ML22024A245

DG-4030 (RG 1.249 Rev 0) Public Comment Resolution Table

ML22024A245
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Issue date:	08/09/2023
From:	Jason White NRC/NRR/DEX/EXHB
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Karagiannis H
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ML22024A165	List: ML22024A241 ML22024A245 ML22024A253 ML22159A226
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DG-4030 RG 1.249 Rev 0
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Response to Public Comments on Draft Regulatory Guide DG-4030, Use of ARCON Methodology for Calculation of Accident-Related Offsite Atmospheric Dispersion Factors Proposed New Regulatory Guide 1.249 On August 17, 2021, the U.S. Nuclear Regulatory Commission (NRC) published a notice in Volume 86 of the Federal Register (FR) (86 FR 46024) announcing the availability for public comment of Draft Regulatory Guide (DG)-4030, Use of ARCON Methodology for Calculation of Accident-Related Offsite Atmospheric Dispersion Factors, for new Regulatory Guide (RG) 4.28. The public comment period ended on September 16, 2021. It should be noted that, after further consideration of the applicability of this RG, the staff decided that it is more suitable to be listed under the RGs of Division 1, Power Reactors. As a result, the RG number was changed to RG 1.249, using the same RG title, instead of being listed under Division 4, Environmental and Siting, as RG 4.28. The NRC received comments from the following organizations.

Agencywide Documents Access and Commenter Name and Organization Management System (ADAMS) Accession No.

Marsha Kinley ML21273A156 Duke Energy Delaney Simmons ML21272A286 Kairos Power T.M. Cook ML21272A285 Tennessee Valley Authority (TVA)

Richard Gropp ML21272A287 Exelon Generation Company, LLC Ray Schiele ML21272A350 TVA The table below shows the public comments and the NRC staffs responses.

Commenter Section Specific Comments NRC Resolution T.M. Cook 2.1.1 In Section 2.1.1. Onsite Meteorological Data, The NRC staff agrees with this comment and added a (TVA) Page 9 recommendations for meteorological data collection is sentence to Section 2.1.1 stating that wind direction should be presented. Regarding wind direction data, there is no recorded as discussed in RG 1.23 and its supporting specification on whether the parameter should be collected documentation (ANSI/ANS-3.11-2005).

as a scalar or vector average (or both). Further guidance is requested.

Delaney 2.2.1 and 2.2.2 Section 2.2.1 on page 11 and Section 2.2.2 (page 12) imply The NRC staff agrees that a clear definition should be Simmons Page 11 what [Power block Area (PBA)] is, but a clear definition of provided. After consideration, the staff changed the term (Kairos) PBA should be provided.

Commenter Section Specific Comments NRC Resolution power block area (PBA) to nuclear island. This term is more consistent with those used in previously reviewed applications.

Delaney C.2 A performance metric should be developed for when site The NRC disagrees with this comment. This RG does not Simmons Page 8 atmospheric transport and diffusion conditions are not exclude any areas from consideration. However, the RG does (Kairos) suitable for application of the dispersion algorithms in indicate that the applicability of ARCON dispersion algorithms ARCON, rather than deterministically excluding Alaska and may not apply or may require additional modification to Hawaii from the applicability of ARCON. account areas characterized by extreme and persistent restrictive dispersion conditions. No change was made in response to this comment.

Delaney C.2 This section is written for design certifications and may not The NRC staff agrees in part and has added a statement Simmons Page 8 apply to construction permits. This section should be graded under Applicable Regulations to address advanced and test (Kairos) in two dimensions: 1. Construction permit vs. design reactors.

certification, and 2. Test reactors vs. power reactors.

Delaney 2.1.1 There should be a graded approach for meteorological data The NRC staff disagrees with this comment. This RG is Simmons Page 9 expectations between power reactors and test reactors. consistent with existing guidance related to meteorological (Kairos) data sets for power, test, and advanced reactors. This RG provides a graded approach for meteorological data, as it provides guidance for the use of both onsite and alternative data, as described in Sections 2.1.1 and 2.1.2. No change was made in response to this comment.

Delaney 2.1.2 There should be a graded approach for technical detail The NRC staff disagrees with this comment. This RG Simmons Page 9 expectations when using alternative meteorological data provides a graded approach for meteorological data (Kairos) between power reactors and test reactors. expectations for both onsite data and alternative data in Sections 2.1.1 and 2.1.2. The guidance provided is just one way to meet the NRC regulations and is applicable to any type of reactor that meets the applicability statement, which includes both power and test reactors. No change was made in response to this comment.

Delaney 2.1.2 (last There should be a graded approach for meteorological data The NRC staff disagrees with this comment. This RG Simmons paragraph) expectations between power reactors and test reactors. provides a graded approach that is consistent with both (Kairos) Page 11 existing guidance related to meteorological data sets for power, test, and advanced reactors. The guidance provided is just one way to meet the NRC regulations and is applicable to any type of reactor that meets the applicability statement, which includes both power and test reactors. No change was made in response to this comment.

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Commenter Section Specific Comments NRC Resolution Delaney 2.1.2 (last Is 5 years of weather data necessary to have confidence in The NRC staff disagrees with this comment. The RG provides Simmons paragraph) the representativeness of data to determine 95th percentile one way to meet the NRC regulations. The NRC staff finds (Kairos) Page 11 and 99.5th percentile X/Q per RG 1.145? that 5 years of offsite data acceptable because of the uncertainty in using meteorological data from a non RG 1.23 qualified system. RG 1.23 provides guidance to develop an onsite meteorological monitoring system that ensures high data quality. Five years of data provide confidence in meteorological data collected from systems with different design specifications. No change was made in response to this comment.

Delaney 2.1.2 (last The relatively short time scale of 5 years is long when The NRC staff disagrees with this comment. The use of the Simmons paragraph) compared to the number of hours to calculate 99.5th phrase relatively short time scale is referring to the (Kairos) Page 11 percentile X/Q. 5 years is also longer than the time scale remainder of the sentence, which reads ...added attention requirements for onsite monitoring in RG 1.23. It is unclear should be given to the comparison between the offsite why the staff considers 5 years to be a relatively short time station(s) and the conditions at the site, as discussed above scale. in Sections 2.1.2(f) and 2.1.2(g) of this RG. The comparison between onsite data and offsite data usually involves long-term data justifying the representativeness of the onsite data (see NUREG-0800, Section 2.3.2, Subsection III(1), and RG 1.70, Section 2.3.3). Previously the staff and industry have interpreted long term to mean a climate normal period of 30 years or longer. Since, in the case of Section 2.1.2 of this RG, there is no comparison to onsite data, 5 years is both a relatively short time and will be considered representative of the conditions at the site. No change was made in response to this comment.

Delaney 2.1.2 (last Should 2.1.2(6) and 2.1.2(7) be 2.1.2(f) and 2.1.2(g), The NRC staff agrees with this comment. The suggested edits Simmons paragraph) respectively? to the RG were made.

(Kairos) Page 11 Delaney 2.3.2 An acceptable method using a single code (i.e., ARCON) The NRC staff disagrees with this comment. The existing Simmons Page 15 should be provided. versions of ARCON are not able to model plume rise and do (Kairos) not appear to adequately estimate effluent concentrations at the bases of industrial stacks. The staff recognizes the shortcoming of modeling this rare, but plausible, scenario and has provided this method as an alternative. This mirrors the same control room intake configuration as in RG 1.194. No change was made in response to this comment.

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Commenter Section Specific Comments NRC Resolution Delaney Appendix A In Section 3.7 of NUREG/CR-6331, the larger of the 1-hr The NRC staff agrees with this comment. The RG was Simmons Page A-1 and 2-hr averaging interval is used for the 0-2 hr period. updated to recommend that licensees and applicants use the (Kairos) 1-hr X/Q, which is usually be the most conservative method and which is consistent with RG 1.145. The staff also added that NUREG/CR-6331 recommends that the larger of the 1-hour or 2-hour averaging periods should be used but that this is likely to only apply under certain circumstances.

Richard Background Under the Background section (Page 5), last paragraph, last The NRC staff agrees with this comment. The suggested edits Gropp Page 6 sentence, Exelon recommends inserting a period "." at the to the RG were made.

(Exelon) end of the sentence.

Richard 2.1.1 Section 2.1.1 (Page 8) states "data should meet the 90- The NRC staff agrees with this comment. The suggested Gropp Page 9 percent recovery criterion." Exelon recommends inserting edits to the RG were made.

(Exelon) "RG 1.23" before "90-percent" for clarity purposes.

Richard 2.1.1 Section 2.1.1 (Page 8) provides guidance related to the This comment is outside the scope of this RG. However, the Gropp Page 9 minimum amount of onsite meteorological data that is NRC staff expects to develop a future update to RG 1.194 (Exelon) significantly different than the guidance in RG 1.194. Exelon during a larger review of atmospheric dispersion guidance believes that this change in guidance should also be documents applicable to RG 1.194. Therefore, does the NRC plan to revise RG 1.194 to incorporate the relevant changes made in DG-4030?

Richard 2.1.2 Section 2.1.2 (Page 8) provides guidance in developing This comment is outside the scope of this RG. However, the Gropp Page 9 meteorological data from alternative sources that is not NRC staff expects to develop a future update to RG 1.194 (Exelon) found in RG 1.194. Therefore, does the NRC plan to revise during a larger review of atmospheric dispersion guidance RG 1.194 to incorporate the relevant changes made in DG- documents.

4030?

Richard 2.2.1 Section 2.2 implies that individual ARCON runs will be run The NRC staff disagrees with the comment that additional Gropp Page 11 for all 16 source-to-receptor sectors. Exelon believes that it guidance should be included. The current functionality of the (Exelon) would be helpful to include additional guidance related to ARCON96 and ARCON 2 graphical user interfaces (GUIs) this, including if this is the preferred approach or if there are allows only one source-receptor pair to be entered at a time, alternatives to running all the combinations. therefore, that is the methodology to use. No change was made in response to this comment.

Richard Section 2.3.4 Plants may have safety-related and seismically designed The NRC staff agrees with the comment and added clarifying Gropp Page 16 systems that process and release activity at a specific point text to Section 2.2.1 of the RG stating that if the location(s) of (Exelon) from a building (e.g., a plant vent). Typical applications of the release point is known, that location may be used rather RG 1.194 would include modelling this scenario as a point than the shortest distance from the building edge.

source at the vent release point, which could be on the roof. Exelon believes that Sections 2.2 and 2.3.4 do not 4

Commenter Section Specific Comments NRC Resolution seem to address this scenario and further clarification might be beneficial.

Richard 2.3.4 The use of point sources on the edge of a building closest to The NRC staff agrees with the comment and added a Gropp Page 16 the exclusion area boundary (EAB) or low population zone discussion in Section 2.2.1 to this RG that points licensees (Exelon) (LPZ) in a given sector is considered conservative. and applicants to Section 2.3.5 of this RG and RG 1.194 for However, the approach in Sections 2.2.1 and 2.2.2 do not additional details on diffuse area sources. In Section 2.3.5 of provide any guidance related to robust structures that may this RG, the staff also added that, for some situations, it may be seismically qualified and safety-related. Exelon believes be more appropriate to use a diffuse area source.

that a robust structure of this design that does not have an engineered release point on the surface should be modeled as a diffuse area source. Guidance for this situation is provided in RG 1.194, Section 3.2.4, and should also be applicable in this new RG as well.

Richard 2.3.2 The ARCON calculation process to address multiple The NRC staff agrees with the comment and recognizes the Gropp Page 14 sources, for all 16 sectors, including determining the 99.5th challenge of needing multiple ARCON runs for an analysis.

(Exelon) percentile X/Q values for the various time periods may be a However, the current functionality of the ARCON96 and challenge to implement. ARCON 2 GUIs allows only one source-receptor pair to be entered at a time. No change was made in response to this comment.

Richard 2.3.4 and 2.3.5 Sections 2.3.4 and 2.3.5 (Page 15) describe modeling the The NRC staff disagrees with the comment that the figures Gropp Page 16 source as a point or a point in the center of a diffuse area should include buildings that do not release radioactivity.

(Exelon) source. The guidance in Sections 2.2.1 and 2.2.2 describe Sections 2.3.4 and 2.3.5 suggest that the closest point along modeling the source to receptor as distances from edges of the edge of the applicable building be used. The staff does buildings from which radioactive material could potentially not include non-radiological buildings in Figure 2.2 since be released. Section 2.2.2 provides a useful option for the those are not the buildings of concern. Adding in non-analyst to explicitly evaluate the effects from individual radiological buildings would clutter the image and might lead release points. However, Figure 2-2 assumes that all to confusion. No change was made in response to this buildings release radioactivity. Exelon believes that a better comment.

example of Figure 2-2 may be to include some buildings that do not release radioactivity.

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Commenter Section Specific Comments NRC Resolution Richard Appendix A Appendix A does not include examples on calculating the The NRC staff agrees with this comment and revised the text Gropp Page A-3 X/Q time intervals beyond 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. ARCON methodology to state that other averaging periods can be calculated using (Exelon) determines these by a weighted combination of the two the cumulative frequency distribution (.CFD) example and applicable X/Q values. Exelon believes providing an ARCON output files.

example of calculating the 99.5th percentile for the time intervals beyond 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, including equations and the procedure, is needed to ensure the analyst performs the calculation according to approved guidance.

Ray Schiele Background This Draft RG does not mention the short-term dispersion The NRC staff disagrees that this RG should also address the (TVA) Page 6 estimates for an environmental report. NUREG-1555 and atmospheric dispersion factors for an environmental report.

RG 4.2 address the 50th percentile X/Qs for the design The focus of this RG is on design-basis accident dispersion basis accident evaluation in an environmental report. This factors, rather than the nominal meteorological conditions guidance should address ARCON as an acceptable considered in NUREG-1555. However, the same data and methodology for calculation of 50th percentile atmospheric assumptions used in Appendix A to this RG may be useful for dispersion factors for an environmental report. estimating the 50-percent X/Q value but would need appropriate technical justification consistent with proposed use.

Marsha Discussion DG-4030 states that only the user interface was updated in The NRC staff agrees with the comment and added a Kinley Page 6 ARCON 2.0, and not the algorithms. However, the ARCON sentence to the background section to read, Although the (Duke) 2.0 User Guide (Figure 2.8) and NRC RAMP response ARCON 2 model includes an option to use RASCAL diffusion (11/12/2020, ATM_HelpResource@nrc.gov from Kerstun coefficients (NUREG-1940), this guidance is applicable to Norman) to inquiry from Duke Energy (Marsha Kinley) both only the ARCON96 diffusion coefficients provided in indicate that ARCON 2.0 allows the user to select either RG 1.194.

ARCON96 or RASCAL diffusion coefficient adjustments.

a. Recommend adding to DG-4030 the NRCs preference or guidance on use of either ARCON96 or RASCAL diffusion coefficients for setup of ARCON 2.0.

Marsha Discussion b. Recommend explaining the differences of selecting either The text includes references to both the RG 1.194 and Kinley (Duke) Page 6 ARCON96 or RASCAL diffusion coefficients in the ARCON NUREG-1940 dispersion coefficients. No change to this RG is 2.0 Users Guide and/or in DG-4030. Only minimal needed, since this guidance is only to be used with ARCON96 information is available from NUREGs on RASCAL and dispersion coefficients.

related presentations:

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Commenter Section Specific Comments NRC Resolution Marsha Discussion Where is the full content of ARCON 2.0 Users Guide The NRC staff agrees with this comment that the previous Kinley Page 6 available? The ARCON 2.0 documentation from the NRCs version of the ARCON 2.0 Users Guide was organized in a (Duke) RAMP website only provides chapter 2 of the users guide, manner that could be confusing. The Users Guide has been but the reader is referred to chapter 3 for more information updated and is available through the RAMP Web site on diffusion coefficients. Are chapter 3 and the full content (ADAMS Accession No. ML22004A219).

of the ARCON 2.0 Users Guide available to the public?

Marsha 2.2.1 Will use of the conservatively shorter EAB and LPZ The NRC staff does not intend to use the guidance in this RG Kinley Page 11 distances measured from closest powerblock building(s) as to support actions in a manner that would constitute (Duke) proposed in DG-4030, instead of actual release point(s), backfitting. The staff added a sentence to Section 2.2.1 set a precedence to then require updating an existing stating that it is also acceptable to use known release point facilitys EAB and LPZ distances for licensing bases? Are locations rather than the closest edge of the building. Use of revisions to station procedures, UFSAR, and ODCM (etc)) this method may further inform the location of offsite needed to agree with the shorter distances to EAB and LPZ sampling locations for Radiological Environmental Monitoring used per the DG-4030 method? Will this also impact Programs (REMP) but in a way consistent with existing selection of offsite sampling locations for REMP programs? procedures.

Marsha 2.4 Clarify whether ARCON (CFD output) or PAVAN is preferred The NRC staff is not stating a preference for either PAVAN or Kinley (Duke) Page 17 to determine the 99.5 percentile max sector X/Q. Suggest ARCON to determine the 99.5th-percentile maximum sector revising text in (2.4). X/Q. This RG only provides one acceptable method.

• (2.4) states that ARCON does not calculate the 99.5 percentile max sector X/Q, but PAVAN does.

• (2.4.2) states that ARCON CFD output file can be used to calculate the 99.5 percentile X/Q for any sector.

Marsha Appendix A The result in Appendix A example for the 99.5th percentile The NRC staff agrees with this comment and has made the Kinley Page A-3 X/Q value of 1.97E-03 is not reproducible. Verify that following changes to the text: (a) HTotal is 8,750 for this (Duke) values given in the example are correct and show the example. (b) The text has been updated to now recommend values for all input variables. that the 1-hr X/Q value be used for most cases. The staff has

a. What is the value for the total number of hours (Htotal) in corrected and clarified the example numbers. The incorrect this example? 99.5 percentile value in the example (1.97E-03) was replaced

b. There is a typo either on page A-2 or A-3 for the lesser with the correct value (2.077E-03).

% exceedance value in the example. Two different values are stated for the lesser % exceedance. Verify the correct value and edit the text of Appendix A accordingly.

Marsha General Comment Why is NRC proposing to create a new Regulatory Guide The NRC staff agrees, in part, with this comment. The RG Kinley (Duke) Page 1 4.28 in the Environmental and Siting division (DG-4030) number was reassigned to the Power Reactor division and will rather than revising the existing Reg. Guide 1.145 in the be RG 1.249. Updating RG 1.145 was considered an Power Reactors division? It appears that the proposed alternative option, since it is also used to determine design-alternative use of ARCON 2.0 for DBA offsite impacts is basis accident (DBA) offsite impacts. However, since this RG 7

Commenter Section Specific Comments NRC Resolution applicable to both existing and future nuclear power uses ARCON rather than PAVAN, and includes different facilities, as long as EAB and LPZ distances are less than dispersion assumptions, it may have been confusing to 1200m. Why was revision of RG 1.145 not considered as an combine the two approaches into one guide.

option in the Regulatory Analysis for RG 4.28 (NRC-2021-0133-0003_content.pdf)?

Recommend revising RG 1.145 to include the proposed alternative method presented in DG-4030 for calculating accident related offsite atmospheric dispersion factors (e.g.

suggest adding an appendix to RG 1.145 for the proposed alternative method), instead of creating a new RG 4.28.

Creating multiple guidance documents on the same topic for different methods will ultimately confuse the regulatory guidance for the industry and increase NRC costs to maintain separate documents.

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