G. C.
Lalor
I
NUCLEAR lNTERESTS IN THE CARlBllEAN
life of 454 years. The neutron intensity referred to the full space
is 1.2
x
10
7
3.0
X
10
7
neutrons/sec.
The neutron flux with an average energy of 4 Mev is separated
into fast and thermal by use of a cadmium shield which is trans–
parent to fast neutron and a paraffin block which thermalises the
neutron flux. Simultaneous radiation of duplicate samples one by
fast the other by thermal neutrons can be carried out.
The nuclear reations which occur are with thermal neutrons;
2iAl
n
~
28AI
28AI
~
28AI
+
Y
With fast neutrons;
28Si
11
~
28Al
+
P
28AI
~
28AI
+
Y
27
Al
n
~
27 Mg
+
P
2iMg
~
27Mg
+
Y
After irradiation the activated samples are counted by G. M. de–
tectors. This study indicates tha t neutron activation analysis
using quite simple equipment provides an automatic or semi-auto–
matic method of analysing for alumina in bauxite. Our activation–
measurement cycle used allows the analysis of 30 samples in an eight
hour day. The accuracy depends on the number of counts per sam·
pIe, number of replicates, ete., and above aH, on the quality of
the standards used. Indeed we pound reason to be suspicious of a
couple of the standards. Results have been consistently obtained
wiwtha reproducibility of beuer than
-1-
5
1
%
which when one consi–
dereserrors in the sampling of the very large quantities involved
seems reasonable, but the method has not really attracted much
attention in the industry or in the Government institution although
the equipment cost is low, of the arder of
$
15,000 (us).
FUTURE PROGRAMMES
The next programme to begin will be a survey of radioactivity.
Equipment is now on order to begin an examination
'oi
various
known sites of radioactivity in Jamaica and to conduct prelimina–
ry survey by motor vehicle of the distribution of radioactivity
