ML13130A136

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Instrument Efficiency Determination for Use in Minimum Detectable Concentration Calculations in Support of the Final Status Survey at Hbpp
ML13130A136
Person / Time
Site: Humboldt Bay
Issue date: 06/13/2012
From: Erickson M
Pacific Gas & Electric Co
To:
NRC/FSME
References
HBL-13-008
Download: ML13130A136 (36)
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Text

Enclosure 2 PG&E Letter HBL-13-008 Instrument Efficiency Determination for Use in Minimum Detectable Concentration Calculations in Support of the Final Status Survey at HBPP June 13, 2012

PacificGas and Electric Company' Instrument Efficiency Determination for Use in Minimum Detectable Concentration Calculations in Support of the Final Status Survey at HBPP June, 13, 2012 Martin C. Erickson Reviewed By: - 8,1-j Date:

Approved By: Approved By: - 7/i /Z, z Date: 7z, Z--

Table of Contents 1.0 INT R O D UC T IO N........................................................................................ 1 2.0 CALIBRATION SOURCES ......................................................................... 1 3.0 EFFICIENCY DETERMINATION .......................................................... 5 3.1 Alpha and Beta Instrument Efficiency (el) ........................................... 5 3.2 Source to Detector Distance Considerations ..................................... 6 3.2.1 Methodology ............................................................................... 7 3.3 Source (or surface) Efficiency (es) Determination .............................. 7 4.0 INSTRUMENT CONVERSION FACTOR (Ei) (INSTRUMENT EFFICIENCY FOR SCANNING) ...................................................................... 8 5.0 APPLYING EFFICIENCY CORRECTIONS BASED ON THE EFFECTS OF FIELD CONDITIONS FOR TOTAL EFFICIENCY ....................................... 9 6.0 C O NC LU S IO N ..................................................................................... 10 7.0 R E FE R E NC ES ..................................................................................... 10 Tables Table 2. 1 Nuclides and Major Radiations: Approximate Energies ................... 3 Table 3. 1 Instrument Efficiencies (el) ............................................................... 6 Table 3. 2 Source to Detector Distance Effects on Instrument Efficiencies for a -

P3 E m itters ................................................................................................. .. ... 7 Table 3. 3 Source Efficiencies as Listed in ISO 7503-1 ................................... 8 Table 4. 1 Energy Response and Efficiency for Photon Emitting Isotopes ..... 9 ii

Executive Summary The minimum detectable concentration (MDC) of the field survey instrumentation is an important factor affecting the quality of the final status survey (FSS). The efficiency of an instrument inversely impacts the MDC value. The objective of this report is to determine the instrument and source efficiency values used to calculate MDC. Several factors were considered when determining these efficiencies and are discussed in the body of this report. Instrument efficiencies (e1), and source efficiencies (es), for alpha beta detection equipment under various field conditions, and instrument conversion factors (E1), for gamma scanning detectors were determined and the results are provided herein.

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1.0 INTRODUCTION

Before performing Final Status Surveys of building surfaces and land areas, the MDC must be calculated to establish the instrument sensitivity. The Humboldt Bay Power Plant (HBPP) License Termination Plan (LTP) lists the available instrumentation and nominal detection sensitivities; however for the purposes of this basis document, efficiencies for the nominal 100cm 2 gas proportional and the 2"x2" Nal (TI) detectors will be det ermined. Efficiencies for the other instrumentation listed in the LTP shall be determined on an as needed basis. The 100 cm 2 gas proportional probe will be used to perform building surface surveys (i.e. fixed point measurements). A 2"x2" Nal (TI) detector will be used to perform gamma surveys (i.e., surface scans) of portions of land areas and possibly supplemental structural scans at the HBPP site. Although surface scans and fixed point measurements can be performed using the same instrumentation, the calculated MDCs will be quite different. MDC is dependent on many factors and may include but is not limited to:

  • Instrument Efficiency
  • Background
  • Integration Time
  • Surface Type
  • Source to Detector Geometry
  • Source Efficiency A significant factor in determining an instrument MDC is the total efficiency, which is dependent on the instrument efficiency, the source efficiency and the type and energy of the radiation. MDC values are inversely affected by efficiency, as efficiencies increase, MDC values will decrease. Accounting for both the instrument and source components of the total efficiency provides for a more accurate assessment of surface activity.

2.0 CALIBRATION SOURCES For accurate measurement of surface activity it is desirable that the field instrumentation be calibrated with source standards similar to the type and energy of the anticipated contamination. The nuclides listed in Table 2.1 illustrate the nuclides found in soil and building surface area DCGL results that are listed in the LTP.

Instrument response varies with incident radiations and energies; therefore, instrumentation selection for field surveys must be modeled on the expected surface activity. For the purposes of this report, isotopes with max beta energies less than that of C-14 (0.158 MeV) will be considered difficult to detect (reference I

table 2.1). The detectability of radionuclides with max beta energies less than 0.158 MeV, utilizing gas proportional detectors, will be negligible at typical source to detector distances of approximately 0.5 inches. The source to detector distance of 1.27 cm (0.5 inches) is the distance to the detector' with the recommended standoff. Table 2.1 provides a summary of the LTP radionuclides and their detectability using Radiological Health Handbook data.

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Table 2. 1 Nuclides and Major Radiations: Approximate Energies Nuclide a Energy E13max Average Ep Photon Energy a Detectable 1 Detectable y (MeV) (MeV) (MeV) (MeV) w/Gas wlGas Detectable Proportional Proportional w/Nal 2x2 H-3 0.018 0.005 C-14 0.158 0.049 Ni-59 Co-60 0.314 0.094 1.173(100%)

1.332(100%) "

Ni-63 0.066 0.017 Sr-90 0.544 0.200 0.931 2.245(Y-90) /

Nb-94 0.50 0.156 0.702(100%)

0.871(100%) -

Tc-99 0.295 0.085 /

1-129 0.154 0.041 0.039(8%) /

Cs-1 37 1.167(5.4%) 0.195 0.662(85%)

0.512(95%) Ba-1 37m X-Rays /

Eu-1 52 1.840 0.288 0.122(37%) 0.245 (8%)

0.344(27%) 0.779(14%)

0.965(15%), 1.087(12%) /

1.113((14%) 1.408(22%)

Eu-1 54 1.850(10%) 0.228 0.143(40%)

1.274(35%) /

Np-237 4.79(47%)

4.77(25%)

4.64(6%)

Pu-238 5.50(72%) 0.099(8E-3%)

5.46(28%) 0.150(1 E-3%)

0.77(5E-5%) "

Pu-239 5.16(88%) 0.039(0.007%)

5.11(11%) 0.052(0.20%)

0.129(0.005%) /

Pu-240 5.17(73%)

5.12(27%) /

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Nuclide a Energy Eimax Average Ep Photon Energy a Detectable 13 Detectable y (MeV) (MeV) (MeV) (MeV) w/Gas w/Gas Detectable Proportional Proportional w/Nal 2x2 Pu-241 4.90(0.0019%)

4.85(0.0003%) 0.021 0.005 0.145(1.6E-4%)

Am-241 5.49(85%) 0.060(36%)

5.44(13%) 0.101(0.04%) "/

Cm-243 6.06(6%)

5.99(6%) 0.209(4%)

5.79(73%) 0.228(12%)

5.74(11.5%) 0.278(14%) /

Cm-244 5.8(76%)

5.76(24%) /

Cm-245 5.36(93%) 0.175(10%)

5.3(5%) /

Cm-246 5.39(82%)

5.34(18%) /

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NUREG-1507 and ISO 7503-1 provide guidance for selecting calibration sources and their use in determining total efficiency. It is common practice to calibrate instrument efficiency for a s ingle beta energy; however the energy of this reference source should not be significantly greater than the beta energy of the lowest energy to be measured. Calibration sources should be selected that emit alpha or beta radiation with energies similar to those expected of the contaminant in the field. Cs-137 and Sr-90 are the major beta contributors at HBPP with Cs-137 having the lowest energy.

Cs-137 (0.512MeV at 95% and 1.17Mev at 5.4%) and Am-241 (4.68 MeV at 76%

and 5.49 MeV at 85%) have been selected as the beta and alpha calibration standards respectively, because their energies conservatively approximate the beta and alpha energies of the plant specific radionuclides most prevalent in the field.

3.0 EFFICIENCY DETERMINATION Typically, using the instrument 4Tr efficiency exclusively provides a g ood approximation of surface activity. Using these means for calculating the efficiency often results in an under estimate of activity levels in the field. Applying both the instrument 2Tr efficiency and the surface efficiency components to determine the total efficiency allows for a more accurate measurement due to consideration of the actual characteristics of the source surfaces. ISO 7503-1 recommends that the total surface activity be calculated using:

= RS+B -RB where:

As is the total surface activity in dprn/cm 2 ,

Rs +B is the gross count rate of the measurement in cpm, RB is the background count rate in cpm, ei is the instrument or detector 2Tr efficiency es is the efficiency of the source W is the area of the detector window (cm 2 ) (126 cm2 for the 43-68) 3.1 Alpha and Beta Instrument Efficiency (e,)

Instrument efficiency (ei) reflects instrument characteristics and counting geometry, such as source construction, activity distribution, source area, particles 5

incident on the detector per unit time and therefore source to detector geometry.

Theoretically the maximum value of es is 1.0, assuming all the emissions from the source are 2-rr and that all emissions from the source are detected. The ISO 7503-1 methodology for determining the instrument efficiency is similar to the historical 4T-r approach; however the detector response, in cpm, is divided by the 2Tr surface emission rate of the calibration source. The instrument efficiency is calculated by dividing the net count rate by the 2Trr surface emission rate (q2, ) (Includes absorption in detector window, source detector geometry). The instrument efficiency is expressed in ISO 7503- 1 by:

-R Ri e= S+B RB where:

RS+B is the gross count rate of the measurement in cpm, RB is the background count rate in cpm, q 2, is the 2Tr surface emission rate in reciprocal seconds Note that both the 2r" surface emission rate and the source activity are usually stated on the certification sheet provided by the calibration source manufacturer and certified as National Institute of Standards and Technology (NIST) traceable. Table 3.1 depicts nominal instrument efficiencies that have been determined during calibration using the 2rr surface emission rate of the source.

Table 3. 1 Instrument Efficiencies (es) 100 cm 2 Gas Proportional 43-68 Active Area Area of the Instrument Source Emission of the Source Detector Efficiency (ei) 2 (cm ) (Contact)

Cs-1 37 15.2 100 cm 2 0.4800 Am-241 a 15.2 100 cm 2 0.2500 3.2 Source to Detector Distance Considerations A major factor affecting instrument efficiency is source to detector distance.

Consideration must be given to this distance when selecting accurate instrument efficiency. The distance from the source to the detector shall to be as close as practicable to geometric conditions that exist in the field. A range of source to detector distances has been c hosen, taking into account site specific survey 6

conditions. In an effort to minimize the error associated with geometry, instrument efficiencies have been determined for source to detector distances representative of those survey distances expected in the field. The results shown I in Table 3.2 illustrate the imposing reduction in detector response with increased distance from the source. Typically this source to detector distance will be 0.5 inches for fixed point measurements and 0.5 inches for scan surveys on flat surfaces, however they may differ for other surfaces. Table 3.2 makes provisions for the selection of source to detector distances for field survey conditions of up to 2 i nches. If surface conditions dictate the placement of the detector at distances greater than 2 inches instrument efficiencies will be determined on an as needed basis.

3.2.1 Methodology The practical application of choosing the proper instrument efficiency may be determined by averaging the surface variation (peaks and valleys narrower than the length of the detector) and adding 0.5 inches, the spacing that should be maintained between the detector and the highest peaks of the surface. The source-to-detector distance was evaluated using a Ludlum 43-68 gas proportional detector with a 0.8 mg/cm 2 window for Cs-137 and Am-241. Five 1 minute measurements were made on contact and at distances of 0.5, 1 and 2 centimeters. Measurement results are contained in Attachment 1.

Select the source to detector distance from Table 3.2 that best reflects this pre-determined geometry.

Table 3. 2 Source to Detector Distance Effects on Instrument Efficiencies for a - 13 Emitters Source to Detector Instrument Efficiency (e1)

Distance (cm) Cs-137 Distributed Am-241 Disc Contact 1 1 0.5 0.8935+/-0.019 0.8331+/-0.007 1.0 0.8159+/-0.021 0.7244+/-0.007 2.0 0.6592+/-0.023 0.3615+/-0.010

  • Uncertainties represent the 95% confidence interval. Based on propagating the counting errors in each measurement 3.3 Source (orsurface) Efficiency (es) Determination Source efficiency (es), reflects the physical characteristics of the surface and any surface coatings. The source efficiency is the ratio between the number of particles emerging from surface and the total number of particles released within the source. The source efficiency accounts for attenuation and backscatter. es is nominally 0.5 (no self-absorption/attenuation, no b ackscatter)-backscatter 7

increases the value, self-absorption decreases the value. Source efficiencies may either be derived experimentally or simply selected from the guidance contained in ISO 7503-1. ISO 7503-1 takes a c onservative approach by recommending the use of factors to correct for alpha and beta self-absorption/attenuation when determining surface activity. However, this approach may prove to be too conservative for radionuclides with max beta energies that are marginally lower than 0.400 MeV, such as Co-60 with a I3max of 0.314 MeV. In this situation, it may be more appropriate to determine the source efficiency by considering the energies of other beta emitting radionuclides. Using this approach it is possible to determine weighted average source efficiency. For example, a source efficiency of 0.375 may be calculated based on a 50/50 mix of Co-60 and Cs-137. The source efficiencies for Co-60 and Cs-137 are 0.25 and 0.5 respectively, since the radionuclide fraction for Co-60 and Cs-137 is 50% for each, the weighted average source efficiency for the mix may be calculated in the following manner:

(0.25)(0.5)+ (0.5Xo.5) = 0.375 Table 3.3 lists guidance on source efficiencies from ISO 7503-1.

Table 3. 3 Source Efficiencies as Listed in ISO 7503-1

> 0.400 MeVmax -50.400 MeVmax Beta Emitters e. = 0.5 es = 0.25 Alpha Emitters es = 0.25 es = 0.25 It should be noted that source efficiency is not typically addressed for gamma detectors as the value is effectively unity.

4.0 INSTRUMENT CONVERSION FACTOR (Ei)

(INSTRUMENT EFFICIENCY FOR SCANNING)

Separate modeling analysis (Microshield TM ) was conducted using the common gamma emitters with a c oncentration of 1 pC i/g of uniformly distributed contamination throughout the volume. Microshield is a c omprehensive photon/gamma ray shielding and dose assessment program, which is widely used throughout the radiological safety community. An activity concentration of 1 pCi/g for the nuclides was entered as the source term. The radial dimension of the cylindrical source was 28 cm, the depth was 15 cm, and the dose point above the surface was 10 cm with a soil density of 1.6 g/cm 3 . The instrument efficiency when scanning, Ei, is the product of the modeled exposure rate ( MicroshieldTM) mRhr-1/pCi/g and the energy response factor in cpm/mR/hr as derived from the energy response curve provided by Ludlum Instruments (Appendix A). Table 4.1 demonstrates the derived efficiencies for the major gamma emitting isotopes listed in Table 2.1.

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Table 4. 1 Energy Response and Efficiency for Photon Emitting Isotopes Ei Isotope (cpm/pCilg)

Co-60 315 Nb-94 387 Cs-137 202 Eu-152 419 Eu-1 54 230 When performing gamma scan measurements on soil surfaces the effective source to detector geometry is as close as is reasonably possible (less than 3 inches).

5.0 APPLYING EFFICIENCY CORRECTIONS BASED ON THE EFFECTS OF FIELD CONDITIONS FOR TOTAL EFFICIENCY The total efficiency for any given condition can now be calculated from the product of the instrument efficiency ei and the source efficiency es.

Etotal = ei x es The following example illustrates the process of determining total efficiency. For this example we will assume the following:

" Surface activity readings need to be made in the HBPP Security Building concrete wall surfaces using the 2350-1 and 43-68 gas proportional detector.

" Data obtained from characterization results from the security building indicate the presence of beta emitters with energies greater than 0.400 MeV.

" The source (activity on the wall) to detector distance is 0.5 inch detector stand off. To calculate the total efficiency, etotal, refer to Table 3.2 "Source to Detector Distance Effects on Instrument Efficiencies for a - 03 Emitters" to obtain the appropriate ej value.

0 Contamination on all surfaces is distributed relative to the effective detector area.

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" When performing fixed-point measurements with gas proportional instrumentation the effective source-to-detector geometry is representative of the calibrated geometries listed in Table 3.1.

" Correction for pressure and temperature are not substantial. ,

In this example, the 2Tr value for ej is 0.48 as depicted in Table 3.1 "Instrument Efficiencies"'. The source-to-detector correction for 0.5 inches is 0.8935 as depicted in Table 3.2 "Source to Detector Distance Effects on Instrument Efficiencies for a- 8 Emitters". The es value of 0.5 is chosen refer to Table 3.3 "Source Efficiencies as listed in ISO 7503-1". Therefore the total efficiency for this condition becomes = e1 x e. = 0.48 x 0.8935 x 0.5 = 0.214 or 21.4%.

6.0 CONCLUSION

Field conditions may significantly influence the usefulness of a survey instrument.

When applying the instrument and source efficiencies in MDC calculations, field conditions must be considered. Tables have been constructed to assist in the selection of appropriate instrument and source efficiencies. Table 3.2 "Source to Detector Distance Effects on Instrument Efficiencies for a-p Emitters" lists instrument efficiencies (ei) at various source to detector distances for alpha and beta emitters. The appropriate ei value should be applied, accounting for the field condition, i.e. the relation between the detector and the surface to be measured.

Source efficiencies shall be selected from Table 3.3 "Source Efficiencies as listed in ISO 7503- 1 ". This table lists conservative es values that correct for self-absorption and attenuation of surface activity. Table 5.1 "Energy Response and Efficiency for Photon Emitting Isotopes" lists E1 values that apply to scanning MDC calculations. The MicroshieldTM model code was used to determine instrument efficiency assuming contamination conditions and detector geometry cited in section 5.4.4.4.5 "MDCs for Gamma Scans of Land Areas" of the License Termination Plan.

Detector and source conditions equivalent to those modeled herein may directly apply to the results of this report.

7.0 REFERENCES

7.1 NUREG- 1507, "Minimum Detectable Concentrations with Typical Radiation Survey Instruments for Various contaminants and Field Conditions," 1998 7.2 ISO 7503- 1, "Evaluation of Surface Contamination - Part I: Beta Emitters and Alpha Emitters," 1988-08-01.

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7.3 ISO 8769, "Reference Sources for the Calibration of Surface Contamination Monitors-Beta-emitters (maximum beta energy greater

0. 15MeV) and Alpha-emitters," 1988 15.

7.4 "Radiological Health Handbook," Revised Edition 1970.

I1

Appendix A MicroshieldTm and Excel Forms 12

MicroShield 8.03 Pacific Gas and Electric Co. (8.03-0000)

Date By Checked Filename Run Date Run Time Duration HBPP Co60 eff.msd February 9, 2012 10:58:03 AM 00:00:00 Project Info Case Title 44-10 eff Co-60 Description HBPP 44-10 eff for Co-60 Geometry 8 - Cylinder Volume - End Shields Source Dimensions Height 15.0 cm (5.9 in)

Radius 28.0 cm (11.0 in)

Dose Points A X Y Z

  1. 1 0.0 cm (0 in) 25.0 cm (9.8 in) 0.0 cm (0 in)

Shields Shield N Dimension Mat4 ial Density Source 3.69e+04 cm 3 Mixe*d-> 1.60122 Air 0.00122 SOIL 1.6 Air Gap Air 0.00122 Source Input: Grouping Method - Actual Photon Energies Nuclide Ci Bq pCi/cm 3 Bq/cm3 Co-60 3.6945e-008 1.3670e+003 1.00OOe-006 3.7000e-002 Buildup: The material reference is Source Integration Parameters Radial 20 Circumferential 10 Y Direction (axial) 10 Results 13

Exposure Fluence Fluence Rate Exposure Rate Energy Activity Rate MeV/cm2 /sec Rate (Photons/sec) mR/hr (MeV) MeV/cm2/sec With mR/hr With No Buildup Buildup No Buildup Buildup=

9.138e-06 F'

1 0.6938 1.1732 1.3325 2.230e-01 1.367e+03 1.367e+03 1.107e-01j 1.303e-01 1.88le-05 1.777e-01 2.020e-01 1.764e-08 1.978e-04 2.261e-04 3.633e-08 3.175e-04 3.504e-04 Totals 2.734e+03 2.410e-01 3.796e-01 4.239e-04 6.679e-04 Co-60 Microsoft Excel E, Calculation Sheet 14

Exposure Energy Energy Rate Energy Ej (MeV) (keV) (mR/hr-1 Response (cpm/pCi/g) pCi/g) cpm/mR/hr) 0.6938 694 6.63E-08 810,000 0 1.1732 1173 3.18E-04 495,000 157 1.3325 1333 3.50E-04 450,000 158 4 4

+ f 4 1* t 4 I +

I. t I.

I* t Ej Total 315 MicroShield 8.03 Pacific Gas and Electric Co. (8.03-0000) 15

Date By Checked Filename Run Date Run Time Duration HBPP Nb94 eff.msd February 9, 2012 11:54:43 AM 00:00:00 Project Info Case Title 44-10 eff Nb-94 Description HBPP 44-10 eff for Nb-94 Geometry 8 - Cylinder Volume - End Shields Source Dimensions Height 15.0 cm (5.9 in)

Radius 28.0 cm (11.0 in)

Dose Points A X Y z 41 0.0 cm (0 in) 25.0 cm (9.8 in) 0.0 cm (0 in)

Shields Shield N Dimension Material Density Source 3.69e+04 cm 3 Mixed-> 1.60122 Air 0.00122 SOIL 1.6 Air Gap Air 0.00122 Source Input: Grouping Method - Actual Photon Energies 3

Nuclide Ci Bq piCi/cm Bq/cm3 Nb-94 3.6945e-008 1.3670e+003 1.00OOe-006 3. 7000e-002 Buildup: The material reference is Source Integration Parameters Radial 20 Circumferential 10 Y Direction (axial) 10 Resultts Energy Activity Fluence Fluence Rate Exposure Exposure (MeV) (Photons/see) Rate MeV/cm 2 /sec Rate Rate 16

MeV/cm 2 /sec With mRlhr mRlhr No Buildup Buildup No Buildup With

_Buildup-0.0023 9.067e-02 8.023e-11 2.388e-10 1.073e-10 3.195e-10 0.0174 4.834e-01 5.28e-09 1.83 1e-08 2.855e-10 9.884e-10 0.0175 9.260e-01 1.038e-08 3.627e-08 5.499e-10 1.921e-09 0.0196 2.720e-01 I 4.802e-09 2.057e-08 1.773e-10 7.595e-10 0.7026 1.367e+03 5.695e-02 1.166e-01 1.098e-04 2.248e-04 0.8711 1.367e+03 7.530e-02 1.381e-01 1.417e-04 2.600e-04 Totals 2.736e+03 1.322e-01 2.547e-01 2.515e-04 4.848e-04 Nb-94 Microsoft Excel Ej Calculation Sheet 17

Energy Energy Exposure Energy Ej (MeV) (keV) Rate Response (cpm/pCi/g)

(mR/hr-1 pCi/g) cpm/mR/hr) 0.0023 2 3.20E-10 0 0.0174 17 9.88E-10 0 0.0175 18 1.92E-09 0 0.0196 20 7.60E-10 0 0.7026 703 2.25E-04 846,000 190 0.8711 871 2.60E-04 756,000 197 4 t *1 I. 4 4 I. + I. I I 4 4 *1 I. 4 4

i. +

4 4 + *1-4 + 4 +

i I i Ej Total 1 387 MicroShield 8.03 Pacific Gas and Electric Co. (8.03-0000)  !

18

Date By Checked Filename Run Date Run Time Duration HBPP Csl37eff.msd February 9, 2012 12:17:17 PM 00:00:00 Project Info Case Title 44-10 effCs-137 Description HBPP 44-10 eff for Cs-137 Geometry 8 - Cylinder Volume - End Shields Source Dimensions Height 15.0 cm (5.9 in)

Radius 28.0 cm (11.0 in)

Dose Points A X Y Z

  1. 1 0.0 cm (0 in) 25.0 cm (9.8 in) 0.0 cm(0 in)

Shields Shield N Dimension Material Density Source 3.69e+04 cm 3 Mixed -> 1.60122 Air 0.00122 SOIL 1.6 Air Gap Air 0.00122 Source Input: Grouping Method - Actual Photon Energies Nuclide Ci Bq pCi/cm3 Bq/cm 3 Ba-137m 3.4950e-008 1.2932e+003 9.4600e-007 3.5002e-002 Cs-137 3.6945e-008 1.3670e+003 1.00OOe-006 3.7000e-002 Buildup: The material reference is Source Integration Parameters Radial 20 Circumferential 10 Y Direction (axial) 10 Results 19

Exposure Fluence Fluence Rate Exposure Rate Energy Activity Rate MeV/cm2 /sec Rate 2 mR/hr (MeV) (Photons/sec) [leV/cm /sec With mR/hr With No Buildup Buildup No Buildup Buildup 0.0045 _ 1.342e+01 2.319e-08 6.901e-08 1.589e-08 4.730e-08 0.0318 2.677e+01 3.00le-06 3.558e-05 2.499e-08 112.964e-07 0.0322 4.939e+01 5.782e-06 7.018e-05_ 4.653e-08 11 5.648e-07 0.0364 1.797e+01 A 3.281e-06 j5.035e-05 L1.864e-08 ] 2.860e-07 0.6616 1. 164e+03 4.482e-02 9.434e-02 8.690e-05 1.829e-04 Totals .. 1.271e+03 4.484e-02 _9.450e-02 8.701e-05 1.841e-04 Cs-1 37 Microsoft Excel Ei Calculation Sheet Energy Energy Exposure Energy Ej (MeV) (keV) Rate Response (cpm/pCi/g)

(mR/hr-1 pCi/g) cpm/mR/hr) 0.0045 5 3.20E-10 0 0.0318 32 9.88E-10 0 0.0322 32 1.92E-09 0 0.0364 36 7.60E-10 0 0.6616 662 2.25E-04 900,000 202 20

_______________________ Ej Total 202 MicroShield 8.03 Pacific Gas and Electric Co. (8.03-0000)

JL 202 E* Total Date By i _

Checked Filename Run Date Run Time Duration HBPP Eu152 eff.msd PFebruary oM9, 2012 12:21:22 00. 00:00 ProHect 9nfo Case Title 44-10 effEu-152 Description L.HBPP 44-10 eff for Eu-152 21

Geometry 8 - Cylinder Volume - End Shields Source Dimensions Height 15.0 cm (5.9 in)

Radius 28.0 cm (11.0 in)

Dose Points A X Y z

  1. 1 0.0 cm (0 in) 25.0 cm (9.8 in) 0.0 cm (0 in)

Shields Shield N Dimension Material Source 3.69e+04 cm 3 Mixed ->

Air SOIL Air Gap Air Source Input: Grouping Method - Standard Indices Number of Groups: 25 Lower Energy Cutoff: 0.015 Photons < 0.015: Included Library: Grove Nuclide Ci Bq ACi/cm 3 Bq/cm 3 Eu-152 3.6945e-008 1.3670e+003 1.00OOe-006 3.7000e-002 Buildup: The material reference is Source Integration Parameters Radial 20 Circumferential 10 Y Direction (axial) 10 Results Exposure Fluence Fluence Rate Exposure Rate Energy Activity Rate MeV/cm 2 /sec Rate (MeV) (Photons/sec) MeV/cm 2/sec mR/hr With mR/hr With No Buildup Buildup No Buildup Buildup 0.015 2.077e+02 1.204e-06 3.583e-06 1.033e-07 3.073e-07 0.04 8.088e+02 2.054e-04 3.698e-03 9.082e-07 1.635e-05 22

FI

!Ii 0.05 2.022e+02 1.067e-04 2.522e-( 3 ]2.841 e-071 719e-06 0.1 3.887e+02 1.090e-03 1.656e-( )2 l.667e-06~ 2.534e-051 0.2 1.024e+02 8.179e-04 4.688e-( )3 1.443e-06 8.274e-06

  • 0.3 3.696e+02 5.060e-03 1.857e-( )2 9.598e 3.522e-05 0.4 8.590e+01 1.715e-03 5.247e-( B 3.342e-06 1.022e-05 0.5 7.711 e+00 2.061 e-04 5.042e-( A 4.046e-07 -9.97e-07 0.6 5.797e+01 1.966e-03 4.324e-( 3- 3. -837e-06 -8 .44 1e_0 6 0.8 2.434e+02 1.200e-02 2.305e-( )2 2.283e-05 4.384e 1.0 5.849e+02 3.853e-02 6.582e-( )2 7.102e-05 1.213e-04 I 1.5 3.171 e+02 3.515e-02 5.314e-( )2 5.914e-05 8.940e-05 Totals 3.376e+03 9.685e-02 1.981e-( )i 1.746e-04 3.664e-04}

Eu-1 52 Microsoft Excel E Calculation Sheet Energy Energy Exposure Energy Ei (MeV) (keV) Rate Response (cpm/pCi/g)

(mR/hr-1 pCi/g) cpm/mR/hr) 0.015 15 3.07E-07 0 0.04 40 1.64E-05 0 0.05 50 6.72E-06 0 0.1 100 2.53E-05 4,680,000 119 0.2 200 8.27E-06 3,420,000 28 0.3 300 3.52E-05 2,610,000 92 0.4 400 1.02E-05 2,070,000 21 0.5 500 9.90E-07 1,575,000 2 0.6 600 8.44E-06 1,080,000 9 0.8 800 4.38E-05 765,000 34 1 1000 1.21E-04 630,000 76 1.5 1500 8.94E-05 425,000 38 t I 23

24 Case Summary of 44-10 effEu-154 Page I of 2 MicroShleld 8.03 Pacific Gas and Electric Co. (8.03-0000)

Date By Checked Filename Run Date Run Time Duration HBPPEu154eff.msd June 12, 2012 1:24:05 PM 00:00:00 Project Info Case Title 44-10 effEu-154 Description HBPP 44-10 eff for Eu-154 Geometry 8 - Cylinder Volume - End Shields Source Dimensions Height 15.0 cm (5.9 in)

Radius 28.0 cm (11.0 in)

Dose Points A X Y Z

  1. 1 0.0cm (0 in) 25.0 cm (9.8 in) 0.0 cm (0 in)

Shields Shield N Dimension Material Density Source 3.69c+04 cm' Mixed-> 1.60122 Air 0.00122 SOIL 1.6 Air Gap Air 0.00122 Source Input: Grouping Method - Standard Indices Number of Groups: 25 Lower Energy Cutoff: 0.015 Photons < 0.015: Included Library: ICRP-38 Nueide Ca Bq pCicm' Bq/cm' Eu- 154 3.6945e-008 1.3670c+003 1.OOO0e-006 3.7000e-002 Buildup: The material reference Is Source Integration Parameters Radial 20 Circumferential 10 Y Direction (axial) 10 Results Flue"ne Rate Finance Rate Exposure Rate Exposure Rate Energy (MeV) Activity (Photons/se) MeV/em*/sec MeV/cm/sec mR/hr mR/hr No Buildup With Buildup No Buildup With Buildup 0.015 9.493e+01 5.502e-07 5.664e-07 4.720c-08 4.858e-08 0.04 3.013e+02 7.65ie-05 1.057e-04 3.384e-07 4.674e-07 0.05 7.422et0l 3.9141-05 6.382v-05 1.043c-07 1.700c-07 0.06 5.337c-02 4.787e-08 9.413e-08 9.508e- I 1 .870c-10 file://C\Programn Files\MicroShield 8\Examples\CaseFiles\HIML\1HBPP Eul 54 eff-ER-O0... 6/12/2012 25

Case Summary of 44-10 effEu-154 Page 2 of 2 0.08 8.433e-02 1.526e-07 3.71 Oe-07 2.41I4c-10 5.871c-10 0.1 5.53 1e+'02 2.37c-06 6.3ý5e-b6' 0.15 1.569e+00 8.386c-06 2.272c-05 1.38 Ie-08 3.74 1e-08 0.2 9-.397e+OI 7-.503c-04, 1.925e-03 1.324e-06 0.3 2.894e+00 3.962e-65 9.062c-05 7.Si 5 C-08-Os 1.719c-07 4.604e-04 42 0.4 1.103c+0 1 21203e-64 . 92e-0-7 8.971 e-07 0.5 6. 104e+00 1.632c-04 3.171c-04 33.203&-07 6.224c-07 0.6 8.886e+0 I 3.0 13c-03 5.52le-03 5.882c-06 1.078e-05 0.8 '5.145e+02 2. 538e-02 4.266e-02 4.827c-05 *8.114e-05 1.0 4.249e+02 2.7499e-0 4.426e-02 5.1 5§C,-05 1.5 5.353c+02 5.934e-02 8.482c-02 9.983e-05 I .427c-04 2.0 2.329e-02 3.702e-06 5.007e-06 5.725c-09 1.7443e-69 Totals 2.703e+03 1.186e-01 1.844e-01 2.106e-04 3.284c-04 filc:/CAProgram Files\MicroShield 8U.xarnplcs\CaseFiles\HTML\HBPP Eu154 cff-ER-00... 6/12/2012 26

Eu-1 54 Microsoft Excel E Calculation Sheet Energy Energy Exposure Energy Ei (MeV) (keV) Rate Response (cpm/pCi/g)

(mR/hr-1 pCi/g) cpm/mR/hr) 0.015 15 4.86E-08 0 0.04 40 4.67E-07 0 0.05 50 1.70E-07 0 0.06 60 1.87E-10 4,320,000 0 0.08 80 5.87E-10 4,500,000 0 0.1 100 6.33E-06 4,680,000 30 0.15 150 3.74E-08 4,770,000 0 0.2 200 3.40E-06 3,420,000 12 0.3 300 1.72E-07 2,610,000 0 0.4 400 8.97E-07 2,070,000 2 0.5 500 6.22E-07 1,575,000 1 0.6 600 1.08E-05 1,080,000 12 0.8 800 8.11E-05 765,000 62 1 1000 8.16E-05 630,000 51 1.5 1500 1.43E-04 425000 61 2 2000 7.74E-09 333,000 0 I. + + *1 t t I 4 4 Ej Total 230 27

Energy Response for Ludlum Model 44-10 I0 C..?

0 I

0.1 10 100 1000 10000 Gamma EaeWg (Iw) _____________

28

Attachment 1 Cs-137 and Am-241 Source-to-Detector Distance Effects 29

Experiment Data Sheet Time Started 112411 F "'-.-6.SAF Detector Model S/N Data logger S/N Cal Due Det.A ,Xp'Art 7 1/3-4,8 1(/1it If R 0 3 ,LJ9LI I ,I /,-a,I Det B. .2sI ,ser .. I 4- ý ,811 t-41?/,ad /4 f- t- ol3?1 /. /j igho,.-A ISource I1D feet Det. A Det. B 1 22qV 2(

2 .932441 024a.R 4 ~ A72 g2 ( R'Z r_

Istl-mDet.

2T 17 I cl4 eS 0 ;7 3 17 9&

A 83 4, 109 !

1 51.

DeE. 8 lo1Q zi OLL41 All counts are for 1 min.

Technician ~-

Technician 30

Experiment Data Sheet Date 5 Time Started joqS_

Name Detector Model S/N Data logger S/N Cal Due Det. A .5c,'31e .J7 4/ I3", / (,qJl ge,5qq aj;/, V1,;ý Det B. ck 37,21 1 43 AJD~~

, Ish ý8 I Background - I min. Det. A Det. B 1 1~V7 011 2 104 9 3 Iq AIs 6 I a JAI 7 6 A00oo 8 i.?l?

9 204 ___

10 215I Feet:z ,'5 .

Contact - 1 min. Det. A Det. B feet - 1 min. Det. A Det. B 3

420 j 003

(ý 3o0.5

' 13 2 1

2 3

.2709 1-

.2_'7(_o

.a27yo .

oLgs 4-/

ioo 3alo5 K

2 S 2(a 11A03 1

,,;1 cm - 1 rain. Det. A Det. B * -+2 cm - I mi Det. A Det. B 1 2, Q"75 I 1 R 2 a I0go jp LO" 3 .24 3.)

_ _(, 2" 3 103 .2 1 4 5' onno, s a /4o3 a 7-A Technician Technician 31

Enclosure 3 PG&E Letter HBL-13-008 Gross Activity DCGL in Support of the Final Status Survey at HBPP July 11, 2012

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