Beta-Gamma Monitoring - doe-hdbk-1113-98_reaffirm_2005

DOE-HDBK-1113-98

Radiological Safety Training for Uranium Facilities

Module 104 Internal Dose Control

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

When performing personnel monitoring it is very important to keep the

detector (i.e., the probe) close to the surface being monitored and to

move the detector slowly. If the detector is not held close to the

surface being monitored, the alpha particles may not reach the

detector. If the detector is moved too quickly across the surface, the

electronics in the instrument will not have time to respond to indicate

the amount of radioactive contamination present.