ML090900773

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Final Status Survey Summary Report for September, 26, 2008, Tank Farm Tritium Evaporator Pad, Survey Unit F8100044
ML090900773
Person / Time
Site: Rancho Seco
Issue date: 09/26/2008
From: Tallman D
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
Shared Package
ML090830613 List: ... further results
References
DPG 09-097
Download: ML090900773 (22)
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Rancho Seco Final Status Survey Summary Report September 26, 2008 Tank Farm Tritium Evaporator Pad Survey Unit F8100044 Prepared By: Dan A. Tallman Date:September 26, 2008 FSS Engineer Reviewed By:

Date:

Lead FSS Engineer Approved By: Z Date:

Dismantlement ýuperintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8100044, Tank Farm Tritium Evaporator Pad Survey Unit

Description:

Operating History: This area commonly referred to as the Tank Farm, surrounded the tanks used to store radioactive liquids. The Tritium Evaporator Pad resides within the boundaries of the Tank Farm and has been 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.

Site Characterization: Gamma scan measurements were made of Northeast quadrant of the Tank Farm, including the Tritium Evaporator Pad. These measurements confirmed the presence of plant-derived radionuclides. Scan measurements on the Tritium Evap Pad showed a mean gross activity level of 2,998 dpm/100 cm 2 and a maximum value of 3,329 dpm!100 cm. Based on the classification procedure (DSIP-0020) and levels of activity reported, the area was determined to be a Class 2 area.

Survey UnitDesign 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 54 m2 were scanned for approximately 36% coverage. Samples of removable contamination were collected at each direct measurement location. 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 8 FSS Summary Report F8100044

Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:

Survey Unit:

Class:

SU Area (m2):

Evaluator:

DCGL (dpm/100 cm 2):

Area Factor:

Design DCGLemc (dpm/100 cm2):

LBGR (dpm/100 cm 2):

Design Sigma (dpm/100 cm 2):

Type I Error:

Type II Error:

Predominant Nuclide:

Sample Area (m2):

Scan Area (M2):

Scan Coverage (%):

Sign P:

Calculated Relative Shift:

Relative Shift Used:

N-Value:

Design N-Value + 20%:

Design Min Samples N:

Grid Spacing L:

F810 Tank Farm Tritium Evaporator Pad Structure Surface LTP Table 5-4

.0044 2

148 D.A.Tallman 43000 N/A N/A 21500 167 0.05 0.05 Cs-137 10.5 54 36%

1.645 1.645 0.99865 128.7 3

11 14 14 3.2 Gross. Activity DCGL Class 2 Class 2 Default = 50% DCGL Class 2 Class 2 Uses 3.0 if Relative Shift is

>3 NUREG-1575 Table 5-5 Class 2 Class 2 Page 3 of 8 FSS Summary Report F8100044

Survey Results:

A total of 14 direct measurements were made in F8100044. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. None of the scan measurements indicated areas of elevated activity. Scan activity ranged from 5751 to 14591 dpm/1'00 cm 2, based on a surveyor efficiency of 0.5 and no background subtracted. Samples for removable surface activity were all less than 10% of the DCGL as shown in Table 3. Removable surface activity samples were counted for alpha activity and none was detected at the MDC shown in Table 2-1 of Attachment 2.

Table 2. Direct Measurement Results Measurement ID Gross Activit (dpm/100 cm F8100044-C0001BD F8100044-CO002BD F8100044-CO003BD F8100044-CO004BD F8100044-CO005BD F8100044-CO006BD F8100044-CO007BD F8100044-CO008BD F8100044-CO009BD F8100044-CO01OBD F8100044-C0011 BD F8100044-C0012BD F8100044-CO013BD F8100044-C0014BD Mean:

Median:

Standard Deviation:

Range:

2775 2775 2583 2983 2983 2490 2485 2199 2697 2697 2542 2646 2853 2609 2666 2671 209 2199-2983 Page 4 of 8 FSS Summary Report F8100044

Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2)

F8100044CO001SM

-6.11 F8100044C0002SM

-4.82 F8100044C0003SM

-4.82 F8100044C0004SM 1.64 F8100044C0005SM

-3.53 F8100044C0006SM

-3.53 F8100044C0007SM 0.34 F8100044C0008SM

-2.24 F8100044C0009SM

-2.24 F8100044CO010SM

-4.82 F8100044CO01ISM

-6.11 F8100044C0012SM

-2.24 F8100044C0013SM

-3.53 F8100044C0014SM 1.64 Mean:

-2.88 Median:

-3.53 Standard Deviation:

2.57 Range:

-6.11 to 1.64 Page 5 of 8 FSS Summary Report F8100044

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 4. 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 6 of 8 P FSS Summary Report F8100044

Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm 2):

Ambient Background Used (dpm/100 cm2):

Actual Direct Measurements (N):

Median (dpm/100 cm2):

Mean (dpm/100 cm 2):

Direct Measurement Standard Deviation (dpm/100 cm2):

Total Standard Deviation (dpm/100 cm 2):

Maximum (dpm/100 cm 2):

Material Type:

Sign Test Final N Value:

S+ Value:

Critical Value:

Sufficient Samples Collected:

Maximum Value < DCGL:

Median Value < DCGL:

Mean Value < DCGL:

Maximum Value < DCGLemc:

Total Standard Deviation <= Sigma:

Pass the Sign Test?

Reject the Null Hypothesis?

Does the Survey Unit Pass All Criteria?

N/A N/A 14 2671 2666 209 Average Ambient BKG 0

Based on samples and backgrounds.

Background Subtract Not Applied 209 2983 N/A 14 14 10 Yes Yes Yes Yes N/A Investigate Yes Yes Yes Class 2 No additional samples required Both values of sigma result in relative shift greater than three so no additional samples required Page 7 of 8 FSS Summary Report F8100044

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 2 structure 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. However, no additional samples were required. 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. No direct measurements exceeded the DCGL of 43000 dpm/100 cm2 and none of the removable surface activity measurements exceeded 10% of 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 F8100044 meets the release criteria of 10CFR20.1402.

Page 8 of 8 FSS Summary Report F8100044 Maps September 26, 2008 Survey Unit F8100044

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D RST PAD a,1:r H3 EVAP 7PAD WTPAd BWS.T DPAD Zone 3 Zone 1 TANK FARM - CONCRETE PADS GENERAL ARRANGEMENT PLAN VIEW F8100044-Mi SHEET 1. OF 2

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VERTICAL SURFACES VERTICAL SURFACES 00 Scale Meters SMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT TANK FARM - H3 EVAP PAD SCAN SURVEY LOCATION OVERVIEW F8100044-M3 SHEET 1 OF 3

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Instrumentation September 26, 2008 Survey Unit F8100044

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

Model; Serial No.

(dpm/100 cm 2 )

(dpm/100 cm 2 )

M2350; 193715 43-68B; 148630 433 1033 Tennelec; 0401171 N/A 6 dpm c, 12 dpmf3 N/A Table 2-2. Investigation Criteria and DCGL Value Parameter d

alue CM2)

(dpm/100 c2 Investigation Criteria - Direct 43000 Investigation Criteria - Scan 43000 DCGLW 43000 DCGLF.MC N/A Page 2 of 2 Att. 2 Instrumentation F8100044 Investigation September 26, 2008 Survey Unit F8100044 (none required)

Data Assessment September 26, 2008 Survey Unit F8100044

'-e F8100044 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/100cm2 3,500 3,000 2,500 1/2 1,000 2

1500 0

0 20 40 60 80 100 Percentile Direct Measurements Odpm/1OOcni2) median 75th Percentile....

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