ML082620087

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Final Status Survey Summary Report, July 2, 2008, Chemical Storage Balcony Ceiling and Upper Walls Room 133, Survey Unit F8131222
ML082620087
Person / Time
Site: Rancho Seco
Issue date: 07/02/2008
From: Ellen Brown
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
References
MPC&D 08-064
Download: ML082620087 (24)
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Text

Rancho Seco Final Status Survey Summary Report July 2, 2008 Chemical Storage Balcony ceiling and upper walls Room 133 Survey Unit F8131222 Prepared By:

Z Date: 712 12Q0 FSS Engineer Reviewed By:

kL Date:

4(

Lead FSS Engineer Approved By:

Date:_

Dismantlement Superintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8131222, Chemical Storage Balcony ceiling and upper walls Room 133 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/1 00 cm2 and a maximum value of 5,720,000 dpm/100 cm2. 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 dpmr/100 cm 2. Direct measurements on the -20' elevation showed a mean gross activity level of 247,831 dpm/100 cm2 and a maximum value of 10,080,000 dpm/lO00 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 dpm/100 cm2. 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 dpmr/100 cm 2. Direct measurements on the +40' elevation showed a mean gross activity level of 3,288 dpm/l00 cm 2 and a maximum value of 24,781 dpm/100 cm2. 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 cm2. (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 90 m2 were scanned for approximately 33% 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 F8131222

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

F813 1222 Survey Unit:

Class:

SU Area (m2):

Evaluator:

DCGL (dpm/100 cm2)

Area Factor:

Design DCGLemc (dpm/100 cm2):

LBGR (dpm/100 cm2):

Design Sigma (dpm/100 cm2):

Type I Error:

Type II Error:

Predominant Nuclide:

Sample Area (m2):

Scan Area (m2):

Scan Coverage (%):

Zl-ot :

ZI.P :

Sign P:

Calculated Relative Shift:

Relative Shift Used:

N-Value:

Design N-Value+ 20%:

Design Min Samples N:

Grid Spacing L:

2 270.9 Erin L. Brown 43000 N/A N/A 21500 6935 0.05 0.05 Cs-137 19.35 90 33%

1.645 1.645 0.99865 3.1 3

11 14 14 4.3 Chemical Storage Balcony ceiling and upper walls Room 133 Structure Surface LTP Table5-4 Gross Activity DCGL Class 2 Class 2 Default 50% DCGL Class 2 Class 2 Uses 3.0 if Relative Shift is

Ž3 NUREG-1575 Table 5-5 Class 2 Class 2 Page 3 of 8 PFSS Summary Report F8131222

Survey Results:

A total of 16 direct measurements were made in F8131222. 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 1318 to 24396 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 Attachment 2.

Table 2. Direct Measurement Results Measurement ID Gross Activity (dpm/100 cm)

+

F8131222-CO001 BD F8131222-CO002BD F8131222-CO003BD F8131222-CO004BD F8131222-COOO5BD F8131222-CO006BD F8131222-CO007BD F8131222-CO008BD F8131222-CO009BD F8131222-CO01OBD F8131222-CO011 BD F8131222-CO01 2BD F8131222-CO01 3BD F8131222-CO014BD F8131222-CO01 5BD F8131222-CO01 6BD Mean:

Median:

Standard Deviation:

Range:

2260 2337 2381 2127 2690 2712 2646 2094 2293 2690 2745 2502 2480 2579 2094 2260 2431 2431 230 2094-2745 Page 4 of 8 FSS Summary Report F8131222

Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpmll00 cm 2)

F8131222C0001SM

-3.53 F8131222C0002SM 1.64 F8131222C0003SM

-0.95 F8131222C0004SM

-2.24 F8131222C0005SM

-2.24 F8131222C0006SM

-4.82 F8131222C0007SM 1.64 F8131222C0008SM

-0.95 F8131222C0009SM 1.64 F8131222C0010SM

-2.24 F8131222C0011SM 0.34 F8131222C0012SM

-2.24 F8131222C0013SM

-4.82 F8131222C0014SM

-0.95 F8131222C0015SM 0.34 F8131222C0016SM

-2.24 Mean:

-1.35 Median:

-1.59 Standard Deviation:

2.09 Range:

-4.82 to 1.64 Page 5-of 8 FSS Summary Report F8131222

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

Page 6 of 8 FSS Summary Report F8131222

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):

16 Median (dpm/100 cm2):

2431 Mean (dpm/100 cm2):

2431 Direct Measurement Standard Deviation 230 (dpm/100 cm 2):

Total Standard Deviation (dpm/100 cm2):

230 Based on samples and backgrounds.

Maximum (dpm/100 cm2):

2745 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:

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 F8131222

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 exceededl 0% 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 F8131222 meets the release criteria of 10CFR20.1402.

S Page 8 of 8 FSS Summary Report F8131222 Maps July 2, 2008 Survey Unit F8131222

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  • , HILL Instrumentation July 2, 2008 Survey Unit F8131222

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; 180733 43-98B; 148638 N/A 1680 M2350; 180733 43-94; 148620 N/A 1610 M2350; 175834 43-68B; 190482 909 2169 M2350; 203486 43-68B; 161400 909 2169 M2350; 203486 43-116-1B; 190173 N/A 6854 Tennelec; 0401171 N/A 5.9 dpm a, N/A 11.7 dpmr PI The MDC noted for the detector model 43-98B is for the 3" diameter piping and detector model 43-94 is for the 2" diameter piping which is the most conservative.

Table 2-2. Investigation Criteria and DCGL Value Param eterVa u C M (dpm/100 cm 2)

Investigation Criteria - Direct 43000 Investigation Criteria - Scan 43000 DCGLw 43000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8131222 Investigation July 2, 2008 Survey Unit F8131222 (none required)

Data Assessment IJuly 2, 2008 Survey Unit F8131222

CF8131222 Gross Activity Sample Results Quantile Plot oQ 0

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