TOPIC 4: ALARA Philosophy

Let’s understand ALARA.

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Let’s look at Radiation Protection manual and how the ALARA philosophy is emphasized.

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Optimization is keeping doses ALARA. Doses, costs, and benefits are optimized well below the limits such that doses are as low as practical, not as low as possible. Any unnecessary exposure should be avoided, and all exposures should be kept as low as reasonably achievable – which means economic and social factors are being taken into account. Optimization balances costs and benefits. Benefits result from radiation protection efforts, but also from using those same resources elsewhere. There is also an assumed detrimental cost to the working population receiving the radiation dose, but they benefit from employment and there can be other safety benefits from using ionizing radiation to perform some tasks.

A company can put the ALARA principle into practice with administrative procedures, engineering controls, and other methods.  The three fundamental techniques that you can use to minimize doses in your daily job duties are Time, Distance and Shielding.  Common sense will always play an important part in how these are applied.

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Think of a camping trip and sitting around the fire.  Put your hands close to the fire.  It gets hot … fast.  Back up just a little bit and it cools down quickly.  Your marshmellow falls close to the flames and you quickly grab it.  A little warm but it didn’t hurt. This is the same with radiation. We cannot see, taste, touch or smell it, but the radioactive source is emitting energy.

Just like a fire, one thing we can do to minimize the dose from the source is to keep the time spent near the source to a minimum.  Do what has to be done and then move on.  Keeping doses as low as you can is as much your responsibility as it is the responsibility of the Radiation Safety Officer or the company.

Remember:

Do not loiter near radioactive material

The time spent in a radiation field is directly proportional to dose

Since dose is directly proportional to time spent in the radiation field, it is a good idea to know what you are going to do near the source so you don’t linger longer than necessary.

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Remember:

Gamma radiation follows inverse square law. The intensity drops by the square of the distance.

Keep radioactive materials a reasonable distance until needed.

Working with radioactive materials is to be planned in advance.

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Remember:
For a given reduction in radiation intensity, the amount of shielding required is dependent on the shielding material’s density.  The higher the “Z” number, the more effectively it will shield gamma and X-radiation.  Since lead is more dense than concrete, it will take less thickness to provide the same shielding protection as concrete.  Recall the concepts of Half-value layer  and Tenth value layer.

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Remember that Typically, the best shield for storing the radioactive material is the container that the material was packed in to be shipped to your facility.