ALARA principle in Radiation physics

[Girish Kumar]

ALARA - Defined as As Low As Reasonably Achievable

 

This is well known law in the field of radiation physics. It is evident that occupational workers in nuclear reactors, fuel reprocessing plants, accelerators etc... shall continue their work in radiation zones. Hence as they cannot avoid radiation exposure to zero level, they have to minimize it.

 

The ALARA principle says the same. The measures required by law to minimize the risk is to practice the TDS principle.

 

' T ' stands for Time ; ' D ' stands for Distance ; ' S ' stands for Shielding

 

Time ---- Radiation occupational workers shall minimize the exposure time by means of sharing the work between individuals. Hence many sites follow splitting of work in shifts which reduces the cumulative radiation dose.

 

Distance ----- While handling radioactive sources, methods shall be adapted to maintain sufficient distance from the radioactive sources to minimize the exposure. For instance, the range of alpha, beta particles, and other massive particles in air is less and hence it is comfortable to reduce exposure to about zero level by keeping them at small distances away from the body.

 

but when you handle sources emitting gamma, neutron good distance shall be maintained away from the sources to minimize the exposure though it is difficult to reduce the exposure to zero. For instance 1 meter / two meter tongs are normally used in laboratories to handle the low activity gamma / neutron sources as they obey inverse square law.

 

Shielding -- Most important aspect in reducing the exposure. Suitable shielding methods shall be incorporated to handle the sources. For particles like alpha, beta a simple economical shielding is enough to restrict the escape of radiation through container.

 

It should be kept in mind that three of the above parameters shall always be practiced simultaneously for achieving ALARA principle.

 

Hope this clarifies your query.

 

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