ML082620115
| ML082620115 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/12/2008 |
| From: | Donna Anderson Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| References | |
| MPC&D 08-064 | |
| Download: ML082620115 (22) | |
Text
Rancho Seco Final Status Survey Summary Report May 12, 2008 Building East Exterior Wall (+) 20' El. t Survey Unit F8120151 Fuel Storage Prepared By:
o (+) 69' 4" El.
FSS Er Date:
5I//2-/.aco Reviewed Date:
SLead Ft" Engineer Approved By:
7//
Date: 7 C"
Dismantlement Superintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8120151, Fuel Storage Building East 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/100 cm2 and a maximum value of 200,000,000 dpm/1 00 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 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 dpmr/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 determined using a random-start, fixed grid pattern and 130 in 2 were scanned for approximately 39% 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 F8120151
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:
F812 Survey Unit:
Class:
SU Area (m2):
Evaluator:
DCGL (dpm/100 cm 2):
Area Factor:
Design DCGLemc (dpm/100 cm 2):
LBGR (dpm/100 cm2):
Design Sigma (dpm/100 cm 2):
Type I Error:
Type II Error:
Predominant Nuclide:
Sample Area (M2):
Scan Area (M2):
Scan Coverage (%):
ZIp:
Sign P:
Calculated Relative Shift:
Relative Shift Used:
N-Value:
Design N-Value + 20%:
Design Min Samples N:
Grid Spacing L:
0151 2
332 D. Anderson 43,000 N/A N/A 40,759 747 0.05 0.05 Cs-137 23.71 130 39%
1.645 1.645 0.99865 3
3 11 14 14 4.8 Fuel Storage Building East Exterior Wall (+) 20' El. to
(+) 69' 4" El.
Structure Surface LTP Table 5-4 Gross Activity DCGL Class 2 Class 2 Adjusted 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 F8120151
Survey Results:
A total of 14 direct measurements were made in F8120151. 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 highest average ISOCS gamma measurement was 2,650 dpm/100 cm 2 Cs-137; Co-60 was not identified above the MDA. 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,)
F8120151-CO001BD 1,141 F8120151-CO002BD 1,437 F8120151 -CO003BD 1,738 F8120151-CO004BD 1,468 F8120151-CO005BD 1,452 F8120151 -CO006BD 1,349 F8120151 -CO007BD 1,198 F8120151-CO008BD 1,515 F8120151-CO009BD 1,302 F8120151-COOIOBD 1,235 F8120151-CO011BD 1,250 F8120151-CO012BD 1,193 F8120151-CO013BD 1,219 F8120151-CO014BD 1,494 Mean:
1,356 Median:
1,325 Standard Deviation:
167 Range:
1,141 - 1,738 Page 4 of 8 FSS Summary Report F8120151
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpml100 cm 2)
I.
F8120151COOOISM F8120151 C0002SM F8120151 C0003SM F8120151 CO004SM F8120151 CO005SM F8120151 C0006SM F8120151 C0007SM F8120151 C0008SM F8120151 C0009SM F8120151 CO010SM F8120151 CO01ISM F8120151 Co012SM F8120151 Co013SM F8120151C0014SM Mean:
Median:
Standard Deviation:
Range:
-3.53 0.34 4.22 6.8 0.34 1.64
-0.95
-0.95
-0.95
-0.95
-2.24
-2.24
-0.95 4.22 0.34
-0.95 2.91
-3.53 to 6.8 Page 5 of 8 FSS Summary Report F8120151
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 less than the design standard deviation so no additional samples were required.
Page 6 of.8 FSS Summary Report F8120151
Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm2):
N/A Ambient Background Used (dpm/100 cm 2):
N/A Average Ambient BKG = 0 Actual Direct Measurements (N):
14 Median (dpm/100 cm2):
1,325 Mean (dpm/100 cm2):
1,356 Direct Measurement Standard Deviation 167 (dpm/100 cm 2):
Total Standard Deviation (dpm/100 cm 2):
167 Based on samples and backgrounds.
Maximum (dpm/100 cm2):
1,738 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 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 F8120151
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 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 F8120151 meets the release criteria of 10CFR20.1402.
Page 8 of 8 FSS Summary Report F8120151
Attachment I Maps May 12, 2008 Survey Unit F8120151
0 TIt 00 Map F8120151-1, Fuel Storage Building Location at Rancho Seco site
6 9'4".-. E.L 40' El.__
20'.El.
a'EI I LI
"[I61.5 f
16.1 Map F8120151-2, Fuel Storage Building East Exterior Wall, 20' El. to 69' 4" El.
Area Estimate: 332 sq. meters Page 3 of 7 Att. 1 Maps F8120151
70 75 80 85 90 95 Random Start Location 9.1 m from south corner 9.1 m above grade (+0' El)go.
0' 0
1 2
3 4
Distance In Meters Map F8120151-3, Fuel Storage Building East Exterior Wall, 20' El. to 69' 4" El. (Class 2)
Random Start Location Page 4 of 7 Att. 1 Maps F8120151
Distance in meters from grade (+0' El.)
mo, N
0 1
2 3
4 Distance in Meters Map F8120151-4, Fuel Storage Building East Exterior Wall, 20' El. to 69' 4" El.
Class 2 Beta Direct Measurements F8120151C0001BD to F8120151C0014BD 4.8 sq. meter grid spacing Page 5 of 7 Att. 1 Maps F8120151
3 3
3 43 3
43 30 0~~
0 1
2 3
Distance in Meters Map F8120151-5, Fuel Storage-Building East Exterior Wall, 20' El. to 69' 4" El.
Class 2 ISOCS Gamma Scan Measurements F8120151 C0001GS to F8120151 C0012GS 12.57 sq. meter field of view Total Scan Area: 130 sq. meters Page 6 of 7 Att. 1 Maps F8120151
N 0
1 2
3 4
Oistance in Meters Map F8120151-6, Fuel Storage Building East Exterior Wall, 20' El. to 69' 4" El.
Penetration Scan Measurements F8120151P0001BS to F8120151P0002BS Page 7 of 7 Att. 1 Maps F8120151 Instrumentation May 12, 2008 Survey Unit F8120151
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; 180733 43-98B; 148638 1,400 2,520 M2350; 203481 43-68B; 148629 433 1,033 Tennelec; 0401171 N/A 5.88 dpm a, N/A 11..71dpmf3 MDC Concrete - 1,220 dpm/100 cm2 Cs-137, Concrete - 886 dpm/100 cm2 Co-60 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 Ant. 2 Instrumentation F8120151 Investigation May 12, 2008 Survey Unit F8120151 (none required)
Data Assessment May 12, 2008 Survey Unit F8120151
DF8120151 Gross Activity Sample Results Quantile Plot 0
DCGL = 43000 dpm/1 00cm 2 2,400 -*
1,900 -
d 1,400"-
4**
1325
-100-
" 0 20 40 60 80 100 IPercentile Direct Measurements (dpm/100cm2) median 75th Percentile 50th Percentile
CD F8120151 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpmll00cn=
2000 1800 -.--------.----------------------------------
lass E 1600 0
0 0
0100 0
- r. 1200 -
0 0
0 0
4000 CD
'C 600 C4 000 200 V-IN 0 W
P.N. M 0
0 V-0 0 0
C 04 C
0 CD C
i C %
0 V-V" V-Vt a
0 a
C 0 a a
a a
a a
0a A
a 0
C 0
00 0
00 000 0
0 0
0 U
U U
U U,
U U
U U
U U
U U
U Measurement Locations 00 o
Gross Activ Average -
"+3StDev" -
- _-3StDev"j 0O
CD 0
F8120151 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 4
00 U-0 3
2 1
0 N-
,1O, N-Bins - Upper End Value (dpm/1 00cm2) r