“a
.4
2.
CONTAMINATION
The 23 nuclear tests
H-bomb
shot
of
1954,
from 1946 to 1958, and
deposited
radioactive
Bikini Atoll, including the lagoon.
in
particular the Brayo
fallout
unevenly
throughout
Over the past 26 years, contamination
has diminished through spontaneous decay, and in the case of the lagoon, by
exchange of water with the open sea.
The most important remaining nuclide
is cesium-137 (half-life, 30 years).
Also present but much less important
is strontium-90 (half-life, 29 years).
Traces of the transuranic elements
are also present (plutonium-239, -240; americium-241), but contribute very
little to the total dose.
In the discussion that follows, the level
activity)
is expressed
in picocuries
substance
as
the
of
1987,
pCi/g signifies that
emits
a
burst
of
in one
radiation
earliest
of radioactivity (specific-
per gram
that
(pCi/g)
of soil
resettlement might
or other
occur.
gram of substance one atom disintegrates
every
occurring potassium-40 in soil
27
seconds.
For comparison,
One
and
naturally
ranges between 0.5-0.8 pCi/g (9, p. 30); in
sea water it is about .03 pCi/g.
2.1
Lagoon
The nuclear shots that occurred at Bikini
(Appendix C) affected
the floor, water and sediment of the lagoon.
2.1.1
the
lagoon.
Floor.
During
Three shots in particular affected the floor of
Operation
Crossroads
in
1946,
11
ships
sank
to
the
bottom, five during the Able shot and six including the carrier Saratoga
during the Baker shot (Figure 2, sunken ships).
These ships carried fuel,
‘loaded guns and stores of ammunition.
The remnants of several
observation towers also lie on
the bottom, near Lomilik Island (B4, Figure 2).
50000 lb
17