3.4
RADIATION DOSES
The total gamna-radiation dose recaived on a penetration flight can
be broken down into two parts: the dose received in the cloud and the
dose received on the return flight. The return flight dose for the
B-578 was found to be approximately 15 percent of the total dose when
the return flight was of about 50 minutes duration. Section 2.3 of this
report explains the various direct and indirect methods used to masure
the dosage received by the crew, both in the cloud and on the return
flight. Data collected by these various methods is presented in
ail arta
TABLE 3.1.
The maximm total dose received by any crew member during a penetration flight associated with this project was approximately 16 r, as
measured by film dosimetry. Doses as high as 40 r were reconied by
dnostriments more sensitive to soft gamma radiation than film dosimetry.
It is significant to note that the highest radiation do3es received do
not correspond to the earliest penetrations, Tha dose received in the
cloud is a fimction of the average dose rate in the cloud and the tine
spent in the cloud, For each shot the first penetration usually was
made at the lowest altituds, and succeeding penetrations were mads at
higher altitudes,
This plan was followed so that in the event turbulence was encountered, it could be tolerated better at the lower altitude, Thus
the earliest penetrations were made through the stem of the cloud.
Since the dose rate in the stem was lower than the dose rate in the
mushroom at the Same time after detonation and since the diameter of
the stem was a third to a half of that of the mushroom, lower dosages
were received by the crews who made the earlier penetrations of the
Stem of the cloud than by those crews who made later penetrations of
the mushroom,
This was true for all shots.
3.6 CONTAMDUTION FACTOR
The contamination factor was defined and discussed in Section
2.309. Valuss given in Table 3.1 are from computations made using eech_
“of the methods of calculations which were desccibad, The average con-
tamination factor for B-57B aircraft is 0.6 ¢ 0.2 percent per minute,
Both methods of caleulation gave about the same valus, With a contam
{nation factor of this magnitude, a return to base flight of several
hours duration after an early penetration of a radioactive cloud would
result in a radiation dose to the crew, during the return flight, of
about 25 percent of the total dose,
The contamination factor for any particular type of aircraft is a
furction of the distance between the crew compartment and the residual
contamination on the aircraft, In gensral, the engines are the mosthighly contaminated portion of the aircraft after flight through a radio-
active cloud,
Project 2.8 of Operation TEAFOT measured contamination
factors on several different types of aircraft and concluded the contam=
ination factor to be higher for those aircraft where the crew compartment was close to the engine or engines,
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