations), the proposed 500 ppsm dose criterion of 2x the distance to 1 rem in 1 month for advanced reactors is quite conservative as compared to the current level of protection accepted for large LWR siting. Per NRC discussion during the October 27, 2023, public meeting, the advanced reactor dose criterion is significantly based on the desire to have the dose criterion below that associated Proposed, For large LWRs, tThe numerical values in this guide are generally consistent with past NRC practice and reflect consideration of severe accidents for large LWRs, as well as the demographic and geographic conditions of the United States. For advanced reactors, the numerical values are conservative with respect to past NRC practice and reflect consideration of EPA protective action guidelines.

The NRC staff disagrees with the comment.

See response to comments NEI #6 and NEI #37.

No changes were made in response to this comment.

7 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution with the Environmental Protection Agency (EPA) Protective Action Guides (PAGs) of 1 rem in 4 days and 2 rem in 1 year.

As described in our comments on Appendix A and in the NEI White Paper Advanced Reactor Population-Related Siting Considerations, the basis for the proposed dose criterion should be reconsidered. At the very least, clarification on the basis of the currently proposed values for advanced reactors should be added as shown with redline/strikeout.

16 NEI #16 C. Staff Regulatory

Guidance, Page 19, Section 1.4.3, 1st full paragraph Insert clarifying text as shown with redline insertion.

Other factors, such as safety, environmental, or economic characteristics, may render the site with higher population density acceptable including reactor plant designs with relatively small cores, passive safety features, or other design features, which are anticipated to result in smaller postulated accident releases and associated radiological doses.

The staff agrees in part.

The consideration of design attributes that could influence the area in which population density is assessed is described in Appendix A. No changes were made to this section, which mentions the factors identified in 10 CFR 100.21(h) for potentially siting any reactor in an area other than one of low population density.

17 NEI #17 C. Staff Regulatory

Guidance, Page 20, Section 1.5.3 Add clarifying language to reflect the forthcoming final rule, Emergency Preparedness for Small Modular Reactors and Other New Technologies, as shown with redline insertion.

Insert after 3rd paragraph:

As a note, some reactor plant designs with relatively small cores, passive safety features, or other design features, which are anticipated to result in smaller postulated accident releases, may follow alternative emergency preparedness requirements for small modular reactors and other new technologies per 10 CFR 50.160 which may The staff agrees with the comment in part given the publication of the final rule on November 16, 2023 (88 FR 80050).

The staff has added the following text to the end of Section 1.5.3:

The NRC incorporated a technology-inclusive and consequence-oriented approach to emergency planning into the regulations by adding 10 CFR 50.160, Emergency preparedness for small modular reactors,

8 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution reduce the size of their emergency planning zone.

non-light-water reactors, and non-power production or utilization facilities. The requirements include a scalable emergency planning zone around a facility. Applicants and licensees for small modular reactors (SMRs) and other new technologies can use the rule in developing a performance-based emergency preparedness program as an alternative to the radiological emergency planning requirements in 10 CFR 50.47 and Appendix E to 10 CFR Part 50. Guidance for using the rule is provided in RG 1.242, Performance-Based Emergency Preparedness for Small Modular Reactors, Non-Light-Water Reactors, and Non-Power Production or Utilization Facilities.

18 NEI #18 C. Staff Regulatory

Guidance, Page 21, Section 1.5.3, final paragraph, final sentence Consider adding clarifying language, as shown with redline insertion.

The Clinch River FSER highlights that emergency plans for one or more reactors should be considered for green-field, or retired fossil fuel plant, siting of nuclear power plants.

The NRC staff agrees with this comment in part. The text has been edited to remove green-field so that the sentence is not limiting to either green-field or retired fossil fuel sites.

19 NEI #19 C. Staff Regulatory

Guidance, Page 21, last paragraph before Security section.

Add clarifying text after the last paragraph in Section 1.5.3, as shown with redline insertion.

As a note, some reactor plant designs with relatively small cores, passive safety features, or other design features, which are anticipated to result in smaller postulated accident releases, may follow alternative emergency preparedness requirements for small modular reactors and other new technologies per 10 CFR 50.160 which may reduce the size of their emergency planning zone.

NRC staff agrees with this comment in part. The text added in response to NEI comment #17 addresses this comment.

20 NEI #20 C. Staff Regulatory

Guidance, Page 25, Section Consider adding clarifying language, as shown with redline insertion.

Both the frequency and duration of periods of low flow or low water level should be determined from a reasonable and representative period of time based on the historical record and, if the cooling water is to The NRC staff disagrees with this comment. Proposed edit is not needed. The proposed edit would only add ambiguity to an otherwise clear statement since reasonable and representative are subjective.

9 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution 1.7.2.3, 1st paragraph, 2nd sentence be drawn from impoundments, for projected operating practices.

No changes were made in response to this comment.

21 NEI #21 C. Staff Regulatory

Guidance, Page 26, Section 1.8.3, bottom paragraph, 1st sentence Consider adding clarifying language, as shown with redline/strikeout.

The acceptability of a site depends on establishing that (1) an postulated accident at a nearby industrial, military, or transportation facility will not result in radiological consequences that exceed the dose specified in 10 CFR 50.34, or (2) such an postulated accident poses no undue risk because the annual frequency of its occurring is sufficiently low (less than about 1x10-7 per year).

The NRC staff agrees with this comment. Text has been modified as proposed.

22 NEI #22 C. Staff Regulatory

Guidance, Section C.2, Page 27-48 Numbering is off in Section C.2, e.g., subsection numbering goes from 2 to 2.1.1. Later subsections often skip 2.X.1 or 2.X.X.1, e.g.

2.1.3 is followed by 2.1.3.2 on Page

29.

Generic editorial correction to check section numbers and sequencing.

The NRC staff agrees with this comment. The subsection numbering has been corrected.

23 NEI #23 C. Staff Regulatory

Guidance, Page 29, Section 2.1.3.4, 1st paragraph Add clarifying language, as shown with redline/strikeout.

Depending on the plants cooling system design, wWater and water vapor released to the atmosphere The NRC staff agrees with this comment. Suggested edit has been made.

24 NEI #24 C. Staff Regulatory

Guidance, Page 30, Section 2.1.4.4, 2nd paragraph Add clarifying language, as shown with redline/strikeout.

Depending on the plants cooling system design, cConcentrations of chemicals, dissolved solids, and suspended solids in cooling tower drift could affect terrestrial biota within the area of potential effect and result in unacceptable damage to vegetation and other resources.

The NRC staff agrees with this comment in part. The first edit has been made. The second edit regarding area of potential effect has not (see response to comment NEI #1).

10 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution 25 NEI #25 C. Staff Regulatory

Guidance, Page 32, Section 2.2.2.4, 1st paragraph Add clarifying language, as shown with redline/strikeout.

The potential impacts of commercial nuclear power stations on water quality would are likely to be acceptable if they satisfy effluent limitations, water quality criteria for receiving waters, and other requirements under the CWA.

The applicant should also identify any other relevant state, local, or federal regulations current at the time when it is considering sites.

The NRC staff agrees with this comment in part. The first proposed edit was not adopted. The 2nd proposed edit has been made.

26 NEI #26 C. Staff Regulatory

Guidance, Page 32, Section 2.2.2.4, 5th paragraph Modify text for clarity, as shown with redline/strikeout.

Although effluent discharges are governed under the authority of the Federal Water Pollution Control Act (FWPCA) to ensure that established existing water quality standards are maintained to be protective of the public and environment, wWhere station construction or operation could degrade water quality to the detriment of other users as a result of waters being listed as impaired under Section 303(d) of the CWA, more detailed analyses and evaluation of water quality may be necessary.

The NRC staff disagrees with this comment. The proposed edit changes the meaning of the original statement to imply that additional analysis may be necessary only if those waters are already listed as impaired, which is not correct.

No changes were made in response to this comment.

27 NEI #27 C. Staff Regulatory

Guidance, Page 34, Section 2.2.3.4, 1st paragraph Modify text for clarity, as shown with redline/strikeout.

If applicable, potential sources of cooling water should also be screened to determine if the proposed plant cooling water system meets all three criteria of the CWA 316(b) intake flow limitations specified in 40 CFR 125.81: (1) is a point source that uses or proposes to use a cooling water intake structure; (2) has at least one cooling water intake structure that uses at least 25 percent of the water it withdraws for cooling purposes based on an average monthly measurement; and (3) has a design intake flow greater than two (2) million gallons per day. by their capacity to meet intake flow limitations specified in CWA section 316(b), as implemented by the EPA in 40 CFR Parts 9, 122, 123, 124, and 125. CWA section 316(b) identifies criteria based NOTE: This comment references the 7th paragraph of Section 2.2.3.4, not the 1st paragraph.

The NRC staff agrees with this comment in part. It is useful to provide the intake flow limitations of 40 CFR 125, but its not appropriate to delete references to the other regulations. The paragraph has been edited to read as:

CWA section 316(b) identifies criteria based on type of water body in order to reduce environmental impact. It is typically administered by State programs. If applicable, potential sources of cooling water should also be screened by their capacity to meet intake flow limitations specified in CWA section 316(b), as implemented by the EPA in 40 CFR Parts 9, 122, 123, 124, and 125.

11 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution on type of water body in order to reduce environmental impact. It is typically administered by State programs.

Specifically, 40 CFR 125 Subpart I provides requirements applicable to cooling water intake structures for new facilities under CWA section 316(b).

28 NEI #28 C. Staff Regulatory

Guidance, Page 34, Section 2.2.3.4, 2nd paragraph Consider adding clarifying language, as shown with redline insertion.

The following are examples of potential environmental effects of station construction and operation that should be assessed and which the applicant can reference per NUREG-1437, Revision 1, when addressing operational impacts, as applicable:

NOTE: This comment references the 8th paragraph of Section 2.2.3.4, not the 2nd paragraph.

The NRC staff does not agree with this comment.

NUREG-1437 applies to license renewal of nuclear power plants.

No changes were made in response to this comment.

29 NEI #29 C. Staff Regulatory

Guidance, Page 36, Section 2.3, 1st paragraph, 2nd sentence Consider adding clarifying language, as shown with redline insertion.

The ecological systems and biota at potential sites and their environs within the area of potential effect should be sufficiently well known The NRC staff does not agree with this comment. See response to comment NEI #1.

No changes were made in response to this comment.

30 NEI #30 C. Staff Regulatory

Guidance, Page 41, Section 2.3.5 Consider adding clarifying language, as shown with redline insertion.

To limit the potential for entrapment of aquatic organisms by intake or discharge structures, evaluations of potential sites should consider of the entrainment, impingement, and heat shock requirements of applicable Federal, State and local regulations.

The NRC staff agrees with this comment. The proposed edit has been made.

31 NEI #31 C. Staff Regulatory Guidance, top of Page 43, Section 2.4.2 Consider adding clarifying language, as shown with redline insertion.

Locating a commercial nuclear power station adjacent to lands devoted to public use when present might be unacceptable to Federal, State, or local jurisdictions.

The NRC staff disagrees with this comment. The proposed edit would make the statement unclear. For example, it is not clear if when present refers to the power station, the adjacent land, or the public use.

No changes were made in response to this comment.

32 NEI #32 C. Staff Regulatory

Guidance, Page 43, Consider adding clarifying language, as shown with redline insertion.

For example, nuclear power station siting in areas uniquely suited for growing specialty crops, if present, may be considered a type of land The NRC staff disagrees with this comment. The presence of the crops at a particular point in time is not the issue.

12 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution Section 2.4.2.4, 3rd paragraph conversion involving unacceptable economic dislocation.

No changes were made in response to this comment.

33 NEI #33 C. Staff Regulatory

Guidance, Page 44, Section 2.4.3 Consider adding clarifying language, as shown with redline/strikeout.

Where applicable, sSome areas might be unsuitable for siting a nuclear power station because of public interest in reserving land for future to public scenic, recreational, or cultural use.

The NRC staff disagrees with this comment. The phrase where applicable does not add anything to the statement. It degrades clarity because applicability is not defined or described.

No changes were made in response to this comment.

34 NEI #34 C. Staff Regulatory

Guidance, Page 48, Section 2.6 Consider adding clarifying language, as shown with redline/strikeout.

Unless adequate mitigation measures can be implemented to offset impacts, tThe use of a proposed site that could disproportionately affect minority or low-income communities should be avoided as sites for nuclear power stations.

The NRC staff disagrees with this comment. Proposed edit is not needed. The original sentence is simply a statement of the issue and the proposed edit changes the meaning significantly by introducing the topic of mitigation measures, which is beyond the scope of this RG.

No changes were made in response to this comment.

35 NEI #35 C. Staff Regulatory

Guidance, Section C.3, Page 49 The draft guidance only references use of a Limited Work Authorization in support of a combined license (COL). Per 10 CFR 50.10(d), limited work authorization may be requested in support of a combined license application or construction permit (CP) application or by an applicant or holder of an early site permit (ESP).

Please clarify discussion to include CP and ESP, in addition to COL.

The NRC staff agrees with this comment. The text has been changed to include CPs and ESPs.

36 NEI #36 C. Staff Regulatory

Guidance, Page 50, Section 3.3, bulleted list Consider adding clarifying language, as shown in redline/strikeout.

• Identify the geographic area of potential effect and time period to be considered in evaluating the cumulative impact. Collect information on the relevant impacts of the proposed action within the identified geographic area of potential effect.

• Identify other past, present, or reasonably foreseeable actions that would contribute to the The NRC staff disagrees with this comment. See response to comment NEI #1.

No changes were made in response to this comment.

13 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution cumulative impact within the area of potential effect when added to the proposed action.

• Determine the cumulative impact on the resource area within the area of potential effect.

• Identify plans or actions (if any) to avoid, minimize, or mitigate adverse cumulative impacts within the area of potential effect.

37 NEI #37 Appendix A The NRCs proposed criterion associated with very low frequency events, twice the distance of 1 rem in 30 days is more than a factor of five times more conservative compared to previous large LWR licensing when calculated using best estimate consequence methods. That is, 1 rem is approximately five times lower than the level of protection currently accepted for large LWRs using a population density distance of 20 miles. Doubling the distance to 1 rem in 30 days for advanced reactors will further lower the dose, resulting in more than a factor of five conservatism given the decrease in dose with distance, e.g., 4.7 rem/0.36 rem =

a factor of 13.

The NRC proposed dose criterion results in undue burden on the owner of an advanced reactor with population related siting considerations unnecessarily limiting allowable sites when The NRC should revise the dose criterion for the population density distance (PDD) of advanced reactors, even if this requires the Commissions approval. We recommend that the dose criterion for the PDD of advanced reactors be established as 5 rem in 30 days (rather than the currently proposed PDD of 2x the distance of 1 rem in 30 days). To be consistent with the current level of protection accepted by the NRC, this dose limit should be based upon implementation of a performance-based approach to advanced reactor siting with required consequence analyses performed using best estimate approaches rather than conservative approaches.

The staff disagrees with the comment.

The criteria in DG-4034 reflects the history of the NRCs policy of siting reactors away from population centers, many interactions with stakeholders and the Advisory Committee on Reactor Safeguards during the development of SECY-20-0045, Population Related Siting Considerations for Advanced Reactors (ML19143A194), and the Commissions direction in the related staff requirements memorandum.

The existing guidance evolved based on quantitative information from various studies performed over many years as well as qualitative factors for how population density should be considered in the siting of nuclear power plants. The consideration of population density dates to the period when the licensing of nuclear plants did not explicitly consider the risks from severe or Class 9 accidents, but the NRC recognized the need to consider such accidents in evaluating alternative sites for proposed nuclear plants (see SECY-78-137 for early history). The existing guidance, which has evolved over decades, is not based on specific projected doses at specific distances nor on a quantifiable role for limiting population densities near nuclear plants in terms of contributing to defense in depth or limiting societal risks posed by potential accidents. The comment is largely based on (1) an attempt to reverse engineer a dose-

14 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution compared to the accepted level of protection for existing plants. It is also not consistent with the NRCs Advanced Reactor Policy Statement that expects at least the same level of protection.

equivalent criterion for the distance in the existing guidance using the calculated consequences of a selected severe accident for a LLWR at a distance of 20 miles from the damaged reactor and (2) using the resultant value as a representation of the existing guidance for LLWRs for comparison to the alternative approach in Appendix A of DG-4034. However, as explained in the 10 CFR Part 100 final rule and related disposition of the petition for rulemaking PRM-50-20 (61 FR 65175, Dec. 11, 1996) the basis for a distance of 20 miles in the existing guidance included quantitative and qualitative assessments of both event frequencies and consequences.

The optional alternative approach proposed in Appendix A of DG-4034 includes an increased use of quantitative criteria for determining the distance out to which population density should be assessed when siting new nuclear power plants. The proposed criteria were developed considering the current understanding and ability to model severe accidents, the ability to assess overall risks in terms of both consequences and frequency of severe accidents, and regulatory requirements to assess and, when appropriate, incorporate design features to prevent or mitigate severe accidents in new plants. As explained in Appendix A of DG-4034, the criteria were developed in part to ensure that the population density near future nuclear plants was aligned with the potential risks and the possible use of immediate or intermediate protective actions (e.g.,

evacuation or relocation) to limit the consequences of an accident. In this way, the optional alternative approach in Appendix A of DG-4034 provides a functional performance standard that is an integral part of a technology-inclusive, risk-informed, and performance-based approach. The fixed distance value of 20 miles for

15 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution assessing population density in section C.1.4 of the RG was established considering both qualitative and quantitative factors informed by generic studies of potential severe accidents at a LLWR.

The comment suggests criteria for assessing population density out to a distance where analysis results estimate 5 rem over the month following a severe accident. As explained above, the staff disagrees with the derivation of the suggested criteria and the claim of equivalency between the commenters representation of existing guidance developed for the operating fleet of nuclear plants and the optional alternative approaches for advanced reactors in Appendix A. Furthermore, the staff does not believe that the suggested criteria in the comment aligns with the purpose for considering population density in Appendix A, which includes supporting the possible use of immediate or intermediate protective actions to limit the consequences of an accident. As mentioned under Option 3 in Enclosure 1, Options and Recommendation for Population-Related Siting Considerations for Advanced Reactors (ML19262H152) of SECY-20-0045 related to the development of the criteria incorporated into Appendix A, the EPA Protective Action Guide (PAG) Manual guidelines for the relocation of the public following a potential nuclear accident are 2 rem projected dose in the first year and 0.5 rem per year projected dose in the second and subsequent years. The comment and related white paper do not explain how the suggested criteria of 5 rem over the month following an accident relates to the consideration of relocating populations following an accident at a nuclear plant proposing to use the alternative criteria in Appendix A.

16 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution No changes to the guidance were made as a result of this comment.

38 NEI #38 Appendix A Related to the consideration of uncertainty, per dispersion calculations developed and discussed in the NEI white paper, Advanced Reactor Population-Related Siting Considerations, the proposed 500 ppsm dose criterion of 2x the distance to 1 rem in 30 days for advanced reactors is quite conservative as compared to previous large LWR licensing when calculated using best estimate consequence methods. The conservatism based on best-estimate calculations would be more than a factor of five. It is also noted that the LWR base case would have uncertainty associated with it, such that the margin could be even more. While consideration of uncertainty is important, the margin in the proposed population density criterion for advanced reactors as compared to historical large LWR siting should limit the need for extensive uncertainty assessment.

Provide for simplified assessment of uncertainty as described in NEI white paper, Advanced Reactor Population-Related Siting Considerations.

The NRC staff agrees in part with this comment, insofar as there are flexibilities and tradeoffs in how a prospective applicant addresses uncertainties.

As explained in the response to comment NEI #37, the staff believes that there are fundamental issues with attempting to directly compare the historical guidance in previous revisions to RG 4.7 to the criteria in Appendix A for determining a distance out to which population density is assessed. The staff does not agree that excessive conservatisms have been introduced through the criteria in Appendix A that would justify other suggested changes in the comments. However, the guidance related to uncertainty assessments in Appendix A provides flexibility in statements such as the following in Section A-3:

Acceptable analyses, in general, can be thought of along a continuum of realism and rigor of the analysis, ranging from bounding assumptions and simple modeling to a high level of realism and detail.

The guidance further expands this discussion in Section A-3.3(c) as follows:

A simpler design with relatively coarse assumptions might require less accounting for uncertainty at the cost of design margin (e.g., through the use of more conservative assumptions). Conversely, a finely refined analysis can be used to capture design margin (with an associated lower margin between the analysis and acceptance criteria) at the cost of quantifying the uncertainty and justifying how the analysis meets the applicable NRC requirements...

17 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution No changes were made in response to this comment.

39 NEI #39 Appendix A The draft guidance would benefit from inclusion of examples and graphs of various siting scenarios (such as those provided in the SECY 20-0045 Enclosure and the referenced ORNL report) but with real numbers rather than variables to provide and promote greater clarity, understanding, and transparency such that potential siting scenarios for advanced reactors are more readily apparent to stakeholders, including members of the public.

NRC should consider inclusion of examples and graphs in the guidance.

The NRC staff agrees in part with the comment.

While examples and graphics are useful in promoting understanding of guidance documents, the staff believes that references in Appendix A to the cited background material in SECY-20-0045 and ORNL/TM-2019/1197, Advanced Reactor Siting, Policy Considerations, adequately serve that purpose.

No changes were made in response to this comment.

40 NEI #40 Appendix A The following discussion provided by the NRC in the Enclosure to SECY 20-0045, Furthermore, while NRC regulations do restrict the siting of plants relative to a population center containing more than about 25,000 residents, the staffs interactions with stakeholders have not identified any near-term proposals to site reactors within a population center exceeding 25,000 residents, and no changes to the relevant regulatory criteria and associated guidance are being proposed at this time, appears to be a little short-sighted and not consistent with the clean sheet of paper approach advocated for in developing a risk-informed, performance-based regulatory NRC should ensure guidance is more widely applicable for future advanced reactor applications, and not just consider feedback from stakeholder engagement on near-term needs for this guidance.

The NRC staff disagrees with the comment.

When assessing the potential benefits of undertaking a rulemaking, which would be required to change the use of densely populated center within the definition of population center distance in 10 CFR 100.3, the NRC engages stakeholders to determine the need for and the costs and benefits associated with the regulatory action.

Given the feedback from stakeholders at the time the staff prepared SECY-20-0045, the decision was made to pursue changes to those matters addressable by revising guidance documents. The staff cannot revise regulatory requirements through guidance documents and so RG 4.7 continues to cite the requirements for reactors to be some distance from the boundary of population centers of approximately 25,000 persons.

No changes were made in response to this comment.

18 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution framework for advanced reactors.

One would expect a more far-reaching vision to be embraced as part of this regulatory framework development.

41 NEI #41 Appendix A The draft guidance should make it clear that best estimate assumptions for weather, wind direction and shielding may be used in offsite consequence analyses to inform the alternative population-related siting considerations for advanced reactors.

Specify in Appendix A that best estimate assumptions for weather, wind direction and shielding may be used in offsite consequence analyses to inform the alternative population-related siting considerations for advanced reactors.

The NRC staff agrees in part.

As discussed under comment NEI #38 on addressing uncertainties, Appendix A explains the flexibility of analytical approaches as follows:

Acceptable analyses, in general, can be thought of along a continuum of realism and rigor of the analysis, ranging from bounding assumptions and simple modeling to a high level of realism and detail.

The suggested wording on best estimate assumptions for weather, wind direction and shielding in offsite consequence analyses fits within the stated continuum.

No changes were made in response to this comment.

42 NEI #42 Appendix A Information that is equally applicable across the approaches described in Appendix A, e.g., the limiting population-related siting consideration may be population center distance instead of population density distance, could be consolidated into one section to minimize repetition and clarify the common performance-based foundation for all approaches.

Consider organizing Appendix A to minimize repetition of information that is equally applicable/available to each approach.

The NRC staff acknowledges the comment; but considers the existing structure of Appendix A to provide sufficient clarity.

No changes were made in response to this comment.

43 NEI #43 Section A-1, Background, Section A-3.1, The language in 10 CFR 100.21(h) sets a flexible regulatory requirement (i.e., Reactor sites Ensure the language of 10 CFR 100.21(h) is captured accurately and continue the use of flexible language, e.g., should, when providing guidance The staff agrees with this comment.

The body of Revision 4 to RG 4.7 and Appendix A refer to 10 CFR 100.21(h) and the related flexibility to

19 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution Section A-3.2 should be located away from very densely populated centers. Areas of low population density are, generally, preferred.) rather than a strict regulatory limit. (emphasis added)

The guidance in Appendix A seems to impose the 500 ppsm guideline as a limit rather than as guidance for meeting a flexible regulatory requirement.

B. Discussion, Population Considerations, on Page 6 does state, The numerical values in this guide are generally consistent with past NRC practice and reflect consideration of severe accidents for large LWRs, as well as the demographic and geographic conditions of the United States.

Additionally, Sec. 1.4.3 continues the flexible language of preferably and should when introducing the 500 persons per square mile.

However, the approach for advanced reactors provided in the draft guidance of Appendix A does not consistently use flexible language. See for example, A-3.2, 1st paragraph, for which population density is not to throughout the RG, including Appendix A, if 500 ppsm is indeed not meant to be a regulatory limit.

consider safety, environmental, economic, or other factors when assessing the possible siting of a nuclear reactor in an area not having a low population density.

As described in comment NEI #13, the staff changed the wording in DG-4034 where the rule language was paraphrased to the exact wording in 10 CFR 100.21(h).

See comment NEI #13 for the revisions to the guidance.

To alleviate the perception that Appendix A seems to impose the 500 ppsm density as a limit, the discussion in Appendix A was changed to only refer to the area where the population density is evaluated. For instance, the text in section A 3.1, 2nd paragraph was modified to read: "Applicants using a methodology like that described in RG 1.233 would use the licensing-basis events categorized as design-basis events (DBEs) and beyond-design-basis events (BDBEs) to estimate potential offsite doses for use in determining the distance out to which the population considerations are assessed in accordance with Section C.1.4 of this RG."

20 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution exceed 500 ppsm.

See NRC precedent in Florida Power & Light Co. (Turkey Point Units 6 and 7), Commission Memorandum and Order CLI 01, Docket Nos. 52-040-COL &

52-041-COL (Apr. 5, 2018), at 29-32 (ML18095A117), including The Staff noted that the highest population density at any radial distance out to 20 miles for the Turkey Point site is comparable to that of previously licensed sites.

Id. For example, the Limerick site had a density of 789 persons per square mile at 5 miles; the Zion site had a density of 668 persons per square mile at 10 miles; and the Connecticut Yankee site had a density of 716 persons per square mile at 20 miles. Id. (citing Metropolitan Siting - A Historical Perspective, NUREG-0478 (Oct.

1978), tbl.I (ML12187A192)).

44 NEI #44 Section A-3, Page A-3, bulleted list The introduction to the bulleted list states the NRC staff provides the following list of key actions for siting analyses that should be considered regardless of the approach taken:

In the NRC public meeting October 27, 2023, slide 7 for Non-LWR under LMP indicated that risk metrics under LMP are based Proposed new bullet:

Perform an atmospheric dispersion analysis (i.e.,

dose assessment), based on mean dose.

The NRC staff agrees in part.

While not disputing the comment, the staff believes that the details of analytical approaches for the LMP methodology are adequately addressed in guidance such as RG 1.233 and RG 1.247. Future revisions of these guidance documents may address lessons learned from the first uses of the LMP and potential siting of new reactors based on the analyses under the LMP methodology. For LWRs and non-LWRs using more traditional approaches, Appendix A explains the

21 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution on mean frequency and mean consequence, with decision making informed by other factors such as uncertainty. In public discussion, the NRC confirmed that while EAB and LPZ dose calculations are performed with conservative inputs for atmospheric dispersion analysis, the population density (i.e., 500 ppsm) atmospheric dispersion calculations may be performed in a best estimate manner consistent with LMP. The public noted that the same best estimate dispersion analysis should seem to be applicable to the other two approaches of LWR under traditional approach and the non-LWR under traditional approach.

One clear way to indicate this is to include an additional bullet in this list regarding the atmospheric dispersion analysis.

flexibility of analytical approaches as follows:

Acceptable analyses, in general, can be thought of along a continuum of realism and rigor of the analysis, ranging from bounding assumptions and simple modeling to a high level of realism and detail.

The suggested wording on atmospheric dispersion analysis and related input assumptions fits within the stated continuum. An applicant could justify use of either conservative assumptions or mean values in the atmospheric dispersion analysis depending on their overall approach to demonstrating that adequate defense in depth is provided for a particular reactor design and site.

No changes were made in response to this comment.

45 NEI #45 Section A-3.1, Page A-4, 2nd paragraph Section A-3.2, Page A-5, 2nd paragraph Section A-3.1 Regulatory Guide 1.233 Approach (non-LWRs) second paragraph includes the following:

The calculation of offsite doses should be in accordance with NRC-accepted methodologies, including associated computer models for the plant response to an accident, the performance of various barriers to the release of Proposed additional sentence:

The atmospheric dispersion analysis (i.e., dose assessment) may be based on best estimate inputs and assumptions, mean dose and consideration of uncertainties.

Include a footnote with some example best estimate inputs / assumptions, such as:

Examples of best estimate inputs and assumptions associated with the atmospheric dispersion The NRC staff agrees in part.

As discussed under comment NEI #38 on addressing uncertainties, Appendix A explains the flexibility of analytical approaches as follows:

Acceptable analyses, in general, can be thought of along a continuum of realism and rigor of the analysis, ranging from bounding assumptions and simple modeling to a high level of realism and detail.

22 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution Section A-3.3, Page A-6, 2nd paragraph radioactive materials, and the atmospheric dispersion of any released materials to the area surrounding the plant.

In the NRC public meeting October 27, 2023, slide 7 for Non-LWR under LMP indicated that risk metrics under LMP are based on mean frequency and mean consequence, with decision making informed by other factors such as uncertainty. In public discussion, the NRC confirmed that while EAB and LPZ dose calculations are performed with conservative inputs for atmospheric dispersion analysis, the population density (i.e., 500 ppsm) atmospheric dispersion calculations may be performed in a best estimate manner consistent with LMP. This should be clarified.

Further, the public noted that the same best estimate dispersion analysis should be applicable to the other two approaches of LWR under traditional approach and the non-LWR under traditional approach. Use of best estimate /

mean dispersion analysis for all three approaches (i.e., A-3.1, A-3.2, A-3.3) makes sense in view of an overall performance-based approach and, as demonstrated in the NEI white paper on Advance modeling include average weather conditions, average dose of varied wind direction, credit for normal shielding (e.g., public in their homes at night.)

The suggested wording on atmospheric dispersion analysis and related input assumptions fits within the stated continuum.

No changes were made in response to this comment.

23 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution Reactor Population-Related Siting Considerations, reduces undue conservatism as compared to previous large LWR siting criterion.

One clear way to indicate this is to include additional text in the corresponding paragraph for each section regarding the acceptability of mean/best estimate atmospheric dispersion analysis.

46 NEI #46 A-3.1, Regulatory Guide 1.233 Approach (non-LWRs),

Page A-4 to A-5 The last sentence of this section states, "However, an advanced reactor with estimated doses below 1 rem at the site boundary over the month following the assumed postulated accident could be sited within towns with populations of no more than approximately 25,000 residents." This is potentially a very conservative interpretation of the regulations that may counteract efforts to provide technology-inclusive, risk-informed, and performance-based guidance. The safety profiles of some advanced reactors, e.g., micro-reactors, will be analogous to research and test reactors. Further, there may be defense-in-defense features associated with advanced reactors that outweigh the benefits of establishing additional defense-in-depth via locating reactors away from population centers and/or there may be performance Although they are their own license class, the precedent set by research and test reactor siting should be considered for consistency, i.e., the safety profile of an advanced reactor may support siting within towns with a population greater than approximately 25,000 residents.

The NRC staff disagrees with the comment.

As discussed under comment NEI #40, the staff cannot revise regulatory requirements through guidance documents and so RG 4.7 continues to cite the requirements for nuclear power reactors to be some distance from the boundary of population centers of approximately 25,000 persons.

No changes were made in response to this comment.

24 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution characteristics that could demonstrate safety in even closer proximity to population centers.

47 NEI #47 A-3.2, Regulatory Guide 1.183 Plus Severe Accidents Approach (LWRs), Page A-5 The last sentence of this section states, "However, an advanced reactor with estimated doses below 1 rem at the site boundary over the month following the assumed postulated accident could be sited within towns with populations of no more than approximately 25,000 residents."

This is potentially a very conservative interpretation of the regulations that may counteract efforts to provide technology-inclusive, risk-informed, and performance-based guidance.

The safety profiles of some advanced reactors, e.g., micro-reactors, will be analogous to research and test reactors.

Further, there may be defense-in-defense features associated with advanced reactors that outweigh the benefits of establishing additional defense-in-depth via locating reactors away from population centers and/or there may be performance characteristics that could demonstrate safety in even closer proximity to population centers.

Although they are their own license class, the precedent set by research and test reactor siting should be considered for consistency, i.e., the safety profile of an advanced reactor may support siting within towns with a population greater than approximately 25,000 residents.

The NRC staff disagrees with the comment.

As discussed under comment NEI #40, the staff cannot revise regulatory requirements through guidance documents and so RG 4.7 continues to cite the requirements for nuclear power reactors to be some distance from the boundary of population centers of approximately 25,000 persons.

No changes were made in response to this comment.

25 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution 48 NEI #48 A-3.3, For Non-LWRs Not Using RG 1.233 and Using Traditional Analysis of a Containment-Type Barrier, Page A-6, 2nd paragraph The last sentence of this section states, "However, an advanced reactor with estimated doses below 1 rem at the site boundary over the month following the assumed postulated accident could be sited within towns with populations of no more than approximately 25,000 residents."

This is potentially a very conservative interpretation of the regulations that may counteract efforts to provide technology-inclusive, risk-informed, and performance-based guidance. The safety profiles of some advanced reactors, e.g., micro-reactors, will be analogous to research and test reactors. Further, there may be defense-in-defense features associated with advanced reactors that outweigh the benefits of establishing additional defense-in-depth via locating reactors away from population centers and/or there may be performance characteristics that could demonstrate safety in even closer proximity to population centers.

Although they are their own license class, the precedent set by research and test reactor siting should be considered for consistency, i.e., the safety profile of an advanced reactor may support siting within towns with a population greater than approximately 25,000 residents.

The NRC staff disagrees with the comment.

As discussed under comment NEI # 40, the staff cannot revise regulatory requirements through guidance documents and so RG 4.7 continues to cite the requirements for nuclear power reactors to be some distance from the boundary of population centers of approximately 25,000 persons.

No changes were made in response to this comment.

49 NEI #49 A-3.3, (c)

Consideration of Uncertainty, Page A-8, last paragraph The last sentence of this section states, However, use of a hazard assessment coupled with provisions of defense in depth (multiple means of satisfying a safety function to reduce or Provide clarity on any expectation to follow specific methodologies for hazard assessment.

The NRC staff agrees with the comment.

The sentence has been revised to:

However, use of a non-probabilistic hazard assessment technique coupled with provisions of defense in depth (multiple means of satisfying a safety function to reduce

26 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution eliminate the likelihood of phenomena) can satisfactorily address phenomenological uncertainties. Is the term hazard assessment used generally or is a specific methodology expected to be followed, e.g., seismic hazard assessment has a specific meaning.

or eliminate the likelihood of phenomena) can satisfactorily address phenomenological uncertainties associated with specific internal and external hazards.

50 NUSCALE

1. 1 Appendix A Section A-1, Page A-2 The value of 1 month described in this section (among other instances in other sections) for a radiological release duration is a somewhat ambiguous value and inconsistent with the 30-day term used elsewhere throughout DG-4034 and used exclusively in Regulatory guide (RG) 4.7 Rev. 3 and RG 1.183.

Clarify or update all instances of the exposure period description from terms of months to terms of days.

The NRC staff agrees with the comment.

The staff has made changes throughout the document to replace 1 month with 30 days.

51 NUSCALE

1. 2 Section 1.5, Page 19 The guidance does not include the use of and references to relevant Emergency Preparedness for Small Modular Reactors regulations in newly affirmed 10 CFR 50.160 and RG 1.242.

Add in references:

1. U.S. Code of Federal Regulations, Emergency Preparedness for Small Modular Reactors and Other Nuclear Technologies, Section 160 (Proposed),

Part 50, Chapter 1, Title 10, Energy (10 CFR 50.160).

2. U.S. Nuclear Regulatory Commission, Performance-Based Emergency Preparedness for Small Modular Reactors, Non-Light Water Reactors, and Non-Power Production or Utilization Facilities, Regulatory Guide 1.242 The NRC staff agrees with the comment given the publication of the final rule on November 16, 2023 (88 FR 80050).

As described in the NRC resolution to comment NEI

1. 17, the staff has added a reference to the revised regulations in Section 1.5.3.

27 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution Revision 0 issued November 2023.

52 NUSCALE

1. 3 Section 1.5.3 Page 20 This entire section does not include the benefits of the newly affirmed 10 CFR 50.160 and RG 1.242. The affirmed EP rule 10 CFR 50.160, Emergency Preparedness for Small Modular Reactors and Other Nuclear Technologies provides a performance-based and consequence-oriented regulation that recognizes safety enhancements incorporated into the newest SMR and advanced reactor designs. RG 1.242 identifies methods and procedures the NRC staff considers acceptable for use by applicants and licensees of SMRs to demonstrate compliance with performance-based emergency preparedness requirements outlined in 10 CFR 50.160.

Add in the description or a new subsection (1.5.4) to include 10 CFR 50.160 and RG 1.242 as applicable to small modular reactors and other nuclear technologies.

The NRC staff agrees with the comment given the publication of the final rule on November 16, 2023 (88 FR 80050).

As described in the NRC resolution to comment NEI

1. 17, the staff has added a reference to the revised regulations in Section 1.5.3.

53 NUSCALE

1. 4 Section 1.5.3, Page 20 SMRs and other nuclear technologies are demonstrating Emergency Planning Zones (EPZ) can be sized at the site boundary.

With an EPZ sized at the site boundary, predetermined prompt protective measures to evacuate the public, shelter in place, and administer potassium iodide will not be required. With the slow progression of accident scenarios, time is available for Clarify or update how the requirements for siting are applied and changed if an EPZ is sized at the site boundary.

The NRC staff agrees in part.

As described in the NRC staff resolution to comment NEI #17, the staff has added a reference to the revised regulations for alternative EP requirements in Section 1.5.3.

The staff expects there to be some correlation between those plant designs that can take advantage of the performance-based emergency planning provisions of 10 CFR 50.160 and those proposing to justify the alternative approach in Appendix A for considering

28 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution offsite emergency response agencies to initiate an appropriate protective response to adequately protect public health and safety during the early phase of an accident.

population density. Some aspects of modelling important design features and estimating offsite consequences will be similar for justifying alternatives for emergency planning, determinations of EABs and LPZs, and determining the distances out to which population density is assessed. However, there are also differences between the various analyses in terms of assumptions and consideration of results (e.g., different exposure times). The siting requirements have not been revised, and the evaluations for determination of the EAB, LPZ, and distance to population center remain the same; therefore, no changes were made in response to this comment.

54 NUSCALE

1. 5 Appendix A, Page A-1 to A-8 There has been significant progress with SMRs and other nuclear technologies demonstrating the design and safety features during accidents.

The RG does not address if prior to completing siting investigations for plants in higher population areas, if NRC review and approval of a new technologys accident scenarios is required.

Clarify if NRC review and approval of a new technologys Chapter 15 and Chapter 19 dose consequences is required prior to completing a site investigation for a location within a higher population area.

The NRC staff agrees in part. The following footnote has been added to Section A-3:

Although population densities will ultimately be considered in a site-specific licensing application, some supporting analyses could be provided in generic documents such as a topical report, standard design approval, or standard design certification and subsequently referenced within a site-specific application with the appropriate confirmations that the generic analyses were applicable to the subject site. In the absence of generic analyses supporting the use of the alternative siting guidance in this appendix, the scope and fidelity of the required site-specific analyses to justify an alternative distance for assessing population density would need to satisfy the requirements for the specific type of application (e.g., construction permit or operating license).

29 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution 55 BTI #1 Alignment of Metrics The existing requirement for large LWR emergency planning zones is about 10 miles.2 The population density limited area in DG-4034 is twice that distance, or 20 miles. The finalized rulemaking for small modular reactors and other new technologies defines an emergency planning zone where a 1 rem total effective dose equivalent to the public over 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> from the release of radioactive materials from the facility.3 The proposed distance in this guidance for the population density distance is twice the distance at which the public dose would be 1 rem over a 30 day period.

The difference between the time periods results in a requirement in this guidance that is more strict than existing guidance. It also creates an additional distance to determine and evaluate the 30 day distance is likely to be farther from the site than a 96 hour0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> distance using similar assumptions.

1 SECY-20-0045, ADAMS No. ML19143A194 2 10 CFR 50.47(c)(2) 3 Emergency Preparedness for Small Modular Reactors and Other New Technologies. Federal Register, 88 FR 80050, November 16, 2023 The NRC staff disagrees with the comment.

The comment overstates any historical relationship between how the NRC established requirements for emergency planning zones and the guidance related to assessing population densities. Although there may be some overlap (as discussed in the response to NUSCALE #4) this guidance document and the Emergency Preparedness for Small Modular Reactors and Other New Technologies rule are addressing separate regulatory requirements. As described in SECY-20-0045, the rationale for using the estimated dose over a 30-day period was to conform to the models and calculations expected to be part of the licensing process described in industry guidance and RG 1.233.

In addition, considering the possible estimated doses accumulated over 30 days serves to limit societal risks from postulated accidents beyond assessing the appropriate planning for immediate protective actions.

It should be emphasized that the guidance in this RG does not create new requirements, and shows one way that an applicant can meet the requirements of 10 CFR 100.21(h).

No changes were made in response to this comment.

56 BTI #2 Categorically permitting existing sites Analysis of population density within 10 miles of existing nuclear power facilities shows the 500 pp/sq.mi. threshold is exceeded at 15% of existing plants.4 Appendix A of this proposed guidance (DG-4034) allows for a scalable distance for the low-population density area. Figure 1 shows that seventeen percent of existing sites exceed the population density limit at some distance from the site. The analysis only includes permanent residents, and therefore is conservative in estimating population density.

The NRC staff agrees in part.

The existing guidance as well as the criterion in DG-4034 is for use in siting decisions and the NRC has acknowledged that subsequent population growth may result in higher population densities during the lifetime of an operating reactor. However, 10 CFR 100.21(h) states that new reactors should be sited away from very densely populated centers and preferably in areas of low population density. The regulation also supports possibly siting reactors in an area not having low population density considering safety, environmental, economic, or

30 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution Figure 1: Portion of existing sites that exceed the population density criterion Regulatory Guide 4.7 considers population density within about 5 years of initial plant approval. Population growth after approval is normal and expected. However, the population density limit as defined would preclude some existing nuclear power sites from consideration.

The NRC has determined that existing nuclear power sites, or sites holding early site permits, are suitable and continues to evaluate suitability through oversight. While R.G.

4.7 allows for justification for the use of a site that exceeds the population density threshold, it is unnecessary to require additional consideration, as described in 10 CFR 100.21(h), for a site the NRC has already approved for a nuclear power facility. A categorical exemption should be included in this guidance for existing sites.

4 Population data collected from most recent Evacuation Time Estimate study for each site other factors. The flexibility provided by the regulation and related guidance can address the possible siting of a new reactor at or near an operating reactor given the potential implications with safety, environmental, economic, or other factors.

No changes were made in response to this comment.

57 BTI #3 Density variation In some cases, the averaged population density criterion is exceeded close to the site, but not farther out. The implication is that smaller zones could be limited by non-uniform population The NRC staff disagrees with the comment.

31 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution relative to distance from the site clustering.

Figure 2 shows that population density typically increases 3-5 miles from the site due to small towns which are typical within the vicinity of existing power plants. This represents a typical commute distance for a rural worker and should be expected.

The result is that more sites will be considered unsuitable that have 1-rem distance (as defined in the regulatory guide) of 2-miles, than if the same site had a 3-mile or greater distance. A larger 1-rem distance represents a larger source term, and therefore a greater overall risk to the public. It is counterintuitive that a larger source term should result in acceptance of site suitability compared to a smaller source term. The cause of this disparity is the use of population density and distance from the site as a proxy for risk. The significant historical experience with this approach is useful for regulatory predictability. However, that experience is predominantly with a single, non-scalable, distance.

Applicant should be able to optionally consider a distance that is greater than the preferred The existing guidance as well as the criterion in Appendix A is based on the population density averaged over any radial distance out to the specified boundary (cumulative population at any radial distance divided by the area at that distance) being below 500 persons per square mile (ppsm). The specified distance is either 20 miles as noted in the body of RG 4.7 or an alternative lesser distance determined by analyses described in Appendix A. In either case, a population density higher than 500 ppsm at 2 miles would exceed the criteria even if the population distribution was such that the average density at a distance of 3 miles or some other distance was less than 500 ppsm. The purported disparity in the comment is therefore not an issue when considering population density using the guidance in RG 4.7.

No changes were made in response to this comment.

32 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution distance from the 1-rem dose boundary in cases where population clusters are expected to impact density. This would require evaluation of low population farther from the site and increases the total area in the density calculation. If the area at a farther distance meets the population density limit, the requirements and intent of 10 CFR Part 100.21(h) are met.

58 BTI #4 Distance Multiplier Area of a circle increases non-linearly with distance from the center (radius). Population as a function of a population density limit (in this case 500 pp/sq.mi.) increases proportionally to area. An alternative distance metric can reduce the challenges associated with the twice-the distance proposed metric and be more aligned with the performance objective of controlling societal risks.

The cumulative maximum potential population relative to different distances from the site are shown in Figure 3. One alternative metric adopts the 1.33 distance multiplier between the Low population Zone and a population center defined in 10 CFR 100.21(b). Another alternative metric considers twice the area of the circle from the site related to the 1-rem dose distance.

The NRC staff disagrees with the comment to the extent that it proposes changes to the guidance.

The NRC staff presented several options to the Commission for consideration in SECY-20-0045. The paper included discussions of possible approaches based on both area (Option 2 that used a combination of dose factor and area) and linear distance (Option 3 that was approved by the Commission in SRM-SECY 0045 dated 13 July 2022). The discussions of each option in SECY-20-0045 addressed how the option considered the time-dose-distance relationships mentioned in the comment. The comment offered no specific reasons as to why multipliers of 1.41 or 1.33 better address the time-dose-distance relationship and the related societal risks (e.g., relocation of populations) than do the criteria approved by the Commission and used in Appendix A of RG 4.7.

No changes were made in response to this comment.

33 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution Twice the area is achieved using a distance multiplier of 2. The multiplier is calculated by, Where r1 is the 1-rem dose distance and r2 is the distance that would result in twice the total area relative to r1.

As shown in Figure 3, the twice the distance of the 1-rem dose proposed in DG-4034 results in a total potential population that quickly diverges from the 1-rem distance population in a non-linear manner. It also does not reflect that the source term decreases with distance from the source.

The alternative multipliers scale the total potential population relative to the population within the 1-rem dose distance which considers societal risk more consistently. One of the proposed alternative multipliers should be implemented in the guidance to be more consistent with the objective of considering the potential societal impact.

59 BTI #5 Siting challenges unique to fossil-fuel facilities Existing fossil-fuel based power sites may be repowered with nuclear reactors. The NRC Staff considered the potential to utilize fossil-fuel sites in SECY-20-0045, stating the selected Option 3 would increase the number of allowable sites for advanced reactors in comparison to current guidance, including sites at retiring fossil stations and isolated communities with populations below 25,000 residents.5 Several projects located at or near retiring fossil-fuel sites are in pre-application or earlier stages of licensing. Therefore, it is prudent to consider regulatory guidance relative to those sites.

Differences between population density near coal plants and existing nuclear plants are not statistically significant. 6 Population density near gas plants compared to existing nuclear plants is statistically significant and more than twice as dense on average (mean 303 vs 127). While the data used in prior sections are derived from existing nuclear power sites, similar challenges should be expected at fossil-fuel sites.

5 Population-related Siting Considerations for Advanced Reactors, SECY-20-0045 The NRC staff acknowledges the comment.

The comment does not seem to include any specific proposal to revise the guidance in RG 4.7.

No changes were made in response to this comment.

34 No.

Commenter Commenter Comment #

DG-4034 Section Specific Comments Commenter Recommendation NRC Resolution 6 Carless, T. S. E. (2018). Framing a New Nuclear Renaissance Through Environmental Competitiveness, Community Characteristics, and Cost Mitigation Through Passive Safety (Version 1). Carnegie Mellon University. https://doi.org/10.1184/R1/6717320.v1