A Health Physics Overview of Handheld and Portable X-Ray Fluorescence Analyzershpschapters.org/northcarolina/spring2013/Blute_NCHPS... · · 2013-03-28A Health Physics Overview

A Health Physics Overview of

Handheld and Portable X-Ray

Fluorescence Analyzers

James Blute, CHP

Health and Safety Manager, RSO

2 Proprietary & Confidential

Topics

• What is X-Ray Fluorescence (XRF) and how does it

work?

• Applications of Handheld XRF

• Radiation Safety Considerations

• Regulatory Compliance

• Questions


Atom


Ionization


Hole in K Shell

K

L

M


Fluorescence

Fluorescent X-Ray


Shells

L

M

K


Example Gamma & X-Ray Emitters

not applicableSpectrum up to 50X-Ray Tube*

43214 and 59.5Am-241

1.322.1, 25.1 & 88.03Cd-109

2.75.9Fe-55

Half-Life

(years)

Gamma or x-ray energy

(keV)

Isotope

(or Device*)

Other manufacturers use Co-57 for lead paint.


X-Ray Spectra of an Adult Multi-Vitamin Pill

KeV

0 10 20 30 40


Tin

Backscatter (Compton

Scattering) with

embedded Tin peaks

KeV

0 10 20 30 40



Calcium

100 20

KeV



Titanium

100 20

KeV



Iron

100 20

KeV



Zinc

100 20

KeV



Molybdenum

100 20

KeV



Example of Analysis Results Screen


Applications


Lead Paint

Max Scatter Dose Rate about 2.5 mR/hr @ 5 cm


Models using X-Ray Tubes


Metal Alloy Analysis

Scrap Metal

QA/QC

Max Scatter Dose Rate Less Than 1 mR/hr @ 5 cm


Precious Metals – Cash for Gold – Pawn Shops

Max Scatter Dose Rate Less Than 0.1 mR/hr @ 5 cm


Consumer Products e.g., Toys

Max Scatter Dose Rate up to 40 mR/hr @ 5 cm (plastic samples)


Soil Clean-up, Mining, and Exploration

Max Scatter Dose Rate up to 10 mR/hr @ 5 cm


Analysis of Prepared Soil Samples

Max Scatter Dose Rate Less Than 1 mR/hr @ 5 cm


Art and Archeometry

Max Scatter Dose Rate @ 5 cm Varies by Sample Type


Camera - Small Spot - Weld Alloy Analysis


Camera - Small Spot – Circuit Board


Dose and Risk in the Primary Beam

0.25 mR/hr

>0.25 mR/hr?

@ 50 kVp, 0.04 mA max rating


Measurement Challenges

• Tube Voltage range is 6 to 50 kVp

• Beam area 0.3 to 1 cm2


Limitations of Handheld Dose Rate Meters

• Detector calibration and energy response

• Calibrations are at 662 keV and tend to go out

below 30 keV with few exceptions.

• Detector Volume Averaging

• The few models accurate below 30 keV are all

greater than 1 cm2.


Other Options

• TLDs

– Volume averaging, biased response at very

low energies, no estimate of EDE

• Monte Carlo Computer Modeling (MCNP)

– Benchmarking


MCNP Model of Finger Exposure looking for TEDE

0-2-4 2 4

-2

0

-4

2

4

Bone

X-ray tube

So

ft T

issue

Air


Contact Dose Rates (Rem/Hr) - 50 kVp X-Ray Tube

Quantity (US NRC Limit)

Dose Rate (rem/hr) *(various device settings)

Quantity Describes

Absorbed Dose

(NA)100 - 3000

What a TLD would measure

in the beam

Total Effective

Dose Equivalent

(5 rem/yr)

0.001 to 0.01(maximum from finger

exposure to primary beam)

stochastic risk of cancer and

hereditary effects

Deep Dose

Equivalent

(50 rem/yr)10 – 150

Non-stochastic risk such as

tissue damage & skin burns

Shallow Dose

Equivalent

(50 rem/yr)

10 – 500

(100 – 5,000 with 10 cm2

averaging)

Non-stochastic risk such as

tissue damage & skin burns


Maximum Sealed SourceIn-Beam Dose Rates

Distance50 mCi

Cd109

30 mCi

Am241

20 mCi

Fe55

5 cm 315 122 0.45

millirem per hour


Chosen Measurement Methods

• Scatter - Handheld detectors

• Primary Beam - TLDs or OSL for DDE & SDE

• Used MCNP for EDE and estimates of TLD error at lower

energies.


Dose & Risk Potential Conclusion

• Non-stochastic dose limits and effects are more limiting than stochastic effects

• Training and authorization is the foundation of the safety program for handheld open-beam use


Safe Use of Thermo Scientific Niton XRF Analyzers



Know where the beam is

Primary-Beam - High Dose Rate!




Scatter Radiation



Know when the primary beam is open

Press Trigger

“Shutter Open” LED indicators

Release Trigger


#1 Rule

Never hold samples or aim the

primary beam at yourself or

others!!



Safety Features

• PIN security to control access to

trained authorized operators

• Sample proximity sensors as

interlocks

• Shielded test stands and

accessories


Proximity Button Interlock


Backscatter Proximity Interlock


ALARA Accessories


Challenging Situations


Small Samples


Small Samples


Safe Use of Niton Bench Top XRF Analyzers


Inaccessible in the Model DXL Series



Inaccessible in the Model FXL Series



Know that “x-ray on” indicator lights mean the x-ray tube

is producing x-rays within the shielded cabinet



Know that “x-ray on” indicator lights mean the x-ray tube

is producing x-rays within the shielded cabinet


“x-ray on”indicator lights



Never tamper with interlocks. Make sure they are always

functioning properly.


Safe Sample Handling Summary

There is always a safe way to take a measurement.

• Never measure with the primary beam

aimed at yourself or others

• Never hold a sample during analysis

• Consider test stands, sample holders, and

sample placement

• Use common sense


Heath Physics Summary

• Applications are diverse – consider all available safety features, test stands, accessories

• Training and authorization is the focus of the safety program.

• Recognize the low cancer risk and focus on risk of skin, tissue, and possible eye damage from extended exposure to the primary beam

• Samples should never be handled during analysis


Licensing, Registration & Compliance


Licensing – Radioactive Sealed Sources

Two License Types

• Specific License (SL) – Requires submittal and approval of

license application, and issuance of license document, in

advance of receipt of radioactive material. Issued by

Agreement State or NRC.

• General License (GL) – Where allowed, is granted

automatically upon receipt of a properly distributed GL device.

No licensing document.


General Licensing in the U.S.

FSE

FSE

FSE

FSE

GL Not Allowed GL Allowed at Fixed Sites Only GL Allowed

WI

NV

MEMT

ID

CA

OR

WA

SD

ND

CO

TX

NMAZ

UT

WY

MS

MN

IA

MO

AR

LA

NE

KS

OK

NY

OHIN

FL

TN

GAAL

MI

IL

PA

KY

WVVA

NC

SC

RINJDE

MD

MA

CT

VT

NH

AK

HI


X-Ray Tube XRF State Regulations*

• Registration of Radiation Machines, Facilities, and Services

• Radiation Safety Requirements for Analytical X-Ray Equipment

* As established in the majority of US states, based in large part on CRCPD SSR


Open Beam & Safety Device Circular Logic

Definition:

“Open-beam configuration” means an analytical x-ray

system in which an individual could accidentally place some

part of his body in the primary beam path during normal

operation.”

Sec. H.3 Equipment Requirements

a. Safety Device, A device which prevents entry of any

portion of an individual’s body into the primary x-ray beam

path or which causes the beam to be shut off upon entry into

its path shall be provided on all open-beam configurations.


X-Ray XRF Radiation Safety Program Requirements

• Operator training (recommended)

• Written program (some states)

• Finger or wrist dosimetry (most states)

• Safety device exemption (some states)

• Equipment survey (some states)


Open Beam Equipment Surveys

• What is the objective?

• Measure Leakage Radiation? Scatter

Radiation? In-beam?

• Are there pass/fail limits? What are they?


Equipment Survey Technique


International Guidance Document IEC 62495

IEC 62495 – Nuclear instrumentation Portable X-ray fluorescence analysis equipment utilizing a miniature X-ray tubeEdition 1.0 April 2011


Highlights of IEC 62495

• Does not imply any prohibition of open beam use

• Requires interlocked sensor detecting sample

proximity, prevents X-rays from being generated for

more than 2 s if a solid sample is not in close

proximity”

• Low Count Rate Safety Sensor

• Infrared Sensor (max 5mm)

• Electromechanical Sensor (max 5mm)

• Secondary Push Button High Voltage Safety Switch

• Describes how to make survey measurements


The End – Questions?


Quantifying Potential Risk

• DDE is typically measured to estimate EDE

• DDE Severely Overestimates EDE


Radiation Protection Basics

Practice ALARA

(As Low As Reasonably Achievable)

Documents

A Health Physics Overview of Handheld and Portable X-Ray Fluorescence Analyzershpschapters.org/northcarolina/spring2013/Blute_NCHPS... · · 2013-03-28A Health Physics Overview