a
dose in the experimental animal as the criterion of tactical effectiveness
ef the system under evaluation. What is this dose in the pig? To eur
knowledge this is an unknown quantity. We do have data on the amount ef
bemb radiation - in air, plus burn - to result in lethality in the swine
with a mean time of death of thirty hourg. This dose was 15,050, the tetal
rep delivered in conjunction 27.5 cal/em© (ITR-1428, Operation PLUMBBOB).
Massive doses, up to 46,000 r tetal body irradiation, have been delivered
to the pig with the 2 MEV Van der Graaf at the National Institutes ef Health
with a dese rate of about 100 r/min. These animals have survived as leng
as three days.
Some programs teach 5000 r prompt whole bedy irradiation delivered te
man is an immediately incapacitating dese. Some observers state that it
might require 25,000 r te incapacitate man. No one quotes an immediately
lethal dose. To evaluate the present system we have elected a minimum ef
5000 r and weuld aim for the experimental animal to receive 25,000 r
delivered to the animal in his particular shielded environment.
Whether
these dese levels can be achieved with the system without subjecting the
environment te impessible blast ever-pressures remains te be seen.
doubted.
It is
Bemb neutrons assume more and more impertance the smaller the yield
ef the weapen. In the small weapons, such as we will evaluate it is of
censiderable importance because ef the high neutron fluxes.
While the neutron RBE for acute effects fer swine is not knew for
certain, it is knew with a geod degree of reliability for mice as a result
of several previous field tests.
The use ef mice in the pregram will,
thereafter, allew the use of a bielegical desimeter as well as physical
desimeters, to measure the effective total dose ef radiation delivered.
The range in the literature fer RBE extends from one of 0.3 to 2.0, with
acute lethality as an end-point. In the swine, of the aize it is projected
we use, it might be as high as 1.8.
Te actually compute station distances
from greund zere we have used an RBE of 1.3 for swine, and 1.7 fer mice.
Considerable work has been done in an effort te measure separately
the air dose and tissue dose due to gamma and neutron radiation. ‘An all
inclusive technique encempassing all significant variables, adaptable
te field use, and of acceptable accuracy, has yet te be demonstrated.
More success has been obtained in the measurement ef gamma radiation than
for neutron fluxes, but there remain many unselved problems in beth. (See
La A
roe
eo aR
Operation.
Sub=project 4.2.1.
tt"
C.
os
Appendix A)
Eighty-seven swine.
To determine immediate
lethality it is required to ebserve visually these animals that are
positioned in the pretected - fram blast and thermal - envirenment.
"Immediate" has been said te be as soon as the observers can enter the
area within the safety limits as set up hy the Test Directer.
If it is
determined that observers cannot enter the area until as leng as H + 2 - 3
hours, then any finding would, of necessity, have to be extrapolated.