ML090890588
| ML090890588 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 06/18/2008 |
| From: | Andersen D Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097, F8260151 | |
| Download: ML090890588 (20) | |
Text
Rancho Seco Final Status Survey Summary Report June 18, 2008 Turbine Building (+) 0' El., South Floor Survey Unit F8260151 Prepared By:
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V9-? eq Lead FSS Engineer Approved By:
Date:________
Dismantlement erintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8260151, Turbine Building (+) 0' El., South Floor Survey Unit
Description:
Operating History: The reinforced concrete and steel structure contained the turbine-generator and supporting systems. The building contained five 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. Direct measurements in the condenser pit elevation showed a mean gross activity level of 3,077 dpm/100 cm 2 and a maximum value of 24,900 dpm/l 00 cm2. Direct measurements on the grade elevation showed a mean gross activity level of 2,035 dpm/100 cm2 and a maximum value of 6,980 dpm/100 cm 2. Direct measurements on the mezzanine elevation showed a mean gross activity level of 1,566 dpm/100 cm 2 and a maximum value of 2,626 dpm/100 cm 2. Direct measurements on the +40' elevation showed a mean gross activity level of 2,843 dpm/100 cm 2 and a maximum value of 3,615 dpm!100 cm 2. Direct measurements on the building exterior showed a mean gross activity level of 1,984 dpm/100 cm 2 and a maximum value of 10,312 dpm/100 cm 2. Based on the classification procedure (DSIP-0020) and levels' of gross activity reported, the interior of the turbine building was determined to be Class 1, 2, & 3 areas and the exterior was, a Class 3.
During characterization surveys of F8260141 (Turbine Building (+) 0' El., South Floor, Class 2), beta measurements identified activity within a 4-meter by 4-meter area that exceeded the DCGL of 43,000 dpm/100 cm 2. The area was subsequently remediated and reclassified as a Class 1 structure, based on the classification procedure (DSIP-0020). As a result of the reclassification, a new survey package was initiated as F8260151.
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 16 m2 were scanned for 100% 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 F8260151
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:
F826 Survey Unit:
Class:
SU Area (m2):
Evaluator:
DCGL (dpm/100 cm2):
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 (%):
Sign P:
Calculated Relative Shift:
Relative Shift Used:
N-Value:
Design N-Value + 20%:
Design Min Samples N:
Grid Spacin2 L:
0151 1
16 D. Anderson 43,000 14.9 640,700 25,030 5,990 0.05 0.05 Cs-137 1.0 16 100%
1.645 1.645 0.99865 3
3 11 14 14 1.0 Turbine Building (+) 0' El.,
South Floor Structure Surface LTP Table 5-4 Gross Activity DCGL Class 1 Class 1 Adjusted Class 1 Class I Uses 3.0 if Relative Shift is
>3 NUREG-1575 Table 5-5 Class I Class 1 Page 3 of 8 FSS Summary Report F8260151
Survey Results:
A total of 16 direct measurements were made, in F8260151. 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 3,492 to 13,953 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 Activit (dpm/100 cm i
F8260151-CO001BD F8260151-CO002BD F8260151-CO003BD F8260151-CO004BD F8260151-CO005BD F8260151-C0006BD F8260151-CO007BD F8260151-CO008BD F8260151 -CO009BD F8260151-Co01OBD F8260151-CO011BD F8260151-Co012BD F8260151-Co013BD F8260151-Co014BD F8260151-CO015BD F8260151-Co016BD Mean:
Median:
Standard Deviation:
Range:
1,323 1,421 1,323 1,520 1,110 1,312 1,473 1,899 1,567 2,806 1,509 1,717 1,349 1,535 1,421 1,551 1,552 1,491 380 1,110 - 2,806 Page 4 of 8 FSS Summary Report F8260151
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/l00 cm 2) 4-F8260151 C0001 SM F8260151CO002SM F8260151 C0003SM F8260151 C0004SM F8260151 COOO5SM F8260151CO006SM F8260151 C0007SM F82601 51 C0008SM F8260151 C0009SM F8260151Co010SM F8260151C0011SM F8260151Co012SM F8260151CO013SM F8260151CO014SM F8260151Co015SM F8260151Co016SM Mean:
Median:
Standard Deviation:
Range:
-0.95
-4.82
-3.53
-2.24 0.34
-2.24
-0.95
-2.24
-2.24
-0.95 4.22
-4.82
-2.24
-2.24 0.34
-4.82
-1.83
-2.24 2.3
-4.82 to 4.22 Page 5 of 8 FSS Summary Report F8260151
Survey Unit Data Assessment:
The survey design required 16 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 F8260151
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):
16 Median (dpm/100 cm2):
1,491 Mean (dpm/100 cm2):
1,552 Direct Measurement Standard Deviation 380 (dpm/100 cm2):
Total Standard Deviation (dpm/100 cm 2):
380 Based on samples and backgrounds.
Maximum (dpm/100 cm 2):
2,806 Material Type:
N/A Background Subtract Not Applied Sign Test Final N Value:
16 S+ Value:
16 Critical Value:
11 Sufficient Samples Collected:
Yes Maximum Value < DCGL:
Yes Median Value < DCGL:
Yes Mean Value < DCGL:
Yes Maximum Value < DCGLemc:
Yes Class 1 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 F8260151
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 1 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. Therefore the EMC criterion was met.
==
Conclusion:==
The FSS of this survey unit was properly designed as a Class 1 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 43,000 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 F8260151 meets the release criteria of 10CFR20.1402.
Page8 of8 FSS Summary Report F8260151 Maps June 18, 2008 Survey Unit F8260151
0 1
2 3
4 Distance in Meters Map F8260151-1, South Turbine Building (+) 0' Elevation Class 1 Area Area Estimate: 16 sq. meters Page 2 of 5 Att. 1 Maps F8260151
-~-----------------------
CD NRIII ýIII-J.
.2 n fro inso th ord r 1.2 m E
0 2 4 6
I I 12 14 1 2 2 02 4
6 60 10 12 14 10 18 20 2
00 CN C:)
2 N
0 0.25 0.5 0.75 1.0 Distance in Meters Map F8260151-2, South Turbine Building (+) 0 Elevation Class 1 Area Random Start Location
CD 0
m 12.6 m 3B 431 0.6 m o
Distance in meters from SW comer 2
2 Map F8260151-3, South Turbine Building (+) 0' Elevation Class 1 Area Beta Direct Measurements F8260151C0001BD to F8260151C0016BD 1 m by 1 m grid spacing It 00 3
2 0
0.25 0.5 0.75 1.0 Distance in Meters
0 f-I' 4
16BS 15BS 14BS 13BS i.0m
.0m 9BS 1OBS 11BS 12BS 2,1 f BBS 7BS 6BS 5BS 1BS 2BS 3BS 4BS
.0 m It' 00 1-1 3
3 N) 0 3
_C:o Distance in meters 3
from SW corner 0
0.25 0.5 0.75 1,0 Distance in Meters Map F8260151-4, South Turbine Building (+) 0 Elevation Class 1 Area Beta Scan Measurements F8260151C0001BS to F8260151C0016BS Instrumentation June 18, 2008 Survey Unit F8260151
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; 149794 43-68/5B; 149103 433 1,033 Tennelec; 0401171 N/A 5.88 dpm a, N/A 11.71 dpm 13 Table 2-2. Investigation Criteria and DCGL Value Parameter d
alue c (dpm/100 cm2)
Investigation Criteria - Direct 640,700 Investigation Criteria - Scan 640,700 DCGLw 43,000 DCGLEMc 640,700 Page 2 of 2 Att. 2 Instrumentation F8260151 Investigation June 18, 2008 Survey Unit F8260151 (none required)
Data Assessment June 18, 2008
- Survey Unit F8260151
It~
4'-
U)1 F8260151 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/1 00cm2 Im 3,000 -
2,500 -
2,000 -
1,500 -
1,000 -
1491 500-0 0
20 40 60 80 100 Percentile
- Direct measurements (dpm/lO0cm2) medi an 75th Percentile 50th Percentile
o F8260151 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpm100cmt 3000 a
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(tZ CD Cnj F82601 51 Gross Activity Frequency Plot DCGL = 43000 dpm/100cm2 LL C0
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N" It00 ON Bins - Upper End Value (dpm/1 00cm2)