ML090990730
| ML090990730 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 07/04/2008 |
| From: | Donna Anderson Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097 | |
| Download: ML090990730 (23) | |
Text
Rancho Seco Final Status Survey Summary Report July 4, 2008 Fuel Storage Building (+) 40' El., Control Rod Transfer Pit Survey Unit F8121005 Prepared By: '. ) o'-- Date: 7/4/,//oz8' FSS Engineer Reviewed By: Date: _ q .sb)
Lead FSS Engineer Approved By: Date: 2.-6 -c-7 Dismantlement erintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8121005, Fuel Storage Building (+) 40' El., Control Rod Transfer Pit 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 cm 2 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 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 randomly determined and 3.1 m2 were scanned for approximately 9%
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 F8121005
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F812 Fuel Storage Building
(+) 40' El.,
Control Rod Transfer Pit Survey Unit: 1005 Structure Surface Class: 3 LTP Table 5-4 SU Area (m2): 33.4 Evaluator: D. Anderson DCGL (dpm/100 cm 2): 43,000 Gross Activity DCGL Area Factor: N/A Class 3 Design DCGLemc N/A Class 3 (dpm/100 cm 2):
LBGR (dpm/100 cm 2): 42,553 Adjusted Design Sigma (dpm/100 cm 2): 149 Type I Error: 0.05 Type II Error: 0.05 Predominant Nuclide: Cs-137 Sample Area (M 2 ): N/A Class 3 Scan Area 2 (M ): 3.1 Scan Coverage (%): 9% Class 3 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: 14 Design N-Value + 20%: 14 NUREG-1575 Table 5-5 Design Min Samples N: 14 Class 3 Grid Spacing L: N/A Class 3 Page 3 of 8 FSS Summary Report F8121005
Survey Results:
A total of 14 direct measurements were made in F8121005. 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 4,145 to 6,250 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 Activity (dpm/100 cm )
F8121005-C0001BD 1,432 F8121005-CO002BD 1,219 F8121005-CO003BD 1,209 F8121005-CO004BD 1,209 F8121005-CO005BD 1,188 F8121005-CO006BD 1,634 F8121005-CO007BD 2,013 F8121005-CO008BD 1,214 F8121005-CO009BD 1,364 F8121005-CO01 OBD 1,136 F8121005-C0011 BD 1,323 F8121005-CO012BD 1,276 F8121005-CO013BD 1,452 F8121005-CO014BD 1,784 Mean: 1,389 Median: 1,299 Standard Deviation: 257 Range: 11136 - 2,013 Page 4 of 8 FSS Summary Report F8121005
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2)
F8121005C0001 SM 0.34 F8121005CO002SM -0.95 F8121005CO003SM 0.34 F8121005CO004SM -2.24 F8121005COOO5SM -0.95 F8121005CO006SM 2.93 F8121005CO007SM -0.95 F8121005CO008SM -3.53 F8121005CO009SM 6.8 F8121005C0010SM -2.24 F8121005C001ISM -4.82 F8121005C0012SM -0.95 F8121005C0013SM 0.34 F8121005C0014SM 0.34 Mean: -0.39 Median: -0.95 Standard Deviation: 2.81 Range: -4.82 to 6.8 Page 5 of 8 FSS Summary Report F8121005
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 greater than the design standard deviation. Since both values of sigma resulted in a relative shift greater than three (3), no additional samples were, required.
Page 6 of 8 FSS Summary Report F8121005
Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used 2 (dpm/100 cm ): N/A Ambient Background Used (dpm/I00 cm 2): N/A Average Ambient BKG = 0 Actual Direct Measurements (N): 14 Median (dpm/100 cm 2): 1,299 Mean (dpm/100 cm 2): 1,389 Direct Measurement Standard Deviation 257 (dpm/100 cm 2):
Total Standard Deviation (dpm/100 cm 2): 257 Based on samples and backgrounds.
Maximum (dpm/100 cm 2): 2,013 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 3 Total Standard Deviation <= Sigma: Investigate All measurements < DCGL.
Survey unit passes.
Pass the Sign Test? Yes Reject the Null Hypothesis? Yes Does the Survey Unit Pass All Criteria? Investigate All measurements < DCGL.
Survey unit passes.
Page 7 of 8 FSS Summary Report F8121005
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 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 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 F8121005 meets the release criteria of 10CFR20.1402.
Page 8 of 8 FSS Summary Report F8121005
Attachment 1 Maps July 4, 2008 Survey Unit F8121005
0f Map F8121005-1, Fuel Storage Building
(+) 40' Elevation (floor) 00 Location of Control Rod Transfer Pit Storage Building site 00I E
04 If)
C,)
C)l 00A 112 ft.- 34.1 m N 0 1 2 3.
Distance in Meters 4
0.5 ft - 0.15 m N
0.0 0.5 1.0 1.5 2.0 Distance in Meters Map F81210005-2, Fuel Storage Building +40' El.
Control Rod Transfer Pit Area Estimate: 33.4 sq. meters Page 3 of 8 Att. 1 Maps F8121005
00 6.5 1.6 1.5 -20o Distance in Meters Map F81210005-3, Fuel Storage Building +40' El.
Control Rod Transfer Pit Random Measurement Locations Page 4 of 8 Att. 1 Maps F8121005
(J]
,-b ~0.16 m[_ [ 0.16 m F 0.6m 0.17 m
> 0.24 m5 -0.6 m
- 1BD---
__E 'N E _ __ _
1.24 28 E OA 9BD E mN
- U2 I E North Wall East Wall
-TI 00 Map F81210005-4, Fuel Storage Building +40' El.
Control Rod Transfer Pit
_North Wall Beta Direct Measurements F8121005C0001BD to F8121005C0006BD 0.0 0.5 1.0 1.5 2.0 Distance Meters East Wall Beta Direct Measurements F8121005C0007BD to F8121005C0009BD
-e OD 00 k
D.2 m r IOBD E
4m E
CN\
0.2 m 1 ,- 0.2 m M W-s0.2 South Wall West Wall It-C0 Map F81210005-5, Fuel Storage Building +40' El.
C) Control Rod Transfer Pit (A South Wall Beta Direct Measurements
-. F8121005CO01OBD to F8121005C0012BD 0.0 0.5 1.0 Distance in Mewers 1.5 2.0 West Wall Beta Direct Measurement F8121005C0013BD
0.0 0.5 1.0 1.5 2.0 Map F81210005-6, Fuel Storage Building +40' El.
Distance in Meters Control Rod Transfer Pit Floor Beta Direct Measurement F8121005C0014BD Page 7 of 8 Att. I Maps )F8121005
N 0.0 0.5 1,0 1.5 2.0 Map F81210005-7, Fuel Storage Building +40' El.
Distance in Meters Control Rod Transfer Pit Beta Scan Measurements F8121005COOO1BS to F8121005C0004BS
'Total Scan Area: 3.1 sq. meters Page 8 of 8 Att. I Maps F8121005
Attachment 2 Instrumentation July 4, 2008 Survey Unit F8121005
Table 2-1. Survey Unit Instrumentation Instrument Detector MDC Static MDC Scan 2
Model; Serial No. Model; Serial No. (dpm/100 cm ) (dpm/100 cm 2 )
. M2350; 175834 43-68B; 190482 433 1,033 Tennelec; 040117.1 N/A 5.88 dpm 11.71 dpmct,P3 N/A Table 2-2. Investigation Criteria and DCGL Value Param eter (dpm/100V l ecm 2 )2 Investigation Criteria - Direct 21,500 Investigation Criteria - Scan 43,000 DCGLw 43,000 DCGLEMC *N/A Page 2 of 2 Att. 2 Instrumentation F8121005
Attachment 3 Investigation July 4, 2008 Survey Unit F8121005 (none required)
Attachment 4 Data Assessment July 4, 2008 Survey Unit F8121005
CD F8121005 Gross Activity Sample Results Quantile Plot 0 DCGL = 43000 dpm/100cm2 2,500 2,000 1,500 U. 1299 CD 1,000
('D 500 0
0 20 40 60 80 100 Percentile 00
- Direct Measurements (dpm/100ccm2) -median - - - 75th Percentile . 50th Percentile
('Q 0CD F8121005 Gross ActIvity Sample Results Scatter Plot DCGL = 43000 dpmll00cm=
2500
-- -- -- ----- ---- ---- ---- ---- ---- -- ----- *1 2160 2000 0 0
0 A
C 1500 E 1389 0 0 0 0 0 0 1000 (1o
---- ------ ---- 1 619
- 500 0
o 0 0 0 0 0 0 0 0 Cl 0 0 0 0 r IN l0 W tlO - - 0 10 r- N, o a i ci a i ci ci ci c 0 0 0 0 0 0e0 M 00 r U 0 0 00 0 0 Measurement Locations 00 G
0........ s A t - A e .-.
- -"+3StDev" _" 3_S.tDe...v' NJI
-O (D
0.
F8121005 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 6
5 4
U-0 3-4-d C()
2-1-
0 0 ( I", 00 if) 5O N C'J c..,. O)
LO) CO 00 Bins - Upper End Value (dpm/1 00cm2) t'J
... I.-
......