ML082620084

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Final Status Survey Summary Report, July 15, 2008, Room 117 West of Column P 0 of AB, Survey Unit F8131041
ML082620084
Person / Time
Site: Rancho Seco
Issue date: 07/15/2008
From: Ellen Brown
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
References
F8131041, MPC&D 08-064
Download: ML082620084 (26)
v • d • e


Text

Rancho Seco Final Status Survey Summary Report.

July 15, 2008 Room 117 West of Column "P" 0' of AB Survey Unit F8131041 Prepared By: 6'&,71

/

,yV-Date: 2//2 FSS Engineer Reviewed By Date:

(? l 7_o Lead FSS Engineer Approved By:

Date:_________

Dismantlement Superintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8131041, Room 117 West of Column "P" 0' of AB Survey Unit

Description:

Operating History: The reinforced concrete structure contained the RadWaste processing and supporting systems. The building contained six main elevations. Residual radioactive material was known to be present on all levels of the interior of the building.

Operating records and the HSA document several events with the potential for a release of radioactivity inside this structure. One report documented contamination of the auxiliary building roof. The roof was later replaced.

Site Characterization: Direct measurements were made of each of the interior elevation surfaces as well as the exterior surfaces of the structure. These measurements confirmed the presence of plant-derived radionuclides. Direct measurements on the -47' elevation showed a mean gross activity level of 320,071. dpm/100 cm2 and a maximum value of 5,720,000 dpm/100 cm 2. Direct measurements on the -29' elevation showed a mean gross activity level of 544,756 dpm/100 cm 2 and a maximum value of 11,370,000 dpm/1 00 cm 2. Direct measurements on the -20' elevation showed a mean gross activity level of 247,831 dpm/100 cm 2 and a maximum value of 10,080,000 dpm/100 cm 2. Direct measurements on the grade elevation showed a mean gross activity level of 373,758 dpm/100 cm 2 and a maximum value of 5,800,000 dpmr/100 cm 2. Direct measurements on the +20' elevation showed a mean gross activity level of 85,408 dpm/100 cm 2 and a maximum value of 1,900,000 dpm/100 cm2. Direct, measurements on the +40' elevation showed a mean gross activity level of 3,288 dpm/l100 cm 2 and a maximum value of 24,781 dpm/100 cm 2. Direct measurements on the building exterior, including the mezzanine roof, showed a mean gross activity level of 1,897 dpm/l 00 cm 2 and a maximum value of 2,990 dpm/100 cm 2. (The roof had been replaced prior to the classification survey.) Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the interior of the auxiliary building was determined to be a Class 1, 2 area and the exterior was a Class 2,3.

HSA Events: HSA Report pg. 63.

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 186 m2 were scanned for approximately 26% 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 F8131041

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

F813 Survey Unit:

Class:

SU Area (m2):

Evaluator:

DCGL (dpm/O00 cm2):

Area Factor:

Design DCGLemc (dpm/100 cm 2):

LBGR (dpm/100 cm 2):

Design Sigma (dpm/100 cm 2):

Type I Error:

Type II Error:

Predominant Nuclide:

Sample Area (m):

Scan Area (in2):

Scan Coverage (%):

Zip:

Sign P:

Calculated Relative Shift:

Relative Shift Used:

N-Value:

Design N-Value + 20%:

Design Min Samples N:

Grid Spacing L:

1041 2

716 Erin L. Brown 43000 N/A N/A 21500 6935 0.05 0.05 Cs-137 51 186 26%

1.645 1.645 0.99865 3.1 3

11 14 14 7.1 Room 117 West of Column "P" 0' of AB Structure Surface LTP Table 5-4 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 F8131041

Survey Results:

A total of 15 direct measurements were made in F8131041. 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. ISOCS gamma scan measurements were performed in fourteen locations as shown in Attachment 1. Co-60 or Cs-137 were not identified above the MDC. Scan activity ranged from 853 to 17846 dpm/100 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.

Table 2. Direct Measurement Results Measurement ID Gross Activity (dpm/100 cm F8131041-CO001 BD F8131041 -C0002BD F8131041 -CO003BD F8131041-CO004BD F8131041-C0005BD F8131041 -C0006BD F8131041 -C0007BD F8131041 -C0008BD F8131041 -CO009BD F8131041--Co01OBD F8131041-CO011BD F8131041--Co012BD F8131041 -Co01 3BD F8131041--Co014BD F8131041--Co015BD Mean:

Median:

Standard Deviation:

Ranae:

2403 2249 2568 2436 2723 2612 2491 1400 2778 2524 2701 2767 2778 2723

.2866 2535 2612 357 1400-2866 Page 4 of 8 FSS Summary Report F8131041

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

F8131041 C0001 SM 4.22 F8131041C0002SM

-0.95 F8131041 CO003SM

-4.82 F8131041 C0004SM

-0.95 F8131041 C0005SM

-2.24 F8131041 C0006SM

-0.95 F8131041C0007SM 0.34 F8131041 C0008SM

-0.95 F8131041 C0009SM

-3.53 F8131041CO010SM

-3.53 F8131041 CON I SM

-3.53 F8131041C0012SM

-3.53 F8131041C0013SM

-2.24 F8131041COO14SM

-3.53 F8131041 C0015SM

-3.53 Mean:

-1.98 Median:

-2.24 Standard Deviation:

2.25 Range:

-4.82 to 4.22 Page 5 of 8 FSS Summary Report F8131041

Survey Unit Data Assessment:

The survey design required 15 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 less than the design standard deviation so no additional samples were required.

Page 6 of 8 FSS Summary Report F8131041

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

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

N/A Average Ambient BKG = 0 Actual Direct Measurements (N):

15 Median (dpm/100 cm 2):

2612 Mean (dpim/100 cm 2):

2535 Direct Measurement Standard Deviation 357 (dpm/100 cm 2):

Total Standard Deviation (dpm/100 cm2):

357 Based on samples and backgrounds.

Maximum (dpm/100 cm 2):

2866 Material Type:

N/A Background Subtract Not Applied Sign Test Final N Value:

15 S+ Value:

15 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:

Yes Pass the Sign Test?

Yes Reject the Null Hypothesis?

Yes Does the Survey Unit Pass All Criteria?

Yes Page 7 of 8 FSS Summary Report F8131041

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), 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 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 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 F8131041 meets the release criteria of.10CFR20.1402.

Page 8 of 8 FSS Summary Report F8131041 Maps July 15, 2008 Survey Unit F8131041

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

Model; Serial No.

(dpm/100 cm2 )

(dpm/100 cm 2 )

M2350; 180733 43-98B; 148638 N/A 2520 M2350; 180733 43-94B; 148620 N/A 1030 M2350; 203486 43-68B; 190476 912 2176 M2350; 203486 43-116-1B; 190173 N/A 3258 M2350; 180733 43-111B; 148641 N/A 2230 906 Co-60 ISOCS 1983,920 N/A 10 Co-60 1230 Cs-137 2210 Co-60 Inspector 10054579 N/A 2200 Co-60 2200 Cs-137 Tennelec; 0401171 N/A 5.9 dpm a, N/A 11.7 dpmr]3 The scan and static MDC's provided represent the most conservative MDC value for the survey conducted.

Table 2-2. Investigation Criteria and DCGL Value Parameter (dpm/100 cm 2)

Investigation Criteria - Direct 43000 Investigation Criteria - Scan 43000 DCGLw 43000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8131041 Investigation July 15, 2008 Survey Unit F8131041 (none required)

Data Assessment July 15, 2008 Survey Unit F8131041

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F8131041 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/1 00cm 2 I.

3 3,500 3,000 2,500 2,000 1,500 1,000 2612 500-0 0

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I Direct Measurements (dpm/100cm2) -

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