ML25192A114

License Termination Plan License Amendment Request Audit Plan

ML25192A114
Person / Time
Site:	Oyster Creek
Issue date:	07/11/2025
From:	Amy Snyder Reactor Decommissioning Branch
To:
References
EPID L-2024-LLA-0107
Download: ML25192A114 (1)

Text

Enclosure AUDIT PLAN REGARDING PROPOSED LICENSE TERMINATION PLAN AMENDMENT REQUEST HOLTEC DECOMMISSIONING INTERNATIONAL, LLC OYSTER CREEK NUCLEAR GENERATING STATION DOCKET NO. 50-219 I.

BACKGROUND By letter dated August 1, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24214A037), as supplemented by letters dated March 26, 2025 (ML25086A156), April 29, 2025 (ML25119A267) and May 13, 2025 (ML25133A131), Holtec Decommissioning International, LLC (HDI) requested approval of a proposed amendment to the Renewed Facility Operating License DPR-16 for Oyster Creek Nuclear Generating Station (OCNGS or Oyster Creek) to include license termination plan (LTP) requirements.

II.

REGULATORY AUDIT BASES A regulatory audit is a tool available to the U.S. Nuclear Regulatory Commission (NRC) staff that can help to efficiently gain understanding, verify information, and/or identify information that will require docketing to support an NRC staff decision. This audit is a planned license or regulation-related activity that includes the examination and evaluation of primarily non-docketed information. An audit was determined to be an efficient approach toward a timely resolution of questions associated with this request. Performing a regulatory audit is expected to assist the NRC staff in efficiently conducting its review and gaining insights into the licensees processes and procedures. This approach is expected to minimize the potential for multiple rounds of requests for additional information (RAIs) and eliminate questions that would no longer be necessary to make a safety determination.

The basis of this audit is the licensees request for Oyster Creek as identified above. The audit will be performed consistent with NRC Office of Nuclear Reactor Regulation Office Instruction LIC-111, Revision 2, Regulatory Audits, dated December 19, 2024 (ML24309A281) and will be conducted virtually.

III.

PURPOSE AND SCOPE The purpose of the audit is to gain a more detailed understanding of the licensees processes and procedures. Information that the NRC staff relies upon to make the safety determination must be submitted on the docket. The areas of focus for the regulatory audit are the information contained in the licensees submittal, the enclosed audit information (attachment 2) needs, and all associated and relevant supporting documentation (e.g.,

methodology, process information, calculations). The relevant supporting documents are identified below.

2 IV.

INFORMATION AND OTHER MATERIAL NECESSARY FOR THE REGULATORY AUDIT The NRC audit team will require access to licensees personnel knowledgeable of the technical aspects of the request and the audit questions attached to the plan. The licensee is requested to compile all the information identified in this section prior to the audit so that it is readily available to the NRC staff. The documentation can be provided by presentations, documents, or calculation details.

Documents 1.

Technical basis documents for dose methodology or supplements 2.

Technical basis documents for final status survey strategy or supplements 3.

Technical basis documents for groundwater modeling methodology for dose and final status survey or supplements 4.

Before the audit is over, the NRC staff will determine if the supplemental information is needed to be docketed because it would be needed to make regulatory decisions.

Demonstrations and Discussions 1.

Audit questions (Attachment 1)

V.

AUDIT TEAM The following are members of the NRC audit team:

Amy Snyder, Sr. Project Manager (Amy.Snyder@nrc.gov)

Gregory Chapman, Sr. Health Physicist (Gregory.Chapman@nrc.gov)

Cynthia Barr, Sr. Risk Analyst (Cynthia.Barr@nrc.gov)

Randall Fedors, Sr. Hydrologist (Randall.Fedors@nrc.gov)

VI.

SPECIAL REQUESTS The NRC staff would like access to the documents listed above in Section IV through an online portal that allows the NRC staff to access documents remotely via the internet at least 1 week prior to the start of the audit. The NRC staffs access to the online portal should be terminated upon issuance of the audit summary discussed in Section VII of this audit plan. The NRCs information sharing portal will be used.

The NRC project manager will provide the licensee the names and contact information of the NRC staff who will be participating in this audit. HDI will provide the NRC project manager with the names and contact information of the HDI staff who need access to the NRC sharing portal for this audit because they will be participating in the audit. All other communications should be coordinated with the NRC project manager.

3 VII.

LOGISTICS The audit will be held from July 28 through July 31, 2025. As part of the audit, the NRC audit team will conduct a teleconference and/or video conference with the licensee for the purposes of introducing the team, discussing the scope of the audit, and describing the information to be made available on the online portal. The NRC staff acknowledges the potential for the proprietary nature of some of the information requested. It will be handled appropriately throughout the audit. The NRC staff will take notes that will be marked as proprietary, for such material, and will not remove hard copies or copy electronic files. The NRC project manager will coordinate any changes to the audit schedule and location with the licensee. A proposed agenda and the questions for the audit are attached to this audit plan. The audit period may be reduced or extended, depending on the progress NRC and HDI staff make in addressing audit questions. If new technical items are identified, additional audit sessions may be needed to facilitate the continued review of the requested amendment.

VIII.

DELIVERABLES At the completion of the regulatory audit, the NRC staff will conduct an exit briefing and provide a summary of the audit results. The NRC staff plans to prepare a regulatory audit summary that will include the documents reviewed, the audit activities, and any RAIs that were discussed or that will be issued based on the audit, as applicable.

Proposed Audit Agenda TIME TOPIC July 28, 2025 9:00 a.m. - 9:15 a.m.

Entrance Meeting: Purpose, Scope, and NRC and licensee introductions and logistics 9:15 a.m. - 12:00 p.m.

Health Physics July 29, 2025 1:00 p.m. - 3:00 p.m.

Hydrogeology July 30, 2025 9:00 a.m. - 12:00 p.m.

Dose Assessment July 31, 2025 1:00- 3:00 p.m.

Exit Meeting: Review of Path Forward/Action Item Discussions and Exit Audit Questions & Clarifications Health Physics -

1) Data Reporting: Clarify how HDI reports results from site characterization/final status surveys.

HDIs characterization summary data tables in the proposed LTP report minimal detectable concentration (MDC) as the analytical result if the actual result was less than the MDC. Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) guidance (NUREG-1575, Revision 2) states that the actual sample results should be reported even if less than 0. In the proposed LTP, HDI states it was developed following MARSSIM guidance. MARSSIM states results should be directly reported even if less than the MDC which is inconsistent with the data being presented in the characterization summary. If the results are not provided in future reports, the NRC staff anticipates additional data requests to obtain the analytical results for statistical tests so that staff can verify the licensees statistical results.

However, it would be beneficial to the NRC staff if HDI continued its practice of bolding those results that are greater than the MDC. A summary statistic table of the MDC data could be added to address the topic of achieved MDCs for the survey. This practice could further streamline the NRC staffs review as it would demonstrate that measurements had sufficient sensitivity to see residual radioactivity at the derived concentration guideline levels (DCGL) level. The only time the results less than 0 should be rounded up to 0 is when demonstrating a compliance dose (if the average concentrations of a radionuclide of concern (ROC) in a survey unit is less than 0, it should be rounded to 0 to determine a sum-of-fractions (SOF) value and associated dose for a survey unit) as there is no such thing as a negative dose. This usually means that the average concentrations for a survey unit are derived for each radionuclide and those averages that are less than 0 are then rounded to 0 before establishing the survey units SOF value. The licensee should make note of this for future data reports being submitted.

2) Determination of 75th Percentile: Clarify how HDI determines a 75th percentile. An HDI walk through of their methods will assist in an efficient review of TSD 025-032, Rev. 0 Radionuclides of Concern in Support of the Oyster Creek Station License Termination Plan.

In TSD 025-032, Rev 0, it appears that HDI uses all data to derive a 75th percentile ratio to Cs-137 or mixture ratio. The NRC staff has found it acceptable for licensees to use data which was detected above the MDC to make these types of determinations. Rather than using 75th percentiles of primarily low certainty data (less than the MDC) that could give misleading results. The NRC staff anticipates evaluating only data greater than the MDC to verify that the licensees method provides reasonable results. Please clarify whether there is a safety-related reason why HDI is using all data to derive a 75th percentile ratio?

3) LTP Section 4.8, ALARA Evaluation: Confirm the method that HDI will use to perform as-low-as-reasonably achievable (ALARA) evaluations.

It appears that the HDI is pursuing a pre-determined compliance measure method for

2 demonstrating compliance with the ALARA requirements. Per Section 6.3.6 of NUREG-1757, Vol 2, Rev. 1, Characterization, Survey, and Determination of Radiological Criteria, there are two acceptable options for demonstrating compliance with the ALARA requirement currently in the guidance: a performance-based compliance method as well as the pre-determined compliance measure. Please verify HDI intends to pursue the pre-determined compliance measure method currently described in the proposed LTP as opposed to the performance-based compliance method.

Further, in the HDI ALARA compliance demonstration in the proposed LTP, the costs for remediation detailed in the analysis appear relatively high on a per unit basis. For example, the cost of planning and engineering have a total time commitment of 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> per m3 of soil remediation. This seems unreasonable as there is seldom just a single m3 of soil remediation necessary. It implies that remediation of 100 m3 of soil as a project would require 1,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> for the planning and engineering when, instead, the originally estimated 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> is more likely to be defrayed over the entire project so that any 1 m3 of soil remediation would be charged 0.1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> for planning and engineering. This type of overhead costs should be reduced to a reasonable time frame for a reasonably sized project.

Clarification also is needed of why one analysis uses a discount rate of 0.07 while the other uses 0?

Please clarify the basis for HDIs costs for the time commitment to remediation and the discount rates used to allow the staff to determine compliance with 10 CFR 20.1402.

4) LTP Section 5.2.6.4, Surrogate Ratio DCGLs, and 5.2.6.5, Gross Activity DCGLs:

Explain how HDI determined the ratios and fractional activity associated with these derivations and whether HDI determined that the results are reasonably conservative.

Walking the NRC staff through some of its technical papers on this subject (TSD 24-01 2888, Dose Contribution from Insignificant Radionuclides in the Oyster Creek Site-Specific Suite of Radiological Nuclides, and TSD 24-062, OCNGS Structure Nuclide Fractions and Gross Activity DCGLs (DCGLGA) will save NRC staff review time before reading in-depth and verifying some of the details.

For example, using the average/median ratio for surrogates would likely underestimate at least half of the represented concentrations in samples which could be problematic if a sample concentration approaches the DCGL. In the past, the NRC staff reviewed and approved use of a conservative ratio or fractions for these types of derivations. For acceptability, the NRC staff must determine in their safety evaluation, among other things, that the dose methodology does not lead to underestimation of dose.

5) Section 5.2.3.9, Measurement Locations: Explain the rationale for allowing the final status survey (FSS) supervisor to adjust the FSS plan during a FSS (e.g., within 10 radius of the initially identified inaccessible location if practical, else a random location within the survey unit will be chosen to replace the location that is inaccessible). The NRC staff must understand HDIs FSS strategy and for acceptability, among other things, must determine that the FSS strategy meets the data quality objective process if HDI commits to following MARSSIM or is using some other approach. The NRC reviews the FSS plan to ensure all necessary information is collected for decision-making. This process involves defining the problem, identifying decisions, specifying inputs, setting study boundaries, developing

3 decision rules, and specifying acceptable limits for potential decision errors.

6) Section 5.2.6.7, Elevated Measurement Comparison Evaluations: Define/clarify what is meant as areas of elevated activity. The NRC staff believe clarifying this term for the site would streamline staff FSS report reviews.

7) Section 5.3.1, Scan Surveys and Section 5.3.2, Direct Measurements for Surfaces:

Please describe how/if ambient background will be subtracted from measurements.

Understanding how HDI will address ambient background will streamline the NRC staffs FSS report reviews.

8) Section 5.4.2, Bulk Materials: Clarify how reused site bulk materials (especially those that may be used for backfilling) will be characterized.

In the past, the NRC staff expected materials that may be used as backfill to be characterized to the rigors of the LTP commitments of a FSS. The NRC staff understands that special considerations may be appropriate if a licensee is planning to reuse building materials for backfill (e.g., the licensee would perform volumetric instead of structural surveys). Therefore, HDI should explain if it anticipates any special considerations to avoid future challenges in their decommissioning strategy.

9) Section 5.7.4, Advanced Technologies: The NRC staff would like to discuss to understand whether HDI will tie operator training and qualifications to data quality objectives. The NRC staff will need this information when determining whether use of advanced technologies will provide reasonable assurance in the results of such measurements.

10) Section 5.9.2.1, Posting Plots: Clarify whether scanning will be posted on a map (preferred) or be documented in some other way. Review of scanning data is part of the NRC staffs review of the FSS reports and knowing how this data will be presented will streamline the staffs review.

11) Section 5.9.6, Record Keeping and Section 5.9.8, Final Status Survey Reporting:

Clarify how HDI will document the FSSs and what HDI will submit to the NRC for review of the FSS Report. This information will assist the NRC staff in planning its FSS reviews to be more efficient.

For example, will HDI submit release records for each survey unit and make the final status survey report a stand-alone summary document submitted after all FSSs have been completed.

12) Radionuclides of Concern (ROCs): Explain why HDI believes it is appropriate to determine ROCs for most of the site areas, including outdoor areas, based on concrete building sampling only. Based on NRC staffs review experience it is uncommon that one area stands to represent all survey units. Further, if HDI plans to use new data in the future, HDI should explain its method for updating its ROC determination methodology.

13) Insignificant Contributors: Clarify the basis for the insignificant contributors (IC) dose and the listing of ICs. Page 6-4 of the proposed LTP appears to state that the dose from insignificant radionuclides is based on concrete measurements. Based on NRC staffs experience concrete measurements are not expected to be representative of activity

4 fractions in subsurface soils or above ground buildings planned for reuse.

Also, Technical Support Document No.25-032, Rev. 0, indicates that concrete samples were used to determine ICs. Please provide more details regarding the current basis for ICs and whether HDI has plans to validate the significant or ICs list consistent with MARSSIM guidance.

14) Validation of Significant Contributors: The text at the end of Section 5.2.6.3, Page 5-20 states that 5 percent of the samples will be analyzed for hard-to-detects (HTDs) to verify the ICs. Typically, 10 percent of samples are used to validate assumed surrogate ratios and by extension the lack of need to analyze for HTDs. Clarify the basis for using 5 percent. The staff needs this information to determine whether HDI HTD verification practices are acceptable.

15) Dose Contributions from Insignificant Contributors: The text on page 5-21 states that 0.075 mrem/yr will be added to the dose to account for the dose from ICs in soil. Section 3.3 of NUREG-1757, Volume 2, Rev. 2, Insignificant Radionuclides and Exposure Pathways states that the uncertainty should be accounted for in the evaluation of ICs, including dose from less likely but plausible (LLBP) exposure scenarios. Clarify how this information is used to determine that HTD radionuclides are insignificant to LLBP residential scenarios. The NRC staff notes that the methodology used to calculate the dose contributions for HTDs does not appear to be complete as it (i) does not account for varying mobility of easy to detect radionuclides (ETD) versus HTD radionuclides (e.g., assumes HTDs will be co-located with ETDs), and (ii) assumes that five samples will be sufficient to determine representative concentrations for use in dose calculations. Page 2-104 of the proposed LTP states that Sr-90 was only found in subsurface samples. The number of subsurface samples are limited, and the concentrations of Sr-90 do not appear to be correlated to less mobile Cs-137 or Co-60 concentrations. Therefore, the use of a maximum concentration of 0.07 pCi/g (see Table 3-1, page 7 of OCNGS Technical Basis Document No. 24-01-12-2888, Revision 0,1 Dose Contribution from Insignificant Radionuclides, based on 5 samples where Cs-137 and Co-60 concentrations are highest) to calculate the dose from Sr-90, when higher Sr-90 concentrations closer to 5 pCi/g are measured in limited subsurface samples (e.g., see page 2-124 of RCA-DEP6-043-B in the proposed LTP). The NRC staff seeks to understand HDIs approach and why additional subsurface soil samples would not be needed to better understand the contributions of Sr-90 to dose. This comment may apply to other HTDs in addition to Sr-90.

Groundwater

1) FSS Plan for Groundwater: Clarify HDIs FSS plan or strategy for estimating residual radioactivity in groundwater for use as input calculating dose due to existing groundwater contamination. Section 5.6 of the proposed LTP mentions that the measurements from wells will be used as input to Equation 5-9. Clarify (i) the period over which measurements will be collected (duration over which trends can be verified), (ii) when the measurements will be collected (e.g., after last soil disturbing activity), and (iii) why measurements at wells reflect maximum concentration across the site. This information is needed for the staff to make a determination regarding the adequacy of the groundwater survey method.

1 While Technical Basis Document No. 24-01-12-2888, Revision 0 was superseded by Technical Support Document No.25-032, Rev. 0, the proposed LTP still references the former document when estimating the dose from insignificant contributors in Chapter 5 of the proposed LTP as indicated in this comment.

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2) Detection Decision for Groundwater: Section 5.6 of the proposed LTP indicated that a dose of zero for existing groundwater contamination will be assigned for ROCs when laboratory analyses show no positive results. Clarify what is meant by positive result in section 5.6 of the proposed LTP Revision 1 and definition of the term detection limit as used in section 2.4 of the proposed LTP Revision 1 so that staff can compare the information to the terminology in Chapter 20 of Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP, NUREG-1576) guidance (i.e., decision level and critical level measurements after the last soil disturbing activity). If HDI does not intend to use MARLAP guidance, then identify if it is using other guidance or explain the basis for its groundwater detection decision strategy. Providing the requested information should assist the NRC to efficiently review the proposed LTP.

3) Groundwater Flow and Transport Pathways: Clarify or provide information that supports the simplification of the conceptual site model (CSM) considering the two uses of the CSM (i) abstraction for RESRAD inputs for flow and transport, and (ii) linking potential Historical Site Assessment (HSA) events and possible transport directions. This information is needed so that the staff can determine whether the CSM presented by HDI adequately represents the Oyster Creek sitem The simplifications for each usage may vary but should consider the three-dimensional flow field that evolved from 2006 to 2024 due to annual recharge variations, influence of construction fill and breaching of aquitard between Cape May and Cohansey aquifers, pump-and-treat remediation, and reduction in number and areal extent of wells used for groundwater contouring. Also, what is the long-term nature of the flow field, i.e., has the effect of the pump-and-treat remediation on the flow field dissipated?

For part (i) for RESidual RADioactivity (model) (RESRAD) abstraction, clarify support for hydrologic inputs (e.g., unsaturated zone (UZ) thickness, gradient) for the one-dimensional RESRAD flow abstraction considering the three-dimensional characteristics of the flow field. The discussion should involve abstractions that do not lead to underestimation of dose. The NRC staff notes that the proposed LTP and supporting documents did not include the parameter inputs for the LLBP resident farmer scenario (see request of RESRAD files in Dose Assessment section of questions). This information is necessary for the staff to review the dose assessment to determine whether it is acceptable and does not underestimate the dose.

For part (ii) on linking potential transport pathways with the HSA, clarify any supporting information that possible releases from locations west of the Reactor Building (e.g., the Old Radwaste Building and the New Radwaste Building) migrate only to the west; i.e., that contamination does not migrate vertically in the construction fill to the Cohansey aquifer and then eastward as possibly implied (though uncertain) by the mounding of represented by the potentiometric contouring of the Cohansey.

4) Unsaturated Zone Thickness: Clarify how the contaminated zone thickness and UZ thickness are implemented in the Industrial Use (IU) scenario (Table 6-15) for RESRAD simulations. Based on site information, the UZ thickness appears to vary between 5 and 20 ft across the site (excluding immediately adjacent to the canals), which is consistent with the input listed in Table 6-15. However, it is not clear if the UZ thickness includes the contaminated zone thickness, or if the thickness reflects the uncontaminated zone that lies

6 below the contaminated zone as defined in RESRAD. The NRC staff needs this information to understand the groundwater modeling for the IU scenario.

5) Uncaptured Dose Calculation for Groundwater Pathway: Clarify the approach of subtracting RESRAD groundwater concentration from existing groundwater contamination in Equation 6-17 for the dose contribution of future groundwater contamination presented in section 6.12 of the proposed LTP and in Enclosure 26 TSD 24-081, Oyster Creek Groundwater Dose Calculation Methodology to Support License Termination Plan.

Describe the assumed connection between existing groundwater contamination measurements and every solid media source term in the RESRAD-ONSITE calculations (RESRAD water concentrations in Table 6-38). Clarification may include a description of the input for the source term used to estimate the RESRAD water concentrations. This information is needed for the NRC staff to understand HDIs groundwater dose assessment strategy.

6) Hydrology

Reference:

Clarify why the 2017 Hydrogeologic Investigation Report (HIR) is not included in the submittal or provide it on the docket. If the 2017 HIR data is used in the proposed LTP, then the staff will ask that it be submitted on the docket. The 2017 HIR, 2022 HIR, and generic OCNGS HIR are all mentioned in the proposed LTP text and tables.

But only the 2022 HIR is included in the reference lists of the proposed LTP Chapters 2, 6, and 8 and only the 2022 HIR is included as an enclosure to the submittal. The 2022 HIR does not appear to contain the same information on parameter support that was in the 2017 HIR for at least one parameter. For the UZ thickness as an example, Table 6-15 of the proposed LTP stated that the basis of the range of UZ thicknesses of 1.37 to 5.94 m is the 2017 HIR where the water table was stated to 5 to 20 feet below ground surface. The 2022 HIR does not include information on the UZ thickness. The NRC staff must use the information that is docketed if it is using it in their safety evaluation report.

Dose Assessment

1) Residential Scenario Exposure Pathways: Clarify whether the drinking water pathway was considered for the residential exposure scenario (LTP Section 6.3.2). HDI evaluated the dose from Cs-137, Co-60, and C-14 according to Table 6-4 in the proposed LTP. Key assumptions of the analysis could not be identified (e.g., plant and drinking water ingestion rates) and should be provided with the RESRAD files to allow NRC to review the technical basis for the analysis. The requested modeling assumptions are risk-significant for this review because the NRC staff has not yet determined whether the residential scenario is reasonably foreseeable and eliminating exposure pathways in the IU scenario leads to higher DCGLs.

2) Surface and Subsurface DCGLs for Soils: Surface and subsurface soil DCGLs appear to be combined. While use of a single DCGL for soil may be acceptable, staff seeks to understands HDIs plans to document and implement its methods that will be used in the FSS to ensure that dose is not underestimated due to the potential compositing of relatively clean soils with higher concentration soils (e.g., scanning of soil cores to identify any elevated areas and depth discrete sampling). A good understanding of the sensitivity of dose to the depth and thickness of residual radioactivity should be reflected in survey procedures to ensure comparison of radiological survey data results to DCGLs does not underestimate dose.

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3) Groundwater Usage Surrounding the Site: The proposed LTP provides information on domestic potable and non-potable wells within a 1-mile radius of the site (Table 1-1, proposed LTP page 1-5); however, it is unclear what these wells are used for (e.g., drinking water, irrigation, IU) and the applicability of the Lacey Township ordinance on municipal water supply in the surrounding area. Please clarify (i) domestic groundwater well uses in the area surrounding the site, (ii) the applicability of Lacey Township ordinance requirements related to use of municipal water supply for properties surrounding the site; (iii) any exceptions to the ordinance; and (iv) any available information on the enforceability of the requirements. The DCGLs are significantly higher, particularly for buried sources (e.g., orders of magnitude), when the groundwater pathway is not considered. Because the unrestricted release of the site is being pursued, the basis for exclusion of the groundwater/drinking water pathway must be well understood. Clarification regarding groundwater usage in the area is needed to provide support for not including the groundwater pathway in deriving DCGLs.

4) Municipal Water Supply Requirements: Clarify the requirements of the municipal ordinance with respect to connecting to municipal water supply and disconnecting and sealing wells, which seem to apply to certain areas in Lacey Township. Does the ordinance require OCNGS to connect to the municipal water supply and does the ordinance requiring sealing of wells apply to the OCNGS based on its location (i.e., its block and lot number)?

Finally, please clarify if any potential ongoing use of groundwater wells onsite is intended for other than drinking water purposes. Licensees are to follow applicable requirements from state and local governments which may be used to provide support for elimination of the groundwater pathway; however, it is unclear what requirements apply to the OCNGS.

5) Groundwater Exclusion Zone: Clarify the extent of the groundwater exclusion zone. The groundwater exclusion zone appears to apply to a portion of the site based on the map presented below. If portions of the site are not under groundwater exclusion zone restrictions, then there may be a higher likelihood of groundwater use than currently assumed.

Map of Groundwater Exclusion Zone at OCNGS. Data accessed and image created from the New Jersey Department of Environmental Protection (DEP) DataMiner.

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6) Risk Associated with the Excavation Scenario: The excavation scenario assumes that excavation only occurs above the water table resulting in only 800 m3 of drilling spoils brought to the surface, thereby limiting the dose from human intrusion into the subsurface/substructures. Bases should be presented to support the limited depth of excavation or a more robust analysis should be performed to derive DCGLs for subsurface materials (e.g., deeper depth of excavation). Rationale for assumptions must be provided by licensees for the NRC staff to determine whether the assumptions are reasonable.

Reasonable assumptions are needed to ensure appropriate exposure scenarios and potential risk are assessed, thus providing reasonable assurance that the 10 CFR 20.1402 criteria are met.

7) Building Occupancy vs. Renovation Scenario Dose: TSD 24-085, Rev. 0, Probabilistic Dose Comparisons: Building Occupancy Scenario Vs. Room Renovation Scenario is the technical basis document supporting the conclusion that the building occupancy dose is larger for above ground buildings compared to the renovation scenario. It appears that energetic activities associated with the renovation scenario may not be reflected in the model (e.g., higher resuspension rates and removable fractions may be associated with the renovation scenario). A more thorough review and analysis will be performed by NRC staff to assess the risk-significance of the renovation scenarios. Staff seeks to further understand HDIs approach for this scenario to ensure it doesnt underestimate dose. HDI could also provide additional information on why they think the renovation scenario is not reasonably foreseeable.

8) Limitations of the RESRAD-ONSITE Computer Code in Simulating Flow Through Reactor Basement Substructures. Explain how the use of RESRAD-ONSITE to support development of DCGLs for reactor basement substructures does not underestimate dose.

RESRAD-ONSITEs conceptual model does not support flow through relatively impermeable substructures, while basement substructures that remain at the time of license termination may act as resistive flow barriers. Additionally, the RESRAD-ONSITE computer code does not support evaluation of various source-to-well geometries that may be more appropriate considering the final configuration of site structures at the time of license termination. Limitations of the RESRAD-ONSITE computer code with respect to simulating hydraulic barriers and complex geometry assumptions should be evaluated to ensure that dose is not underestimated. For example, HDI could use a more sophisticated model capable of modeling the expected conditions at license termination to develop DCGLs or show that the RESRAD-ONSITE modeling is conservative (i.e., leads to higher doses). Alternatively, the NRC staff could review the modeling in more detail to ensure that dilution is not overestimated in the analysis. HDI should provide their RESRAD input and output files for review along with additional justification for the approach taken.