Special Radiological Surveys and Techniques for Release of Materials with the Potential for Uranium Contamination

DOE-HDBK-1113-98

Radiological Safety Traning for Uranium Facilities

Module 104 - Internal Dose Control

Radon is a radioa ctive gas that occ urs natu rally in the envir onment. It

decays by alpha emission in the first of a series of very short half-life

radionuclides that decay by alpha or beta-gamma emission.

There is a simple, inexpensive alternative to determine if the

contamination is due to radon. The effective half-life for radon

radioactive decay products is about 30 minutes, compared with the

millions of years it takes for uranium to decay. The simple way to

determine if contamination is due to radon is to wait and see if it goes

away. The sample is recounted after the radon has an opportunity to

decay to lower levels. The count rates are compared, and if the count

rates are significantly different, radon is the most likely reason for the

higher initial count rate.

Special Radiological Surveys and Techniques for Release of Materials with the

Potential for Uranium Contamination

The alpha contamination detection problems mentioned in monitoring personnel

for contamination also apply to monitoring material. An added problem is that

uranium conta mination may be loc ated in areas not accessib le to survey.

DOE requires that materials used in Contamination Areas, High Contamination

Areas, and Airborne Radioactivity Areas that are being released for unrestricted

use have accessible surfaces surveyed. Materials with inaccessible surfaces

having a potential for internal contamination shall not be released without

evaluating the material on a case-by-case basis to ensure internal contamination

does not exist.

DOE values for release of uranium- contaminated material s are higher than DOE

values for rel ease of materi als contamina ted with some ot her radioac tive

nuclides found in the DOE system, such as plutonium. The difference in these