ML24030A747
| ML24030A747 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  (DPR-072) |
| Issue date: | 02/13/2024 |
| From: | Jack Parrott Reactor Decommissioning Branch |
| To: | Reid B ADP CR3, Crystal River, FL |
| Shared Package | |
| ML24030A740 | List: |
| References | |
| EPID L-2022-LLA-0194 | |
| Download: ML24030A747 (1) | |
Text
CR3 LTP Audit Summary of Topics December 4-8, 2023 Page 1 of 36 Attachment Compliance with Radiological Criteria for License Termination (CRCLT)
No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 1a FSS 12b Clarify the approach to demonstrating compliance with the 10 CFR 20.1402 dose limit for an individual who is exposed to the following sources of radioactivity while residing onsite:
Surface soil Subsurface soil Pavement-covered areas and shallow concrete slabs Buried piping Buried structures Groundwater Fill material.
Explain the approach for incorporating the dose contribution from the insignificant ROCs contributing less than 10% of the dose to their respective DCGL.
NRC and licensee staff discussed that the surface soil DCGLs and building structure DCGLs are each based on the entire 25 mrem/yr dose limit. NRC staff indicated to the licensee that those DCGLs do not account for dose contributions from other contaminated media that a hypothetical receptor (e.g., resident farmer) could be exposed to.
NRC staff indicated that the licensee could reference NUREG-1757 Vol. 2, Rev. 2, Section 2.7 for guidance on how to account for multiple sources of contamination during DCGL development.
This discussion topic resulted in the issuance of CRCLT RAI-1 Approach to Dose Criterion Compliance Demonstration.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 2 of 36 Attachment 2a Discuss the availability of the RESRAD-ONSITE and RESRAD-BUILD model input and output files for the following analyses:
DCGL calculations for each ROC Sensitivity analyses for each ROC During the audit the licensee uploaded RESRAD-ONSITE summary files for soil DCGL development to the portal. The NRC staff identified that the soil DCGL values in the RESRAD summary files for some radionuclides do not match the DCGL values listed in Table 5.1 of the LTP resubmittal (e.g., RESRAD-Onsite Summary file CR3_DCGL_H3_
SUMMARY
.REP generated on February 13, 2022).
The licensee did not provide summary files for the sensitivity analysis for soil DCGLs. The NRC staff understands that the licensee intends to revise the soil DCGL dose model to include additional site-specific parameters, which could change the RESRAD-Onsite output files.
The licensee did not provide RESRAD-BUILD summary files from the development of or sensitivity analysis for building surface DCGLs. However, NRC staff learned that the licensee is considering developing other types of DCGLs (e.g., basement DCGLs, buried piping DCGLs). If the licensee develops a new dose modeling approach for structures to remain onsite at license termination, this request will pertain to the summary files for the new model(s).
This discussion topic, in part, resulted in the issuance of CRCLT RAI-2 DCGL Development and Justification for Building Surfaces Left at License Termination and CRCLT RAI-3 Technical Justification for Parameter Selection for Soil Dose Model.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 3 of 36 Attachment 3a Clarify the plan to characterize the depth of soil contamination, including the criteria that will be used to determine when the characterization depth is adequate.
NRC staff learned that the licensee intends to investigate the top 6 inches of soil for characterization purposes. If (1) the licensee finds no contamination on the surface, and (2) if no subsurface source exists, the licensee will not further characterize soil into the subsurface.
NRC staff understand that the licensee intends to provide their approach to surveying only the top 6 inches of soil unless certain criteria are met (e.g., a potential subsurface source exists). This can be accomplished in a revision to Chapter 5 of the LTP to explain the approach and discuss the specific criteria for determining subsurface samples are needed. This discussion topic, in part, resulted in the issuance of SC RAI-1 Site Characterization.
Additionally, NRC staff understands that the licensee intends to update the description of the QA/QC program in the LTP to indicate whether they will perform a limited number of subsurface samples in some areas, even if criteria for completing subsurface characterization are not met. The NRC staff also understands that the licensee intends to replace wording in LTP Section 5.4.3.2 regarding sampling up to a depth of 1 meter with criteria for determining the appropriate depth of soil characterization.
3b Clarify the basis for the contamination depth in models used to calculate soil DCGL values, including supporting sensitivity analyses.
The NRC staff clarified that the "contaminated zone thickness" parameter in RESRAD-ONSITE should be based on the depth of soil contamination at the site.
This discussion topic, in part, resulted in the issuance of CRCLT RAI-2 DCGL Development and Justification for Building Surfaces Left at License Termination and CRCLT RAI-3 Technical Justification for Parameter Selection for Soil Dose Model.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 4 of 36 Attachment 4a Clarify the process for selecting the following in sensitivity analyses for each dose model:
Physical parameters to represent with stochastic distributions.
Parameter distributions to correlate.
Values of correlation coefficients The NRC staff learned that the licensee did not have access to additional information about the selection of parameters to represent with stochastic distributions, which parameters to correlate, and the values of correlation coefficients used in the sensitivity analyses for soil and building DCGLs.
The NRC staff indicated that the NRC staff could evaluate (1) whether the information in Enclosure 8 of the LTP was sufficient to reproduce the licensees sensitivity analyses; (2) whether representing additional parameters stochastically changed the sensitivity analysis results; and (3) whether changing the values of correlation coefficients or correlating additional parameters changed the sensitivity analysis results. Because the licensee described plans to change the RESRAD-Offsite model later in the audit, these NRC actions cannot take place until the NRC staff receives the new model input from the licensee.
5a Clarify the following information related to sorption of radionuclides to site soil:
whether berm soil can be represented by a more specific soil type than the generic soil type whether surface areas described as sandy soil underlain by limestone can be delineated whether additional information is available to support the determination that the generic soil type represents site conditions."
NRC staff learned that the licensee does not currently have additional bases for the modeled soil sorption coefficients beyond the information presented in the LTP (i.e., generic values were used because of the variety of soil types onsite (sandy soil, limestone, fill material)).
The NRC staff understands that the licensee intends to provide an explanation of whether using sorption coefficients for generic soil is representative or conservative based on the soil types expected to be onsite at license termination.
This could be accomplished in Enclosure 10 of the LTP.
6a Expand upon the technical justification (i.e.,
supporting analysis) for the selection of the building occupancy scenario as the most conservative/bounding scenario for backfilled basement substructures and embedded piping, as stated in the LTP.
During audit discussions, the NRC staff and the licensee concurred that the building occupancy scenario is not a realistic exposure scenario for basement structures and buried piping, since no buildings will remain at grade upon license termination. The licensee discussed that a person would not physically be in the building substructure since the basement will be backfilled. However, the licensee indicated that it may develop a new dose modeling approach for basement structures and buried piping.
This discussion topic, in part, resulted in the issuance of CRCLT RAI-2 DCGL Development and Justification for Building Surfaces Left at License Termination.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 5 of 36 Attachment 7a Clarify which DCGLs the licensee will use in the field for FSS? In other words, what are the Operational DCGLs? Will the LTP resubmittal include these Operational DCGLs and technical justification?
NRC staff explained that the term Operational DCGL is highly defined by the licensee in the LTP and has varied from site to site in the past. Some licensees have developed Operational DCGLs based on an a priori fraction of the 25 mrem/yr dose limit from each source term when multiple contaminated media are present. Others have used Operational DCGLs to add a safety margin from the 25 mrem/yr dose limit.
The licensee explained their definition that Operational DCGLs are those that are compared to scanning results after accounting for all ROCs and all pathways.
NRC staff learned that the licensee is planning to develop one set of DCGLs for soil and possibly apply modifiers to that set of DCGLs for other contaminated media (e.g., basement structures, buried piping). The licensee does not intend to create an additional set of Operational DCGLs. NRC staff understand that the licensee will provide the approach for developing soil DCGLs, DCGL values for each radionuclide of interest, a new list of radionuclides of concern, possible modifier values for other contaminated media, sensitivity analysis, and the approach to account for insignificant contributors.
Depending on the licensees development of and justification for the soil DCGLs, this discussion topic may be related to the questions asked in CRCLT RAI-1 Approach to Dose Criterion Compliance Demonstration.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 6 of 36 Attachment Hydrology and Groundwater (HGW)
No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 1a 2a Dose due to existing groundwater contamination A discussion is needed on the completeness of DQOs for groundwater monitoring and inputs needed for FSS dose calculations. DQOs should address all the site-specific ROCs listed in LTP Table 5-1, a sampling plan as appropriate for those radionuclides, the approach for estimating the maximum concentration in the groundwater, period of time over which trends in data will be evaluated, and the method for accounting for the distance from likely sources to concentrations in monitoring wells.
In addition, the discussion should include a description of the calculation to determine the dose from groundwater contamination, if any, that exists at the time of license termination.
Clarify the meaning of measurement results of radionuclides in groundwater reported as U or LLD in the LTP and AREORs and described in the ODCM.
Discuss how the reported laboratory results are consistent with the MARLAP guidance in NUREG-1576, Chapter 20, or provide justification for not following the guidance.
Staff understands that the licensee will take the approach of demonstrating that all (19) radionuclides, except tritium, in the site-specific suite of radionuclides will be below the critical limit (detection decision) in the uppermost saturated zone at the site. For tritium, staff understands that the licensee intends to develop support for designating tritium levels as background.
Licensee described the meaning of U (undetected), LLD, and variety of other terms in the LTP, annual monitoring reports, and laboratory reports. Licensee provided several laboratory procedures documenting the methodology for laboratory measurements. Staff pointed to guidance on reporting sample results in NUREG-1576 (MARLAP). Staff understands that the licensee intends to confirm if their reporting of results is consistent with MARLAP for the detection decision and quantification of low levels of radionuclide.
In parallel with the above discussions for both items in this group, staff understands that the licensee intends to pursue an alternative approach for dose due to existing groundwater contamination. Staff understands that the licensee intends to assess the possibility of demonstrating that the saturated groundwater at the site is impacted by saltwater intrusion, and thus, would not meet the definition of an aquifer by the state of Florida. If staff finds the demonstration adequate, then staff will not review the dose due to existing groundwater contamination nor the reporting details for low levels of radionuclides in groundwater. The licensee and staff discussed that groundwater contamination should still be characterized even if the saturated groundwater does not meet the definition of an aquifer.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 7 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 3a Discuss the relationship between the datums used in the set of LTP submittal documents. The discussion would be facilitated by one or two cross-sections that illustrate the relationships of features and components between the survey units on the berm of the power block and survey units outside the area of the berm. These cross-sections should include ground surface, basements of subsurface structures that will remain, geological or hydrogeological layers, and typical or average groundwater table elevations.
Discuss the datum that is planned for all elevation-related FSS information (e.g., subsurface sampling, excavations).
The licensee confirmed the relationship between the three vertical datums used at the site for different technical areas. Staff understands that the licensee intends to primarily utilize the plant datum, and intends to clarify the relationship when other datums are used (such as local building coordinates, subsurface sampling elevations, or groundwater conditions). To support the conceptual site model, staff understands that the licensee intends to develop a cross-section that integrates the features listed in the discussion topic.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 8 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 4a 5a 6a 7a 8a Inputs for groundwater pathway in dose models Clarify how the hydrogeological parameters in the berm area relate to the conditions outside the berm of the CR3 plant area, and vice versa, or that dose is not underestimated for survey units in either area.
Discuss the reasonableness of the CZ and UZ parameters of precipitation and hydraulic conductivity in the soil dose model for representing site conditions, including the coherency of the hydraulic conductivity with the coefficients for evapotranspiration and runoff. Also, discuss why the upper end of the precipitation as used in the soil dose model in terms of its contribution to dilution at the wellbore in RESRAD.
Clarify the supporting bases for several hydrological soil dose model inputs.
Discuss the analysis that produced the large value of hydraulic conductivity that is being applied to the soil dose model. Discuss how the selected inputs for hydraulic gradient are consistent with groundwater conditions at the site, particularly for survey unit areas.
Clarify the support for hydrogeological parameters leading to significant wellbore dilution for the soil dose model.
The licensee explained that parameter values reflected properties or conditions of both berm and non-berm areas; i.e., a composite representation. The licensee further explained their conceptual model for the berm area and how it differed from that of the general site conceptual model. Staff understands that the licensee intends to evaluate parameter values that might not apply both to the berm and off-berm areas (e.g., UZ thickness, hydraulic conductivity, gradient) and determine if they are non-conservative as applied to either berm or non-berm areas.
The licensee clarified that the berm was constructed of crushed limestone, which is significantly different than the unsaturated zone media in areas surrounding the berm. The licensee also described the configuration of the curtain wall below the main structures; the curtain wall fully was enclosed on the sides and the bottom. The licensee mentioned that some small amount of designed leakage occurred. Considering the crushed limestone and curtain wall, the licensee described a separate conceptual model for flow and transport in the berm area and the basis for the choices of inputs for unsaturated zone (vertical) hydraulic conductivity and precipitation.
Staff understands that the licensee will consider the justifications for RESRAD input parameter values in light of the RESRAD abstracted model and the porous media of the berm.
Licensee provided H&A TSD #134300 on the portal, which was cited in the LTP as documenting the supporting bases for selected RESRAD-ONSITE input parameters. The document contains some additional information for several parameters, however, the gradient information was TBD. Staff understands that the licensee intends to update the basis for the selected gradient value, including justification for why the gradient is appropriate for all areas of the site under all tidal conditions.
[7a] Licensee explained that the choice to use default gradient was driven by wide range of gradients found across the site, and that the
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 9 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path gradients change dependent on tidal conditions. Staff understands that the licensee intends to evaluate appropriateness of the large flux value produced by large hydraulic conductivity and moderate gradient for the saturated zone at the site. Staff understands that the licensee intends to reassess sensitivity results if parameter values change significantly.
[8a] The licensee and staff discussed the parameters that affect the calculation of wellbore dilution in RESRAD-ONSITE. Staff provided a link to additional descriptions of the dilution calculation contained in an Interim Staff Guidance (ML23177A612). Staff understands that the licensee intends to evaluate and justify the parameters that affect borehole dilution for CR3 in RESRAD-ONSITE.
[All] In parallel with the above discussion for all the items in this group, staff understands that the licensee intends to pursue an alternative approach for the groundwater pathway in CR3 dose models. Staff understands that the licensee intends to assess the possibility of eliminating the groundwater pathway by demonstrating that the saturated groundwater at the site is impacted by saltwater intrusion, and thus, would not meet the definition of an aquifer by the state of Florida. If staff finds the demonstration adequate, then staff will not review the values or bases for hydrological input parameters used for the groundway pathway in RESRAD-ONSITE.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 10 of 36 Attachment Site Characterization (SC)
No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 1a 1b For survey unit classification:
Discussion of classification of downgrading and previous remediated survey units.
Discuss the methodology that would be used to inform the basis to downgrade survey unit classification.
NRC staff and the licensee discussed the classification and reclassification of survey units, including those previously remediated.
NRC staff learned reclassification of survey units will not occur without NRC approval prior to implementation. However, the licensee explained they do not consider classification of soil beneath a demolished building to not constitute "reclassification." As an example, NRC staff and the licensee discussed survey unit EOCZ-04, which was remediated during the operational phase of the site. In addition, the licensee discussed WOCZ-03 as an example of downgrading a survey unit classification.
The licensee discussed the history of the RMSW-D Tank, including the contamination incident, to include remediation activities.
This discussion topic resulted in the issuance of RAI SC-1, Site Characterization.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 11 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 2a Describe surveys conducted and their results, or plans for the characterization building interiors, building basement structures, embedded piping, backfill material, and subsurface soils.
NRC staff and the licensee discussed the importance of characterization data in determining radionuclide mixtures, insignificant contributor (IC), and input to dose modeling. The NRC staff learned the licensee completed additional sampling in outdoor areas and buildings.
Limited subsurface samples were collected from the BERM area with no embedded piping characterization completed to date. Additional survey and sampling planned includes core sampling in the Reactor Building, embedded piping sampling, and supplemental survey and sampling of previously surveyed outdoor areas. The NRC staff understands, for existing characterization data, the licensee anticipates providing supplemental information to Chapter 2 of the LTP by the first quarter of 2024. The NRC staff clarified if only Class 1 areas remain to be characterized, receiving supplemental data will not hold up the approval of the LTP.
The discussion topics above resulted in the issuance of RAI SC-1 Site Characterization. The NRC staff was tasked with evaluating the additional characterization data needed to support the LTP review and approval. The NRC staff communicated this information in RAI SC-1, Site Characterization.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 12 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 2b 2c Concerning characterization survey methodology:
Explain the process for conducting site characterization measurement and sampling and sufficiency of these results for determining input to the FSS design and radionuclide mixture/fractions.
Discuss the results of gamma scan surveys conducted on impacted open land areas and how the results of these scans were used to identify areas of biased sampling.
NRC staff and the license discussed the methodology used for conducting characterization surveys including random or systematic sampling, judgmental sampling, determination of sample locations and numbers, scanning surveys, and instrument sensitivities. The licensee informed NRC staff characterization surveys were not performed to the rigor of an FSS, and at present, data will not be included in the FSS analysis. NRC staff emphasized the importance of the characterization for classification of areas, including soils under buildings and providing justification for these decisions.
The NRC staff learned there were no gamma scan surveys during site characterization surveys of impacted open land survey areas. For the purposes of identifying judgmental sampling locations, the licensee focused on low-lying areas, ditches, areas of concern identified in the historical site assessment, and professional judgment. The NRC staff learned gamma scan surveys were conducted during surveys of non-impacted areas and some previously surveyed open land areas (e.g.,
CHAR-09, WOCZ-03).
This discussion topics resulted in the issuance of RAI SC-1 Site Characterization. Upon receipt of outdoor area gamma scanning surveys, NRC staff will review the information and provide the licensee with any questions concerning these surveys.
2d For land areas, there were only twelve out of 123 characterization samples sent for HTD analyses with the samples were selected randomly. Explain how analyzing <10% of the total land area samples for HTD radionuclides is adequate to assess HTD contributions for land areas. Explain why the samples were analyzed for only a subset of the HTD radionuclides contained in Table 2.4, CR3 Site-Specific Suite of Radionuclides of Concern.
The licensee clarified the results for 117 samples (4 duplicates) are available in Enclosure 20, Table 3-3, including analysis for the full suite of radionuclides.
There is no further action for NRC staff or the licensee at this time.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 13 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 2e Describe how the results of ongoing characterization efforts will be communicated to NRC staff.
NRC staff understand the licensee intends to provide supplements to existing characterization data in the LTP as they become available.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 14 of 36 Attachment Plan for Radiological Site Remediation (PRSR)
No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 1a 1b 1c 1d Describe the justification for applying 2014 rather than inflated values for the averted dose and value of statistical life, including the use of sensitivity analysis evaluating low, best, and high estimates.
Explain the rationale for using of a 7% discount rate parameter as a conservative approach when calculating the ALARA limits.
Discuss the approach for selecting 1 m2 as the survey unit area and 1 m3 as the waste volume in the generic cost/benefit analysis.
Explain the rationale for using only Cs-137 and Co-60 verses all the radionuclides of concern in the generic ALARA evaluation.
The licensee provided a revised ALARA evaluation for NRC staff evaluation for soil excavation and scabbling in "Crystal River Unit 3 Nuclear Generating Plant ALARA Evaluation, Rev 1, Draft," which included several updated inputs to the present worth of the future collective averted dose (PW(ADCollective)) calculation. These revisions included the necessary information for the staff to continue their review; however, the consideration of a zero-discount rate was not included.
NRC staff understand that the licensee intends to revise the draft ALARA evaluation to include:
An analysis for a zero-discount rate and select the discount rate used in the ALARA with justification for the value selected.
A revision of the text and inclusion of a step for determining the ratio of the cost of remedial actions to the value of the averted dose.
Additionally, the NRC understands the licensee intends to finalize the draft ALARA evaluation report, update the discussion in Chapter 4 of the LTP, and replace or supplement the attachment to Chapter 4.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 15 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 1e Clarify why the LTP provides only a generic ALARA analysis for building surfaces. Clarify what remediation activities are considered as a part of this analysis and why other remediation activities dont require an ALARA evaluation.
When are survey unit specific ALARA evaluations conducted and how they are documented? Describe any alternative disposal paths under 10 CFR 20.2002 being utilized for soils.
NRC staff learned the licensee no longer plans to conduct survey unit specific ALARA evaluations instead focusing on a generic ALARA analysis. A soil excavation and scabbling scenario were considered for the generic evaluation with the licensee inquiring about other generic scenarios that should be considered.
NRC staff evaluated the generic scenarios and recommended the licensee benchmark their generic ALARA scenarios against other license termination plans to determine if similar scenarios are applicable to the Crystal River site.
Additionally, NRC staff learned the licensee will not use alternative disposal paths under 10 CFR 20.2002 with all their waste shipped to the Waste Control Specialists.
1f Clarify the meaning of remediation of soils beyond the DCGLs. Does the licensee mean remediation below the DCGLs is not likely to be cost effective in the LTP Section 4.4, ALARA Analysis, and the Crystal River Nuclear Generating Plant Generic ALARA Evaluation.
NRC staff explained in Section 4.4, ALARA Analysis, and the Crystal River Nuclear Generating Plant Generic ALARA Evaluation, the text uses the phrase beyond the DCGLs. The licensee clarified they meant below the DCGLs.
NRC staff understand the licensee intends to update the text in the LTP to read below the DCGLs.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 16 of 36 Attachment Final Radiation Survey Plan (FSS)
No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 1a 1b 1c 1d 1e For alpha/beta instruments, Table 5.8 presents an efficiency. Clarify of the type of efficiency included in Table 5.8 (e.g., instrument efficiency or total efficiency.)
Explain how the instrument efficiency (ei) will be adjusted for in conditions where the source term in the field is larger area than the calibration source used for determining the source-to-detectors distance in Table 5.9.
What radionuclide mixture is assumed for determination of the weighted instrument efficiency (ei)? Explain how the instrument efficiency will be adjusted for HTD radionuclides or variable mixtures for the ROCs included in Table 2.4, CR3 Site-Specific Suite of Radionuclides of Concern.
What radionuclide mixture is assumed for determination of the weighted source efficiency (es)?
Explain how the source efficiency will be adjusted for HTD radionuclides or variable mixtures for the ROCs included in Table 2.4, CR3 Site-Specific Suite of Radionuclides of Concern.
Explain the selection of 1.38 as a sensitivity index (d)
NRC staff emphasized a priori static and scan minimum detectable concentrations (MDCs) should be directly comparable to the surface and soil DCGLs. NRC staff requested all inputs for the static and scan MDC equations to facilitate validation of the licensee calculations. NRC staff learned the licensee no longer intends on applying a source-to-detector distance efficiency to / efficiencies since measurements will be taken at contact or near-contact with the surface. Additionally, the licensee will calculate and apply weighted instrument efficiencies based on site wide, building specific, or survey unit specific radionuclide mixtures. The NRC staff and licensee discussed the appropriateness of the index of sensitivity (d) to the site and alternatives to the current value.
This discussion topic resulted in the issuance of RAI FSS-3, Instrument and Laboratory Analysis Minimum Detectable Concentration.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 17 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 2a 2b 2c 2d 2e Identify what advanced technologies are under consideration, their proposed use, and the criteria for providing a technical basis document for review.
Clarify the proposed uses of ISOCS and the criteria for providing a technical basis document for review.
Include this discussion of instrument sensitivity and calibration.
Explain how the HTD radionuclides will be accounted for in the in situ and advanced technology measurements.
Discuss the NaI detector or ISOCS methodology for identifying the potential presence of subsurface contamination (i.e., greater than 15 cm in depth) and the triggers for further investigation. How will this methodology be used with excavations (e.g., with or without overlying soil)?
Discuss the methodology for use of ISOCS for scanning.
NRC staff learned that the licensee will not use advanced technologies or ISOCS. NRC staff clarified for the licensee that advanced technologies are those technologies not routinely used by the industry for area surveys; however, there is a process for notifying the NRC when new technologies are considered.
NRC staff understands that the licensee intends to update the LTP to remove references to ISOCS and advanced technologies.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 18 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 3a 3b 3c For onsite gamma spectroscopy, for all measurement media and geometries discuss how the MDCs will meet the applicable DCGLs.
For onsite alpha and beta analyses, for all measurement media and geometries discuss how the MDCs will meet the applicable DCGLs.
For the vendor laboratory, describe the analysis type, technique, method, and MDCs by media.
NRC staff emphasized the need for a priori onsite and offsite analytical laboratory MDCs directly comparable to the DCGLs. For onsite analyses, this information could be included in existing instrument sensitivity tables. For offsite sample analysis, the NRC staff recommends the licensee include in the LTP the MDCs by analysis type, technique, method, and media used. NRC staff learned the onsite laboratory is required to meet 10-50% of the DCGL and the offsite laboratory to meet 10-50% of the DCGL for easy to detect radionuclides and 1-5% of the DCGL for HTDs.
This discussion topic resulted in the issuance of RAI FSS-3, Instrument and Laboratory Analysis Minimum Detectable Concentration.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 19 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 5a 5b 5c 5d How are scanning ILs calculated such that a gross count rate observed during scanning is equated to the DCGL values designated for Class 1 and Class 2 survey units?
Explain the basis for the 3-sigma above the mean as an investigation level for Class 1 direct measurements. How is this statistical parameter determined for use as an IL and how have these values have been verified to be less than the DCGLEMC?
How is detectable over background established for Class 3?
Clarify in Table 5.4, Investigation Levels, Table 5.7, Investigative Actions for Individual Survey Units, Section 5.3.6.4, Remediation and Reclassification, Section 5.4.5.1, and other areas of the LTP discussing investigation levels whether DCGL refers to DCGLw.
NRC staff and the licensee discussed investigation levels (ILs) and how they are applied in the field. NRC staff learned the licensee will include values comparable to field instrument readings in a revision of Table 5.4, Investigation Levels. The NRC staff clarified that the use of 3-sigma above the mean or detectable above background, if used as scan or static ILs, will require an explanation of the derivation. NRC staff also recommended the license consider specifying the appropriate DCGL (DCGLW or DCGLEMC) for ILs in Table 5.4.
NRC staff understand the licensee intends to update Table 5.4, Investigation Levels in the LTP to reflect ILs implemented during FSS and will evaluate updating DCGL to include the appropriate subscript. NRC staff understand the licensee intends to provide justification and explanation of the derivation of ILs applying statistical parameters or detectable above background.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 20 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 6a-i ii iii iv v
Describe how are the actual minimum detectable concentration for scanning surveys where HTD radionuclides are present will be calculated.
Describe how HTD ROCs will be accounted for during scanning and direct measurements in the absence of the use of surrogate radionuclides.
Describe the sampling protocol for measurement of HTD radionuclides, including the selection of random or systematic and biased samples for HTD analysis and the collection of sufficient samples to demonstrate a statistically significance.
Explain how the instrument efficiency is determined for mixtures containing HTD radionuclides.
Discuss the ROC mixtures identified in various media.
NRC staff provided an overview of the expectations concerning measurement and sampling of HTD radionuclides, and their consideration in MDC calculations. The current LTP indicated that the licensee does not plan to use surrogate ratios. NRC staff learned the licensee is evaluating the use of Cs-137 or all gamma emitters as surrogates for HTD radionuclides. NRC staff emphasized if the licensee plans to forego the use of surrogates 100% of the FSS samples would require analysis for all ROCs.
This discussion topic resulted in the issuance of RAI FSS-2, Surrogate Radionuclides.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 21 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 6b-i ii iii For gross activity DCGL and measurements:
The LTP did not specify whether both alpha and beta measurements will be made on structure surfaces during characterization or for the FSS.
What are the requirements for alpha scans? If only beta measurements will be performed, describe how the release criteria for alpha emitting ROCs will be demonstrated.
Clarify whether both alpha-plus-beta measurements or independent gross alpha and gross beta measurements are used to develop the gross activity DCGLs, and the method for calculation of the DCGLs. For example, will a gross activity DCGL be developed based on fractional amounts of ROCs and alpha-plus-beta measurements, or will independent gross beta and gross alpha DCGLs be developed based on fractional activity and then the unity rule be applied to the alpha and beta measurements?
Explain how the HTDs will be accounted for in a gross activity DCGL in lieu of the surrogate method for surface activity measurement data assessments.
How will the contributions from HTDs be accounted for in application of the unity rule, particularly since limited data is available on HTD contributions to the total source term?
If the new radionuclide distribution data found to be more appropriate for use results in an increased DCGLGA, describe the process that will be followed.
NRC staff and the licensee discussed the derivation of gross activity DCGLs (DCGLGA) and their application. The NRC staff requested clarification on measurement types used to determine residual radioactivity on structures (e.g., alpha, beta, alpha/beta). The NRC staff learned the licensee is currently evaluating their survey techniques and gross activity DCGLs. Updates to the DCGLGA will include the consideration of recent radionuclide mixtures, including HTDs. The licensee currently plans to use independent alpha and beta measurements using weighted efficiencies and separate gross alpha and beta DCGLs. The NRC staff asked for clarification on DCGLGA reevaluation in the event of a new radionuclide distributions.
NRC staff understands the licensee intends to update the LTP to:
Clarify the survey types used for buildings structures (e.g.,
alpha/beta scans and direct measurements) and the instrument mode (alpha only, beta only, or alpha plus beta) used to determine alpha and beta activities.
Describe how gross activity DCGLs will be calculated and how gross alpha and beta instrument readings will be correlated to these DCGLs.
Remove or supplement the discussion concerning reevaluation of the DCGLGA with new radionuclide distribution data.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 22 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 7a-i Describe when turnover surveys are used and the intended use of these data. How do turnover surveys differ from remediation surveys?
The NRC staff learned turnover surveys are conducted post-remediation to determine when a survey unit is ready for FSS for Class 1 and Class 2 areas. Turnover surveys statistics may be used to provide input data to the FSS design.
There is no further action for NRC staff or the licensee at this time.
7a-ii Explain what is meant by equivalent evaluation in Sections 5.1.3.2, Survey Preparation and the methodology for conducting these evaluations.
NRC staff learned the licensee will not use equivalent evaluations.
NRC staff understand the licensee intends to remove references to equivalent evaluations from the LTP.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 23 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 7a-iii Discuss the survey methodology used to support the contamination control program, including verification of isolation and controls and evaluation of haul paths.
During the site tour, NRC staff learned Crystal River used dust suppression, containment structures with negative ventilation, and structure decontamination to free release levels, where possible, to control the spread of contamination to the environment from decommissioning activities. Additionally, the licensee has a routine follow-up surveillance program conducted for previously released areas.
NRC staff and the licensee discussed maintaining isolation and controls in areas with active non-nuclear operations at the Crystal River Energy Complex (CREC). NRC staff learned traditional isolation of areas (e.g., fences, ropes) following FSS may not be possible. The licensee explained there is a process in place to disseminate information on postings and other controls to CREC personnel. The licensee informed NRC staff portions of the isolation and control program may be discontinued on a risk-informed basis following confirmatory surveys.
NRC staff understand the licensee intends to supplement Section 5.2.4.4, Isolation and Control Measures to expand on the contamination control measures implemented at the site.
Additionally, NRC staff understand the licensee intends to provide isolation and control procedures and an explanation of the dissemination of isolation and control protocols to the CREC for NRC staff review.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 24 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 7b-i ii For discrete radioactive particles (DRPs):
Describe the criteria where adjustments to DQOs and survey plans will be made for discovery of hot particles and/or DRPs. How will these incidents be documented, including the material origin, cause(s) for the materials presence, and the extent of the condition?
Explain how the survey and sampling methodology will be modified in the event DRPs are found, including how the physical and radiological characteristics of the DRPs will be determined. For which survey units will revise survey methodologies be implemented when DRPs are identified.
The NRC learned the licensee benchmarked their radiological control program with other sites, such as Zion, who had experience with DRPs. As a result, Crystal River has improved the process for managing hot particles and DRPs in all Radiological Control Areas by focusing on controlling the generation at the source (e.g.,
containment structures, fixative, encapsulation, capping, vacuuming). In addition, the licensee conducts routine surveys for hot particles and DRPs. When hot particles or DRPs are found, an investigation is conducted and documented in the corrective action program.
NRC staff understand the licensee intends to supplement the information in Chapter 2 of the LTP taking credit for operational practices and surveys conducted to control the generation of DRPs.
During the audit NRC staff informed the licensee of an information notice in draft, which contains insight on how to address DRPs. The NRC staff communicated the need for additional explanation on how DRPs will be addressed during the FSS process and how DRPs events will be documented. The discussion should include the cause and extent of the condition (physical and radiological characteristics of the DRPs). Clarity related to the conditions for adjustments to the Data Quality Objectives (DQOs) and survey plans and the survey methodology employed following DRP discovery (e.g., radionuclide identification, scan survey approach and coverage, consideration for adjacent survey units, remediation) would help inform the staffs review.
NRC staff understand that the licensee intends to include in the LTP a discussion of DRP survey and sampling protocol, and the criteria for adjusting their DQOs and survey plans when DRPs are identified.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 25 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 7b-iii Describe the method proposed to evaluate dose from DRPs NRC staff and the licensee discussed the potential need for additional information on the method for assessing potential dose from DRPs should they be found during FSS or confirmatory surveys.
8a-i For basement structures, what are the types of surface activity measurements to be conducted (e.g., alpha, beta, a combination)? Explain how the surface activity release criteria will be expressed for comparison to a gross activity DCGL.
NRC staff understand that the licensee intends to revise the LTP and/or Technical Basis Documents (TBDs) to include information on their approach to surveying below grade structures. This approach will include information about their surveying techniques for below grade structures prior to backfill, the types of measurements (alpha, beta, gamma) as well as a narrative of how the surface activity will be compared to gross activity DCGLs. The gross activity DCGLs will be developed either from the current building surface DCGLs OR new substructure DCGLs that the licensee may develop.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 26 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 8a-ii Discuss the technical justification to support the basis for selecting a volumetric concrete sample of 10 mm in thickness after removal of the surface layer for subsurface structures.
NRC staff learned that the licensee referenced a 10 mm depth from guidance in NUREG 1757 Appendix H Criteria for Conducting Screening Dose Modeling Evaluations, which applies to determining when screening criteria are appropriate. The licensee has been implementing a practice during characterization surveys to scabble the uneven paint and epoxy from surfaces (e.g., basement floors) of approximately 10 mm. NRC staff understand that the 10 mm thickness does not apply to volumetric sampling but rather the thickness of material that will have been removed from the surface at the time of FSS. The licensee stated that its current practice is to continue with volumetric sampling (core boring) if and when contamination is found on the surface.
NRC staff understand that the licensee intends to:
Evaluate verbiage in Chapter 5 of the LTP related to 10 mm thickness and scabbling and determine if that language needs to be included for FSS, Include more detailed information about its proposed use of core boring to assess volumetric contamination, including the sample approach, laboratory procedures to analyze the cores (e.g., cutting into discs at certain depths), etc., and Evaluate the language in Chapter 2 of the LTP related to core boring for the purposes of site characterization to inform new language in Chapter 5.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 27 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 8a-iii Section 5.4.3.2, Volumetric Concrete Measurements states Volumetric sampling of contaminated concrete, as opposed to direct measurements, may be necessary if the efficiency or uncertainty of the gross beta measurements is too high. Explain how the efficiency being too high is an issue.
NRC staff learned that the licensee's initial position of the efficiencies being too high would be a result of the uneven paint/epoxy on building surfaces. However, since the paint will already have been removed from the building surface at the time of FSS, the licensee does not plan to employ this approach.
NRC staff understand that the licensee intends to determine if the verbiage related to the efficiency of gross beta measurements being too high in Section 5.4.2.4 will be removed from the LTP.
8a-iv Discuss the technical justification (including pathway analysis) for using building surface DCGLs as a conservative approach for subsurface applications (i.e., basement structures, piping).
NRC staff learned that the licensee is considering developing other types of surface DCGLs (subsurface structures as opposed to building surface). NRC staff and the licensee discussed different exposure scenarios related to building surface vs. subsurface structure dose modeling. NRC staff cited NUREG 1757 Appendix J for examples of exposure scenarios and applicability of RESRAD to subsurface modeling.
This discussion topic, in part, resulted in the issuance of CRCLT RAI-2 DCGL Development and Justification for Building Surfaces Left at License Termination.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 28 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 8a-v For concrete measurements, explain the criteria for determining at what point (depth) contamination can no longer be adequately assessed by surface activity measurements and should be replaced by volumetric measurements, particularly in areas subject to neutron activation. How will compliance with release criteria be demonstrated in the event volumetric concrete samples replace surface activity measurements? Describe what volumetric sampling technique(s) would be used.
NRC learned that in areas of activation potential (i.e., in the bioshield), the licensee plans to perform volumetric sampling in the form of core boring. The licensee noted that surface measurement can only detect contamination to a depth of about 10 mm. The licensee noted that when performing volumetric sampling, the licensee would typically take core bores to 1 m.
NRC staff understand that the licensee intends to evaluate their survey procedures and update language in the LTP (Chapter 5) to discuss (1) criteria for depth of volumetric concrete sampling and (2) high-level overview of the sampling plan and technique to investigate neutron activation in concrete.
8a-vi Discuss the approach for assessing the radiological condition of soils adjacent to exterior basement walls and soils beneath basement floor slabs. Particularly for floor slabs, describe the plan to ensure that these soils satisfy release criteria.
The licensee and NRC staff discussed the viability of contamination leakage through building structures e.g. (cracks) that may contaminate the land areas underneath and directly adjacent to buildings. NRC staff learned that the material surrounding basement structures planned to be left onsite is mostly crushed limestone in the berm, as opposed to soil. To date, the licensee has been using professional judgment and historical knowledge (e.g., spills) to perform judgmental surveys of soils underneath buildings.
NRC staff understand that the licensee intends to clarify the approach to soil measurements under and adjacent to building structures for FSS.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 29 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 8a-vii 10b-i Describe the investigation process planned for the crushed limestone surrounding the basements.
Explain how the total dose for backfilled basements will be assessed, particularly in the case where either demolition concrete is used that has not been quantitatively assessed or soil is placed from a Class 2 or 3 area where there may be some residual contamination.
Describe the procedure for scanning and sampling of excavation floor and wall surfaces.
NRC staff learned that the material surrounding basement structures planned to be left onsite is mostly crushed limestone in the berm, as opposed to soil. The licensee clarified that it will not reuse onsite material as backfill but rather plans to use offsite material as backfill. There was a discussion on the definition of backfill, specifically related to native soil (e.g., excavation spoils to be returned to the same area) vs. soil originating offsite. NRC staff acknowledged that soil from an excavation that is replaced in the same location is not considered "backfill" material, based on how the licensee defines the term "backfill" in the LTP. NRC staff discussed the importance of record keeping of actions related to refilling and backfilling excavations of buried material, including position (x, y, z) location for sampling locations.
NRC staff understand that the licensee intends to include its approach to surveying crushed limestone for FSS and evaluate the definition of the term "backfill" in the LTP as it relates to offsite soil vs. replacing native soil from an excavation. NRC staff understand that the licensee intends to evaluate the relevancy of Enclosure 18 (Letter to the State of Florida) to the LTP, specifically with reference to "Specific End State Condition 3" that discusses the reuse concrete debris onsite. NRC staff understand that the licensee intends to include information of the FSS survey plans for excavations prior to backfill, including a commitment to perform FSS commensurate with the level of contamination of the buried material that is being removed.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 30 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 8b-i ii iii iv v
vi vii For buried piping that will remain onsite at license termination, discuss the following:
methodology for determining piping instrumentation sensitivities that are directly comparable to the DCGL, calibration process for instrumentation used in piping surveys, Survey protocol and how the percent survey coverage will be determined for Class 2 and Class 3 piping, sample analysis plan for pipe scale and sediment and smears, how inaccessible areas of embedded and buried piping will be assessed and describe the plans to characterize and release piping if it cannot access areas to be surveyed, Criteria for determining when embedded piping DCGLs are required, and Approach for changing the overall dose compliance if piping DCGLs were to be developed.
NRC staff discussed that the current LTP contains some information on survey techniques for inaccessible areas. NRC staff identified LTP Sections 5.4.4.3 (which references the development of a separate FSS plan) and LTP 5.4.5.4.8 (FSS of inaccessible areas) that include conflicting information on FSS of buried piping. LTP Section 5.3.6.3.2 commits to submitting a technical basis document to develop buried piping DCGLs if certain criteria are met.
NRC staff understand that the licensee intends to evaluate certain portions of the LTP to ensure consistency about information related to FSS of buried piping. The licensee will provide more detailed information on its FSS survey plan and techniques for accessible and inaccessible areas of buried piping. NRC staff understand that the licensee intends to consider the information presented in the discussion topics to inform the language related to the FSS plan in the LTP.
NRC staff discussed the implications of accounting for the dose from developing buried piping to the overall dose compliance equation. This discussion topic, in part, resulted in the issuance of CRCLT RAI-1 Approach to Dose Criterion Compliance Demonstration 9a Describe how radiological surveys and samples would be performed to provide reasonable assurance that plant-derived radionuclides from rubblized concrete used as backfill are detectable.
Include in this discussion how these radionuclides from the concrete debris designated for reuse will be factored into the assigned dose contributions.
NRC staff learned that the licensee does not plan to reuse concrete as backfill. NRC staff understand the licensee intends to remove language related to reuse of concrete or debris from Section 1.3.3 of the LTP.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 31 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 10a-ii Discuss the process for determining when judgmental sampling will be conducted at locations where residual radioactivity is identified during static and scanning measurements.
The NRC staff learned biased sampling of soil during FSS will be based on professional judgement, audible indications, and investigation levels. Any activity found in the top six inches of soil will result in further investigation of the area.
NRC staff understand the licensee intends to provide an update to Section 5.4.3 of the LTP to clarify when judgmental soil samples are collected and the basis for that determination.
10a-v Under what conditions will roadways be surveyed to verify residual radioactivity has not been introduced during ingress and egress activities?
The NRC staff learned that pre-and post-surveys occur along the haul path for major evolutions (e.g., transport of the reactor vessel segments) along with routine periodic surveys. The licensee conducts weekly inspections of the CREC to identify conditions potentially impacting decommissioning and to collect judgmental samples, when necessary. NRC staff learned the coal plant regrades portions of roads on a weekly basis, which presents challenges to FSS in these areas.
NRC staff understand the licensee intends to supplement language in the LTP to discuss the routine surveillance program for the CREC, haul paths, and post-FSS survey units.
10c-i Explain the criteria for performing subsurface soil contamination investigations and how this will be conducted.
The NRC staff learned subsurface sampling is dependent on locations of known spills as indicated in the historical site assessment. The NRC staff informed the licensee subsurface sampling should be considered for areas of known radiological activities, such as the power block.
Actions associated with the topic above are documented under CCRLT-3a.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 32 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 10c-ii Discuss the justification for limiting the maximum depth of planned subsurface soil sampling and investigation to one meter.
NRC staff learned subsurface soil sampling is not limited to a depth of 1 meter. Contamination will be followed until the concentration is below established criteria. For example, at some locations, soil has been sampled down to a depth of 8 to 9 feet.
NRC staff understand the licensee intends to explain the protocol for subsurface soil investigations replacing the LTP language about sampling to a depth of 1 meter with criteria for determining the depth of sampling.
10d-i Explain the measurement and sampling methodology used to ensure soils planned for reuse do not contain residual radioactivity greater than the release criteria. How will sample numbers be determined?
The NRC staff learned from the licensee all soils for backfill will be taken from clean soil approximately 15 miles east of the plant. The licensee conducted an initial survey and sampling campaign to verify the soil was clean; however, no additional sampling is planned. The number of samples was determined based on professional judgment. NRC staff reviewed SMG Off-site Backfill Characterization Worksheet, which contained the survey plan for offsite backfill soils. The procedure indicated the licensee conducted gamma scans to identify areas of elevated activity for further investigation and sampling. In addition, the criteria for use of soil as backfill was based on whether the soil contained residual radioactivity at levels less than those of the offsite background study conducted as a part of the licensees previous partial site release.
The survey plan includes provisions for analysis of the full suite of radionuclides.
NRC staff understand the licensee intends to include a discussion in the LTP on the survey and sampling of offsite backfill soils before use. Additionally, the licensee intends to provide survey and sampling results for offsite backfill soil completed to date.
10d-ii Describe the criteria for determining when a bulk monitoring technical basis will be developed and provided to NRC staff for review.
NRC staff learned the licensee uses bulk monitors such as portal and truck monitors for qualitative screening only. NRC staff understand the licensee intends to remove references to the use of bulk monitoring for soils during FSS from the LTP.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 33 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 11a 11b Define the criteria for use of double sampling, including the classification of survey units for which double sampling will be employed.
Explain how the increase in the probability of a Type I error will be justified for double sampling.
NRC staff learned that the licensee will not conduct double sampling during final status survey. The NRC staff understands the licensee intends to remove references to double sampling from the LTP.
12a 12c 12d Explain whether the licensee plans to perform a secondary evaluation of insignificant contributors to reduce the ROCs further than was originally proposed in the LTP and how this will be performed.
Discuss supporting information obtained from the characterization data results that corroborate the theoretical analysis conducted in Enclosure 5 for determining insignificant contributors.
Describe how the relative nuclide fractions/mixtures are determined, how these fractions will be utilized, and how these fractions will be verified throughout the characterization, remediation, and FSS process.
NRC staff and the licensee discussed plans for further identification and deselection of insignificant contributors. NRC staff learned that the licensee is working on data tables that provide radionuclide fractions. The licensee plans to perform a secondary evaluation of insignificant contributors, which may take weeks to months. NRC staff emphasized the need for a minimum number of samples for statistical significance in determining ICs and the need for continuing verification of ICs through the completion of FSS (i.e.,
typically 10%).
This discussion topic resulted in the issuance of RAI FSS-1 Insignificant Contributors.
12e Explain the process for considering radionuclide results with values less than the minimum detectable concentration and negative values in the determination of radionuclide mixtures.
NRC staff learned the licensee plans to apply the Oak Ridge Institute for Science and Education method for handling negative and less than MDC values when determining radionuclide fractions.
The NRC staff discussed the applicability of this approach for the Wilcoxon Rank Sum test, highlighted the need for all negatives to be averaged as zeros when considering dose.
NRC staff understand the licensee intends to provide a discussion of how negative and less than MDC values are addressed when determining radionuclide mixtures.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 34 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 13a 13b Please discuss the following information related to volumetric concrete measurements:
Volumetric sampling results from characterization efforts including but not limited to the January 2020 Scoping Surveys Validity of this surveying approach for FSS purposes, including technical precedent, if any.
NRC staff learned that the licensee has not performed volumetric concrete measurements at Unit 3. The information referenced in the January 2020 Scoping Surveys was related to limited volumetric measurements taken from Units 1 and 2. Throughout characterization efforts and during FSS, the licensee has been and will apply MARSSIM techniques for volumetric cores with direct and scanning measurements.
There is no further action for NRC staff or the licensee at this time.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 35 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path 14a 14b 14c 14d 10a-i The LTP notes that soil DCGLs are applicable to surveys of pavement-covered areas and shallow concrete slabs, please clarify the following:
Expand upon the claim that the exposure scenario is most similar to direct radiation from surface soil. Discuss dominant pathways and other pathway contributions from applying the conceptual model for soils rather than building structures Explain the types of measurements and specific approaches for final status surveys planned for concrete/asphalt roadways, including:
o Explanation of how the licensee will account for different densities of soil vs. concrete, and o
Dose modeling assumptions that are similar and different between the 2 materials.
Explain the types of measurements and specific approaches for final status surveys planned for the soils underneath paved areas.
Provide clarity on the locations of paved areas on the maps provided in Chapter 2.
Survey and sampling methodology for paved and shallow concrete slabs:
Clarify whether the survey and sampling methodology for Class 1 and Class 2 involve systematic sampling with a random starting point for surface soils. Clarify whether the survey and NRC staff and the licensee discussed RESRAD-ONSITE model assumptions in the development of soil DCGLs and their applicability to paved areas. NRC staff and the licensee discussed environmental factors (rainfall and runoff) and material properties (radionuclide transport in soil vs. asphalt). NRC staff noted that the LTP only has one sentence to justify the use of soil DCGLs for paved areas which indicates that the direct exposure pathway is dominant without supporting justification (i.e., analysis, calculations, etc.). NRC staff requested an analysis of these differences with a more detailed pathway analysis.
This discussion topic, in part, resulted in the issuance of CRCLT RAI-1 Approach to Dose Criterion Compliance Demonstration and CRCLT RAI-4 Applicability or Conservativism of DCGLs for Pavement-Covered Areas and Shallow Concrete Slabs.
The licensee discussed their current FSS plans for paved areas and concrete slabs, which included additional investigation if a statistical measurement lands on the asphalt (core bore into asphalt and soil).
Additionally, the discussion included the types of surveys (e.g.,
scanning, smears), location of scanning and measurements, and types of measurements (biased vs. systematic sampling) during FSS. The licensee noted that soil below the asphalt will be surveyed, as well.
NRC staff and the licensee discussed the plausibility of creating separate survey units for the pavement/slab and soil areas. If the licensee plans to separate paved areas into separate survey units, NRC staff understand that the licensee will provide maps of those survey units as part of Chapter 2 of the LTP. NRC staff noted that the current LTP does not denote which pavement-covered areas and shallow concrete slabs will remain onsite at license termination.
This discussion topic resulted in the issuance of RAI FSS-4: FSS Plans for Pavement-Covered Areas and Shallow Concrete Slabs.
CR3 LTP onsite Audit Summary of Topics December 4 - 8, 2023 Page 36 of 36 Attachment No.
Discussion Topic NRC Staff Observations & Proposed Closure Path iii iv sampling methodology for Class 3 involves random measurement patterns for surface soils.
Clarify whether alpha survey measurements will be conducted for pavement covered areas and shallow concrete slabs.
Discuss any volumetric sampling to be conducted for pavement covered areas and shallow concrete slabs.
Final status survey program quality assurance.
The NRC staff and the licensee discussed including summaries of decommissioning activities effecting quality. For example:
Written procedures Training and qualification Measurement and data acquisition Instrument selection, calibration, and operation Chain of custody Control of consumables (e.g., containers, tools)
Database control and management.
NRC staff and the licensee discussed inclusion of the measurement/data acquisition process which addresses replicate measurements and surveys, duplicate and split samples, field blanks and spikes, and quality control (QC) investigations. NRC staff learned from the licensee that the QC information is contained in the survey plans.
NRC staff understand the licensee intends to update Section 5.8, Final Status Survey Program Quality of the LTP.