evidence availatle from the analysis of the particle trajectories. The
maximm lateral dimension of the fallout pattern as indicated in Fig.6.5
agrees well with the constructed pattern. The density of arrival points
Snould te related t» the levels of activity; this offers rurther reason
to construct the area of peak activity to the north of Rongelap Atoll.

4.2.8

Eveluation of the Snot 1 Fallout Fattern

To determine the time of arrival of fallout, Pic. 6.13 was conStructed beset on the times as deternined from the particle trajectory
analysis. Incluced iu the analysis wes the effect of the cloud dimer
sions. Comparison of this calculatedtine of arrival with the reporied4/

time of errival cn the cuter islenis indicates the validity of the
calculated rates of fall of the particles.

comparison.

Table 6.5 presents this

,

TACLE 6.6 -— Shot 1, Comparison of Calculated and Observed Times of
Arrival of Fallout

Distance

(n miles)

Calculated Time
of Arrival (hr)

10)
50
a7
190

126

(a)

1.
2.1
Le

1
:
7

5.9

-

8.9
11
13.2
15.4

18

7.8

150
290
250
302

Observed Time (@)

| of Arrival (hr)

8

Taken from Reference 1.

The reliability of the observed times of arrival on the atolls

innebited by natives are open to some question because of poor documen-

tation.

Tris appears to be especially true of the 7 hr crrival tine

at the atoll of Rongelap.

‘he weather island of Rongerik at 126 nauti-

Cal miles reported onserved arrival times that compare well with the
Calculated values.
An attempt to deternine the average period of fallout was made

by eveluating the trajectory data as shown in Fir. 4.13.
by obtaining an average time of cessation of fallout.

This was done

‘The rate of

arrivel of fellout at How Island caused the majority of the activity
to be deposited early in the total period of fallout (see Section 5.7).
On the basis of this observation the curve indicating the time of cessa-

tior. of fellout (Fig. 6.13) was weighted showing the period of fallout

ending before all particulate had arrived.

level of gamma activity peaks.

It is at tuis time that the

Continuing fallout after inis time is of

Select target paragraph3