Internal Behavior of Europium

["Paul E Ruhter"<RUH@inel.gov>]

From: Paul E Ruhter@INEL on 09/29/97 01:45 PM


To:   radsafe@romulus.ehs.uiuc.edu
cc:
Subject:  Internal Behavior of Europium


We recently had a minor incident involving Europium-152/154/155.  We used
whole body counts to quantify the potential uptakes.  However, the activity
levels did not appear to follow the published model, albeit ICRP indicates
that the experience upon which the model was based was very limited.  We
counted them about 3 hours after the event, 24 hours later, then 96 hours
after that (5 days after the event). The two with indications of internal
uptake (positive nsasl contamination) had WBC results (at these three time
points) of  about 60 nCi, 40 nCi, and <MDA (about 4-5 nCi) and 45 nCi, 18
nCi, and <MDA.  A third individual with no indication of internal uptake
had counts of 100 nCi, 7 nCi, and <MDA.

The drop during the time between the first two counts we are attributing to
loss of surface contamination, even though showers were taken before the
first count and no surface contamination was detectable with hand-held
survey instruments. The rapid drop during the next 4 day period has us
puzzled.  Although we believe the data for the third individual suggests
that all the detectable activity was external contamination, we are
reluctant to attribute the drop between the last two counts in the first
two individuals to external contamination. Since this was an inhalation
event following the loss of contamination control, we have looked at the
possibility of a large particle size causing rapid clearance (naturally we
have no actual particle size data), but the "models" don't want to clear it
out fast enough to match the data, even assuming 25 microns.

The exposure from these amounts is relatively small, less than 50 mrem, but
we are trying to understand what is going on biologically since the INEEL
is beginning to handle this isotope and we may need to deal with it in the
future. Have any of you had any experience with Europium or bright ideas
that would be of assistance?

Thanks in advance for your help!!!  Never a dull moment in this business!

The usual, intuitively obvious but regrettably needed, reminder that I
        alone am responsible for the contents of my messages!

        Paul E. Ruhter   CHP
        Supervisor, Radiation Dosimetry & Records
        Lockheed Martin Idaho Technologies Company
        Idaho National Engineering & Environmental Laboratory (INEEL)
        e-mail:   ruh@inel.gov