Sources of Surface Contamination

 

Surface contamination which occurs at TRIUMF is largely composed of beta and gamma emitting activation products . It can originate and spread in the ways listed below:

1. Volatile activation products which escape from any of the systems or processes may decay into particulates and deposit on surfaces.
2. Liquid leaks from seals, joints, filters, etc. will drip onto surfaces. This will release active materials on the surfaces which remain when the liquid evaporates or is wiped up.
3. Radionuclides  will plate out in pipes, valves, etc. of cooling water systems.
4. Proton  beams passing through targets or vacuum windows eject radioactive nuclei . Vacuum enclosures connected to meson production targets are usually contaminated.
5. Maintenance work may require the handling of contaminated equipment. Without special precautions, this will certainly lead to contamination of hands, hair, tools, clothing, floors, and surroundings. Inhalation and even ingestion is then possible.
6. Machining or grinding of contaminated material will produce radioactive dust which will settle out on surrounding surfaces.
7. Carelessness in personal monitoring or in handling contaminated material will result in the formation and spread of surface  contamination.

Because it can lead to internal exposure , loose contamination  is a greater hazard than fixed contamination. There are two ways in which it may enter the body.

It can be transferred to exposed skin from which it may find its way into the mouth, or it can be inhaled as a result of resuspension. Resuspension is caused by work activity and traffic in the contaminated area which stirs up the loose contamination so that some of it becomes airborne.

Eating, drinking, smoking, and any actions which could lead to ingestion are restricted in all areas which can become contaminated with loose contamination. Work areas which do become contaminated must be cleaned up as soon as possible to prevent the possibility of spread, and unnecessary traffic in the area must be prevented.

Fixed contamination  cannot be resuspended or transferred to the skin, and is therefore an external hazard  only. The beta dose rate, especially, can be quite high at contact. For example, a beta dose rate on contact of for a contamination level of is fairly representative.