ML091000375

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Final Status Survey Summary Report for August 20, 2008 North Diesel Generator Room (Class 1 Area) Survey Unit F8131212
ML091000375
Person / Time
Site: Rancho Seco
Issue date: 08/20/2008
From: Ellen Brown
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
Shared Package
ML090830613 List: ... further results
References
DPG 09-097, F8131212
Download: ML091000375 (19)
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{{#Wiki_filter:Rancho Seco Final Status Survey Summary Report August 20, 2008 North Diesel Generator Room (Class 1 Area) Survey Unit F8131212 Prepared By: *., &.-) Date: FSS Engineer Reviewed By, 61Jý'A A'ý Date: e -2 Lead FSS Engineer Approved By: Date: Dismantlement Superintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit: F8131212, North Diesel Generator Room Survey Unit

Description:

Operating History: The reinforced concrete structure contained the RadWaste processing and supporting systems. The building contained six 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. One report documented contamination of the auxiliary building roof. The roof was later replaced. 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 -47' elevation showed a mean gross activity level of 320,071 dpm/100 cm2 and a maximum value of 5,720,000 dpm/l100 cm 2. Direct measurements on the -29' elevation showed a mean gross activity level of 544,756 dpm/100 cm2 and a maximumvalue of 11,370,000 dpm/100 cm 2. Direct measurements on the - 2 0' elevation showed a mean gross activity level of 247,831 dpm/O00 cm 2 and a maximum value of 10,080,000 dpm/100 cm 2. Direct measurements on the grade elevation showed a mean gross activity level of 373,758, dpm/100 cm 2 and a maximum value of 5,800,000 dpm/100 cm 2. Direct measurements on the +20' elevation showed a mean gross activity level of 85,408 dpm/100 cm 2 and a maximum value of 1,900,000 dpm/l100 cm2. Direct measurements on the +40' elevation showed a mean gross activity level of 3,288 dpm/1 00 cm 2 and a maximum value of 24,781 dpm/100 cm 2. Direct measurements on the building exterior, including the mezzanine roof, showed a mean gross activity level of 1,897 dpm/100 cm 2 and a maximum value of 2,990 dpm/100 cm 2. (The roof had been replaced prior to the classification survey.) Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the interior of the auxiliary 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 12 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 F8131212

Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F813 North Diesel Generator Room Structure Surface LTP Table 5-4 Survey Unit: Class: SU Area (M2): Evaluator: - DCGL (dprnI1O0 cm2): Area Factor: Design DCGLemc (dpm/100 cm2): LBGR (dpm/100 cm 2): Design Sigma (dpm/100 cm 2): Type I Error: Type II Error: Predominant Nuclide: Sample Area (m2): Scan Area (M2): Scan Coverage (%): Sign P: Calculated Relative Shift: Relative Shift Used: N-Value: Design N-Value + 20%: Design Min Samples N: Grid Spacing L: 1212 12 Erin L. Brown 43000 17.1 735730 21500 6935 0.05 0.05 Cs-137 0.86 12 100% 1.645 1.645 0.99865 3.2 3 11 14 14 0.9 Gross Activity DCGL Class 1 Class 1 Default = 50% DCGL Class 1 Class I Uses 3.0 if Relative Shift is >3 NUREG-1575 Table 5-5 Class 1 Class 1 Page 3 of 8 FSS Summary Report F8131212

Survey Results: A total of 14 direct measurements were made in F8131212. 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 3347 to 7761 dpm/l100 cm 2, 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 cm) F8131212-CO001 BD F8131212-CO002BD F8131212*-CO003BD F8131212-CO004BD F8131212-CO005BD F8131212-CO006BD F8131212-CO007BD F8131212-CO008BD F8131212-CO009BD F8131212-CO01OBD F8131212-CO011BD F8131212-CO01 2BD F8131212-CO01 3BD F8131212-CO014BD Mean: Median: Standard Deviation: Range: 1727 1873 2013 1940 2049 1733 2132 2588 2511 2116 2215 2817 2339 2428 2177 2124 326 1727-2817 Page 4 of 8 FSS Summary Report F8131212

Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2) F8131212C0001SM F8131212CO002SM F8131212CO003SM F8131212CO004SM F8131212CO005SM F8131212CO006SM F8131212CO007SM F8131212CO008SM F8131212CO009SM F8131212C0010SM F8131212C001ISM F8131212C0012SM F8131212C0013SM F8131212CO014SM Mean: Median: Standard Deviation: Range: 6.8 5.51 1.64 1.64 5.51 0.34 4.22 2.93 -0.95 1.64 15.84 4.22 -2.24 0.34 3.39 2.28 4.43 -2.24 to 15.84 Page 5 of 8 FSS Summary Report F8131212

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 F8131212

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): 14 Median (dpm/100 cm 2): 2124 Mean (dpm/100 cm 2): 2177 Direct Measurement Standard Deviation 326 (dpm/100 cm 2): Total Standard Deviation (dpm/100 cm 2): 326 Based on samples and backgrounds. Maximum (dpm/100 cm 2): 2817 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: 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 ' F8131212

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. Therefore the EMC criterion was met.

== 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 F8131212 meets the release criteria of 10CFR20.1402. Page 8 of 8 FSS Summary Report F8131212 Maps August 20, 2008 Survey Unit F8131212

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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 1033 M2350; 193700 43-116-IB; 216072 N/A 3258 Tennelec; 0401171 N/A 5.9 dpm a, N/A 11.7 dpmf Table 2-2. Investigation Criteria and DCGL Parameter Value (dpmll.00 cm 2) Investigation Criteria - Direct 735730 Investigation Criteria - Scan 735730 DCGLw 43000 DCGLEMC 735730 Page 2 of 2 Att. 2 Instrumentation F8131212 Investigation August 20, 2008 Survey. Unit F8131212 (none required) Data Assessment August 20, 2008 Survey Unit F8131212

(n~ 0 (tI 00 F8131212 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/100cm2 3: 3,000 2,500 2,000 1,500 1,000 2124 500 0 0 20 40 60 80 100 Percentile Direct Measurements (dpm/100cm2) median - - -75th Percentile 50th Percentile

CD F8131212 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpmt100cm= 3500 3154 3000 E o 2500 -o 0 0 oo 'b'- -*2177 E 2000 - 0 0 0 1200 a Ž1000 (n CDa rc 500 0 1 t - I I.. I 1 t

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crQ 0 Cf2 0 C/) 0 F81 31212 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 3 a) L) 2 1 0 (N U-) 00 wO Bins - Upper End Value (dpm/1 00cm2) ...........}}

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