ML081610165

Final Status Survey Summary Report, April 6, 2008, Misc. Waste Tank Pump Room, Room 16, Survey Unit F8130181

ML081610165
Person / Time
Site:	Rancho Seco
Issue date:	04/06/2008
From:	Ellen Brown Sacramento Municipal Utility District (SMUD)
To:	NRC/FSME
References
F8130181
Download: ML081610165 (27)

Text

Rancho Seco Final Status Survey Summary Report April 6, 2008 Misc. Waste Tank Pump Room, Room 16 Survey Unit F8130181 Prepared By:

&/.

Date: 4 /6/z o0 D/

Date: *'/2j Ž'1 Reviewed By:

LeaeFSS E ineer" Approved By:

-'i Date:_ ________

Dismantlement Superintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F813018 1, Misc.- Waste Tank Pump Room, Room 16 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/100 cm 2. Direct measurements on the -29' elevation showed a mean gross activity level of 544,756 dpm/100 cm 2 and a maximum value of 1.1,370,000 dpm/100 cm2. Direct measurements on the -20' elevation showed a mean gross activity level of 247,831 dpmr/100 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 cm2 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/100 cm2 and a maximum value of 1,900,000 dpm/100 cm 2. Direct measurements on the +40' elevation showed a mean gross activity level of 3,288 dpm/100 cm2 and a maximum value of 24,781 dpmr/100 cm 2. Direct measurements on the building exterior, including the mezzanine roof, showed a mean gross activity level of 1,897 dpm/l100 cm2 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 Designi 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 114 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 241 and 2-2 in Attachment 2.

Page 2 of 8 FSS Summary Report F8130181

Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:

F813 Survey Unit:

Class:

SU Area (rn):

Evaluator:

DCGL (dpm/100 cm 2):

Area Factor:

Design DCGLemc (dpm/100 cm 2):

LBGR (dpm/100 cm 2):

Design Sigma (dpm/100 cm 2):

Type I Error:

Type II Error:

Predominant Nuclide:

Sample Area (r2)

Scan Area (M2):

Scan Coverage (%):

Zj-" :

Sign P:

Calculated Relative Shift:

Relative Shift Used:

N-Value:

Design N-Value + 20%:

Design Min Samples N:

Grid Spacing L:

0181 1

114 Erin L. Brown 43000 3.4 146200 21500 12035 0.05 0.05 Cs-137 6.6 114 100%

1.645 1.645 0.955435 1.7 1.7 14 17 17 2.5, Misc. Waste Tank Pump Room, Room 16 Structure Surface LTP Table 5-4 Gross Activity DCGL Class I Class 1 Default = 50% DCGL Class 1 Class 1 Uses 3.0 if Relative Shift is

>3 NUREG-1575 Table 5-5 Class 1 Class 1 Page 3 of 8 FSS Summary Report F8130181

Survey Results:

A total of 21 direct measurements were made in F8130181. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. Three of the scan measurements indicated areas of elevated.

activity. Scan activity ranged from 1532 to 242239 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/lO0 cm F8130181-CO001BD F8130181 -CO002BD F8130181 -CO003BD F8130181-C0004BD F8130181-CO005BD F8130181 -CO006BD F8130181-CO007BD F8130181 -CO008BD F8130181 -CO009BD F8130181-CO01OBD F8130181 -COOIIBD F8130181 -CO01 2BD F8130181 -Co01 3BD F8130181-CO014BD F8130181 -CO01 5BD F8130181-CO016BD F8130181-CO017BD F8130181 -Co01 8BD F8130181-CO019BD F8130181 -CO02OBD F8130181 -C0021BD Mean:

Median:

Standard Deviation:

Range:

1971 1836 1935 2044 1831 2179 2142 2210 2018 23234 10416 1805 1748 2319 5836 4876 2085 1919 5099 1919 1795 3867 2044 4907 1748-23234 Page 4 of 8 FSS Summary Report F8130181

Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2)

F8130181 C0001 SM

-2.24 F8130181 C0002SM

-2.24 F8130181 C0003SM 2.93 F8130181 C0004SM

-0.95 F8130181C0005SM 9.38 F8130181C0006SM 8.09 F8130181 C0007SM 17.13 F8130181C0008SM

-0.95 F8130181C0009SM

-3.53 F8130181CO010SM 26.17 F8130181CO011SM 46.84 F8130181C0012SM 1.64

-F8130181C0013SM 0.34 F8130181CO014SM 9.38 F8130181COO15SM 24.88 F8130181C0016SM 11.97 F8130181C0017SM 2.93 F8130181C0018SM

-3.53 F8130181C0019SM 58.46 F8130181 C0020SM

-3.53 F8130181 C0021 SM

-2.24 Mean:

9.57 Median:

2.93 Standard Deviation:

16.95 Range:

-3.53 to 58.46 Page 5 of 8 FSS Summary Report F8130181

Survey Unit Data Assessment:

The survey design required 21 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 F8130181

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):

21 Median (dpm/100 cm'):

2044 Mean (dpm/100 cm2):

3867 Direct Measurement Standard Deviation 4907 (dpm/100 cm2):

Total Standard Deviation (dpm/100 cm2):

4907 Based on samples and backgrounds.

Maximum (dpm/100 cm 2):

23234 Material Type:

N/A Background Subtract Not Applied Sign Test Final N Value:

21 S+ Value:

21 Critical Value:

14 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 F8130181

Survey Unit Investigations and Results:

An investigation was required for three scan measurements as indicated in Attachment 3.

Investigation of the areas resulted in the decision to perform additional remediation. The investigation results in attachment 3 represent the residual radioactivity levels achieved after additional remediation.

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. Three potential areas of elevated activity were detected as indicated in Attachment 3.

==

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 cm2 and none of the removable surface activity measurements exceeded 10% of the DCGL. An investigation was required for three scan measurements as indicated in Attachment3.

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 F8130181 meets the release criteria of 10CFR20.1402.

Page 8 of 8 FSS Summary Report F8130181 Maps April 6, 2008 Survey Unit F8130181

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Table 2-1. Survey Unit Instrumentation Instrument Detector MDC Static MDC Scan Model; Serial No.

Model; Serial No.

(dpm/100 cm2 )

(dpm/100 cm 2)

M2350; 180733 43-98B; 148638 N/A 820 M2350; 175834 43-68B; 190482 433 1033 M2350; 175834 43-116-IB; 190642 N/A 3258 Tennelec; 0401171 N/A 5.9 dpm a, N/A 1

11.7 dpmn Table 2-2. Investigation Criteria and DCGL Value Parameter Valuc (dpm/100 cm2)

Investigation Criteria - Direct 146200 Investigation Criteria - Scan 146200 DCGLw 43000 DCGLEMC 146200 Page 2 of 2 Att. 2 Instrumentation F8130181 Investigation April 6, 2008 Survey Unit F8130181

Table 3-1 Survey Unit Investigation T Investigation Elevated

]

Investigation DCGLemc ResuArea DCGLemc Result Unity Grid Investigation Initial Value Result Eeae Area (in 2), Factor U0mniFatio Level (cpm)

(cPm) cArea (m2)

Factor (dpm/

C0043BS 19,000 25,203 5,052 N/A N/A 146,200 37,061 0

C0091BS 19,000 33,021 3,140 N/A N/A 146,200 23,035 0

C0094BS 19,000 36,417 2,987 N/A N/A 146,200 21,912 0

SU Mean =

Survey Unit Remainder 43,000 3867 0.09 EMC Unity Sum 0.09 All of the grids above were initially greater than DCGLemc. Investigation of the areas resulted in the decision to perform additional remediation. The investigation results above represent the residual radioactivity levels after additional remediation.

Page 2 of 2 Att. 3 Investigation F8130181 Data Assessment April 6, 2008 Survey Unit F8130181

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