ML090830322

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Final Status Survey Report for March 2, 2009 Tank Farm Nw Quadrant Survey Unit F8100021
ML090830322
Person / Time
Site: Rancho Seco
Issue date: 03/02/2009
From: Tallman D
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
Shared Package
ML090830613 List: ... further results
References
DPG 09-097, F8100021
Download: ML090830322 (21)
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Rancho Seco Final Status Survey Summary Report March 2, 2009 Tank Farm NW Quadrant Survey Unit F8100021 Prepared By: Dan A. Tallman Qz" - Date: March 2, 2009 FSS Engineer Reviewed By: . " L Date: B I Lead FSS Engineer Approved By: Date: C-1C' Dismantlement Stperintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8100021, Tank Farm NW Quadrant 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 1,940 pCi/g. Substantial remediation and dismantlement activities have impacted the survey unit. All the above ground tanks have been removed and a large percentage of buried piping has also been removed. During pipe removal activities, open trenches wer6 sampled using MARSSIM protocols to the extent practical, sampling the soil at various: depth intervals during excavation as well as the bottoms of the trench and the spoils piles. Gamma scan surveys of the various trench features were also performed typically using the 44-10. Based on the classification procedure (DSIP-0020) and levels of Cs-137 reported, the area was determined to be a Class 1 land area.

Survey Unit Design Information:

The Survey Unit Design Parameters are presented in Table 11below. 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 1618 m2 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 F8100021

Table 1. Survey Unit Design Parameters Survey Design Parameter Value Comment Survey Area: F810 Tank Farm NW Quadrant Survey Unit: 0021 Open Land Area Class: 1 LTP Table 5-4 SU Area (m 2 ): 1618 Evaluator: D.A.Tallman DCGL Cs137 surrogate (pCi/g): 51.2 Area Factor: 1.2 Class 1 Design DCGLemc (pCi/g): 63 Class 1 LBGR (pCi/g): 25.6 Default = 50% DCGL Design Sigma (pCi/g): 10.7 DTBD-06-001, Table 5-4B Type I Error: 0.05 Type II Error: 0.05 Nuclide: Cs137 Sample Area (m2): 100 Class 1 Total Area Scanned (m2): 1618 Scan Coverage (%): 100% Class 1 Z1 ~ : 1.645 Z1 ~ : 1.645 Sign P: 0.97725 Calculated Relative Shift: 2.3 Relative Shift Used: 2.3 Uses 3.0 if Rel Shift >3 N-Value: 12 Design N-Value + 20%: 15 NUREG-1575 Table 5-5 Grid Spacing L: 10.4 Class 1 Page 3 of 7 FSS Summary Report F8100021

Survey Results:

A total of 17 direct measurements were made in F8100021. The results including mean, median, standard deviation and range are shown in Table 2. All of the direct measurements were less than the DCGL. Eleven (11) of the scan measurements indicated areas of elevated activity, with an observed range of 4992 - 20292 cpm with the 2350-1/44-10 instrument - detector combination. Soil samples and Direct Measurements were counted to the MDC shown in Table 2-1 of Attachment 2. :

Table 2. Direct Measurement Results (all activity values in pCi/g)

Page 4 of 7 FSS Summary Report F8100021

Survey Unit Data Assessment:

The survey design required 17 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 F8100021

Table 3. Data Assessment Results Survey Results Parameter Value Comment Actual Direct Measurements (N): 17 Median (pCi/g): 3.09E-01 Mean (pCi/g): 3.5 1E-01 Standard Deviation (pci/g): 2.3 1E-01 Maximum (pCi/g): 8.60E-01 Sign Test Final N Value: 17 S+ Value: 17 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 F8100021

Survey Unit Investigations and Results:

Eleven (11) investigations (scan grids 1, 5, 9, 25, 28, 44, 51 ý,55, 66, 79, & 193) were required for the scan measurements and the results are reported in Attachment 3. The EMC unity rule was not exceeded as shown in Table 3-1.

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. Potential areas of elevated activity were detected and evaluated as shown in Attachment 3. Therefore the EMC criterion was met.

==

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. Eleven (11) 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 thatsurvey unit F8100021 meets the release criteria of 10CFR20.1402.

Page 7 of 7 FSS Summary Report F8100021

Attachment 1 Maps March 2, 2009 Survey Unit F8100021

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Asph I It SCALE METERS

-171 0 5 00 TANK FARM - ZONE 2 Surfaci Area EslikaIW o) Sol 1539 mn GENERAL ARRANGEMENT PLAN VIEW Asphalt t9 SACPALMENTO MUNICIPAL SURFACE AREA ESTIMATE 1618 m.

Total UTILITY DISTRiCT F8100021-Mi SHEET 1 ofi

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C0 TANK FARM - ZONE 2 SCAUEMETERS SOIL SAMPLE

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..... Road GS017 GS016 GS023 GS022 GS012 GS026 GS027 GS028 CD GS032 GS033 1T33

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C) DISCRETE PARTICLE GAMMA SCAN SCALE METERS MEASUREMENT LOCATIONS SARAMENTO (MU!I'WDALt 0 S 10 T>OTRICT F8100021-M3 Sl EET2 of2

Attachment 2 Instrumentation March 2, 2009 Survey Unit F8100021

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

2350-1 #256101

  1. 193700 44-10 #171374 5-6 pCi/g. 1, 2
  1. 193715 #171992
  1. 203481 Inspector N/A 08051294 Asphalt - 0.901 pCi/g Co-60 Asphalt - 0.860 pCi/g Cs- 137 HPGe N/A 05069128 Soil - 0.102 pCi/g Co-60 Soil - 0.074 pCi/g Cs-137 Ludlum 2350-1 with Nal Detector MDA /investigation level sufficientto detect a I uCi discrete Co60 particle as detailed in "Discrete Particle Detection Using the Ludlum 2350-Im and 5.08 by 5.08 Nal detectors" RFD 3/27/07 2 Ludlum 2350-1 w/ Nal detector (44-10/SPA-3) MDA for distributed soil activity 6 pCi/g.

Table 2-2. Investigation Criteria an'd DCGL Instrument Parameter Value 2351/44-10 Investigation Criteria - Scan 7,024 - 10068 cpm' Inspector Investigation Criteria - Direct 63 ý-pCi/g Cs-137(sur.)

HPGe Investigation Criteria - Direct Soil - 63 pCi/g Cs-137(sur.)

All DCGLw 51.2 Cs-137 12.6 Co-60 All DCGLEMc 63 - pCi/g Cs-137(sur.)

'Depending on Instrument set used, 2350-1/44-10 Investigation Level calculated IAW DSIP-0510 (encl. 8.6)

Page 2 of 2 Att. 2 Instrumentation F8100021

Attachment 3 Investigation March 2, 2009 Survey Unit F8100021

Table 3-1 Survey Unit Investigation Value nvestiationslevateiAreaDCGLemc Investigation Initial Value Investigation Elevated Area DCGtemc Unity Grid Level (cpm) (cpm) Result1 Area (i 2) Factor DCGLec Result (pCi/g) Ut 19,79 Rsult(p~/g)Fraction 001 10,068 19,789 24.2 (c) N/A" N/A N/A 24.2 (c) N/A 005 8,340 8,340 7767 (a) N/A N/A N/A 7767 (a) N/A 009 8,340 8,798 < 1.27 (b) N/A N/A N/A < 1.27 (b) N/A 025 8,340 9,310 1.4 (c) N/A N/A N/A 1.4 (c) N/A 028 8,340 9,817 0.54 (c) N/A N/A N/A 0.54 (c) N/A 044 10,068 14,379 6.7 (c) 2 N/A N/A N/A 6.7 (c) 2 N/A 051 10,068 10,568 8360 (a) N/A N/A N/A 8360 (a) N/A 055 8,340 .20,282 5.3 (c) 3 N/A N/A N/A 5.3 (c) 3 N/A 066 10,068 11,892 5.95 (c) N/A N/A N/A 5.95 (c) N/A 079 7,025 8,236 0.43 (c) N/A N/A N/A 0.43 (c) N/A 193 10,068 10,276 <-1.12 (b) N/A N/A N/A < 1.12 (b) N/A Survey Unit Remainder DCGL = SU Mean = N/A 51.2

" (a)= static count 44-10, (b)= InSpector 1000 (pCi/g), (c)= HPGe (pCi/g) 2 rock from "scree" isolated- counted, 63 pCi Co60 3a rock from "scree"isolated - counted, 93 pCi Co60 EMC Unity Sum N/A Page 2 of 2 Att. 3 Investigation F8100021

Attachment 4 Data Assessment March 2, 2009 Survey Unit F8100021

F8100021 Quantile Plot Cs137 DCGL = 51.2 pCi/g 1.000 0.900 0.800 0.700 U 0.600 0.500 U 0.400 0.300 0.309 0.200 0.100 0.000 0 20 40 60 80 100 Percentile

  • Activity - Median -- - 75th Percentile ... 50th Percentile 00

0 A

F8100021 Scatter Plot Cs137 DCGL = 51.2 pClIg 1.20E+00 1.0OE+00- -- - 1 8.00E-01

= 6.00E-01 2- 0 4.00E-1 0 0 0 6 .0012+00 -

-2.,0E-01 0 cj*

. .. .. . .. . . . . . . . . . . . . .0.341 r4 -4.00E-01

-6,00E-01 i 1 Measurement Locations I 0 Activty - Averaqe - - "+3StDev - - "-3StDev"i Or1 00 0

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F8100021 Frequency Plot Cs1 37 DCGL = 51.2 pCi/g 9_

8-

)7 a) 6-

-5

>3 (2

o0 C/2 ci, / QV Co.

N N Bins - Upper End Value (pCi/g)

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