ML22277A448
| ML22277A448 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 07/05/2022 |
| From: | Marlayna Vaaler Doell Reactor Decommissioning Branch |
| To: | |
| Doell M, 301-415-378 | |
| Shared Package | |
| ML22277A350 | List: |
| References | |
| Download: ML22277A448 (4) | |
Text
1 Questions for Energy Solutions on La Crosse Class 1 Excavation and Basement Survey Units
- 1. General. Is there a procedure for establishing background radiation levels in land survey areas (specifically excavation areas)? How was background established for the survey scans?
- 2. B1-010-004. The November 2020 RAI response (RAI 1e) indicated that the pre and post-rain event scan data for the WGTV was included in the revised release record, but the pre and post scan data from before and after the rain event that caused intrusion to the WGTV Basement does not seem to be in the revised release record. Please verify that Revision 1 of the release record is the correct revision that is meant to have the pre and post-rain event scan data.
- 3. B1-010-004. The maximum insignificant contributor (IC) dose calculated by the licensee for the continuing characterization samples was 0.5042 mrem/yr for the concrete core samples and 0.1437 mrem/yr for the soil samples, which is below the 2.5 mrem/yr limit provided in the LTP for DCGL adjustment. Please provide the detailed calculations for this maximum IC dose.
- 4. B1-010-004. The licensees response to RAI 3g states:
No additional remediation took place in the WGTV Basement after the continuing characterization cores were obtained. The ISOCS results from the survey reflect the expectations of the results with the cores. The highest ISOCS result, 1.32E+7 pCi/m2 was obtained from the WGTV sump, which also had the highest Cs-137 concentration of 148 pCi/g. The value of 148 pCi/g when converted to pCi/m2 is 4.42E+6 pCi/m2. The mean and median of the systemic measurements of 5.77E+4 and 3.77E+4 pCi/m2, equate to 1.94 and 1.27 pCi/g of Cs-137. This is in line with the sporadic contamination within the area and the use of a 28.3m2 field of view for the ISOCS measurements.
Please provide the assumptions and/or detailed calculations supporting these conversions from pCi/m2 to pCi/g. Please also provide additional justification as to why additional remediation did not take place in this survey unit given the results of the continuing characterization samples.
- 5. L1-SUB-TDS. Two of the eight continuing characterization samples in the Turbine Building Excavation were positive for Tc-99 but they contained no other radionuclides above MDC. Has the licensee calculated the relative dose contribution at this concentration for Tc-99? The average concentration of Tc-99 for soils from characterization was 0.576 pCi/g, and the staff notes that this is not far off from what was assumed to derive the IC dose contribution.
However, if the relative proportion of the radionuclides was assumed to be consistent, the staff believes these samples would also have been positive for Cs-137. Could ES provide the analysis that shows or a discussion that supports that this meets the original IC dose contribution assumptions? The staff notes that the associated RAI path forward (RAI 3) asked for detailed calculations to estimate the actual IC dose for each individual sample result.
- 6. L1-SUB-TDS. ORISE conducted a confirmatory survey of the Turbine Building Excavation survey unit from January 15-18, 2018. The results of the confirmatory survey concluded that LACBWRs FSS design and implementation were appropriate and reported results were acceptable for demonstrating compliance with the release criteria given that all the radionuclide
2 concentrations in measurements obtained in the confirmatory survey were at least an order of magnitude less than the respective Operational DCGLs.
The ORISE confirmatory survey noted that the physical boundary established by LACBWR for the turbine building excavation did not match the planned boundary established in the GIS files as indicated by the difference in where ORISE performed scans and the blue line at the southern portion of the survey unit in the associated figures. The survey also stated that the post-survey review of the gamma walkover maps showed a discrepancy between the planned survey unit boundary and the physical boundary observed in the field. Please confirm that the boundaries of the survey units surrounding the excavation survey unit of L1-SUB-TDS share physical boundaries such that 100 percent of the soil area was investigated. Please explain the difference in this survey unit boundary, and confirm that the portion of the survey unit that was not scanned by ORISE during their confirmatory survey was scanned by the licensee during FSS.
- 7. L1-SUB-TDS A. Why was one continuing characterization sample in the Eastern Portion of the Turbine Building, Sump, Pit, and Diesel Excavation survey unit considered adequate? From where in the survey unit was it taken? Was it taken from the highest risk area (sump area)?
- 8. L1-SUB-TDS B. For the RPGPA Excavation continuing characterization samples and RASS samples, please provide the location of where the samples were taken. Provide a map with the continuing characterization and RASS sample locations (in Figure 16-1 or a new Figure 16-2).
- 9. L1-SUB-TDS B. The release record states that the maximum IC dose in the survey unit was 0.6373 mrem/yr, and then also states that the IC dose from Sump Area #1 is 0.4987 mrem/yr. It is confusing that the IC dose from samples with none of the insignificant radionuclides above MDC would be higher than that for Sump Area #1, which had several insignificant radionuclides above MDC. Could you please provide the detailed calculations? Was the material represented by the Sump Area #1 soil sample removed or left in place?
- 10. L1-010-101 C. Were there any continuing characterization samples taken before backfilling either prior to or during the original FSS of the Waste Treatment Building (WTB) Excavation? If so, may we have the results from those samples? How about the samples collected as part of the NRC inspection activities? Were they analyzed for any other radionuclides?
- 11. L1-SUB-DRS. For the Radiologically Controlled Area North Excavation, please explain why continuing characterization was not necessary in this survey unit. Why was the original characterization of the above land survey unit deemed adequate for this survey unit and no samples sent off for analysis for the full suite of initial radionuclides?
- 12. L1-SUB-LES. There were several alarms during the RASS prior to FSS of the Low Specific Activity (LSA) Building, Eat Shack, and Septic Excavation survey unit, and this area received additional remediation. The Cs-137 concentration was 29 pCi/g, and the Co-60 concentration was 85.7 pCi/g in the samples taken prior to FSS. However, there were no continuing characterization samples taken as per Section 5.3.3.4, Inaccessible or Not Readily Accessible Areas, of the LACBWR LTP. What was the process to decide that no continuing characterization samples would be collected given that this was a previously uncharacterized area?
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- 13. L1-SUB-CDR. In the RPGPA Excavation survey unit, the Cs-137 value measured using gamma spectroscopy on NRC Sample #4 was 1.52 pCi/g compared to the 171 pCi/g measured in the lab.
The NRC asked for additional information on the difference between NRC Sample #4 gamma spectroscopy measurements versus the GEL Laboratory results. The licensee responded stating:
Sample NRC-CDR #4 is believed to have been split from a different sample coming from the RPGPA area, which was split from the unit due to necessary remediation. It is believed the split may have been from one of the sump samples. This is supported by the results of the concrete core sampling of the tunnel, which was the structure removed for the unit. Sample results from the concrete cores, B1008101-CJ-FC-002-CV 0-1/2, B1008101-CJ-FC-003-CV 0-1/2, and B1008101-CJ-FC-004-CV 0-1/2 were 16.0, 10.0, and 19.8 pCi/g for Cs-137.
These were biased concrete core samples of the source of the remediation (concrete tunnel), which were removed and contained much less activity than NRC-CDR #4.
Please walk through the connection between these concrete core sample results and the Cs-137 concentrations in NRC Sample #4. If the NRC Sample #4 Cs-137 concentrations were really associated with the sump samples that were remediated, this needs to be explicitly stated and supported with some sort of basis. The staff notes that this was not described in the associated release record and is an important aspect of the final status survey.
As the release record reads, the NRC Sample #4 results are presented as an investigational sample with radionuclide concentrations above the DCGLs (both Operational and Base Case) that was not remediated. Please clarify if the soil associated with NRC Sample #4 was remediated and consider updating the release record to clarify this situation and the relationship of the NRC Sample #4 results to the final status of the survey unit.
- 14. The NRCs RAI 5 stated that the release record for the WGTV Basement contains information in Table 7-4, Summary of Replicate ISOCS Measurements for QC, Section 8, and Attachment 4 on two replicate ISOCS measurements acquired during the FSS of the basement structure.
According to Attachment 4 and Section 8 of the release record, both pairs of measurements did not identify any radionuclides in the samples. The licensee stated that their acceptance method could not be utilized for this situation, and since the detectable radioactivity levels were well below the OpDCGL for basements, no further action was deemed necessary.
Based on a review of the survey data in Attachment 6 of the release record, the Cs-137 concentrations in the original and quality control (QC) samples were above the reported MDCs.
For sample B1-010-004-QSFC-03-GM, the values are 2.13E+05 pCi/m2 with an MDC of 4.81E+04 pCi/m2; and for sample WGTV-03, the values are 1.93E+05 pCi/m2 with an MDC of 4.72E+04 pCi/m2. For sample B1-010-004-QSWC-10-GM, the values are 2.83E+04 pCi/m2 with an MDC of 2.20E+04 pCi/m2; and for sample WGTV-10, the values are 2.62E+04 pCi/m2 with an MDC of 2.38E+04 pCi/m2. Given that both the QC and original ISOCS measurements have Cs-137 concentrations above the associated MDCs, the licensee should provide the QC analysis or a discussion of why this approach is acceptable. The licensee should also explain why of the release record does not agree with the raw data, which matches the data summarized in Table 7-4 of the release record.
4 The RAI response states that in this case, both pairs of standard and comparison measurements contained insignificant or no detectable radioactivity, and all were well below the OpDCGLB.
However, the staff notes that there is a difference between saying there was nothing above MDA and saying it was slightly above MDA. Please provide clarification on this response.