ML090930085
| ML090930085 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/03/2008 |
| From: | Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097 | |
| Download: ML090930085 (19) | |
Text
Rancho Seco Final Status Survey Summary Report June 3, 2008 Reactor Building Exterior Dome Survey Unit F8113000 Prepared BC Date:_
FSS E gine r Reviewed By:
Date:
Lead FSVEngineer Approved By:
Date:
2 Dismantlement (-uperintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8113000, Reactor Building Exterior Dome Survey Unit
Description:
Operating History: The reinforced concrete structure contained the reactor and supporting systems. The building contained four 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. No events documenting exterior contamination were found.
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 -27' elevation showed a mean gross activity level of 1,535,383 dpm/100 cm 2 and a maximum value of 8,134,000 dpm/100 cm 2. Direct measurements on the grade elevation showed a mean gross activity level of 201,670 dpm/100 cm 2 and a maximum value of 370,000 dpm/100 cm 2. Direct measurements on the +40' elevation showed a mean gross activity level of 51,521 dpm/100 cm2 and a maximum value of 99,150 dpm/100 cm 2.. Direct measurements on the +60' elevation showed a mean gross activity level of 20,110 dpm/100 cm 2 and a maximum value of 46,660 dpm/100 cm 2. Direct measurements on the exterior roof showed a mean gross activity level of 1,364 dpm/l 00 cm 2 and a maximum value of 1,571 dpm/100 cm 2. Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the interior of the reactor building was determined to be a Class 1 area and the exterior was a Class 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 randomly determined and 16 m2 were scanned for approximately 3%
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.
The reactor building exterior survey (F8113001) was designed as a class 3 survey of the exterior walls of the building. The survey design excludes the roof under the assumption that the roof characterization data could be accepted as the final survey data. The survey of the r6of (changed to F8113000 from the initial SA8113000 designation) was Page 2 of 9 FSS Summary Report F8113000
performed in 2005 using a crane to access the roof. The crane was scheduled to leave site allowing a small window of opportunity to perform the survey.
The roof survey consists of 30 direct beta measurements, 16 one m2 scans covering 3 percent of the surface area, and 16 smears. The locations of the direct measurement points were determined on a random basis within a restricted area based on engineering judgment and personnel safety considerations. The reactor building roof lacks tie off points and is surrounded by a low concrete wall allowing survey personnel access only to the area adjacent to the wall.
In order to reduce the safety risk to personnel, it seems reasonable to accept the characterization for the roof as the data is consistent with clean, uncontaminated concrete.
There is little to be gained by repeating the measurements as the same safety requirements will be in place.
C' Page 3 of 9 FSS Summary Report F8113000
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:
F811 Survey Unit:
Class:
SU Area (m2):
Evaluator:
DCGL (dpm/100 cm 2):
Area Factor:
Design DCGLemc (dpm/100 cm2):
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 (%):
Sign P:
Calculated Relative Shift:
Relative Shift Used:
N-Value:
Design N-Value + 20%:
Design Min Samples N:
Grid Spacing L:
3000 3
575 Gary Frank 43000 N/A N/A 21500 119 0.05 0.05 Cs-137 N/A 16 3%
1.645 1.645 0.99865 180.6 3
11 14 14 N/A Reactor Building Exterior Dome 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 4 of 9 PSS Summary Report F8113000
Survey Results:
A total of 30 direct measurements were made in F8113000. 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 4269 to 6646 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 beta activity and none was detected at the MDC shown in Table 2-1 of Attachment 2. The removable activity samples were not counted for alpha at the time of collection, however, applying the alpha to beta ratio of the structure nuclide profile would result in alpha activity well below the MDA of the detector.
Table 2. Direct Measurement Results Measurement ID Gross Activit (dpm/100 cm F8113000-CO001BD F8113000-CO002BD F8113000-CO003BD F8113000-CO004BD F8113000-CO005BD F8113000-CO006BD F8113000-CO007BBD F8113000-CO008BD F8113000-CO009BD F8113000-CO01OBD F8113000-CO011 BD F8113000-CO01 2BD F8113000-CO013BD F8113000-CO014BD F8113000-CO015BD F8113000-CO016BD F8113000-CO017BD F8113000-C001 8BD F8113000-CO01 9BD F8113000-CO02OBD F8113000-C0021 BD F8113000-CO022BD F8113000-CO023BD F8113000-C0024BD F8113000-CO025BD F8113000-CO026BD F8113000-C0027BD F8113000-C0028BD F8113000-CO029BD F8113000-CO03OBD Mean:
Median:
Standard Deviation:
Range:
1836 2148 2474 2360 2262 2262 1950 2397 2391 2044 1857 2386 2225 2173 2075 2137 2376 2158 2184 2122 2505 2360 1940 2158 2111 1873 2065 2516 2044 2148 2185 2158 191 1836 -2516 Range:
1836-2516 Page 5 of 9 FSS Summary Report F8113000
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/i00 cm 2)
F8113000C0001SM F8113000C0002SM F8113000C0003SM F8113000C0004SM F8113000C0005SM F8113000C0006SM F8113000C0007SM F8113000CO008SM F8113000C0009SM F8113000C0010SM F8113000C0011SM F8113000C0012SM F8113000C0013SM F8113000C0014SM F8113000C001 5SM F8113000C0016SM Mean:
Median:
Standard Deviation:
. Range:
-17.50 5.80 81.60
-17.50
-64.13
-11.66
-40.81 17.50
-46.64 11.70 35.00
-34.98 5.80
-29.15 23.40 70.00
-0.72
-2.93 40.5
-64.13 to 81.60 Page 6 of 9 FSS Summary Report F8113000
Survey Unit Data Assessment:
The survey design required 30 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. Since both values of sigma resulted in a relative shift greater than three (3), no additional samples were required.
Page 7 of 9 FSS Summary Report F81 13000
Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm 2):
N/A Ambient Background Used (dpm/100cM2):
N/A Average Ambient BKG = 0 Actual Direct Measurements (N):
30 Median (dpm/100 cm 2):
2158 Mean (dpm/100 cm2):
2185 Direct Measurement Standard Deviation 191 (dpm/100 cm 2):
Total Standard Deviation (dpm/100 cm 2):
191 Based on samples and backgrounds.
Maximum (dpm/100 cm 2):
2516 Material Type:
N/A Background Subtract Not Applied Sign Test Final N Value:
30 S+ Value:
30 Critical Value:
20 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:
Investigate All Measurements <0.5 DCGL Pass the Sign Test?
Yes Reject the Null Hypothesis?
Yes Does the Survey Unit Pass All Criteria?
Investigate Survey Unit Passes Page 8 of 9 FSS Summary Report F8113000
'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 3 structure survey and the sample results are consistent with that classification. The variability of the survey results was greater than the characterization data used for survey design. However, no additional samples were required. 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 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 F8113000 meets the release criteria of IOCFR20.14d2.
Page 9 of 9 FSS Summary Report F8113000 Maps June 3, 2008 Survey Unit F8113000
Containment. Bldg. Beta Direct Survey 1
126 125 124 123 122 121 120 119 118 C
117 116 115
,004 110S-94 93 92 91 90 8887 86 8584 83 F8113000-Mi
' Page 2 of 3 Att. 1 Maps F8113000
Containment Bldg. Beta Scan Survey C0012BS @ Cap 80 F8113000-M2 Page 3 of 3 Att. 1 Maps F81 13 000 Instrumentation June 3, 2008 Survey Unit F8113000
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; 193700 43-68B; 190294 433 1033 M2350; 203482 43-68B; 178511 433 1033 L2000; 36594 N/A 131.3 dpmf3 N/A Table 2-2. Investigation Criteria and DCGL Value Parameter d
aluc (dpm/100 cm2)
Investigation Criteria - Direct 21500 Investigation Criteria - Scan 43000 DCGLw 43000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8113000 Investigation June 3, 2008 Survey Unit F8113000 (none required)
Data Assessment June 3, 2008 Survey Unit F8113000
Cf Q (tn 00 F8113000 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/100cm2 4-3,000 2,500 2,000 1,500 1,000 2158 500 0
0 20 40 60 Percentile 80 100 Direct MeasuIrernents (cipm/100cm2)
-median
-75th Percentile....-
50th Percentile
- -o cgQ CD U) 0 FBI 13000 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpm/100cm=
b Cn Cn U) a3 3000 2500 E
U o° 2000 C.0 a01500
'C 500-0.
0 0 0 0
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275E 2125 111 A.
0 0
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-00000,00000*0000000000O0000000000 UuU.UUoUUUUUUUUUUUUUUUUoUUUUUUo 00 C:)
0 Measurement Locations 1o Gross Activity -
Average -
"+3StDev" -
"-3StDev
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0 CD)
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F811 3000 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 ci~
LL 0
13 12 11 10 9
8 7
6 5
4 3
2 1
0 (0
(0 I'.-
to Cl Cl Cl Bins - Upper End Value (dpm/1 OOcrn2)
............