ML24261B867

Ns Savannah License Termination Plan RAIs 9-16-24

ML24261B867
Person / Time
Site:	NS Savannah
Issue date:	09/16/2024
From:	Reactor Decommissioning Branch
To:
Shared Package
ML24261B855	List: ML24261B866 ML24261B867
References
EPID L-2023-LLA-0151
Download: ML24261B867 (10)

Text

Page 1 of 10 REQUEST FOR ADDITIONAL INFORMATION RELATED TO SUBMITTAL AND REQUEST FOR APPROVAL OF THE LICENSE TERMINATION PLAN UNITED STATES MARITIME ADMINISTRATION NUCLEAR SHIP SAVANNAH DOCKET NO. 50-238 EPID L-2023-LLA-0151 By letter dated October 23, 2023 (Agencywide Documents Access and Management System Accession No. ML23298A041), as supplemented by letter dated June 27, 2024, (ML24183A271), United States Maritime Administration (MARAD, licensee), submitted a license amendment for the Nuclear Ship Savannah (NS Savannah). The proposed amendment would modify the license to add License Condition 2.C.(4) to include License Termination Plan (LTP) requirements to the U.S. Nuclear Regulatory Commission (NRC) license for NS Savannah.

The NRC staff has reviewed the information submitted and determined that additional information is required to complete its review. To support the NRC staffs technical review of the LTP license amendment request pursuant to the regulations in Title 10 Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, Section 50.82, Termination of license, please provide the additional information described in the specific requests for additional information (RAIs) listed below.

The NRC developed this set of RAIs using the regulations in 10 CFR 50.82, 10 CFR 20.1402, Radiological criteria for unrestricted use, 10 CFR 20.1501, [Surveys and Monitoring] General, Appendix B to Part 20, Annual Limits on Intake (ALIs) and Derived Air Concentrations (DACs) of Radionuclides for Occupational Exposure; Effluent Concentrations; Concentrations for Release to Sewerage, and the related guidance in NUREG-1507, Revision 1, Minimum Detectable Concentrations with Typical Radiation Survey Instruments for Various Contaminants and Field Conditions (ML20233A507), NUREG-1575, Revision 1, Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) (ML003761476), and NUREG-1757, Volume 2, Revision 2, Consolidated Decommissioning Guidance - Characterization, Survey, and Determination of Radiological Criteria (ML22194A859).

RAI 5-1: Minimum Detectable Concentration (MDC)

Basis:

The regulations in 10 CFR 50.82 (a)(9)(ii)(D) requires detailed plans for the final radiation survey to be included in the LTP. The regulations in 10 CFR 20.1501 requires adequate surveys be performed to understand and know the sites radiological condition. Applicable guidance in NUREG-1575, Revision 1, states that instrument sensitivities should be 10% to 50% of the Derived Concentration Guideline Levels (DCGLs). The description of survey methods in the final status survey (FSS) plan should provide sufficient detail so that NRC staff can verify the MDCs are accurate and that the methods to be employed will be consistent with the stated MDCs.

Page 2 of 10 Issue:

Section 5.7.1.2, Fixed Measurements, of the LTP states Fixed measurements are taken by placing the instrument at the appropriate distance above the surface, taking a discrete measurement for a pre-determined time interval, and recording the reading.

Section 5.7.2.4.2, MDCs for Beta-Gamma Scan Surveys for Structure Surfaces, of the LTP states [i]n the case of a scan measurement, the counting interval is the time the probe is over the source of radioactivity. This time depends on scan speed, the size of the source, and the fraction of the detectors sensitive area that passes over the source; with the latter depending on the direction of probe travel.

The NRC staff notes that methods for scanning and fixed measurements described in the LTP do not include sufficient information to show how the MDCs in Table 5-4, Available Instruments and Associated MDCs, would be met. Without an adequate understanding on the specifics of the distance of the detector to the surface, scanning speed (in terms of detector width per second), or a minimal time interval to which the operator will set an instrument scaler for fixed measurements, the NRC staff cannot verify methods employed will be consistent with the stated MDCs.

Request:

Clarify the methodology used for scanning measurements specific to the detector distance from surfaces and scanning speed to achieve the MDCs in Table 5-4 of the LTP. Provide details of detector distance and scaler settings for fixed measurements to achieve the MDCs in Table 5-4.

RAI 5-2: Quality Assurance and Quality Control Measures for ISOCS Basis:

The regulations in 10 CFR 50.82 (a)(9)(ii)(D) requires detailed plans for the final radiation survey to be included in the LTP. The regulations in 10 CFR 20.1501 requires adequate surveys be performed to understand and know the sites radiological condition. Applicable guidance in NUREG-1507 discusses in situ gamma spectroscopy and potential areas of significant measurement uncertainty that could be addressed through a measurement programs quality assurance (QA) and quality control (QC) process.

Issue:

Section 5.11, Quality Assurance and Quality Control Measures, of the LTP discusses QA/QC activities for the FSS effort to ensure that surveys are performed by trained individuals using approved written procedures and properly calibrated instruments that are sensitive to the suspected contaminant. There is no discussion of QA for in situ object counting system (ISOCS) measurements including training and experience requirements for the ISOCS operator and verification of results to confirm radionuclides/depth profiles of contamination match the modeled configuration.

Page 3 of 10 Request:

Clarify the QA process for use of ISOCS measurements. Describe the training and experience requirements of individuals using the ISOCS system. As well as, how the ISOCS results are verified including the number of duplicates measurements and how the radionuclides/depth profiles of contamination are confirmed to match the modeled configurations.

RAI 5-3: DCGL-elevated measurement comparison (DCGLEMC) and Area Factors Basis:

The regulations in 10 CFR 20.1402 requires radiological license termination criteria not to exceed 25 mrem/year and that the residual radioactivity be reduced to levels that are as low as reasonably achievable (ALARA). NUREG-1757, Volume 2, and NUREG-1575, Revision 1, provide guidance on methods for demonstrating compliance with these criteria including what can be considered appropriate investigation levels.

Issue:

In its letter dated May 30, 2024 (ML24157A103), the NRC staff asked in RAI 5-3 for the licensee to confirm plans to remediate materials with measurements above the DCGLW until residual radioactivity is less than the DCGL-wide (DCGLw) or provide instructions on how any elevated measurements will be addressed in demonstrating compliance with 10 CFR 20.1402.

In its RAI response dated June 27, 2024 (ML24183A271), MARAD stated, All external surfaces above the DCGLW have been or will be remediated to less than the DCGLW. Any internal surface in a system above the DCGLW will be remediated or removed and properly disposed.

Our investigation level is set at 75% of the DCGLW which gives us confidence that measurement locations greater than the DCGLW will either be remediated or removed.

Section 5.5.3.3, Remediation, of the LTP, states If during the performance of an FSS, any areas of residual activity are found to be in excess of the DCGLW and an outlier, those areas will be remediated with the goal to reduce the activity to less than or equal to the DCGLW.

Remediation actions are discussed in Section 4 and documented as described in Section 5.10.

In addition, Table 5-2, Investigation Levels, of the LTP identifies investigation levels for fixed and scanned measurements for the three survey unit classifications and systems and components. Table 5-2 states that for a Class 3 survey unit, an investigation will be performed for fixed and scanned measurements if the results are greater than 25% of the operational DCGLw. The NRC staff notes that the licensee response to RAI 5-3, is inconsistent with Table 5-2 and Section 5.5.3.3 of the LTP.

Request:

Clarify your June 27, 2024, response for RAI 5-3, with regards to investigation levels as compared to that stated in Table 5-2 and described in Section 5.5.3.3, of the LTP.

Page 4 of 10 RAI 5-4: Sensitivity Index Basis:

The regulations in 10 CFR 50.82 (a)(9)(ii)(D) requires detailed plans for the final radiation survey to be included in the LTP. The regulations in 10 CFR 20.1501 requires adequate surveys be performed to understand and know the sites radiological condition. NUREG-1575, Revision 1, provides guidance on determining scan MDC which incorporates use of a sensitivity index (d) as a factor in the scan MDC equation.

Issue:

Section 5.7.2.4.2, MDCs for Beta-Gamma Scan Surveys for Structure Surfaces, of the LTP, states that the sensitivity index of 1.38 was chosen for use in the scan MDC Equation 5-8. The NRC staff notes that significant training is needed to ensure appropriate surveyor techniques and appropriate sensitivity to elevations in count rate to ensure the value of 1.38 is appropriate.

For informational purposes, NRCs contractor, who helped author MARSSIM methods in this technical area, typically utilizes 2.32 as the d value in their scan MDC determinations.

Request:

Provide justification for using a sensitivity index of 1.38 in the scan MDC equation.

RAI 5-5: Scan and Fixed MDC measurements Basis:

The regulations in 10 CFR 50.82 (a)(9)(ii)(D) requires detailed plans for the final radiation survey to be included in the LTP. The regulations in 10 CFR 20.1501 requires adequate surveys be performed to understand and know the sites radiological condition. NUREG-1575, Revision 1, provides guidance on determining both the scan MDC and fixed measurement MDC which incorporates use of both an instrument efficiency and a source efficiency as a denominator in the equations.

Issue:

Table 5-4 of the LTP, Available Instruments and Associated MDCs, includes information on instrumentation, application, nominal efficiency, background, scan and fixed MDC measurements. The NRC staff notes that Table 5-4 does not indicate if source efficiency corrections were included in the nominal fixed and scan MDC values. In addition, source efficiency values for maximum beta energies between 150-400 keV are not indicated. When utilizing the default source efficiency for low energy beta radiation and a sensitivity index of 2.32, it appears that the Geiger-Mueller pancake scanner may be unsuitable for use for FSS scanning.

The NRC staff notes that both the MDC values presented for the High Purity Germanium (HPGe) detector is in units of pCi/g (which is inconsistent with the proposed DCGL units) and that certain instruments mentioned in the LTP which are suitable for scanning or other use in this situation are not listed.

Page 5 of 10 Request:

a) Clarify if the nominal MDC and nominal Scan MDC values in Table 5-4 include source efficiency correction. If Table 5-4 nominal MDC and Scan MDC values do not include a source efficiency, recalculate the values to include the source efficiencies. In addition, recalculate the nominal MDC and Scan MDC in Table 5-4 with the appropriate sensitivity index value from your response to RAI 5-4.

b) Provide the correction/correlation of the nominal MDC values for HPGe radiation detectors in dpm/100cm2.

c) If pipe crawlers are planned to be used for FSS surveys, update Table 5-4 with the appropriate information.

d) Explain how/when Sodium Iodide (NaI) detectors may be used for scanning purposes and update Table 5-4, if appropriate.

RAI 5-6: Water and Sludge Remaining at License Termination Basis:

The regulations in 10 CFR 20.1402 requires radiological license termination criteria not to exceed 25 mrem/year and that the residual radioactivity be reduced to levels that are ALARA.

NUREG-1757, Volume 2, and NUREG-1575, Revision 1, provide guidance on methods for demonstrating compliance with these criteria.

Issue:

Section 5.7.1.4 of the LTP, Samples, states If water or sludge is encountered in a system during FSS, sample results will be compared the Effluent Concentrations (ECs) listed in Table 2, Column 2 of Appendix B to 10 CFR 20. If the sample results are greater than the ECs, the medium will be remediated or removed. The LTP states that the site contains no surface or ground water. The LTP does not discuss what MARAD plans to do if samples of water or sludge are below the ECs.

The NRC staff notes that there is no discussion in the LTP of how comparison of the effluent concentrations in Table 2, Column 2 of Appendix B to 10 CFR 20 will be incorporated into the demonstration of compliance with the 25 mrem/yr TEDE dose limit. The LTP discusses dose from contaminated ship surfaces. If contained water or sludge is encountered in a system during FSS, the NRC staff are concerned that the total compliance dose equation may underestimate dose to an average member of the critical group because it does not currently account for dose from this potential additional source term. This supports insights regarding the exposure scenarios that MARAD designated as risk-significant (e.g., those that provide inputs to the DCGLs)

Request:

Provide a discussion of how residual radioactivity from water and/or sludge remaining at license termination will demonstrate compliance with 25 mrem/yr.

Page 6 of 10 RAI 5-7: Samples of and Compliance Demonstration for Pipes and Systems Basis:

The regulations in 10 CFR 20.1402 requires radiological license termination criteria not to exceed 25 mrem/year and that the residual radioactivity be reduced to levels that are ALARA.

NUREG-1757, Volume 2, and NUREG-1575, Revision 1, provide guidance on methods for demonstrating compliance with these criteria.

Issue:

Assuming functionality is not an issue, if residual radioactivity may remain in any pipe or system at license termination, then that pipe or system should be sealed and made generally inaccessible in the future by means such as grouting or use of similar materials to fill the void spaces. This will similarly make any future potential exposure much less probable as the pipe/system would then be more likely to be disposed of as waste instead of reused in the future.

Section 3.1.2 Completed Dismantlement Activities of the LTP states that the aft Reactor Coolant System piping may remain onsite at license termination or may be one of the last low-level radioactive waste shipments. In the event that this piping system remains onsite and contains residual radioactivity, the NRC staff does not have a clear understanding of how the licensee plans to characterize the residual radioactivity nor the criteria MARAD will use to estimate dose to an average member of the critical group from the residual radioactivity to comply with the 25 mrem/yr TEDE dose limit.

Section 4.2.3 "High Pressure Water Blasting" of the LTP states that if the licensee discovers residual radioactivity in a pipe in excess of the release criteria and the system is going to remain, the licensee will perform in situ remediation. However, Section 5.6 Survey Protocol for Non-structural Systems and Components of the LTP states that MARAD expects limited use of in-situ gamma spectroscopy or pipe crawlers.

Section 5.6 Survey Protocol for Non-structural Systems and Components of the LTP states that Evaluations as to whether 1) material should be considered as a structure or a component will be made and 2) comparisons with the dose modeling scenarios used to develop the DCGLs that govern release of structures. The NRC staff are seeking clarification as to how material will be categorized. The NRC staff are also seeking clarification on how the licensee will account for systems and components containing residual radioactivity at license termination but not considered in the dose modeling scenarios.

At other sites, all non-structural components are typically removed prior to FSS. If components may be left (e.g., piping), those are considered separate survey units that, once surveyed, are combined with the structural or open land survey unit in which they reside so the SOFs are added when assessing compliance. Such pipes are also typically sealed and grouted to some extent if they cant be fully accessed and surveyed.

Request:

1. Provide any updates to the end state configuration plans of any pipe or systems to remain at license termination, including plans to fill any pipe or system to make inaccessible.

Page 7 of 10

2. Discuss how material will be considered as a structure or a component possibly including decision criteria.

3. Explain how the residual radioactivity from systems and components not included in the dose modeling scenarios will be accounted for dose compliance with the 25 mrem/yr TEDE dose limit.

RAI 5-8: Remaining Dismantlement Activities Basis:

The regulations in 10 CFR 50.82(a)(9)(ii)(B) requires identification of remaining dismantlement activities. Applicable guidance on identification of remaining site dismantlement activities can be found in NUREG-1700, Revision 2, Section 2.3, and NUREG-1757, Volume 2, Revision 2, Appendix G.3.5, Recontamination.

Issue:

Section 5.4.4, Area Preparation: Isolation and Control, of the LTP, states, Once the area meets the isolation and control criteria, isolation and control will be achieved through a combination of personnel training, physical barriers, postings, and site notices as appropriate, to prevent unauthorized access to an isolated survey unit. Isolation and control measures will be implemented through approved plant procedures. An administrative process will be used to evaluate, approve (or deny), and document all activities conducted in these areas during and following FSSs.

The NRC staff notes that Section 5.4.4 does not discuss periodic surveillance and surveys to verify that no new residual radioactivity has been reintroduced to a survey unit/area once FSS activities have been completed.

Request:

Provide criteria for surveillance and surveys that must be met and what corrective actions will be taken if criteria are not met. Discuss periodic surveillance and surveys to verify that no new residual radioactivity has been reintroduced to a survey unit/area once FSS activities have been completed.

RAI 5-9: Operational Checks Basis:

The regulations in 10 CFR 20.1501 require appropriate surveys appropriate to evaluate the concentrations and quantities of residual radioactivity. NUREG-1575, Revision 1, Sections 4.7.1, 6.2.2.2, and 6.5.4 provide guidance on operational and calibration checks on instruments.

Issue:

Section 5.7.2.3, Operational Checks, of the LTP states Instrumentation will be checked for proper operation in accordance with approved procedures. If the instrument operational check does not fall within the established range, the instrument will be removed from use until the reason for the deviation can be resolved and acceptable operation is again demonstrated. If the instrument fails a post-survey source check, all data collected during that time period with the

Page 8 of 10 instrument will be carefully reviewed and possibly adjusted or discarded, depending on the cause of the failure.

Section 13 of the NS Savannah Project STS-003-001, Revision 4, indicates that instrumentation will be properly controlled, calibrated, and adjusted during specified periods to maintain accuracy within necessary limits. NUREG-1575, Revision 1, Section 6.2.2.2, Bias, defines calibration checks as measurements performed to verify measurement performance each time an instrument is used.

While the LTP commitments are likely consistent with guidance in that the licensee commits to routine operational checks, typically operational checks are done daily or per shift, at a minimum, to assure response is within acceptable ranges and that any changes in background are not attributable to contamination of the detector.

Request:

Clarify that operational checks of survey instruments are being conducted daily or per shift when used.

RAI 5-10: Survey Unit Failure Basis:

Regulations at 10 CFR 20.1402 state a site to be acceptable for unrestricted use if the residual radioactivity results in a TEDE that does not exceed 25 mrem/y and be ALARA. NUREG-1575, Revision 1, Section 8.5.3 provides guidance on what should be considered If the Survey Unit Fails.

Issue:

Section 5.10, Final Status Survey Release Records and Reports, of the LTP, states, When a survey unit fails, the FSS report will include the following: a description of any changes in initial survey unit assumptions relative to the extent of residual radioactivity; a summary of the investigation conducted to ascertain the reason for the failure; a summary of the effect that the failure has on the conclusion that the facility is ready for final radiological surveys; and, a summary of the effect of the failure has on other survey unit information.

The NRC staff note that if a survey unit fails, then the survey unit cannot be determined to meet the license termination criteria, and thus license termination cannot be granted. If a survey unit fails, then the cause should be evaluated and corrections performed, to possibly include additional remediation and resurveying, in order to demonstrate compliance with the DCGLs and the license termination criteria. Only FSSRs which ultimately demonstrate meeting the release criteria should be submitted to the NRC.

Request:

Clarify actions that will be taken if a survey unit fails.

Page 9 of 10 RAI 5-11: Ambient Background Subtraction Method Basis:

The regulations in 10 CFR 50.82 (a)(9)(ii)(D) requires detailed plans for the final radiation survey be included in the LTP. The regulations in 10 CFR 20.1501 requires adequate surveys to be performed to understand and know the sites radiological condition. NUREG-1507, Revision 1, Section 4.5, Ambient Background Count Rate, provides guidance on ambient background effects and Section 5.1, Background Count Rates for Various Materials, further discusses ambient background. In addition, Appendix A, Section A.2, Methods, discusses some acceptable methods to determining ambient background.

Issue:

Section 5.8.1, Sign Test, of the LTP, discusses the evaluation of gross activity measurements after subtracting the ambient background from each measurement. Note that NUREG-1575, Revision 1, provides guidance that gross measurements should be evaluated using the Wilcoxon Rank Sum test which would likely alleviate ambient background subtraction as a possible issue if performed incorrectly.

Request:

Clarify how ambient background will be appropriately/conservatively determined for each gross activity measurement.

RAI 5-12: ALARA Analysis Basis:

The regulations in 10 CFR 20.1402 requires radiological license termination criteria not to exceed 25 mrem/year and that the residual radioactivity be reduced to levels that are ALARA.

NUREG-1757, Volume 2, Revision 2, Appendix N, provides guidance on methods for demonstrating compliance with the ALARA portion of the regulation.

Issue:

Section 4.4, ALARA Evaluation, of the LTP, states that the licensee will meet a pre-determined compliance measure of 15 mrem/y which is ALARA when the license termination criteria is 25 mrem/y. The NRC staff notes that this is inconsistent with the guidance in NUREG-1757, Volume 2, Appendix N which should be used to evaluate the residual radioactivity remediation methods in order to determine a pre-determined compliance measure. If the ratio of ALARA concentration to 25 mrem/y DCGL is 3/5 or greater, then it is demonstrated that the 15 mrem/y licensee-imposed limit will be ALARA. Otherwise, it is uncertain if ALARA would be an even smaller dose concentration. The NRC staff notes that the licensee could determine the ratio of the ALARA concentration to the 15 mrem/y DCGLs to demonstrate ALARA when the ratio is 1 or greater.

Page 10 of 10 Request:

Perform an ALARA analysis consistent with guidance in NUREG-1757, Vol 2, Appendix N to demonstrate that 15 mrem/y DCGLs are ALARA or adjust the DCGLs to correspond to a dose limit that is considered ALARA as determined by the ALARA analysis.

RAI 10-1: NRC Approval of LTP Changes Basis:

The regulations in 10 CFR 50.82(a)(10) outlines the requirements for changes to the LTP.

Applicable guidance on areas that cannot be changed without NRC approval can be found in NUREG-1700, Revision 2, Appendix B, LTP Areas That Cannot Be Changed Without NRC Approval. NUREG-1575, Revision 1, Section 4.7.1 provides guidance that a measurement system with an MDC between 10-50% of the DCGL should be selected.

Issue:

Chapter 10, LTP Areas That Cannot be Changed Without NRC Approval, of the LTP, Bullet 5 states, Increase the derived concentration guideline levels. Nominal values for the MDCs have been presented in Table 5-4 in the LTP. Using the methodology for calculating MDCs presented in Chapter 5 in the LTP, the actual MDCs will be calculated prior to performing the FSS.

Therefore, increasing the MDCs does not require NRC approval.

The NRC staff notes that several terms for the MDC determination appear to have been omitted or non-conservatively selected. At a minimum, the NRC staff should be informed if the actual MDC values for instruments used to perform FSSs are potentially going to exceed 50% of the proposed DCGLs.

Request:

Make appropriate changes to Table 5-4 to present nominal values using appropriate terms for the scan MDC and fixed measurement MDC. Subsequently, ensure bullet number 5 is consistent with the guidance in NUREG-1700, Revision 2, Appendix B regarding contacting the NRC if increasing the MDC above what was approved.