ML090850549

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Final Status Survey Report for April 5, 2008, Rhut/Aux Boiler Pad Area, Survey Unit F8370001
ML090850549
Person / Time
Site: Rancho Seco
Issue date: 04/05/2008
From: Tallman D
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
Shared Package
ML090830613 List: ... further results
References
DPG 09-097
Download: ML090850549 (31)
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Rancho Seco Final Status Survey Summary Report April 5, 2008 RHUT/Aux Boiler Pad Area Survey Unit F8370001 Prepared By: Dan A. Tallman -_-Date: April 5, 2008 Reviewed Date:

Approved By: Date: 3 -

Dismantlement Sup rintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8370001, RHUT/Aux Boiler Pad Area Survey Unit

Description:

Operating History: The area surrounded the A and B Regenerant Hold Up Tanks. This area was used for the storage of radioactive material. The survey unit was expanded to include the foot prints of the historic Auxiliary Boiler pad and the Bulk Acid Storage pad.

Operating records and the HSA document several leaks/spills 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.

Initial soil sampling prior to remediation showed activity levels up to 140 pCi/g with both Cs-137 and Co-60 detected. These samples were sent for HTD analysis and formed the basis for the soil nuclide fraction.

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 4.09 pCi/g and a maximum value of 31.13 pCi/g. Based on the classification procedure (DSIP-0020) and initial levels of Cs- 137 reported, the area was determined to be a Class I 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. Direct measurement locations were determined using a random-start, fixed grid pattern and 1819 m 2 were scanned for 100% 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 F8370001

Table 1. Survey Unit Design Parameters Survey Design Parameter Value Comment Survey Area: F837 RHUT/Aux Boiler Pad Area Survey Unit: 0001 Open Land Area Class: 1 LTP Table 5-4 SU Area (m2): 1819 Evaluator: D.A.Tallman DCGL Cs137 surrogate (pCi/g): 51.2 Area Factor: 1.2 Class 1 Design DCGLemc (pCi/g): 61.9 Class 1 LBGR (pCi/g): 25.6 Default = 50% DCGL Design Sigma (pCi/g): 9.83 DTBD-06-001, Table 5-4D Type I Error: 0.05 Type II Error: 0.05 Nuclide: Cs137 Sample Area (m2): 121.3 Class 1 Total Area Scanned (m2): 1819 Scan Coverage (%): 100% Class 1 ZIa : 1.645 Zl-P : 1.645 Sign P: 0.99379 Calculated Relative Shift: 2.6 Relative Shift Used: 2.6 N-Value: 12 Design N-Value + 20%: 15 NUREG-1575 Table 5-5 Grid Spacing L: 11 Class 1 Page 3 of 7 FSS Summary Report F8370001

Survey Results:

A total of 18 direct measurements were made in F8370001. 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. ISOCS scan activity ranged from less than MDA to 2.35 E-01 pCi/g for Cs-137. MDA values are as indicated in Attachment 2. 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: 1 1.44B .1 Median: 5.33E-02 Standard Deviation:<, 1j1* !<* j* 2.69E-01 Range: 3.75E-02 to 9.OOE-01 F8370001SOOO1SS 4.52E-02 < 4.52E-02 F8370001S0002SS 7.03E-02 < 7.03E-02 F8370001S0003SS 6.53E-02 < 6.53E-02 F8370001S0004SS 5.86E-02 < 5.86E-02 F8370001S0005SS 4.33E-02 < 4.33E-02 F8370001S0006SS 5.99E-02 < 5.99E-02 F8370001S0007SS 5.25E-02 < 5.25E-02 F8370001A0008GD 9.OOE-01 < 9.00E-01 F8370001SO009SS 3.95E-02 < 3.95E-02 F8370001SOO1OSS 4.95E-02 < 4.95E-02 F8370001SOOllSS 3.75E-02 < 3.75E-02 F8370001S0012SS 4.64E-02 < 4.64E-02 F8370001S0013SS 5.40E-02 < 5.40E-02 F8370001S0014SS 4.99E-02 < 4.99E-02 F8370001A0015GD 8.65E-01 < 8.65E-01 F8370001S0016SS 5.70E-02 < 5.70E-02 F8370001S0017SS 4.23E-02 < 4.23E-02 F8370001S0018SS 6.01E-02 < 6.01E-02 Page 4 of 7 FSS Summary Report F8370001

Survey Unit Data Assessment:

The survey design required 18 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 F8370001

Table 3. Data Assessment Results Survey Results Parameter Value Comment Actual Direct Measurements (N): 18 Median (pCi/g): 5.33E-02 Mean (pCi/g)t 1.44E-01 Standard Deviation (pci/g): 2.69E-01 Maximum (pCi/g): 9.00E-01 Sign Test Final N Value: 18 S+ Value: 18 Critical Value: 12, Sufficient Samples Collected: Yes Maximum Value < DCGL: Yes Median Value < DCGL: Yes Mean Value < DCGL: Yes Maximum Value < DCGLemc: Yes Class 1 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 F8370001

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 1 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 1 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 F8370001 meets the release criteria of 10CFR20.1402.

Page 7 of 7 FSS Summary Report F8370001

Attachment 1 Maps April 5, 2008 Survey Unit F8370001

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Attachment 2 Instrumentation April 5, 2008 Survey Unit F8370001

Table 2-1. Survey Unit Instrumentation Detector Detector Serial Instrument Model MDC No.No.

HPGe N/A 05069128 Soil - 0.0703 pCi/g Cs-137 Soil - 0.0751 pCi/g Co-60 Asphalt - 0.810 pCi/g Cs-137 Inspector N/A 08051294 Asphalt - 0.306 pCi/g Co-60 Soil - 0.3 pCi/g Cs-137 ISOCS N/A 2983947 Soil - 0.1 pCi/g Co-60 Asphalt - 0.3 pCi/g Cs-137 Table 2-2. Investigation Criteria and DCGL Instrument Parameter Value Soil - 20 pCi/g Cs-137 ISOCS Investigation Criteria - Scan Soil - 5 pCi/g Co-60 Asphalt- 20 pCi/g Cs-137SUr, All DCGLw 51.2 Cs-137 12.6 Co-60 All DCGLEMC 61.95 Cs-137 15.37 Co-60 Page 2 of 2 Att. 2 Instrumentation F8370001

Attachment 3 Investigation April 5, 2008 Survey Unit F8370001 (none required)

Attachment 4 Data Assessment April 5, 2008 Survey Unit F8370001

F8370001 Quantile Plot Cs1 37 DCGL = 51.2 pCi/g 1.000 0.900 (D

0.800 04 0.700 0

0.600 0.

0.500 U 0.400 0.300 0.200 0.100 rIt 0.053 0.000 Cj) 0 20 40 60 80 100 Percentile I Activity - Median - - - 75th Percentile - - - - 50th Percentile I 00

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F8370001 Scatter Plot Cs137 DCGL = 51.2 pClIg 1.20E+00 1.OOE+00 -.0 O --. 0-----------------------------------------------

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Measurement Locations I o Activity - Average - - "+3StDev"- - "-3StDev i 00

0q CD F8370001 Frequency Plot Cs1 37 DCGL = 51.2 pCi/g 16 14

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Bins - Upper End Value (pCi/g) 00

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