“8=
not bean observed during our 1962 experiments,
Maxiaum values were
Mooss vci D172 for a deposition of 0.1 uC/m2, which corresponded to
.0224 uct 9172 for a deposition of 0.4 uct/n?,
In 1963, the maximum observed value was 0,024 uci 1251/% for a
J deposition of 0.62 yCi Ti3l/ny?, and a specific activity of the grass of
0.77 uli 132s 4g of dry material,
Two reasons could be advanced to explain this difference:
ae
The Windscale accident occurred in October, that is to say at a time of
year when the grass is no longer growing very auch and is less thick (is
dry material/s*), which leads to a higher specific activity than in cur
experiments made in the sumer and at the start of autumn.
b.
While the cheeical and physical nature of the 15) emitted during the
Windscale accident is uncertain, there was not more than 5% of activity
collected near installations associated with particles larger than a
nicron{!),
Moreover, results obtained by different methods have indi-
cated that 80% of the activity due to 115) was retained in the greas,
Moreover the work of Thomas (8) and Chambertain(?) and others, have
' ghown that factors of accumulation in plants for iodine in vapor fore
could be very important.
But in our experiments we have contaminated
the pasture with 1231 in finely atomized aquecus solution.
The shape of the secretion curves has show us that secondary phenomena
probably intervene, such ae: modification with tine of the fors of 123) in
the plant, washing away by rain, and taking up the 1252 again from the “mat".
These factors should be studied separately by experiments under con-
\
trolled conditions.
ceeTTS