ML091000387
| ML091000387 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 01/13/2009 |
| From: | Donna Anderson Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097 | |
| Download: ML091000387 (20) | |
Text
Rancho Seco Final Status Survey Summary Report January 13, 2009 Fuel Storage Building (-) 6' El. to (+) 15' El. South Exterior Wall, Class 1 Area Survey Unit F8120181 Prepared By: c6.
Approved By:
Dismantlement Superintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8120181, Fuel Storage Building (-) 6' El. to (+) 15' El. South Exterior Wall, Class 1 Area 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 cm2 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.
During final status surveys of F8120171 (Fuel Storage Building-Auxiliary Building Gap
(+) 0' El. to (+) 40' El., Class 2), beta measurements identified activity within two small areas that exceeded the DCGL of 43,000 dpm/100 cm2 . The areas were subsequently remediated and reclassified as a Class 1 structure, based on the classification procedure (DSIP-0020). Final surveys of the Class 1 area were performed under survey package F8120181.
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 50 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 F8120181
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F812 Fuel Storage Building (-) 6' El. to (+) 15' El. South Exterior Wall, Class 1 Area Survey Unit: 0181 Structure Surface Class: 1 LTP Table 5-4 SU Area (m2): 50 Evaluator: D. Anderson DCGL (dpm/100 cm 2): 43,000 Gross Activity DCGL Area Factor: 5.5 Class 1 Design DCGLemc 236,500 Class 1 (dpm/100 cm 2):
LBGR (dpm/100 cm 2): 21,500 Default = 50% DCGL 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): 3.57 Class 1 Scan Area (m ): 2 50 Scan Coverage (%): 100% Class 1 1.645 1.645 Sign P: 0.99865 Calculated Relative Shift: 4.7 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 1 Grid Spacing L: 1.9 Class I Page 3 of 8 FSS Summary Report F8120181
Survey Results:
A total of 21 direct measurements were made in F8120181. 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. Beta scan activity ranged from 4,761 to 84,311 dpm/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 F8120181 -CO001 BD 2,142 F8120181-CO002BD 4,959 F8120181-CO003BD 4,741 F8120181 -C0004BD 2,708 F8120181-CO005BD 6,064 F8120181-CO006BD 5,903 F8120181-CO007BD 4,658 F8120181-CO008BD 1,784 F8120181-CO009BD 2,262 F8120181-CO01OBD 1,971 F8120181-CO011BD 1,691 F8120181 -CO012BD 2,687 F8120181-CO013BD 1,681 F8120181-CO014BD 1,717 F8120181 -CO01 5BD 1,707 F8120181--Co016BD 4,824 F8120181-CO017BD 6,085 F8120181-CO018BD 1,748 F8120181-CO019BD 1,572 F8120181-CO02OBD 1,857 F8120181-CO021BD 2,614 Mean: 3,113 Median: 2,262 Standard Deviation: 1,671 Range: 1,572 - 6,085 Page 4 of 8 FSS Summary Report F8120181
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpmll00 cm 2) i F8120181COOOISM -0.29 F8120181C0002SM 8.75 F8120181 C0003SM 13.91 F8120181C0004SM -1.58 F8120181 C0005SM 6.16 F8120181C0006SM 6.16 F8120181CO007SM 11.33 F8120181 C0008SM 3.58 F8120181 C0009SM 1 F8120181CO010SM -0.29 F8120181 C0011 SM 3.58 F8120181 C001 2SM 3.58 F8120181Co013SM -1.58 F8120181 CO014SM 1 F8120181CO015SM -0.29 F8120181Co016SM -0.29 F8120181C0017SM 31.99 F8120181 CO018SM 6.16 F8120181 Co019SM 1 F8120181 C0020SM 2.29 F8120181C0021SM 1 Mean: 4.63 Median: 2.29 Standard Deviation: 7.55 Range: -1.58 to 31.99 Page 5 of 8 FSS Summary Report F8120181
Survey Unit Data Assessment:
The survey design required 21 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 F8120181
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): 21 2
Median (dpm/100 cm ): 2,262 Mean (dpm/100 cm 2): 3,113 Direct Measurement Standard Deviation 1,671 (dpm/100 cm 2):
2 Total Standard Deviation (dpm/100 cm ): 1,671 Based on samples and backgrounds.
Maximum (dpm/100 cm 2): 6,085 Material Type: N/A Background Subtract Not Applied Sign Test Final N Value: 21 S+ Value: 21 Critical Value: 14 Sufficient Samples Collected: Yes Maximum Value < DCGL: Yes Median Value < DCGL: Yes Mean Value < DCGL: Yes Maximum Value < DCGLemc: Yes Class I 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 F8120181
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 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 F8120181 meets the release criteria of 10CFR20.1402.
Page 8 of 8 FSS Summary Report F8120181
Attachment 1 Maps January 13, 2009 Survey Unit F8120181
CD 0
~N
-A-- ------.....
LIU Remaining styrofoam
//
Location of Fuel Storage Building 20'.El.
at Rancho Seco site Opening into Spent Fuel Pool 1.El 1 Class 1 Area removed from
- I-------- 0'-El.
Di.t-r' in .e- /'.Map F8120181-1, Fuel Storage Building () 6' El. to (+) 15' El.
0 . ."Styrofoam Gap area between Fuel Storage Building and Auxiliary Building Fuel Storage Building South Wall (Looking North)
Area Estimate: 50 square meters
40' El.
CD w
Random Start Location - Remaining styrofoam 1.0 m from West Wall 1.5 m above grade
/
Opening into Spent Fuel Pool
........... .20.'.El..
I I I I/ 1II I I 1I I I I II I I I I 03 ITJ 00 t0 2 t 4 6 8 10 . 1 Map F8120181-2, Fuel Storage Building (-) 6' El. to (+) 15' El.
C( -
00 Fuel Storage Building South Exterior Wall (Looking North)
Random Start Location 0.5 1.0 1.5 2.0 0 2 4 6 8 10 12 14 16 [ C lass 1Area removed from 0.0 I F8120171.
Distance in Meters
It 0
3.0 m above grade-1.5 m above grade-0' Elevation 2BD I'll 00 1.5 m below grade-00 Map F8120181-3, Fuel Storage Building (-) 6' El. to (+) 15' El.
Fuel Storage Building South Exterior Wall (Looking North)
Class 1 Area - Beta Direct Measurements 0.0 0.5 1.0 1.5 2.0 F8120181C0001BD to F8120181C0021BD Distance in Meters 1.5 meter grid spacing
40' El.
0 0
. * ~............ ..0.E....
20' El.
371SS B,..4B IBS' 3B, '3ýUB
... .. .O ' El.
00 00 0.0 0.5 1.0 1.5 2.0 Distance in Meters Lý, Map F8120181-4, Fuel Storage Building South-Wall (Looking North)
Beta Scan Measurements F8120181C0001BS to F8120181C0050BS Total Scan Area: 50 sq. meters
Attachment 2 Instrumentation January 13, 2009 Survey Unit F8120181
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; 180738 43-68/5B; 148942 433 1,033 Tennelec; 0401171 N/A 4.93 dpm tY N/A 8.21 dpm __
Table 2-2. Investigation Criteria and DCGL Value dp luc Parameter (dpmn/100 cm2)
Investigation Criteria - Direct 236,500 Investigation Criteria - Scan 236,500 DCGLw 43,000 DCGLEmc 236,500 Page 2 of 2 Att. 2 Instrumentation F8120181
Attachment 3 Investigation January 13, 2009 Survey Unit F8120181 (none required)
Attachment 4 Data Assessment January 13, 2009 Survey Unit F8120181
F8120181 Gross Activity Sample Results Quantile-Plot DCGL = 43000 dpm/1 00cm2 7,000 6,000 0
5,000 I:
4,000 4- 3,000 En V) 2262 2,000 1,000 0
0 20 40 60 80 100 Percentile I + Direct Measurements (dpm/100crn2) -median - - -75th Percentile - - - - 50th Percentile I 00
CD a
0 F8120181 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpml00icm=
10000
-4* 8000 8126 E
0 C 6000 0 0 0 0 E
CL 4000 3113 a *0 0 0 0 0 0. 0 0 0 0 0 0 2000 CD Z0 0
02
-2000 I 1I 1 t -V-I-I-1 I - -I - f-i I- -h -1900
.-4000 coo mnm.m0*mm0r mmmmmrnmmm0 nO0I n*O n
-4./
0 0000000 0 a 0 0.0 0 0 U U U U U U U U U U U U U U Ul U UU U U U Measurement Locations It t iy--
oGross Ac-lv Avrg veag -v ' +3Stbe
+ - '"-3tDe 00
CD F81 20181 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 9
8 7
aI) 6 5
0 4
cth 3 2
1 0
(N C D (
[1. . r:5ý1ý 00 Bins - Upper End Value (dpm/1 00cm2) 00
.......