ML081610218
| ML081610218 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 01/29/2008 |
| From: | Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| References | |
| MPC&D 08-032 | |
| Download: ML081610218 (20) | |
Text
Rancho Seco Final Status Survey Summary Report January 29, 2008 Room 111 Stairway Survey Unit F8131001 Prepared By Date:_________
FSS En ne Reviewed By:
Date:
Lead FSS"Engineer Approved By:
7 Date:
I 13 -V Dismantlement Superintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8131001, Room 111 Stairway 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 cm2. Direct measurements on the -29' elevation showed a mean gross activity level of 544,756 dpmr/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 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 37.3,758 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/100 cm 2. Direct measurements on the +40' elevation showed a mean gross activity level of 3,288 dpm/100 cm2 an da 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/1 00 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 25 m2 were scanned for approximately 30% 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 F813 1001
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:
Survey Unit:
Class:
SU Area (m2):
Evaluator:
DCGL (dpm/100 cm 2):
Area Factor:
Design DCGLemc (dpm/100 cm2):
LBGR (dpm/100 cm2):
Design Sigma (dpm/100 cm 2):
Type I Error:
Type II Error:
Predominant Nuclide:
Sample Area (m2):
Scan Area (M2):
Scan Coverage (%):
ZI-, :
Sign P:
Calculated Relative Shift:
Relative Shift Used:
N-Value:
Design N-Value + 20%:
Design Min Samples N:
Grid Spacing L:
F813 1001 2
83 Gary Frank 43000 N/A N/A Room I1I Stairway Structure Surface LTP Table 5-4 Gross Activity DCGL Class 2 Class 2 Default 50% DCGL Class 2 Class 2 21500 6935 0.05 0.05 Cs-137 5.18 25 30%
1.645 1.645 0.99865 3.2 3
11 114 14 2.4 Uses 3.0 if Relative Shift is
>3 NUREG-1575 Table 5-5 Class 2 Class 2 Page 3 of 8 FSS Summary Report F8131001
Survey Results:
A total of 17 direct measurements were made in F8131001. 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 2171 to 3213 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 F8131001-CO001BD 1328 F8131001-COO2BD 1292 F8131001-CO003BD 1426 F8131001-CO004BD 1318 F8131001-COOO5BD 1395 F8131001-CO006BD 1359 F8131001.CO0007BD 1395 F8131001-CO008BD 1261 F8131001-CO009BD 1261 F8131001-CO01OBD 1385 F8131001-CO011BD
.1312 F8131001-CO012BD 1494 F8131001-CO013BD 1136 F8131001-CO014BD 1229 F8131001-CO015BD 1302 F8131001-CO016BD 1369 F8131001-CO017BD 1478 Mean:
1338 Median:
1328 Standard Deviation:
91 Range:
1136-1494 Page 4 of 8 FSS Summary Report.
F813 1001
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2)
F8131001CO001SM
-4.82 F8131001CO002SM 4.22.
F8131001CO003SM
-2.24 F8131001CO004SM 1.64 F8131001 C0005SM
-3.53 F8131001 C0006SM
-0.95 F8131001C0007SM 8.09 F8131001C0008SM 1.64 F8131001C0009SM
-2.24 F8131001CO010SM 2.93 F8131001CO011SM 0.34 F8131001COO12SM 6.8 F8131001CO013SM
-0.95 F8131001CO014SM
-2.24 F8131001CO015SM
-2.24 F8131001CO016SM
-0.95 F8131001CO017SM 2.93 Mean:
0.5 Median
-0.95 Standard Deviation:
3.59 Range:
-4.82 to 8.09 Page 5 of 8 FSS Summary Report F813 1001
Survey Unit Data Assessment:
The survey design required 17 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 F8131001
Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm 2):
N/A Ambient Background Used (dpm/100 cm2):
N/A Average Ambient BKG 0
Actual Direct Measurements (N):
17 Median (dpm/100 cm2):
1328 Mean (dpm/100 cm 2):
1338 Direct Measurement Standard Deviation 91 (dpm/100 cm 2):
Total Standard Deviation (dpm/100 cm 2):
91 Based on samples and backgrounds.
Maximum (dpm/] 00 cm 2):
1494 Material Type:
N/A Background Subtract Not Applied Sign Test Final N Value:
17 S+ Value:
17 Critical Value:
12 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 F8131001
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 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 F8131001 meets the release criteria of I0CFR20.1402.
Page 8 of 8 FSS Summary Report F813 1001 Maps January 29, 2008 Survey Unit F8131001
(DO t0) 0 9
8 7
6 5
4 3
2 00 uj 8
9 10 11 12
crQ 0
('D 00 uo C)
North Wall ROOM 111 North & East Walls BETA SCANS F8131001 - M2
(D~
0 All grids are 1 meter square with the exception of 09BS Looking South Looking West r17 00 Wo C,)
S)
Room 111, Stairway Beta Scans F8131001 - M3
21BS DN STAIRS 00 REFLECTED CEILING Room 111 Stairway Beta Scans F8131001 - M4 Instrumentation January 29, 2008 Survey Unit F8131001
Table 2-1. Survey Unit Instrumentation Instrument Detector MDC Static MDC Scan Model; Serial No.
Model; Serial No.
(dpm/100 cm 2 )
(dpm/100 cm2)
M2350; 203486 43-68B; 190476 433 1033 Tennelec; 0401171 N/A 5 dpm a, 11 dpm f3 N/A Table 2-2. Investigation Criteria and DCGL Value Param eterV a 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 F8131001 Investigation January 29, 2008 Survey Unit F8131001 (none required)
Data Assessment January 29, 2008 Survey Unit F8131001
0
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