Instead, Dok measured the gamma radiation emitted by americium-~-a daughter
product of plutonium. Americium results from radioactive decay of plutonium, and
its gamma emissions are sufficiently energetic to penetrate several inches of soil.
To accomplish this measurement in the difficult environment on Enewetak, DoE
designed and built special tracked vehicles which could operate in the soft sands,
equipped them with boom-mounted, highly sensitive germanium detectors (cooled
by liquid nitrogen), and installed analysis and counting equipment in the vehicle.
The vehicle itself was air conditioned to provide a controlled environment for this
delicate equiprnent. These mobile measuring systems measured the intensity of
gamma radiation in the energy spectrum characteristic of americium. Readings
were taken at every intersection of a 50-meter grid surveyed on each island which
coarser aerial and in-situ surveys had shown to have significant transuranic
contamination.
At each location of van readings, soil samples from several depths
were obtained and were analyzed for plutoniurn-americium ratio by the radiological
laboratories. In areas of higher or irregular contamination, additional van readings
and soil samples were taken at intervals of 25, 12%, or 6% meters. Sophisticated
computer programs were developed to produce radiation contour maps of plutonium contamination, which were then used by cleanup teams to guide soil excision.
After each removal of soil, the area was re-surveyed, new van readings and new
soil samples were taken, until
acceptable limits.
residual plutonium contamination had reached
The U.S. forces which accomplished the radiological cleanup and rehabilitation throughout 1978 and 1979 typically were present in about the following groups
and strengths:
Joint Task Group Staff (DINA)
35
Army Element
430
Navy Element
5
Air Force Element
75
Support Contractor
165
Army & Air Force Exchange System
5
DoE
5
Rad-Lab Contractors
10
Mid-Pacific Research Laboratory
10
Dol and TTPI
5
Rehabilitation Contractor
Micronesian Labor
100
10
965