strument has the capability of measuring the average density of areas uf film as large
au 4 by 4 inch, even though the density ig nonuniform.
2.2.3 Photographic Film for Radioautographic Studies. One method of studying the
surface contamination and relati:-g it to the contact hazard is that of photographic film
dosimetry. To obtain accurate measurem< ts of dose rates of all tissue-damaging radiation and the distribution of this ridiation, speciai film packs were developed. These
had the following characteristics:
.
1. Size: Denial pack size of 174, by 1% inches.
2. Emulsion: Single emulston of abcut 5 mg/om?in thicknesa. A thin sine
,
emulsion oliminates the necegslty for the use ef corrections to account for the absorption of the beta radiation in the material of the film itself.
i
'
*hi-k consisting of red cellophane andthin aluminum foil.
}
3. Wrapping: (1) Individually wrapped by hand in a light-tight covoring 8.6 mg/cm?
(2) Film stacks for depth-dose
-curerncnts wrapped te arom. or: “it seribed above. A stack consisted of 30
‘iow witn 8-mg/em? paper spacers betwee: adjacent films. Two types of films were
film; (2) five of each film type placed alternately; and ,2) sufficient of the more sensitive
film to bring the total number of pieces of film to thirty.
4. Range of Sensitivity: Several types of film with varying sensitivities were
obtained in order to assure that all anticipated dose rates could be measured. Tabic 2.1
lista these films, along with their respective characteristics.
0523 and DF-19 types were tse
that as encountered.
In cvtual practice only the
inasmuch ag they covered the entire range of exposures
2.2.4 Calibration Standards. Since densities of film are relative measurements, the
accuracy of dose measuremeats made with film is no better than the standard to which
the densities refer. The standards used by the authors of Reference 6 were used for the
present study. They were Sc”-¥™ and tuballoy.
Through exposure of a particular type of film to one of these standards, a characteristic
exposure--versus-flensity curve was obtained. Figures 2.1 and 2.2 show typical curves
obtained for 0523 and DF-18 film. These curves were used to convert density measure-
.
weeee
used. The composition of each stack was as fcilows: ‘1) six to ten of the less sensitive
:
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ment; (2) actual radiation dose rates on the surface of the aircraft and the distribution of
the activity; (3) a measure of the absorption characteristics of this contamination; and
(4) measurements c, the rate of decay of the contamination as a function of elapsed time
after detonation.
16
SECRET
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7
Ee 4
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oe
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RPE
The data required to 2ccomplish the ovjectives of this project included: (1) radiation
dose rate surrounding a co.tazainated aircraft as measured by a standard survey instru-
SATE
DATA REQUIRED
OCRATE NE
2.3.
whens Ankh eee
ments to dosage for those films that had besa cxposed to fission-fragment contamination.
In order to eliminate any variation that might have resulted from varlationa in processing
conditions, control films were exposed and processed with cach batch of film. The dc=sities of these control films were averaged, and a characteristic exposure-versus-density
curve was drawn for each shot. The variation in these curves from one shot to another
was hever more than 10 percent and usually was iass than 5 percent.