ML090850559
| ML090850559 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 08/20/2008 |
| From: | Frank G Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097 | |
| Download: ML090850559 (21) | |
Text
Rancho Seco Final Status Survey Summary Report August 20, 2008 Turbine Building High Pressure Pedestal Survey Unit F8261005 Prepared By:
Reviewed By FSS Engineer Lead FSS Engineer Date:
2*6iý_
Date:
Approved By:
Date:
2-
-7 Dismantlement derinten dent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8261005, Turbine Building High Pressure Pedestal Survey Unit
Description:
Operating History: The reinforced concrete and steel structure contained the turbine-generator and supporting systems. The building contained five main elevations. 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.
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 in the condenser pit elevation showed a mean gross activity -level of 3077 dpm/1 00 cm 2 and a maximum value of 24,900 dpm/100 cm 2. Direct measurements on the grade elevation showed a mean 2
2 gross activity level of 2,035 dpm/100 cm and a maximum value of 6,980 dpm/100 cm2.
Direct measurements on the mezzanine elevation showed a mean gross activity level of 1,566 dpm/100 cm2 and a maximum value of 2,626 dpm/100 cm 2. Direct measurements on the +40' elevation showed a mean qross activity level of 2,843 dpm/100 cm 2 and a maximum value of 3,615 dpm/100 cm. Direct measurements on the building exterior showed a mean gross activity level of 1,984 dpm/1 00 cm2 and a maximum value of 10,312 dpm/100 cm2. Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the interior of the turbine building was determined to be Class 1, 2, & 3 areas and the exterior was a Class 3.
HSA Events: None Page 2 of 9 FSS Summary Report F8261005
Survey Area Classification 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 73 m2 were scanned for approximately 31% 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 3 of 9 FSS Summary Report F8261005
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:
F826 Survey Unit:
Class:
SU Area (m2):
Evaluator:
DCGL (dpm/100 cm2):
Area Factor:
Design DCGLemc (dpm/lO0 cm2):
LBGR (dpm/100 cm 2):
Design Sigma (dpm/100 cm2):
Type I Error:
Type II Error:
Predominant Nuclide:
Sample Area (m2):
Scan Area (M2):
Scan Coverage (%):
- ZlI, ZJ-P :
Sign P:
Calculated Relative Shift:
Relative Shift Used:
N-Value:
Design N-Value + 20%:
Design Min Samples N:
. Grid Spacing L:
1005 2
236.5 Gary Frank 43000 N/A N/A 21500 1316 0.05 0.05 Cs-137 16.9 73 31%
1.645 1.645 0.99865 16.3 3
11 14 14 4.1 Turbine Building High Pressure Pedestal 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 4 of 9 FSS Summary Report F8261005
Survey Results:
A total of 15 direct measurements were made in F8261005. 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 2347 to 7827 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 cmr)
F8261005-CO001 BD F8261005-CO002BD F8261005-CO003BD F8261005-CO004BD F8261005-CO005BD F8261005-CO006BD F8261005-CO007BD F8261005-CO008BD F8261005-CO009BD F8261005-COOIOBD F8261005-CO01 I BD F8261005-CO01 2BD F8261005-CO013BD F8261005-CO014BD F8261005-CO01 5BD Mean:
Median:
Standard Deviation:
Ranqe:
1598 1416 1463 1525 1509 1411 1618 1530 1675 1437 1603 1458 1416 1598 1535 1520 1525 85 1411 -1675 Page 5 of 9 FSS Summary Report F8261005
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2)
F8261005C0001SM 0.34 F8261005C0002SM
-2.24 F8261005C0003SM
-3.53 F8261005C0004SM
-0.95 F8261005C0005SM
-0.95 F8261005C0006SM
-2.24 F8261005C0007SM
-0.95 F8261005C0008SM
-0.95 F8261005C0009SM
-0.95 F8261005C0010SM
-3.53 F8261005C0011SM 1.64 F8261005C0012SM 0.34 F8261005C0013SM
-0.95 F8261005C0014SM
-2.24 F8261005C0015SM 4.22 Mean:
-0.86 Median:
-0.95 Standard Deviation:
1.98 Range:
-3.53 to 4.22 Page 6 of 9 FSS Summary Report F8261005
Survey Unit Data Assessment:
The survey design required 15 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 7 of 9 FSS Summary Report F8261005
Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm 2):
N/A Ambient Background Used (dpmn100 cm2):
N/A Average Ambient BKG = 0 Actual Direct Measurements (N):
15 Median (dpm/100 cm2):
1525 Mean (dpm/100 cm 2):
1520 Direct Measurement Standard Deviation 85 (dpm/100 cm2):
Total Standard Deviation (dpm/100 cm 2):
85 Based on samples and backgrounds.
Maximum (dpm/100 cm2):
1675 Material Type:
N/A Background Subtract Not Applied Sign Test Final N Value:
15 S+ Value:
15 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 8 of 9 FSS Summary Report F8261005
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, 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 43000 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 F8261005 meets the release criteria of I OCFR20.1402.
Page 9 of 9 FSS Summary Report F8261005 Maps August 20, 2008 Survey Unit F8261005
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Map F8261005-M1, Turbine Buiiding High Pressure Pedestal O
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9.0-8.5-8.0 -
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North Column Looking South 1105 ft2 102.7 m 2
West Column Looking ast 720 ft2 66.9 m2 ITI 00 CD F8261005-M3
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C~C Measurements in meters 0 Random Start at 7 WE and 10 SN.
East Column Looking West 720 ft 2
66.9m2 North Column Looking South 1105 ft2 -
102.7 ml West Column Looking ast 720 ft2 66.9 m2 (00 O
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(-A F8261005-M4 Instrumentation August 20, 2008 Survey Unit F8261005
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; 203486 43-68B; 190476 433 1033 M2350; 149789 43-68B; 161415 433 1033 Tennelec; 0401171 N/A 6 dpm a, 12 dpmr N/A Table 2-2. Investigation Criteria and DCGL
,Value Param eter V l eC 2
(dpm/100 cm2)
Investigation Criteria - Direct 43000 Investigation Criteria - Scan 43000 DCGLw 43000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8261005 Investigation August 20, 2008 Survey Unit F8261005 (none required)
Data Assessment August 20, 2008 Survey Unit F8261005
F8261005 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/1 00cm2 1,700 1,650*
>, 1,500
.1,550 z*0*
IC*2 CD) 01,450 17400-1,350 -1 0
20 40 60 80 100 Percentile Direct Measurements (dpm/100cm2)
-median
- -75th Percentile 50th Percentile C)_.
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Fo 8261005 Gross Activity Sample Results Scatter Plot A*
DCGL = 43000 dpml001cma
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1774 160 0
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Measurement Locations ro oHGross Activity Average -
"+3StDev"- -
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ýA F8261005 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 C-I 6
5 4
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F::
CO Bins - Upper End Value (dprrVl 00cm2)