Ass ssessi essing ng Sk Skin in Dose se in th the Field eld - - PowerPoint PPT Presentation

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Ass ssessi essing ng Sk Skin in Dose se in th the Field eld from m Ra Radionuclide dionuclide Cont ntaminatio amination n on th the Bo Body

Rolan and d Benk nke, PhD, , CHP Director of Business Development roland.benke@rcdsoftware.com

29th Annual National Radiological Emergency Preparedness Conference Dose Assessment Series, April 4, 2019, Orlando, FL

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Radiological Contamination Screening

• Labor intensive
• Common to many

incidents

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• Significant concern to
• Public
• Emergency workers
• Medical care providers
• Important to incident response

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Overarching Questions & Motivation

• Handling high activity sources without shielding

is dangerous, but what’s the potential for skin damage from intentional or uncontrolled radioactive material dispersal into the atmosphere?

• What count rates from contamination are a

medical concern for skin damage?

• What new software features would provide the

greatest benefits to responders in the field? 3

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Potential: Rapid assessment software for contaminated skin, clothing, & wounds

Potential to Fill Current Gap

• Contamination surveys yield
• instrument count rate*
• not dose rate
• VARSKIN computer code
• calculates skin dose
• 30 years of U.S. NRC development
• Dose rate much better for
• triage
• justifying medical treatment

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*Convertible to radionuclide activity per unit area if radionuclide identity & radionuclide-specific instrument calibration are known in the field

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Potential: Rapid assessment software for contaminated skin, clothing, & wounds

RCD―Leader in Skin Dosimetry

• Experts in software development
• C, C++, C#, FORTRAN
• Python, Java, JavaScript, JSON
• HTML, CSS, React, React Native, PHP
• MATLAB, LabView, Unix shell, VHDL

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• VARSKIN computer code
• developed by Dr. Hamby’s group over the last 10 years
• maintained by Renaissance Code Development (RCD)
• Potential fieldable smart phone app for skin dose

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Technical Objective: Skin Dose Rate

Conversion for Instrument Count Rate 6

• Necessary to quantify off-axis

detection efficiency because larger contaminated areas imply greater off-axis contributions to instrument count rate

• RCD demonstrates the solution by
• developing survey meter efficiencies for large contaminated areas from

point measurements of instrument count rate

• calculating skin doses with VARSKIN

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VARSKIN Background

• Developed for hot particles and contamination on or near skin
• Shallow dose equivalent for highest contiguous 10 cm2 or other areas
• Electron (beta) and photon (gamma) dose modeling
• Select source geometry as point, disk, cylinder, sphere, or slab
• Air gap and multiple cover layers above skin allowed
• Planar disk source selected to address varying areas of

contamination in this assessment (i.e., skin curvature not modeled)

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90Sr/90Y source

Method Summary & Example Measurement Data

• Calculated detection efficiency over

center of uniformly contaminated area from radial point measurements

• 90Sr/90Y areal detection efficiency
• 24% for 1 cm2 source
• 18% for 10 cm2 source
• 4.4% for 100 cm2 source
• 0.45% for 1000 cm2 source
• Applied planar disk source geometry
• Merged (1) VARSKIN skin doses per

unit areal contamination and (2) contamination concentration necessary to induce a meter reading

• f 100,000 cpm
• Compared skin dose rates

for various scenarios

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• Same radionuclide plotted,

different encapsulation, very different efficiency

• Source encapsulation significantly

attenuates electrons (beta particles)

• Vertical air gap of 1.3 cm
• Investigation continued with thin foil

sources for better representation of contamination on skin and clothing

Important to Include Electrons

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Investigated Contamination Size

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Point-like 1 cm2 Medium 100 cm2 Small 10 cm2 Large 1000 cm2

• Factor of 2 to 3 influence on skin dose rate from contamination

size for same instrument count rate

• Skin dose rate for highest contiguous 10 cm2 exposed

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• Emission characteristics influenced skin dose rate by factor of 3 to 6

for same instrument count rate

• Strontium-90/Yttrium-90 (90Sr/90Y), electron
• n (beta)

a) emissions

• Cesium-137/Barium-137m (137Cs/137mBa), phot
• tons
• ns (gamma

mma) ) & electrons

• ns (beta)

a)

• Priority given to Radiological Dispersal Device (RDD) threats
• Point-like, small, medium, and large contamination sizes considered

Investigated Two Radionuclides

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RDD threat sources

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Investigated Contamination on Clothing versus Skin Deposition

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• Cotton clothing reduced skin

dose rate by factor of 2 to 4 for same count rate

• 0.4 mm cotton (0.036 g cm-2)
• Point-like, small, medium, and

large contamination sizes considered

Above each point the instrument reads 100,000 cpm. Will skin dose be a concern … for both, for one, for neither?

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Conclusions of this Preliminary Assessment

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• Emergency guidance suggests 100,000 cpm* as a screening threshold for

further medical evaluation (CRCPD Handbook)

• Conversion factor for skin dose rate at the screening threshold
• Less than 0.009

009 Gy Gy h-1 per r 100,0 0,000 00 cpm

• Not more than 0.002

002 Gy Gy h-1 per r 100,0 0,000 00 cpm for most scenarios

• Deterministic effects to unbroken skin expected at skin doses of 2 − 3 Gy
• Sufficient time exists for self-decontamination or monitored decontamination

at community reception centers to prevent skin damage

• Irradiation damage to unbroken skin appears less critical for medical

intervention at this screening threshold

• Potential radionuclide uptake & internal doses justify further evaluation

*Much lower levels are recommended for broken skin and contaminated wounds

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Is there interest in field software to convert survey count rates from contamination on the body to skin dose rate

• r effective dose rate?

VARSKIN Status & Prospects

• VARSKIN currently calculates skin dose rate from

radionuclide activity and geometric inputs

• We show how VARSKIN could be modified to produce

skin dose rates from survey count rates in the field

• Recall upper value 0.009 Gy h-1 to skin per 100,000 cpm*
• Factor varied by more than an order of magnitude in this study
• Single value could be useful for triage

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*Screening threshold for electrons (beta) & photons (gamma); lower levels apply to alpha particles

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Feedback requested:

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Potential: Rapid assessment software for contaminated skin, clothing, & wounds

What features are most wanted?

• Current survey equipment does not provide

dose rates from contamination on the body

• Psychosomatic issues cannot be ignored,

despite ruling out serious skin damage

• Dose rates can be calculated, but is it better

to emphasize GM pancake probes or other survey instruments during initial screening?

• Contaminated wounds require much less

radioactivity to become medically significant

• REAC/TS implements contaminated

wound modeling per NCRP Report 156

• What field software features

do you want?

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