ML081610116
| ML081610116 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 03/27/2008 |
| From: | Tallman D A Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| References | |
| F2000001 | |
| Download: ML081610116 (18) | |
Text
Rancho Seco Final Status Survey Summary Report March 27, 2008 South Buffer/Ouffall Area Survey Unit F2000001.Prepared By: Dan A. Tallman te: March 27, 2008 Reviewed By: Date: Lead S Engineer Approved By: S Date:____________
Dismantlement Superintendent, Radiological FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit: F2000001, South Buffer/Outfall Area Survey Unit
Description:
Operating History: This area bordered the release point for non-controlled/unmonitored liquid effluents released from the plant (ie. storm drains). The area extended from the south Industrial Area fence to the South Non-Impacted Area. Operating records and the HSA document the release of radioactivity in this survey area. The HSA recorded several unplanned release events from the RHUT with the potential to contaminate the area.Site Characterization:
Soil and sediment samples were collected and analyzed for the presence of plant-derived radionuclides.
A special gamma scan survey was performed using vehicle-mounted HPGe detectors.
Cs-137 was the. only detected nuclide of plant origin with a mean activity level of 0.129 pCi/g and a maximum value of 0.301 pCi/g.(Site background levels of Cs-137 have been determined to be approximately 0.312 pCi/g.) As described in section 2 of the LTP, the area was evaluated and determined to be"not significantly different from background", however based on the history of spills along the south industrial area fence, the area was designated as a Class 3.HSA Events: ODR-740017, 840217, 840317.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 2268 m 2 were scanned for approximately 1%coverage.
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 F2000001
- Table 1. Survey Unit Design Parameters Survey Design Parameter
'Value Comment Survey Area: F200 South Buffer/Outfall Area Survey Unit: 0001 Open Land Area Class: 3 LTP Table 5-4 SU Area (m2): 226567 Evaluator:
D.A.Tallman DCGL Cs137 surrogate (pCi/g): 51.2 Area Factor: N/A Class 3 Design DCGLeme (pCi/g): N/A Class 3 LBGR (pCi/g): 25.6 Default = 50% DCGL Design Sigma (pCi/g): 0.15 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): 2268 Scan Coverage (%): 1% Class 3 Zl-, : 1.645: 1.645 Sign P: 0.99865 Calculated Relative Shift: 170.6 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 F2000001 Survey Results: A total of 14 direct measurements were nmade in F2000001.
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 Attachment 2.Table 2. Direct Measurement Results (all activity values in pCi/g)Measurement ID Cs137 MDA Cs137 Activity Uncertainty Mean: .2.72E-01 Median: j--------2 75E-01 Standard Deviation:
> ; K -1.59E-01 Range: 5.13E-02 to 5.311E-01 F2000001SOOOISS 7.14E-02 < 7.14E-02 F2000001SO002SS 7.56E-02 2.53E-01 6.66E-02 F2000001S0003SS 1.15E-01 1.79E-01 1.21E-01 F2000001 SO004SS 6.92E-02 3.81E-01 9.07E-02 F2000001 SO005SS 5.77E-02 1.69E-01 5.11E-02 F2000001SO006SS 7.53E-02 5.1OE-01 1.14E-01 F2000001SO007SS 7.82E-02 2.97E-01 7.26E-02 F2000001SO008SS 7.65E-02 5.31E-01 1.07E-01 F2000001SO009SS 1.04E-01 < 1.04E-01 F2000001SOO1OSS 5.13E-02 < 5.13E-02 F2000001S0011SS 7.69E-02 3.3 1E-01 7.88E-02 F2000001S 0012SS 8.2 1E-02 1.27E-01 5.65E-02 F2000001S0013SS 8.49E-02 4.09E-01 8.14E-02 F2000001 S0014SS 7.86E-02 3.93E-01 9.02E-02 Page 4 of 7 FSS Summary Report F2000001 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 greater than the design standard deviation.
Since both values of sigma resulted in a relative shift greater than three (3), no additional samples were required.Page 5 of 7 FSS Summary Report F2000001 Table 3. Data Assessment Results Survey Results Parameter Value Comment Actual Direct Measurements (N): 14 Median (pci/g): 2.75E-01 Mean (pCi/g): 2.72E-01.Standard Deviation (pCi/g): 1.59E-01 Maximum (pci/g): 5.3 1E-0 1 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: Investigate Sufficient number of sample acquired Pass the Sign Test? Yes Reject the Null Hypothesis?
Yes.The survey unit passes all conditions?
Yes Standard Deviation vs.design sigma (0.15 vs.0.159) did not alter required number of samples or evaluation outcome.Page 6 of 7 FSS Summary Report F2000001 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 greater than the characterization data used for survey design. No potential areas of elevated activity were detected; therefore the EMC criterion was met.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 F2000001 meets the release criteria of 1 OCFR20.1402.
Page 7 of 7 FSS Summary Report F2000001 Attachment 1 Maps March 27, 2008 Page I of 4 Att. 1 Maps F200000i 0 k)0 STORM4 DRAIN'-35.75E KF 86.08N 8,14434.ODE
-1587985.16NM 21 72.05E 138SO0!33 6812668.50E IP.58006.9214
-6812812.2 C 135I 555.,0E 1383842.0N 1887848,75N
-81371 I.I 2265!87SQLER-SOIL 13 58: 1786.75 E.1886976.50Nl 10 30 510 C, 20 40 SCALL 7ETERs C:)CD C: 3 W) SMUD SACRAMENTO MUNICIPAL UTIL'Y DISTRICT SOUTH PLANT OUTFALL SURVEY UNIT BOUNDRIES F2000001 -Ml
-o ('D 0 STORM DRAIN-BUFFER KQJ 6813656 1867846' 6812458E 1887666N 6813629a 1887519N 68138396 1887438N 681'2 446 1887168N 10 30 50 0 20, 40 SCALE METERS SMUD S.SACRAMENTO MUNICIPAL UTILITY DISTRICT SOUTH PLANT OUTFALL SAMPLE LOCATION OVERVIEW F2000001 -M2 (0 STOR ORIN GUrFER S~~CRLc-.
M~~~ %J~s c," , as'pa Scn CUUjERT PIPC --7"43,RT PIPE'7$ "'~w-/ / / k4P~NEMEN\\~
'A1S 6i 6 Sdn 43-47~, $a~n5 28-32 I-ý3 Scans S 14 NJIE1 LEWY FENCE 1 to 30 57 1 0 20 40 METEIOS SOUTH PLANT OUTFALL SMUD1 SCAN LOCATION OVERVIEW SACRAMENTO MUNI IPAt UTIl' DITRCTF2000001 -M3 FLE:zOC0 .RC FlAymn Attachment 2 Instrumentation March 27, 2008 Survey Unit F2000001 Table 2-1. Survey Unit Instrumentation Detector Detector Serial Instrument Model MDC No. No.HP'Ge N/A 9987008 Soil- 0.115 pCi/g Cs-137 Soil -0.0712 pCi/g Co-60 Soil -0.104 pCi/g Cs-137 Soil -0.0699 pCi/g Co-60 Soil -0.301 pCi/g Cs-137 ISOICS N/A 1983920 Soil -0.211 pCi/g Co-60 Soil -0.323 pCi/g Cs-137 I NA234Soil
-0.197 pCi/g Co-60 Table 2-2. Investigation Criteria and DCGL Instrument Parameter Value Soil -23 pCi/g Cs-137 ISOCS Investigation Criteria -Scan Soil -2 pCi/g Co-60 Soil ý- 5 pCi/g Co-60 All DCGLw 52.6 Cs-137 1_ 1 12.6 Co-60 Page 2 of 2 Att. 2 Instrumentation F2000001 Attachment 3 Investigation March 27, 2008 Survey Unit F2000001 (none required)Page I of I Att. 3 Investigation Attachment 4 Data Assessment March 27, 2008 Survey Unit F2000001 tk)C/2 (D Cn F2000001 Quantile Plot Cs137 DCGL = 52.6 pCi/g 0.600 0.500 0.400 0.40.0.300 0.200 0.100 0.000 0.275 0 20 40 60 80 Percentile
- Acti~ity ~- Median --- 75th Percentile
-- -- 50th Percentile 100 0 0 F2000001 Scatter Plot Cs137 DCGL = 52.6 pCi/g C/2 En (/2$,oaE-o1 6.0OE-01 4.OOE.O1 2.OOE-O1 O.OOE+0O-7-OOE -4.0012-01 0 00 o 0 0 00-t 2 7 2-----------------------0.207 I I I -Measurement Locations I o Activity -Average --"+3SIEev" --'-3Sev"l C)
CD)Cl)03 F2000001 Frequency Plot Csl 37 DCGL = 52.6 pCi/g 0 6 5 4 3 2 1 0z~AN N (V.N:.N (5 Bins -Upper End Value (pCi/g)