59
26-1972
Description and History: 13
5.3 years.
b ieot um-90. an emitter of beta rays, with a half-life of 29 years.
Cesium-137. an emitter of gamma rays and beta particles, with a half-
life of 30 years.
;
,
.
,
a half-life of 24,000
d plutonium-239, an emitter of alpha particles, with
years.
e.
Plutonium -240, an emitter of alpha particles with a half-life of 6,600
years.
f Americium- 241, an emitter of gamma rays with a half-life of 433
rears.
.
.
.
.
{n ‘dition to the radionuclides present in the soil and lagoon sediments
of Enewetak Atoll, other radioactive materials were present on some of
ihe islands in the form of contaminated debris. Some of this debris was on
the surface and some was In burial sites on certain islands. All of these
evidences of the nuclear test program were to have some influence on the
cleanup operation. In chapters to follow, the condition of each individual
island is described. These descriptions are based on the conditions of the
‘sland in 1977, almost 20 yearsafter the last test shot wasfired and before
any cleaning operations had begun.
WESTERN TEST RANGE: 1958 - 1972
The years between the termination of the nuclear weaponstest program
and the commencement of cleanup planning were not withoutactivity. For
a short time, the atoll lagoon was used as a target area for missiles fired
from Vandenberg Air Force Base in California. Later, that function was
transferred to the much larger lagoon of Kwajalein Atoll. In the 1960’s,
explorations and experiments on the upwelling of deep-ocean water were
conducted by the University of California at San Diego. Neither of these
operations had much effect upon the effort that would be required in the
cleanup project, although some structures were erected to provide
operations and maintenance support.
PROJECT HIGH ENERGY UPPER STAGE (HEUS)
During the time that the atoll was under the control of the U.S. Air
Force, two test firings of a developmental HEUS rocket motor were
conducted. One was conducted in 1968 and the other in 1970, both on
Enjebi. The rocket motors tested each contained 2,500 pounds of
propellant of which 300 pounds wasberyllium. Thefirst firing, in April