ML090930072
| ML090930072 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 12/10/2008 |
| From: | Frank G Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097 | |
| Download: ML090930072 (16) | |
Text
Rancho Seco Final Status Survey Summary Report December 10, 2008 Tank Farm Trench #1 Eastern Portion Subsurface Soil Survey Unit F8100053 Prepared By _ Q Date: /Z-/1/6 -46 FSS Engineer Reviewed ByLA-Ocyt I -SA Date: [
Lead FSS Engineer ApprovedBy: Date:
Dismantlement S 4-erintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8100053, Tank Farm Trench #1 Eastern Portion Subsurface Soil Survey Unit
Description:
Operating History: The area surrounded the tanks used to store radioactive liquids. This area was used for the storage of radioactive material. Operating records and the HSA document several events with the potential for a release of radioactivity associated with this survey area. The HSA documented the storage of radioactive material within the area that may have had the potential to contaminate the area.
Records of soil samples taken near the BWST showed soil contamination levels as high as 230 pCi/g prior to remediation.
Site Characterization: Soil samples were collected and analyzed for the presence of plant-derived radionuclides. Cs-137 was the primary nuclide of plant origin detected with a mean activity level of 379 pCi/g and a maximum value of 1,040 pCi/g. Based on the classification procedure (DSIP-0020) and levels of Cs-137 reported, the area was determined to be a Class 1 land area.
Based on results of soil samples and measurements acquired during buried piping remediation the subsurface area was determined to be a Class 2 land area.
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. The purpose of this survey unit was to perform subsurface evaluation at -1 meter and -2 meters below the surface of the area outside the equipment hatch. The surface area outside the equipment hatch is covered under F8100052. Direct measurement locations were determined using a random-start, fixed grid pattern. Soil samples were collected at each direct measurement location and analyzed by HPGe 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 F8100053
Table 1. Survey Unit Design Parameters Survey Design Parameter[ Value Comment Survey Area: F810 Tank Farm Trench #1 Eastern Portion Subsurface Soil Survey Unit: 0053 Open Land Area Class: 2 LTP Table 5-4 SU Area (m): 660 Evaluator: Gary Frank DCGL Cs137 surrogate (pCi/g): 51.2 Area Factor: N/A Class 2 Design DCGLemc (pCi/g): N/A Class 2 LBGR (pCi/g): 25.6 Default = 50% DCGL Design Sigma (pCi/g): 0.1 DTBD-06-001, Table 5-4D Type I Error: 0.05 Type II Error: 0.05 Nuclide: Cs137 Sample Area (m2): 27.5 Class 2 Total Area Scanned (m2): 660 Scan Coverage (%): 100% Class 2 Zl-, : 1.645 ZI-p : 1.645 Sign P: 0.99865 Calculated Relative Shift: 256 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: 6.9 Class 2 Page 3 of 7 FSS Summary Report F8100053
Survey Results:
A total of 28 direct measurements were made in F8100053. 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 direct 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: 94.62E-02 Median: -4.417E-02 Standard Deviation: - -11 1. E02 __________
Range: 2.64E-02 to 7.45E-02 F8100053SOO01SS 5.05E-02 < 5.05E-02 F8100053S0002SS 5.63E-02 < 5.63E-02 F8100053S0003SS 4.56E-02 < 4.56E-02 F8100053S0004SS 5.39E-02 < 5.39E-02 F8100053S0005SS 3.72E-02 < 3.72E-02 F8100053 SO006SS 5.95E-02 < 5.95E-02 F8100053S0007SS 6.07E-02 < 6.07E-02 F8100053S0008SS 4.89E-02 7.45E-02 3.58E-02 F8100053S0009SS 5.87E-02 < 5.87E-02 F8100053SOO1OSS 4.75E-02 < 4.75E-02 F8100053S0011SS 4.48E-02 < 4.48E-02 F8100053S0012SS 5.38E-02 < 5.38E-02 F8100053S0013SS 3.95E-02 < 3.95E-02 F8100053S0014SS 5.56E-02 < 5.56E-02 F8100053S0015SS 5.96E-02 < 5.96E-02 F8100053S0016SS 3.81E-02 < 3.81E-02 F8100053S0017SS 3.56E-02 < 3.56E-02 F8100053S0018SS 4.46E-02 < 4.46E-02 F8100053S0019SS 2.92E-02 < 2.92E-02 F8100053S0020SS 3.99E-02 < 3.99E-02 F8100053S0021SS 3.29E-02 < 3.29E-02 F8100053S0022SS 4.81E-02 < 4.81E-02 F8100053S0023SS 3.43E-02 < 3.43E-02 F8100053S0024SS 4.34E-02 < 4.34E-02 F8 100053S0025SS 3.64E-02 < 3.64E-02 F8100053S0026SS 4.25E-02 < 4.25E-02 F8100053S0027SS 4.41E-02 < 4.411E-02 F8100053S0028SS 2.64E-02 < 2.64E-02 Page 4 of 7 PFSS Summary Report F8100053
Survey Unit Data Assessment:
The survey design required 28 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 F8100053
Table 3. Data Assessment Results Survey Results Parameter Value Comment Actual Direct Measurements (N): 28 Median (pCi/g): 4.47E-02 Mean (pCi/g): 4.62E-02 Standard Deviation (pCi/g): 1.11 E-02 Maximum (pCi/g): 7.45E-02 Sign Test Final N Value: 28 S+ Value: 28 Critical Value: 18 Sufficient Samples Collected: Yes Maximum Value < DCGL: Yes Median Value < DCGL: Yes Mean Value < DCGL: Yes Maximum Value < DCGLemc: N/A Class 2 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 F8100053
Survey Unit Investigations and Results:
No investigations were required for direct 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, the ALARA criterion has been met.
Changes in Initial Survey Unit Assumptions:
The survey unit was designed as a Class 2 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 2 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 F8100053 meets the release criteria of 10CFR20.1402.
Page 7 of 7 FSS Summary Report F8100053
Attachment 1 Maps December 10, 2008 Survey Unit F8100053
Trench 1 Eastern Portion 0
t'Q Soil Samples at Depth Samples 1 to 12 -15cm to -115cm 13 to 24 -115cm to -215cm cd~
It Random Start 15 WE 4 NS 0....
. *.. . ,0. . . .*
0 1g5 2.-* . . . 30...
f20 25
.3.
gutter
. -.0. .45 00 C/i Edge of concrete gutter U.
F8100053-MI
Attachment 2 Instrumentation December 10, 2008 Survey Unit F8100053
Table 2-1. Survey Unit Instrumentation Detector Detector Detector SerialMD Instrument Model oMDC No.
No.
Soil - 0.026 pCi/g Cs-137, HPGe N/A 050691280.0306 pCi/g Co-60 Table 2-2. Investigation Criteria and DCGL Instrument Parameter Value ISOCS InvestigationCriteria - Scan Soil -20 pCi/g Cs-137 Soil - 6 pCi/g Co-60 All DCGLw 51.2 Cs-137 12.6 Co-60 Page 2 of 2 Att. 2 Instrumentation F8100053
Attachment 3 Investigation December 10, 2008 Survey Unit F8100053 (none required)
Attachment 4 Data Assessment December 10, 2008 Survey Unit F8100053
-e CIQ F8100053 Quantile Plot Cs137 DCGL = 51.2 pCi/g 0.080 0.070 0.060 0.050 G0. 0.045 0.040 00 .5 0
0.030 0.020 0.010 U)
Cn 0.000 0 20 40 60 80 100 Percentile
- Activity - Median -- - 75th Percentile - - - - 50th Percentile C)
C)I
FBI100063 Scatter Plot Cs137 DCGL -61.2 pClIg 9.00E-02 8.00 E-02 ----------------- - - - - - - - - 0.079, 7.00E-02
&OE-2 0 0 0 5 .00E 2..- .4
> 4.00E-02 0 Cn ~3.00E-02 a 2.00E-02
- - - - - -001 I .00E-02 -- --- - - - - -
0,00E*00r t0 Measurement Locations oD
F8100053 Frequency Plot Cs1 37 DCGL = 51.2 pCi/g 14 13 12-11 10
¢.2 9 8-0- 7 0 6 00 5
U) 4--
OQ 3 2
C.
1 0
r& &
t~v V
Bins - Upper End Value (pCi/g)