ML082620167
| ML082620167 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 07/09/2008 |
| From: | Stein M Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| References | |
| F8130732, MPC&D 08-064 | |
| Download: ML082620167 (24) | |
Text
Rancho Seco Final Status Survey Summary Report July 9, 2008 East and West Heat Removal Cooler Rooms 051 and 052 Excavation Between Exterior Reactor Building Wall and Auxiliary Building Floor Slab Survey Unit F8130732 Prepared By: . Date: ll7 61 FSS Engineer Reviewed By: Date: ko10 Lead FSS Engineer Approved By: 7 Date: . -
Dismantlement uperintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8130732, East and West Heat Removal Cooler Rooms 051 and 052 Excavation Between Exterior Reactor Building Wall and Auxiliary Building Floor Slab Survey Unit
Description:
Operating History: The East and West Heat Removal Cooler Rooms are located on the
-20' elevation of the Auxiliary Building. The Auxiliary Building is a reinforced concrete structure that, during power operations, contained the Radwaste processing and supporting systems. The building has six main elevations. Residual levels of surface radioactivity were detected on all interior elevations of the building. Operating records and the HSA document several events with the potential for a release of radioactivity inside this structure.
Site Characterization: Direct measurements were taken on each interior elevation of the Auxiliary Building. These measurements confirmed the presence of plant-derived radionuclides. Direct measurements taken on the -20' elevation, showed a mean gross activity level of 247,831 dpm/100 cm 2 and a maximum value of 10,080,000 dpm/100 cm 2. Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the interior surfaces of the Auxiliary Building were determined primarily to be a Class 1 for the floors and lower walls (bottom 2 meters of the walls), and Class 2 for the upper walls and ceiling. Inside the East and West Heat Removal Cooler Rooms radioactive liquids leaked through the construction joints between the exterior surface of the Reactor Building wall and~the -20' Auxiliary Building floor slab. There were a number of areas on the concrete structures exposed during excavation of the area where the gross surface activity levels were higher than the DCGL prior to remediation.
Therefore, a Class 1 final status survey was performed on the East and West Heat Removal Cooler Rooms 051 and 052, excavation area between the exterior Reactor Building wall and Auxiliary Building floor slab.
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 93 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 F8130732
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F813 East and West Heat Removal Cooler Rooms 051 and 052, Excavation Between Exterior Reactor Building Wall and Auxiliary Building Floor Slab Survey Unit: 0732 Structure Surface Class: 1 LTP Table 5-4 SU Area (m2): 93 Evaluator: Michael Stein DCGL (dpm/100 cm 2): 43000 Gross Activity DCGL Area Factor: 4.1 Class I Design DCGLemc 176300 Class 1 (dpm/100 cm 2):
LBGR (dpm/100 cm 2): 21500 Default = 50% DCGL Design Sigma (dpm/100 cm 2): 12035 Type I Error: 0.05 Type II Error: 0.05 Predominant Nuclide: Cs-137 Sample Area (m2): 5.5 Class 1 Scan Area (m2): 93 Scan Coverage (%): 100% Class 1 ZI.* : 1.645 1.645 Sign P: 0.96407 Calculated Relative Shift: 1.7 Relative Shift Used: 1.7 Uses 3.0 if Relative Shift is
>3 N-Value: 14 Design N-Value + 20%: 17 NUREG-1575 Table 5-5 Design Min Samples N: 17 Class I Grid Spacing L: 2.3 Class 1 Page 3 of 8 FSS Summary Report F8130732
Survey Results:
A total of,25 direct measurements were made in F8130732. 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 bata scan measurements indicated areas of elevated activity. Beta scan activity ranged from 3,196 to 48,982 dpm/100 cm 2, based on a surveyor efficiency of 0.5 and no background subtracted. None of the gamma scan measurements indicated areas of elevated activity. Gamma scan activity ranged from 290 to 1,399 dpm/100 cm 2 for Co-60 and 396 to 22,297 dpm/100 cm 2 for Cs-137. Scan measurement locations for both beta and gamma emissions are identified in Attachment 1 of this report. 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 F8130732-CO001BD 1841 F8130732-CO002BD 3683 F8130732-CO003BD 2184 F8130732-CO004BD 7164 F8130732-CO005BD 3102 F8130732-CO006BD 1836 F8130732-CO007BD 1899 F8130732-CO008BD 2350 F8130732-CO009BD 1332 F8130732-CO01OBD 1285 F8130732-COOlI BD 1390 F8130732-CO012BD 1297 F8130732-COOI3BD 1123 F8130732-CO014BD 1577 F8130732-CO015BD 1355 F8130732-CO016BD 15100 F8130732-CO017BD 2485 F8130732-CO018BD 1426 F8130732-CO019BD 1924 F8130732-CO02OBD 3112 F8130732-CO021BD 1769 F8130732-CO022BD 2391 F8130732-CO023BD 1146 F8130732-CO024BD 1707 F8130732-CO025BD 1343 Mean: 2633 Median: 1836 Standard Deviation: 2879 Range: 1123-15100 Page 4 of 8 FSS Summary Report F8130732
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2)
F8130732C0001SM 1.64 F8130732C0002SM -2.24 F8130732C0003SM -3.53 F8130732C0004SM 2.93 F8130732C0005SM -2.24 F8130732C0006SM -3.53 F8130732C0007SM -0.95 F8130732C0008SM 4.22 F8130732C0009SM -3.53 F8130732C0010SM -3.53 F8130732C001 I SM -3.53 F8130732C0012SM 0.34 F8130732C0013SM -0.95 F8130732C0014SM -3.53 F8130732C0015SM 0.34 F8130732C0016SM 39.09 F8130732C0017SM 1.64 F8130732C0018SM 1.64 F8130732C0019SM 0.34 F8130732C0020SM 18.42 F8130732C0021 SM 1.64 F8130732C0022SM 26.17 F8130732C0023SM -2.24 F8130732C0024SM -3.53 F8130732C0025SM 0.34 Mean: 2.62 Median: 0.34 Standard Deviation: 10.25 Ranqe: -3.53 to 39.09 Page 5 of 8 FSS Summary Report F8130732
Survey Unit Data Assessment:
The survey design required 17 direct measurements for the Sign Test. In actuality, 25 direct measurements were obtained. 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 F8130732
Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm 2): N/A Ambient Background Used (dpm/O00 cm 2): N/A Average Ambient BKG = 0 Actual Direct Measurements (N): 25 Median (dpm/100 cm 2): 1836 Mean (dpm/100 cm 2): 2633 Direct Measurement Standard Deviation 2879 (dpm/100 cm 2):
TotalStandard Deviation (dpm/100 cm 2 ): 2879 Based on samples and backgrounds.
Maximum (dpm/100 cm 2): 15100 Material Type: N/A Background Subtract Not Applied Sign Test Final N Value: 25 S+ Value: 25 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 F8130732
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.
==
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 43000 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 F8130732 meets the release criteria of 10CFR20.1402.
Page 8 of 8 FSS Summary Report F8130732
Attachment 1 Maps July 9, 2008 Survey Unit F8130732
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ý Gamma Scan Points Taken 2.34 m Abovw
-2W-0" Floor, Spaced 1.5 m Apart, And ESTIMATED AREA 2
Centered Over Excavation, First Gamma Base 20.5 m Scan Point Located Over West Edge Of IT1 Sides 72.0 m 2 Room 52 Excavation.
00 Scale Feet TOTAL 92.5 rm2 AUXILIARY BUILDING EL. -20' i" = 1,-0" S ROOM 51 & 52 EXCAVATION GAMMA C:)
Scale Meters SMUD & BETA SCAN MEASUREMENT LOCATIONS SACRAMENTO MUNICIPAL UTILITY DISTRICT F8130732-Mi 0 1 2 3
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Scale Meters *SMUD SACRAMENTO MUNICIPAL LOOSE SURFACE MEASUREMENT POINTS UTILITY DISTRICT F8130732-M2 0 1 9 3 flWG: 813000.02c SHEET4 0F4 TCHLL 11
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- SMUD SACRAMENTO MUNICIPAL BETA SCAN MEASUREMENT LOCATIONS 0 1 UTILITY DISTRICT F8130732-M3 2 3 .QI-PP:T1I l~I T(¢I-HII I
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Attachment 2 Instrumentation July 9, 2008 Survey Unit F8130732
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; 175834 43-68B; 190482 433 1033 M2350; 149794 43-68/5B; 149103 433 1033 M2350; 149794 43-116-1B; 256005 796 3258 M2350; 175834 43-116-IB; 190642 796 3258 N/A ~5.9 dpm at, N Tennelec; 0401171 N/A 5 dpm 11.7 pmN/A
[
4890 Cs-137 Co-60 InSpector 1000 10054579 N/A 2160 2160 Co-60 The scan and static MDC's provided represent the most conservative MDC values for the survey conducted.
Table 2-2. Investigation Criteria and DCGL Parameter Vailue (dpm/100 cm 2 )
Investigation Criteria - Direct 176300 Investigation Criteria- Scan 176300 DCGLw 43000 DCGLEMC 176300 Page 2 of 2 Att. 2 Instrumentation F8130732
Attachment 3 Investigation July 9, 2008 Survey Unit F8130732 (none required)
Attachment 4 Data Assessment July 9, 2008 Survey Unit F8130732
CD F8130732 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/1 00cm2 16,000 14,000 CD 12,000 CD 10,000 I
4-8,000 6,000 4,000 00 2,000 1836 wD Cj) 0 0 20 40 60 80 100 Percentile w1
' Direct Measurements (dpm/100cm2) -median - - - 75th Percentile .... 50th Percentile Ili
0C FBI 30732 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpmll00cm' 20000 15000 0 E
Uo - - - - - - - - - - - - *- * = - - * - -S 11271 10000 Co 0
5000 1 - - - -- - -- -
2331 0
-5000
-600E
-10000 00000000000000000001%cW0 000 0 0000 C CO0 0OOCCO 0 COC0 Measurement Locations 00 C) o Gross Activity - Average - - "+3StDev" - - "3StDev
CD F81'30732 Gross Activity Frequency Plot 0
DCGL = 43000 dpm/1 00cm 2 16 15 C (D) 14 (D 1 2 .- ;-
LL 101 3 " ........... .
109 ~ , ,
Bis- perEd au (dpm/lO ;cm2)
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