[Milsurplus] Radium at Gilbert
Ray Fantini
rafantini at salisbury.edu
Mon Sep 25 10:14:13 EDT 2006
Just wanted to take a couple minutes and write up something on the big
radiation measurement party at Gilbert. Let me start on the technique
and instrumentation, I used a Ludlum model 3 with both the 44-9 and 44-7
heads, the 44-7 is a head that works well with detecting Alpha
emissions, unlike the old "CD" counters that read primarily Gama and
Beta. This meter belongs to the environmental sciences lab here at the
university and was calibrated about two years ago. Radium base paints
are primarily Alpha emitters so I thought an Alpha sensitive head would
be best. The meter reads in Milrems per hour (Mr/h) down to a hundredth
of a mr/h per division. I did readings at two inches from the surface,
one foot and three feet away. Gilbert provided a rare opportunity to
sample many radios that have a potential for being "hot". Lets start
with T-195/R-392 meters, with the head two inches from the face of the
meter their was a reading of about 0.5 mr/h and no noticeable reading
above background further away. Of the "hot' radios they appear the
safest, their were no r-390 receivers their but would assume they are
the same. No other part of the 195/392 other then the meters had
anything above background. Next would be the TBX radio, the one TBX that
was their produced readings of around 5 to 10 mr/h on the lettering on
all the controls, with the meters being about 2 to 3 mr/h this is more
then likely because the glass blocks the Alpha particles. Alpha is
blocked by just about anything, glass, wood , paper and skin unlike Gama
that is blocked by almost nothing except lead, concrete and water. One
foot from the radio their was about a 0.5 to 1 mr/h reading and at three
feet its back to background level. An interesting thing is their was a
TBO their that was "cold" with no readings. The hottest radio their
with out a doubt was a TBY, at two inches their was a reading of 20 to
40 mr/h with 5 to 10 mr/h at one foot and 0.5 to 2 three feet away.
Using the more sensitive head could get readings from six feet away on
the TBY, so can easily see one of these setting off alarms at scrap
yards or airports. Couple other interesting observations, their was a
WS-19 that sure looked like it used radium paint but was completely
cold, always thought they had radium base paint but that one was the
same as background, GRC-9 , R1155 and all the other radios were quiet
with only maybe two other radios having small readings. Just as a foot
note if you feel that the radio being fifty or sixty years old may help
do not think it will, I am told that the radium isotope has a half life
of around fifteen hundred years so don't think any of the TBY radios
will be cold any time soon. I have tried to find out what is considered
a safe level of exposeiure for Radium but have not found any reliable
numbers. Seeing how the government reacts to r-390 meters and their
relatively low reading of 0.5 mr/h compared to the high readings from
the TBY makes you wonder. The people over at the Environmental sciences
department here tell me that there is some controversy over exposure
levels for Radium with some saying different total levels of exposure
per year and other claiming zero is best.
Ray Fantini KA3EKH
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