ML18338A246
| ML18338A246 | |
| Person / Time | |
|---|---|
| Site: | Erwin |
| Issue date: | 12/11/2018 |
| From: | Office of Nuclear Material Safety and Safeguards |
| To: | Nuclear Fuel Services |
| KRamsey NMSS/FCSE/FLB 415.7506 | |
| Shared Package | |
| ML18338A243 | List: |
| References | |
| EPID L-2018-DF1-0000 | |
| Download: ML18338A246 (4) | |
Text
1 Enclosure SAFETY EVALUATION REPORT NUCLEAR FUEL SERVICES, INC. - NORTH SITE ADDENDUM TO THE FINAL STATUS SURVEY REPORT FOR SURVEY UNITS 4, 6, 7, 12, 16, 17 AND 18 SURVEY UNITS 6 AND 7 SURFACE SOIL CHARACTERIZATION
- 1.
Introduction By letter dated October 3, 2018 (Agencywide Documents Access and Management System
[ADAMS] Accession Number ML18128A284), Nuclear Fuel Services, Inc. (NFS) submitted Revision 1 of the Addendum to the Final Status Survey Report for Survey Units 4, 6, 7, 12, 16, 17 and 18 to the U.S. Nuclear Regulatory Commission (NRC). The Addendum is a summary of surface soil surveys and investigation for Survey Units 6 and 7. The addendum was revised in response to the request for additional information from NRC staff via telephone conversation between NFS and the NRC on August 21, 2018 (ADAMS Accession Number ML18277A268).
- 2.
Background
The NFS North Site Survey Units 6 and 7 subsurface soils were characterized in the Final Status Survey Report for Survey Units 4, 6, 7, 12, 16, 17 and 18. On October 26, 2018, NRC staff confirmed that the subsurface soils were suitable for unrestricted release in accordance with Title 10 of the Code of Federal Regulations (10 CFR) Part 20, Subpart E (ADAMS Accession Number ML17298A586). However, the staff requested additional information on the surface soil (0-15 cm). The radiological criteria for unrestricted use in 10 CFR Section 20.1402 states:
A site will be considered acceptable for unrestricted use if the residual radioactivity that is distinguishable from background radiation results in a TEDE 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). Determination of the levels which are ALARA must take into account consideration of any detriments, such as deaths from transportation accidents, expected to potentially result from decontamination and waste disposal.
- 3.
Scope of the Staff Evaluation This staff review addressed the approach for performing and evaluating the radiological survey of surface soils in Survey Units 6 and 7. The radiological survey was performed in August/September 2017 and the Phase 2 investigation was conducted in January/February 2018. The radiological survey results were compared to the surface soil derived concentration guideline levels (DCGLs) from the North Site Decommissioning Plan (DP) published in 2006.
2 The radiological survey included gamma surface scans, in-situ static gamma measurements, and surface soil sample analysis. The Phase 2 investigation included systematic sampling of two areas identified by elevated measurements of Thorium-232 (Th-232). Staff evaluated the survey and investigation results to determine whether they are sufficient to meet the radiological release criteria for unrestricted use in accordance with 10 CFR 20.1402.
- 4.
Surface Soil DCGLs 4.1 Evaluation NFS is using the wide area average guideline level (DCGLw) values from the NFS North Site DP published in 2006 as shown in Table 1.
Table 1 North Site Surface Soil DCGLs Radionuclide DCGLw (pCi/g)
Am-241 (Americium) 130 Pu-238 (Plutonium) 155 Pu-239 140 Pu-240 141 Pu-241 4365 Pu-242 148 Tc-99 (Technitium) 414 Th-230 (Thorium) 17 Th-232 3.7 U-233/U-234 (Uranium) 642 U-235 74 U-238 306
4.2 Findings
The staff finds that that the use of the DCGL values from the North Site DP (2006) is acceptable.
- 5.
Gamma Scan Results 5.1 Evaluation Gamma scans were acquired using a sodium iodide (NaI) detector, digital spectrometer and a survey grade GPS system mounted on a push cart at a survey speed of approximately 1 meter per second. The plotted gamma scan results for Survey Unit 6 shows that surface activity is consistent and did not indicate specifically correlated elevated areas of gamma activity. The gamma scan data for Survey Unit 7 did indicate a small area of elevated gamma
3 measurements which resulted in the collection of a soil sample at the specific location of the elevated measurements.
5.2 Findings
The staff finds that the gamma surface scans were adequate to determine the gamma radiation levels and uniformity of the radionuclides of concern in Survey Units 6 and 7.
- 6.
In-situ Static Gamma Measurements 6.1 Evaluation In-situ static gamma measurements were performed at each corehole location utilized by the subsurface soil characterization of the North Site. There were 60 corehole locations for Survey Unit 6 and 32 corehole locations for Survey Unit 7. The in-situ static measurements were taken using a push cart positioned over each corehole for a 5 minute stationary gamma spectroscopy count. Count rates for Ra-224 and K-40 were used to isolate gamma measurements of the radionuclides of concern from naturally occurring isotopes.
6.2 Findings
The staff finds that the in-situ gamma static measurements were adequate to identify the net count rates for the radionuclides of concern in Survey Units 6 and 7.
- 7.
Surface Soil Sample Analysis 7.1 Evaluation Surface soil samples were collected from the top six inches (0-15 cm) of soil at each corehole location utilized by the subsurface soil characterization of the North Site. There were 60 corehole locations for Survey Unit 6 and 32 corehole locations for Survey Unit 7. In addition to these corehole samples, an additional soil sample was collected from the area of elevated gamma scans identified in Survey Unit 7. The analytical result of this soil sample from Survey Unit 7 exceeded the surface DCGL for Th-232 and prompted an elevated measurement investigation as discussed in section 8. All soil sample analyses were performed at the NFS Non-Destructive Analysis (NDA) Laboratory in September/October 2017 for Am-241, U-235, Th-232, and U-238. The laboratory analysis of the soil samples was performed using gamma spectroscopy. Each individual corehole sample result is below the NFS North Site surface soil DCGLs from Table 1. Each radionuclide reported a sum of fractions (SOF) below 1.0.
7.2 Findings
The staff finds that the surface soil gamma spectroscopy measurements were adequate to determine the activity of the radionuclides of concern in the soil of Survey Units 6 and 7.
4
- 8.
Phase 2 Investigation 8.1 Evaluation Two areas were identified for investigation during the radiological survey based on elevated measurements. Area A was identified by an elevated gamma scan measurement confirmed by a surface soil sample analysis in Survey Unit 7 as noted in section 5. Area B was identified after spatially mapping scan data and is located on the border of Survey Unit 7. Areas A and B are similar in size and located in surface drainage areas. Additional soil sampling in these areas was conducted in January/February 2018. There were 25 samples taken from each area and analyzed for U-235, U-238, Th-232 and Am-241. Area factors from section 5.2.6 of the NFS final status survey plan were used to calculate an elevated measurement comparison guideline level (DCGLemc) concentration for each of the radionuclides. The mean concentration of each radionuclide was below their respective DCGLemc and the SOFs were below unity (1.0).
8.2 Findings
The staff finds that the investigation of areas A and B in Survey Unit 7 is adequate to demonstrate that the soil concentrations are below their respective DCGLemc values.
- 9.
Conclusion NRC staff evaluated the survey and investigation results of surface soils in Survey Units 6 and 7 to determine whether they are sufficient to meet the radiological release criteria for unrestricted use in accordance with 10 CFR 20.1402. Surface scans and static measurements of gamma radiation levels were uniform in Survey Unit 6. The soil sample results were below the surface DCGLw and the SOFs were below unity for Survey Unit 6.
Surface scans were not uniform in Survey Unit 7 resulting in the investigation of 2 areas of elevated gamma measurements. Additional soil sampling in each elevated area to compare with the calculated surface DCGLemc of the respective radionuclides of concern. The soil sample results were below the respective surface DCGLemc and the SOFs were below unity for Survey Unit 7.
The staff finds that the surface soil for Survey Units 6 and 7 meets the radiological criteria for unrestricted use in 10 CFR 20.1402.
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