ML25063A286
| ML25063A286 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 03/10/2025 |
| From: | Reactor Decommissioning Branch |
| To: | |
| Shared Package | |
| ML25063A282 | List: |
| References | |
| EPID L-2024-DFR-0002 | |
| Download: ML25063A286 (1) | |
Text
U.S. NUCLEAR REGULATORY COMMISSION THE OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS TECHNICAL EVALUATION OF THE PHASE 1 FINAL STATUS SURVEY REPORTS FORT CALHOUN STATION, UNIT 1 OMAHA PUBLIC POWER DISTRICT FACILITY OPERATING LICENSE NO. DPR-40 DOCKET NO. 50-285
1 List of Acronyms and Abbreviations
Delta
/
Relative Shift
Sigma ADAMS Agencywide Documents Access and Management System BcDCGL Base Case Derived Concentration Guideline Level BcSOF Base Case Sum of Fractions C-14 Carbon-14 Co-60 Cobalt-60 Cs-137 Cesium-137 DQO Data Quality Objective EPA Environmental Protection Agency ER Evaluation Report ERC Exposure-rate-to-concentration Eu-152 Europium-152 FCS Fort Calhoun Station, Unit 1 FSS Final Status Survey FSSFR Final Status Survey Final Report FSSR Final Status Survey Report HTD ICs Hard-to-Detect Insignificant Contributors ISFSI Independent Spend Fuel Storage Installation ISOCS In Situ Object Counting System LAR License Amendment Request LBGR Lower Bound of the Gray Region LTP License Termination Plan MARLAP Multi-Agency Radiological Laboratory Analytical Protocols Manual MARSSIM Multi-Agency Radiation Survey and Site Investigation Manual (NUREG-1575)
MDC Minimum Detectable Concentration mrem/yr Millirem Per Year MOU mSv Memorandum of Understanding Millisievert NaI Sodium Iodide NRC U.S. Nuclear Regulatory Commission OLA Open Land Area OpDCGL Operational Derived Concentration Guideline Level OPPD Omaha Public Power District ORAU Oak Ridge Associated Universities ORISE Oak Ridge Institute for Science and Education pCi/g Picocuries Per Gram QAPP Quality Assurance Program Plan QC Quality Control RA Radiological Assessment RAI Request for Additional Information
2 ROC Radionuclide of Concern SRP Standard Review Plan SOF SURR Sum of Fractions Survey Unit Release Record TEDE Total Effective Dose Equivalent UBGR Upper Bound of the Gray Region UCL Upper Confidence Limit VSP Visual Sample Plan
3
1.0 INTRODUCTION
Fort Calhoun Station, Unit 1 (FCS) is a permanently shutdown nuclear power reactor in active decommissioning. The goal the FCS decommissioning is to complete all activities necessary to terminate the license and release the FCS site for unrestricted use, except for the footprint of the Independent Spent Fuel Storage Installation (ISFSI) containing the spent nuclear fuel. The decommissioning activities and timeline are described in the FCS Post Shutdown Decommissioning Activities Report (PSDAR) dated December 16, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19351E355). In accordance with 10 Code of Federal Regulations (CFR) 50.82(a)(11), the U.S. Nuclear Regulatory Commission (NRC) shall terminate a power reactor license if it determines that: (i) the remaining dismantlement has been performed in accordance with the approved license termination plan, and (ii) the final radiation survey and associated documentation, including an assessment of dose contributions associated with parts released for use before approval of the license termination plan, demonstrate that the facility and site have met the criteria for license termination in 10 CFR Part 20, Subpart E.
Revision 0 of the FCS License Termination Plan (LTP) was submitted to the NRC under the requirements of 10 CFR 50.82(a)(9) on August 3, 2021 (ML21271A178). After review of Revision 0 by NRC, but before approval, Revision 1 (LTP, Rev. 1) of the FCS LTP was submitted on December 6, 2023 (ML23346A152). Under the provisions of 10 CFR 50.82(a)(1),
LTP, Rev.1 was approved by the NRC on January 31, 2024, as documented in the NRC staffs Safety Evaluation Report (ML24019A168). LTP, Rev.1 supplied the details of the plan for characterizing, identifying, and remediating the remaining residual radioactivity at the FCS site to a level that will allow the site to be released for unrestricted use. LTP, Rev. 1 also described how the licensee will confirm the extent and success of remediation through radiological surveys, as described in final status survey reports (FSSRs).
2.0 BACKGROUND
In a meeting held with representatives of the Omaha Public Power District (OPPD or licensee) on March 27, 2025 (ML24107B127), the licensee described its plan to submit the FSSRs to support license termination of FCS in four phases that will cover all the areas of the site proposed to be released from the license. Phase 1 of the FCS FSSRs was submitted to the NRC by letter dated April 17, 2024 (ML24114A232) and supplemented with additional information on August 10, 2024 (ML24235A082). Revision 1 of the Phase 1 FSSRs was submitted on November 21, 2024 (ML24326A263). The Phase 1 FSSRs cover eleven Class 3 Open Land Area (OLA) survey units. The licensees Final Status Survey (FSS) design criteria, implementation of the Data Quality Objectives (DQO) process, and survey approach/methods included in the Phase 1 FSSRs, were reviewed, and the results were assessed against the approved release criteria from LTP, Rev 1.
2.1 Areas Evaluated The areas the licensee proposed to be released under the Phase 1 of the FSSRs consist of twelve Class 3 OLA survey units. In November 2024, the licensee submitted a revision to the
4 Phase 1 FSSR which included only eleven Class 3 OLA survey units due to the removal of survey unit 8307 from consideration. A final status survey was performed for each of these survey units in accordance with the LTP, Rev.1, NUREG-1575, Rev. 1, Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM), dated August 2002 (ML003761445), and FCS implementing procedures. The implementation of FCS FSS plans, described in the LTP, Rev. 1, support meeting the radiological criteria for unrestricted use in 10 CFR 20.1402, and the survey requirements of 10 CFR 20.1501 (a) and (b) and 10 CFR 50.82(a)(9)(ii)(D)). The licensee states that the FSSR incorporates multiple survey unit release records (SURRs), which provide complete and unambiguous records of the as-left radiological status of specific survey units. NRC staff submitted correspondence, dated July 8, 2024 (ML24180A203), requesting additional information on the Phase 1 FSSR and associated SURRs. The licensee provided a response dated August 10, 2024 (ML24235A082). Sufficient data and information were included in the FSSR and attached SURRs, and the request for additional information (RAI) responses, to enable an independent re-creation and evaluation of both the derived results and the survey activities. According to the licensee, the FSSR was written consistent with the guidance provided in NUREG-1757, Volume 2, Revision 2, Consolidated Decommissioning Guidance -
Characterization, Survey, and Determination of Radiological Criteria (ML22194A859);
MARSSIM; and the licensees procedures on final status survey data reporting.
Figure 1. FCS Phase 1 FSSR Survey Unit Locations
5 2.2 Applicable Requirements 10 CFR 20.1402, Radiological criteria for unrestricted use, states in part: A site will be considered acceptable for unrestricted use if the residual radioactivity that is distinguishable from background radiation results in a TEDE [Total Effective Dose Equivalent] to an average member of the critical group that does not exceed 25 mrem (0.25 mSv) per year, including that from groundwater sources of drinking water, and the residual radioactivity has been reduced to levels that are as low as reasonably achievable (ALARA). 10 CFR 20, Subpart F, Surveys and Monitoring further states that each licensee shall make or cause to be made, surveys of areas, including the subsurface, that (1) May be necessary for the licensee to comply with the regulations in this part; and (2) Are reasonable under the circumstances to evaluate: (i) The magnitude and extent of radiation levels; and (ii) Concentrations or quantities of residual radioactivity; and (iii) The potential radiological hazards of the radiation levels and residual radioactivity detected. FCS documented its proposed approach for meeting these requirements and for documenting the results of its surveys in LTP, Rev.1.
Section 5.7, Final Status Survey Reporting, of LTP, Rev. 1, described FCS approach to license termination and FSSR documentation. Specifically, FCS specified that documentation of the FSSs would be contained in two types of records consistent with Section 8.6, Documentation, of the Multi-Agency Radiation Survey and Site Investigation Manual, NUREG-1575, Rev. 1 (MARSSIM) (ML00376476). In accordance with the LTP, Rev. 1, FCS provided to the NRC, a Final Status Survey Final Report (FSSFR), that included a summary of the survey results and the overall conclusions which demonstrated that the Phase 1 portions of the site, met the radiological criteria for unrestricted use, including ALARA. As appendices to the FSSFR, FCS prepared a Survey Unit Release Record (SURR) to provide a complete record of the as-left radiological status for individual survey units, relative to the specified release criteria.
Chapter 6 of LTP, Rev. 1, provided site-specific derived concentration guideline level (DCGLs) values that correspond to a site wide dose of 25 mrem/yr for each radionuclide of concern (ROC) and each potentially contaminated media remaining at the time of license termination.
FCS stated in LTP, Rev. 1, that dose from multiple radionuclides would be accounted for using the sum of fractions (SOF) approach. The Phase I FSSR contains only one media type, surface soil. FCS anticipated that FSSRs would be provided in phases as remediation and FSS are completed in related portions of the site. The phased approach provides the NRC with detailed insight on remediation and FSS early in the process, while offering FCS opportunities for improvement based on feedback from NRC.
The final dose used to demonstrate compliance with the 25 mrem/yr criterion will be the summation of the dose from all FCS site media. Dose from soil pathways is one part of this compliance dose calculation. The final compliance dose summation evaluation will occur once all FSSR phases have been submitted.
2.3 NRC Review Approach The NRC staff evaluated the FCS Phase 1 FSSR against the information contained in FCS LTP, Rev. 1, to ensure that FCS decommissioning and FSS activities were consistent with, or comparable to, the NRCs applicable decommissioning guidance. The guidance that NRC used
6 for this evaluation includes: MARSSIM; NUREG-1507, Minimum Detectable Concentrations with Typical Radiation Survey Instruments for Various Contaminants and Field Conditions, Revision 1 (ML003676046); NUREG 1505, A Nonparametric Statistical Methodology for the Design and Analysis of Final Status Decommissioning Surveys, Revision 1 (ML061870462);
NUREG-1700, Standard Review Plan for Evaluating Nuclear Power Reactor License Termination Plans, Revision 2, (ML18116A124); and NUREG-1757, Volume 2, Consolidated Decommissioning Guidance, (ML22194A859) to ensure that FCS met the radiological criteria for unrestricted use as specified in 10 CFR 20.1402, Radiological criteria for unrestricted use.
The NRC staff provided evaluations regarding the FSS strategies and results for open land survey areas included in the Phase 1 FSSR.
3.0 TECHNICAL EVALUATION
3.1 Class 3 Open Land Areas As previously mentioned in Section 2.0, on November 12, 2018, and June 29, 2018, OPPD submitted requests to release a portion of the FCS site in accordance with 10 CFR 50.83, Release of Part of a Power Reactor Facility or Site for Unrestricted Release, and 10 CFR 100, Reactor Site Criteria. The partial site release consisted of five non-impacted open land areas.
The release of these areas from the license was approved by the NRC on April 10, 2019. In addition to this PSR, OPPD anticipated three subsequent FSSR submittals, of which this is the first. The Phase 1 FSSR was submitted on April 17, 2024 (ML24114A232) and included twelve open land area survey units. The NRC staff responded with a request for additional information on July 8, 2024 (ML24235A082). The Phase 1 FSSR was revised to address NRC RAIs and resubmitted on November 21, 2024 (ML24326A263). The FCS Phase 1 FSSR, Rev. 1 consists of eleven Class 3 OLA survey units as summarized in Table 1 below. Survey Unit 8307 was originally included in the Phase 1 FSSR, Revision 0, but was subsequently removed in the Phase 1 FSSR, Revision 1, as the survey unit required a reperformance of the final status survey due to flooding in the survey unit.
3.1.1 Summary of Phase 1 Survey Units to be Released Tables 1 through 4 summarize the survey unit classifications and sizes, criteria for survey unit final status survey, scan minimum detectable concentration (MDC), and survey unit results.
Detailed discussion, NRC evaluations, and regulatory findings are included in Section 3.2, NRC Evaluation of Phase 1, Class 3, Open Land Survey Areas.
7 Table 1. FCS Phase 1 FSSR Survey Units Survey Unit Type Survey Unit Description Class Size (m2) 8101 Open Land North Owner Controlled Area 3
99,210 8102 Open Land North Owner Controlled Area 3
74,685 8103 Open Land North Owner Controlled Area 3
58,497 8104 Open Land North Owner Controlled Area 3
99,971 8105 Open Land North Owner Controlled Area 3
99,994 8106 Open Land North Owner Controlled Area 3
99,788 8109 Open Land North Owner Controlled Area 3
98,266 8110 Open Land North Owner Controlled Area 3
105,611 8202 Open Land West Owner Controlled Area 3
54,169 8203 Open Land West Owner Controlled Area 3
99,184 8305 Open Land South Owner Controlled Area 3
98,059 Table 2 summarizes the survey measurements and sampling conducted to meet the final status survey plan and data quality objectives outlined in LTP, Rev. 1. During the final status survey, a minimum of one judgmental sample was to be collected. According to Section 5.3 of LTP, Rev.
1, Class 3, survey units received judgmental (biased) surface scans typically performed on areas with the greatest potential of contamination. Ten percent of the total area for all survey units were scanned. Refer to Section 3.3.2.1 of this report for further detail. Section 5.6.3 of LTP, Rev. 1, and the Quality Assurance Program Plan, committed to the collection of split samples, duplicate samples, and/or replicate scan measurements at a frequency of 5% of the measurements or samples for each survey unit. All survey units met these criteria with the exception of Survey Unit 8102, 8110, 8202, and 8203, which failed to meet the commitment for replicate measurements. Refer to Section 3.3.2.7 of this report for further detail. The licensee chose to forego surrogate ratios requiring the analysis of all soil samples for C-14, the only dose significant radionuclide (LTP, Rev. 1, Section 5.2.6.2). In Situ Object Counting System (ISOCS) investigative measurements were performed and included in the judgmental total, but do not have a commensurate C-14 analysis as clarified in the licensees response to RAI-01-05 C-14 Analysis in the November 21, 2024 (ML24326A263) RAI response. The ISOCS measurements were performed for qualitative investigative purposes, and in each case a subset of areas with the highest results were selected for soil sampling.
8 Table 2. Survey Unit Final Status Survey Criteria Survey Unit Scan Coverage Random Samples Judgmental Samples HTD (C-14) analysis QC Samples QC Scan Areas 8101 9,931 m2 (10%)
14 33 47 6 (13%)
2 (10%)
8102 7,469 m2 (10%)
14 21 35 4 (11%)
1 (4%)
8103 5,850 m2 (10%)
14 27 (21 ISOCS) 20 3 (15%)
1 (7%)
8104 9,997 m2 (10%)
14 13 27 4 (15%)
1 (7%)
8105 9,994 m2 (10%)
14 23 37 4 (11%)
1 (7%)
8106 9,979 m2 (10%)
14 7
21 4 (19%)
1 (7%)
8109 9,827 m2 (10%)
14 38 (34 ISOCS) 18 5 (28%)
1 (7%)
8110 10,561 m2 (10%)
14 35 49 6 (12%)
1 (4%)
8202 5,417 m2 (10%)
14 43 57 7 (12%)
1 (4%)
8203 9,918 m2 (10%)
14 35 49 8 (16%)
1 (4%)
8305 9,806 m2 (10%)
14 28 (22 ISOCS) 20 6 (30%)
1 (7%)
Table 3 summarizes the scan MDC, which was compared to the gross activity OpDCGL(3.47 pCi/g) calculated using Equation 6-1, Gross Activity OpDCGL from Phase 1 FSSR, Rev. 1 (ML24326A263). In all survey units, the calculated scan MDC was less than the OpDCGL. Refer to Section 3.3.2.2 of this report for further discussion on detector efficiency and scan MDC.
9 Table 3. Survey Unit Scan MDC by Survey Unit Survey Unit Scan MDC 8101 2.16 pCi/g 8102 1.95 pCi/g 8103 2.10 pCi/g 8104 2.25 pCi/g 8105 2.21 pCi/g 8106 2.38 pCi/g 8109 2.13 pCi/g 8110 1.929 pCi/g 8202 2.157 pCi/
8203 2.17 pCi/g 8305 2.40 pCi/g Table 4 summarizes the maximum SOFs of all random and judgmental soil samples in each survey unit which were calculated using the OpDCGLs for soil. All values were verified to be less than 1.0, The Mean SOF was determined using the respective BcDCGLs and equated to a mean annual dose, both of which are also listed in Table 4. The Sign Test, described in MARSSIM, was applied as the statistical method for demonstrating compliance resulting in a rejection of the null hypothesis for all survey units, and a determination that all survey units were acceptable for unrestricted release.
Table 4. Results by Survey Unit Results Survey Unit Max SOF Mean SOF Mean Annual Dose 8101 0.3365 0.0374 0.9361 mrem/yr 8102 0.2154 0.0296 0.7404 mrem/yr 8103 0.1657 0.0263 0.6575 mrem/yr 8104 0.4783 0.0503 1.2572 mrem/yr 8105 0.2475 0.0388 0.9697 mrem/yr 8106 0.2199 0.0277 0.6913 mrem/yr 8109 0.4195 0.0303 0.7576 mrem/yr 8110 0.2759 0.0218 0.5449 mrem/yr 8202 0.2972 0.0418 1.0442 mrem/yr 8203 0.2485 0.0361 0.9026 mrem/yr 8305 0.7912 0.0245 0.6115 mrem/yr For Survey Unit 8106, prior to conducting the final status survey, a Radiological Assessment (RA) was performed of the Firing Range within this survey unit. A total of 118 samples were collected during the RA with all samples analyzed via the on-site gamma spectroscopy system with a single Cs-137 concentration for one sample exceeded the MDC. The maximum Cs-137 concentration (0.211 pCi/g) was well below the Cs-137 OpDCGL of 3.65 pCi/g. No other radionuclides were identified. Twelve samples were randomly selected for offsite analysis. Of
10 these samples a single sample contained a positive Cs-137 concentration at 0.0704 pCi/g. The remaining radionuclides contained no positive detection results. NRC staff verified the data from the Firing Range RA, conducted prior to FSS, provides confidence that the classification of SU 8106 was accurate and consistent with the classification as a MARSSIM Class 3 survey unit.
3.3.2 NRC Evaluation of Phase 1, Class 3, Open Land Survey Areas The NRC staff verified that the results of the FCS Phase 1 FSS demonstrate that the Class 3 OLAs included meet the DCGLs and radiological criteria for license termination. Specifically, the NRC staff reviewed the adequacy of the survey methods and instrumentation, the sufficiency of the number of samples collected, the quality control program, the comparison of the results to the release criteria, and the results of the statistical test to demonstrate compliance. A discussion of the topics that received an in-depth review is presented below.
3.3.2.1 Survey Scan Coverage The purpose of scanning during FSS is to identify locations within the survey unit that exceed the investigation levels established in LTP, Rev.1. These locations are intended to be marked and receive additional investigations to determine the concentration, area, and extent of the radiological contamination. LTP, Rev.1 indicates that MARSSIM Table 5.9, Recommended Survey Coverage for Structures and Land Areas, was utilized to determine the recommended survey coverage for open land areas, and the amount of area to be covered by scan measurements is provided in Table 5-20, Recommended Survey Coverage for Open Land Areas and Structures, of LTP, Rev.1.
MARSSIM does not specify a minimum scan coverage requirement for Class 3 survey units; instead, the guidance states that judgmental scans should be performed in areas that are most likely to indicate potential radiological contamination. All eleven of the Class 3 OLA survey units received judgmental surface soil scans of 10% of the total surface area. Section 5.3.4 of LTP, Rev.1, Scan Coverage, states For Class 3 survey units, judgmental (biased) surface scans will typically be performed on areas with the greatest potential of contamination. For open land areas, this will include surface drainage areas and collection points. Section 4.7.1 of the FSSFR, Scan Surveys elaborated by indicating scan locations were also biased to high traffic areas such as roadways and pathways. Additionally, scanning was performed around sampling locations.
Table 6.3 Radiation Detectors with Applications to Gamma Surveys, of MARSSIM Section 6.5.3, Instrument Selection, provides guidance on radiation detection instrumentation applicable to, and appropriate for, conducting FSS. The instrumentation selected by the licensee to perform scan surveys of the Phase 1 OLA survey units is the Ludlum 44-20 (3x3) sodium iodide (NaI) gamma scintillation detector coupled with a Ludlum Model 3001 Multi Detector Digital Survey Meter. This instrumentation is consistent with the guidance contained in MARSSIM regarding appropriate radiation detection instrumentation for use during FSS. In addition, in situ qualitative investigative measurements were conducted in survey units 8103, 8109, and 8305, to investigate small areas of elevated activity found during scanning surveys and post processing as discussed in the licensee's response to RAI-01-02 (ML24235A082). As qualitative measurements they were not considered in the final evaluation of the survey unit but
11 were used only for guiding investigations. Suspected areas of elevated activity identified during gamma walkover surveys were subsequently investigated with ISOCS measurements or the collection of soil samples. Where the ISOCS identified ROCs, a soil sample was collected for further investigation. According to the licensee's response to RAI-01-07 (ML24235A082), there were some cases, where scan alarms occurred, but the reading did not exceed the three standard deviations criterion, so no judgmental samples were collected.
Based on the above considerations, the NRC staff finds that the licensees approach to conducting scan coverage for the FCS Class 3 OLA survey units, as demonstrated in the FSS release records for these survey units, is consistent with the applicable MARSSIM guidance, and aligns with the associated discussion in Section 5.3.4, Scan Coverage, of LTP, Rev.1.
Therefore, the scan coverage for the FCS Class 3 OLA survey units is acceptable.
3.3.2.2 Detector Efficiency and Scan Minimum Detectable Concentration (MDC)
MARSSIM, Section 6.5.3, Instrument Selection, states that instruments used for the detection of residual radioactivity must be capable of detecting the type of radiation of interest. The measurement should be capable of measuring levels less than the DCGL. Section 6.7.2.1, Scanning for Beta and Gamma Emitters, of MARSSIM and Section 6.2.5, A Priori Scan MDCs for Land Areas, of NUREG-1507, Revision 1, provide guidance on scan MDCs for open land areas.
According to the FSSR, radiation detection and measurement instrumentation for performing FSS is selected to provide both reliable operation and adequate sensitivity to detect ROCs at levels sufficiently below the OpDCGL. The Ludlum Model 44-20 NaI detector coupled with a Ludlum Model 3001 Data Logger was selected as the primary radiation detection instrumentation for performing scanning in OLA survey units. Detector distance is detailed in the individual sample plans, but was positioned no more than 2-inches from the ground, and typical scan rate is 0.25 m/s in a 0.5-meter wide pattern. Table 5-23 of LTP, Rev.1, Typical Instrument Detection Sensitivities contains the a priori scan MDC for the Ludlum Model 44-20 NaI detector, which is 3.5 pCi/g. In response to RAI-01-01, the licensee clarifies that the a priori scan MDC for the Ludlum Model 44-20 was calculated following guidance in NUREG-1507 using Equation 6.11 for scan MDC:
Equation 1. Scan MDC The licensee established minimum detectable count rate (MDCR) and exposure-rate-to-concentration ratio (ERC) values using MicroShield inputs and calculations from FC-19-006, Ludlum Model 44-10 Detector Sensitivity (ML21271A212), but substituted the Ludlum Model 44-20 count-rate-to-exposure-rate ratio (CPMR) for a 100% Cs-137 mixture detailed in NUREG-1507 Table 6-3, NaI Scintillation Detector Count Rate versus Exposure Rate (cpm per µR/h).
The licensee states this is conservative as Cs-137 has a higher response factor than Co-60 and Eu-152 has a negligible effect due to its small fractional abundance as specified in LTP, Rev. 1, Table 5-3, Dose Significant Radionuclides and Renormalized Mixture Fractions. In addition,
12 scan MDC was conservatively calculated using a 95% Cs-137 and 5% Co-60 mixture and a 3-inch source to detector distance, resulting in an ERC ratio of 0.3033.
In order to provide sufficient information to determine the applicability of FC-19-006 to the 3 x 3 Ludlum Model 44-20 NaI detector used during these open land surveys, the licensee also submitted FC-24-006, Ludlum 44-20 Detector Sensitivity (ML24326A263), which contains a discussion showing that the scan MDC calculation described in FC-19-006 is conservative for the Ludlum Model 44-20 used during FSS surveys. Specifically, using LTP, Rev.1 mixture fraction, a scan rate of 0.25 m/s, a d of 1.38, a surveyor efficiency of 0.75, a detector height of 2 inches, and an a priori background of 76,000 cpm, the licensee calculated an ERC value of 3.144E-4 R/h and a scan MDC of 3.40 pCi/g when using a Ludlum Model 44-20. Because the initial scan MDC value of 3.45 pCi/g and ERC value of 3.033E-4 R/h, calculated using FC 006 as described above, are less than the values derived in FC-24-006, they are conservative and will meet scan MDC requirements if survey unit conditions are met (background is less than the a priori value of 76,000 cpm).
NRC staff reviewed licensee inputs into Microshield and NUREG-1507, Equation 6.11, and found them to be acceptable. Inputs such as detector height, scan rate, index of sensitivity (d),
and surveyor efficiency (p) match survey criteria outlined in LTP, Rev.1 and FSSFR. NRC staff also reviewed the licensees calculated ERC and scan MDC values from FC-24-006 and found them to be consistent with staff calculated values. Additionally, each of the individual SURR sections above contains a discussion of a posteriori scan MDC calculated based on survey unit specific background. All backgrounds were less than 76,000 cpm and all a posteriori scan MDC values were less than the gross activity OpDCGL calculated for each individual SURR.
Based on the above considerations, the NRC staff finds that the licensees approach to detector efficiency and scan MDCs for the Class 3 open land area survey units, as demonstrated in the FSS release records for these survey units, is consistent with the applicable MARSSIM and NUREG-1507 guidance and aligns with the associated discussion in LTP, Rev.1. Therefore, the detector efficiency and scan MDCs for the FCS Class 3 open land area survey units are acceptable.
3.3.2.3 Background Radiation Measurements The radionuclides of concern for the FCS Class 3 open land areas are cesium-137 (Cs-137),
cobalt-60 (Co-60), europium-152 (Eu-152), and carbon-14 (C-14). The licensee determined average background radiation for the FSS surface scans using an average of five one-minute static measurements, while maintaining the detector at six inches from the soil.
The average background measurements for the eleven open land survey units are summarized in Table 5 below.
13 Table 5. Background Measurement Range for Open Land Survey Units Survey Unit Background Range (cpm) 8101 23,740 - 29,800 8102 22,460 - 24,400 8103 18,087 - 28,192 8104 29,900 - 32,280 8105 20,580 - 31,180 8106 29,340 - 36,220 8109 27,400 - 28,920 8110 20,040 - 23,760 8202 28,160 - 29,720 8203 26,680 - 30,060 8305 31,640 - 36,880 As part of the evaluation of background measurements for the FCS Class 3 open land areas, the NRC staff noted that ideally the measurements would be from a background reference area (not at six inches above the soil surface in the survey units to be scanned during FSS).
The licensee did not subtract background radiation from the FCS soil samples that were submitted for detailed laboratory analyses, which is a conservative approach when determining the radionuclides concentrations in these soil samples for determining compliance with the release criteria. The NRC noted that the average background radiation levels determined by the licensee for the FCS Class 3 open land area survey units to be compatible with those reported by the instrument manufacturer. Based on the above considerations, the NRC staff finds that the licensees methodology for background radiation determination in the FCS Class 3 open land area survey units, as demonstrated in the FSS release records for these survey units, is acceptable.
3.3.2.4 Investigation Samples and Scan Action Levels Section 5.5.2.6, Determining Investigation Levels, of MARSSIM provides the basis for determining FSS investigation levels to indicate when additional radiological investigations may be necessary as a result of survey scan outcomes. The FSS investigation levels for each class of survey unit are presented in Table 5-24, Investigation Levels, of LTP, Rev.1, and are provided as Table 6 below. This table corresponds to Table 5.8, Example Final Status Survey Investigation Levels, of MARSSIM.
Table 6. FSS Investigation Level for Class 3 Classification Scan Investigation Levels Direct Investigation Levels Class 1
>DCGLEMC
>DCGLEMC or >Operational DCGL and
>a statistical parameter-based value Class 2
>Operational DCGL or > MDCscan if MDCscan is greater than Operational DCGL
>Operational DCGL Class 3
>Operational DCGL or > MDCscan if MDCscan is greater than Operational DCGL
>0.5 Operational DCGL
14 Section 5.5.5.2, Remediation, Reclassification and Resurvey of LTP, Rev.1 stated for a Class 3 survey unit, if an individual survey measurement exceeds 50 percent of the OpDCGL, then the survey unit, or a portion of the survey unit will be investigated. If the investigation confirms a residual radioactivity exceeding 50 percent of the OpDCGL, then the survey unit, or the impacted portion will be reclassified as a Class 1 or Class 2 survey unit and the survey will be redesigned and reperformed. Table 5-25 of LTP, Rev.1, Remediation, Reclassification and Resurvey Actions specifies the details for reclassification where necessary. There was no reclassification required for the eleven survey units in the Phase 1 FSSR.
The action levels used for the FCS Class 3 open land areas during the FSS are shown in Table 7 below. The licensee clarifies in response to RAI-01-07, Scan Action Levels, that action levels are based on the mean background of the area to be surveyed plus the associated MDCRSurveyor. Where scan alarms were prevalent using this alarm set point, a statistical parameter-based value of three standard deviations was used to evaluate gamma walkover data to locate suspect small areas of elevated activity. There were some cases when scan alarms were present, but no readings exceeded the three standard deviation criteria, so no judgmental samples were collected. Based on consistency with MARSSIM guidance, NRC staff finds the licensees approach for investigative sampling acceptable.
Table 7. Soil Action Levels for Class 3 Open Land Area Survey Units.
Radionuclide of Concern Action Level (pCi/g)
Co-60 5.30E-01 Cs-137 1.83E+00 Eu-152 1.18E+00 C-14 7.95E+00 3.3.2.5 Number of Samples and Sample Locations Section 4.5.1, Determination of Number of Data Points, of the FCS Phase 1 FSSR specifies that the number of soil samples for the FSS of the OLA survey units was determined in accordance with their procedure for final status survey sample plan development and MARSSIM. MARSSIM and NUREG-1757, Volume 2, Appendix A, Implementing the MARSSIM Approach for Conducting Final Radiological Surveys, discuss how to determine the number of sampling and measurement locations (sample size - N) necessary to ensure sufficient data for statistical analysis, such that there is reasonable assurance that the survey unit will pass the requirements for release. MARSSIM Table 5.5, Values of N for Use with the Sign Test, determines the minimum number of survey samples for chosen DQOs (Type I (, release of a survey unit containing residual radioactivity above the release criterion, or false negative) and Type II (, failure to release a survey unit when the residual radioactivity is below the release criterion, or false positive) decision error rates) assuming a calculated relative shift. The relative shift (/) for the survey unit is defined as the shift (), which is the upper bound of the gray region (UBGR), or the DCGL, minus the LBGR divided by the sigma (), which is the standard deviation of the data set used for survey design. The LBGR for all survey units was determined using survey unit specific characterization data, except for SU 8101 and 8102, which relied on 8100 Survey Area data but excluded data from survey unit 8110.
15 The licensee assumed Type I () and Type II () decision errors of 0.05 for all survey units. The relative shift was calculated based on characterization data from survey areas or survey units, as discussed above in Section 3.1.1 of this evaluation report, and exceeded 3.0 for all eleven survey units. Table 4-2, Number of Samples for FSS from the FSSR, summarizes the number of random samples for each of the eleven survey units, and is replicated below in Table 8.
Table 8. Number of Samples for FSS NRC staff submitted correspondence, dated July 8, 2024 (ML24180A203), requesting additional information associated with several survey units to verify licensee calculated relative shift and associated statistics. The licensee responded by incorporating characterization data used to determine the LBGR, the standard deviation, and the relative shift in Table 3-1 and Equation 5-1, Relative Shift of the Phase I FSSR, Revision 1 SURR reports. Based on the information supplied, NRC staff was able to verify the licensees relative shift and the associated LBGR and for each survey unit, except for SU 8203 where NRC calculated values were close, but not the same. Ultimately, NRC calculated relative shift for SU 8203 still resulted in a required sample number (N) of 14 samples.
NRC staff noted the licensee was reporting negative values as zero for final status survey results in Tables 7-2 and 7-4 of the SURRs. While no laboratory data was provided for characterization data reported in Section 3, Classification Basis, allowing for a direct comparison of reported and laboratory results, it is noted that the characterization data for all survey units did not include any negative values. NRC staff would note that if zero rather than negative values were used in the calculation of the mean and standard deviation for characterization data, this would impact the relative shift calculated in Equation 5-1. Therefore, the mean would be positively biased and the standard deviation negatively biased resulting in a non-conservative relative shift. While the impact to the relative shift is negligible and would result in the same sample numbers identified in Table 5 above, the licensee should consider reporting actual laboratory results as recommended in Section 2.5.1, Nonparametric Statistical Tests of NUREG-1505, Revision 1.
16 The NRC staff also verified that for the FCS Class 3 open land areas, the number of systematic and judgmental samples taken in each survey unit met or exceeded the number prescribed. All the FCS open land area survey units required the collection of at least fourteen systematic soil samples. For the Class 3 open land survey units, systematic soil sample measurement locations were based on simple random locations. The Visual Sample Plan (VSP) software tool was used by the licensee to determine the soil sample locations for the FCS survey units. The VSP systematic measurements are intended to be unbiased, and ensure the measurements are independent and support the assumptions of the statistical tests.
Based on the above considerations, the NRC staff finds that the licensees approach to determining the number of samples and sample locations for the FCS Class 3 open land area survey units, as demonstrated in the FSS release records for these survey units, is consistent with the applicable MARSSIM and NUREG-1757 guidance and aligns with the associated discussion in LTP, Rev.1. Therefore, the sampling methodology for the FCS Class 3 open land area survey units is acceptable.
3.3.2.6 Radionuclides of Concern and DCGLs for Soil FCS established the basis for an initial suite of potential radionuclides of concern (ROCs) for decommissioning in accordance with site technical safety documents. The ROCs were identified as described in LTP, Rev.1. The initial suite of ROCs was prepared after the elimination of some of the theoretical neutron activation products, noble gases, and radionuclides with a half-life less than two years (except for Ce-144). The initial suite is listed in LTP, Rev.1 Table 5-2 and reproduced in Table 2-1 of the FSSFR.
LTP, Rev.1, Chapter 2, provided detailed characterization data, that described current contamination levels in soils. This data was from the characterization campaign conducted in 2019 on structures and in 2020 on open land areas. Surface and subsurface soil samples were taken in each impacted open land survey unit (including soil beneath and adjacent to basements) and analyzed for the presence of plant derived radionuclides. There was no indication from the characterization or operational data that contamination was present in soils.
The Auxiliary Building (AB)/Turbine Building (TB)/Radioactive Waste Processing Building (RWPB) radionuclide mixtures were assumed for soil. FCS determined the presence of several radionuclides that are considered insignificant dose contributors based upon guidance contained in Section 3.3 of NUREG-1757. The FSSFR stated that Cs-137, Co-60, Eu-152, and C-14 were the only dose significant radionuclides with all other radionuclides considered insignificant contributors (ICs) and eliminated from further detailed review. Of the dose significant radionuclides only C-14 is also considered a hard-to-detect (HTD) radionuclide.
To validate the adequacy of methods to demonstrate, with reasonable assurance, compliance with the unrestricted release criteria in 10 CFR 20.1402, the site must have provisions for determining contributions from all radionuclides of concern, including HTDs, in the final dose calculations. Section 5.2.6.2, Surrogate Radionuclides, of LTP, Rev.1 specifies that direct analysis will be performed by offsite laboratory C-14 analysis as opposed to the application of a surrogate ratio for this single HTD in soil. Survey Units 8104, 8105, 8110 and 8203 included samples with C-14 concentrations of 1.48 pCi/g and 4.85 pCi/g, 0.856 pCi/g, 0.695 pCi/g, and
17 0.796 pCi/g, respectively, which exceeded the MDC. Although these samples had positive C-14 results, the SOF for these five samples were less than 1.0 using the OpDCGL.
NRC staff note that for Survey Units 8103, 8109, and 8305, ISOCS investigative measurements were performed. Although these ISOCS measurements do not have a commensurate C-14 analysis, soil samples were collected from a subset of the locations with higher concentrations, which included a C-14 analysis. According to FCS response to RAI-01-05 C-14 Analysis (ML24326A263), this criterion applies to random, systematic, and judgment soil samples and excludes in situ, qualitative investigative measurements. The NRC staff verified that random and judgmental soil samples included an analysis for C-14 consistent with the commitment for analysis of C-14 in LTP, Rev.1, Section 5.2.6.2, and the survey design discussed in the FSSFR.
LTP, Rev.1, Section 5.2.5, Radionuclides of Concern and Mixture Fractions, stated, for continuing characterization including radiological assessments, 10% of all media samples collected in a survey unit will be analyzed for the initial suite of radionuclides from LTP, Rev.1, Table 5-2, including ICs. If no continuing characterization occurred in a survey unit, there was no validation of ICs. A radiological assessment was performed of the Firing Range in Survey Unit 8106 and 10% of the samples were analyzed for the full suite of initial radionuclides from LTP, Rev.1, Table 5-2. No other radiological assessment was performed, and no ICs validation was done in any other survey unit.
Surface soil DCGLs corresponded to the top 0.15 m and subsurface soil DCGLs corresponded to a depth of 0 to 1 m in soil. The NRC staff note that sample data presented in the Phase 1 FSSR were for surface soils. The FSSFR indicated that the there was no expectation of encountering a source term geometry where a clean surface layer of soil over a contaminated subsurface would occur. LTP, Rev.1, Chapter 6 provided the exposure scenarios and modeling parameters used to calculate site-specific soil DCGLs. Each radionuclide-specific BcDCGL was equivalent to the level of residual radioactivity that, when considered independently, results in a total effective dose equivalent of 25 mrem/yr to the average member of the critical group. For determination of the final dose, the unity rule was applied to determine the mean base case SOF (BcSOF) and associated dose. The BcDCGL was reduced based on an expected, or a priori, fraction (0.28 for soil) of the 25 mrem/yr dose limit from each source term to obtain the OpDCGL. The OpDCGL was then used as the DCGL for FSS design of the survey unit (e.g.,
investigation levels). When applying the unity rule, the licensee used OpDCGLs, which provided additional conservatism to the sample specific SOFs. Even with the application of OpDCGL, the SOFs for all random and judgmental soil samples for all survey units were less than one. Table 9, [from Table 2-2 of the Phase 1 FSSR, which is a replication of Table 5-8 from LTP, Rev.1]
and Table 10 [from Table 2-3 of the Phase 1 FSSR, which is a replication of Table 5-7 of LTP, Rev.1], summarize the surface and subsurface soil OpDCGLs and BcDCGLs, respectively.
Table 9. OpDCGLs for Surface and Subsurface Soil ROC OpDCGLSS (0.15 m) pCi/g OpDCGLSB (1.0 m) pCi/g C-14 1.59E+01 2.71E+00 Co-60 1.06E+00 8.21E-01 Cs-137 3.65E+00 2.04E+00 Eu-152 2.36E+00 2.06E+00
18 Table 10. BcDCGLs for Surface and Subsurface Soil ROC BcDCGLSS (0.15 m) pCi/g BcDCGLSB (1.0 m) pCi/g C-14 5.70E+01 9.68E+00 Co-60 3.77E+00 2.93E+00 Cs-137 1.31E+01 7.27E+00 Eu-152 8.41E+00 7.36E+00 The NRC staff evaluated the licensees application of DCGLs in the FSSFR and SURRs for FCS using the regulatory guidance and acceptance criteria contained in MARSSIM, NUREG-1757, Volume 2, Revision 2, and the SRP. The NRC staff finds that the licensees use of base case soil specific DCGLs, that correspond to a dose of 25 mrem/yr, and use of reduced BcDCGLs (i.e., OpDCGLs) based on an expected, or a priori, fraction of the 25 mrem/yr dose limit from each source term, an acceptable method of ensuring that the final combined dose will be less than 25 mrem/yr. As such, NRC staff finds that this approach for the Phase 1 FSSRs is adequate to demonstrate compliance with the approved DCGLs in LTP, Rev. 1.
In addition, the NRC staff verified a subset of nineteen random and nine judgmental samples across SUs 8103, 8104, 8105, and 8202 against the activity and MDC values summarized in the FCS Phase 1 FSSR SURRs, Table 7-2, Summary of the Gamma Spectroscopy Results and OpSOF Calculations for Random Samples, and Table 7-4, Summary of the Gamma Spectroscopy Results and OpSOF Calculations for Judgmental Samples of each SURR. In each case, for those samples results reported in the laboratory reports as negative, the results in Tables 7-2 and 7-4 of the SURR were recorded as zero with these zero values applied to the calculation of sample SOF. The NRC staff found the reassigning a zero for negative laboratory data yielded a positively biased mean and a negatively biased standard deviation in Table 7-3, Basic Statistical Properties of Random Sample Population and Survey Unit Dose statistical results. The base case sum of fractions and dose assigned to the survey unit were also positively biased yielding a conservative dose assignment for surface soil in each of these SUs.
One discrepancy was identified in SU 8103 for the Co-60 MDC value for Sample 8103X-3-FR-GSSX-012 with the laboratory MDC lower than that in the summary table (0.139 versus 0.190).
However, the Co-60 activity concentration was less than both values and there was no impact on the SOF calculation. Additionally, the MDC values for all radionuclides were incorrect for Sample 8103X-3-FJ-GSSX-040 but all radionuclide concentrations were less than the laboratory report MDC value. The activity concentrations for the radionuclides were correct and there was no impact on the SOF calculation. The laboratory sample activity result for C-14 for Sample 8103X-3-FJ-GSSX-041 was 0.0840 pCi/g rather than 0 pCi/g reported in Table 7-4. There was a slight impact to the SOF, increasing it to 0.1465. This did not have an impact on the dose assigned to the survey unit. NRC staff compared four ISOCS measurement data from the Gamma Spectrum Analysis report with the results summarized in Table 7-5, Summary of Qualitative ISOCS Measurements, of the SURR and found no discrepancies.
Based on the above considerations, the NRC staff finds that the licensees methodology for assessing C-14 in the FCS Class 3 open land area survey units, as demonstrated in the FSS release records for these survey units, is consistent with the associated discussion in LTP,
19 Rev.1. Furthermore, the licensees approach to verification of the full suite of radionuclides during continuing characterization was consistent with LTP, Rev.1.
3.3.2.7 Quality Control Measurements Section 5.6, Quality Assurance, of LTP, Rev.1 states that the quality assurance (QA) program complies with the requirements set forth in Appendix B, Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants, of 10 CFR Part 50; Subpart H, Quality Assurance, of 10 CFR Part 71, Packaging and Transportation of Radioactive Material; and Subpart G, Quality Assurance, of 10 CFR Part 72. Also, as stated in LTP, Rev.1, Section 5.6.3.2, Duplicate and Split Samples, data was evaluated using acceptance criteria specified in NUREG 1576, Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP).
Section 5.6.3.2 of LTP, Rev.1 also states that duplicate/split sample analysis will be performed on 5% of the soil samples taken in a survey unit and that 5% of these split samples taken will be sent to an offsite laboratory or analyzed on-site using a separate detector. The NRC staff verified that the number of duplicate/split samples taken in each of the eleven survey units met or exceeded the number required for field split and duplicate analyses.
Section 5.6.3.1, QC Replicate Measurements. states that replicate measurements will be performed on 5% of the static and scan locations in each applicable survey unit at locations chosen at random. The licensee used acceptance criteria outlined in Section C.4.2.2 of MARLAP to determine the acceptability of replicate static measurements. The NRC staff verified that replicate scan measurements taken in each Class 3 of the survey unit met or exceeded the number required for replicate measurements in all cases except for Survey Units 8102, 8110, 8202, and 8203. In these survey units, staff noted that replicate scans were performed in greater than 5% of gamma walkover areas, but less than 5% of all scan areas including 1 m2 scan areas surrounding sample locations where random samples were collected and analyzed, resulting in SOF less than 1.0 in all cases. While the licensee did not meet the commitment for performing 5% duplicate measurements for scan areas when considering random sample points and gamma walkover scan areas listed in Table 7-1, Synopsis of Scan Results, of each SURR, NRC staff found the combination of replicate gamma walkover scan and the soil sampling within random sample point scan areas to be an acceptable equivalency to the 5%
duplicate measurement criteria.
In total, each FCS Phase 1, Class 3, open land survey unit analyzed between 3 and 8 duplicate/split measurement samples with a total of 63 QC samples taken across all survey units. The sample results were compared to determine accuracy and precision. In four survey units (8101, 8102, 8106, 8109), a QC assessment was not performed as neither the standard nor comparison sample contained Cs-137 above the MDC. Cs-137 results were mutually identified in the standard and comparison samples at activities less than 95% upper confidence limit (UCL) (equivalent to 0.599 pCi/g) for seven survey units (8103, 8104, 8105, 8110, 8202, 8203, 8305). Per LTP, Rev.1, since Cs-137 was mutually identified below 95% UCL, MARLAP, Section C.4.2.2, was used to complete a trending assessment that did not result in failure. NRC staff verified the QC assessment documented in SURR Table 16-3 for SU 8103, 8104, and 8105 for a total of five sample pairs and found all assessments to be accurate.
20 Based on the above considerations, the NRC staff finds that the licensees methodology for assessing QC measurement samples in the FCS Phase 1, Class 3, open land area survey units, as demonstrated in the FSS release records for these survey units, is consistent with the associated discussion in LTP, Rev.1. Therefore, the QC approach for the FCS Phase 1, Class 3, open land area survey units is acceptable.
3.3.2.8 Conclusion for Phase 1, Class 3, Open Land Survey Areas The maximum mean BcSOF for all Class 3 open land survey units reported by the licensee was 0.0503, from Survey Unit 8104 in the North Owner Controlled Area, which corresponds to a dose of 1.2572 mrem/yr. This dose was verified to be correct based on an evaluation of summary information provided.
NRCs confirmatory survey contractor, Oak Ridge Institute for Science and Education (ORISE) conducted confirmatory surveys and sampling of a subset of the Phase 1, Class 3, survey units to verify residual radioactivity concentrations for ROCs. ORISE found soil concentrations to be less than 50% of the associated Operational DCGLs with confirmatory survey soil sample SOFs generally lower than the FCS FSS SOF results. As noted for several survey units above, the NRC identified a positively biased mean and a negatively biased standard deviation where negative laboratory results were reassigned as zero. However, the bias of the mean resulted in a conservative value for the dose assigned to the survey unit and was found acceptable by NRC staff.
Section 4.4.1 of LTP, Rev.1 presented a simple ALARA analysis for the excavation and disposal of soils as low-level radioactive waste demonstrating the cost of disposing excavated soil as low-level radioactive waste was greater than the benefit of removing and disposing of soil with residual radioactivity concentrations less than the dose criterion. Since the cost is greater than the benefit, it is not ALARA to excavate and dispose of soils with residual radioactivity concentrations below the DCGL. The SOFs, applying the OpDCGLs, for all random and judgmental samples were below the DCGL. Additionally, the results of the licensees surveys and the ORISE confirmatory surveys demonstrated that the licensee had been implementing good housekeeping practices and execution of isolation and control measures in the Phase 1 survey units to prevent potential cross-contamination from other parts of the site.
For the reasons discussed in the NRC evaluation of the FCS Phase 1, Class 3, open land area survey units, the NRC staff has reasonable assurance that the FSS release records for these survey units demonstrate that surface soil residual radioactivity in the associated open land areas complies with the approved DCGLs in FCS LTP, Rev. 1. The final dose used to demonstrate compliance with the 25 mrem/yr criterion in 10 CFR 20.1402 will be the summation of the dose from all FCS site media. Dose from soil pathways is one part of this compliance dose calculation. The final compliance dose summation evaluation will occur once all FSSR phases have been submitted.
21 4.0 NRC INSPECTIONS AND CONFIRMATORY SURVEYS NRC inspectors and survey contractors from ORISE performed multiple inspection activities, as well as in-process and confirmatory surveys of the radiological conditions at FCS, throughout the decommissioning process. Sample analyses contractors from the Radiological and Environmental Sciences Laboratory (RESL) also performed confirmatory laboratory analysis of samples collected from the site.
An ORISE report discussing confirmatory surveys and RESL sample analyses of these Phase 1 open land areas was provided to NRC on January 20, 2025 (ML25030A329). The intent of the confirmatory survey was to collect independent data for use in determining whether the FCS FSS activities satisfied the criteria for unrestricted release. Confirmatory surveys were performed on June 25 and August 6-8, 2024. The ORISE survey performed independent, low density gamma scans, and sampling activities for OLA survey units 8101, 8104, 8105, 8106, 8109, 8110, and 8307. SUs 8101, 8104, 8105, 8106, and 8109 were combined into one larger confirmatory unit for the purpose of random sampling; however, site flooding and farming activities (i.e., the presence of planted crops) prevented random sample collection.
Scan surveys focused on SU boundaries near the center portion of the site and along vehicle pathways and unplanted/less vegetated areas. Except for SUs 8110 and 8307, ratemeters were also coupled to global positioning systems that enabled real-time gamma count rate and geo-referenced data capture. In total five judgmental samples were collected from two areas with elevated readings in SU 8106 and three samples taken at focus areas within SU 8109 where FCS obtained SOF values of greater than 0.5. RESL does not currently have an approved procedure for performing C-14 analysis. Thus, ORISE reviewed the C-14 data for the SUs identifying two positive C-14 detections in SU 8104 with the maximum value of 4.85 pCi/g, which is below the site investigation level of 7.95 pCi/g.
All ORISE soil sample ROC concentrations were substantially less than the respective Operational DCGLs, and SOF values were less than unity. The confirmatory survey data supported the licensees SU classification. ORISE did not identify any anomalous issues from areas investigated that would preclude the demonstration of compliance with the release criterion.
During the period of January 2022 through November 2022, when the final status surveys for Phase 1 FSSR survey units were conducted, NRC inspectors conducted six inspections documented in NRC inspection reports 050-00285/2022-001 (ML22055A979), 50-00285/2022-002 (ML22112A158), 050-00285/2022-003 (ML22162A001), 050-00285/2022-004 (ML22209A231), 05000285/2022-005 (ML22290A061), and 05000285/2022-006 (ML23004A207) dated February 25, 2022, April 28, 2022, June 15, 2022, September 14, 2022, October 26, 2022, and January 5, 2022, respectively. The inspectors performed plant tours to assess field conditions and decommissioning activities, interviewed personnel, and reviewed records pertaining to areas of review. During these inspections the following areas were evaluated:
Implementation and conduct of decommissioning and maintenance activities in accordance with license and regulatory and requirements.
22 Adequacy of controls for decommissioning activities and radiological work areas, and the assessment of changing radiological conditions.
The conduct and documentation of surveys in accordance with site procedures to justify the unconditional release of the Turbine Building and Intake Structure.
The oversight of significant radiological and containment activities by radiation safety staff.
Review of occupational exposures and ALARA planning.
Implementation of the radiation work permit program.
Radioactive waste handling and transportation.
Evaluation of licensees decommissioning staffing, personnel qualifications, and training, including contractor personnel.
Review of the environmental monitoring and groundwater monitoring programs.
Implementation of the annual program review, the quality assurance audit and oversight program, and the corrective action program.
Maintaining an adequate 10 CFR 50.59 safety evaluation program associated with decommissioning changes and work activities and periodic training for personnel preparing, reviewing, and approving safety evaluations.
The appropriate tracking of decommissioning costs.
Decommissioning activities occurring during these inspection reports included the demolition of the Turbine Building, Intake Structure, Auxiliary Building, Radwaste Building, segmentation of the reactor internals, capping of piping, and shipment of radioactive waste.
During the June 15, 2022, inspection, the inspector reviewed the licensees radiological surveys of the Turbine Building and the Intake Structure and found the licensee conducted at least two surveys of each of the two buildings, a characterization survey and an unconditional release survey. During the visit, the licensee was conducting final status surveys of land areas outside the radioactive restricted areas. The report stated that the licensee implemented the surveys using the procedures in LTP, Rev.1 at risk.
Overall, the inspectors found the licensee was implementing decommissioning and radiological work activities in accordance with license and regulatory requirements. Staffing levels and required training were commensurate with facility activities. The implementation of the corrective action program was also consistent with license and regulatory requirements. During the October 26, 2022, inspection, the NRC issued one Severity Level IV Non-Cited Violation (NCV) of 10 CFR 50.54(a)(1), concerning the licensees failure to implement the quality assurance program concerning the radioactive effluent control program. The NCV was not directly related to the performance of final status surveys.
The NRC inspectors reviewed the licensees decommissioning and radiological control activities, staffing and training, and corrective action program. In 2024, the inspectors observed FSS confirmatory surveys of a subset of the Phase 1 FSSR OLA survey units, and the implementation of isolation and control procedures after completion of FSS. The inspection reports contained no violations concerning the planning and implementation of FSSs for Phase 1, Class 3, OLAs and controls to prevent recontamination.
23 In summary, NRC inspections and ORISE confirmatory surveys corroborated that the radiological conditions of the FCS Phase 1, Class 3, survey units met the approved site-specific DCGLs.
5.0 EVALUATION OF THE NEED FOR NRC/EPA LEVEL 2 CONSULTATION The NRC and the U.S. Environmental Protection Agency (EPA) entered into a Memorandum of Understanding (MOU) for Consultation and Finality on Decommissioning and Decontamination of Contaminated Sites on October 9, 2002 (ADAMS Accession No. ML022830208). The MOU provides that, unless an NRC-licensed site exceeds any of three trigger criteria contained in the MOU, the EPA agrees to a policy of deferral to the NRC for decisions on decommissioning, without the need for consultation. For sites that trigger the criteria in the MOU, the NRC will consult with the EPA at two points in the decommissioning process: (1) prior to NRC approval of the licensees LTP or Decommissioning Plan, which the NRC terms Level 1 consultation; and (2) following completion of the FSS, which the NRC terms Level 2 consultation.
On June 26, 2023 (ADAMS Accession No. ML23082A220), the NRC sent a Level 1 consultation letter to the EPA titled Consultation on the Decommissioning of the Fort Calhoun Station Unit 1 Pressurized Water Reactor in Fort Calhoun, Nebraska. This letter was sent because the licensees proposed DCGLs for certain radionuclides at FCS (C-14, Cs-137, and Eu-152) exceeded the soil concentration values in Table 1 of the MOU related to the residential use scenario. The EPA responded to the Level 1 consultation by letter dated September 28, 2023 (ADAMS Accession No. ML23276A004).
As noted in the Level 1 consultation letter to the EPA (ADAMS Accession No. ML23082A220),
the DCGLs for all three of the proposed ROC at FCS (C-14, Cs-137, and Eu-152) exceed the MOU soil concentration levels for the residential use scenario. However, the residual radioactivity at the site is expected to be much lower than the proposed DCGL values because meeting the not to exceed 25 mrem/year criteria must be demonstrated using an all pathways, SOF approach. Each individual DCGL represents a concentration level corresponding to 25 mrem/yr. Thus, applying the SOF requirement, the actual cleanup values were reduced to ensure that the potential dose from all residual radioactivity at the site from all media is less than 25 mrem/yr.
A Level 2 consultation is not required at this time but will be completed once all final status survey reports are submitted to the NRC for approval. However, NRC staff note that none of the survey unit average concentrations in this Phase 1 submittal exceeded the SOF trigger value of 1.0 when compared to Table 1 of the EPA MOU for either the industrial use or the residential use dose scenarios.
6.0 CONCLUSION
The requirements at 10 CFR 50.82(a)(11) establish NRCs criteria for releasing all or portions a power reactor facility from their license. These criteria include: (1) dismantlement has been performed in accordance with the approved LTP, and (2) the final radiation survey and associated documentation demonstrate that the facility and site have met the criteria for decommissioning in 10 CFR Part 20, Subpart E.
24 The NRC staff has concluded that all decommissioning and dismantlement activities have been completed in the 11 survey units as part of this action, which supports the process of license termination by demonstrating that this portion of the site could be released from the 10 CFR Part 50 license. The FSS activities have confirmed that the residual radioactivity in each of the survey units meets the criteria established in LTP, Rev.1. The NRC staffs review of LTP, Rev.1 determined that the proposed DCGLs would ensure that the 10 CFR Part 20, Subpart E, release criteria would be met. The NRC staffs review of the FCS Phase 1 FSSR determined that the final survey reports were consistent, and demonstrated compliance, with LTP, Rev.1. Therefore, the FSS results demonstrate that the survey areas of this action meet the radiological criteria for unrestricted release at this time. However, recontamination of these survey units can occur where decommissioning is conducted in phases or over long timeframes. Therefore, the licensee should implement isolation and control measures consistent with FCS LTP, Rev.1, until the completion of site decommissioning to avoid recontamination of survey units and the need for additional surveys or analyses to demonstrate compliance.
Based on these considerations, the NRC staff finds that the data in the licensees Phase 1 FSSR, dated November 21, 2024 (ML24326A263) is adequate to provide reasonable assurance that the FCS Class 3 open land area survey units meet the approved DCGLs in LTP, Rev.1.
The NRC staffs findings are supported by multiple NRC inspections and ORISE confirmatory measurements that substantiated that the licensees decommissioning and FSS programs adequately assessed the radiological conditions at the site. The final dose used to demonstrate compliance with the 25 mrem/yr criterion will be the summation of the dose from all FCS site media across all SUs. Dose from soil pathways is one part of this compliance dose calculation.
The final compliance dose summation evaluation will occur once all FSSR phases have been submitted.