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

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.