ML090900771

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Final Status Survey Report for September 26, 2008, Demin Rc Storage Tank Pad, Survey Unit F8100042
ML090900771
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: ML090900771 (22)
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Rancho Seco Final Status Survey Summary Report September 26, 2008 Demin RC Storage Tank Pad Survey Unit F8100042 Prepared By: Dan A. Tallman ,Date: September 26, 2008 FSS Endineer Reviewed By: - -

  • f(1* (O9 Lead FSS Engineer Approved By: Date: 2, 0-0 Dismantlement Superintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8100042, Demin RC Storage Tank Pad Survey Unit

Description:

Operating History: This area commonly referred to as the Tank Farm, surrounded the tanks used to store radioactive liquids. The Demin RC Storage Tank 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 the Demin RC Storage Tank Pad using the HPGe detector and the ISOCS system. These measurements confirmed the presence of plant-derived radionuclides. Scan measurements of the Demin RC Storage tank showed a mean gross activity level of 987 dpm/1 00 cm 2 and a maximum value of 1,120 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 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 84 m2 were scanned for approximately 47% 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 F8100042

Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F810 Detain RC Storage Tank Pad Survey Unit: 0042 Structure Surface Class: 2 LTP Table 5-4 2 177.4 SU Area (mn ):

Evaluator: D.A.Tallman DCGL (dpm/1 00 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 2 73 Design Sigma (dpm/100 cm ):

Type I Error: 0.05 Type II Error: 0.05 Predominant Nuclide: Cs-137 Sample Area (M2): 12.6 Class 2 Scan Area (M ): 2 84 Scan Coverage (%): 47% Class 2 Zl_* : 1.645 1.645 Sign P: 0.99865 Calculated Relative Shift: 294.5 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 3.5 Class 2 Grid Spacin2 L:

Page 3 of 8 FSS Summary Report F8100042

Survey Results:

A total of 16 direct measurements were made in F8100042. 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 3810 to 17650 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 Activity (dpm/100 cm F8100042-CO001BD 4373 F8100042-CO002BD 4560 F8100042-CO003BD 36.93 F8100042-CO004BD 3641 F8100042-CO005BD 3470 F8100042-CO006BD 4082 F8100042-CO007BD 3890 F8100042-CO008BD 3294 F8100042-CO009BD 3756 F8100042-CO01 OBD 4274 F8100042-CO011 BD 3750 F8100042-CO012BD 3616 F8100042-CO013BD 3206 F8100042-CO014BD 3849 F8100042-CO015BD 3097 F8100042-CO016BD 2811 Mean: 3710 Median: 3722 Standard Deviation: 473 Range: 2811 -4560 Page 4 of 8 FSS Summary Report F8100042

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

F8100042C0001SM -0.95 F8100042C0002SM -2.24 F8100042C0003SM -3.53 F8100042C0004SM -6.11 F8100042C0005SM -0.95 F8100042C0006SM -3.53 F8100042C0007SM -0.95 F8100042C0008SM -4.82 F8100042C0009SM -3.53 F8100042C0010SM -3.53 F8100042C0011 SM -2.24 F8100042C0012SM -2.24 F8100042C001 3SM -4.82 F8100042C0014SM -4.82 F8100042C001 5SM -4.82 F8100042C0016SM 10.68 Mean: -2.4 Median: -3.53 Standard Deviation: 3.83 Ranqe: -6.11 to 10.68 Page 5 of 8 FSS Summary Report F8100042

Survey Unit Data Assessment:

The survey design required 16 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. However, since both values of sigma resulted in a relative shift greater than three (3), no additional samples were required.

Page 6 of 8 FSS Summary Report F8100042

Table 4. Data Assessment Results Survey Results Parameter Value Comment 2

Material Background Used (dpm/100 cm ): N/A Ambient Background Used (dpm/100 cm 2

): N/A Average Ambient BKG = 0 Actual Direct Measurements (N): 16 Median (dpm/100 cm 2): 3722 Mean (dpm/100 Cm2 ): 3710 Direct Measurement Standard Deviation 473 (dpm/100 cm 2):

Total Standard Deviation (dpm/100 cm 2): 473 Based on samples and backgrounds.

Maximum (dpm/100 cm 2 ): 4560 Material Type: N/A Background Subtract Not Applied Sign Test Final N Value: 16 S+ Value: 16 Critical Value: 11 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 Both values of sigma result in relative shift greater than three so no additional samples required Pass the Sign Test? Yes Reject the Null Hypothesis? Yes Does the Survey Unit Pass All Criteria? Yes Sufficient sample were taken Page 7 of 8 FSS Summary Report F8100042

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 6xceeded 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 F8100042 meets the release criteria of 10CFR20.1402.

Page 8 of 8 FSS Summary Report F8100042

Attachment 1 Maps September 26, 2008 Survey Unit F8100042

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Scale Feet Surlace Area Estimates 8J"=1'0 TANK FARM - DRCST PAD 00 concrete 176.1 r PLAN / ELEVATION VIEW steel Total 13mrr 1774ma Scale Meters

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  • 5muc SACRAMENTO MUNICIPAL MEASUREMENT LOCATIONS 0 1 2 3 UTILITY DISTRICT F8100042-M3 SHEET 2 of 2

Attachment 2 Instrumentation September 26, 2008 Survey Unit F8100042

Table 2-1. Survey Unit Instrumentation Instrument Detector MDC Static MDC Scan Model; Serial No. Model; Serial No. (dpm/100 cm2 ) (dpm/100 cm2 )

M2350;, 193700 43-68B; 160691 433 1033 M2350; 142499 43-37; 148502 N/A 616 Tennelec; 0401171 N/A 6 dpm a, 12 dpmI3 N/A Table 2-2. Investigation Criteria and DCGL Parameter Value VleC2 (dpm/100 cm 2 )

Investigation Criteria - Direct 43000 Investigation Criteria - Scan 43000 DCGLw 43000 DCGLEmc N/A Page 2 of 2 Att. 2 Instrumentation F8100042

Attachment 3 Investigation September 26, 2008 Survey Unit F8100042 (none required)

Page I of I Att. 3 Investigation F8100042

Attachment 4 Data Assessment September 26, 2008 Survey Unit F8100042

F8100042 Gross Activity Sample Results Quantile Plot 0.

DCGL = 43000 dpm/1 00cm2 5,000 4,500 4,000 3722 3,500 3,000 2,500 Ci2 2,000 1,500 1,000 500 C/) 0 0 20 40 60 80 100 Percentile

  • Direct Measurements (dpm/100cm2) - median - - - 75th Percentile .... 50th Percentile

CD F8100042 Gross Activity Sample. Results Scatter Plot DCGL = 43000 dpmlO00cmR 6000 -

  1. -5000 -- ---- ---------- - - ---- -- --- ------ -- -- -- --- 51 29 E 0 U 0 0 (42-0-o _i -- -. - 3710 CL 3°000 -

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