| Radioactivity can be determined by utilizing the phenomena that
is caused by the interaction of radiation with various materials
(gas, liquid, solid). The energy consumed in the interaction between
radiation and materials transforms molecules and atoms into their
ionic or excited states, and finally changes into electricity,
light, and chemical energy. So, from these quantities, we can
estimate the radiation energy and further know the quantity of
the radioisotope. "Heat" is another important form of energy resulting
from irradiation. It is well known that P. Curie had succeeded
in the detection of decay energy by means of a calorimeter. In
JAERI, microcalorimetry has been adopted to determine the amount
of 3H in neutron irradiated Li-Al alloy. Recently microcalorimetry
successfully took part in an international comparison of the radioactivity
measurement of the 192Ir source. In this case, nine per cent of the difference between
both values of the radioactivity obtained by the calorimeter and
the ion-chamber becomes an issue. The result of an analytical
research shows that the difference has resulted from the self
absorption of the source in spite of its thinness (0.3 mm). The
calorimetric measurement, having no relation to the influence
of self-absoption of the source, will give more accurate values
than the other method. |
