[ RadSafe ] Skyshine measurements
Ted de Castro
tdc at xrayted.com
Thu Mar 7 00:09:51 CST 2013
On 3/6/2013 8:58 PM, Victor Anderson wrote:
| Good Evening,
| This is indeed interesting. Perhaps Ted could share some of his results.
Not sure what results you'd like --- or what I may still have after I
| The trick of using 1 inch (2.54 cm) by 12 inch (30.48 cm) compensated
GM tubes is intriguing. One big question is how sensitive these
They are sensitive enough and reliable/stable enough that I could see
the annual variation in background radiation - I believe due to moisture
content in the ground. I could also look at the record and see when
rain would start - and back ground jump due to washout - when it was
raining - a decrease in background until the ground was saturated - and
when the rain was over - an increase in background as the ground dried.
All this with 10 minute counts.
Typical calibration factors for the two detector types are:
11000 counts/mREM neutron 76647 counts/mR gamma
That one time the ALS was having problems and ran in FILL mode for 2
weeks straight I was able to find all those 10 minute intervals that
were totally within beam ON times and those totally without and
determine site boundary exposure rates from FILL to be 0.6 microREM per
Neutron and 0.02 microREM per hour Gamma. Total data collected was a
couple of 100 hours each for ON and OFF periods. This I found in some
notes I saved. I also calculated the statistical significance for those
results but couldn't find that report quickly - but if memory serves it
was significant to something like 15 standard deviations.
Therefore I think these instruments - commercially available - would be
at least sufficient to determine skyshine variations with weather
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