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Sample weight is crucial because some materials
has linearly correlation with the radioactivity of the sam-
ple during neutron irradiation. Radioactivitity of sam-
ple is limited by exposure time and sample weight for
a given thermal neutron flux considering nuclear reac-
tor from other possibility is neglected. Some materi-
als will create large activity with high energy gamma,
for example Cobalt-60. Therefore, irradiation of Cobalt
sample to produce Cobalt-60 required proper estima-
tion of radioactivity in reactor core, otherwise will intro-
duce instability onto the reactor environment. On the
other hand, the element with high neutron cross sec-
tion is also has limited weight allow to be irradiated,
This kind of material could absorb some thermal neu-
tron and change the kinetic particularly the reactivity of
reactor, such condition is called poissonous core which
should be avoided.

3.5 Application in Enviroment Study

3.5.1 Atmospheric pollution

This study involved with long-distance transport,precioitation,
source identification, impacts of industrial activities. Sam-
ple types involved vary from air particulate matter, wet
or dry deposition to mosses and linchens used as bi-
ological indicator. In some of these studies also anal-
ysed of soils is including to determine enrichment fac-

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