THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD
Figure 1—Nal scintillation detector pulse-height distri~
bution (approximately the gamma-ray photon spectrum)
from a typical fallout sample with the gamma-ray line
specira from & wuclide or nuclide chains often identifi-
able in such spectra.
5. W. FE. Taomraon, USNRDL-TR-146.
The two extreme radiation spectra revealed
by this information are (2) « field of 2.8 Mev
7 BR. 3. Marner, R. A. Tavtor and C. S. Cook.
Nuelennics 14-8, 69 (August 1956),
source radiation.
Experimental measurements of radiation
spectra have been made for the simple case of
fallout on level land. The spectrumis a fune-~
tion of the direction of the radiation as shown
in Figure 2. This data wae taken 9 days
following the detonation (when the 105 kev
deposited with the fallout from the bomb cloud.
These 5 isotopes tell most of the story in the
time span from 2 hours to 3 months following
the detonation. Each isotope becomes most
prominent (to the extent of 20-50 percent of
the gamma ray intensity) in the spectra about
1.5 half-lives after the time of detonation.
tion, the very penetrating and biologicallyeffec-
a Fae Sooted
tive 2.8 Mev quanta may be found in abun-
dance. Four days following the detonation the
105 kev quanta from Np* generally constitutes
a very large fraction of the quante emitted but
these quanta have relatively low penetration
and biological effectiveness. Twenty days
after, the quite penetrating and effective 1.6
Fiaure 2.—Experimental 20~-800 kev gamma-ray photon
months after,
20 to 300 kev region of the spect ..
The pronounced peak in the intensity of 105
kev radiation traveling in the horizontal direction (90°) is due to viewing this uniformly distributed source planeat grazing incidence where
Mev quanta from La'° are prominent.
Two
the 750 kev radiation from
ZrNb* dominates the spectra,
There appears to be real differences in the
spectral composition of fallout radiation that
are of the order of 2 to 1 for the contribution
of individual gamma ray lines. These differ-
ences have been observed to be (a) character-
istic of the weapon, (6) characteristic of the
the degradation by multiple scattering of the
105 kev Np”line.
quanta aboveinducedsoil activities near ground
zero 10-20 hours after the detonation, and (8)
the 40-100 kevair scattered radiation entering
a freshly dug foxhole in a fallout area 2-10
days after the detonation.
1. F. L. Bovavar, W. E. Krearr, R. J. Marner and
C. 8. Coox, USNRDL-420,
apectra observed in vartaus directions obove a flat field
covered with fallout acticities 9 days after the detonation.
Np* line was very prominent) and shows the
the effective radiation source strength per unit
solid angle reaches a very large value. The
mosteffective use of shielding in sucha radiation
106.
(Classified.)
Jonnson, R. A, Taynor and F, M, Tomnovec,
ITR-TL7. (Classified)
(Classified)
2. ©. &. Coox, R. F. Jounson, R. L. Marner, F. M.
Tomnovec and L. A. Ween, USNRDL-TR-32.
(Classified.)
6. Los Alamos Scientific Laboratory, “The Effects of
Atomic Weapons,” U. 8. Goverament Printing
Office, Washington D. C. (1950), Chapter VIII.
DISCUSSION
R. L. Mather
Mr. Graveson
REFERENCES
(Classified)
timately mixed with the fission products and
At 10-20 hours after the detonation, in those
locations where Na” is an important contribu-
4. C.8. Coon, R. L. Marnen, A. J, Honaws, Jr, R. PF.
the horizonta) (<<90°} the radiationis all from
scattering. The 75 kev peak im the epectrum
of radiation scattered down by the air is due to
but always less than the source energy. Usually the energy of the scattored quanta is less
than 250 kev regardless of the energy of the
Joos oo
distributed in direction and for angles above
Following the emission of the quanta by the
radioactive nuclides the gamma. ray spectrum
is considerably altered by Compton seattering
from materials which support and surround the
residual radiation sources. The scattered radiation is continuous in its energy distribution
T] zh ete te
37
3.1. A. Webs, F. M. Tomwovec, R. L. Matuzr,
R. F. Jonson and C. §. Coox, USNRDL-TR-
slightly below the horizon.
The scattered radiation is more uniformly
sistent explanation of these variations.
enonRO CHEE SCALE
SUMMARY OF GAMMA RADIATION SPECTRA FROM RESIDUAL RADIATION
field is to shield against radiation coming from
region of the fallout area, and {c) a characieristic of the individual fallout particles. There
is insufficient information to make any con-
(New York Operations).
Do you know whether the sodium 24 was pri-
warily from your Teapot data, or have you
encountered this elsewhere?
Mr. LaRrrere. T don’t knowif it is Teapot.
I am sure it was Nevada,