ML21225A773
| ML21225A773 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay |
| Issue date: | 08/24/2021 |
| From: | Amy Snyder Reactor Decommissioning Branch |
| To: | Welsch J Pacific Gas & Electric Co |
| Amy Snyder, 301-415-6822 | |
| Shared Package | |
| ML21225A771 | List: |
| References | |
| Download: ML21225A773 (37) | |
Text
SAFETY EVALUATION BY OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS RELATED TO FINAL STATUS SURVEYS FOR TEN SURVEY UNITS LOCATED IN THE TRAILER CITY AREA PACIFIC GAS AND ELECTRIC COMPANY HUMBOLDT BAY POWER PLANT, UNIT 3 DOCKET NO. 50-133
1.0 INTRODUCTION
The U.S. Nuclear Regulatory Commission (NRC) staff reviewed Final Status Survey Reports (FSSRs) for ten survey units in what is informally known as the Trailer City Area (formerly known as the Hazardous Waste Area in the License Termination Plan [LTP]) for Humboldt Bay Power Plant (HBPP), Unit 3 facility, as provided by letter dated May 21, 2020 (Agencywide Documents Access and Management System [ADAMS] Accession No. ML20142A287). These survey units are designated as OOL09-01 through OOL09-10: the discharge canal headworks (OOL09-01); the settling basins (OOL09-02); Soil Management Facility (SMF) West (OOL09-03); SMF East (OOL09-04); Bull Pen West (OOL09-05); Bull Pen East (OOL09-06);
Ground Water Treatment System (GWTS) North (OOL09-07); GWTS South (OOL09-08);
Asbestos Area (OOL09-09); and the Trail Buffer Zone (OOL09-10). The Pacific Gas and Electrics (the licensees) Final Status Survey (FSS) design criteria, implementation of the Data Quality Objectives (DQO) process, and survey approach/methods were reviewed, and the final results were assessed against the licensees approved release criteria. The licensee provided both a survey of the excavation as well as the survey of the backfilled area (designated as a Final Site Restoration [FSR] survey), or essentially two FSSR surveys of each survey unit. The NRC staff evaluated each survey performed as a stand-alone survey unit with the more restrictive of the two surveys being the bounding dose for the survey unit. If both surveys demonstrate meeting the unrestricted release criteria, then the survey unit would meet the unrestricted release criteria because a more generalized approach would have the surveys combined in some manner to average the hypothetical dose from each (both surveys were conservatively performed/evaluated as surface land areas). The NRC staffs analysis is provided below.
2.0 EVALUATION OOL09-01 (Discharge Canal Headworks)
The survey unit designated as OOL09-01 was classified by the licensee as a Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) Class 1 unit and is described as an approximately 1,922 m2 area. The licensee describes the survey unit as being bounded by OOL01-03 and OOL09-07 on the North, OOL09-02, OOL09-03, and OOL-09-09 on the East, OOL09-09 National Grain and Feed Association (NGFA)-East and NGFA-West on the South, and NGFA-West, OOL04-01, and OOL07-02 on the West. Survey unit OOL09-001 consists of the south end of the discharge canal and the open land area east of the discharge canal. The licensee further described this area as an area where the following activities were conducted before the FSS: the excavation of Unit 1, 2, and 3 underground circulating water piping (that ran through the survey unit to the discharge canal headworks), the removal the above and Enclosure
below ground discharge canal headworks, and remediation of any other commodities, as necessary. After the waste materials were removed, the FSS of the excavation was conducted and, after the FSS activities for the excavation were completed, the area was immediately backfilled with poured concrete and reclaimed soil from various locations on-site that had passed through the Gamma Radiation Detection and In-Container Analysis (GARDIAN) system.
After remediation of the area was completed, a second survey of the surface of this area was performed with the survey unit redesignated as OOL09-01-FSR. As such, the FSS of this survey unit can be best described as being two FSSs, one of the excavation footprints, and another of the remediated area after backfilling.
The licensee, in its LTP, identified 21 radionuclides of concern (ROCs). This was further broken down into hard-to-detect (HTD) ROCs and easy-to-detect (ETD) ROCs where the ETD ROCs are adequately analyzed for by gamma spectroscopy. The breakdown is as shown in the table below.
HBPP ROCs HTD ROCs ETD ROCs Radionuclide DCGL (pCi/g, soil) Radionuclide DCGL (pCi/g, soil)
Cm-243/244 29 Am-241 25 CM-245/246 17 Co-60 3.8 C-14 6.3 Cs-137 7.9 H-3 680 Eu-152 1.0 Ni-59 1,900 Eu-154 9.4 Ni-63 720 Nb-94 7.1 Pu-238 29 Np-237 1.1 Pu-239/240 26 Pu-241 860 Sr-90 1.5 Tc-99 12 The licensee determined, by using the DQO process, that Cs-137, Co-60, Eu-152, Eu-154, and Sr-90 were plant derived nuclides that could potentially be present in this survey unit. The licensees survey design was based on a sum of fractions (SOF) determination and a value less than unity would result in meeting the radionuclide dose criteria. The licensee determined the required number of soil samples using a Type 1 and Type 2 error rate of 0.05 and a relative shift of 1.25. The licensee determined that the required number of samples was 22. The licensee collected 23 randomly selected soil samples. The NRC determined that these activities are consistent with Table 5.5 of MARSSIM.
The licensee deselected the HTD ROCs with only seven remaining radionuclides to be quantified through sampling/analysis. However, the licensee noted only five radionuclides (four ETD ROCs) could potentially be present. This approach left Am-241, Nb-94, and Np-237 unreported and unaddressed. The licensee clarified its approach as described above by stating these ROCs were generally not found in analytical results greater than the minimum detectable concentration (MDC) so the licensee presumed the impact to be negligible and did not report them. This is contrary to the LTP in that the results should either have been presented in the FSSR or the ROCs considered deselected and their impact addressed; however, NRC staff agree, after review of available data, that these ROCs seem to contribute minimally, on average, to the assessment and believe an appropriate conservative assessment would be to bound their hypothetical dose impact by assuming 1 mrem/y from unreported ROCs.
The hypothetical dose estimated from the 14 deselected ROCs was initially 2.15 mrem/y in the submittal; however, the NRC staff noted that the licensee has since revised its hypothetical dose estimate for the deselected HTD ROCs (see ADAMS Accession No. ML21063A474, ). In the referenced attachment in Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y. The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any survey unit as being 2.9 mrem/y. The NRC staff believe it more appropriate to conservatively bound the impact of the HTD ROCs at 2.9 mrem/y.
Of the systematic samples collected in this survey, the licensee reported that the maximum SOFs from the analytical results is approximately 0.218 and the average being slightly less than zero (i.e., negative). The NRC staff find that use of negative average values when calculating a SOF value to be misleading and the licensee should have zeroed out the negative averages prior to summing the fractions. However, the overall impact when doing this is essentially negligible as the NRC staff calculated a maximum SOF value of 0.256 and the average SOF to be 0.0025. The small amount of non-conservative bias introduced by using the negative average results when comparing to the release criteria is not sufficient to change the licensees conclusions, in this case.
Based on the initially reported data, the licensee stated the maximum hypothetical dose was 1.63 mrem/y (2.15 mrem/y from deselected radionuclides less 0.52 mrem/y from the slightly negative average SOF value). It is because of this manipulation of hypothetical dose that the NRC staff do not consider use of negative average values when comparing to the release criteria to be appropriate. The NRC staffs determination of the maximum hypothetical dose is 5.0 mrem/y (2.9 mrem/y bounding dose from HTD ROCs plus 0.06 mrem/y from the average SOF for the ETD ROCs when not utilizing negative average values, 1 mrem/y bounding dose from non-reported ROCs, and 1 mrem/y from a bounding consideration of residual radioactivity in groundwater (described below)). Regardless, the hypothetical dose in the survey unit from residual radioactivity in soil/groundwater is far below the 25 mrem/y unrestricted release criteria.
While ingestion of contaminated groundwater was identified as a pathway of concern for the average member of the critical group in the LTP, it was not addressed in the original FSSR submittal other than the fact that ingestion of groundwater was considered in the development of the Derived Concentration Guideline Levels (DCGLs). In response to NRC staffs Request for Additional Information (RAI) 1 (ADAMS Accession No. ML20247J598), the licensee provided groundwater monitoring results from 2015, 2016, and 2017, three years during which the licensee maintains groundwater was most likely to have been impacted due to decommissioning work. Groundwater well monitoring was discontinued in accordance with the LTP during the site decommissioning due to various construction type activities occurring which made maintaining the wells impractical.
Based on the reported groundwater sample results, none of the wells sampled during this period demonstrated detectable contamination for Co-60, Cs-137, or H-3. The licensee also monitored for gross alpha and beta activity during this period and some detectable alpha activity was reported in 2015 while detectable beta activity was sporadically reported, although mostly not detectable, in wells during the 2015-2017 period. The NRC staff reviewed the reported MDC values and noted that the MDCs for Co-60, Cs-137, and H-3 were typically around 5 pCi/L, 5 pCi/L, and 300 pCi/L, respectively. Conservatively assuming these concentrations in groundwater, the staff compared these MDC values to the respective liquid effluent concentration values in Title 10 of the Code of Federal Regulations (CFR) 20, Appendix B, Table 2 to derive an estimated hypothetical dose of less than 1 mrem/y from ingesting residual radioactivity in groundwater. While the groundwater monitoring results were not encompassing of all the ROCs for the site, NRC staff consider it adequate to conservatively assume the identified radionuclides are present at the typical MDC value because gross alpha/beta results were not indicative of any significant activity exceeding the MDC values or missed ROCs.
Also, while the NRC staff agree with the licensee that it is unlikely ingestion of contaminated groundwater at the site would occur due to tidal basin flow affecting groundwater potability and limited impact of past plant operations to the available drinking water aquifers, the NRC staff consider it reasonably conservative to assume some contaminated groundwater could be present and ingested by future site occupants because the licensee did not justify disregarding this potential pathway. As such, NRC staff find it reasonable to conservatively bound a hypothetical dose contribution through ingestion of existing residual radioactivity in groundwater equivalent to the typical MDC values and corresponding to 1 mrem/y even though this was not addressed by the licensee in its FSSR. The NRC staff included this contribution in their estimate of hypothetical dose for this survey unit as noted previously.
The licensees LTP requires 100% of Class 1 areas to receive a gamma walkover scan coverage during FSS; however, this was not accomplished in the literal sense despite the licensee stating it was 100% scanned. According to the submittal, approximately 68% of the area was covered by walking transects and traditional scanning and 15% of the area was covered using an In Situ Object Counting System measurements (gross soil measurements).
The remainder of the area was inaccessible due to backfill being placed prior to surveys being performed. To compensate, the licensee obtained additional biased samples in the backfilled area consistent with discussions with the NRC. One investigative sample was obtained due to the high gamma flux obtained during the walkover survey. While the sample indicated exceedance of the release criteria, sample collection involved an excavator bucket of soil being removed from the survey unit to facilitate sample collection (i.e., sampling the removed soil).
Subsequent measurements in the area did not identify any significant elevation implying that the area of concern was remediated during sampling. The NRC staff considered that, while the scanning was not performed in compliance with the LTP in this survey unit, there is no indication overall that residual radioactivity exceeds the release criteria and, in this case, compensatory measures taken are considered adequate based on previous discussions with the NRC staff and management.
In addition to gamma measurements and systematic and investigative sampling, the licensee obtained five biased samples and performed analyses for HTD radionuclides on two randomly selected split samples, which included alpha spectroscopy, gas proportional counting, or liquid scintillation depending on the radionuclide. This frequency of HTD analyses is consistent with guidance from MARSSIM Section 4.3.2. The NRC staff reviewed the sample analysis for these samples and verified that no ROCs were present greater than the applicable detection limits (MDC) other than Cs-137 which was considered in the surveys that were performed. Also, the split evaluations had adequate agreement. Lastly, the licensee noted that it took approximately 70 samples from the soil adhering to the sheet pilings placed to accommodate excavation work.
Only three of these samples were noted as exceeding the detection limit for Cs-137 at levels that were only a small fraction of the DCGL value and didnt warrant investigation.
The licensees survey results indicated that Cs-137 was not identified above the detection limit in any of the soil samples collected for non-parametric statistical testing. Only one soil sample was triggered as an investigation based on scanning surveys and that was resolved as no indication of remaining elevations was noted after initial sample collection. Because no systematic sample exceeded the DCGL, the statistical test (i.e., Sign Test) was not required. As such, the licensee acknowledged that the Sign Test was performed (by inspection) on the data and compared to the original assumptions of the DQOs, and that performing the test is unnecessary as it is passed by inspection.
The licensee determined that the survey unit meets the unrestricted release criteria with an estimated hypothetical dose of 1.63 mrem/y. The NRC staff determined a hypothetical dose of 5.0 mrem/y for the survey unit (2.9 mrem/y from HTD ROCs, 0.06 mrem/y from ETD ROCs, 1 mrem/y from non-reported ROCs, and 1 mrem/y from groundwater). Both estimates (the licensees and the NRC staffs) are significantly below the unrestricted release criteria of 25 mrem/y.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-01-FSR (Discharge Canal Headworks after Final Site Restoration)
As previously noted, after completing remediation of the discharge canal by excavation, the licensee subsequently backfilled the excavation utilizing concrete and soil from on-site that had been screened through the GARDIAN system which is a bulk material measurement system used to screen trucks containing soil. The footprint of the survey of OOL09-01-FSR remained essentially identical to that of OOL09-01. The survey that is reported for OOL09-01-FSR is of the surface of the backfilled material which originated on-site. The NRC staff note that an additional layer of clean backfill was subsequently placed on the filled area after this survey using material that originated off site. The licensee considered this a Class 1 survey unit as the material used as backfill originated from Class 1 areas.
The licensee performed DQOs for the restored areas in the Trailer City and noted that Cs-137 is the prevalent radionuclide expected to be present. The licensee confirmed this by randomly selecting 46 samples from the Trailer City surveys, 20 of the samples originated from restored areas (backfilled areas) and analyzing them for the full suite of HTD radionuclides. The NRC staff reviewed the contract laboratory analytical reports provided in the submittal and verified that, generally, only naturally occurring radionuclides and Cs-137 were routinely detected at concentrations greater than the MDC and primarily at what could be considered background concentrations. Three samples did have unusual detects of plant radionuclides not normally seen (Be-7 and Cf-245/246); however, in each case the concentration detected was relatively low (less than three times the MDC), and is likely an anomalous result from the laboratory. This is especially the case for the Be-7 detects as that radionuclide has a 53-day half-life and normally originates from cosmic interactions in the atmosphere. It was also noted that in each instance where an unusual detection occurred, no other plant derived radionuclides (except for Cs-137) were identified.
As such, when establishing the DQOs for the OOL09-01-FSR surveys, the licensee only considered Cs-137 concentrations. The survey design was developed by the licensee by using Type 1 and Type 2 errors of 0.05 and the lower bound of the grey region (LBGR) was set in order to achieve a relative shift of two. This resulted in 15 samples being required which is consistent with Table 5.5 of MARSSIM. The maximum Cs-137 result was 0.096 pCi/g and the mean was 0.028 pCi/g. No sample had Cs-137 detected at concentrations exceeding the MDC.
The dose contribution from the average level of Cs-137 was determined to be approximately 0.089 mrem/y. Because no sample result exceeded the DCGL, the licensee concluded the Sign Test passed based on inspection.
Similar to the survey for survey unit OOL09-01, the licensee disregarded 14 of the ROCs from analysis by preliminarily assigning a dose of 2.15 mrem/y based on analytical results from a Liquid Radioactive Waste Building sample that exceeded three times the DCGL for Cs-137.
The combined dose from the Cs-137 concentrations and the disregarded radionuclides was estimated at 2.24 mrem/y which is significantly less than the 25 mrem/y release criteria.
However, this approach left six ETD radionuclides unaddressed which were not considered in the dose determination (Co-60, Eu-152, Eu-154, H-3, Nb-94, and Np-237) and the NRC staff also noted that the dose estimate did not account for contaminated groundwater.
In response to RAI (ADAMS Accession No. ML21063A474) Table 5, the licensee provided all analytical results for the ETD ROCs in the samples utilized for statistical evaluations for this particular survey. Taking into consideration all the ETD ROC data, and disregarding negative average data for individual ROCs, the dose estimate changed from 0.089 mrem/y to 0.25 mrem/y. In addition, Attachment 1 to the response to RAIs included a revised consideration of the HTD ROCs from across the site. The licensee, in Table 2 of the Attachment, states that the dose contribution from average HTD ROCs in Class 1 survey units is 0.187 mrem/y on average. However, in Table 8 of the same Attachment, the licensee acknowledges that a bounding dose estimate of 2.9 mrem/y is possible. The NRC staff consider it appropriate to conservatively bound the hypothetical dose from residual radioactivity as totaling 4.15 mrem/y (2.9 mrem/y from HTD ROCs, 0.25 from ETD ROCs, and 1 mrem/y from residual radioactivity in groundwater [see explanation in survey discussion for survey unit OOL09-01]).
The NRC staff also considered that the licensee did not take representative samples from the entire volume of backfilled material; instead, this material was screened through the GARDIAN system. However, the licensee had previously discussed the hypothetical dose from the fill materials as the GARDIAN system data showed relatively minor fluctuations in Cs-137 and Co-60 in the data. In response to RAI-4 (ADAMS Accession No. ML21165A092), the licensee summarized the GARDIAN system data for materials that were processed. The NRC staff estimated that the hypothetical dose from all pathways from backfill material would likely be bounded by an estimate of 5.96 mrem/y. The NRC staff further note that this is a relatively minor increase from the estimate of 4.15 mrem/y which was based on sampling data in the survey unit and, because the backfill materials were likely well mixed due to excavations and relocations of materials, disregarded the fill material as possibly being of slightly higher impact, but ultimately of minor consequence, to determining hypothetical dose.
The licensee stated that approximately 100% of the survey unit was scanned, which is consistent with MARSSIM guidance for Class 1 survey units, and no exceedances of investigation levels were noted either from sampling or scanning. The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. The split samples were also analyzed for the HTD ROCs with no notable findings. This frequency of quality assurance is consistent with MARSSIM, Section 4.3.2, and the LTP.
The NRC staff finds that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-02 (Settling Basins)
The survey unit designated as OOL09-02 was classified by the licensee as a MARSSIM Class 1 unit and is described as an approximately 1,995 m2 area. The licensee describes the survey unit as being bounded by OOL09-03 and OOL09-04 on the North, OOL09-09 on the East, OOL09-09 on the South, and OOL09-01 on the West. It contained a portion of the Retention Ponds, Trailer City, SMF 1 Footprint, and the SMF haul road. The licensee further describes this as an excavation to remove part of the Unit 1, and 2 Effluent Control Project consisting of 4 Fiberglass Reinforced Pipe Low Volume Waste, 6 Fiberglass Reinforced Pipe Metal Cleaning Waste Ammoniated lines, the abandoned valve box and a major portion of the retention ponds.
Once the FSS activities for the excavation were completed, the area was immediately backfilled with reclaimed soil from various locations on-site that had passed through the GARDIAN system. After remediation and backfilling of the area was completed, a second survey of the surface of this area was performed with the survey unit redesignated as OOL09-02-FSR. As such, the FSS of this survey unit can be best described as being two FSSs, one of the excavation footprints and another of the remediated area after backfilling. The NRC staff found it appropriate to assess each survey individually although they do cover the same planar footprint of the site.
The licensee determined by using the DQO process that Cs-137 is the only plant derived ROC that could potentially be present at significant levels. The licensee determined the required number of soil samples using a Type 1 and Type 2 error of 0.05 and a relative shift of two. The required number of samples was 15, and the licensee collected 21 randomly selected soil samples. The required number of samples is consistent with Table 5.5 of MARSSIM and the licensee desired six additional samples for power in the statistical tests.
The licensee deselected 14 of the HTD ROCs listed in Table 6-4 of the LTP with only seven remaining to be quantified through sampling/analysis. This approach assigned a hypothetical dose of 2.15 mrem/y to these deselected radionuclides based on sample results from the Reactor Drain Tank (RDT) Vault in the Liquid Radiactive Waste Building which had Cs-137 concentrations at approximately three times the DCGL. However, the licensee only reported Cs-137 results in this survey leaving the remaining six ETD ROCs unaccounted for in the survey that was performed. In addition, while the dose estimated from the 14 deselected HTD ROCs was initially estimated at 2.15 mrem/y; staff note that the licensee has since revised its dose estimate for the HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y. The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any survey unit as being 2.9 mrem/y. The NRC staff find it reasonably conservative to assume 2.9 mrem/y from the deselected HTD ROCs applies to the survey unit.
Also, the licensee is not consistent with the LTP in its exclusion of the six ETD ROCs from consideration in hypothetical dose from residual radioactivity. The licensee states that the six ETD ROCs being excluded were never seen above the detection limit, had negligible impact, and so were not reported. However, per the LTP, these should have been included in the deselected ROCs hypothetical dose consideration. Even so, NRC staff agree with the licensee that the impact would be very minor and NRC staff consider a 1 mrem/y dose contribution from these unreported ROCs to be a reasonably conservative bounding assumption such that the deselected ROCs and unreported ROCs hypothetically contribute 3.9 mrem/y dose when combined.
Of the systematic samples collected in this survey, the licensee reported that the maximum Cs-137 concentration from the analytical results is approximately 0.064 pCi/g and the mean is 0.018 pCi/g. None of the Cs-137 results exceeded the MDC. Based on the reported data, the licensee initially stated the hypothetical dose was 2.21 mrem/y (2.15 mrem/y from deselected radionuclides plus 0.06 mrem/y from the average Cs-137 value). However, as previously mentioned, the licensee has revised the dose contribution from deselected HTD ROCs to be 0.187 mrem/y (bounded at 2.9 mrem/y) and the hypothetical dose contribution from unreported ETD ROCs was bounded at 1 mrem/y. Also, ingestion of residual radioactivity in groundwater is anticipated to contribute at most 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01); therefore, the NRC staff believe a reasonably conservative bounding estimate for the hypothetical dose due to residual radioactivity is 5.0 mrem/y in this survey unit. Still significantly below the 25 mrem/y unrestricted release criteria.
In addition to gamma measurements and systematic sampling, the licensee performed analyses for HTD radionuclides on three randomly selected split samples which included alpha spectroscopy, gas proportional counting, or liquid scintillation depending on the radionuclide of interest. This frequency of HTD analyses is consistent with guidance from MARSSIM Section 4.3.2. The split samples had no notable findings and the duplicate evaluations had adequate agreement.
The licensees survey results indicated that Cs-137 was not identified above the detection limit in any of the soil samples collected for non-parametric statistical testing. Because no sample exceeded the DCGL, the statistical test (i.e., Sign Test) was not required. As such, the licensee acknowledged that the Sign Test was performed (by inspection) on the data and compared to the original assumptions of the DQOs, and that performing the test is unnecessary as it is passed by inspection. Scanning of approximately 100% of the survey unit area was performed consistent with the LTP and MARSSIM and no investigation levels were exceeded.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-02-FSR (Settling Basins after Final Site Restoration)
As previously noted, after completing remediation of the settling basins by excavation, the licensee subsequently backfilled the excavation utilizing soil from on-site that had been screened through the GARDIAN system which is a bulk material measurement system used to screen trucks containing soil. The footprint of the survey of OOL09-02-FSR remained essentially identical to that of OOL09-02. The survey that is reported for OOL09-02-FSR is of the surface of the backfilled material which originated on-site. The NRC staff note that an additional layer of backfill was subsequently placed on the filled area after this survey was complete using material that originated off site.
The licensee performed DQOs for the restored areas in the Trailer City and noted that Cs-137 is the prevalent radionuclide expected to be present. The licensee confirmed this by randomly selecting 46 samples from the Trailer City surveys, 20 samples originated from restored areas (backfilled areas) and analyzing them for the full suite of HTD radionuclides as previously discussed in the evaluation of survey unit OOL09-01-FSR. For this reason, when establishing the DQOs for the OOL09-02-FSR surveys, the licensee only considered Cs-137 concentrations.
Like other surveys, the survey design was developed using Type 1 and Type 2 errors of 0.05 and the LBGR was set to achieve a relative shift of two. This resulted in 15 samples being required which is consistent with Table 5.5 of MARSSIM. The maximum Cs-137 result was 0.054 pCi/g and the mean was 0.016 pCi/g. Only one sample had Cs-137 detected at concentrations slightly exceeding the MDC. The hypothetical dose contribution from the average level of Cs-137 was determined to be approximately 0.051 mrem/y. Because no sample result exceeded the DCGL, the licensee concluded the Sign Test passed based on inspection.
Like the survey for survey unit OOL09-02, the licensee disregarded 14 of the plant derived HTD ROCs from analysis by preliminarily assigning a dose of 2.15 mrem/y. However, the licensee has since revised its dose estimate for deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y.
The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical dose impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and, as such, a conservative bounding estimate of 1 mrem/y should be assigned to these ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01); therefore, a reasonably conservative bounding estimate for the hypothetical dose due to residual radioactivity in this survey unit is 5.0 mrem/y (Cs-137 contributed 0.051 mrem/y on average) which remains significantly less than the 25 mrem/y unrestricted release criteria.
The NRC staff also considered that the licensee did not take representative samples from the entire volume of backfilled material; instead, this material was screened through the GARDIAN system. However, the licensee had previously discussed the hypothetical dose from the fill materials as the GARDIAN system data showed relatively minor fluctuations in Cs-137 and Co-60 in the data. In response to RAI-4 (ADAMS Accession No. ML21165A092), the licensee summarized the GARDIAN system data for materials that were processed. The NRC staff estimated that the hypothetical dose from all pathways from backfill material would likely be bounded by an estimate of 5.96 mrem/y. The NRC staff further note that this is a relatively minor increase from the estimate of 5 mrem/y which was based on sampling data in the survey unit and, because the backfill materials were likely well mixed due to excavations and relocations of materials, disregarded the fill material as possibly being of slightly higher impact, but ultimately of minor consequence, to determining hypothetical dose.
The licensee also stated that approximately 100% of the survey unit was scanned which is consistent with MARSSIM guidance for Class 1 survey units. No exceedances of investigation levels were noted from either sampling or scanning. The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. The split samples were also analyzed for HTD ROCs. This frequency of quality assurance is consistent with MARSSIM Section 4.3.2 and the LTP.
The NRC staff finds that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-03 (SMF West)
The survey unit designated as OOL09-03 was classified by the licensee as a MARSSIM Class 1 survey unit and is described as an approximately 1,839 m2 area. The licensee describes the survey unit as being bounded by OOL09-05 on the North, OOL09-04 on the East, OOL09-02 on the South, and OOL09-01 and OOL09-07 on the West. The licensee describes this as an excavation to remove part of the Unit 1, and 2 Effluent Control Project consisting of the retention ponds, the associated discharge piping, and a concrete pad. Once the FSS activities for the excavation were completed, the area was immediately backfilled with reclaimed soil from various locations on-site that had passed through the GARDIAN system. After remediation and backfilling of the area was completed, a second survey of the surface of this area was performed with the survey unit redesignated as OOL09-03-FSR. The NRC staff found it appropriate to assess each survey individually although they do cover the same planar footprint of the site and the survey unit will pass if both surveys demonstrate meeting the release criteria.
The licensee used its DQO process to determine that Cs-137 is the only ROC that could potentially be present at significant levels. The licensee determined the required number of soil samples using a Type 1 and Type 2 error of 0.05 and a relative shift of 2. The required number of samples was 15, and the licensee collected 21 randomly selected soil samples. The required number of samples is consistent with Table 5.5 of MARSSIM and the licensee desired six additional samples for power in the statistical tests.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven ETD ROCs remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y. The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical dose impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and, as such, a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the systematic samples collected in this survey, the licensee reported that the maximum Cs-137 concentration from the analytical results is approximately 0.078 pCi/g and the mean is 0.016 pCi/g. None of the Cs-137 results exceeded the MDC. Based on the reported data, the licensee initially stated the hypothetical dose was 2.21 mrem/y (2.15 mrem/y from deselected radionuclides plus 0.06 mrem/y from the average Cs-137 value). The NRC staff verified the licensees calculation but, when considering the revisions to the deselected ROC estimate, unreported ROC contribution, and residual radioactivity in groundwater, staff determined a reasonably conservative bounding estimate for the hypothetical dose due to residual radioactivity in this survey unit is 5.0 mrem/y (2.9 mrem/y from deselected ROCs in soil, 1 mrem/y from unreported ROCs in soil, 1 mrem/y from ingestion of residual radioactivity in groundwater, and 0.06 mrem/y from Cs-137 in soil) which remains significantly less than the 25 mrem/y unrestricted release criteria.
The licensees LTP requires 100% of Class 1 areas to receive gamma walkover scan coverage during FSS and the licensee states it met the expectation of 100% scanning of the survey unit.
This complies with the LTP and MARSSIM guidance. No exceedance of investigation levels was noted.
In addition to gamma measurements and systematic sampling, the licensee performed analyses for HTD radionuclides on three randomly selected split samples which included alpha spectroscopy, gas proportional counting, or liquid scintillation depending on the radionuclide.
This frequency of HTD analyses is consistent with guidance from MARSSIM Section 4.3.2.
These samples were found to pass the licensees criteria for quality measurements.
The licensees survey results indicated that Cs-137 was not identified above the detection limit in any of the soil samples collected for non-parametric statistical testing. Because no sample exceeded the DCGL, the statistical test (i.e., Sign Test) was not required. As such, the licensee acknowledged that the Sign Test was performed (by inspection) on the data and compared to the original assumptions of the DQOs, and that performing the test is unnecessary as it is passed by inspection.
The NRC staff find that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-03-FSR (SMF West after Final Site Restoration)
As previously noted, after completing remediation of the SMF West area by excavation, the licensee subsequently backfilled the excavation utilizing soil from on-site that had been screened through the GARDIAN system, which is a bulk material measurement system used to screen trucks containing soil. The footprint of the survey of OOL09-03-FSR remained essentially identical to that of OOL09-03. The survey that is reported for OOL09-03-FSR is of the surface of the backfilled material which originated on-site. The NRC staff note that an additional layer of backfill was subsequently placed on the filled area after this survey was complete using material that originated off site.
The licensee performed DQOs for the restored areas in the Trailer City and noted that Cs-137 is the prevalent radionuclide expected to be present. As such, when establishing the DQOs for the OOL09-03-FSR surveys, the licensee only considered Cs-137 concentrations. Like other surveys, the survey design was developed using Type 1 and Type 2 errors of 0.05 and the LBGR was set to achieve a relative shift of two. This resulted in 15 samples being required which is consistent with Table 5.5 of MARSSIM.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP leaving only seven remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides based on sample results from the RDT Vault in the Liquid Radioactive Waste Building which had Cs-137 concentrations at approximately three times the DCGL. However, NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y. The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical dose impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and, as such, a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the non-parametric samples collected, the maximum Cs-137 result was 0.050 pCi/g and the mean was 0.012 pCi/g. Only one sample had Cs-137 detected at concentrations slightly exceeding the MDC. The dose contribution from the average level of Cs-137 was determined to be approximately 0.04 mrem/y. The total estimated hypothetical dose initially estimated by the licensee was 2.19 mrem/y; however, after revisions of deselected HTD ROC dose estimates, bounding assumptions for unreported ROCs, and consideration of the groundwater pathway, the NRC staff derived a bounding estimate of 4.9 mrem/y. Still far beneath the 25 mrem/y unrestricted release criteria. When statistically evaluating the survey data, the licensee noted that, because no sample exceeded the DCGL, the survey unit passed the Sign Test by inspection.
The NRC staff also considered that the licensee did not take representative samples from the entire volume of backfilled material; instead, this material was screened through the GARDIAN system. However, the licensee had previously discussed the hypothetical dose from the fill materials as the GARDIAN system data showed relatively minor fluctuations in Cs-137 and Co-60 in the data. In response to RAI-4 (ADAMS Accession No. ML21165A092), the licensee summarized the GARDIAN system data for materials that were processed. The NRC staff estimated that the hypothetical dose from all pathways from backfill material would likely be bounded by an estimate of 5.96 mrem/y. The NRC staff further note that this is a relatively minor increase from the estimate of 4.9 mrem/y which was based on sampling data in the survey unit and, because the backfill materials were likely well mixed due to excavations and relocations of materials, disregarded the fill material as being of slightly higher possible impact, but ultimately of minor consequence, for determining hypothetical dose.
The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2. Also, the licensee stated that approximately 100% of the survey unit was scanned which is consistent with MARSSIM guidance for Class 1 survey units. No exceedances of investigation levels were noted either from either sampling or scanning.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-04 (SMF East)
The survey unit designated as OOL09-04 was classified by the licensee as a MARSSIM Class 1 unit and is described as an approximately 1,471 m2 area. The licensee describes the survey unit as being bounded by OOL09-05 on the North, OOL09-04 on the East, OOL09-02 on the South and OOL09-01 and OOL09-07 on the West. It contained a portion of the Retention Ponds, Trailer City, SMF Footprints and the SMF haul road. The survey unit was an excavation to remove the Unit 1 and Unit 2 Effluent Control Project that existed in the current survey units.
This consisted of a portion of the retention ponds, the associated discharge piping and a concrete pad. The discharge lines ran East to West underground and discharged into the discharge canal. Once the decommissioning and FSS activities were completed, the area was immediately backfilled with remediated soil from various locations on-site that had passed through the GARDIAN system. After remediation of the area was completed, a second survey of the surface of this area was performed with the survey unit redesignated as OOL09-04-FSR.
The FSS of this survey unit can be best described as being two FSSs, one of the excavation footprints and another of the remediated area after backfilling. The NRC staff found it appropriate to evaluate each survey separately and the survey unit will pass if both surveys meet the release criteria.
The licensee used its DQO process to determine that Cs-137 was the only ROC that could potentially be present at significant levels. The licensee determined the required number of soil samples using a Type 1 and Type 2 error of 0.05 and a relative shift of two. The required number of samples was 15, consistent with Table 5.5 of MARSSIM, and the licensee collected 21 randomly selected soil samples.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y.
The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the potential impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and, as such, a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the systematic samples collected in this survey, the licensee reported that the maximum Cs-137 analytical result is approximately 0.126 pCi/g with the average being 0.0319 pCi/g. The hypothetical dose based on the mean Cs-137 value is 0.10 mrem/y with the survey unit hypothetical dose being initially reported as 2.26 mrem/y. When the NRC staff consider the conservative bounding estimates for deselected HTD ROCs, non-reported ETD ROCs, and residual radioactivity in groundwater, the NRC staff estimate a hypothetical dose of 5.0 mrem/y.
Still far below the 25 mrem/y unrestricted use criterion.
The licensees survey results indicated that Cs-137 was not identified above the detection limit in any of the soil samples collected for non-parametric statistical testing. Because no sample exceeded the DCGL, the statistical test (i.e., Sign Test) was not required. As such, the licensee acknowledged that the Sign Test was performed (by inspection) on the data and compared to the original assumptions of the DQOs, and that performing the test is unnecessary as it is passed by inspection.
The licensee evaluated three split sample analyses and three recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2. Also, the licensee stated that approximately 100% of the survey unit was scanned which is consistent with MARSSIM guidance for Class 1 survey units. No exceedances of investigation levels were noted from either sampling or scanning.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-04-FSR (SMF East after Final Site Restoration)
As previously noted, after completing remediation of the SMF East area by excavation, the licensee subsequently backfilled the excavation utilizing soil from on-site that had been screened through the GARDIAN system which is a bulk material measurement system used to screen trucks containing soil. The footprint of the survey of OOL09-04-FSR remained essentially identical to that of OOL09-04. The survey that is reported for OOL09-04-FSR is of the surface of the backfilled material which originated on-site. The NRC staff note that an additional layer of backfill was subsequently placed on the filled area after this survey was complete using material that originated off site.
The licensee DQOs for the restored areas in the Trailer City noted that Cs-137 is the prevalent radionuclide expected to be present. As such, when establishing the DQOs for the OOL09-04-FSR surveys, the licensee only considered Cs-137 concentrations. Like other surveys, the survey design was developed using Type 1 and Type 2 errors of 0.05 and the LBGR was set to achieve a relative shift of two. This resulted in 15 samples being required which is consistent with Table 5.5 of MARSSIM.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven remaining to be quantified through sampling/analysis. The licensee initially assigned a hypothetical dose of 2.15 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y. The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the potential impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate.
This is contrary to the LTP, however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and, as such, a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the non-parametric samples collected, the maximum Cs-137 result was 0.142 pCi/g and the mean was 0.024 pCi/g. Only one sample had Cs-137 detected at concentrations barely exceeding the MDC. The dose contribution from the average level of Cs-137 was determined to be approximately 0.08 mrem/y. Because no sample result exceeded the DCGL, the licensee concluded the Sign Test passed based on inspection. The total estimated hypothetical dose initially estimated by the licensee was 2.23 mrem/y; however, after revisions of deselected HTD ROC dose estimates, bounding assumptions for unreported ETD ROC dose estimates, and consideration of residual radioactivity in groundwater, the NRC staff derived a bounding estimate of 5.0 mrem/y. Still far beneath the 25 mrem/y unrestricted release criteria.
The NRC staff also considered that the licensee did not take representative samples from the entire volume of backfilled material; instead, this material was screened through the GARDIAN system. However, the licensee had previously discussed the hypothetical dose from the fill materials as the GARDIAN system data showed relatively minor fluctuations in Cs-137 and Co-60 in the data. In response to RAI-4 (ADAMS Accession No. ML21165A092), the licensee summarized the GARDIAN system data for materials that were processed. The NRC staff estimated that the hypothetical dose from all pathways from backfill material would likely be bounded by an estimate of 5.96 mrem/y. The NRC staff further note that this is a relatively minor increase from the estimate of 5.0 mrem/y which was based on sampling data in the survey unit and, because the backfill materials were likely well mixed due to excavation and relocation of materials, disregarded the fill material as being of slightly higher possible impact, but ultimately of minor consequence, for determining hypothetical dose.
The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for all ROCs which is consistent with MARSSIM Section 4.3.2. Also, the licensee stated that approximately 100% of the survey unit was scanned which is consistent with MARSSIM guidance for Class 1 survey units. No exceedances of investigation levels were noted either from either sampling or scanning.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-05 (Bull Pen West)
The survey unit designated as OOL09-05 was classified by the licensee as a MARSSIM Class 1 unit and is described as an approximately 1,954 m2 area. The licensee describes the survey unit as bounded by OOL09-10 on the North, OOL09-06 on the East, OOL09-03 and OOL09-04 on the South and OOL09-07 and OOL09-08 on the West. It contained the Humboldt Bay Generating Station (HBGS) project laydown area, Trailer City, reuse soil laydown areas, SMF Footprints and the SMF haul road.
The survey unit was an excavation to remove the SMF tents and the SMF haul road and other associated soils/debris. Once the decommissioning and FSS activities were completed, the area was immediately backfilled with recovered soil from various locations on-site that had passed through the GARDIAN system. After remediation of the area was completed, a second survey of the surface of this area was performed with the survey unit redesignated as OOL09-05-FSR. As such, the FSS of this survey unit can be best described as being two FSSs, one of the excavation footprints and another of the remediated area after backfilling. The NRC staff found it appropriate to evaluate each survey separately and the survey unit will pass if both surveys meet the release criteria.
The licensee used its DQO process to determine that Cs-137 was the only ROC that could potentially be present at significant levels. The licensee determined the required number of soil samples using a Type 1 and Type 2 error of 0.05 and a relative shift of two. The required number of samples was 15, which is consistent with Table 5.5 of MARSSIM, and the licensee collected 21 randomly selected soil samples.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y.
The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the potential impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and, as such, a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the systematic samples collected in this survey, the licensee reported that the maximum Cs-137 analytical result is approximately 0.095 pCi/g with the average being 0.026 pCi/g. The hypothetical dose based on the mean Cs-137 value is 0.08 mrem/y with the survey unit hypothetical dose being initially reported as 2.24 mrem/y. When the NRC staff consider the revised bounding estimates for deselected HTD ROCs, non-reported ETD ROCs, and residual radioactivity in groundwater, the NRC staff estimate a hypothetical dose of 5.0 mrem/y. Still far below the 25 mrem/y unrestricted use criterion.
The licensees survey results indicated that Cs-137 was not identified above the detection limit in any of the soil samples collected for non-parametric statistical testing. Because no sample exceeded the DCGL, the statistical test (i.e., Sign Test) was not required. As such, the licensee acknowledged that the Sign Test was performed (by inspection) on the data and compared to the original assumptions of the DQOs, and that performing the test is unnecessary as it is passed by inspection.
The licensee evaluated three split sample analyses and three recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2. Also, the licensee stated that approximately 100% of the survey unit was scanned which is consistent with MARSSIM guidance for Class 1 survey units. No exceedances of investigation levels were noted either from either sampling or scanning.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-05-FSR (Bull Pen West after Final Site Restoration)
As previously noted, after completing remediation of the Bull Pen West area by excavation, the licensee subsequently backfilled the excavation utilizing soil from on-site that had been screened through the GARDIAN system which is a bulk material measurement system used to screen trucks containing soil. The footprint of the survey of OOL09-05-FSR remained essentially identical to that of OOL09-05. The survey that is reported for OOL09-05-FSR is of the surface of the backfilled material which originated on-site. Staff note that an additional layer of backfill was subsequently placed on the filled area after this survey was complete using material that originated off site.
The licensee performed its DQO process for the restored areas in the Trailer City and noted that Cs-137 is the prevalent radionuclide expected to be present at significant levels. As such, when establishing the DQOs for the OOL09-05-FSR surveys, the licensee only considered Cs-137 concentrations. Like other surveys, the survey design was developed using Type 1 and Type 2 errors of 0.05 and the LBGR was set to achieve a relative shift of two. This resulted in 15 samples being required which is consistent with Table 5.5 of MARSSIM.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y.
The licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical impact of the HTD ROCs in soil is bounded at 2.9 mrem/y.
Of the non-parametric samples collected, the maximum Cs-137 result was 0.100 pCi/g and the mean was 0.031 pCi/g. No sample had Cs-137 detected at concentrations exceeding the MDC.
The dose contribution from the average level of Cs-137 was determined to be approximately 0.10 mrem/y. The total estimated hypothetical dose initially estimated by the licensee was 2.25 mrem/y based solely on the initially reported deselected ROC contributions and Cs-137 data. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Because no sample result exceeded the DCGL, the licensee concluded the Sign Test passed based on inspection.
The licensee initially failed to report or consider data for six ETD ROCs in soil which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, in response to RAI (ADAMS Accession No. ML21063A474) Table 6, the licensee provided all analytical results for the ETD ROCs in the samples utilized for statistical evaluations for this particular survey unit. Taking in consideration all the data, and disregarding negative average data for individual ROCs, the dose estimate changed from 0.04 mrem/y (due to Cs-137 alone) to 0.125 mrem/y from the ETD ROCs. As such, the NRC staff determined a bounding hypothetical dose estimate from deselected HTD ROCs in soil, all ETD ROCs in soil, and ingestion of groundwater should be 4.0 mrem/y. Still far beneath the 25 mrem/y unrestricted release criteria.
The NRC staff also considered that the licensee did not take representative samples from the entire volume of backfilled material; instead, this material was screened through the GARDIAN system. However, the licensee had previously discussed the hypothetical dose from the fill materials as the GARDIAN system data showed relatively minor fluctuations in Cs-137 and Co-60 in the data. In response to RAI-4 (ADAMS Accession No. ML21165A092), the licensee summarized the GARDIAN system data for materials that were processed. The NRC staff estimated that the hypothetical dose from all pathways from backfill material would likely be bounded by an estimate of 5.96 mrem/y. The NRC staff further note that this is a relatively minor increase from the estimate of 4.0 mrem/y which was based on sampling data in the survey unit and, because the backfill materials were likely well mixed due to excavation and relocation of materials, disregarded the fill material as being of slightly higher possible impact, but ultimately of minor consequence, for determining hypothetical dose.
The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2. Also, the licensee stated that approximately 100% of the survey unit was scanned which is consistent with MARSSIM guidance for Class 1 survey units. No exceedances of investigation levels were noted either from either sampling or scanning.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-06 (Bull Pen East)
The survey unit designated as OOL09-06 was classified by the licensee as a MARSSIM Class 1 unit and is described as an approximately 1,946 m2 area. The licensee describes the survey unit as being bounded by OOL09-10 on the North, OOL10-19 on the East, OOL09-04 and OOL09-09 on the South and OOL09-04 and OOL09-05 on the West. It contained the HBGS project laydown area, Trailer City, reuse soil laydown areas, and the SMF haul road. The survey unit was an excavation to remove the SMF haul road and other associated soil/debris.
Once the decommissioning and FSS activities were completed, the area was immediately backfilled with remediated soil from various locations on-site that had passed through the GARDIAN system. After remediation of the area was completed, a second survey of the surface of this area was performed with the survey unit redesignated as OOL09-06-FSR. As such, the FSS of this survey unit can be best described as being two FSSs, one of the excavation footprints and another of the remediated area after backfilling. The NRC staff found it appropriate to evaluate each survey separately and the survey unit will pass if both surveys meet the release criteria.
The licensee used its DQO process to determine that Cs-137 was the only ROC that could potentially be present at significant levels. The licensee determined the required number of soil samples using a Type 1 and Type 2 error of 0.05 and a relative shift of two. The required number of samples was 15, which is consistent with Table 5.5 of MARSSIM, and the licensee collected 21 randomly selected soil samples.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y.
The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the potential impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment but believe a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the systematic samples collected in this survey, the licensee reported that the maximum Cs-137 analytical result is approximately 0.268 pCi/g with the average being 0.0571 pCi/g. The hypothetical dose based on the mean Cs-137 value is 0.18 mrem/y with the survey unit hypothetical dose being initially reported as 2.34 mrem/y. When the NRC staff consider the conservative bounding estimates for deselected HTD ROC, non-reported ETD ROCs, and residual radioactivity in groundwater, staff estimate a hypothetical dose of 5.1 mrem/y. Still far below the 25 mrem/y unrestricted use criterion.
The licensees survey results indicated that Cs-137 was identified slightly above the detection limit in four of the soil samples collected for non-parametric statistical testing. Because no sample exceeded the DCGL, the statistical test (i.e., Sign Test) was not required. As such, the licensee acknowledged that the Sign Test was performed (by inspection) on the data and compared to the original assumptions of the DQOs, and that performing the test is unnecessary as it is passed by inspection.
The licensee evaluated three split sample analyses and three recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-06-FSR (Bull Pen East after Final Site Restoration)
As previously noted, after completing remediation of the Bull Pen East area by excavation, the licensee subsequently backfilled the excavation utilizing soil from on-site that had been screened through the GARDIAN system which is a bulk material measurement system used to screen trucks containing soil. The footprint of the survey of OOL09-06-FSR remained essentially identical to that of OOL09-06. The survey that is reported for OOL09-06-FSR is of the surface of the backfilled material which originated on-site. The NRC staff note that an additional layer of backfill was subsequently placed on the filled area after this survey was complete using material that originated off site.
The licensee performed DQOs for the restored areas in the Trailer City and noted that Cs-137 is the prevalent radionuclide expected to be present. As such, when establishing the DQOs for the OOL09-06-FSR surveys, the licensee only considered Cs-137 concentrations. Like other surveys, the survey design was developed using Type 1 and Type 2 errors of 0.05 and the LBGR was set to achieve a relative shift of two. This resulted in 15 samples being required which is consistent with Table 5.5 of MARSSIM.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y.
The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the potential impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and believe a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected HTD ROCs and non-reported ETD ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the non-parametric samples collected, the maximum Cs-137 result was 0.076 pCi/g and the mean was 0.036 pCi/g. Two samples had Cs-137 detected at concentrations slightly exceeding the MDC. The dose contribution from the average level of Cs-137 was determined to be approximately 0.11 mrem/y. Because no sample result exceeded the DCGL, the licensee concluded the Sign Test passed based on inspection. The total estimated hypothetical dose initially estimated by the licensee was 2.27 mrem/y; however, after revisions of deselected HTD ROC dose estimates, bounding assumptions for unreported ETC ROC dose estimates, and consideration of residual radioactivity in groundwater, the NRC staff derived a bounding estimate of 5.0 mrem/y. Still far beneath the 25 mrem/y unrestricted release criteria.
The NRC staff also considered that the licensee did not take representative samples from the entire volume of backfilled material; instead, this material was screened through the GARDIAN system. The licensee had previously discussed the hypothetical dose from the fill materials as the GARDIAN system data showed relatively minor fluctuations in Cs-137 and Co-60 in the data. In response to RAI-4 (ADAMS Accession No. ML21165A092), the licensee summarized the GARDIAN system data for materials that were processed. The NRC staff estimated that the hypothetical dose from all pathways from backfill material would likely be bounded by an estimate of 5.96 mrem/y. The NRC staff further note that this is a relatively minor increase from the estimate of 5.0 mrem/y which was based on sampling data in the survey unit and, because the backfill materials were likely well mixed due to excavations and relocations of materials, disregarded the fill material as being of slightly higher possible impact, but ultimately of minor consequence, for determining hypothetical dose.
The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2. Also, the licensee stated that approximately 100% of the survey unit was scanned which is consistent with MARSSIM guidance for Class 1 survey units. No exceedances of investigation levels were noted either from either sampling or scanning.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-07 (GWTS North)
The survey unit designated as OOL09-07 was classified by the licensee as a MARSSIM Class 1 unit and is described as an approximately 1,994 m2 area. The licensee describes the survey unit as being bounded by OOL09-08 on the North, OOL09-03 and OOL09-05 on the East, OOL09-01 and OOL09-03 on the South and OOL01-01 and OOL01-02 on the West. It contained HBGS project laydown area, GWTS and the SMF and Discharge Canal haul roads.
The survey unit was an excavation to remove the GWTS area, the haul roads, and any other associated soil/debris. Once the decommissioning and FSS activities were completed, the area was immediately backfilled with remediated soil from various locations on-site that had passed through the GARDIAN system. After remediation of the area was completed, a second survey of the surface of this area was performed with the survey unit redesignated as OOL09-07-FSR.
As such, the FSS of this survey unit can be best described as being two FSSs, one of the excavation footprints and another of the remediated area after backfilling. The NRC staff found it appropriate to evaluate each survey separately and the survey unit will pass if both surveys demonstrate meeting the release criteria.
The licensee used its DQO process to determine that Cs-137 was the only ROC that could potentially be present at significant levels. The licensee determined the required number of soil samples using a Type 1 and Type 2 error of 0.05 and a relative shift of two. The required number of samples was 15, which is consistent with Table 5.5 of MARSSIM, and the licensee collected 21 randomly selected soil samples.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven ROCs remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y.
The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and believe a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected HTD ROCs and non-reported ETD ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the systematic samples collected in this survey, the licensee reported that the maximum Cs-137 analytical result is approximately 0.086 pCi/g with the average being 0.029 pCi/g. The hypothetical dose based on the mean Cs-137 value is 0.09 mrem/y with the survey unit hypothetical dose being initially reported as 2.25 mrem/y. When the NRC staff consider the conservative bounding estimates for deselected HTD ROCs, non-reported ETD ROCs, and residual radioactivity in groundwater, staff estimate a hypothetical dose of 5.0 mrem/y. Still far below the 25 mrem/y unrestricted use criterion.
The licensees survey results indicated that Cs-137 was not identified above the detection limit in any of the soil samples collected for non-parametric statistical testing. Because no sample exceeded the DCGL, the statistical test (i.e., Sign Test) was not required. As such, the licensee acknowledged that the Sign Test was performed (by inspection) on the data and compared to the original assumptions of the DQOs, and that performing the test is unnecessary as it is passed by inspection.
The licensee evaluated three split sample analyses and three recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-07-FSR (GWTS North after Final Site Restoration)
As previously noted, after completing remediation of the GWTS North area by excavation, the licensee subsequently backfilled the excavation utilizing soil from on-site that had been screened through the GARDIAN system which is a bulk material measurement system used to screen trucks containing soil. The footprint of the survey of OOL09-07-FSR remained essentially identical to that of OOL09-07. The survey that is reported for OOL09-07-FSR is of the surface of the backfilled material which originated on-site. The NRC staff note that an additional layer of backfill was subsequently placed on the filled area after this survey was complete using material that originated off site.
The licensee performed DQOs for the restored areas in the Trailer City and noted that Cs-137 is the prevalent radionuclide expected to be present. As such, when establishing the DQOs for the OOL09-03-FSR surveys, the licensee only considered Cs-137 concentrations. Like other surveys, the survey design was developed using Type 1 and Type 2 errors of 0.05 and the LBGR was set to achieve a relative shift of two. This resulted in 15 samples being required which is consistent with Table 5.5 of MARSSIM.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y.
The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP, however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and believe a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the non-parametric samples collected, the maximum Cs-137 result was 0.100 pCi/g and the mean was 0.020 pCi/g. No sample had Cs-137 detected at concentrations exceeding the MDC.
Because no sample result exceeded the DCGL, the licensee concluded the Sign Test passed based on inspection. The dose contribution from the average level of Cs-137 was determined to be approximately 0.06 mrem/y. The total estimated hypothetical dose initially estimated by the licensee was 2.22 mrem/y; however, after bounding revisions of deselected HTD ROC dose estimates, bounding assumptions for unreported ETD ROC dose estimates and, consideration of residual radioactivity in groundwater, the NRC staff derived a bounding estimate of 5.0 mrem/y. Still far beneath the 25 mrem/y unrestricted release criteria.
The NRC staff also considered that the licensee did not take representative samples from the entire volume of backfilled material; instead, this material was screened through the GARDIAN system. However, the licensee had previously discussed the hypothetical dose from the fill materials as the GARDIAN system data showed relatively minor fluctuations in Cs-137 and Co-60 in the data. In response to RAI-4 (ADAMS Accession No. ML21165A092), the licensee summarized the GARDIAN system data for materials that were processed. The NRC staff estimated that the hypothetical dose from all pathways from backfill material would likely be bounded by an estimate of 5.96 mrem/y. The NRC staff further note that this is a relatively minor increase from the estimate of 5.0 mrem/y which was based on sampling data in the survey unit and, because the backfill materials were likely well mixed due to excavations and relocations of materials, disregarded the fill material as being of slightly higher possible impact, but ultimately of minor consequence, for determining hypothetical dose.
The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2. Also, the licensee stated that approximately 100% of the survey unit was scanned which is consistent with MARSSIM guidance for Class 1 survey units. No exceedances of investigation levels were noted from either sampling or scanning.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-08 (GWTS South)
The survey unit designated as OOL09-08 was classified by the licensee as a MARSSIM Class 1 unit and is described as an approximately 1,805 m2 area. The licensee describes the survey unit as being bounded by OOL05-01 and OOL09-10 on the North, OOL09-05 and OOL09-10 on the East, OOL09-07 on the South and OOL01-01 and OOL05-01 on the West. It contained the HBGS project laydown area, GWTS and the SMF and Discharge Canal haul roads. The survey unit was an excavation to remove the GWTS area, the haul roads and any other associated soil/debris. Once the decommissioning and FSS activities were completed, the area was immediately backfilled with remediated soil from various locations on-site that had passed through the GARDIAN system. After remediation of the area was completed, a second survey of the surface of this area was performed with the survey unit redesignated as OOL09-08-FSR.
As such, the FSS of this survey unit can be best described as being two FSSs, one of the excavation footprints and another of the remediated area after backfilling. The NRC staff found it appropriate to evaluate each survey separately and the survey unit will pass if both surveys meet the release criteria.
The licensee used its DQO process to determine that Cs-137 was the only ROC that could potentially be present at significant levels. The licensee determined the required number of soil samples using a Type 1 and Type 2 error of 0.05 and a relative shift of two. The required number of samples was 15 which is consistent with Table 5.5 of MARSSIM.
The licensee deselected 13 of the ROCs listed in Table 6-4 of the LTP with eight remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 0.794 mrem/y to these deselected radionuclides based on sample results from the RDT Vault in the Liquid Radioactive Waste Building which had Cs-137 concentrations at approximately three times the DCGL. However, NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y. The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for seven ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and believe a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the systematic samples collected in this survey, the licensee reported that the maximum Cs-137 analytical result is approximately 0.061 pCi/g with the average being 0.018 pCi/g. The hypothetical dose based on the mean Cs-137 value is 0.06 mrem/y with the survey unit hypothetical dose being initially reported as 0.86 mrem/y. When the NRC staff consider the conservative bounding estimates for deselected and non-reported ROCs and consideration of residual radioactivity in groundwater, staff estimate a bounding hypothetical dose of 5.0 mrem/y.
Still far below the 25 mrem/y unrestricted use criterion.
The licensees survey results indicated that Cs-137 was not identified above the detection limit in any of the soil samples collected for non-parametric statistical testing. Because no sample exceeded the DCGL, the statistical test (i.e., Sign Test) was not required. As such, the licensee acknowledged that the Sign Test was performed (by inspection) on the data and compared to the original assumptions of the DQOs, and that performing the test is unnecessary as it is passed by inspection.
The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-08-FSR (GWTS South after Final Site Restoration)
As previously noted, after completing remediation of the GWTS South area by excavation, the licensee subsequently backfilled the excavation utilizing soil from on-site that had been screened through the GARDIAN system which is a bulk material measurement system used to screen trucks containing soil. The footprint of the survey of OOL09-08-FSR remained essentially identical to that of OOL09-08. The survey that is reported for OOL09-08-FSR is of the surface of the backfilled material which originated on-site. The NRC staff note that an additional layer of backfill was subsequently placed on the filled area after this survey was complete using material that originated off site.
The licensee established DQOs for the restored areas in the Trailer City and noted that Cs-137 is the prevalent radionuclide expected to be present. As such, when establishing the DQOs for the OOL09-08-FSR surveys, the licensee only considered Cs-137 concentrations. Like other surveys, the survey design was developed using Type 1 and Type 2 errors of 0.05 and the LBGR was set to achieve a relative shift of two. This resulted in 15 samples being required which is consistent with Table 5.5 of MARSSIM.
The licensee deselected 13 ROCs listed in Table 6-4 of the LTP with 8 ROCs remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 0.794 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y.
The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for seven ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP, however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and believe a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the non-parametric samples collected, the maximum Cs-137 result was 0.072 pCi/g and the mean was 0.012 pCi/g. No sample had Cs-137 detected at concentrations exceeding the MDC.
The dose contribution from the average level of Cs-137 was determined to be approximately 0.04 mrem/y. Because no sample result exceeded the DCGL, the licensee concluded the Sign Test passed based on inspection. The total estimated hypothetical dose initially reported by the licensee was 0.84 mrem/y; however, after bounding assumptions of deselected and unreported ROC dose estimates and consideration of residual radioactivity in groundwater, the NRC staff derived a bounding estimate of 4.9 mrem/y. Still far beneath the 25 mrem/y unrestricted release criteria.
The NRC staff also considered that the licensee did not take representative samples from the entire volume of backfilled material; instead, this material was screened through the GARDIAN system. However, the licensee had previously discussed the hypothetical dose from the fill materials as the GARDIAN system data showed relatively minor fluctuations in Cs-137 and Co-60 in the data. In response to RAI-4 (ADAMS Accession No. ML21165A092), the licensee summarized the GARDIAN system data for materials that were processed. The NRC staff estimated that the hypothetical dose from all pathways from backfill material would likely be bounded by an estimate of 5.96 mrem/y. The NRC staff further note that this is a relatively minor increase from the estimate of 4.9 mrem/y which was based on sampling data in the survey unit and, because the backfill materials were likely well mixed due to excavations and relocations of materials, disregarded the fill material as being of slightly higher possible impact, but ultimately of minor consequence, for determining hypothetical dose.
The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2. Also, the licensee stated that approximately 100% of the survey unit was scanned which is consistent with MARSSIM guidance for Class 1 survey units. No exceedances of investigation levels were noted either from either sampling or scanning.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-09 (Asbestos Area)
The survey unit designated as OOL09-09 was classified by the licensee as a MARSSIM Class 2 unit and is described as an approximately 2,558 m2 area. The licensee describes the survey unit as being bounded by OOL09-01, OOL09-02, OOL09-04 and OOL09-06 on the North, HBGS-East, and OOL10-19 on the East, OOL09-01 and OOL10-19 on the South and OOL09-01, OOL09-02 and OOL09-04 on the West. It contained a small footprint under the newly constructed HBGS, part of the railroad, abandoned gas line, the 4 FRP-LVW and 6 RFP-MCW Ammoniated lines, the abandoned valve box, old asbestos debris field, and decommissioning reuse soil stockpiles. The survey unit was an excavation to remove the abandoned lines and valve box, remediate the environmental hazards in the asbestos debris area and the portion of the railroad left in the area, and any other associated soil/debris. Once the decommissioning and FSS activities were completed, the area was immediately backfilled with remediated soil from various locations on-site that had passed through the GARDIAN system. After remediation of the area was completed, a second survey of the surface of this area was performed with the survey unit redesignated as OOL09-09-FSR. As such, the FSS of this survey unit can be best described as being two FSSs, one of the excavation footprints and another of the remediated area after backfilling. The NRC staff found it appropriate to evaluate each survey separately and the survey unit will pass if both surveys meet the release criteria.
The licensee used its DQO process to determine that Cs-137 was the only ROC that could potentially be present at significant levels. The licensee determined the required number of soil samples using a Type 1 and Type 2 error of 0.05 and a relative shift of two. The required number of samples was 15 which is consistent with Table 5.5 of MARSSIM.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 3, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 2 areas to be 0.12 mrem/y.
The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, the NRC staff agree, after review of available data, that these ETD ROCs would likely have minor impact on the hypothetical dose assessment and believe a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, a bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the systematic samples collected in this survey, the licensee reported that the maximum Cs-137 analytical result is approximately 0.295 pCi/g with the average being 0.051 pCi/g. The hypothetical dose based on the mean Cs-137 value is 0.16 mrem/y with the survey unit hypothetical dose being initially reported as 2.32 mrem/y. When the NRC staff consider the conservative bounding estimates for deselected and non-reported ROCs and residual radioactivity in groundwater, staff estimate a hypothetical dose of 5.1 mrem/y. Still far below the 25 mrem/y unrestricted use criterion.
The licensees survey results indicated that Cs-137 was identified slightly above the detection limit in two of the soil samples collected for non-parametric statistical testing. Because no sample exceeded the DCGL, the statistical test (i.e., Sign Test) was not required. As such, the licensee acknowledged that the Sign Test was performed (by inspection) on the data and compared to the original assumptions of the DQOs, and that performing the test is unnecessary as it is passed by inspection.
The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2. Also, the licensee stated that approximately 50% of the survey unit was scanned which is consistent with MARSSIM guidance for Class 2 survey units. No exceedances of investigation levels were noted from either sampling or scanning.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-09-FSR (Asbestos Area after Final Site Restoration)
As previously noted, after completing remediation of the Asbestos Area by excavation, the licensee subsequently backfilled the excavation utilizing soil from on-site that had been screened through the GARDIAN system which is a bulk material measurement system used to screen trucks containing soil. The licensee describes the survey unit as being bounded by OOL09-01-FSR, OOL09-02-FSR, OOL09-04-FSR and OOL09-06-FSR on the North, OOL09-09, HBGS-East, OOL09-10-FSR and OOL10-19-FSR on the East, OOL09-01-FSR and OOL10-19 on the South and OOL09-01-FSR, OOL09-02-FSR and OOL09-04-FSR on the West.
NRC staff noted that the footprint of the survey of OOL09-09-FSR was slightly modified from the footprint of OOL09-09 (1,990 m2 vs 2,558 m2) and that the backfill actually extended slightly outside of the excavation area (the OOL09-09 survey unit boundaries) as needed to contour portion of a catch basin in the previously surveyed and neighboring Duck Pond survey unit (a Class 3 survey unit). The licensee describes the OOL09-09-FSR survey unit as a Class 1 open land area of 1,990 m2 which includes materials used as backfill in the OOL09-09 survey unit and nearby outside of those boundaries (see ADAMS Accession No. ML21217A070).
Regardless, the area being surveyed is consistent with MARSSIM survey unit area limits for Class 1 survey units. The survey that is reported for OOL09-09-FSR is of the surface of the backfilled material which originated on-site. The NRC staff note that an additional layer of backfill was subsequently placed on the filled area after this survey was complete using material that originated off site.
The licensee established DQOs for the restored areas in the Trailer City and noted that Cs-137 is the prevalent radionuclide expected to be present. As such, when establishing the DQOs for the OOL09-09-FSR surveys, the licensee only considered Cs-137 concentrations. Like other surveys, the survey design was developed using Type 1 and Type 2 errors of 0.05 and the LBGR was set to achieve a relative shift of two. This resulted in 15 samples being required which is consistent with Table 5.5 of MARSSIM.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven ROCs remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y.
The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP, however, NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and believe a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the non-parametric samples collected, the maximum Cs-137 result was 0.082 pCi/g and the mean was 0.021 pCi/g. Only one sample had Cs-137 detected at concentrations slightly exceeding the MDC. Because no sample result exceeded the DCGL, the licensee concluded the Sign Test passed based on inspection. The dose contribution from the average level of Cs-137 was determined to be approximately 0.07 mrem/y. The total estimated hypothetical dose initially estimated by the licensee was 2.22 mrem/y; however, after bounding revisions of deselected and unreported ROC dose estimates and consideration of residual radioactivity in groundwater, the NRC staff derived a bounding estimate of 5.0 mrem/y. Still far beneath the 25 mrem/y unrestricted release criteria.
The NRC staff also considered that the licensee did not take representative samples from the entire volume of backfilled material; instead, this material was screened through the GARDIAN system. However, the licensee had previously discussed the hypothetical dose from the fill materials as the GARDIAN system data showed relatively minor fluctuations in Cs-137 and Co-60 in the data. In response to RAI-4 (ADAMS Accession No. ML21165A092), the licensee summarized the GARDIAN system data for materials that were processed. The NRC staff estimated that the hypothetical dose from all pathways from backfill material would likely be bounded by an estimate of 5.96 mrem/y. The NRC staff further note that this is a relatively minor increase from the estimate of 5.0 mrem/y which was based on sampling data in the survey unit and, because the backfill materials were likely well mixed due to excavations and relocations of materials, disregarded the fill material as being of slightly higher possible impact, but ultimately of minor consequence, for determining hypothetical dose.
The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2. Also, the licensee stated that approximately 100% of the survey unit was scanned which meets MARSSIM guidance for Class 1 survey units. No exceedances of investigation levels were noted from either sampling or scanning.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-10 (Trail Buffer Zone)
The survey unit designated as OOL09-10 was classified by the licensee as a MARSSIM Class 2 unit and is described as an approximately 2,216 m2 area. The licensee describes the survey unit as being bounded by OOL10-13 on the North, OOL10-13 and OOL10-19 on the East, OOL05-01, OOL09-05, OOL09-06 and OOL09-08 on the South and OOL05-01 and OOL09-08 on the West. It contained the pedestrian coastal trail, some GWTS discharge piping that led to the bay and decommissioning reuse soils stockpiles. The survey unit is an excavation to remove the abandoned drains lines leading to the bay, and any other associated soil/debris as directed by Pacific Gas and Electric. Once the decommissioning and FSS activities were completed, the area was immediately backfilled with remediated soil from various locations on-site that had passed through the GARDIAN system. After remediation of the area was completed, a second survey of the surface of this area was performed with the survey unit redesignated as OOL09-10-FSR. As such, the FSS of this survey unit can be best described as being two FSSs, one of the excavation footprints and another of the remediated area after backfilling. The NRC staff found it appropriate to evaluate each survey separately and the survey unit will pass if both surveys demonstrate meeting the release criteria.
The licensee used its DQO process to determine that Cs-137 was the only ROC that could potentially be present at significant levels. The licensee determined the required number of soil samples using a Type 1 and Type 2 error of 0.05 and a relative shift of two. The required number of samples was 15 which the licensee collected, and which is consistent with Table 5.5 of MARSSIM.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven ROCs remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, the NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 3, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 2 areas to be 0.12 mrem/y.
NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the potential dose estimate. This is contrary to the LTP; however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and believe a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the systematic samples collected in this survey, the licensee reported that the maximum Cs-137 analytical result is approximately 0.101 pCi/g with the average being 0.0313 pCi/g. The hypothetical dose based on the mean Cs-137 value is 0.10 mrem/y with the survey unit hypothetical dose being initially reported as 2.25 mrem/y. When the NRC staff consider the conservative bounding estimates of deselected and non-reported ROCs and consider residual radioactivity in groundwater, staff estimate a hypothetical dose of 5.0 mrem/y. Still far below the 25 mrem/y unrestricted use criterion.
The licensees survey results indicated that Cs-137 was only identified above the detection limit in one soil sample collected for non-parametric statistical testing. Because no sample exceeded the DCGL, the statistical test (i.e., Sign Test) was not required. As such, the licensee acknowledged that the Sign Test was performed (by inspection) on the data and compared to the original assumptions of the DQOs, and that performing the test is unnecessary as it is passed by inspection.
The licensee stated that a scanning survey was performed over approximately 50% of the survey unit which meets the MARSSIM guidance for Class 2 survey units. The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
OOL09-10-FSR (Trail Buffer Zone after Final Site Restoration)
As previously noted, after completing remediation of the Trail Buffer Zone by excavation, the licensee subsequently backfilled the excavation utilizing soil from on-site that had been screened through the GARDIAN system which is a bulk material measurement system used to screen trucks containing soil. NRC staff noted that the surveyed backfill actually extended outside of the excavation area (the OOL09-10 survey unit boundaries) as needed to contour portion of a catch basin in the previously surveyed and neighboring Duck Pond survey unit (a Class 3 survey unit). The licensee describes the OOL09-10-FSR survey unit as a Class 1 open land area of 1,771 m2 which includes materials used as backfill in the OOL09-10 survey unit and nearby outside of those boundaries (see ADAMS Accession No. ML21217A070).
Regardless, the area being surveyed is consistent with MARSSIM survey unit area limits for Class 1 survey units. The survey unit is bounded by OOL10-13 on the North, OOL10-13 and OOL10-19 on the East, OOL05-01, OOL09-05-FSR, OOL09-06-FSR and OOL09-08-FSR on the South and OOL05-01 and OOL09-08-FSR on the West. The survey that is reported for OOL09-10-FSR is of the surface of the backfilled material which originated on-site. The NRC staff note that an additional layer of backfill was subsequently placed on the filled area after this survey using material that originated off site. Staff further note that the survey unit boundaries vary slightly from that of OOL09-10 and believe that fill was placed outside of the initial survey unit boundaries and that OOL09-10-FSR boundaries were adjusted to encompass additional filled areas.
The licensee established DQOs for the restored areas in the Trailer City and noted that Cs-137 is the prevalent radionuclide expected to be present. As such, when establishing the DQOs for the OOL09-10-FSR surveys, the licensee only considered Cs-137 concentrations. Like other surveys, the survey design was developed using Type 1 and Type 2 errors of 0.05 and the LBGR was set to achieve a relative shift of two. This resulted in 15 samples being required which is consistent with Table 5.5 of MARSSIM.
The licensee deselected the HTD ROCs listed in Table 6-4 of the LTP with only seven remaining to be quantified through sampling/analysis. The licensee initially assigned a dose of 2.15 mrem/y to these deselected radionuclides; however, NRC staff note that the licensee has since revised its dose estimate from deselected HTD ROCs (see ADAMS Accession No. ML21063A474, Attachment 1). In the Attachment, Table 2, the licensee estimates the average hypothetical dose contribution from HTD ROCs in Class 1 areas to be 0.187 mrem/y.
The NRC staff note that the licensee states that C-14 is not a radionuclide expected to be present in the survey unit because it is produced from neutron activation of concrete and, as such, is only considered to be potentially present in the Caisson FSS Unit NOL01-09. Also, in Table 8 of the same Attachment, the licensee bounds the hypothetical dose from all HTD ROCs in any site survey unit as being 2.9 mrem/y. The NRC staff consider it reasonably conservative to assume the hypothetical impact of the HTD ROCs is bounded at 2.9 mrem/y. In addition, the licensee failed to report data for six ETD ROCs which it stated were never detected above the MDC and had negligible impact to the hypothetical dose estimate. This is contrary to the LTP; however, the NRC staff agree, after review of available data, that these ROCs would likely have minor impact on the hypothetical dose assessment and believe a conservative bounding estimate of 1 mrem/y should be assigned to these unreported ROCs in lieu of actual data. As such, the bounding hypothetical dose estimate from all deselected and non-reported site ROCs in soil should be 3.9 mrem/y. In addition, ingestion of residual radioactivity in groundwater is conservatively anticipated to contribute 1 mrem/y (see groundwater discussion in evaluation of survey unit OOL09-01).
Of the non-parametric samples collected, the maximum Cs-137 result is 0.082 pCi/g and the mean is 0.026 pCi/g. No sample had Cs-137 detected at a concentration exceeding the MDC.
The dose contribution from the average level of Cs-137 was determined to be approximately 0.08 mrem/y. Because no sample result exceeded the DCGL, the licensee concluded the Sign Test passed based on inspection. The total estimated hypothetical dose initially estimated by the licensee was 2.24 mrem/y; however, after revisions of bounding dose estimates for deselected and unreported ROCs and consideration of residual radioactivity in groundwater, NRC staff derived a bounding estimate of 5.0 mrem/y. Still far beneath the 25 mrem/y unrestricted release criteria.
The NRC staff also considered that the licensee did not take representative samples from the entire volume of backfilled material; instead, this material was screened through the GARDIAN system. However, the licensee had previously discussed the hypothetical dose from the fill materials as the GARDIAN system data showed relatively minor fluctuations in Cs-137 and Co-60 in the data. In response to RAI-4 (ADAMS Accession No. ML21165A092), the licensee summarized the GARDIAN system data for materials that were processed. The NRC staff estimated that the hypothetical dose from all pathways from backfill material would likely be bounded by an estimate of 5.96 mrem/y. The NRC staff further note that this is a relatively minor increase from the estimate of 5.0 mrem/y which was based on sampling data in the survey unit and, because the backfill materials were likely well mixed due to excavation and relocation of materials, disregarded the fill material as being of slightly higher possible impact, but ultimately of minor consequence, for determining hypothetical dose.
The licensee evaluated two split sample analyses and two recount analyses from the survey and found all to pass its criteria for quality measurements. This frequency of quality assurance is consistent with MARSSIM Table N.2 and the LTP. The split samples were also analyzed for HTD ROCs which is consistent with MARSSIM Section 4.3.2. Also, the licensee stated that approximately 100% of the survey unit was scanned which is consistent with MARSSIM guidance for Class 1 survey units. No exceedances of investigation levels were noted from either sampling or scanning.
The NRC staff concludes that the licensees survey and analyses for this survey unit provide reasonable assurance the licensee was able to demonstrate compliance with the unrestricted release criteria of 10 CFR 20.1402.
Conclusions The licensees FSS design criteria, implementation of the DQO process, and survey approach/methods were reviewed, and final results were assessed against the licensees approved release criteria. While some requirements in the LTP were not met (often the licensee failed to address all ROCs in the LTP and, in at least one instance, a scanning survey was not able to be completed to the rigor required), the NRC staff found these failures to be of minor consequence to the finding that the unrestricted release criterion were met because staff could conclude it to be very unlikely the unaddressed ROCs had significant impact and the scanning issue was addressed at the time the survey was conducted with the NRC staff and management consultation.
The NRC staff find the data in the licensee report dated May 21, 2020 (ADAMS Accession No. ML20142A287) and supplemented by response to RAIs (see ADAMS Accession Nos. ML20247J598, ML21063A474, and ML21165A092) adequate to provide reasonable assurance that the survey units designated as OOL09-01 through OOL09-10 (the discharge canal headworks (OOL09-01); the settling basins (OOL09-02); SMF West (OOL09-03); SMF East (OOL09-04); Bull Pen West (OOL09-05); Bull Pen East (OOL09-06); GWTS North (OOL09-07); GWTS South (OOL09-08); Asbestos Area (OOL09-09); and the Trail Buffer Zone (OOL09-10)) meet the unrestricted use criteria found in 10 CFR 20.1402.
The NRC staff noted that the licensees surveys of stacked survey for each survey unit is unconventional (each survey unit had an excavation survey and a final site remediation survey performed), and the criteria and assessments being performed assumed these were surface survey units when, in fact, both are subsurface. While a more accurate approach would be to perform a weighted average of the two surveys hypothetical exposure determinations, it also means that if both surveys meet the release criteria, then the survey unit would meet the release criteria as a whole. As such, the NRC staff reviewed each survey to determine if it demonstrated meeting the release criteria and found that all surveys in the submittal meet the release criteria, thus each survey unit in the submittal met the criteria.
The NRC staffs findings are supported by a confirmatory survey conducted by Oak Ridge Institute for Science and Education (ORISE) (an independent NRC contractor, see ADAMS Accession No. ML20021A128) in which scanning surveys and sampling was performed in these land areas. ORISE obtained and analyzed 18 soil samples from these areas and noted that the sample SOFs were all less than unity and no individual ROC exceeded 50% of the DCGLw confirming the licensees classification of the survey units. Also, no elevated areas were noted during scanning.
The NRC staff concludes that 1) the FSSs were effectively conducted in accordance with the LTP, as amended, even though some scanning surveys were deficient due to inaccessibility or backfill prior to the survey being conducted. The NRC staff independently evaluated data in the FSSRs and in response to RAIs and, in concurrence with the approved revised LTP, found the data adequate even though the licensee failed to appropriately address all site ROCs consistent with the LTP in some reports; (2) the FSSR and RAI responses contain the information identified in NUREG-1757, Consolidated NMSS Decommissioning Guidance, Section 4.5; and (3) the FSS results demonstrate that the residual radioactivity in survey unit(s) OOL09-01 through OOL09-10 meet the radiological criteria for unrestricted release identified in the LTP.
The NRC staffs conclusion is based on its review of the licensees FSSRs, survey release records, responses to RAIs, and the results of confirmatory surveys conducted by ORISE.