Bioassay Measurements & Thyroid Shields

[Mack Richard <MRICHAR%INDYCMS.bitnet@vmd.cso.uiuc.edu>]

Regarding the questions about bioassay measurements and when they
are required, we have utilized NUREG-1400 entitled "Air Sampling in
the Workplace" which follows the NRC Reg Guide.  This allows the
estimation of airborne releases under certain conditions and can
easily be used to estimate the need for bioassays as well as air
monitoring.  We included this approach in our most recent NRC
license renewal application and it was accepted without question.
The results of calculations using this method resulted in quite high
levels of activity that can be utilized before bioassays are
required.  We actually set our internal limits of activity use lower
and call them "screening" measurements, thus the documentation
requirements as specified in 10 CFR 20 are not required.


Regarding thyroid shields, we generally provide personnel monitoring
for individuals who have questions about the need for thyroid
shields with instructions for those monitors to be worn in the neck
area.  After a specific time period (usually at least 3 months) we
evaluate the results of the monitoring and compare them to the
recommended limits (e.g. 50 rem/yr to an individual organ).  From
the results one can establish levels for continued monitoring, use
of thyroid shields etc.  Such levels are generally reviewed and
approved by some type of Radiation Safety Committee.


The powers that be at this institution rarely understand me, so they
certainly won't be responsible for what I say.