Safety_Series_041_1975 - gnssn - International Atomic Energy ...

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A N N E X II
CRITICAL NUCLIDES, PATHWAYS AND POPULATION GROUPS,
AND OTHER HAZARD ASSESSMENT APPROACHES
INDIA
Identification of critical nuclides, pathways and population groups
in the neighbourhood of the Tarapur reactors [16]
Critical nuclides
In the early period of operation of Tarapur reactors 131I was the
critical nuclide since it was the m ajor activity released to sea .and
the seafood picked up the radioiodine. Since seafood in this region
is consumed fresh, I becom es important even though it is short
lived.
By the end of 1970 and 1971 the activities of other isotopes
especially that of 134+137Cs and 58+60Co increased in the radwaste
releases. Radiocaesium levels were 25 to 30% and radiocobalt levels
were 15 to 20%. Thus 131I, 134+137Cs and58+60Co became critical
nuclides for exposure consideration from liquid waste discharges.
Even though radiostrontium levels were within 2 to 3% of total,
since Sr is a bone seeker, radiostrontium becom es one of the
radionuclides of interest for exposure purposes. Other radionuclides
are short lived and are not of interest biologically for population
exposure, except 3H. The 3H released has been quite low even
during 1971 and is insignificant for causing exposure.
The air dust filter sam ples, taken on a m illipore filter paper
( 0 . 22 /um pore size) and charcoal cartridge through which air has been
filtered, did not show any significant activity above fall-out background
in the vicinity of TAPS station during 1969-71, indicating
that atmospheric release of particulates and radioiodines are not
of significance for evaluation of population exposure.
Even though the inert gas activity releases have gone up to
580 mCi /s during 1971, since these inert gases are not taken up by
biological system , they do not come into the diet. Noble gas active
nuclides decay to stable end products without giving any problem
of significant daughter product activity. Since the activity due to
inert gases can cause direct radiation exposure to the public from
the active gaseous cloud and also due to submersion, the dose in the
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