ML090900773
| 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:
|
| References | |
| DPG 09-097 | |
| Download: ML090900773 (22) | |
Text
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: F810 Tank Farm Tritium Evaporator Pad Survey Unit: .0044 Structure Surface Class: 2 LTP Table 5-4 SU Area (m2): 148 Evaluator: D.A.Tallman DCGL (dpm/100 cm 2): 43000 Gross. Activity DCGL Area Factor: N/A Class 2 Design DCGLemc N/A Class 2 (dpm/100 cm 2):
LBGR (dpm/100 cm 2): 21500 Default = 50% DCGL Design Sigma (dpm/100 cm 2): 167 Type I Error: 0.05 Type II Error: 0.05 Predominant Nuclide: Cs-137 Sample Area (m2): 10.5 Class 2 Scan Area (M2): 54 Scan Coverage (%): 36% Class 2 1.645 1.645 Sign P: 0.99865 Calculated Relative Shift: 128.7 Relative Shift Used: 3 Uses 3.0 if Relative Shift is
>3 N-Value: 11 Design N-Value + 20%: 14 NUREG-1575 Table 5-5 Design Min Samples N: 14 Class 2 Grid Spacing L: 3.2 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 2775 F8100044-CO002BD 2775 F8100044-CO003BD 2583 F8100044-CO004BD 2983 F8100044-CO005BD 2983 F8100044-CO006BD 2490 F8100044-CO007BD 2485 F8100044-CO008BD 2199 F8100044-CO009BD 2697 F8100044-CO01OBD 2697 F8100044-C0011 BD 2542 F8100044-C0012BD 2646 F8100044-CO013BD 2853 F8100044-C0014BD 2609 Mean: 2666 Median: 2671 Standard Deviation: 209 Range: 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 2 (dpm/100 cm ): N/A Ambient Background Used (dpm/100 cm 2 ): N/A Average Ambient BKG 0 Actual Direct Measurements (N): 14 Median (dpm/100 cm 2 ): 2671 Mean (dpm/100 2 cm ): 2666 Direct Measurement Standard Deviation 209 (dpm/100 cm 2 ):
Total Standard Deviation (dpm/100 cm 2 ): 209 Based on samples and backgrounds.
Maximum (dpm/100 cm 2 ): 2983 Material Type: N/A Background Subtract Not Applied 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 2 Total Standard Deviation <= Sigma: Investigate No additional samples required Pass the Sign Test? Yes Reject the Null Hypothesis? Yes Does the Survey Unit Pass All Criteria? Yes 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 cm 2 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
Attachment 1 Maps September 26, 2008 Survey Unit F8100044
(tD D RST PAD a,1:r H3 EVAP 7PAD WTPAd BWS.T DPAD Zone 3 Zone 1 IT~J TANK FARM - CONCRETE PADS GENERAL ARRANGEMENT
- 14. PLAN VIEW F8100044-Mi SHEET 1. OF 2
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H3 FVAP PAfl 00 Scale Feet Surface Area Estimates 81"
= 1':0" TANK FARM - H3 EVAP PAD Concrete 143m2 PLAN / ELEVATION VIEW Steel 5sm Scale Meters Total 148In
- smu SACRAMENTO MUNICIPAL SURFACE AREA ESTIMATE 0 1 2 3 UTILITY DISTRICT F8100044-Mi SHEET 2 OF 2
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___$D 00 TANK FARM - H3 EVAP PAD BETA DIRECT MEASUREMENT SMUD RANDOM START LOCATION SACRAMENTO MUNICIPAL UTILITY DISTRICT F81 00044-M2 4 2-_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
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14 Row relocated one meter east H3 EVAP PAD 00 00 Scale Feet TANK FARM - H3 EVAP PAD BETA DIRECT Scale Meters 0*SMUn SACRAMENTO MUNICIPAL MEASUREMENT LOCATIONS 0 1 2 3 UTILITY DISTRICT F8100044-M2 SHEET 2 OF 2
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VERTICAL SURFACES VERTICAL SURFACES 00 Scale Meters TANK FARM - H3 EVAP PAD SCAN SURVEY SMUD LOCATION OVERVIEW SACRAMENTO MUNICIPAL UTILITY DISTRICT F8100044-M3 SHEET 1 OF 3
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00 TANK FARM - H3 EVAP PAD BETA SCAN MEASUREMENT 4ý-
- SMUG LOCATION DETAIL SACRAMENTO MUNICIPAL UTILITY DISTRICT F8100044-M3 SHEET 2 OF.3 -
Attachment 2 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 dpmc, 12 dpmf3 N/A Table 2-2. Investigation Criteria and DCGL Value Parameter d (dpm/100 c2 2 )
alueCM Investigation Criteria - Direct 43000 Investigation Criteria - Scan 43000 DCGLW 43000 DCGLF.MC N/A Page 2 of 2 Att. 2 Instrumentation F8100044
Attachment 3 Investigation September 26, 2008 Survey Unit F8100044 (none required)
Attachment 4 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 .... 50th Percentile
CD o IF8100044 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpmll00cm=
3500 .
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- V- V- Tw 0000 C3 0 0 a a 0 0 0 0 a U U U U U U U U U U U U U U Measurement Locations
- - ) o ~Gross Activity '-- Average.- "+3StDev" "-3StDev"
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F8100044 Gross Activity Frequency Plot DC G L = 43000 dpm/1 00cm" 4-0 C 3-
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