ML082620126
| ML082620126 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco (DPR-054) |
| Issue date: | 05/09/2008 |
| From: | Donna Anderson Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| References | |
| MPC&D 08-064 | |
| Download: ML082620126 (23) | |
Text
Rancho Seco Final Status Survey Summary Report May 9, 2008 Fuel Storage Building West Exterior Wall (+) 20' El. to (+) 69' 4" El.
Survey Unit F8120131 Prepared By:
- a. **-d-Ow O-Date:
.6/1/9 o'
Reviewed By:
Date:
Lea FSS Engineer Approved By:
Date:
7 Dismantlement Superintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8120131, Fuel Storage Building West Exterior Wall (+) 20' El. to (+) 69' 4" El.
Survey Unit
Description:
Operating History: The reinforced concrete structure contained the spent fuel pool and supporting systems. The building contained three main elevations including the pool.
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. Three documented instances of contamination through the common fuel building/turbine building wall were noted.
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 pool elevation showed a mean gross activity level of 16,900,000 dpm/l100 cm 2 and a maximum value of 200,000,000 dpm/100 cm2. Direct measurements on the +40' elevation showed a mean gross activity level of 5,942 dpm/100 cm 2 and a maximum value of 19,357 dpm/100 cmn2.
Direct measurements on the building exterior showed a mean gross activity level of 1,408 dpm/100 cm 2 and a maximum value of 21,600 dpm/100 cm2. Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the interior of the spent fuel 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 220 m2 were scanned for approximately 68% 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 F8120131
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:
F812 Fuel Storage Building West Exterior Wall
(+/-) 20' El. to (+) 69' 4" El.
Survey Unit:
0131 Structure Surface Class:
2 LTP Table 5-4 SU Area (m2):
322 Evaluator:
D. Anderson DCGL (dpm/100 cm2):
43,000 Gross Activity DCGL Area Factor:
N/A Class 2 Design DCGLemc N/A Class 2 (dpm/100 cm 2):
LBGR (dpm/100 cm2):
40,759 Adjusted Design Sigma (dpm/O00 cm2):
747 Type I Error:
0.05 Type II Error:
0.05 Predominant Nuclide:
Cs-137 Sample Area (m2):
23 Class 2 Scan Area (ml):
220 Scan Coverage (%):
68%
Class 2 Z1-, :
1.645 Zl-P :
1.645 Sign P:
0.99865 Calculated Relative Shift:
3 Relative Shift Used:
3 Uses 3.0 if Relative Shift is
>3 N-Value:
11 Design N-Value + 20%:
14 NUREG-1575 Table 5-5 Design Min Samples N:
14 Class 2 Grid Spacing L:
4.7 Class 2 Page 3 of 8' FSS Summary Report F8120i31
Survey Results:
A total of 19 direct measurements were made in F8120131. 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. All ISOCS gamnma measurements were less than the Cs-137 and Co-60 MDAs.
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 F8120131-COOOIBD 778 F8120131 -CO002BD 1,048 F8120131 -CO003BD 1,079 F8120131-CO004BD 1,110 F8120131 -CO005BD 1,089 F8120131 -CO006BD 809 F8120131-CO007BD 1,193 F8120131-C0008BD 882 F8120131-CO009BD 1,043 F8120131-CO01OBD 1,323 F8120131-C0011BD 1,509 F8120131-CO012BD 1,276 F8120131-CO013BD 1,712 F8120131-CO014BD 1,209 F8120131-CO015BD 1,416 F8120131-C0O016BD 1,250 F8120131-C0017BD 1,727 F8120131-C0018BD 1,359 F8120131--Co019BD 1,660 Mean:
1,235 Median:
1,209 Standard Deviation:
282 Range:
778-1,727 Page 4 of 8 FSS Summary Report F8120131
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm2 )
F8120131CO001SM
-3.53 F8120131C0002SM
-2.24 F8120131 C0003SM 0.34 F8120131 C0004SM
-2.24 F8120131 C0005SM
-2.24 F8120131 C0006SM
-3.53 F8120131C0007SM
-3.53 F8120131 C0008SM
-4.82 F8120131 C0009SM
-0.95 F8120131CO010SM 2.93 F8120131CO011SM 6.8 F8120131C0012SM 6.8 F8120131C0013SM 2.93 F8120131C0014SM 8.09 F8120131C0015SM
-0.95 F8120131COO16SM 1.64 F8120131C0017SM 10.68 F8120131COO18SM
-0.95 F8120131C0019SM 11.97 Mean:
1.43 Median:
-0.95 Standard Deviation:
5.13 Range:
-4.82 to 11.97 Page 5 of 8 FSS Summary Report F8120131
Survey. Unit Data Assessment:
The survey design required 19 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 F8120131
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):
19 Median (dpm/100 cm2):
1,209 Mean (dpm/100 cm 2):
1,235 Direct Measurement Standard Deviation 282 (dpm/100 cm2):
Total Standard Deviation (dpm/100 cm 2):
282 Based on samples and backgrounds.
Maximum (dpm/100 cm 2 ):
1,727 Material Type:
N/A Background Subtract Not Applied Sign Test Final N Value:
19 S+ Value:
19 Critical Value:
13 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 F8120131
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 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 43,000 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 F8120131 meets the release criteria of 10CFR20.1402.
Page 8 of 8 FSS Summary Report F81201,31
Attachment I Maps May 9, 2008 Survey Unit F8120131
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Map F8120131-2, Fuel Storage Building West Exterior Wall, 20' El. to 69' 4" El.
Area Estimate: 322 sq. meters Page 3 of 8 Att. 1 Maps F8120131
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go0 55 100 110 Random Start Location 5.6 m from north corner 3.7 m above turbine deck (40' El) t:
115 p"':
0 125 0
1 2
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Distance in Meters Map F8120131-3, Fuel Storage Building West Exterior Wall, 20' El. to 69' 4" El. (Class 2)
Random Start Location Page 4 of 8 Z;I Att. 1 Maps F8120131
C FA' no-3 6, N-0 1
2 3
4 Distance in Meters Map F8120131-4, Fuel Storage Building West Exterior Wall, 20' El. to 69' 4" El.
Class 2 Beta Direct Measurements F8120131C0001BD to F8120131C0019BD 4.79 sq. meter grid spacing Page 5 of 8 Att. 1 Maps F8120131
0 1
2 3
4 Distance in Meters Map F8120131-5, Fuel Storage Building West Exterior Wall, 20' El. to 69' 4" El.
Penetration Scan Measurements F8120131P0001BS to F8120131P0002BS Page 6 of 8 Att. 1 Maps F8120131
cCD 0 tn 0o ~CD no-3.
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4 Distance in Meters Map F8120131-6, Fuel Storage Building West Exterior Wall, 20' El. to 69' 4" El.
Class 2 ISOCS Gamma Scan Measurements F8120131C0001GS to F8120131C0014GS 10.2, 11.3 and 12.6 m2 fields of view Total Scan Area: 136 sq. meters Page 7 of 8 Att. 1 Maps F8120131
a CD 38 c SR 3 5 N-*
0 1
2 3
4 Distance in Meters Map F8120131-7, Fuel Storage Building West Exterior Wall, 20' El. to 69' 4" El.
Class 2 ISOCS Gamma Scan Measurements F8120131C0015GS to F8120131C0022GS 12.57 sq. meter field of view Total Scan Area: 84.6 sq. meters Page 8 of 8 Att. 1 Maps F8120131 Instrumentation May 9, 2008 Survey Unit F8120131 r,
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; 193700 43-68B; 160691 433 1,033 M2350; 203481 43-68B; 148629 433 1,033 M2350; 193700 43-116-1B; 216072 796 3,258 Tennelec; 0401171 N/A 5.88 dpm x, N/A 11.71 dpmf N/A Table 2-2. Investigation Criteria and DCGL Value Parameter (dpm/100 cm 2)
Investigation Criteria - Direct 43,000 Investigation Criteria - Scan 4,300 (ISOCS average activity)
DCGLw 43,000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8120131 Investigation May 9, 2008 Survey Unit F8120131 (none required)
Data Assessment May 9, 2008 Survey Unit F8120131
00 F8120131 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpmll 00cm2 I
4-2,000 1,800 1,600 1,400 1,200 1,000 800 600 400 200 0
1209 1r 0
20 40 60 Percentile 80 100 Direct Measurements (dpm/100cm2) -
median -
- 75th Percentile....
50th Percentile
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F8120131 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpmlO0=cn 00 C'
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F81 20131 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 5
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0 End Value (dpm/1 OOcm2)
N-(\\J N-t' Bins - Upper