ML082620102
| ML082620102 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/29/2008 |
| From: | Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| References | |
| MPC&D 08-064 | |
| Download: ML082620102 (20) | |
Text
Rancho Seco Final Status Survey Summary Report May 29, 2008 0' Elevation Auxiliary Steam Support Survey Unit F8132131 Prepared By:&
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T-X_
Date:________
FS E-ieer Reviewed By:
Date:
LeadOSS Engineer Approved By:
Date:
Dismantlement Superintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8132131, 0' Elevation Auxiliary 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 cm2 and a maximum value of 5,720,000 dpm/1 00 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 dpm/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 cm2. Direct measurements on the +40' elevation showed a mean gross activity level of 3,288 dpm/1 00 cm2 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/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 105 m2 were scanned for approximately 34% 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 F81321'31
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 cm 2):
Type I Error:
Type II Error:
Predominant Nuclide:
Sample Area (m2):
Scan Area (m2):
Scan Coverage (%):
Zl-, :
Zl-P :
Sign P:
Calculated Relative Shift:
Relative Shift Used:
N-Value:
Design N-Value + 20%:
Design Min Samples N:
Grid Spacina L:
2131 2
310.7 Gary Frank 43000 N/A N/A 21500 342 0.05 0.05 Cs-137 22.2 105 34%
1.645 1.645 0.99865 62.8 3
11 14 14 4.7 0' Elevation Auxiliary Steam Support 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 NUREG-1575 Table 5-5 Class 2 Class 2 Page 3 of 8 FSS Summary Report F8132131
Survey Results:
A total of 14 direct measurements were made in F813213 1. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. Two of the gamma particle scan measurements indicated areas of elevated activity. Beta scan activity ranged from 1929 to 5847 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 Activit (dpm/100 cm F8132131-CO001BD 1966 F8132131-CO002BD 1733 F8132131-CO003BD 1598 F8132131 -CO004BD 1172 F8132131-CO005BD 1172 F8132131-CO006BD 1836 F8132131-CO007BD 1634 F8132131 -CO008BD 996 F8132131 -CO009BD 1733 F8132131-CO01OBD 1816 F8132131-CO011BD 1743 F8132131-CO012BD 1764 F8132131-CO013BD 1468 F8132131-CO014BD 1727 Mean:
1597 Median:
1730 Standard Deviation:
289 Range:
996-1966 Page 4 of 8 FSS Summary Report F81321131
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2)
F8132131C0001SM
-2.24 F8132131 C0002SM
-3.53 F8132131C0003SM
-3.53 F8132131 C0004SM
-0.95 F8132131 C0005SM
-0.95 F8132131 C0006SM
-4.82 F8132131 C0007SM
-3.53 F8132131 C0008SM
-3.53 F8132131 C0009SM
-0.95 F8132131C0010SM
-3.53 F8132131C0011SM
-4.82 F8132131C0012SM
-2.24 F8132131C0013SM
-4.82 F8132131C0014SM
-2.24 Mean:
-2.98 Median:
-3.53 Standard Deviation:
1.41 Range:
-4.82 to -0.95 Page 5 of 8 FSS Summary Report F8132131
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 F8132131
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):
14 Median (dpm/100 cm 2):
1730 Mean (dpm/100 cm 2):
1597 Direct Measurement Standard Deviation 289 (dpm/O00 cm 2):
Total Standard Deviation (dpm/100 cm2):
289 Based on samples and backgrounds.
Maximum (dpm/100 cm 2):
1966 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 Page 7 of 8 FSS Summary Report F8132131
Survey Unit Investigations and Results:
Two investigations in grid 07 were required for the particle scan measurements and the results are reported in Attachment 3.
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. Two potential areas of elevated activity were detected and evaluated as shown in Attachment 3.
==
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/1 00 cm2 and none of the removable surface activity measurements exceeded 10% of the DCGL. Two investigations were required and resulted in a 1 square meter section in particle scan grid 7 to be elevated to Class 1 that will be evaluated under Survey Unit F8132133.
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 F8132131 meets the release criteria of 10CFR20.1402.
Page 8 of 8 FSS Summary Report F8132131 Maps May 29, 2008 Survey Unit F8132131
F8132131 Auxiliary Building Exterior Beta Scan Measurements k) 0 North Face 69 ft 2
6.4 ml aS j
22BS 23BS 25 118S 07 128S 13BS 14B8 0180l 02BI 13BSJ 04BS 058S' 068 I
I Looking South 20 m 2
0' Elev Refleocted Ceiling 583.ft2 54.1 m 2
'O.5m x 2m Looking Southeast 742 ft 2.
68.9 m2 N
cn 1l5 7BS5BIS
-1O~
- Not in e.y unit Looking East 29.7 M 2
Looking West 62.5 m2 0 Elev Floor 744 ft2 69.1 m2 0'-0" ELEV. Crotch Walls tj Scans on grids 28, 33 and 99 were not performed.
Grids 28 and 33 could not be placed due to error in map measurements. Grid 99's location presented a problem obtaining correctly performed scan measurement. Sufficient area was scanned to meet the
-Classification requirement.-
F8132131 - M1
0 F8132131 Auxiliary Building Exterior Direct Measurement/Sample Points 110-105-100 95-90 -
85 -
80-75 70 North Face 69 ft2 6.4 ml 12BD 4.7m--'- 110BD*4.7m---* 10BD 2.6m t
Looking Southeast 742 ft 2
68.9 m 2
0'Eley Reflected Ceiling 583 ft2 54.1 m2 65-60 55 -
50 45-40 35 30 25 20 15-10-5-
- 05BD0, 4.7m -
06BD 2.7m
~t Looking West 62.5 m2 1
i N
00 0.8m 1380 4.7m-.1 14->1*.14m No<i y unzt Looking East 29.7 m 2
0' Elev Floor 744 ft2 69.1 m2 0'-0" ELEV. Crotch Walls 00 tLP
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5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 F8132131 - M2
CD F8132131 Auxiliary Building Exterior Gamma Particle Scan Investigation area found to exceed investigation level reclassified as Class 1 A
NA Not part of particle survey I.TI 00 F8132131 - M3 Instrumentation May 29, 2008 Survey Unit F8132131
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; 203481 44-10; 171992 N/A 5.2 pCi/g M2350; 175834 43-68B; 190482 433 1033 M2350; 203486 43-68B; 161400 433 1033 Tennelec; 0401171 N/A 6 dpm a, 12 dpm f3 N/A Table 2-2. Investigation Criteria and DCGL Value Parameter (dpm/100 cm 2)
Investigation Criteria - Direct 43000 Investigation Criteria - Scan 43000 DCGLW 43000 DCGLEMc N/A Page 2 of 2 Att. 2 Instrumentation F8132131 Investigation May 29, 2008 Survey Unit F8132131
Table 3-1 Survey Unit Investigation Investigation Initial Value Investigation Elevated Area Investigation DCGLemc Grid Lnves Initial Result Area ar DCGL Result Unity Level (cpm)
(cpm)
(dpm/lOOcm2)
(m2)
Factor (dpm/lOOcm2)
Fraction 07 8197 14410 285041 N/A N/A lm x 1lm area reclassified 07 8197 11862 138938 lmxm N/A N/A asClass1andsurveyed under Survey Unit F8132133 Survey Unit Remainder DCGL=
SU Mean N/A 43,000 EMC Unity Sum N/A NOTE: The elevated measurements were found during the gamma particle scan utilizing a 2350-1 and 44-10 (2" x 2" Nal) detector. The area was bounded with the 44-10 and analyzed using the InSpector 1000. The results required the area around the two spots in Grid 7 reclassified as a Class 1. The area will be surveyed under Survey Unit F8132133.
Page 2 of 2 Att. 3 Investigation F8132131 Data Assessment May 29, 2008 Survey Unit F8132131
CD 0
Cl)
CD) 00 t'Q F8132131 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpmll 00cm2 2,500 2,000 I.
1730 1,500 -
1,000 500 0
0 20 40 60 Percentile 80 100 Direct Measurements (dpm/100cm2)
-median
. -75th Percentile - --
- 50th Percentile
CD U4 3
0 F8132131 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpmlO00cm=!
A+
00 3000 F' 2500 E
U g 2000 Ea 1500 1000 500 M.---
- 1 2463 0
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n mm m
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U Measurement Locations o
Gross Activity -
Average -
"+3StDev" -
"-3StDev"
CD 0
00 F81 32131 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 C09 9
8 7
6 5
4 3
2 1
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Bins - Upper End Value (dpm/l 00cm2)