ML091000388
| ML091000388 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 07/22/2008 |
| From: | Donna Anderson Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097 | |
| Download: ML091000388 (27) | |
Text
Rancho Seco Final Status Survey Summary Report July 22, 2008 Fuel Storage Bldg (+) 40' El., Auxiliary Bldg end, Lower Walls Survey Unit F8121003 Prepared By: c. A tx'-.) Date:. 7I2/*2-1 /A FSS Engineer Reviewed By: I02--) 0
?4 Lead FSS Engineer Approved By: Date:______
Dismantlement Superintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8121003, Fuel Storage Bldg (+) 40' El., Auxiliary Bldg end, Lower Walls 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/100 cm 2 and a maximum value of 200,000,000 dpm/100 cm 2 . Direct measurements on the +40' elevation showed a mean gross activity level of 5,942 dpm/100 cm2 and a maximum value of 19,357 dpm/100 cm 2.
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 cm 2. 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 Clafs 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 115.8 m 2 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 F8121003
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Table 1. Survey Unit Design Parameters Survey Design Value, Comment Parameter Survey Area: F812 Fuel Storage Bldg (+) 40' El., Auxiliary Bldg end, Lower Walls Survey Unit: 1003 Structure Surface Class: 1 LTP Table 5-4 SU Area (m2): 115.8 Evaluator: D. Anderson DCGL (dpm/100 2 cm ): 43,000 Gross Activity DCGL Area Factor: 3.4 Class I Design DCGLemc 146,200 Class 1 (dpm/100 cm 2):
LBGR (dpm/100 cm 2): 29,107 Adjusted Design Sigma (dpm/100 cm 2): 4,631 Type I Error: 0.05 Type II Error: 0.05 Predominant Nuclide: Cs-137 Sample Area (m2): 2.6 Class 1 Scan Area (M2 ): 115.8 Scan Coverage (%): 100% Class 1 1.645 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: 17 Class 1 Grid Spacing L: 2.6 Class 1 Page 3 of 8 FSS Summary Report F8121003
Survey Results:
A total of 26 direct measurements were made in F8121003. 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. The gamma activity ranged from < 943 dpm/100 cm2 Co-60 and < 1,3.10 dpm/100 cm 2 to 917 dpm/100 cm2 Cs-137. Beta scan activity ranged from 5,510 to 10,804 dpmr/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 F8121003-CO001BD 3,329 F8121003-CO002BD 3,417 F8121003-CO003BD 4,321 F8121003-C0004BD 3,869 F8121003-CO005BD 3,693 F8121003-C0006BD 3,274 F8121003-CO007BD 4,387 F8121003-CO008BD 3,913 F8121003-C0009BD 3,704 F8121003-CO01 OBD 3,505 F8121003-COOIIBD 3,792 F8121003-Co012BD 4,078 F8121003-CO01 3BD 4,189 F8121003-CO014BD 3,858 F8121003-Co01 5BD 3,627 F8121003-Co016BD 3,957 F8121003-CO017BD 3,472 F8121003-Co018BD 3,549 F8121003-Co019BD 3,153 F8121003-CO02OBD 3,869 F8121003-C0021 BD 3,417 F8121003-CO022BD 3,814 F8121003-CO023BD 3,902 F8121003-CO024BD 4,023 F8121003-CO025BD 3,770 F8121003-CO026BD 2,756 Mean: 3,717 Median: 3,781 Standard Deviation: 368 Range: 2,756 - 4,387 Page 4 of 8 FSS Summary Report F8121003
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2)
F8121,003C0001 SM 0.34 F8121003C0002SM 6.8 F8121003CO003SM 0.34 F8121003C0004SM 0.34 F8121003C0005SM 2.93 F8121003CO006SM -4.82 F8121003CO007SM -3.53 F8121003CO008SM -0.95 F8121003C0009SM -2.24 F8121003CO010SM -2.24 F8121003C001 1SM 0.34 F8121003C0012SM -0.95 F8121003C0013SM 1.64 F8121003CO014SM -2.24 F8121003C0015SM 0.34 F8121003C0016SM -3.53 F8121003CO017SM -2.24 F8121003C0018SM -4.82 F8121003C0019SM -4.82 F8121003C0020SM -3.53 F8121003CO02ISM -2.24 F8121003C0022SM 6.8 F8121003C0023SM 2.93 F8121003C0024SM 1.64 F8121003C0025SM 1.64 F8121003C0026SM -0.95 Mean: -0.5 Median: -0.95 Standard Deviation: 3.14 Range: -4.82 to 6.8 Page 5 of 8 FSS Summary Report F8121003
Survey Unit Data Assessment:
The survey design required 26 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 F8121003
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): 26 Median (dpm/100 cm 2 ): 3,781 Mean (dpm/100 cm 2 ): 3,717 Direct Measurement Standard Deviation 368 (dpm/100 cm 2):
Total Standard Deviation (dpm/100 cm 2): 368 Based on samples and backgrounds.
Maximum (dpm/O00 cm 2): 4,387 Material Type: N/A Background Subtract Not Applied Sign Test Final N Value: 26 S+ Value: 26 Critical Value: 17 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 .F8121003
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 F8121003 meets the release criteria of 10CFR20.1402.
Page8 of8 FSS Summary Report F8121003
Attachment 1 Maps July 22, 2008 Survey Unit F8121003
CD 0
33.75 ft. - 10.29 m 00 N -W 0 1 2 3 4 Distance in Motors Map F8121003-1, Fuel Storage Building +40' El. (Aux Bldg end)
East Wall (Lower 3 meters) Area Estimate: 36.7 sq. meters
1E 43 ft. - 13.11 m South Wall 0 1 2 3 DistanOc in Meters 4 Map F8121003-2, Fuel Storage Building +40' El. (Aux Bldg end)
South Wall (Lower 3 meters) Area Estimate: 43.2 sq. meters Page 3 of 12 Att. 1 Maps F8121003
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0 33.75 ft. - 10.29 m 00 It.,
0 1 2 3 4 Map F8121003-3, Fuel Storage Building +40' El. (Aux Bldg end)
Dostanco in Meters West Wall (Lower 3 meters) Area Estimate: 35.8 sq. meters
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- t ;41, L--
F--.v o+ J.;2.L 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 Map F8121002-4, Fuel Storage Building +40' El. (Aux Bldg end)
F.,. ' -: L "-L.- Lower Walls (Lower 3 meters) Random Start Location 0 1 2 3 4 Distance in Meters Page 5 of 12 Att. I Maps F8121003
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Map F8121003-5, Fuel Storage Building +40' El. (Aux Bldg end) 0 1 2 3 4 East Wall (Lower 3 meters) Beta Direct Measurements Dist.nc in %lo.o-F8121003CO001BD to F8121003C0008BD 2.60 sq. meter grid
l-Height in meters
. . 3.0 m
-- 0.40 m 0
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'IT E E E E c-i r- 'TCNj oEW Map F8121003-6, Fuel Storage Building +40' El. (Aux Bldg end) 0 1 2 3 4 Distance in Meters South Wall (Lower 3 meters) Beta Direct Measurements F8121003C0009BD to F8121003C0018BD 2.60 sq. meter grid Page 7 of 12 Att. 1 Maps F8121003
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Map F8121003-7, Fuel Storage Building +40' El. (Aux Bldg end) 0 1 2 3 4 West Wall (Lower 3 meters) Beta Direct Measurements Distance in Motors F8121003C0019BD to F8121003C0026BD 2.60 sq. meter grid
0 Cn a 2 E E c.- E E O CD v; E 0-o CO to I'l 00 N ,.
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Map F8121003-8, Fuel Storage Building +40' El. (Aux Bldg end) 0 1 2 3 Distance in Meters 4 East Wall (Lower 3 meters) Gamma Scan Measurements F8121003C0001GS to F8121003C0003GS 28 sq. meter field of view
Height in /
meters 1.51 m j --
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- 0 E C 10U
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I I Map F8121003-9, Fuel Storage Building +40' El. (Aux Bldg end) 0 1 2 3 4 Distance in Meters South Wall (Lower 3 meters) Gamma Scan Measurements F8121003C0004GS to F8121003C0006GS 28 sq. meter field of view Page 10 of 12 Att. I Maps F8121003
0 E F 2 (
0 C (0
1P 01 E0 00
-w - --- --- 0 C>Q Map F8121003-10, Fuel Storage Building +40' El. (Aux Bldg end) 0 1 2 3 4 West Wall (Lower 3 meters) Gamma Scan Measurements Distance in Meters F8121003C0007GS to F8121003C0009GS 28 sq. meter field of view
Map F8121003-11, Fuel Storage Building +40' El. -Aux Bldg end Lower Wall (10 ft) Penetration Scan Measurements F8121003P0001BS to F8121003P0005BS Page 12 of 12 Att. 1 Maps F8121003
Attachment 2 Instrumentation July 22, 2008 Survey Unit F8121003
Table 2-1. Survey Unit Instrumentation Instrument Detector MDC Static MDC Scan Model; Serial No. Model; Serial No. (dpm/100 cm2 ) (dpm/100 cm 2 )
M2350; 189089 43-68B; 161406 433 1,033 M2350; 175834 43-116-1B; 190642 796 3,258 Tennelec; 0401171 N/A 5.88 dpm a, N/A
_______ _______ _______ 11.71ldpmf_ _ _ _ _ _ _
IDetector Detector MDC ivioael No. Serial Nio.
Concrete - 1,310 dpm/100 cm22 Cs-137, ISOCS N/A 1983920 Concrete- 943 dpm/100 cm Co-60 Table 2-2. Investigation Criteria and DCGL Value Param eter (dpm/100 cm 2)2 V l eC Investigation Criteria - Direct 146,200 Investigation Criteria - Scan 146,200 Investigation Criteria - Scan (ISOCS average activity - 28 sq. 23,900 meter field of view)
DCGLw 43,000 DCGLEMC 146,200 Page 2 of 2 Att. 2 Instrumentation F8121003
Attachment 3 Investigation July 22, 2008 Survey Unit F8121003 (none required)
Attachment 4 Data Assessment July 22, 2008 Survey Unit F8121003
F8121003 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/1 00cm2 7,000 6,000 Cn 5,000 I
4,000 3781 00 3,000 2,000 1,000 0
0 20 40 60 80 100 Percentile I* Direct Measurements (dpm/100cm2) -median - - - 75th Percentile - - - - 50th Percentile I
a (4
0 fr-i) F8121003 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpml00ocm=
6000 OR" 5000 4821 E 0 u 0 00 g 4000 0 S--" - -
0 0 - 0V 0
0 0 3717 E. 0 0 E. 3000 - - - - - - - - - - - - - - - ft - - - - - - - - - - - - - -- -0 2813 Co 2000 a
Cn c-f C1000 0 4 , - - 1- 1 - . -..... .. I r---------------- ' '
1 '
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1 000000000 0 0 00000 0 0 00000000 0 *00 00 0000 0 rn C)3 C) a3 a a 03 ID 03 CD (0 0)001 CD 01 0n 000 0 N 0OrC4fl'tU)4D or* w 0 r aO 0 0 0 0 00O000 0 0 00000000 000000000 0 0 000000000 0 0 00000000 OUUOUOUUUU U U UUUUU U U UUUUUUUU Measurement Locations I-'
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- .............Average-civity.. .......... ... . ........-
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- "-3StDevi
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F81 21003 Gross Activity, Frequency Plot DCGL = 43000 dpm/1 00cm2 8
7 6
C) 0l 5 4-0~
4 3
0 2
1 0
r'- 00 LO c'J 00 I'J Bins - Upper End Value (dpm/1 00cm2)
...........