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USEFUL INFORMATION

Understanding some fundamentals of radiation counting systems is essential to prudent selection of the equipment that will be purchased and deployed for these applications. This section of the catalog is intended to present some fundamental concepts to non-expert users about radiation measurement systems. It will help you understand the basic theory of radiation measurement and in selecting the type of detectors and options that will best meet your application requirements.

Nucsafe is committed to solving problems with our clients. Whether in advising about instrument capability and suitability, after-sales support, service or training, Nucsafe is here to help you get the most out of the equipment and to make its operation simple and reliable for the user.

Understanding some fundamentals of radiation counting systems is essential to prudent selection of the equipment that will be purchased and deployed for these applications. This section of the catalog is intended to present some fundamental concepts to non-expert users about radiation measurement systems. It will help you understand the basic theory of radiation measurement and in selecting the type of detectors and options that will best meet your application requirements.

Nucsafe is committed to solving problems with our clients. Whether in advising about instrument capability and suitability, after-sales support, service or training, Nucsafe is here to help you get the most out of the equipment and to make its operation simple and reliable for the user.

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Radiation Basics

Radiation is energy traveling in the form of particles or waves in bundles of energy called photons. Some everyday examples are microwaves used to cook food, radio waves for radio and television, light, and x-rays used in medicine.

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Radiation Risks

When radiation deposits energy in a person, he or she receives a radiation dose. Radiation doses are measured in units of rem or millirem (mrem). One thousand millirem is equal to one rem (1000 mrem = 1 rem).

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Detectors

Gross counting systems measure a fraction of the total radiations in such a way as to allow the determination of the presence of radioactivity above ambient background.

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Selecting a Gamma Ray Detector

The choice of gamma ray detector depends on a number of factors including their efficiency (determined in part by their density) and their peak resolution (determined in part by their light outut).

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Radiation Counting with Guardian Systems

Gross counting is used to determine the presence of absence of radioactivity in an object. Once it has been determined that radiation is present above the ambient background levels, it is necessary to determine the specific radionuclides that are present.

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Electronics and Pulse Processing

Once the radiation deposits it energy in the detector and the detector converts the energy into an electrical pulse, the system electronics process the information into a useable form, either as a count rate for gross counting systems or as an energy spectrum for nuclide identification and spectroscopy.

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Determining the Presence of Radiation, Alarm Calculations and Statisitics

How do we know if a radioactive source is present in the vehicles, pedestrians, freight or other objects being measured? How can the portable and mobile search tools determine if the radiation levels are increasing significantly or are the variations just the natural fluctuations seen in radiation measurements?

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Gamma Ray Interactions, Gamma Spectroscopy and Nuclide Identification

A typical pulse height spectrum measured with a 3×3” NaI(Tl) detector with a 137Cs source is shown in the figure. The photopeak, Compton maximum and backscatter peak are indicated. The lines around 30 keV are Ba X-rays emitted by the source.

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Gross Counting

Gross counting is used to determine the presence of absence of radioactivity in an object. Once it has been determined that radiation is present above the ambient background levels, it is necessary to determine the specific radionuclides that are present.

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Selecting a Neutron Detector

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References