ML091000386
| ML091000386 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 01/15/2009 |
| From: | Donna Anderson Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097 | |
| Download: ML091000386 (25) | |
Text
Rancho Seco Final Status Survey Summary Report January 13, 2009 Fuel Storage Building/Auxiliary Building Gap, (-) 6' El. to (+) 40' El.
Survey Unit F8120171 Prepared By:
Date:-
6.5 !,wq FSS Engineer Reviewed By:
exLA&ate:
1 9
Lead FSS Engineer Approved By:
2--7,1 Date:
_ -_o Dismantlement Su'erintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8120171, Fuel Storage Building/Auxiliary Building Gap, (-) 6' El. to (+) 40' 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/100 cm 2 and a maximum value of 200,000,000 dpm/l 00 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 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.
During final status surveys of F8120171 (Fuel Storage Building -Auxiliary Building Gap
(+) 0' El. to (+) 40' El., Class 2), beta measurements identified activity within four grids that exceeded the DCGL of 43,000 dpm/100 cm 2. Three grids 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 144 m2 were scanned for approximately 47% 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 F8120171
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:
F812 Survey Unit:
Class:
SU Area (m2):
Evaluator:
DCGL (dpm/100 cm2):
Area Factor:
Design DCGLemc (dpm/100 cm 2):
LBGR (dpm/100 cm2):
Design Sigma (dpm/100 cm2):
Type I Error:
Type II Error:
Predominant Nuclide:
Sample Area (m2):
Scan Area (M2):
Scan Coverage (%):
Zl-, :
Sign P:
Calculated Relative Shift:
Relative Shift Used:
N-Value:
Design N-Value + 20%:
Design Min Samples N:
Grid Spacing L:
0171 2
305 D. Anderson 43,000 N/A N/A 21,500 747 0.05 0.05 Cs-137 22.4 144 47%
1.645 1.645 0.99865 28.7 3
11 14 14 4.7 Fuel Storage Building/Auxiliary Building Gap, (-).6' El. to (+) 40' El.
Structure Surface LTP Table 5-4 Gross Activity DCGL Class 2 Class 2 Default = 50% DCGL Class 2 Class 2 Uses 3.0 if Relative Shift is
>3 NUREG-1575 Table 5-5 Class 2 Class 2 Page 3 of 8 FSS Summary Report F8120171
Survey Results:
A total of 16 direct measurements were made in F8120171. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. Four of the beta scan measurements indicated areas of elevated activity. Scan activity ranged from 4,115 to 110,855 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 F8120171-CO003BD F8120171 -CO004BD F8120171-CO005BD F8120171 -CO006BD F8120171 -CO007BD F8120171-CO008BD F8120171 -CO009BD F8120171-COOIOBD F8120171-CO011BD F8120171 -Co01 2BD F8120171--Co013BD F8120171-COO4BD F8120171--Co015BD F8120171-CO016BD F8120171 -COOI7BD F8120171--COOlBBD Mean:
Median:
Standard Deviation:
Range:
1,691 1,458 1,675 1,354 1,650 1,670 1,478 1,769 1,333 1,660 1,369 1,458 1,738 1,639 3,102 1,904 1,684 1,655 412 1,333 - 3,102 Page 4 of 8 FSS Summary Report F8120171
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2)
F8120171C0003SM 3.58 F8120171C0004SM
-1.58 F8120171C0005SM 6.16 F8120171 C0006SM 1
F8120171C0007SM 2.29 F8120171 C0008SM 4.87 F8120171CO009SM 1
F8120171CO010SM 1
F8120171CO011SM 6.16 F8120171C0012SM 4.87 F8120171C0013SM
-0.29 F8120171C0014SM 2.29 F8120171C0015SM 3.58 F8120171C0016SM
-0.29 F8120171C0017SM
-0.29 F8120171C0018SM
-0.29 Mean:
2.13 Median:
1.64 Standard Deviation:
2.49 Range:
-1.58 to 6.16 Page 5 of 8 FSS Summary Report F8120171
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 F8120171
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):
16 Median (dpm/100 cm 2):
1,655 Mean (dpm/100 cm 2):
1,684 Direct Measurement Standard Deviation 412 (dpm/100 cm 2):
Total Standard Deviation (dpm/100 cm 2):
412 Based on samples and backgrounds.
Maximum (dpm/100 cm 2):
3,102 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:
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 F8120171
Survey Unit Investigations and Results:
Four investigations (scan grids 28, 33, 50 and 55) were required for the scan measurements and the results are reported in Attachment 3.
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. Four potential areas of elevated activity were detected and evaluated as shown in Attachment 3.
==
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. Four 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 F8120171 meets the release criteria of 10CFR20.1402.
Page 8 of 8 FSS Summary Report F8120171 Maps January 13, 2009 Survey Unit F8120171
0 o*t 1'10 40' El.
Location of Fuel Storage Building at Rancho Seco site Opening into SIent Fuel Pool Remaining styrofoam 20' El.
0' EI.
00 Class 1 Area removed from F8120171 and surveyed under F8120181.
0.0 0.5 1.0 1.5 2.0 Distance in Meters Map F8120171-1, Fuel Storage Building (+) 0' El. to (+) 40' El.
Styrofoam Gap area between Fuel Storage Building and Auxiliary Building Fuel Storage Building South Wall (Looking North)
Area Estimate: 150 square meters
cf*
CDQ (50 0
00 C')
40' EF.
Remaining styrofoam Opening into Diesel Generator Room I
20.'-El.
...............O0:..El.
0' El.
0.0 0.5 1.0 1.5 2.0 Distance in Meters Map F8120171-2, Fuel Storage Building (+) 0' El. to (+) 40' El.
Styrofoam Gap area between Fuel Storage Building and Auxiliary Building Auxiliary Building North Wall (Looking South)
Area Estimate: 155 square meters
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1 2
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Distance in Meters Map F8120171-3, Fuel Storage Building (+) 0' El. to (+) 40' El.
Styrofoam Gap area between Fuel Storage Building and Auxiliary Building Random Start Location
40' El.
('I) 0 0
I Class 1 Area removed from this
[j survey unit and surveyed under 00 F8120181.
0.0 0.5 10 1.5 2.0 Distantce mn Meters exterior of East Wall) 20' El.
5 m above grade 0.3 m above grade 0' El.
Map F8120171-4, Fuel Storage Building South Wall (Looking North)
Beta Direct Measurements F8120171C0003BD to F8120171C0009BD 4.7 meter grid spacing
0 00 2.0 m (from exterior c 5 m above grade E
fEast Wall)
IOBO I5BD 0.3 m above grade "E
17jBD whs-v~~~-~~
Map F8120171-5, Auxiliary Building North Wall (Looking South)
Beta Direct Measurements F8120171CO01OBD to F8120171C0018BD 4.7 meter qrid spacinq
(0 0
O Grids investigated.
Class 1 Area removed from this survey unit and surveyed under F8120181.
00 0.0 0.5 1.0 1.5 2.0 Distance in Meters Map F8120171-6, Fuel Storage Building South Wall (Looking North)
Beta Scan Measurements F8120171C0001BS to F8120171C0062BS Total Scan Area: 60 sq.-meters
40' El.
00 00 cit 00 16BS I 7BS 8BS 9BS 1OBS 111BS 15BS 14BS I 13BS 12BS 20' El.
62BS 61 BS 47BS 48BS 49BS 50BS 111BS 60BS 112BS 113BS 114BS 115BS 116BS 59BS 117BS 118BS 51BS 54BS I 55BS 58BS 119BS 120BS' 528 53BS 56BS 57BS Class 1 Area removed E]
from this survey unit and surveyed under package F8120181.
jf Additional scan grids added to F8120171.
0 El.
121BS 1ý2Bs, 1i,20-38ý1,24B, 15Si6, B 0.0 0.5 1.0 1.5 2.0 Distance in Meters Map F8120171-7, Fuel Storage Building South Wall (Looking North).
Beta Scan Measurements F8120171C0001BS to F8120171C0062BS and F8120171C0111BS to F8120171C0126BS Total Scan Area: 99 sq. meters
(r0 0
40' El.
92S9 9laS1 90BS B9BS888Sý 87BS 86BS 85BS 84BS 83BS 82BS 20' El.
0' El.
0.0 0.5 1.0 1.5 2.0 Distance in Meters r Additional scan grids added to F8120171.
-II Map F8120171-8, Auxiliary Building North Wall (Looking South)
Beta Scan Measurements F8120171C0063BS to F8120171C0110BS Total Scan Area: 45 sq. meters Instrumentation January 13, 2009 Survey Unit F8120171
Table 2-1. Survey Unit Instrumentation Instrument Detector MDC Static MDC Scan Model; Serial No.
Model; Serial No.
(dpm/100 cm2 )
(dpm/100 cm2 )
M2350; 149794 43-68/5B; 149103 433 1,033 M2350; 180738 43-68/5B; 148942 433 1,033 Tennelec; 0401171 N/A 4.93 dpm,
N/A 8.21 dpm 3 Table 2-2. Investigation Criteria and DCGL Value Param eter V l eC 2
(dpm/100 cm 2)
Investigation Criteria - Direct 43,000 Investigation Criteria - Scan 43,000 DCGLw 43,000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8120171 Investigation January 13, 2009 Survey Unit F8120171
Table 3-1 Survey Unit Investigation Investigation Initial Value Investigation Elevated Area Investigation DCGLemc Result Area DCGLemc Result Unity Level (cpm)
(cpm)
(Cpm)
(m 2)
F (dpm/lOOcm2)
Fraction 28 5,840 7,338 6,012 0.023 N/A 43,000 31,186 33 5,840 8,327 0.052 N/A 43,000 43,194 Refer to Note
.9,360 below.
33 5,840 7,134 0.093 N/A 43,000 37,006 50 5,840 15,109 17,345 0.186 N/A 43,000 89,973 55 5,840 6,685 0.139 N/A 43,000 34,677 0.00 7,193 55 5,840 6,948 0.076 N/A 43,000 36,041 0.00 DCGL =
SU Mean =
Survey Unit Remainder 43,000 1,684 0.039 EMC Unity Sum 0.039 NOTE: Grids 25 to 50 removed from survey package F8120171, reclassified as Class 1, remediated, and a new survey performed under survey package F8120181.
Page 2 of 2 Att. 3 Investigation F8120171 Data Assessment January 13, 2009 Survey Unit F8120171
('D 0
Aý 00 F8120171 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/1OOcm 2 I:
4-3,500 3,000 2,500 2,000 1,500 1,000 500 0
1655 1t 0
20 40 60 80 100 Percentile Direct Measurements (dpm/100cm2)
-median
- - 75th Percentile....
50th Percentile
CD 0
F8120171 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpml00icm=
p*
CD Cn 00 0
-3 3500 N-3000-E 2500-
' 2000-
- %we1500 1000-
< 500-0 3=,=
O 0
00 o
0 0
0 0
- I 2921
- 1 1684 I -
=
- I 448 3
1 3
3 1
3 3
3 3
m cm m
m m m
mm m m m m cm in C
C 0
0 C
0 0
C 0
0 C
0 0
C 0
C Measurement Locations o
Gross Activity -
Average
"+3StDev" -
"-3StDev"l
CD~
0ý-
CD F8120171 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 7
C I-U-
C 6
5 4
3 2
1 0
NN Irj 00 Bins - Upper End Value (dpm/1 00cm2)