ML082620150
| ML082620150 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 06/13/2008 |
| From: | Tallman D Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| References | |
| MPC&D 08-064 | |
| Download: ML082620150 (23) | |
Text
Rancho Seco Final Status Survey Summary Report June 13, 2008 AB Western Stairwell -10' to grade including TF transition Survey Unit F8130091 Prepared By: Dan A. Tallman Date: June 13, 21 FSS Engineer ReviewedBy:-
/U-DateB:il/1*/0 Lead FSS Engineer Approved By:
7/
Date:
7-Dismantlement S'perintendent, Radiological 008
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8130091, AB Western Stairwell -10' to grade including TF transition.
Survey Unit
Description:
Operating History: The Auxiliary Building is a reinforced concrete structure that 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.
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. The direct measurements on the -20' elevation showed a mean gross activity level of 247,831 dpm/1 00 cm2 and a maximum value of 10,080,000 dpm/100 cm2. Direct measurements on the grade elevation showed a mean gross activity level of 373,758 dpm/100 cm2 and a maximum value of 5,800,000 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 dpni//100 cm2. Based on the classification procedure (DSIP-0020) and levels of gross activity reported, Survey Unit 8130091 within the interior, transitioning to the exterior, of the auxiliary building was determined to be a Class 3 area.
HSA Events: HSA Report pg. 63.
Survey Unit Design Information:
The Survey Unit Design Parameters are presented in Table I-below. The survey unit and measurement locations are depicted on the maps in Attachment 1. Direct measurement locations were randomly determined and 20 m2 were scanned for approximately 11%
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 F8130091
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:
F813 0091 3
Survey Unit:
Class:
SU Area (m2):
Evaluator:
DCGL (dpm/100 cm 2):
Area Factor:
Design DCGLemc (dpm/100 cm 2):
LBGR (dpm/100 cm'):
Design Sigma (dpm/100 cm2):
Type I Error:
Type II Error:
Predominant Nuclide:
Sample Area (m2):
Scan Area (M2):
Scan Coverage (%):
Zip:
Sign P:
Calculated Relative Shift:
Relative Shift Used:
N-Value:
Design N-Value + 20%:
Design Min Samples.N:
Grid Spacing L:
178.1 D.A.Tallman 43000 N/A N/A 21500 6935 0.05 0.05 Cs-137 N/A 20 11%
1.645 1.645 0.99865 3.1 3
11 14 14 N/A AB Western Stairwell -10' to grade including TF transition Structure Surface LTP Table 5-4 Gross Activity DCGL Class 3 Class 3 Default = 50% DCGL Class 3 Class 3 Uses 3.0 if Relative Shift is
>3, NUREG-1575 Table 5-5 Class 3 Class 3 Page 3 of 8 FSS Summary Report F8130091
Survey Results:
A total of 14 direct measurements were made in F8130091. 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 2912 to 7175 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/lO0 cm F8130091 -COOOI BD F8130091-CO002BD F8130091-CO003BD F8130091 -CO004BD F8130091 -CO005BD F8130091-CO006BD F8130091-CO007BD F8130091-CO008BD F8130091 -CO009BD F8130091-COOIOBD F8130091-CO011BD F8130091-Co012BD F8130091-Co013BD F8130091-CO014BD Mean:
Median:
Standard Deviation:
Range:
1198 2505 1069 1266 1136 1380 1494 1302 1281 1203 1198 1292 1266 1369 1354 1273 348 1069-2505 Page 4 of 8 FSS Summary Report F8130091
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm2)
F8130091C0001SM
-2.24 F8130091CO001SM
-4.82 F8130091C0002SM
-0.95 F8130091CO003SM
-3.53 F8130091C0004SM
-2.24 F8130091 C0005SM
-4.82 F8130091C0006SM
-3.53 F8130091 C0007SM 1.64 F8130091C0008SM
-3.53 F8130091 C0009SM
-2.24 F8130091CO010SM 2.93 F8130091C0011SM
-3.53 F8130091C0012SM 0.34 F8130091C0013SM 1.64 F8130091C0014SM
-2.24 Mean:
-1.81 Median:
-2.24 Standard Deviation:
2.42 Range:
-4.82 to 2.93 Page 5 of 8 FSS Summary Report F8130091
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 Page 6 of 8 FSS Summary, Report F109 F8130091
Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/lO0 cm 2):
N/A Ambient Background Used (dpm/100 cm 2):
N/A Average Ambient BKG 0
Actual Direct Measurements (N):
14 Median (dpm/100 cm2):
1273 Mean (dpm/100 cm 2):
1354 Direct Measurement Standard Deviation 348 (dpm/100 cm 2):
Total Standard Deviation (dpm/100 cm2):
348 Based on samples and backgrounds.
Maximum (dpm/100 cm 2):
2505 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 3 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 F8130091
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 3 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 3 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 F8130091 meets the release criteria of 10CFR20.1402.
Page 8 of 8 FSS Summary Report F8130091 Maps June 13, 2008 Survey Unit F8130091
0 00 TOP Door S
Facing ELEV. -_.
Room 127 Staftwel Looking West Room 127 StaorwelLoodrig East
.1 1.
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frWC~ Ni 'CICV C HILL OWC: 813000 Instrumentation June 13, 2008 Survey Unit F8130091
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; 203486 43-68B; 190476 433 1033 Tennelec; 0401171 N/A 6 dpm a, 12 dpm3 N/A Table 2-2. Investigation Criteria and DCGL Value Parameter (dpm/100 cm 2)
Investigation Criteria - Direct 21500 Investigation Criteria - Scan 43000 DCGLW 43000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8130091 Investigation June 13, 2008 Survey Unit F8130091 (none required)
Data Assessment June 13, 2008 Survey Unit F8130091
CF8130091 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/100cm2 3,000 2,5000 2,00"0
- i*,
1,500 En 1273 500.
0 0
20 40 60 80 100 Percentile Direct Measurements (dpm/100cm2)
-median
- - 75th Percentile - --
- 50th Percentile C:)
0C F8130091 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpmll00cm'
.71 00 Uj C)
C) 3000 F? 2500 E
502000 1000
"~500 a
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U MU U U
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U Measurement Locations 1 0 Gross Activity -
Average -
"+3StDev" -
"-3$tDev "I
(j)
En 00 F8130091 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 1
1 1
1 U-C.0 3
2 1
0 9
8 7
6 5
4 3
2 1
0 CO-'
Bins - Upper End Value (dpm/100cm2)