PREDICTION OF RADIONUCLIDE DEPOSITION
727
surements or operating at an extremely low power level. Therefore the
activity measured at the sampling locations was entirely from nuclear
testing.
During a four-week period, precipitation was collected through a
10.5-in.-diameter polyethylene funnel into a rain jug. Zirconium carrier was added to the collection jug prior to each sampling period. At
the end of the sampling period, the funnel was washed with 3N HNO,
and the wash was measured and added to the contents of the rain jug.
The rain jug was returned to the laboratory, its contents were measured, and then the jug was washed thoroughly with HNO, and HCl. The
contents and the wash solutions were transferred to a beaker and evaporated to dryness, the residue finally being transferred to a 2-in.-
diameter stainless-steel planchet for beta counting. The beta counter
used was a low-background thin-window flow Geiger counter that was
calibrated with the beta radiation from 7‘T1.
Air samples were collected by drawing air through high-efficiency
membrane filters during a period of two weeks. The air volume was
measured with a gas meter and subsequently corrected for the pres-
sure drop across the filter. At the end of the two-week period, the air
filter was brought back to the laboratory, allowed to decay for seven
days, and then counted.
The rainfall was measured from the volume of rain collected dur-
ing the four-week period. We have noted that, on the average, the 10.5in.-diameter funnel collected more rain for its diameter than the standard rain gauge. However this effect was at least partially offset by the
effect of evaporation during the four-week sampling time.
Measurements at the Study Farm at Tecumseh
The deposition and precipitation measurements on the Tecumseh
farm were made on a weekly basis,
Collections were made through
an 8-in,-diameter polyethylene funnel.
Stewart et al.® have reported that an 8-in.-diameter polyethylene
funnel will collect more rain than the 8-in.-diameter standard rain
gauge. Therefore, as in the case of the 10.5-in.-diameter funnel, we
expect the rainfall measurement to be higher than would be measured
by the standard rain gauge. However, because the four-week evaporation period was not available for the Tecumseh measurements, the
rainfall measurements at Tecumseh and those from the environmental
survey around the Fermi Reactor may really not be comparable. As
will be shown later on, this is probably the reason for only fair agreement
between
the
predicted
and
the measured depositions at the
Tecumseh farm.
Air samples were collected at the Tecumseh farm in the same
manner as the air samples that were collected for the environmental