-41-
made during the build-up of the discharge level to 1,000 curies
per month and a reassessment of the "safety factors" that were
included in the original studies and recommendations,
authoriza-
tion has now been granted to discharge wastes at Windscale at
the rate of 10,000 curies per month.
Another area where radioactivity is being added continuously
is the Pacific Ocean at the mouth of the Columbia River which
receives low level liquid wastes from the Hanford plutonium production reactors.
The total amount of radioactivity entering the
ocean at this point is about 1000 curies per day
Energy Commission,
(U.
S. Atomic
1960).
The waters of the oceans cover 71 per cent of the earth's
surface and the mean depth for all oceans
is about 14,000
The ocean can be conveniently divided into three domains:
the inshore area,
feet.
(1)
including the intertidal zone, bays and harbors;
(2) the shelf area,
extending from the low tide line out to a
depth of about 600 feet where the bottom slope increases rapidly
towards the deep sea; and
inshore area,
(3)
the deep sea.
The waters of the
the shelf and the uppermost part of the deep sea
are thoroughly mixed by the winds and in the inshore areas by
the tides.
By contrast,
the waters of the deep sea below
the surface layer, which varies in depth but is usually about
200
that
feet thick,
are stratified and slow moving.
both vertical and
boundary
between the
identified by
a rapid
horizontal
surface and
decrease in
-_-
.
This means
mixing is
the deeper
limited.
The
waters is
temperature with depth
.
a
—~ ff bee.
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