ML091000382

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Final Status Survey Summary Report 10/08/08, +20' Aux Steam Support, Survey Unit F8132134
ML091000382
Person / Time
Site: Rancho Seco
Issue date: 10/08/2008
From: Frank G
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
Shared Package
ML090830613 List: ... further results
References
DPG 09-097, F8132134
Download: ML091000382 (19)
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Rancho Seco Final Status Survey Summary Report October 8, 2008

+20' Aux Steam Support Survey Unit F8132134 Prepared B Date:

FSS Engineer Reviewed By..-ýO A I* L:J.-Date: 6(7 Lead FSS Engineer Approved By:__________ Date: -

Dismantlement Superintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8132134, +20' Aux Steam Support 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 cm 2 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/100 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 dpmr/100 cm 2. Direct measurements on the grade elevation showed a mean gross activity level of 373,758 dpm/1 00 cm 2 and a maximum value of 5,800,000 dpm/1 00 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 cm 2. Direct measurements on the +40' elevation showed a mean gross activity level of 3,288 dpm/100 cm2 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/100 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 2.25 m2 were scanned for 100% 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 F8132134

Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F813 +20' Aux Steam Support Survey Unit: 2134 Structure Surface Class: 1 LTP Table 5-4 SU Area (m2): 2.25 Evaluator: Gary Frank DCGL (dpm/100 cm'): 43000 Gross Activity DCGL Area Factor: 82.6 Class 1 Design DCGLemc 3551800 Class 1 (dpm/100 cm 2):

LBGR (dpm/100 cm 2): 21500 Default = 50% DCGL Design Sigma (dpm/100 cm 2): 342 Type I Error: 0.05 Type II Error: 0.05 Predominant Nuclide: Cs-137 Sample Area (m2): 0.16 Class 1 Scan Area 2 (M ): 2.25 Scan Coverage (%): 100% Class 1 Zl-, : 1.645 Zl-Pl : 1.645 Sign P: 0.99865 Calculated Relative Shift: 62.9 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 1 Grid Spacing L: 0.4 Class I Page 3 of 8 FSS Summary Report F8132134

Survey Results:

A total of 15 direct measurements were made in F8132134. 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 19124 to 30796 dpm/100 cm', 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 F8132134-COOOIBD 3455 F8132134-CO002BD 18674 F81321347-CO003BD 22191 F8132134-CO004BD 6759 F8132134-CO005BD 8575 F8132134-CO006BD 7319 F8132134-CO007BD 4388 F8132134-CO008BD 3688 F8132134-CO009BD 4943 F8132134-CO01OBD 2376 F8132134-CO011BD 2355 F8132134-CO012BD 2620 F8132134-CO013BD 2334 F8132134'CO014BD 2122 F8132134-CO015BD 2205 Mean: 6267 Median: 3688 Standard Deviation: 6135 Range: 2122 - 22191 Page 4 of 8 FSS Summary Report F8132134

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

F8132134C0001 SM 1 F8132134C0002SM 30.7 F8132134C0003SM 41.03 F8132134C0004SM 4.87 F8132134C0005SM 4.87 F8132134C0006SM 7.46 F8132134C0007SM 3.58 F8132134C0008SM .2.29 F8132134C0009SM 10.04 F8132134C0010SM 1 F8132134C0011SM 3.58 F8132134C0012SM 8.75 F8132134C0013SM 3.58 F8132134C0014SM 1 F8132134C0015SM 11.33 Mean: 9.01 Median: 4.87 Standard Deviation: 11.54 Range: I to 41.03 Page 5 of 8 FSS Summary Report F8132134

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 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 FSS Summary Report F8132134

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 2

Median (dpm/100 cm ): 3688 2

Mean (dpm/1 00 cm ): 6267 Direct Measurement Standard Deviation 6135 (dpm/100 cm 2):

Total Standard Deviation (dpm/100 cm2 ): 6135 Based on samples and backgrounds.

Maximum (dpm/100 cm 2): 22191 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: Yes Class 1 Total Standard Deviation <= Sigma: Investigate All values <DCGLw Pass the Sign Test? Yes Reject the Null Hypothesis? Yes Does the Survey Unit Pass All Criteria? Investigate Survey Unit Passes Page 7 of 8 FSS Summary Report F8132134

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, the ALARA criterion has been met.

Changes in Initial Survey Unit Assumptions:

The survey unit was designed as a Class 1 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. 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. 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 F8132134 meets the release criteria of 10CFR20.1402.

Page 8 of 8 FSS Summary Report F8132134

Attachment 1 Maps October 8, 2008 Survey Unit F8132134

0 0

1 LJ L Location of 20'Auxiliary Steam Support inside the Industrial Area F8132134-M1, Auxiliary.Building 20' Auxiliary Steam Support

Auxiliary Building Exterior Class 1 20' Auxiliary Steam Support Beta Scans 0

75 70 65 60 55 50 45 40

-e cj~

35 30 25 20" 15 10

..... I .... I .... I .... .... I5.... I.... I .... I .... I .... ... I .... I0.... I .... I .... I. ... I .... I .... I .... I .... I .... I ....

5 M0 15 20 25 30 35 40 45 50 55 R0 65 70 .75 80 85 90 95 W0 105 oI1 00 F8132134-M2

Auxiliary Building Exterior Class 1 (D 20' Auxiliary Steam Support Beta Directs

ý-o 75" 70" 65-60-55-50 "

45-40-35-30-25-20-15-10-5-

..... I .... I .... I .... I.... I .... I .... I .... I .... I.... I .... I.. I .... I .... I .... I .... I.... I .... I .... I .... I .... I ....

5 10 15 20 25 30 3S 40 45 50 55 60 65 TO 75 80 85 90 95 M00 105 00 F8132134-M3

Attachment 2 Instrumentation October 8, 2008 Survey Unit F8132134

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; 193715 43-68B; 148630 433 1033 M2350; 193715 43-116-1B; 256007 796 3258 Tennelec; 0401171 N/A 5 dpm at,10 dpm f3 N/A Table 2-2. Investigation Criteria and DCGL Value Param eterVa (dpm/100u cm 2)

CM Investigation Criteria - Direct 3551800 Investigation Criteria - Scan 3551800 DCGLw 43000 DCGLEMC 35'51800 Page 2 of 2 Att. 2 Instrumentation F8132134

Attachment 3 Investigation October 8, 2008 Survey Unit F8132134 (none required)

Attachment 4 Data Assessment October 8, 2008 Survey Unit F8132134

F8132134 Gross Activity Sample Results Quantile Plot t') 2 0 DCGL = 43000 dpm/1 00cm 25,000 20,000 15,000 tz)

I 4-10,000 I

0n En 5,000 3688 CD1 0

0 20 40 60 80 100 Percentile 00 I

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

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F81 32134 Gross Activity Sample Results Scatter Plot DCGL =43000 dpmlIOcmI 30000 25000 - -- --- -- --- - - - - - - - - - - - -I 24672 0

C 20000 E 0 o 15000 E 10000 6267 S 5000 o 0 0 0 0 0 0 0

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F81 32134 Gross Activity Frequency Plot 2

DCGL = 43000 dpm/1 00cm 10 9

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6 LL C 5 0

00 4

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Uj 1 0

0) q4 oo Bins - Upper End Value (dpm/1 00cm2)

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