Interpreting info on radiation levels - 3

     Last I knew (last half of the 20th century) scientists measured radiation in roentgens. (The Documentary about Chernobyl I wrote about on March 17 spoke of "roentgens." Another article about Chernobyl used the measurement "curies.") Now I keep hearing references to microrems and  millisieverts and CPM (counts per minute).  I assume "counts per minutes" refers to clicks on a Geiger counter, if they still measure radiation with Geiger counters. And the Air Quality Management District uses something they call Beta Gross Count Rate. What's that? How do curies compare to microrems compare to millisieferts compare to CPM compare to a Beta Gross Count Rate (compare to roentgens)?
     Possibly they are measurements of different kinds of radiation. AQMD measures gamma rays. The radiation that spread over Europe from Chernobyl in 1968, was 30,000 roentgens per hour or  300 sieverts per hour (so there's a definite correlation there; 100 roentgens must equal 1 sievert). It was cesium 137 (half-life 30 years) and iodine-131 (half-life 8 days). Radiation from the Fukushima nuclear plants is apparently iodine-131. Are either or both of these kinds of radiation gamma radiation? I have no idea.
     All I've found out so far is that "normal background radiation" is 10-12 microrems/hour or 40-46 CPM or 2.4mSv (squared) which I believe refers to millisieverts. (I don't know how to make my software do the elevated 2 for "squared.") Oh, and I just found out "rem" stands for "Roentgen Equivalent in Man."  I suppose "rew" would be "Roentgen Equivalent in Woman." Getting loopy. I am way out of my depth here; the math of conversions is beyond me.
     All you need to know about radiation is, LESS IS BEST.


HALF-LIFE refers to the time for half the atoms in a radioactive substance to disintegrate. If I understand correctly, it then takes the same length of time for half of what remains to disintegrate--and so on.

HALFLIFE also refers to one of the seven books of poetry by my brother Tim Reynolds. Part of the title poem, the part I understand, goes like this:

When the light came
a piece of glass
incandescing
        ingested

an inch and a
half of copper
electrical
        wiring, a

scrap of tin and
three small pebbles,
now all fused to
        the one thing. . .



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