ML081580589
| ML081580589 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/01/2008 |
| From: | Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| References | |
| F8510001 | |
| Download: ML081580589 (22) | |
Text
Rancho Seco Final Status Survey Summary Report March 25, 2008 Switch Gear Yard Survey Unit F8510001 Prepared B Date:_______
Reviewed By:
Date:___________
Approved By:___
Date:
-O' Dismantlement Superintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F85 10001, Switch Gear Yard Survey Unit
Description:
Operating History: The area consisted of both paved and soil covered land. The area was located on the west side of the IA and contained the electrical switchgear for the system grid. Operating records and the HSA document the storage of radioactive material within the area.
Site Characterization: Soil samples were collected and showed Cs-137 at mean activity levels of 0.056pCi/g and a maximum activity of 0.072 pCi/g. Based on the classification procedure (DSIP-0020) and levels of activity reported, the area was determined to be a Class 3 area.
HSA Events: HSA Report pg. 64.
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 832 m2 were scanned for approximately 5%
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 F8510001
Table 1. Survey Unit Design Parameters Survey Design Parameter Value Comment Survey Area:
F851 Switch Gear Yard Survey Unit:
0001 Open Land Area Class:
3 LTP Table 5-4 SU Area (m2):
16700 Evaluator:
Gary Frank 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):
0.008 DTBD-06-001, Table 5-4D Type I Erior:
0.05 Type II Error:
0.05 Nuclide:
Cs137 Sample Area (m2):
N/A Class 3 Total Area Scanned (M2):
832 Scan Coverage (%):
'5% Class 3 ZI-, :
1.645 ZI-p :
1.645 Sign P:
0.99865 Calculated Relative Shift:
3200 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 F85 10001
Survey Results:
A total of 14 direct measurements were made in F85 10001. The results including mean, median, standard deviation and range are shown in Table 2. All of the direct measurements were less than the DCGL. 90 scan measurements were performed with. all below the investigation level except one. Grid 57 indicated elevated activity is documented in Attachment 3. 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:
6.12E-02 Median:
5.85E-02 Standard Deviation:
1..60E-02 Range:
3.58E-02 to 9.02E-02 F8510001S0001SS 4.95E-02
< 4.95E-02 F8510001S0002SS 5.46E-02
< 5.46E-02 F8510001S0003SS 5.59E-02
< 5.59E-02 F8510001S0004SS 4.76E-02
< 4.76E-02 F8510001S0005SS 5.50E-02 6.92E-02 3.81E-02 F8510001SO006SS 5.23E-02
< 5.23E-02 F8510001S0007SS 6.11E-02
< 6.11E-02 F8510001S0008SS 5.81E-02 7.32E-02 4.06E-02 F8510001S0009SS 4.36E-02
< 4.36E-02 F8510001SOOlOSS 5.67E-02 6.84E-02 3.88E-02 F8510001S0011SS 4.71E-02 9.02E-02 3.64E-02 F8510001SO012SS 3.58E-02
< 3.58E-02 F8510001S0013SS 6.75E-02
< 6.75E-02 F8510001 SO014SS 5.82E-02 8.86E-02 4.15E-02 Page 4 of 7 FSS Summary Report F8510001
.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 but no additional samples were required.
Page 5 of 7 FSS Summary Report F8510001
Table 3. Data Assessment Results Survey Results Parameter Value Comment Actual Direct Measurements (N):
14 Median (pCi/g):
5.85E-02 Mean (pCi/g):
6.12E-02 Standard Deviation (pCi/g):
1.60E-02 Maximum (pCi/g):
9.02E-02 Sign Test Final N Value:
14 S+ Value:
14 Critical Value:
9 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 Results <0.5 DCGL Pass the Sign Test?
Yes Reject the Null Hypothesis?
Yes The survey unit passes all conditions?
Investigate Survey Passes Page 6 of 7 FSS Summary Report F851oo601
Survey Unit Investigations and Results:
One investigation (scan grid 57) was required for a scan 5 cpm above the investigation level. A rescan of the grid resulted in a count rate of 7000 cpm. Three gamma direct measurements were performed with results less than MDA for both Cs-137 and Co-60.for the scan measurements and the results are reported in Attachment 3.
,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 3 land siirvey 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. One potential area of elevated activity were detected and evaluated as shown in Attachment 3.
==
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. One investigation was 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 F85 10001 meets the release criteria of 10CFR20.1402.
Page 7 of 7 PFSS Summary Report F85 10001 Maps March 25, 2008 Survey Unit F8510001
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- SCALE METERS9 00 SWITCH YARD GAMMA SCANS ENLARGED DETAIL SACRAMENTO MUNICIPAL UTILITY DISTRICT F851000-M 7 FILE: 85 1000 IRC RAYM.4OND
0 00 Instrumentation March 25, 2008 Survey Unit F8510001
Table 2-1. Survey Unit Instrumentation Detector Detector Serial Instrument Model MDC No.
No.
HPGe N/A 05047773 Soil - 0.0902 pCi/g Cs-137 Soil - 0.0624 pCi/g Co-60 Soil - 3.6 pCi/g Cs-137 InSpector N/A 10054579 Soil - 2.6 pCi/g Co-60 Soil*- 2.68 pCi/g Co-60 Table 2-2. Investigation Criteria and DCGL Instrument Parameter Value Investigation Criteria -
Soil - 26.3 pCi/g Cs-137 Direct Soil - 6.3 pCi/g Co-60 All DCGLW 51.2 Cs-137 12.6 Co-60 All DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8510001 Investigation March 25, 2008 Survey Unit F851 0001
Table 3-1 Survey Unit Investigation IInvestigation.
DCGLemc Gd Investigation Initial Value Rest Elevated Area DCGLemc Investigation Unity ri Level Value Result Area (m2)
Factor Result (cpm)
Fraction Grd evl(cpm)
(cpm)
(cpm)
Fato 57 8200 8205 7000 N/A N/A N/A 7000 N/A S
U mDCGL=
SU Mean=
Sur-vey Unit Remainder 51.2 EMC Unity Sum N/A Grid 57 was resurveyed on 5/31/06 with 2350-1 #193700 and SPA-3 #404397 with a resulting logged value of 7000 cpm.
Three InSpector 1000 direct measurements were taken in the grid (Map F8510001-M8) with results less than MDA for both Cs-137 and Co-60.
The initial scan is considered a false positive and no furthers actions are required.
Page 2 of 2 Att. 3 Investigation F8510001 Data Assessment March 25, 2008 Survey Unit F8510001
crQ 0
00 C)1 00 F8510001 Quantile Plot Cs137 DCGL = 51.2 pCi/g U0.
5 C.)
0.100 -
0.090 -
0.080 -
0.070 -
0.060 -
0.050 -
0.040 -
0.030 -
0.020 -
0.010 -
0.000 -
0.058 Ip
.0 20 40 60 80 Percentile 100 Activity -
Median -
- -75th Percentile - -
- 50th Percentile
0 F8510001 Scatter Plot Cs137 DCGL = 51.2 pCIIg 1.20E-01
.109 1.O0E-01 0
o 0
0 0
0 6.00E..2-----------------------------------------.081 4.00E-02 0
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- - - - - - - - - - - - -013 O.OOE+00 i
Measurement Locations 0
Activity Average
"+3StDev-
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F8510001 Frequency Plot Cs1 37 DCGL = 51.2 pCi/g C:
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Bins - Upper End Value (pCi/g)
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