appears to be a valid assumption in the case of thermal burns, and, if
true, indicates an IDs for man in the range of 5000 beta rep whole
body exposure «=!
However, from a practical point of view, considering
a fall-out radiation field, these values are probably academic in nature.
The ratio of measurable gamma radiation in air to beta radiation, plus
unmeasured low energy gamma radiation on the skin, under clothing indicates that the gamma radiation dose is the limiting exposure .20/
The
short range of beta particles practically necessitates actual deposition of fall-out particles upon the skin in order for skin burns to
occur.
The measurement of the effective beta plus low energy gamma
rediation to the simultaneously measured gemma radiation may be re-
ferred to as the beta/gamma ratio.
studied by many investigators.
140/1.
This beta/gamma ratio has been
The values obtained vary from 3/1 to
These differences are primarily due to the methods » instrumen-
tation, and detector geometry used.
When comparing dosage of beta and low energy gamma radiation
received by the ankle, protected by a layer of clothing, to a filn
badge worn on the shoulder, a ratio of 2.5/1 has been obtained.
Other
investigators using laboratory techniques and making direct surface
measurements of beta to gamma intensities have arrived at a value of
140/1 or even higher .22/ Since the range in air of fall-out beta particles is about six feet, the ratio of intensities will increase as
measurements of radiation dose are made closer to the source.
It is possible to equate the observed degree of skin damage
suffered by the Marshallese natives during Operation CASTLE to known
27/ Broido and Teresi, Tolerance in Man to External Beta Radiation,
Technical Manual No. 4, USNRDL, August 1954.
28/
29/
Brennen, J.T., Beta-Gemma Skin Hazard in the Post-shot Contamin-
ated Area, UPSHOT-KNOTHOLE Proj. 4.7, December 1953, CONFIDENTIAL.
Condit, R.I., Dyson, J.P., and Lamb, W.A., An Estimation of the
Relative Hazard of Beta and Gamma Radiation from Fission Products,
USNRDL, AD-95H, April 1949.
87