Chopter |
INTRODUCTION
1.1
OBJECTIVES
The primary objectives of Project 2.2 were: (1) to measure the initial-gamma-exposure
rate as a function of time from the detonation of high-yield-thermonuclear devices; and
(2) to measure the residual-gamma-exposure rate as a function of time at land fallout
stations. Secondary objectives were: (1) to measure residual radiation at early times on
the crater lip of a high-yield, land-surface shot; and (2) to field test a prototype thermal-
radiation detector to be used in a radiological~defense-warning system.
1.2
BACKGROUND
Los Alamos Scientific Laboratory (LASL) measured initial-gamma-exposure rate
versus time for high-yield devices during Operation Ivy (Reference 1). It was found
that high-yield devices did not follow the relatively simple scaling laws of low-yield
devices. Gamma radiation at 2 particular distance scales linearly with yield for devices
up to about 100 kt.
creasing yield.
For megaton-range devices, gamma radiation scales higher with in-
This enhancement of initial-gamma radiation was attributed largely to
the hydrodynamic effect (Section 1.3.4). U.S. Army Signal Research and Development
Laboratory (USASRDL) obtained several gamma-exposure-rate-versus-time data points
frorn high-yield devices during Operation Castle (Reference 2). The data obtained by
USASRDL were lower by a factor of 10 or more than the Super-~Effects Handbook predictions (Reference 3).
One of the purposes of Project 2.2 was to resolve the initial-gamma-radiation-scaling
laws for high-yield devices. Of particular interest was a high-yieid air burst, since it
would allow correlation of the hycrodynamic effect from an airburst with that from a
surface burst. USASRDL made measurements of residual-gamma-exposure rates from
high-yield devices during Operation Castle (Reference 2). Only limited data were obtained
because of a high loss of instruments early in the operation. These data indicated that
the decay exponent for the residua! activity varied with the type of nuclear device. Another
purpose of Project 2.2 was to determine accurate decay exponents for residual activity.
The thermal~radiation detector, part of an early-warning system for nuclear detonations, was .ested with low-yield devices during Operation Teapot (Reference 4). The
tests were successful. The detector showed a capability far in excess of the requirements.
It was decided to determine the response of this detector to megaton-range devices during
Operation Redwing in order to complete the testing.
1.3
THEORY
The gamma radiation emitted from a nuclear detonation may be divided into two por-