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General Overview of Radiation Detection and

Equipment

International Nuclear Safeguards Policy and

Information Analysis Course

Monterey Institute of International Studies

June 3, 2013

Mark Schanfein, Idaho National Laboratory

INL/MIS-11-22727

What is Radiation?

• Energy traveling through space in the form of particles or electromagnetic waves

• Examples include microwaves, x-rays, radio waves, and light

• Can be ionizing or non-ionizing

• Radioactive material – emits ionizing radiation

Source: http://www.antonine-education.co.uk/physics_gcse/Unit_1/Topic_5/topic_5_what_are_the_uses_and_ha.htm

Alpha

Beta (+/-)

Neutron

Alpha

Neutron

Gamma and X-rays

Beta

Paper Aluminium Lead Water

Source: ICx Technologies

• Nuclear materials emit unique “radiation” (alpha, beta, gamma, neutron)

• Gamma ray energies can identify material while intensity may provide insight into the amount of material.

• Gamma spectroscopy - quantitative study of energy spectra of gamma-sources

Identifying Sources w/ Spectroscopy

Source: http://en.wikipedia.org/wiki/File:Gammaspektrum_Uranerz.jpg

Sodium iodide

gamma spectrum

of cobalt-60

Sodium iodide

gamma spectrum

of cesium-137

General Detector Types

• Gas tube detectors,

– Utilize small metal tubes filled with gas, containing an electrical lead down the center connected across a potential voltage. As ionized particles interact with gas molecules inside the tube, an electrical current is induced through the lead and outputted to a readout.

• Scintillation Crystal detectors

– Comprised of materials that fluoresce when hit by a photon. The induced florescence is then amplified, processed and outputted to a readout. Added ability to characterize energies observed.

• Solid-state semiconductor detectors

– Photons from a gamma ray hit the surface of a semiconductor, creating free electrons which can be detected as an electrical current, which is then processes and outputted to a readout.

ICAS 49-5.8/Page 5

Radiation Sensor: Ionization cut away

Basic Workings of Scintillation Based Detectors

• NaI(Ti) detector consists of an NaI (thallium doped) crystal optically mounted to a photomultiplier tube.

• Incident radiation interacting in the NaI crystal fluoresce or “spark” (“scintillations”).

• The emitted light are transmitted into the photomultiplier tube where the light produces electrons.

Scintillation

crystal

surrounded

by assorted

detector

assemblies

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Source: WikiBooks.org

Basic Workings of Scintillation Based Detectors

• The number of electrons is amplified within the phototube. The signal output of the phototube is processed electronically into a pulse that signifies the incidence of a photon:

– Circuitry consisting of high voltage supply, a resistor chain array and a load resistor, RL. Voltage is applied to the resistor divider array (each of same resistance), dividing up Vdc into equal voltages which are supplied to “dynodes”

– Resulting charge from phototube amplifies from dynode to dynode within the array fed into the anode with a load resistor used to generate an output voltage, Vout

– The pulse stream is outputted with Vout directly proportional to energy deposited by radiation in Crystal

Source: WikiBooks.org

HM-5 Components

8

Basic Components of a Typical Detector

Sensor (i.e.

NaI(Ti))

Integrated

Electronics

Package

Integrated Software

Package

Co-60

=

identiFINDER™ HM5 by ICx Technologies

• The HM-5 is a handheld radiation detection, measurement, and analysis tool based on scintillation technology – one of the most frequently used tools by IAEA inspectors

• Used to search for nuclear materials, identify isotopes present, and determine the level of uranium enrichment.

Basic Features:

• NaI class instrument

• Easy to operate

• Automatic calibration & stabilization

• Digital signal processing

• Visible, audible, & tactile alarms

• Nuclear ID based on template matching

• Finder mode to locate source or possible contamination

• Integrated ancillary detectors – Geiger-Mueller tube for high dose rates; He3 tube for neutron detection.

Source: IAEA

identiFINDER™ HM5 by ICx Technologies

• The gamma dose rate is displayed as a digital readout as well as a logarithmic analog bar graph

• For gamma only devices, gamma count rate is displayed or for identiFINDER’s with neutron capabilities the neutron count rate is displayed. Both are in counts per second (cps)

Gamma Only

Gamma & Neutron

Source: ICx Technologies

identiFINDER™ HM-5 by ICx Technologies

• One or several nuclides can be listed upon successful identification

• During data acquisition of the identification process the dose rate alarms are still active but the only indication will be audible tones, messages will not be displayed

• Nuclide identification is done by comparing spectra stored in the library with the measured spectra, if a mixture of isotopes is found then results could be unidentifiable because the spectrum is so different

Nuclide The result is

rated between 1

(unlikely) and

10 (very likely)

Source: ICx Technologies

Basic Workings of Scintillation Based Detectors

• Outputted pulse stream to screen, log, etc… – Typical plot graph (gamma spectrum) of count rates (Y) vis-à-vis voltage pulse

height (X) for each gamma energy emitted from source

• Output quality – Inherent limitations given inefficient conversions of radiation to light and

subsequent generation of electrical current

Source: WikiBooks.org

Statistical

spread / the

higher the

resolution

(quality) the

more narrow

the spread

Safeguards Verification Activities

• Attribute test Pu, U and Th Materials

• Confirms the presence of plutonium in low-grade mixed plutonium/uranium mixed oxide (MOX), MOX scrap, and waste

• Presence/Absence/Enrichment of LEU, natural, and depleted U

– UF6 cylinders, process materials, scrap, and waste

• Detects the presence of natural, depleted, and LEU in containers of process materials, scrap, and waste at LEU fuel fabrication plants

• Verify % U-235 in samples (enrichment)

• Distinguish between natural (0.7% U-235), depleted (ca. 0.2% U-235), LEU (0.7 – 20% U-235), and HEU (> 20% U -235)

• Confirm that fresh low-enriched uranium (LEU) fuel is in fact, low-enriched fuel

15

Safeguards Verification Activities Cont. • Verification of Active Length of Nuclear Fuel

– Used to determine boundaries of the nuclear fuel zone in fuel pins and assemblies

– Note – the nuclear fuel zone boundaries should be measured carefully - to determine the total uranium and U-235 content of the fuel

• Detecting Undeclared Nuclear Activity – In dose-rate mode, permits detection of gamma radiation from undeclared

nuclear material processing

• Including: Fuel reprocessing, enriching uranium, and production of HEU

• Detecting Undeclared Nuclear Material – In isotope identifier mode, permits detection of undeclared nuclear

materials, which aids in identifying undeclared nuclear activities

• Including: Pu-239, U-235, Cs-137, Sr-90, Th-232, and Am-241

– Note – To confirm the presence of undeclared nuclear material, the inspector should collect a sample of the material or an environmental (swipe) sample

– Note – Secure the unknown material with an IAEA seal

16

Raider™ Hand-Held Radionuclide Identifier

• A Main Display

• B Gamma/Neutron Detectors

• C Left Control Buttons (1 & 2)

• D Right Control Buttons (3 & 4)

• E Communication LEDs

• F Speaker

• G Microphone

• H Detection LEDs

• I Power Button

• J Secondary Display

• K Alarm Beeper

A

B

C

D

E F

G H

I J

K

False Alarms

• The verification of unknown containers and materials can lead to false (positive) alarms

• Inspectors need to be aware of common commercial materials and equipment that contain small amounts of radioactive substances, including:

– Orange/yellow/green glassware colored with uranium minerals

– Orange/yellow/green ceramic ware colored with uranium minerals

– Natural phosphate fertilizer containing uranium

– Large porcelain and ceramic objects containing thorium and/or radium

– Radium painted night-glow instruments and watch faces

– Smoke detectors containing Am-241 (ionization type)

– Natural Th (camera lenses, lantern mantels, welding rods)

– Radon

– People and Bananas (K40)

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Germanium Detectors

InSpector 2000 Multi-channel Analyzer (Germanium).

Pictured laptop used to record readings from the detector.

Source: IAEA

Germanium Detectors

Uranium Spectral Features

High-Enriched

uranium spectrum

at high-(Ge) and

low- (NaI) energy

resolution Ge

NaI

185.7 keV

(235U)

60 keV

(241Am)

U, Th

X rays

22

Plutonium Spectra Relative Comparison

23

Considerations for Gamma-Ray Measurements

• Detector Type?

• Content of Source? • Single Isotope?

• Multiple Isotopes?

• Distance to Source? • Dead Time

• Poor Statistics

• Measurement Time with Source?

• Instrument Count Time?

• Your Radiation Exposure?

• Shielding?

• Collimation?

• Location of Source within Container?

• Nearest Neighbors?

Summary

• The HM-5 is a small, portable, and very powerful gamma dose-rate meter and gamma spectrometer

• The HM-5 is used by safeguards inspectors on routine inspections and Complementary Access under the Additional Protocol

• Despite the fact that it is small and portable it is an important tool – if the user is properly trained

• The HM-5 is used to

– Determine the presence of Pu, U, and Th in samples

– Determine uranium enrichment

– Determine the active length of nuclear fuel pins and assemblies

– Detect undeclared nuclear activities

– Detect undeclared nuclear material – and identify that material

• The IAEA is looking into the Raider System

25

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“May the Force be with you…..”

(Image Source – Angela Durst, DNE)