Chapter 5
CONCLUSIONS and RECOMMENDATIONS
5.1 CONCLUSIONS
The ganima radiation field over fallout-contaminated ocean was successfully surveyed by
aerial detectors after Shots Zuni, Navajo, and Tewa.
Shots Cheroxee and Mohawk,
No fallout was found in the sea following
Contamination on the aircraft determined the minimum detectable dose rate over the sea.
Airborne radioactive material was encountered by the survey aircraft on D+1 day after Shot
Flathead.
These isodose plots therefore were limited to the relatively hot close-in fallout area.
5.1.1 Altitude Absorption. The field measurements of gamma dose rate at various altitudes
over contaminated land and water areas agree with the relationships developed by theoretical
calculations.
A 500-kev average gamma-emission energy was assumed, and this is substantiated by the
ratio of readings of an energy-dependent detector compared to the readings of an energy-
independent detector.
5.1.2 Fallout Distribution. A land-equivalent isodose plot may be inferred from the surveys
over the sca. For example, a fallout density of 0.36 megacurie/naut mi’, ona land surface, will
result in 1 r/hr at 3 feet from the surface. The same fallout density in the sea, after mixing,
will result in 0.88 mr/hr at 3 feet from the surface (Section 1.3.4), However, the location of
the isoduse contours must be corrected to the location of the ocean surface at the time of fallout.
The ropeat surveys on subsequent days after the shot indicate the distortion of the contours, and
the direction and magnitude of the ocean currents at the surface. The 0.1 r/hr gamma dose rate
at Parry Island 24 hours after Shot Tewa agreed with its location between the 0.025 and 0.25
r/he land-equivalent isodose contours determined fromthe aerial survey over the sea.
The land-equivalent conversion is based on uniform mixing of the fallout in the sea to a depth
of 60 meters. Samples of sea water from various depths provided the data on which this estimate was based. While only a fewstations could be sampled, the reproducibility of the areas
enciused by the isodose contours from aerial Surveys on succeeding days indicate that the mix-
ing becomes stabilized for a reasonable number of days after a shot.
3.1.3 Material-Balance Estimates.
The conversion from fission-product contamination den-
sity to gamma dose rate could not be conclusively validated from the data available. However,
estimates were made based on the calculated factors.
The measurements show no detectable fall-
out from the air burst, Shot Cherokee.
The two water-surface shots. Flathead and Navajo,
fallout in the local area
3
Shot Zuni was fired on a land site, and its fallout accounted for:
“It is possible that the soil picked upin the fireball provides relatively heavy
particles which, on condensation, fall to the surface faster than the products resulting from a
water shot.
The fallout from Shot Tewa, fired ona reef site, was approximately