ML23354A064

Enclosure - Crystal River License Termination Plan Request for Additional Information

ML23354A064
Person / Time
Site:	Crystal River
Issue date:	12/22/2023
From:	Jack Parrott Reactor Decommissioning Branch
To:	Reid B Accelerated Decommissioning Partners
Shared Package
ML23354A057	List: ML23354A063 ML23354A064
References
EPID L-2022-LLA-0194
Download: ML23354A064 (15)

Text

1 Crystal River Unit 3 Nuclear Generating Plant License Termination Plan Review Request for Additional Information Dose Modeling and Approach for Compliance with Radiological Criteria for License Termination (CRCLT)

CRCLT RAI-1: Approach to Dose Criterion Compliance Demonstration Comment:

Clarification is needed of the licensees approach to meeting the U.S. Nuclear Regulatory Commission (NRC) radiological criteria for unrestricted use (10 CFR 20.1402) for an individual who could potentially be exposed to multiple contaminated media.

Basis:

The NRC radiological criteria for unrestricted use (10 CFR 20.1402) indicates that a site will be considered acceptable for unrestricted use if the residual radioactivity that is distinguishable from background radiation results in a total effective dose equivalent (TEDE) to an average member of the critical group that does not exceed 0.25 millisievert per year (mSv/yr) (25 millirem per year) (mrem/yr) and the residual radioactivity has been reduced to levels that are as low as reasonably achievable (ALARA). To demonstrate compliance, a licensee must demonstrate that dose requirement will be met for individuals who could be exposed to multiple sources of radioactivity in a single exposure scenario.

Consolidated Decommissioning Guidance, Characterization, Survey, and Determination of Radiological Criteria, NUREG-1757, Vol. 2, Rev. 2, Section 2.7 demonstrates how to develop derived concentration guideline limit (DCGL) values to account for exposure to multiple sources of contamination using a sum-of-fractions approach. In that example, DCGL values are calculated for radioactivity in surface soil, groundwater, and buried piping such that each source contributes less than 0.25 mSv/yr (25 mrem/yr) to the projected dose. Those DCGLs provide reasonable assurance that an individual who is exposed to multiple sources of radioactivity while living onsite will not have an exposure exceeding the 0.25 mSv/yr (25 mrem/yr) 10 CFR 20.1402 dose limit.

License Termination Plan (LTP) Enclosure 10, Section 4.0 provides a formula for deriving surface soil DCGLw values based on a total dose of 0.25 mSv/yr (25 mrem/yr). Based on that formula, it is unclear how the DCGLw for surface soil will be used to demonstrate compliance with the 0.25 mSv/yr (25 mrem/yr) dose criterion for an individual (e.g., a resident farmer) who could also be exposed to contamination in subsurface soil, buried piping, and buried structures.

NUREG-1757, Appendix J, Section J.1.1 indicates that the licensee must adequately survey potentially contaminated fill materials (e.g., concrete rubble or soil) and account for their dose contributions when demonstrating compliance with the 10 CFR 20.1402 dose limit. Based on the DCGL calculation shown in LTP Enclosure 10, Section 4.0, clarification is needed of the licensee plan to account for the potential dose from backfill materials when calculating surface soil DCGL values.

2 Without a clear description of the approach for accounting for multiple sources of exposure for an individual who resides on the site after unrestricted release, the NRC staff is concerned that exposures could exceed the 10 CFR 20.1402 0.25 mSv/yr (25 mrem/yr) dose limit.

During the audit, the NRC staff learned that the licensee will be evaluating the dose contribution from different media (e.g., buried material, fill material) and from insignificant radionuclides.

Request:

a.

Please 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.

b.

Please explain the approach for incorporating the dose contribution from insignificant radionuclides.

CRCLT RAI-2 DCGL Development and Justification for Building Surfaces Left at License Termination Comment:

Clarification is needed as to the applicability or conservatism associated with applying the building occupancy scenario to basement substructures.

Basis:

The DCGLs selected for different building surfaces that are to be left in place upon license termination affects the demonstration of compliance dose to an individual who resides on the site after unrestricted release in 10 CFR 20.1402. The LTP described the end-state condition as cement structures removed to an elevation 3 ft below ground surface and backfilled to ground surface. Although the LTP provides the dose modeling approach for building surfaces, including model assumptions, inputs, and building surface DCGL values from RESRAD-BUILD, it does not give adequate technical justification for the applicability or conservativism of the building occupancy scenario as the basis for DCGLs that will be applied to subsurface basement structures. At license termination, no buildings will remain above grade at license termination, and licensee currently plans to apply these DCGLs to subsurface basement structures and buried piping. If applying building surface DCGLs developed using the building occupancy scenario, the licensee must provide either an analysis of this conservatism and/or a technical justification for the reasonably foreseeable exposure scenario selected.

During the audit, the licensee noted that they may consider revising its approach to accounting for the dose from contamination on subsurface structures. The licensee indicated it would evaluate the possibility of removing the building surface DCGLs from the LTP because no

3 buildings will remain above ground. Instead, the licensee may develop separate DCGLs for basement substructures and, possibly, buried piping.

Request:

a.

If the licensee maintains the approach of applying building surface DCGLs to subsurface structures and buried piping, please provide the following information:

RESRAD-BUILD reports for the building surface DCGLs Technical justification of the applicability or conservatism of the building occupancy scenario to subsurface basement structures.

b.

If the licensee does not apply building surface DCGLs, please provide the following information:

Dose modeling approach for the development of subsurface structure DCGLs Dose modeling approach for the development of buried piping DCGLs or new criteria to trigger the development of buried piping DCGLs Calculations and/or models used to determine the DCGLs DCGL values and technical justification for computer code applicability, selection of parameter values, and applicability of exposure scenarios and pathways.

CRCLT RAI-3 Technical Justification for Parameter Selection for Soil Dose Model Comment:

Clarification is needed of the basis for modeling soil contamination with a 15 centimeter (cm) (6 inch) thickness. Clarification is needed of the basis for sorption coefficients for radionuclides in the contaminated zone, unsaturated zone, and saturated zone in models used to calculate soil DCGL values.

Basis:

The depth of soil contamination and sorption coefficients (i.e., Kd values) affect the dose to an individual who resides on the site after unrestricted release and therefore affects compliance with the dose criterion in 10 CFR 20.1402.

NUREG-1757, Vol. 2, Rev. 2, Section 3.6 indicates that the depth of residual radioactivity in surface and subsurface soils should be informed by characterization surveys. That section of the guidance also indicates that DCGLs derived from dose modeling should be consistent with the actual vertical extent of the residual radioactivity at the site. LTP Enclosure 8, Section 2.2 and LTP Enclosure 10, Table 3 indicate that the modeled contamination depth was based on the default value for the thickness of the soil mixing layer in the RESRAD computer code.

However, the soil mixing layer thickness and the contaminated zone thickness are different parameters with different meanings in the RESRAD code. NUREG1757, Vol. 2, Rev. 2, Appendix G, Figure G.2 shows the difference between the two parameters. That figure also shows the effect of the thickness of the contaminated zone on various exposure pathways.

NUREG-1757, Vol. 2, Rev. 2, Section 3.6, states that if subsurface residual radioactivity is ignored, the dose could be significantly underestimated.

LTP Enclosure 14 includes radiological events that could lead to subsurface contamination, including radiological spills of spent resin, radioactive water release outside the Turbine

4 Building, a leaking underground pipe associated with the Station Drain Tank-1, and tritium identified in groundwater thought to be associated with the pipe leak. LTP Section 5.4.3.2 indicates that areas of potential subsurface soil contamination may be sampled at a depth up to 1 m.

Additionally, support is needed for the modeled radionuclide sorption coefficients in site soils because those values affect the calculated soil DCGL values used to demonstrate compliance with 10 CFR 20.1402. NUREG-1757 Vol. 2, Rev. 2,Section I.6.4.4 indicates that conservative percentile values can be used if the values are drawn from distributions that represent site conditions. That section of the guidance also indicates that, if dose and compliance risk are sensitive to the selection of Kd values, it may be necessary to conduct experiments using site materials to provide support for Kd values used in dose modeling. LTP Enclosure 8, Sections 2.2.1 through 2.2.3 indicate that Kd values in the contaminated zone, unsaturated zone, and saturated zone were represented in the sensitivity analyses based on parameter distributions for a generic soil type because a range of soil types are present on site. LTP Enclosure 8, Table 4 indicates that several Kd values were identified as sensitive parameters.

Because of the sensitivity of the projected dose to sorption coefficients for several radionuclides, clarification is needed of the compatibility of the distributions for the generic soil type with site soil. Without site-specific information about physical parameters that have been identified as sensitive parameters, the NRC staff cannot make a reasonable determination that DGCL values will not be overestimated, allowing doses to exceed the 10 CFR 20.1402 dose limits.

Staff learned during the audit that the licensee plans to evaluate whether to update several parameters in the RESRAD model used to generate soil DCGL values based on site-specific information.

Request:

a.

If the licensee does not update the soil DCGL model, please provide the following information:

Description of why the DCGL values are appropriate, considering possible updates to site-specific physical parameters The RESRAD-ONSITE model input and output files for the following analyses:

o DCGL calculations for each radionuclide of concern (ROC) o Sensitivity analyses for each ROC b.

If the licensee does update the soil DCGL model, please provide the following information:

Calculations and/or models used to determine the soil DCGLs Updated DCGL values Technical justification for the selection of site-specific physical parameter values.

CRCLT RAI-4 Applicability or Conservativism of DCGLs for Pavement-Covered Areas and Shallow Concrete Slabs Comment:

Clarification is needed as to the applicability of soil DCGLs to pavement-covered areas and shallow concrete slabs that will be left onsite at license termination.

5 Basis:

The DCGLs selected for pavement-covered areas and shallow concrete slabs that are to be left in place upon license termination affect the demonstration of compliance dose to an individual who resides on the site after unrestricted release in 10 CFR 20.1402. In order to demonstrate compliance, the LTP must discuss, in sufficient detail, the applicability or conservativism of DCGLs to meet the unrestricted release criteria.

LTP Section 5.4.4.1 Pavement-Covered Areas and Shallow Concrete Slabs notes that CR3 plans to apply soil DCGLs to surveys of paved areas along the roadways providing ingress to and egress from the site. The LTP indicates that the resident farmer exposure scenario associated with soil DCGLs is most applicable to pavement-covered areas and shallow concrete slabs because it includes direct radiation from surface soil. However, the licensee did not address whether other pathways could be applicable or whether the parameters used to model direct radiation from soil are applicable to pavement (e.g., density).

Staff learned during the audit that the licensee plans to evaluate the applicability or conservatism of soil DCGLs to paved areas and concrete slabs remaining onsite, including contributions from multiple exposure pathways.

Request:

To support the approach of applying soil DCGLs to pavement-covered areas and shallow concrete slabs, please provide technical justification (analysis, explanation, etc.) that the resident farmer exposure scenario is applicable or conservative with respect to pavement-covered areas and shallow concrete slabs. Discuss dominant pathways and other pathway contributions from applying the conceptual model for soils and the applicability of the physical parameters used in the model.

Hydrology and Groundwater (HGW)

HGW-1 Comment:

Clarification is needed for the appropriateness of hydrogeological inputs for all areas of the site in groundwater pathways of DCGLs for soils or subsurface structures.

Basis:

The basis for hydrogeological input values for RESRAD-ONSITE calculations and their appropriateness to the conceptual site model is needed to provide reasonable assurance that the site has been adequately characterized per 10 CFR 20.1501.

Revision 0 of LTP Section 2.4.8 provides a description of the geological media in berm (power block) and non-berm areas. Staff notes that the conceptual models for berm and non-berm areas are significantly different, yet the same hydrogeological inputs were applied to both areas.

Table G-1 of Enclosure 16 (Crystal River Unit 3 DCGL Development Summary Report, Revision

0) provided the hydrogeological input values for the soil DCGL. Enclosure 22 (Haley & Aldrich 2023, which includes GHS 2017 as Appendix A) provided hydrogeological information and

6 support for selected hydrogeological inputs. However, the unsaturated zone thickness, unsaturated zone hydraulic conductivity, hydraulic gradient, sorption coefficients, vertical flux may not be consistent with the description of the hydrogeology in different areas of the site.

Also, the hydrogeological inputs were also a mixture of site-specific information and in RESRAD-ONSITE default parameters that may lead unrealistic flow and transport. In addition, significant wellbore dilution estimated for soil DCGLs using RESRAD-ONSITE warrants a more substantial supporting basis than was provided for inputs in Table G-1 of Enclosure 16.

Request:

The licensee indicated during the audit that they will first assess the possibility of eliminating the groundwater pathway by demonstrating that the saturated groundwater at the site is not usable and thus would not meet the definition of an aquifer by the state of Florida. That demonstration should include data supporting the poor groundwater quality.

If the saturated groundwater system below the site meets the definition of an aquifer in the state of Florida, then the licensee should provide justification and bases for hydrogeological inputs to RESRAD-ONSITE using site-specific information or show that the inputs lead to conservative dose results. If inputs cannot be justified or shown to lead to conservative doses, then soil DCGLs (and potential subsurface structure DCGLs) will need to be revised.

HGW-2 Comment:

Clarification is needed on how the entire suite of radionuclides for existing groundwater contamination will be shown to be below detection for the final status survey (FSS) consistent with laboratory reporting guidance in NUREG-1576 (MARLAP).

Basis:

A discussion of groundwater data quality objectives (DQOs) is needed to help staff understand the sufficiency of plans to provide reasonable assurance that the final conditions of the site are consistent with the dose criteria in 10 CFR 20.1402 and that the site has been adequately characterized per 10 CFR 20.1501.

In Revision 0 of LTP Section 5.4.4.7, the licensee provided a partial description of information needed for DQOs addressing existing groundwater contamination for dose calculations. In addition to historical data, staff notes that DQOs should address the possibility of dismantling and demolition activities during decommissioning leading to radionuclides being released to the subsurface. Also, the LTP did not provide an approach for estimating dose due existing groundwater contamination, nor how that dose will be addressed the total dose calculation for a survey unit in the FSS.

According to Revision 0 of LTP Section 2.4.11, data from the sampling program did not indicate to the licensee that the groundwater was significantly impacted by plant-related radionuclides.

Revision 0 of LTP Table 2.25 provided groundwater concentrations for the period 2020-2022 for only 3 of the 19 site-specific ROCs in Revision 0 of LTP Table 5.1 (H-3, Co-60, and Cs-137). In addition, historical groundwater results in Revision 0 of LTP Table 2-25 were reported as U:

Not detected, value is the laboratory reporting limit. In the annual radiological environmental

7 operating reports (AREORs), the results were reported as below the lower limit of detection (LLD), though no definition for LLD was provided. Staff notes the laboratory reporting, such as the detection decision, should either follow NUREG-1576 (MARLAP) guidance or demonstrate how the reporting of results are consistent with the intent of MARLAP guidance.

During the audit, the licensee indicated they may choose to demonstrate that the entire suite of radionuclides will be shown to be below detection limits for existing groundwater contamination for FSS. Therefore, no approach for existing groundwater contamination would be required in the LTP; only a basis for the detection decision would be needed that considers MARLAP guidance. However, licensee may consider the development of groundwater pathway dose conversion factors (PDCFs) in the LTP to alleviate the risk associated with not being able to demonstrate all radionuclides are below detection at the time of FSS, or if the saturated groundwater system below the site is not excluded by the state of Florida due to saltwater intrusion. If groundwater PDCFs are developed, the licensee also would need to develop an approach to factor in the groundwater dose for existing groundwater contamination into the total dose calculation to meet the 25 mrem/yr release criteria.

Request:

Provide an approach for demonstrating that the entire suite of radionuclides will be below detection limits for existing groundwater contamination for the FSS. To address elimination of groundwater pathways in DCGLs for soil and (potential) subsurface structures, provide justification that the saturated groundwater beneath the site has significant saltwater intrusion and therefore would not be considered an aquifer due to saltwater intrusion using the state of Floridas definition.

Site Characterization (SC)

SC-1 Site Characterization Comment:

Supplement the LTP characterization data to provide:

Methods for survey measurements to clarify what the data being reported represent, Justification for the classification for structural survey units (subsurface basements, underground piping) consistent with NUREG-1575, Multi-Agency Radiation Site Survey and Investigation Manual (MARSSIM) classifications, the development of radionuclide mixtures (including surrogate ratios for HTDs) for each applicable area, the determination of insignificant contributors.

Justification for the classification of outdoor survey units (surface and subsurface) with few to no measurements.

Basis:

The LTP must provide an adequate site characterization (10 CFR 50.82(a)(9)(ii)(A)) with surveys of area, including the subsurface, sufficient to evaluate the concentration or quantity of residual radioactivity and the potential radiological hazards of radiation levels and residual

8 radioactivity detected (10 CFR 20.1501(a)(2)). Characterization is necessary to distinguish between areas with and without residual radioactivity, to quantify the extent of existing contamination, and radionuclide fractions. The licensee committed to performing site characterization activities in accordance with MARSSIM, NUREG-1757, and site procedures.

NUREG-1575, Multi-Agency Radiation Site Survey and Investigation Manual (MARSSIM),

Section 4.4, Classify Areas by Contamination Potential and A.2, Classification of Areas by Residual Radioactivity Levels, detail survey unit classification consideration for non-impacted and impacted areas, including criteria for Class 1, Class 2, and Class 3. The initial assumption for classification is that all areas are considered Class 1 unless there is some basis for reclassification as Class 2 or Class 3.

NUREG-1757, Section 4.2.2, Characterization Surveys describes characterization surveys, which include systematic as well as judgmental measurements. The LTP Section 2.3.1, Data Quality Objectives maintains that characterization surveys of sufficient quality and quantity were performed to determine the nature and extent of residual radioactivity in applicable structures, site soils, groundwater, and surfaces. The LTP continues indicating that soils and structures were sampled, and sufficient measurements were obtained to determine mean and maximum activity and sample standard deviation. Enclosure 19, CR3 Site Characterization Survey Report (CHAR-01) Impacted Open Land Survey Areas, Section 1.2.2, Sample Plan, states that from seven to ten samples were collected from the outdoor survey areas ranging in size from 2,712 m2 to 283,000 m2.

NUREG-1757, Section 4.2.2, recommends the licensee describe the characterization design and results of the survey, including for sites, areas, or buildings with multiple radionuclides, a discussion justifying the ratios of radionuclides that will be assumed in the FSS or an indication that no fixed ratio exists, and each radionuclide will be measured separately. MARSSIM, Section 5.3, Characterization Surveys recommends the results of the characterization should include the identification and distribution of contamination in buildings, structures, and other site facilities.

To conduct a MARSSIM, Section 5.3, Characterization Surveys recommends the results of the characterization should include the concentration and distribution of contamination in surface and subsurface soils. The LTP Section 2.3.4, Types of Measurements and Samples summarized the approach to static measurements, beta surface scans, gamma surface scans, removeable surface scans, concrete sampling, and material sampling. The sampling depth for soil and concrete core sampling was six inches. The LTP identified no subsurface samples in the site characterization summary. For areas of potential subsurface soil contamination, the LTP Section 5.4.3.2, Volumetric Samples states that areas of potential subsurface soil contamination may be sampled at a depth up to 1 meter. The LTP stipulates where subsurface sampling is used for FSS compliance purposes, additional subsurface soil sampling/assessment details will be provided to the NRC on a case-by-case basis to ensure that sampling and evaluation methods are appropriate. No elaboration on example scenarios under which this subsurface process would be implemented, or the criteria to trigger subsurface investigations is specified.

In the LTP summary to Chapter 2 (Section 2.6, Summary) the licensee asserts that characterization data collected and analyzed to date are of sufficient quantity and quality to provide a basis for the initial classification of survey areas, yet the LTP lacks characterization for

9 structures (subsurface basements, underground piping) and some outdoor survey units. During the ongoing audit, NRC staff was informed areas would not be reclassified; however, the licensee considered classification of an area under a building to be initial classification.

Incorporate in this section of the LTP a discussion on the process for using characterization or other survey data to verify survey unit classifications, especially when justifying a Class 2 or Class 3 designation.

Request:

a.

Update the relevant sections of the LTP to provide adequate characterization information for structures, embedded piping, surface and subsurface land areas, above ground concrete and asphalt. Note that the NRC staff identified survey units with few or no sampling locations (e.g., WOCZ-03, WOCZ-04, EOCZ-03, EOCZ-04, EOCZ-07, EORB-01, SOCZ-04, SORB-01, SORB-02, SORB-03, SORB-04, SORB-05, SORB-08, SORB-09), which brings into question the completeness of the site characterization. Data tables should address all ROCs, including the HTDs, to an appropriate extent. The LTP should provide a detailed description (or figure) when gamma scans were conducted during the characterization and, in their absence, the process for identifying residual radioactivity at levels of concern.

b.

Summarize the characterization survey methods used to collect the sampling and measurement data, including:

Discussion of ROCs (including HTDs) during characterization and how the instruments and measurements are appropriate for all ROCs.

c.

The licensees development of radionuclide mixtures is dependent on the site characterization effort. Discuss the methodology for determining radionuclide fractions/mixtures and the results to inform the analysis of insignificant contributors, surrogate ratios, weighted instrument efficiencies, and gross activity DCGLs.

d.

Table 2.6, Additional Phases of Characterization to be Complete of the LTP provided a schedule and objectives for the remaining site characterization phases. Explain in related text how the additional site characterization will be considered in the remediation/FSS plans.

e.

Discuss the process for delineating survey units and validating MARSSIM classification with scoping and characterization data. Provide supplemental information or provide, in the absence of characterization data (buried piping, subsurface basements), a basis for classifications.

f.

For subsurface sampling, describe:

The criteria for determining when subsurface sampling and measurements are completed (e.g., reaching a depth where measurements return to background levels).

The criteria the licensee used to determine that residual radioactivity does not exceed 1 meter in depth.

The subsurface sampling results completed to date.

10 Final Radiological Survey Plan (FSS)

FSS-1: Insignificant Contributors Comment:

The LTP does not include an approach to determining insignificant contributors (ICs) based on site characterization data, the process to account for potential dose from ICs, and a method for continued validation that radionuclides remain insignificant radionuclide through the FSS process.

Basis:

To validate the adequacy of methods to demonstrate, with reasonable assurance, compliance with unrestricted release criteria (10 CFR 20.1402), the site must have provisions for determining the contributions of ICs to the dose criteria. Detailed information on the FSS plan for survey and sampling is necessary to ensure the survey (10 CFR 20.1501 (a)(2)) and LTP (10 CFR 50.82(a)(9)(ii)(D)) requirements are met. Surveys must account for all radionuclides of concern identified in the LTP. NUREG-1757, Section 3.3, Insignificant Radionuclides and Exposure Pathways allows for the elimination of radionuclides considered insignificant contributors to dose for further detailed consideration; however, their dose contributions must be considered in demonstrating compliance with the radiological release criteria for license termination. The sum of dose contributions from all insignificant contributor radionuclides should be no more than 10 percent of the dose criterion in 10 CFR 20, Subpart E. Characterization data or analysis (if remediation is planned) may be used to define the relative activities of significant and insignificant radionuclides to determine relative dose contributions from radionuclides. The licensee should show that the relative dose contributions will not increase following remediation because of an increase in concentrations or redistribution of residual radioactivity.

The LTP Enclosure 5, Crystal River Nuclear Power Station Radiological Nuclide Selection for DCGL Development describes the selection of radionuclides of concern, which are summarized in Table 6-1, CR3 Site-Specific Suite of Radionuclides. A theoretical list of radionuclides was derived from NUREG/CR-3474, Long-lived Activation Products in Reactor Materials. Additional radionuclides were added to the list based on previous analyses and documentation from NUREG/CR-4289, Residual Radionuclide Contamination Within and Around Commercial Nuclear Power Plants and the Crystal River historical site assessment. ROCs were eliminated if the half-life was less than 5.4 years, except for Co-60, or if the individual radionuclide contributed less than 0.1 percent of the total activity from the NUREG/CR-3474 evaluation. To determine the dose contributions for all radionuclides, doses for both the residential and occupancy scenarios were generated with the Decontamination and Decommissioning (DandD) code. The dose contribution from these deselected ROCs were calculated to be less 0.0449 percent and 0.0016 percent of the total calculated dose for the residential scenario and the occupancy scenario, respectively. Several radionuclides met the criteria for deselection but could not be discounted because there are other methods of production in addition to activation of reactor components or they were observed in the waste stream analysis or site characterization samples. While the LTP mentions information from site characterization was considered in the analysis, the LTP did not include a discussion of the sample results, their support of the theoretical selection and deselection of radionuclides, or the verification of the

11 radionuclide fractions discussed in Enclosure 5. In addition, the LTP lacks a discussion of the process for continuing validation of insignificant contributors.

Request:

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 radionuclide fractions/mixtures are determined, how these fractions will be utilized, and how these fractions will be verified throughout the characterization, remediation, and FSS process.

Describe the process to account for all radionuclides of concern in Table 2.4 during the FSS, including plans to conduct further deselection of radionuclides, if being pursued.

FSS-2: Surrogate Radionuclides Comment:

The LTP states there is no plan to use surrogate radionuclides with no discussion of an alternative approach to account for hard to detects (HTDs) during surveys.

Basis:

To validate the adequacy of methods to demonstrate, with reasonable assurance, compliance with unrestricted release criteria (10 CFR 20.1402), the site must have provisions for determining contributions from all radionuclides of concern, including HTDs, in the final dose calculations. Detailed information on the FSS plan for survey and sampling is necessary to ensure the survey (10 CFR 20.1501 (a)) and LTP (10 CFR 50.82(a)(9)(ii)(D)) requirements are met. NUREG-1757, Section 4.1.4, Release Criteria states that the licensee should list the DCGLs that will be used to design the surveys and to demonstrate compliance with the radiological criteria for release, including the DCGLW for each radionuclide and medium, the DCGLEMC (or area factors) for each radionuclide and medium, and the appropriate DCGLW for the survey method if multiple radionuclides are present. MARSSIM, Section 4.3.2, DCGLs and the Use of Surrogate Measurements recommends for sites with HTD radionuclides, surrogate measurements may be utilized if a ratio can be established between the ROCs. When a surrogate is used, the DCGL for the radionuclide that is measured is adjusted downward allowing the licensee to demonstrate compliance with all contaminants.

Section 5.2.1.3, Surrogate Ratio DCGLs of the LTP states that CR3 does not currently plan on using surrogate DCGLs due to the difficulty in determining consistent ratios, but that if surrogates are to be used a white paper will be generated and submitted to the NRC for approval. This is reiterated in Section 5.3.3.1, Determining Which Statistical Test Will Be Used.

During the ongoing audit, the licensee informed NRC staff of the plan to reevaluate the use of surrogate ratios for HTD radionuclides.

Request:

12 If surrogate ratios are not used, please provide a description of the process to account for HTD radionuclides during direct and scanning surveys is needed. In addition, all samples require analysis for the full suite of radionuclides in Table 2.4.

If surrogates are used, discuss:

How surrogate ratios are developed The application during direct and scanning surveys How minimum detectable concentrations (MDCs) and DCGLs are determined Plans for the verification of surrogate ratios through the FSS process.

If the licensee decides not to use surrogates, a description of the process to account for HTD radionuclides during direct and scanning surveys is needed. In addition, all samples require analysis for the suite of radionuclides.

FSS-3: Instrument and Laboratory Analysis Minimum Detectable Concentrations Comment:

The LTP does not include static and scan minimum detectable concentrations that are directly comparable to the surface and soil DCGLs. Clarification is needed on the input parameters for MDC calculation to validate that the MDCs are comparable to the surface and soil DCGLs.

Gamma measurement sensitivities provided in Table 5.8, Typical FSS Instrumentation and Sensitivities include only Co-60 and Cs-137, while other gamma emitting radionuclides are included in the radionuclides of concern. The LTP does not include specific information on offsite analyses.

Basis:

Surveys shall be conducted to evaluate concentrations or quantities of residual radioactivity and the potential radiological hazards of radiation levels and residual radioactivity detected (10 CFR 20.1501(a)(2)). Instruments and equipment used for quantitative radiation measurements require periodic calibration for the radiation measured (10 CFR 20.1501(c)). MARSSIM, Section 6.5.4, Instrument Calibration indicates proper calibration procedures are essential to providing confidence in the measurements made to demonstrate compliance with clean up criteria.

Factors affecting the calibration validity include (1) the energies of radioactive sources used for routine calibration differing from radionuclides in the field, (2) differences in source-to-detector distances between calibration and actual conditions, and (3) the condition and composition of surfaces monitored. If responses under routine calibration and use conditions are significantly different, correction factor(s) should be supplied. MARSSIM, Section 6.5.3, Instrument Selection recommends instrumentation be capable of detecting the type of radiation and the sensitivity capable of measuring less than the DCGL.

The LTP Table 5.8 provides a subset of input parameters to the MDC calculations including detector area, instrument efficiencies for alpha and beta instruments, and less than background levels. Field gamma instrument sensitivities are given in µR/h without information on background or efficiency. The LTP does not provide any preliminary static or scan MDCs in units directly comparable to the surface and soil DCGLs.

13 LTP, Section 5.4.5, Instrumentation, discusses instrument selection, calibration and maintenance, response checks, and MDC, including equations and information used to calculate static and scan MDCs. The example calculation provided in Enclosure 6, Section 6.0, Applying Efficiency Corrections Based on the Effects of Field Conditions for Total Efficiency, indicates the total efficiency (et) is derived from the product of the instrument efficiency (ei), the source efficiency (es), and the source-to-detector correction. The LTP does not specifically address the basis for the assumption of a 50% Cs-137 and 50% Co-60 radionuclide mixtures used to determine the weighted ei and es. As the Co-60 to Cs-137 ratio increases, the weighted es is no longer appropriate and overestimates the actual efficiency. The resulting scan MDC and surface activity would be underestimated. Table 5.9, Source-to-Detector Distance Effects on Instrument Efficiency for / Emitters of the LTP includes source-to-detector variable that are used in conjunction with the instrument and source efficiencies to calculate a total efficiency., Table 3.1, Nominal Instrument Efficiencies (es) lists Tc-99 and Am-241, with an active area of 15.2 cm2, as the calibration sources for beta and alpha, respectively. All alpha and beta detectors listed in Table 5.8 of the LTP have physical probe areas of 100 cm2 or larger.

The instrument alpha and beta efficiency terms are overestimated because the calibration sources are smaller than the physical area of the detectors. The LTP does not explain how efficiencies for large area sources (i.e., source larger than the probe area) are determined.

The licensees beta-gamma and land area gamma surface scan MDC equations both selected an index of sensitivity (d) of 1.38, which is documented in Section 5.4.5.4.2, Structural Surface Beta-Gamma Scan MDCs and Section 5.4.5.4.6, Open Land Area Gamma Scan MDCs.

Guidance provided from the confirmatory survey contractor suggests a d value of 2.32, which corresponds to a false positive value of 0.25 and the acceptable probability of a detection at 95%. The LTP does not provide justification for the selection of the index of sensitivity.

NUREG-1757, Section 4.4, Final Status Survey Design recommends a description of analytical instruments for sample measurement, including the calibration, sensitivity, and methodology for evaluation, be supplied to validate that the analysis has adequate sensitivity to demonstrate compliance with release criteria. The information provided in the LTP for planned sample analysis methods is limited. Section 5.4.5.4.7, HPGe Spectrometer Analysis mentions the use of onsite High Purity Germanium Detector (HPGe) calibrated for various sample geometries. Laboratory counting times are set to meet an approximate MDC of 50 percent of the DCGLs. Table 5.8 includes a Mirion HPGe detector for gamma counting and a Ludlum L-2000 for alpha and beta counting. The reported sensitivity of 0.1 pCi/g for Co-60 and Cs-137 for the HPGe satisfies the recommendation for an MDC of between 10 to 50% of the DCGL for Co-60 and Cs-137; however, MDCs for other gamma emitters are not provided. Sensitivities comparable to the surface DCGLs are not included in the LTP for the Ludlum L-2000. For the onsite laboratory, the LTP does not contain sufficient information to determine if the sensitivity for gross alpha and gross beta is less than the DCGL. The LTP does not provide information on vendor laboratory analysis sensitivities.

Request:

Instrument sensitivity and laboratory sample analysis should be capable of measuring residual radioactivity less than the DCGL. To facilitate validation of instrument and method sensitivities:

14 Provide the values used to calculate static MDCs, including background count, sample and background count times, instrument and source efficiencies, and probe areas for detectors.

Provide the variables used to calculate scan MDCs, including the d, the time interval the probe is over the hot spot, the surveyor efficiency, instrument and source efficiencies, and the probe area. Evaluate the applicability of d value to the site-specific situation, justify the selection, and adjust the scan MDC as necessary.

Describe the derivation of the weighted instrument and source efficiencies, including the radionuclide mixture/fractions used.

For field survey and onsite laboratory instruments in Table 2.5, Instrument Types, Nominal Sensitivity, and MDC Examples and Table 5.8, include a priori static and scan MDCs directly comparable to the DCGLs for measurement types (alpha, beta, gamma, specific radionuclides).

Summarize offsite laboratory sensitivities, including a description of the analysis type, technique, method, and MDCs.

FSS RAI-4: FSS Plans for Pavement-Covered Areas and Shallow Concrete Slabs Comment:

Clarification is needed as to the FSS plans for pavement-covered areas and shallow concrete slabs that will be left onsite at license termination.

Basis:

10 CFR 20.1501(a)(2) indicates that the licensee shall make surveys of areas that may be necessary for the licensee to comply with the regulations in Subpart F. NUREG-1757 Vol. 2, Rev. 2, Appendix G, Section G.3.4, Paved Parking Lots, Roads, and Other Paved Areas provides guidance on FSS design for paved areas. Additional information is needed about the FSS plan for pavement-covered areas and shallow concrete slabs.

Generic survey design criteria including DQOs, scan coverage, sample size distributions, reference grids and sample locations, investigation levels, and elevated measurement comparisons are found in Section 5.3, Survey Design and Data Quality Objectives. Section 5.4.4.1, Pavement-Covered Areas and Shallow Concrete Slabs states the survey design was based on soil survey unit (SU) sizes with paved areas designated as separate SUs or incorporated into adjacent land areas. Surveys will include scan and static measurements and sampling of the asphalt/concrete and the soil underneath. Further clarification or discussion is needed on the approach used to measure residual radioactivity in paved/concrete areas and roadways. The LTP does not specify whether samples are random or random-start systematic samples are planned, or when gamma verses beta-gamma scan and static measurements will be conducted. The criteria for volumetric sampling for the asphalt/concrete and the soil underneath is unclear. The LTP states surveys of roadways providing ingress and egress to CR3 will be required; however, no details are provided. LTP Section 5.3.6.2, Investigation Levels discusses judgmental sampling for soils, especially at locations of direct radiation identification during scanning. However, Section 5.4.3, Soils does not discuss this approach for pavement-covered areas and shallow concrete slabs.

15 Based on audit conversations, the licensee may develop separate FSS plans (including separate survey units) for pavement-covered areas and shallow concrete slabs from the surface soil underneath.

Request:

Please provide an explanation of the types of measurements and specific approaches (scanning, static surveying, sampling, volumetric analysis, etc.) for final status surveys planned for:

Pavement-covered areas and shallow concrete slabs.

Soil underneath pavement-covered areas and shallow concrete slabs.

The investigation levels for pavement-covered areas and shallow concrete slabs.

If the licensee creates separate survey units for pavement-covered areas and shallow concrete slabs, please provide a map of those survey units, including information on survey unit size and MARSSIM classification of each unit.