ML091000377

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Final Status Survey Summary Report 10/02/08, the Walls and Ceiling of the Ventilation Room 211 and the Duct Room 208, Survey Unit F8131372
ML091000377
Person / Time
Site: Rancho Seco
Issue date: 10/02/2008
From: Stein M
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
Shared Package
ML090830613 List: ... further results
References
DPG 09-097, F8131372
Download: ML091000377 (26)
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Text

Rancho Seco Final Status Survey Summary Report October 2, 2008 The Walls and Ceiling of the Ventilation Room 211 and the Duct Room 208 Survey Unit F8131372 Prepared By:

Date:

/101O/4&

00 FSS Engineer Reviewed By."

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Date:

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Dismantlement Suerintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8131372, The Walls and Ceiling of the Ventilation Room 211 and the Duct Room 208 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 dpmr/100 cm 2. Direct measurements on the -29' elevation showed a mean gross activity level of 544,756 dpm/100 cm2 and a maximum value of 11,370,000 dpm/100 cm2. 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/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 dpm/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/1 00 cm 2. 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/100 cm2 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. The walls and ceiling of the Ventilation Equipment Room 211 and the Duct Room 208 were determined to be a Class 2.

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 215 m2 were scanned for approximately 27% 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 F8131372

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

F813 Survey Unit:

Class:

SU Area (m2):

Evaluator:

DCGL (dpm/100 cm 2):

Area Factor:

Design DCGLemc (dpm/ 100 cm 2);

LBGR (dpm/100 cm 2):

Design Sigma (dpm/100 cm2):

Type I Error:

Type II Error:

Predominant Nuclide:

Sample Area (m2):

Scan Area (m2)

Scan Coverage (%):

Zl-,, :

Sign P:

Calculated Relative Shift:

Relative Shift Used:

1372 2

811 Michael Stein 43000 N/A N/A 21500 5461 0.05 0.05 Cs-137 57.9 215 27%

1.645 1.645 0.99865 3.9 3

The Walls and Ceiling of the Ventilation Room 211 and the Duct Room 208 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 N-Value:

Design N-Value + 20%:

Design Min Samples N:

Grid Spacing L:

11 14 14 7.6 NUREG-1575 Table 5-5 Class 2 Class 2 I

Page 3 of 8 FSS Summary Report F8131372

Survey Results:

A total of 14 direct measurements were made in F8131372. 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 2,201 to 6,672 dpm/100 cm2, 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 )

F8131372-CO001 BD F8131372-CO002BD F8131372-CO003BD F8131372-CO004BD F831 372-COOO5BD F8131372-CO006BD F8131372-CO007BD F8131372-CO008BD F8131372-CO009BD F8131372-CO01 OBD F8131372-CO01 I BD F8131372-CO012BD F8131372-CO01 3BD F8131372-CO014BD Mean:

Median:

Standard Deviation:

Range:

1354 1691 1795 1769 1758 1359 1489 1572 1686 1634 1235 1852 1613 1639 1603 1637 184 1235-1852 Page 4 of 8 FSS Summary Report F8131372

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

F8131372C0001 SM F8131372C0002SM F8131372C0003SM F8131372C0004SM F8131372C0005SM F8131372C0006SM F8131372C0007SM F8131372C0008SM F8131372C0009SM F8131372C0010SM F8131372C0011SM F8131372C0012SM F8131372C0013SM F8131372C0014SM Mean:

Median:

Standard Deviation:

Ranue:

2.29 1

11

-0.29

-1.58 24.24 2.29 2.29 1

-0.29 2.29 7.46

-1.58 2.94 1

6.52

-1.58 to 24.24 Page 5 of 8 FSS Summary Report F8131372

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

Page 6 of 8 FSS Summary Report F8131372

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

N/A Ambient Background Used (dpm/O00 cm 2):

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

14 Median (dpm/100 cm 2):

1637 Mean (dpm/100 cm 2):

1603 Direct Measurement Standard Deviation 184 (dpm/100 cm 2):

Total Standard Deviation (dpm/100 cm 2):

184 Based on samples and backgrounds.

Maximum (dpm/O00 cm 2):

1852 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:

Yes Pass the Sign Test?

Yes Reject the Null Hypothesis?

Yes Does the Survey Unit Pass All Criteria?

Yes I Page 7 of 8 P FSS Summary Report F8131372

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 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 cm2 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 F8131372 meets the release criteria of 10CFR20.1402.

Page 8 of 8 FSS Summary Report F8131372 Maps October 2, 2008 Survey Unit F8131372

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Table 2-1. Survey Unit Instrumentation Instrument Model; Serial No.

Detector Model; Serial No.

MDC Static (dpm/100 cm2 ) T MDC Scan (dpm/100 cm 2)

M2350; 193700 43-68B; 190294 433 M2350; 203486 43-68B; 161400 433 M2350; 175834 43-68B; 148634 433 M2350; 193700 43-116-1B; 216072 796 1033 1033 1033 3258 Tennelec; 0401171 N/A 4.9 dpm c, 8:2 dpm P3 N/A The scan and static MDC's provided represent the most conservative MDC values for the survey conducted.

Table 2-2. Investigation Criteria and DCGL Value Parameter Value cm 2)

(dpm/100 c2 Investigation Criteria - Direct 43000 Investigation Criteria - Scan 43000 DCGLw 43000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8131372 Investigation October 2, 2008 Survey Unit F8131372 (none required)

Data Assessment October 2, 2008 Survey Unit F8131372

CF8131372 Gross Activity Sample Results Quantile Plot 0

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