ML090890587
| ML090890587 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 06/24/2008 |
| From: | Andersen D Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097, F8260141 | |
| Download: ML090890587 (26) | |
Text
Rancho Seco Final Status Survey Summary Report June 24, 2008 Turbine Building (+) 0' El. South Floor Survey Unit F8260141 Prepared By: Date: 0/24/200?
FSS Engineer Reviewed By: - Date: I*-IA 100 Lead FSS Engineer Approved By: Date: 2 ?
Dismantlement Superintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8260141, Turbine Building (+) 0' El. South Floor 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 cm 2 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 cm 2 and a maximum value of 2,626 dpm/100 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 characterization surveys of F8260141 (Turbine Building (+) 0' El., South Floor, Class 2), beta measurements identified activity within a 4-meter by 4-meter area that exceeded the DCGL of 43,000 dpm/100 cm 2. The area was 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 F8260151.
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 496 m2 were scanned for approximately 51% 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 F8260141
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F826 Turbine Building (+) 0' El.
South Floor Survey Unit: 0141 Structure Surface Class: 2 LTP Table 5-4 SU Area (m2): 980.5 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/100 cm 2):
LBGR 2 (dpm/100 cm ): 39,052 Adjusted 2
Design Sigma (dpm/100 cm ): 1,316 Type I Error: 0.05 Type II Error: 0.05 Predominant Nuclide: Cs-137 Sample Area (m2): 70.1 Class 2 Scan Area 2 (M ): 496 Scan Coverage (%): 51% Class 2 Zl_* : 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: 8.3 Class 2 Page 3 of 8 FSS Summary Report F8260141
Survey Results:
A total of 14 direct measurements were made in F8260141. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. One ISOCS gamma scan measurement indicated a possible area of elevated activity (> 4,300 dpm/100 cm average Cs-137 activity for 12.56 m2 field of view). Seven additional ISOCS measurements were performed at the location using a reduced field of view (3.14 m 2) and were evaluated as shown in Table 3-1 of Attachment
- 3. The gamma scan activity for the survey unitranged from < 991 dpm/100 cm 2 Co-60 and < 1,250 dpm/100 cm2 to 10,408 dpm/100 cm2 Cs-137. 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/1O0 cm)
F8260141-CO001BD 1,172 F8260141 -CO002BD 1,193 F8260141-CO003BD 1,572 F8260141-CO004BD 1,717 F8260141-CO005BD 1,769 F8260141-CO006BD 1,800 F8260141-CO007BD 1,722 F8260141-CO008BD 1,857 F8260141 -CO009BD 1,810 F8260141 -CO01OBD 1,795 F8260141-CO011BD 1,758 F8260141-CO012BD 1,909 F8260141-CO013BD 1,945 F8260141 -CO01 4BD 1,753 Mean: 1,698 Median: 1,764 Standard Deviation: 236 Range: 1,172 - 1,945 Page 4 of 8 FSS Summary Report F8260141
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2 )
F8260141C0001SM 0.34 F8260141C0002SM -2.24 F8260141C0003SM -2.24 F8260141C0004SM -0.95 F8260141C0005SM 0.34 F8260141 C0006SM -4.82 F8260141 C0007SM -4.82 F8260141C0008SM -2.24 F8260141C0009SM -0.95 F8260141C0010SM -4.82 F8260141 C0011 SM -4.82 F8260141C0012SM -4.82 F8260141C0013SM -2.24 F8260141C0014SM -4.82 Mean: -2.79 Median: -2.24 Standard Deviation: 2.01 Range: -4.82 to 0.34 Page 5 of 8 FSS Summary Report F8260141
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 F8260141
Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm 2): N/A Ambient Background Used (dpm/100 cmr): N/A Average Ambient BKG 0 Actual Direct Measurements (N): 14 Median (dpm/100 cm 2): 1,764 Mean (dpm/100 cm 2): 1,698 Direct Measurement Standard Deviation 236 (dpm/100 cm 2):
Total Standard Deviation (dpm/100 cm 2): 236 Based on samples and backgrounds.
Maximum (dpm/100 cm 2 ): 1,945 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 F8260141
Survey Unit Investigations and Results:
One investigation (scan grid 26) was required for the scan measurements and the results are reported in Attachment 3. Seven additional ISOCS investigation measurements were performed with a reduced field of view and did not exceed the Investigation Level to detect a 100 cm 2 hot spot within the detector field of view (3.1 sq. meters).
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. One potential area of elevated activity was 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. One ISOCS investigation was performed but did not identify activity exceeding the Investigation Level for the reduced field of view.
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 F8260141 meets the release criteria of 10CFR20.1402.
Page 8 of 8 FSS Summary Report F8260141
Attachment 1 Maps June 24, 2008 Survey Unit F8260141
0 Location of Turbine Building inside the Industrial Area 00 Map F8260141-1, Turbine Building (+) 0' Elevation Location of Turbine Building at Rancho Seco, site
0 jZ11 Cj2 Map F8260141-2, Turbine Building Grade and Below Elevations Location of South Turbine Bldg (+) 0' Elevation Floor
7, Map F8260141-3, South Turbine Building (+) 0' El.
Area Estimate: 980.5 sq. meters (10,554.55 sq. ft.)
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I 0 1 2 3 4 Distance in Meters Page 4 of 10 Att. 1 Maps F8260141
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I ! I i- T, mlii ml I I'I t I I 5 2 4 6 8 10 12 14 16 20 22 24 26 28 30 N *---- Map F8260141-4, South Turbine Building (+) 0' Elevation Floor 0 1 Distance 2in Meters 3 4 Random Start Location Page 5 of 10 Att. I Maps F8260141
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E CD, Eo c E-2 Map F8260141-5, South Turbine Building (+) 0' Elevation Floor N Beta Direct Measurements F8260141C0001BD to F8260141C0014BD 0 1 2 3 4 Distance in Meters 8.3 sq. meter grid Page 6 of 10 Att. 1 Maps F8260141
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5.1im 22GS 23GS 24GS 25GS 26GS 27GS 28GS 9.1 m 2GGS] CG 5G4 FA17GS] 19GS 20GS 4G-U) E U) E-DStace*neteA TotaL_
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N 2.6 m F86014CFIGSS]t F826041000G E*<2 Bq ~ 1271G117 1"S F 2604C00G to F8611040GS GW 2.65 mq il fve 6ee Distance inMeesTtlSa L meters Ar :49 sq Page 7 of 10 Att. 1 Maps F8260141
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21.5 m 17.9 m 14.4 m - Distance in meters from South Wall Map F8260141-7, South Turbine Building (+) 0' Elevation Floor ISOCS Gamma Scan Measurements Location of F8260141C0006GS to F8260141C0009GS, 0
1 2 3 4 F8260141C0015GS to F8260141C0020GS Distance inMeters 12.57 sa. meter field of view Page 8 of 10 Att. I Maps F8260141
E 19.2 m 15.2 m 11.2 m 7.2 m from South Wall Map F8260141-8, South Turbine Building (+) 0' Elevation Floor ISOCS Gamma Scan Measurements N Location of F8260141 C010GS to F8260141 COO 14GS and 0 1 2 3 4 F8260141C0021GS Distance in Meters 12.57 sq. meter field of view Page 9 of 10 Att. I Maps F8260141
Map F8260141-9, South Turbine Building (+) 0' Elevation Floor N
- ISOCS Gamma Scan Measurements F8260141 C0041GS to F8260141 C0047GS o 1 2 33.14 sq. meter field of view Distance in Meters Page 10 of 10 Att. 1 Maps F8260141
Attachment 2 Instrumentation June 24, 2008 Survey Unit F8260141
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; 189089 43-68B; 161406 433 1,033 Tennelec; 0401171 N/A 5.88 dpm a, N/A 1 11.71 dpm P3 Table 2-2. Investigation Criteria and DCGL Value Parameter d (dpm/100 cm 2 )
aluec2 Investigation Criteria - Direct 43,000 Investigation Criteria - Scan (ISOCS average Cs-137 activity 4,300 for 12.5 m2 field of view)
Investigation Criteria - Scan (ISOCS average Cs-137 activity 12,600 for 3.1 M 2 field of view)
DCGLw 43,000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8260141
Attachment 3 Investigation June 24, 2008 Survey Unit F8260141
Table 3-1 Survey Unit Investigation Investigation Initial Value Investigation Investigation DCGLemC Grid Level (dpm/100 Result Elevated Area DCGLemc Result Unity (dpm/l 00 2 (dpm/lO0 Area (m 2) Factor 2 (dpmn/lOcm2) Fraction cm 2) cm) cm )
261 4,300 @ 2 6,030 (See Below) 12.57 N/A N/A N/A N/A meters 10,408 3.14 N/A N/A 10,408 0.00 8,368 3.14 N/A N/A 8,368 0.00 7,239 3.14 N/A N/A 7,239 0.00 2612,600 @ 1- N/A 4,809 3.14 N/A N/A 4,809 0.00 26 ~~meter ______
3,872 3.14 N/A N/A 3,872 0.00 1,466 3.14 N/A N/A 1,466 0.00 2,585 3.14 N/A N/A 2,585 0.00 Survey Unit Remainder DCGL = SU Mean = 0.04 43,000 1,698.
EMC Unity Sum 0.04 1Investigation Level for ISOCS measurements is based on detection of a 100 cm 2 hot spot at the DCGL value within the detector field of view. Should the average activity for an ISOCS measurement exceed the Investigation Level for the detector field of view, additional measurements are performed with a smaller detector field of view to determine if a hot spot exists that may exceed the DCGL.
Page 2 of 2 Att. 3 Investigation F8260141
Attachment 4 Data Assessment June 24, 2008 Survey Unit F8260141
CD F8260141 Gross Activity Sample Results Quantile Plot 0 DCGL = 43000 dpm/1 00cm2 3,000 -
2,500 -
4i-2,000 -
1764 CD ZI 3
1,500 -
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500 -
0 0 20 40 60 80 100 Percentile 00 tkj I
- Direct Measurements (dpm/100crn2) -median - - - 75th Percentile --- - 50th Percentile
a U) 6 F8260141 Gross Activity Sample Results Scatter Plot
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A DCGL = 43000 dpmIlOOcmn 3000 2500 27 Sm o m -m - - * - -f a w am a M a - - a - a - a oa a - - - 2406 E
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00 ON o Gross Activity - Average.- - -- &S..ev"- - "-.St.e..
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F8260141 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm 2 6
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