Speaker
Description
Measurement of natural radioactivity in rock is very important to determine the
amount of change in the natural background activity with time as a result of any ra-
dioactive releases. It is very important to monitor radioactive substances released to the
environment for proper environmental protection. The aim of this work is to investigate
the concentration of radioactive substance in selected rock samples in a quarry site in
Ibadan for the purpose of safety assessment.
Fifteen rock samples, each of mass 1kg were collected from the quarry site in Ibadan
and then hammered into pieces before being crushed into very ?ne grain. The desired
samples were then stored in polythene sachets for 28 days so as to reach secular equi-
librium. Samples were thereafter taken to the Nuclear Physics Laboratory for counting
and analysis. The gamma analysis was performed on a 76mm X 76mm Sodium Iodide
(Thallium doped) NaI (TL) scintillation counter detector photomultiplier. Results ob-
tained showed that the ranges of the activity concentrations of 40K, 238U, 232Th in the
rock samples are 87:05?8:46 to 174:45?2:56, 8:25?1:46 to 21:35?1:25 and 1:02?0:32
to 10:63 ? 0:71Bqkg1. Activity concentrations obtained are less than that of United
Nations Scienti?c Committee on E?ects of Atomic Radiation Report (UNSCEAR) report
2000 which indicated the worldwide activity concentration of 40K, 238U and 232Th within
the ranges 140-850, 17-60 and 11-64Bqkg1 and mean 400, 35 and 30Bqkg1 respectively.
Keywords: Natural Radioactivity, activity concentration, secular equilibrium, rock samples
1Lead City University, Ibadan
1