ML082620159

Final Status Survey Summary Report, July 14, 2008, Pump Alley Floor and Soil Walls, Survey Unit F8130421

ML082620159
Person / Time
Site:	Rancho Seco
Issue date:	07/29/2008
From:	Tallman D Sacramento Municipal Utility District (SMUD)
To:	NRC/FSME
References
MPC&D 08-064 F8130421
Download: ML082620159 (21)

Text

Rancho Seco Final Status Survey Summary Report July 14, 2008 Pump Alley floor and soil walls Survey Unit F8130421 Prepared By: Dan A. Tallman 4

Date: July 14, 2008 FSS Engine/er Reviewed By:

• LL Date: 7[

0 Lead FSS Engineer Approved By:

Date:

7-2-"o Dismantlement Superintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8130421, Pump Alley floor and soil walls Survey Unit

Description:

Operating History: The Auxiliary Building is a reinforced concrete structure that 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.

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 -29' elevation showed a mean gross activity level of 544,756 dpm/100. cm2 and a maximum value of 11,370,000 dpm/100 cm2. Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the Pump Alley of the auxiliary building was determined to be a Class 1 area.

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 144.1 m2 were scanned for 100% coverage. Soil samples were collected at each direct measurement location and analyzed by HPGe detector. 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 F8130421

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

'Survey Area:

F813 Survey Unit:

Class:

SU Area (m2):

Evaluator:

DCGL for Cs-137 surrogate (pCi/g):

DCGL for Co-60 (pCi/g):

Area Factor:

Design DCGLemc (pCi/g):

LBGR (pCi/g):

Design Sigma (pCi/g):

Type I Error:

Type II Error:

Sample Area (m2):

Total Area Scanned (m2):

Scan Coverage (%):

ZIa Sign P:

Calculated Relative Shift:

Relative Shift Used:

N-Value:

Design N-Value + 20%:

Grid Spacing L:

0421 1

144.1 D.A.Tallman 52.6 12.6 2.91/3.01 153/37.9 25.6 15.9 0.05 0.05 6.9 144.1 100%

1.645 1.645 0.945201 1.6 1.6 14 17 2.6 Pump Alley floor and soil walls Open Land Area LTP Table 5-4 Class 1 Class 1 Adjusted charterization samples of soil exposed during remediation resulting in the complete removal of concrete floor and sub floors Class 1 Class 1 Uses 3.0 if Rel Shift >3 NUREG-1575 Table 5-5 Class 1 Page 3 of 8 P FSS Summary Report F8130421

Survey Results:

A total of 21 direct measurements were made in F8130421. The results are shown in Table 2-1. Statistical data including the mean, median, and standard deviation are shown in Table 2-2. All of the direct measurements were less than Unity. Multiple scan measurements indicated areas of elevated activity. Scan activity ranged from 10992 to 46812 cpm and no background subtracted. Soil samples were counted to the MDC's shown in Table 2-1 of Attachment 2.

Page 4 of 8 FSS Summary Report F8130421

Table 2-1. Direct Measurement Results (all activity values in pCi/g)

Cs 137 Co6O Sample ID MDA Activity Uncertainty Unity MDA Activity Uncertainty Value Unity

• Value MD ciiy Ucrany Value Total F8130421S0001SS 7.16E-02 3.99E00 1.98E-01 0.0758 8.85E-02

<8.85E-02 0.007 0.0829 F8130421S0002SS 9.48E-02 5.93E00 2.48E-01 0.1127 6.70E-02 2.94E-01 5.30E-02 0.0234 0.1361 F8130421S0003SS 1.07E-01 9.53E00 3.16E-01 0.1813 1.OOE-01

<I.00E-01 0.0079 0.1892 F8130421S0004SS 8.85E-02 3.67E00 2.05E-01 0.0698 8.48E-02 3.1OE-01 5.93E-02 0.0246 0.0943 F8130421S0005SS 1.34E-01 2.47E01 5.25E-01 0.469 7.26E-02 2.44E-01 5.45E-02 0.0194 0.4884 F8130421S0006SS 8.25E-02 1.79E00 1.54E-01 0.0341 1.44E-01

<1.44E-01 0.0114 0.0455 F8130421S0007SS 1.29E-01 7.12E00 2.90E-01 0.1354 1.00E-01 1.45E00 1.14E-01 0.1151 0.2505 F8130421S0008SS 1.23E-01 1.68E01 4.22E-01 0.3199 7.43E-02 3.32E-01 5.73E-02 0.0264 0.3463 F8130421S0009SS 1.36E-01 2.77E01 5.42E-01 0.5261 7.21E-02 3.82E-01 5.92E-02 0.0303 0.5565 F8130421S0010SS 9.61E-02 1.19E01 3.56E-01 0.2253 7.13E-02 3.17E-01 5.69E-02 0.0252 0.2505 F8130421S0011SS 7.80E-02 3.99E00 2.02E-01 0.0759 1.08E-01

<1.08E-01 0.0086 0.0845 F8130421S0012SS 8.67E-02 2.32E00 1.65E-01 0.0442 1.05E-01

<1.05E-01 0.0083 0.0525 F8130421S0013SS 1.21E-01 1.64E01 4.02E-01 0.3121 5.93E-02 4.27E-01 6.03E-02 0.0339 0.346 F8130421S0014SS 6.95E-02 1.76E00 1.32E-01 0.0335 5.45E-02

<5.45E-02 2.77E-02 0.0043 0.0378 F8130421S0015SS 6.56E-02 4.09E-01 7.16E-02 0.0078 6.95E-02

<6.95E-02 0.0055 0.0133 F8130421S0016SS 5.61E-02 2.63E00 1.57E-01 0.05 8.OOE-02

<8.OOE-02 0.0063 0.0564 F8130421S0017SS 8.01E-02 2.67E00 1.61E-01 0.0508 8.45E-02

<8.45E-02 0.0067 0.0576 F8130421S0018SS 7.17E-02 3.03E00 1.69E-01 0.0576 4.61E-02 2.13E-01 4.51E-02 0.0169 0.0744 F8130421S0019SS 6.16E-02 1.O1EOO 1.OIE-01 0.0192 6.17E-02

<6.17E-02 0.0049 0.0241 F8130421S0020SS 1.01E-01 8.80E00 3.18E-01 0.1673 8.79E-02

<8.79E-02 0.007 0.1743 F8130421S0021SS 7.88E-02 3.67E00 1.90E-01 0.0698 6.78E-02

<6.78E-02 0.0054 0.0752 Page 5 of 8 FSS Summary Report F8130421

Table 2-2. Direct Measurements Results Summary Cs137 Co60 Activity Activity Cs137 Unity Co60 Unity Unity Total

. (pCi/g),

(pCi/g)

DCGLw 52.6 12.6 Mean 7.61E00 2.39E-01 0.1447 0.019 0.1636 Median 3.99E00 1.08E-01 0.0758 0.0086 0.0845 Standard Dvti 7.75E00 3.02E-01 0.1473 0.024 0.1555 DeviationII Cs137 Activity Range (pCi/g) 4.09E-01 to 2.77E01 Co60 Activity Range (pCi/g) 5.45E-02 to 1.45E00 Cs137 Unity Range 0.0078 to 0.5261 Co60 Unity Range 0.0043 to 0.1151 Total Unity Range 0.0133 to 0.5565 Sample Count-21 I

IPage 6 of 8 FSS Summary Report F8130421

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 3. 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.

Table 3. Data Assessment Results Survey Results Parameter Value Comment Actual Direct Measurements (N):

21 Median (Unity):

0.085 Mean (Unity):

0.164 Direct Measurement Std Deviation (Unity):

0.155 Maximum (Unity):

0.556 Sign Test Final N Value:

21 S+ Value:

21 Critical Value:

14 Sufficient Samples Collected:

Yes Maximum Value < Unitized DCGL:

Yes Median Value < Unitized DCGL:

Yes Mean Value < Unitized DCGL:

Yes Maximum Value < DCGLemc (Unity):

Yes Class I 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 F8130421

Survey Unit Investigations and Results:

Numerous investigations of multiple scan grids were required for the scan survey measurements and the results are reported in Attachment 3. Any areas found exceeding the DCGLw were remediated so that all as-left activity levels are below the DCGLw.

Since no as-left levels exceed the DCGLw the EMC unity calculation was not performed and the EMC Unity Sum is indicated as N/A 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 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 land 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. Potential areas of elevated activity were detected and evaluated as shown in Attachment 3. 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. All of the direct measurements were less than Unity. The investigations required were performed and documented.

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 F8130421 meets the release criteria of 10CFR20.1402.

Page 8 of 8 FSS Summary Report F8130421 Maps July 14, 2008 Survey Unit F8130421

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Table 2-1. Survey Unit Instrumentation Detector Detector Serial Instrument Model No.

MDC No.

Soil-1.36E-1 pCi/gCs-137 N/A__

05069128 1.44E-1 pCi/g Co-60 Instrument Detector MDC Model; Serial No.

Model; Serial No.

(dpmll00 cm2 )

M2350; 203481 44-10; 171992 167561 Background 8000 cpm or less Table 2-2. Investigation Criteria and DCGL Instrument Parameter Value M2350; 203481 44-10; 171992 20,000 cpm 52.6 pCi/g Cs-137 All DCGLw 12.6 pCi/g Co-60 153 pCi/g Cs-137 All DCGLEMc 37.9 pCi/g Co-60 Page 2 of 2 Att. 2 Instrumentation F8130421 Investigation July 14, 2008 Survey Unit F8130421

Table 3-1 Survey Unit Investigation Investigation Initial Initial Investigation Investigation DCGLemc Grid A Level B Value Value Result8 Elevated Area DCGLem, c Result Unity (cpm)

(P Ci/g)

(cpm)

(cpm)

Area (m 2)

Factor (pCi/g Cs-137)

Fraction 33GS 20,000 20,858 12,500 1.8 0

39GS 20,000 21,282 19,000 22.0 0

59/62 GS 20,000 25.2 21,631 8,500 15.1 0

64GS 20,000 65 20,738 7,800 3.8 0

66GS 20,000 20,119 8,500 15.1 0

70GS 20,000 20,468 8,500 15.1 0

74GS 20,000 18.9 22,659 8,500 15.1 0

76GS 20,000 15 25,919 8,500 15.1 0

97/98GS 20,000 29,680 16,000 2.3 0

122/125GS 20,000 37,454 17,300 1.6 0

129GS 20,000 9.2 31,500 c

0.7 0

132GS E 20,000 32,983 14,375 5.3 0

137GS E 20,000 83.4 25,906 7,100 1.2 0

140/153GS F 20,000 46,812 5,400.

9.0 0

154/161 GS 20,000 44 39,234 8,800 1.9 0

162GS 20,000 20,132 6,500 0.1 0

163GS D 20,000 17,959 7,300 10.3 0

Survey Unit Remainder DCGL 52.6 pCi/g Cs-137 SU Mean NA 12.6 pCi/g Co-60 Comments:

The Investigation Levels as designed were revised based on variability of local backgrounds observed. Based on LFSSE recommendations, regions greater than 30,000 cpm.were remediated and resurveyed while those between 20,000 and 30,000 would be sampled and resurveyed based on the results.

A Values noted for multiple grids series (59/62) indicate the highest observed within the stated series inclusive.

B Investigation initiated from gamma scan surveys performed with the 44-10. The release criteria are based on the soil sample results. The investigation cpm value is provided for comparison only.

c Post 44-10 reading not logged - technician recalled - 8,000 cpm 0 163GS included in the investigation due to proximity to grids 137 and 161 where elevated activity observed with relativity comparable 44-10 E readings.

Grids 133 and 135, reported at levels comparable to those reported in this investigation are contiguous with the reported grids 132 and 137.

Remedial activities within this region are bounded by the value reported for 132 and 137.

Investigation Grid 78, reported at levels comparable with those reported in this investigation is contiguous with the report grids 140 and 76.

Remedial activities associated with this region are bounded by the reported values for 140 and 76.

EMC Unity Sum NA Page 2 of 2 Att. 3 Investigation F8130421 Data Assessment July 14, 2008 Survey Unit F8130421

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