RADIOACTIVITY CONCENTRATIONS AND DOSE RATES OF NATURAL RADIONUCLIDES IN FISHES FROM MAJOR RIVERS IN IJEBU WATERSIDE SOUTH WEST, NIGERIA.

Abstract

Radioactivity  concentrations  and  dose  rates  of
40
K,
226
Ra  and
228
Ra  in
fishes as internal dose rates from major rivers in Ijebu water side of Ogun
State Southwest of Nigeria had been determined by gamma spectrometry
using  NaI  (TI)  detector  coupled  with  a  pre-amplifier  base  to  a  multiple
channel  analyzer  (MCA).  12  samples  of  fishes  were  collected  from  two
major  rivers  in the study  area:  Odeomi  and  Imakun.  Brycinus longipinnis
had the highest mean concentration and dose rate values of 87.07 ± 5.83
Bq/kg and 0.0078 mGy/hr respectively.  For
226
Ra,  Pylodictus olivaris  had
the highest mean concentration and dose rate of values 1.84 ± 0.63 Bq/kg
and  3.22  x  10
-7
mGy/hr  respectively.  Papyrocranus  afer  had  the  highest
mean concentration and dose rate of
228
Ra with values 7.21 ± 0.49 Bq/kg
and  8.08  x  10
-13
mGy/hr,  respectively.  The  average  dose  rate  of  the
radionuclides in the fishes was calculated to be 1.64 x 10
-3
mGy/hr which is
below the 0.4 mGy/hr limit recommended by National Council on Radiation
Protection (NCRP), (1991) as reported by Blaylock et.al  (1993) which has
no negative radiological health implication to the aquatic animals.