ML081580580
| ML081580580 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/05/2008 |
| From: | Tallman D Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| References | |
| F8480021 | |
| Download: ML081580580 (18) | |
Text
Rancho Seco Final Status Survey Summary Report March 31, 2008 Retention Basin Buffer Area Survey Unit F8480021 Prepared By: Dan A. Tallman
- %-~-Date
- April 1, 2008 Date: 4-,' t#S Reviewed Lead FS En ineer Approved By:
Date:
Dismantlement Superintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8480021, Retention Basin Buffer Area Survey Unit
Description:
Operating History: This area is located at. the southwest comer of the site. The area surrounds the structures that were used for containment and final treatment of liquid effluents prior to their release from the site. Contaminated resin was reported to have been found in the basins. Operating records and the HSA document occurrences of radioactive material with the potential for a release of radioactivity associated with this survey area. Records confirmed the presence of radioactive material within the area and basin sediment/soil contamination levels up to -290 pCi/g. In addition, soil contamination levels up to -5 pCi/g prior to some decontamination activities.
Site Characterization: Soil samples were collected and showed Cs-137 at mean activity levels of 0.086 pCi/g and a maximum activity of 0.196 pCi/g. Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the soil area around the asphalt was determined to be Class 3.
HSA Events: LER-8812.
Survey Unit Design Information:
The Survey Unit Design Parameters are presented in Table 1 below. The survey unit and measurement locations are depicted on the maps in Attachment 1. Direct measurement locations were randomly determined and 1484 m2 were scanned for approximately 14%
coverage. Soil samples were collected at each direct measurement location and analyzed byHPGe detector. The instrumentation used for the survey along with the MDC values are listed in Tables 2-1 and 2-2 in Attachment 2.
Page 2 of 7 FSS Summary Report F8480021
Table 1. Survey Unit Design Parameters Survey Design Parameter Value Comment Survey Area:
F848 Retention Basin Buffer Area Survey Unit:
0021 Open Land Area Class:
3 LTP Table 5-4 SU Area (m2):
10845 Evaluator:
D.A.Tallman DCGL Cs137 surrogate (pCi/g):
51.2 Area Factor:
N/A Class 3 Design DCGLemc (pCi/g):
N/A' Class 3 LBGR (pCi/g):
25.6 Default 50% DCGL Design Sigma (pCi/g):
0.047 DTBD-06-001, Table 5-4D Type I Error:
0.05 Type II Error:
0.05 Nuclide:
Cs137 Sample Area (m2):
'N/A Class 3 Total Area Scanned (m2):
1484 Scan Coverage (%o):
13.7%
Class 3 Zi.a:
1.645 1.645 Sign P:
0.99865 Calculated Relative Shift:
544.6 Relative Shift Used:
3 Uses 3.0 if Rel Shift >3 N-Value:
11 Design N-Value + 20%:
14 NUREG-1575 Table 5-5 Grid Spacing L:
N/A Class 3 Page 3 of 7 FSS Summary Report F8480021
Survey Results:
A total of 14 direct measurements were made in F8480021. The results including mean, median, standard deviation and range are shown in Table 2. All of the direct measurements were less than the DCGL. None of the scan measurements indicated areas of elevated activity. Soil samples were counted to the MDC shown in Table 2-1 of.
Table 2. Direct Measurement Results (all activity values in pCi/g) -
Measurement ID Cs137 MDA Cs137 Activity Uncertainty Mean:
6.25E-02 Median: <~5.66E-02 Standard Deviation:
2.49E-02 Range:
4.27E-02 to 1.46E-01 F8480021S0001SS 4.94E-02
< 4.94E-02 F8480021S0002SS 5.15E-02
< 5.15E-02 F8480021S0003SS 5.1OE-02
< 5.1OE-02 F8480021S0004SS 5.80E-02
< 5.80E-02 F8480021S0005SS 5.52E-02
< 5.52E-02 F8480021S0006SS 7.03E-02
< 7.03E-02 F8480021S0007SS 6.20E-02
< 6.20E-02 F8480021S0008SS 6.03E-02
< 6.03E-02 F8480021S0009SS 4.27E-02
< 4.27E-02 F8480021S00lOSS 5.34E-02
< 5.34E-02 F8480021S0011SS 6.01E-02
< 6.01E-02 F8480021SO012SS 5.46E-02
< 5.46E-02 F8480021SO013SS 6.80E-02 1.46E-01 5.18E-02 F8480021S0014SS 6.12E-02
< 6.12E-02 Page 4 of 7 FSS Summary Report F8480021
Survey Unit Data Assessment:
The survey design required 14 direct measurements for the Sign Test. The critical value and the results of the Sign Test are presented in Table 3. The sample mean and median values were less than the DCGL. The sample standard deviation was less than the design standard deviation so no additional samples were required.
Page 5 of 7 FSS Summary Report F8480021
Table 3. Data Assessment Results Survey Results Parameter Value Comment Actual Direct Measurements (N):
14 Median (pCi/g):
5.66E-02 Mean (pci/g):
6.25E-02 Standard Deviation (pCi/g):
2.49E-02 Maximum (pCi/g):
1.46E-01 Sign Test Final N Value:
14 S+ Value:
14 Critical Value:
10 Sufficient Samples Collected:
Yes Maximum Value < DCGL:
Yes Median Value < DCGL:
Yes Mean Value < DCGL:
Yes Maximum Value < DCGLemc:
N/A Class 3 Standard Deviation <= Sigma:
Yes Pass the Sign Test?
Yes Reject the Null Hypothesis?
Yes The survey unit passes all conditions?
Yes Page 6 of 7 FSS Summary Report F8480021
Survey Unit Investigations and Results:
No investigations were required for either direct or scan measurements and no investigation results are reported.
ALARA Statement:
As stated in Chapter 4 of the LTP, as long as the residual activity within the survey unit is less than the DCGL (i.e. the survey unit average activity is less than the DCGL and the EMC criterion has been met), the ALARA criterion has been met.
Changes in Initial Survey Unit Assumptions:
The survey unit was designed as a Class 3 land survey and the sample results are consistent with that classification. The variability of the survey results was less than the characterization data used for survey design. No potential areas of elevated activity were detected.
==
Conclusion:==
The FSS of this survey unit was properly designed as a Class 3 survey based on Table 5-4 of the LTP. The required number of direct measurements was made and the scan coverage met the requirement of Table 5-6 of the LTP. All of the direct measurements were less than the DCGL. No investigations were required.
The direct measurement data support rejection of the null hypothesis, providing high confidence that the survey unit satisfied the release criteria and that the data quality objectives were met.
It is concluded that survey'unit F8480021 meets the release criteria of 10CFR20.1402.
Page 7 of 7 FSS Summary Report F8480021
Attachment I Maps March 31, 2008 Survey Unit F8480021
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.Attachment 2 Instrumentation March 31, 2008 Survey Unit F8480021
Table 2-1. Survey Unit Instrumentation Detector Detector Serial Instrument Model MDC No.
No.
HPGe N/A 05069128 Soil - 0.0713 pCi/g Cs-137 Soil - 0.0642 pCi/g Co-69 ISOCS N/A 2983947 Soil -0.328 pCi/g Cs-137 Soil - 0.215 pCi/g Co-60 Table 2-2. Investigation Criteria and DCGL Instrument Parameter Value HPGe Investigation Criteria Soil -25.6 pCi/g Cs-137 Soil - 6.3 pCi/g Co-60 Soil - 20 pCi/g Cs-137 ISOCS Investigation Criteria -Scan Soil -
5 pCi/g Co-13 Soil - 5 pCi/g Co-60 All DCGLw 51.2 Cs-137 12.6 Co-60 Page 2 of 2 Att. 2 Instrumentation F8480021 Investigation March 31, 2008 Survey Unit F8480021 (none required)
Data Assessment March 31, 2008 Survey Unit F8480021
00 C)i F8480021 Quantile Plot Csl37 DCGL = 51.2 pCi/g 0
C-,
0.160 0.140 0.120 0.100 0.080 0.060 0.040 0.020 0.000 0,057 0
20 40 60 Percentile 80 100 I
- Activity
-Median
- - 75th Percentile ----
50th Percentile I
00*
A F8480021 Scatter Plot Cs137 DCGL = 51.2 pCIIg A
0 0
1.601E-01 1.40E-01 1.20E-01 1.00E-01 8.OOE-02 6.00E-02 4.00E-02 ICOE-02 0.OOE+00
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Average--
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F8480021 Frequency Plot Cs] 37 DCGL = 51.2 pCi/g 12 10 S9 4-,
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