ML081610236
| ML081610236 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 02/06/2008 |
| From: | Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| References | |
| MPC&D 08-032 | |
| Download: ML081610236 (18) | |
Text
{{#Wiki_filter:Rancho Seco Final Status Survey Summary Report February 6, 2008 Rooms 11512031315 Elevator Shaft Survey, Unit F8131031 Prepared By.*5 L-- Date:- Z SFSS in Reviewed By: Date: _ Lead FiS Engineer Approved By: I Date: Dismantlement Superintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit: F8131031, Rooms 115/203/315 Elevator Shaft 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 cm 2 and a maximum value of 5,720,000 dpmr/100 cm2. Direct measurements on the -29' elevation showed amean gross activity level of 544,756 dpm/100 cm2 and a maximum value of 11,370,000 dpm/ 100 cm2. Direct measurements 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 cm2. 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 cm2. Direct measurements on the +20' elevation showed a mean gross activity level of 85,408 dpm/l00 cm 2 and a maximum value of 1,900,000 dpm/1 00 cm 2. Direct measurements on the +40' elevation showed a mean gross activity level of 3,288 dpm/100 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!l100 cm 2 and a maximum value of 2,990 dpm/1 00 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 160 m2 were scanned for approximately 80%. 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 F8131031
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F813 Rooms 115/203/315 Elevator Shaft Structure Surface LTP Table 5-4 Survey Unit: Class: SU Area (m2): Evaluator: DCGL (dpm/100 cm2): Area Factor: Design DCGLemc (dpm/l 00 cm 2): 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: 1031 2 199 Gary Frank 43000 N/A N/A 21500 6935 0.05 0.05 Cs-137 enter value 160 80% 1.645 1.645 0.99865 3.6 3 11 14 14 3.7 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 3 of 8 FSS Summary Report F8131031
Survey Results: A total of 15 direct measurements were made in F8131031. 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 1810 to 5759 dpm/100 cm 2, based on a surveyor efficiency of 0.5 and no background subtracted. ISOCS scan activity on walls and ceiling ranged from 81.6 to 688 dpm/100cm 2 for Cs-137, with all scans MDA for Co-60 with a range from 71.6 to 505 dpm/1 00cm 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. Table 2. Direct Measurement Results Measurement ID Gross Activit (dpm/100 cm F8131031-COOOIBD F8131031-CO002BD F8131031-CO003BD F8131031-CO004BD F8131031-CO005BD F8131031 -CO006BD F8131031-CO007BD F8131031-CO008BD F8131031-CO009BD F8131031-CO01OBD F8131031-CO011BD F8131031-CO012BD F8131031--Co013BD F8131031-CO014BD F8131031--Co015BD Mean: Median: Standard Deviation: Range: 1089 1250 1198 1344 1504 1380 1276 1380 1333 1255 1069 1312 1146 1203 1271 1267 1271 116 1069-1504 Page 4 of 8 FSS Summary Report F8131031
Table 3. Removable Surface Activity Results Measurement ID Surface Beta, Activity (dpm/100 cm 2) F8131031COOOISM 0.34 F8131031C0002SM -4.82 F8131031CO003SM 2.93 F8131031CO004SM 4.22 F8131031C0005SM 6.8 F8131031 C0006SM 6.8 F8131031C0007SM -2.24 F8131031 C0007SM -0.95 F8131031 C0008SM -2.24 F8131031C0009SM -2.24 F8131031CO010SM 15.84 F8131031 C0011 SM -3.53 F8131031C0012SM 0.34 F8131031CO013SM -0.95 F8131031C0014SM -3.53 F8131031C0015SM 5.51 Mean: 1.39 Median: -0.3 Standard Deviation: 5.38 Range: -4.82 to 15.84 Page 5 of 8 FSS Summary Report F8131031
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 Page 6 of 8 FSS Summary ReportF1301 F8131031
Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm2): 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): 1271 Mean (dpm/100 cm2): 1267 Direct Measurement Standard Deviation 116 (dpm/100 cm 2): Total Standard Deviation (dpm/100 cm 2): 116 Based on samples and backgrounds. Maximum (dpm/100 cm 2): 1504 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 F8131031
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 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 wasproperly 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 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 F8131031 meets therelease criteria of IOCFR20.1402. Page 8 of 8 FSS Summary Report F8131031
Attachment I Maps February 6, 2008 Survey Unit F8131031
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00 C) Instrumentation February 6, 2008 Survey Unit F8131031
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; 142509 43-68B; 160699 433 1033 Tennelec; 0401171 N/A 5.9 dpm o N/A 11.7 dpm Table 2.1, Survey Unit Instrumentation Detector MDC Instrument Serial No. (dpm/1OOcm 2) 163 Cs-137 ISOCS 1983920 163 Co-60 153 Co-60 Table 2-2. Investigation Criteria and DCGL Value Param eterV a u C M (dpm/100 cm2) Investigation Criteria - Direct 43000 Investigation Criteria - Scan 43000 DCGLw 43000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8 131031 Investigation February 6, 2008 Survey Unit F8131031 (none required) Data Assessment February 6, 2008 Survey Unit F8131031
0 CD, ý4 F8131031 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpml1OOcm 2 R> S QJ 1,600 1,400 1,200 1,000 800 600 1271 400 200 0 0 20 40 60 80 100 It 00 Percentile c Direct Measurements (dprn/l00cmr2) -- median - - - 75th. Percentile 50th Percentile
-o 0 A' F81 31031 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpml1 00cm 2 A C/I 00 Cd, O-A -/A a -A. 1800 1600 E 1400 o 1200 E 1000 800 r600-t; 400 200 0 o C, 0 00 0 0 0 -C o" N0qV L l o C ) V W 0 0 0D 0 0 -3 = 3 3 3 = = -3 -0 -V -V %--I V-- I I 1. 1 I I I I I I I I I - I o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o3 0 0 0 0 0 0m 0 0 0 0 03 0 0 0 00 U U U U U U U U U U 0 U O Measurement Locations 0 Gross Activit-Average... ".+3StDev" - "-3StDev"I 1616 1267 1 919
(D .41 00 C> ~r1 00 F81 31031 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 0 t-- 0: 7 6 5 4 3 2 1 0 (0 co 1,-- "a o0 N O "O Bins - Upper End Value (dpmil00crn2)}}