Beta-Gamma Monitoring - hdbk1113cn10146

DOE-HDBK-1113-98

Radiological Safety Traning for Uranium Facilities

Module 104 - Internal Dose Control

Alpha particles are highly charged and will only travel about 2 inches in

air. Alpha particles are also stopped by the dead layer of skin. This

means that alpha particles external to the body are not a health concern.

It also means that alpha particles are hard to detect because the detector

must be close to the source of the material emitting the alpha particle.

There are many detector types available for detecting alpha

contamination. Two of the most commonly used types are scintillation

detectors and gas proportional counters. A thin window Geiger-Mueller

(GM) detector, such as a pancake probe, will also detect a small portion

of the alpha radiation emitted.

ii.

Beta-Gamma Monitoring

Proportional counters and GM detectors are well suited for detecting

beta-gamma radiation emitted by radioactive decay products in the

uranium chain. Beta-gamma radiation travels further than alpha

radiation and is easier to detect. For natural, depleted, and lower levels

of enriched uranium, the ability to measure uranium by detecting the

beta-gamma radiation from the uranium and its radioactive decay

products is about five times more sensitive than by alpha monitoring

alone.

Many surfaces that could be contaminated are porous. If the uranium

contamination is in the pores of the material or the surface of the

material is wet, the alpha radiation will be blocked. Under these

circumstances, beta-gamma monitoring is the only means of detecting

the contamination.

iii.

Monitoring Techniques