ABSTRACT
The primary objective of Project 2.2 was to measure initial- and residual-gammaexposure rates as a function of time at various distances from high-yield-thermonuclear
“a
detonations. Secondary objectives were to measure the residual gamma-exposure rate
at the lip of the crater from a high-yield, land-surface shot; and to field test a prototype
thermal] detector to be used in a radiological-defense-warning system.
The residual-gamma radiation was detected by an unsaturated-ion chamber, whose
output determined the frequency of pulses that were recorded on electro-sensitive paper.
Most of the initial-gamma-radiation stations consisted of scintillation detectors whose
output determined the frequency of pulses that were recorded on magnetic tape. Some
initial-gamma instruments were similar to those used during Operation Castle. The
exposure vate near the crater was measured with a detector-telemeter unit dropped
from a helicopter.
Residual-gamma-exposure rate versus time was obtained after Shots Zuni, Flathead,
Navajo, and Tewa. The observed average-decay exponents for these events were 1.1 for
Zuni and Tewa, 1.2 for Flathead, and 1.3 for Navajo. In some cases, the effect of rainfall in leaching the activity decreased the exposure rate by a factorof two.
Records from Shot Flathead at 7,730 feet and from Shot Navajo at 13,870 feet indicated
that at these locations about *h of the total jnitial-gamma exposure was delivered after
the arrival of the shock front.
The crater-lip measurements indicated that the method was a feasible one; however,
no uSable data was obtained.
The thermal-radiation detector responded satisfactority to a
detonation at a
distance of 20 miles.