ML17065A047

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Final Status Survey Summary Report, October 3, 2016, Iosb Roof, Survey Unit F8300153
ML17065A047
Person / Time
Site: Rancho Seco
Issue date: 01/30/2017
From:
Sacramento Municipal Utility District (SMUD)
To:
Office of Nuclear Material Safety and Safeguards
Shared Package
ML17065A032 List:
References
DPG 17-038
Download: ML17065A047 (15)
v • d • e


Text

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Rancho Seco Final Status Survey Summary Report Octoher 3, 2016 IOSB ROOF Survey Unit F8300153 Prepared ey:_s_*

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FSS Engineer

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Approved By: ___ dJ:::-~--~~----- Date:

Manager, Rancho Seco Assets

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FINAL STATUS SURVEY F8300153 Survey Unit:

F8300153, Interim Onsite Storage Building (IOSB) Roof Survey Unit

Description:

Operating History: The current roof of the IOSB is not the original surface material. The roof surface material has been replaced since construction. The roof is occasionally exposed to high wind conditions and damage has occurred as a result. Additionally, a portion the roof is the closest horizontal surface to the IOSB ventilation stack. However, no records indicating measurable releases of radioactivity had been discovered. In March of 2016, the center section of the roof was replaced following a wind storm that removed most of the original material.

The removed material was surveyed as material and equipment in accordance with SMUD's procedures and released for disposal.

Site Characterization: Static measurements were made of the surface of the roof, to confom the absence or presence of plant-derived radionuclides. Static measurements showed a mean gross beta activity level of2,496/100 cm 2 and a maximum value of3,766 dpm/J 00 cm2* Based on the levels of gross activity reported, the area was determined to be a Class 3 area.

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. Static measurement locations were randomly determined and approximately 1 % of the area scanned. The instrumentation used for the survey along with the MDC values are listed in Table 2-1.

FSS IOSB Roof F8300153

FINAL STATUS SURVEY F8300153 Table 1, Survey Unit Design Parameters

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Survey Packaqe:

F830 IOSB Roof Survey Unit:

015 Class 3

SU Area (m2) 1735 Evaluator:

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'DCGLw:

43,000 Gross Activity DCGL Area Factor N/A Class 3 Design DCGLemc ( dpm/1 OOcm2 ):

N/A Class 3 DCGLemc:

N/A Class 3 LBGR:

21,500 Default= 50% DCGL Sigma:

707 Scoping Survey Data for Roof Type I error:

0.05 Type II error:

0.05 Predominant Nuclide Cs-137 Sample Area (m2)

N/A Total Instrument Efficiency:

0.129 Total Area Scanned (m2):

22.85 Scan Coveraqe (%)

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Material Type:

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1.645 Z1-a:

1.645 Siqn p:

  • 0.9986'5 Calculated Relative Shift:

30.4 Relative Shift Used:

3.0 Uses 3.0 if Relative Shift >3 N-Value:

11 N-Value+20%:

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FSS IOSB Roof F8300153

FINAL STATUS SURVEY F8300153 Survey Results:

A total of 15 direct measurements were made in F8300153. The results of the static measurements are shown in Table 2. All of the static measurements were less than the DCGL. The western roof is an asphalt surface verses the membrane surface for the center and eastern roofs. The asphalt portion results in higher activity (locations I - 3) than the membrane sections. None of the scan measurements indicated areas of elevated activity.

Table 2, Static Measurement Results

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1 F8300153Z00001 288 2,233 2 F8300153Z00002 302 2,341 3 F8300153Z00003 297 2,302 4 F8300153Z00004 171 1,326 5 F8300153Z00005 171 1,326 6 F8300153Z00006 253 1,961 7 F8300153Z00007 176 1,364 8 F8300153Z00008 171 1,326 9 F8300153Z00009 171 1,326 10 F8300153Z00010 184 1,426 11 F8300153Z00011 169 1,310 12 F8300153Z00012 143 1, 109 13 F8300153Z00013 184 1,426 14 F8300153Z00014 162 1,256 15 F8300153Z00015 161 1,248 Table 3 contains the statistical summary of the static measurement data for the IOSB Roof.

3 Table 3, Beta Summary Statistics Mean Median Beta Static /OSB Roof Standard Deviation Minimum Maximum Count FSS IOSB Roof 1,552 1,326 425 1,109 2,341 15 F8300153

FINAL STATUS SURVEY F8300153 Survey Unit Data Assessment:

The survey design required 14 static measurements for the Sign Test. A total of 15 static measurements were collected. 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.

Table 4, Data Assessment Results Number of Samoles:

15 Median:

1,3~6

  • Mean:

1,552 Static Data Standard Deviation:

425 Maximum:

2,34 f Adiusted N Value:

14 S+ Value:

15 Critical Value:

. 10 Sufficient samples collected:

Pass Maximum value <DCGLw:

Pass Median value <DCGLw:

Pass Mean value <DCGLw:

Pass Maximum value <DCGLemc:

N/A Siqn test results:

Pass.

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The survev unit oasses all conditions:

Pass 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, the ALARA criterion has been met.

Changes in Initial Survey Unit Assumptions:

The survey unit was designed as a Class 3 survey and the sample results are consistent with that classification. The variability of the survey results was higher than the characterization data used for survey design. However the relative shift exceeded 3 and had to be adjusted. No potential areas of elevated activity were detected.

4 FSS IOSB Roof F8300153

FINAL STATUS SURVEY,F8300153

==

Conclusion:==

The FSS of this survey unit was properly designed as a Class 3 survey based on the results of the scoping survey. 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 static measurements were less than the DCGL. No investigations were required.

The static 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 F8300153 meets the release criteria of I OCFR20. l 402.

5 FSS IOSB Roof F8300153 Maps October 3, 2016 Survey Unit F8300153

{!) F8300153Z00003 13 = 2 302 dpm1100 cm 2

{+/-) F8300153Z00001 13 = 2 233 dprn1100 cm2 F8300153Z00002 (3 = 2.341 dpm/100 cm2 <+/-)

IOSBROOF SMUD Location*

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Page I F8300153Z00010 (3 = 1. 426 dpm/100 cm2

(+/-) F8300153Z00007 (3 = 1 364 dpm/ 100 cm*

{j) F8300153Z00013 13== 1.426 dpm 100 cmi F8300153Z00004 13 = 1 326 dpm1100 cm* @

(+/-} F8300153Z00009 (3 = 1,326 dpm1100 cm 2 F83001 53ZOOOC6 {!)

13 = 1 961 dpm 1100 cm2 F8300153Z00012 @

(3 = 1 109 dpm/100 cm2 F8300 53200008 13 = 1,326 dpm/1 00 cm* <+/-)

(+/-} F8300153Z00014

(+/-} F8300153Z00005 13 = 1,326 dpm/100 cm*

(3 = 1 256 dpm'100 cm*

<+/-) F8300153Z00011 (3 = 1.31 0 dpm/1 00 cm*

Att. I Maps

{j) F8300153Z00015 (3 = 1,248 dpm11 00 c n 2 F8300153

'Instrumentation October 3, 2016 Survey Unit F8300153

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Beta Static Measurement Table 2-1. Survey Unit Instrumentation Ludlum Model 2350-1 Ludlum Model 44-116 B Detector Beta -

512 dpm/100 cm2

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  • 317899/331973 2/10/17
  • Minimum detectable activities for the count rate instrumentation were calculated in accordance with NUREG-1507, "Minimum Detectable Concentrations with Typical Radiation Survey Instruments for Various Contaminants and Field Conditions" (U.S. NRC, 1997).

b Detectors are required to be calibrated once every 12 months. Calibration due date indicates the date by which the detector must be calibrated again.

cm2 = square centimeters cpm =counts per minute dpm =disintegrations per minute Page 1 Att. 2 Instrumentation F8300153

Static Measurement MDA Variables Beta Survey Type PR331973 Detector Number 184 Background count rate (cpm) 1 Count Time (min) 0.129 Efficiency 100 Area of Detector (cm2)

Constants 60 sec/min 2.54 cm/in Assumptions Background count time and sample count time are equivalent Calculate Static MDA Static MDA =3 + 4.65(Br

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Where:

Static MDA Page 2 Br t

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Background Countrate Count Time (min)

Efficiency Area of detector (cm2) 512 dpm/100 cm2 Att. 2 Instrumentation F8300153

Att. 3 Jnvestigation Investigation October 3, 2016 Survey Unit F8300153 (none required)

F8300153 Data Assessment October 3, 2016 Survey Unit F8300153

Histogram for Beta Static Activity IOSB Roof 10

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Att. 4 Data Assessment

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