Re: Thallium Activated Xtals and Neutron Dse Rate Measurements

["Mike Malaxos" <mike@radiationsafety.com.au>]

Hello All,
            Has anyone comments on the following:

What is the toxicity of Thallium activated NaI.  A detector was cut open
with a hand saw. Is a trace amount absorbed through the skin of the hands
liable to be hazardous.

Neutron Dose rate Measurement. An attempt was made to check the calibration
of an old neutron detector consisting of a slow neutron BF3 detector mounted
inside a 200 mm diameter block of moderator using a 50 mCi Am241 Be Neutron
source.  The detector had good gamma rejection and the source specifications
listed the neutron dose rate at 100 cm as 1.2 microSievert/h.

The detector and source were mounted 300 cm above a cement floor. I
understand that the distance above the floor should be more than 1000 cm for
sufficient scatter reduction.

A cross check with a snoopy monitor which was not in recent calibration
indicated a dose rate almost four times the expexted value.  I would image
that the Am 241 Be source dose rate would be within 10% of the expected
value.  Is the Snoopy monitor calibration way out or am I missing something?

Any comments will be welcolme.

Best Regards,
Mike Malaxos.
Radiation Safety Services
Mike@radiationsafety.com.au
69 Robinson Avenue Belmont Western Australia 6104
Phone 61 (0)8 94750011 FAX  61 (0)8 94750011


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