ML082620078

Final Status Survey Summary Report June 26, 2008 West Heat Removal Cooler Room East of Column N, Room 052 Floor and Lower Walls Survey Unit F8130761

ML082620078
Person / Time
Site:	Rancho Seco
Issue date:	06/26/2008
From:	Stein M Sacramento Municipal Utility District (SMUD)
To:	NRC/FSME
References
F8130761, MPC&D 08-064
Download: ML082620078 (26)

Text

Rancho Seco Final Status Survey Summary Report June 26, 2008 West Heat Removal Cooler Room East of Column N, Room 052 Floor and Lower Walls Survey Unit F8130761 Prepared By:

Date:

FSS Engineer Reviewed By:

Date:"

42 Lead FSS Engineer Approved By:

2 Date:

Dismantlement S erintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8130761, West Heat Removal Cooler Room East of Column N, Room 052 Floor and Lower Walls Survey Unit

Description:

Operating History: The West Heat Removal Cooler Room is located on the -20' elevation of the Auxiliary Building. The Auxiliary Building is a reinforced concrete structure that, during power operations, contained the Radwaste processing and supporting systems.

The building has six main elevations. Residual levels of surface radioactivity were detected on all interior elevations 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 taken on each interior elevation of the Auxiliary Building. These measurements confirmed the presence of plant-derived radionuclides. Direct measurements taken on the -20' elevation, showed a mean gross activity level of 247,831 dpm/l 00 cm 2 and a maximum value of 10,080,000 dpm/l100 cm 2.

Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the interior surfaces of the Auxiliary Building were determined primarily to be a Class I for the floors and lower walls (bottom 2 meters of the walls), and Class 2 for the upper walls and ceiling. Inside the West Heat Removal Cooler Room there were a number of areas on the floor and lower walls where the gross surface activity levels were higher than the DCGL prior to remediation. Therefore, a Class 1 final status survey was performed on the floor and lower walls of the West Heat Removal Cooler Room East 'of Column N, Room 052.

HSA Events: HSAReport 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 150 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 F8130761

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

F813 West Heat Removal Cooler Room East of Column N, Room 052 Floor and Lower Walls Survey Unit:

0761 Structure Surface Class:

1 LTP Table 5-4 SU Area (m2):

150 Evaluator:

Michael Stein DCGL (dpm/100 cm2):

43000 Gross Activity DCGL Area Factor:

3.6 Class 1 Design DCGLemc 154800 Class 1 (dpm/100 cm 2):

LBGR (dpm/100 cm2):

21500 Default = 50% DCGL Design Sigma (dpm/100 cm2):

12035 Type I Error:

0.05 Type II Error:

0.05 Predominant Nuclide:

Cs-137 Sample Area (m2):

6.8 Class 1 Scan Area (m2):

150 Scan Coverage (%):

100%

Class I Zji. :

1.645 Zi-p :

1.645 Sign P:

0.955435 Calculated Relative Shift:

1.7 Relative Shift Used:

1.7 Uses 3.0 if Relative Shift is

>3 N-Value:

14 Design N-Value + 20%:

.17 NUREG-1575 Table, 5-5 Design Min Samples N:

22 Class 1 Grid Spacing L:

2.6 Class 1 Page 3 of 8 FSS Summary Report F8130761

Survey Results:

A total of 22 direct measurements were made in F8130761. The results including mean, median, standard deviation and range areshown in Table 2. All direct measurements were less than the DCGL. Two of the beta scan measurement locations indicated areas of elevated activity. Beta scan activity ranged from 4,225 to 999,149 dpm/100 cm2, based on a surveyor efficiency of 0.5 and no background subtracted. One of the gamma scan measurements indicated an area of elevated activity. Gamma scan activity ranged from 22,973 to 164,032 dpm/100 cm 2 Cs-137. One of the measurements detected 6,190 dpm/100 cm 2 Co-60. The MDCs for the gamma scan measurements were 4,090 to 5,250 dpm/100 cm 2 for Co-60 and 4,260 to 5,210 dpm/100 cm 2 for Cs-137. Scan measurement locations for both beta and gamma emissions are identified in Attachment 1 of this report.

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 Activit (dpm/100 cm F8130761-CO001BD 1810 F8130761-CO002BD 1816 F8130761-CO003BD 2007 F8130761-CO004BD 2044 F8130761-C0005BD 3470 F8130761-CO006BD 2106 F8130761-CO007BD 2749 F8130761-CO008BD 1919 F8130761-CO009BD 2002 F8130761-Co01 OBD 2153 F8130761-CO011BD 1982 F8130761-CO012BD 2350 F8130761-Co013BD 1556 F8130761-CO014BD 1572 F8130761-CO015BD 1551 F8130761-Co016BD 1847 F8130761-CO017BD 2412 F8130761-CO018BD 1634 F8130761-CO019BD 2308 F8130761-CO02OBD 1525 F8130761 -C0021 BD 1992 F8130761-CO022BD 1592 Mean:

2018 Median:

1987 Standard Deviation:

455 Range:

1525-3470 Page 4 of 8 FSS Summary Report F8130761

Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpmllO0 cm 2)

F8130761 COO SM F8130761CO002SM F8130761CO003SM F8130761C0004SM F8130761 C0005SM F8130761 C0006SM F8130761 C0007SM F8130761CO008SM F8130761 C0009SM F8130761C0010SM F8130761C0011SM F8130761CO012SM F8130761CO013SM F8130761CO014SM SF8130761CO015SM F8130761CO016SM F8130761CO017SM F8130761CO018SM F8130761CO019SM F8130761 C0020SM F8130761 C0021 SM F8130761 C0022SM Mean:

Median:

Standard Deviation:

Range:

17.13 35.21 26.17 22.3 17.13 35.21 9.38 22.3 17.13 27.46 15.84 5.51 2.93 9.38 8.09 9.38 26.17 31.34 54.59 6.8 18.42 2.93 19.13 17.13 12.73 2.93 to 54.59 Page 5 of 8 FSS Summary Report F8130761

Survey Unit Data Assessment:

The survey design required 22 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 F8130761

Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm 2):

N/A Ambient Background Used (dpmlO00 cm2):

N/A Average Ambient BKG = 0 Actual Direct Measurements (N):

22 Median (dpm/100 cm 2):

1987 Mean (dpm/100 cm 2):

2018 Direct Measurement Standard Deviation 455 (dpm/100 cm 2):

Total Standard Deviation (dpm/O00 cm 2):

455 Based on samples and backgrounds.

Maximum (dpm/100 cm 2):

3470 Material Type:

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

22 S+ Value:

22 Critical Value:

15 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 F8130761

Survey Unit Investigations and Results:

An investigation was required for two beta scan measurements (CO099BS and CO 136BS) and one gamma scan measurement (COOO1GS) as indicated in Attachment 3.

Investigation of the beta scan measurement areas resulted in the decision to perform additional remediation. The investigation results in Attachment 3 represent the residual radioactivity levels achieved after additional remediation. No additional remediation was performed at the elevated gamma scan measurement location. The EMC unity rule was not exceeded as shown in Table 3-1.

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 unitaverage 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 cm 2 and none of the removable surface activity measurements exceeded 10% of the DCGL.

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 F8130761 meets the release criteria of 10CFR20.1402, Page 8 of 8 FSS Summary Report F8130761 Maps June 26, 2008 Survey Unit F8130761

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-1I-Il Instrumentation June 26, 2008 Survey Unit F8130761

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

Model; Serial No.

(dpmll00 cm2 )

(dpm/100 cmr)

M2350; 180733 43-98B; 148638 1400 2520 M2350; 180733 43-94; 148620 1610 2800 M2350; 149789 43-68B; 161397 433 1033 M2350; 142507 43-68B; 160781 433 1033 M2350; 193715 43-68B; 160703 433 1033 M2350; 142509 43-68B; 160696 433 1033 M2350; 193700 43-68B; 160691 433 1033 M2350; 193715 43-116-1B; 190643 796 3258 Tennelec; 0401171 N/A 5.9 dpma, N/A 11.7 dpmf3 5210 Cs-137 InSpector 1000 10054579 N/A 5250 Co-60 5250 Co-60 The scan and static MDC's provided represent the most conservative MDC values for the survey conducted.

Table 2-2. Investigation Criteria and DCGL Value Parameter (dpm/100 cm 2)

Investigation Criteria - Direct 154800 Investigation Criteria - Scan 154800 DCGLw 43000 DCGLEMC 154800 Page 2 of 2 Att. 2 Instrumentation F8130761 Investigation June 26, 2008 Survey Unit F8130761

Table 3-1 Survey Unit Investigation Investigation Initial Value Investigation Elevated Area Investigation DCGLemc Grid Level (cpm)

(cpm)

Result (cpm)

Area Factor DCGLemc Result Unity l

et (M2)

F(dpm/lOOcm

2)

Fraction C0099BS 21,024 30,979 3,011 N/A N/A N/A 22,088 0.00 C0136BS 21,024 136,200 1,042 N/A N/A N/A 7,644 0.00 Investigation Initial Value Investigation Elevated Area Investigation Grid Level

'd/100 2 )

Result Area DCGLemc

-Result (dpm/lOOcm2) (dP (dpm/lOOcm2)

(Mi2)

(dpm/OOcm2)

C0001GS 154,800 170,222 170,222

<0.5 25.9 1,113,700 170,222 0.15 Survey Unit Remainder DCGL =

SU Mean =

0.05 43,000 2,018 EMC Unity Sum 0.20 All of the grids above were initially greater than DCGLemc. Investigation of grids C0099BS and C0136BS resulted in the decision to perform additional remediation. The investigation results above represent the residual radioactivity levels after additional remediation. No additional remediation was performed at the elevated gamma scan measurement location of C0001GS. The area factor for Co-60 was used in order to be conservative.

Page 2 of 2 Att. 3 Investigation F8130761

.Data Assessment June 26, 2008 Survey Unit F8130761

Fr 0D 00 F8130761 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/1 00cm2 3.

4,000 3,500 3,000 2,500 2,000 1,500 1,000 500 0

1987 0

20 40 60 Percentile 80 100 Direct Measurements (dpm/100cm2) -

median --

75th Percentile - --

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0ý1 F8B30761 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpmtl00cm2 r.*

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