ML090890585
| ML090890585 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 07/04/2008 |
| From: | Andersen D Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097, F8260032 | |
| Download: ML090890585 (28) | |
Text
Rancho Seco Final Status Survey Summary Report July 4, 2008 Turbine Building (+) 0' El., Main Feed Pump Area Survey Unit F8260032 Prepared By: cs,. UADCt-- Date: 1/ I8 FSS Engineer Reviewed By: _______ Date: I jkjo Lead FSS Engineer Approved By: $ Date: _ 27 -
Dismantlement Sup intendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8260032, Turbine Building (+) 0' El., Main Feed Pump Area 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 3,077 dpm/100 cm 2 and a maximum value of 24,900 dpm!100 cm 2. Direct measurements on the grade elevation showed a mean gross activity level of 2,035 dpm/100 cm2 and a maximum value of 6,980 dpm/100 cm 2. Direct measurements on the mezzanine elevation showed a mean gross activity level of 1,566 dpm/100 cm 2 and a maximum value of 2,626 dpm/1 00 cm 2 . Direct measurements on the +40' elevation showed a mean gross activity level of 2,843 dpm/100 cm 2 and a maximum value of 3,615 dpm/100 cm 2 . Direct measurements on the building exterior showed a mean gross activity level of .1,984 dpm/100 cm 2 and a maximum value of 10,312 dpm/100 cm 2. 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.
During FSS surveys of F8260032 (Turbine Building (+) 0' El., Main Feed Pump Area, Class 2), beta measurements identified activity within a 1-meter by 5-meter area that exceeded the DCGL of 43,000 dpm/1 00 cm 2 . The area was subsequently removed from this survey package, remediated and reclassified as a Class 1 structure, based on the classification procedure (DSIP-0020). Final surveys of the Class 1 area will be performed undersurvey package F8260171.
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 100 m2 were scanned for approximately 54% 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 inTables 2-1 and 2-2 in Attachment 2.
Page 2 of 8 FSS Summary Report F8260032
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F826 Turbine Building (+) 0' El.,
Main Feed Pump Area Survey Unit: 0032 Structure Surface Class: 2 LTP Table 5-4 SU Area (m2): 186.2 Evaluator: D. Anderson DCGL (dpm/100 cm 2): 43,000 Gross Activity DCGL Area Factor: N/A Class 2 Design DCGLemc N/A Class 2 (dpm/1 00 cm 2):
LBGR (dpm/100 cm 2): 25,030 Adjusted Design Sigma (dpm/100 cm 2): 5,990 Type I Error: 0.05 Type II Error: 0.05 Predominant Nuclide: Cs-137 Sample Area (m2): 13.3 Class 2 Scan Area (M, 2): 100 Scan Coverage (%): 54% Class 2 1.645 ZIp: 1.645 Sign P: 0.99865 Calculated Relative Shift: 3 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 2 Grid Spacing L: 3.0 Class 2 Page 3 of 8 FSS Summary Report F8260032
Survey Results:
A total of 15 direct measurements were made in F8260032. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. Two of the beta scan measurements indicated areas of elevated activity. Scan activity ranged from 4,218 to 68,000 dpm/100 cm 2 , based on a surveyor efficiency of 0.5 and no background subtracted. The scan grids indicating elevated activity were removed from the survey unit, remediated and resurveyed under FSS Package F8260171. As left beta scan measurements ranged'from 4,218 dpm/100 cm 2 to 8,818 dpm/100 cm 2 . 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/lO0 cm F8260032-CO001 BD 2,552 F8260032-CO002BD 1,712 F8260032-CO003BD 1,577 F8260032-CO004BD 1,784 F8260032-CO005BD 1,644 F8260032-CO006BD 2,485 F8260032-CO007BD 2,329 F8260032-CO008BD 2,111 F8260032-CO009BD 1,930 F8260032-COOIOBD 2,288 F8260032-COOI11BD 2,770 F8260032-CO012BD 1,686 F8260032-CO013BD 1,924 F8260032-CO014BD 1,867 F8260032-CO01 5BD 2,039 Mean: 2,047 Median: 1,930 Standard Deviation: 365 Range: 1,577 - 2,770 Page 4 of 8 FSS Summary Report F8260032
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2)
F8260032C0001 SM -2.24 F8260032C0002SM -0.95 F8260032C0003SM 5.51 F8260032C0004SM 1.64 F8260032C0005SM 10.68 F8260032C0006SM -3.53 F8260032C0007SM -2.24 F8260032C0008SM -3.53 F8260032C0009SM 2.93 F8260032C0010SM -0.95 F8260032C0011SM 1.64 F8260032C0012SM -0.95 F8260032C0013SM -4.82 F8260032C0014SM -0.95 F8260032C0015SM 0.34 Mean: 0.17 Median: -0.95 Standard Deviation: 3.96 Range: -4.82 to 10.68 Page 5 of 8 FSS Summary Report F8260032
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 6 of 8 FSS Summary Report F8260032
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): 15 Median (dpm/100 cm 2): 1,930 Mean (dpm/100 cm 2): 2,047 Direct Measurement Standard Deviation 365 2
(dpm/100 cm ):
Total Standard Deviation (dpm/100 cm 2): 365 Based on samples and backgrounds.
2 Maximum (dpm/100 cm ): 2,770 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 7 of 8 FSS Summary Report F8260032
Survey Unit Investigations and Results:
Two investigations (scan grids 102 and 103) were required for the scan measurements and the results are reported in Attachment 3. As a result of the investigation measurements, Grids 102 through 106 were removed from the survey unit package and will be surveyed as a Class 1 structure under F8260171.
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. Two 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 cm 2 and none of the removable surface activity measurements exceeded 10% of the DCGL. Two 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 F8260032 meets the release criteria of 10CFR20.1402.
Page 8 of 8 FSS Summary Report F8260032
Attachment 1 Maps July 4, 2008 Survey Unit F8260032
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Il m~O L FwZD Location of Turbine Building inside the Industrial Area 00 .......
S Map F8260032-1, Turbine Building Main Feed Pump Area Location of Turbine Building at Rancho Seco site
7 89 10 11 12 13 0
11W Ki LIZ 14 00 N Map F8260032-2, Turbine Building Grade and Below Elevations Location of Main Feed Pump Area
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r////, HPPedestal North 111A V77/Pý~eetalI Nroth / /1 Red numbers denote specific vertical surfaces.
UT1 00j 0 0.5 1.0 1.5 2.0 Map F8260032-3, Turbine Building Main Feed Pump Area Distance in Meters Horizontal Surfaces Area Estimate: 1,363 sq. ft. - 126.6 sq. meters
03.-~. I 0Q 43 Looking North
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0 44 South LokJng South Looking East North Looking East Looking West South Lo[ West 41 Norho"i E or Lookisg West Looking North Looking East Looking West Look*ngNorth Looking East West South East South East West South West South East Looking South North West Looking North East Looking North West Looking North North West 08 Looking South F
West East 120 Looking South W- East It 00 C) 0 0.5 1t.0 1.5 2.0 Map F8260032-4, Turbine.Building Main Feed Pump Area Distance in Meters Vertical Surfaces Area Estimate: 641 sq. ft. - 59.6 sq. meters
Main Feed Pump Area Looking West Map F8260032-5, Turbine Building Main Feed Pump Area Views looking West and East Page 6.of 12 Att. I Maps F8260032
Main Feed Pump Ai g South (SW Corner)
Map F8260032-6, Turbine Building Main Feed Pump Area NW Corner and SW Corner Page 7 of 12 Att. 1 Maps F8260032
Main Feed Pump Area Looking North (N Corner)
... * ", I ,.r - I g boutn (,5t Corner)
Map F8260032r7, Turbine Building Main Feed Pump Area NE Corner and SE Corner Page 8 of 12 Att. 1 Maps F8260032
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Main Feed Pump Area Random Start Location
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FE E Distance in meters E E E from East border of C)~
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Uj Map F8260032-9, Turbine Building Main Feed Pump Area Beta Direct Measurements F8260032C0001BO to F8260032C0015BD 0 0.5 1.0 1.5 2.0 3.0 m by 3.0 m grid spacing Distance in Meters
CD' 00 C')
Map F8260032-10, Turbine Building Main Feed Pump Area Beta Scan Measurements F8260032C0001BS to F8260032C0101BS 0 0.5 1.0 1.5 2.0 Approximate Scan Area: 100 sq. meters Distance in Meters
78BS 77BS 76BS 75BS 74BS I 73BS 72BS L 0
79BS 67BS 68BS 69BS 70[S 8OBSEI 71 BS 81 BS E 66BS 65BS 64BS 63LB 62BS I
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82BS 58BS 59BS 61 BS I7BS M) U) 53BS m io I 2ýp's nBS JBS
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(-) 1.5' El. Li Map F8260032-11, Turbine Building Main Feed Pump Area Beta Scan Measurements
(+) O' El. LI Removed from survey unit:
0 0.5 1.0 1.5 2-0 F8260032C0102BS to F8260032C0106BS Distance in Meters
Attachment 2 Instrumentation July 4, 2008 Survey Unit F8260032
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; 193700 43-68B; 190294 433 1,033 Tennelec; 0401171 N/A 5.88 dpma, N/A Tennele_;_040117 ____ /A_____11.71 dpm]3 N/A Table 2-2. Investigation Criteria and DCGL Value ParameterVau (dpm/100 cmM2 )
Investigation Criteria - Direct 43,000 Investigation Criteria - Scan 43,000 DCGLw 43,000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8260032
Attachment 3 Investigation July 4, 2008 Survey Unit F8260032
Table 3-1 Survey Unit Investigation 1 Investigation measurements indicated activity exceeding the DCGL of 43,000 dpm/1 00 cm 2 for a Class 2 area. Grids 102 through106 were deleted from the survey unit and will be surveyed under FSS package F8260171.
Page 2 of 2 Att. 3 Investigation F8260032
Attachment 4 Data Assessment July 4, 2008 Survey Unit F8260032
F8260032 Gross DCGL Activity
= 43000 Sample dpm/100cm Results Quantile Plot 4,000 '757 3,500 * * * ,, .:'o.
3,000 < .
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~Percentile 5Direct Measurements (dpm/100cm2) - median - - 7te 5 i w i
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C F8260032 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpmrl00cm=
3500 3142 j0j' 3000 0
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F8260032 Gross Activity Frequency Plot DCGL = 43000 dpmn/1 00cm2 4
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0-N~ t o) 0-It 00 UO Bins - Upper End Value (dpm/1 00cm2) k)