measurement and survey protocols defining and identifying radioactive materials
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Measurement and Survey ProtocolsMeasurement and Survey Protocols
Defining and Identifying Radioactive Materials
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OverviewOverview
• Materials disposition overview• Expected materials and isotopes• Field surveys
– Protocols and procedures– Minimum Detectable Activity (MDA) determination
• Gamma spectroscopy• Portal monitor surveys• Initial field surveys
– PEP-II Ring and BaBar
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Materials from Inside Accelerator HousingMaterials from Inside Accelerator Housing
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Expected Materials and IsotopesExpected Materials and Isotopes
• Materials:– Concrete blocks– Electronic copper cables of
various diameters and lengths
– Iron and steel plates– Electronic components and
crates including PMTs– Rubber and plastic hoses– Aluminum piping, cable
plant, and components– Special items including the
Be DHC
• Isotopes:– In Copper:
• Co-60, Fe-55, Mn-54
– In Plastic:• Na-22, Si-32, H-3
– In Lead:• Bi-207, Tl-204, Hg-194,
Pt-193, Ta-179
– In Stainless Steel:• Co-60, Fe-55, Mn-54,
Co-57, V-49, Ni-63, Nb-91, Ar-39, Ti-44
5Path Forward for Suspension Relief: 1. EvaluationPath Forward for Suspension Relief: 1. Evaluation
• Process knowledge– Identify areas and activities that can potentially activate materials
• FLUKA calculations– BaBar detector model– Other geometries model
• Confirmatory measurements– Measurement and survey protocols that follow MARSSIM
guidance• Gross beta-gamma field surveys• Gamma spectroscopy surveys• Portal monitor surveys
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MeasurementsMeasurements
• Gross beta-gamma field survey on all surfaces using an appropriate survey instrument– Detailed procedures for surveying and defining radioactive
material– Technical Basis Document
• Optimized survey instrument performance• Point-source geometry measurement efficiency as reference • MCNP calculations of measurement efficiency for an unknown
volumetric source distribution based on the point-source geometry– Source distribution for BaBar components can be estimated by FLUKA
• MDA calculated for most conservative case of source distributions
• Gamma spectroscopy survey using portable or fixed HPGe system on critical items
• Portal Monitor survey of outgoing shipments
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Field Surveys – Gross beta-gammaField Surveys – Gross beta-gamma
• SLAC uses the Ludlum Model 18 with 44-2 1”x1” NaI detector– Sensitive from <100 keV to
several MeV• Protocols per Procedure
– All surfaces of every item surveyed
• CERN protocols are similar:– All surfaces of every item
surveyed in low background area – slow scanning on contactCERN used comparable detector:
CERN used a NaI (1.3”x1.3”) that could detect down to 3.5 µrem/hr
Ludlum Model 18 with 44-2 NaI detector used at SLAC
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Field Surveys – Gross beta-gammaField Surveys – Gross beta-gamma
• Surface contamination surveys performed using a GM pancake detector (Eberline HP360, Ludlum 44-9, TBM P15)
• Protocols per Procedure– All surfaces of every item
surveyed – Swipes taken on Fe/steel for
LSC measurement for Fe-55Pantex used comparable detectors:
Pantex used a Ludlum Model 12 with a GM frisker for surface contamination.
Pantex estimated their MDAs for contamination to be about 8 dpm for alpha, 13 dpm for beta, and 60 dpm for tritium
TBM P15 used at SLAC
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Field Surveys: Minimum Detectable Activity (MDA)Field Surveys: Minimum Detectable Activity (MDA)
• MCNP then used to model volumetric activation
• Activation profile for BaBar/PEP components estimated by FLUKA
• Conversion factor used to determine MDA in field setting
2m
2cmt x 10
NaI detector (1” x 1” ) with Pb wrapFe
MCNP geometry used for volumetric model
Expected count rate per
unit specific activity, cpm/(pCi/g)
=0 2902
=0 =10 1177
=0 =20 433
uniform
214
=∞ =0.1 277
=∞ =0.2 340
=∞ =0.7 556
Eff
BKGMDA
10Path Forward for Suspension Relief: 2. Release CriteriaPath Forward for Suspension Relief: 2. Release Criteria
• Screening levels for clearance – DOE Order 5400.5
• Guidance for surface contamination (based on 25 mrem/yr)• Case-by-case approval for volumetrically contaminated
materials• ALARA principle be observed
– ANSI N13.12-1999• Guidance for volumetrically activated materials (based on 1
mrem/yr)• 30 pCi/g for most beta-gamma isotopes at SLAC such as Co-
60, Na-22, etc.
Only items without radioactivity, i.e., below MDA, would be released for recycling
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Gamma Spectroscopy SurveysGamma Spectroscopy Surveys
• Surface and/or sampling measurements with portable or fixed HPGe systems on critical items– Very sensitive instruments– Long count time required
• Critical items pre-selected• Measurement results
compared with FLUKA results to confirm FLUKA results and establish efficiencies and MDAs of measurement methods
SLAC Radioanalysis Laboratory’s fixed HPGe system
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Portal Monitor SurveysPortal Monitor Surveys
• Every truck that leaves with a non-regulated load would be surveyed by a portal monitor
Portal Monitor system at CERN
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Preliminary Field Surveys: PEP ActivationPreliminary Field Surveys: PEP Activation
• Gross survey map• Yellow shading
represents some items in the area read above background on the Ludlum Model-18
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Preliminary Field Surveys: BaBar ActivationPreliminary Field Surveys: BaBar Activation
• Past surveys suggest little activation will be found inside of detector
• Preliminary survey of Muon Shield indicated no detectable activity