What is dosimetry?

Dosimetry is essentially how much radiation exposure you get from substances or machines that produce radiation. The science of dosimetry also deals with the effects that radiation has on the body.

Most mineral specimens produce radioactivity from .5-200  mR/hr ( milliRems per hour) measured at about 1/2 inch from the specimen. To put this in perspective take a look at the chart below which shows the radiation limits set by the government for people that work with radiation ( general public dose is about 1/5 of the worker rate)

Permissible occupational radiation dose levels are set by the chapter 10 part 20 of the Code of Federal Regulations (10 CFR 20).

Whole body dose limit for routine exposures = 5 rem/year.

Limits are based on the sum of internal and external exposure. When individual organs are exposed, the following limits apply (the whole body dose limit must still be met).

Organ Dose Limit
Extremities 50 rem/year
Skin and other organs 50 rem/year
Lens of the eye 15 rem/year

NOTICE THE RATE IS REMS NOT MILLIREMS! There are 1,000 milliRems in a Rem.

For the really gruesome facts here is an additional chart.

The effects of being exposed to large doses of radiation at one time (acute exposure) vary with the dose. Here are some examples:

Dose Rate Amount of Body Damage
50 Rems No Change
100 Rems Mild blood change, will not be noticed by the individual
200 Rems Definite signs of injury. You are beginning to get barbequed!
450 Rems 50/30 rule. 50 percent of the population will die in 30 days. You are beyond barbeque, you are now toast!

What all this means is that you would need to hold a fairly hot (50 mR)  radioactive mineral specimen in your hand for a total of 1000 hours just to reach the yearly, 50 Rem maximum for a radiation workers hands!

Check out this handy tool for calculating radiation dose from mineral specimens, ore and mine dump material.











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