Nuclear Instruments and Methods in Physics Research A 422 (1999) 778 — 783 Radioactivity in milk consumed in Nigeria 10 years after Chernobyl reactor accident O.A. Osibote, J.B. Olomo*, P. Tchokossa, F.A. Balogun Department of Physics, Obafemi Awolowo University, Ile-Ife, Nigeria Abstract The average concentrations of the radioactivity in milk imported into and consumed in Nigeria, 10 years after Chernobyl-4 nuclear power plant accident, have been measured by means of a well-calibrated high-purity germanium detector. The photopeaks observed with reliable regularity belong to the naturally occurring series-decay radionuclides headed by U and Th, as well as the non-series decay type, K. Ten years after the nuclear accident, Cs was not detected in any of the milk samples in view of the possible transfer through the soil—grass—cow—milk route, the time interval being one third the Cs half-life (30.2 yr). The average total specific activity values of 23.07$7.75, 4.35$2.06 and 831.66$54.83 Bq kg for Ra, Ra and K, respectively, were obtained.  1999 Elsevier Science B.V. All rights reserved. Keywords: Radionuclides; Specific activity concentrations; Gamma spectroscopy analysis * Corresponding author. Tel.: #234 36 230290/2018. 1. Introduction The most severe civil nuclear reactor accident at Chernobyl power station [1—3] occurred on 26 April 1986. The post-impact assessment pro- gramme for the estimation of ingestion dose as a component of radiation burden of the populace in Nigeria was put in place because of the worldwide distribution of its radioactive effluents. As part of this assessment, there is a need to measure the radioactivity in foods, particularly in milk which forms a major component in the human food chain because it is consumed by people of various ages and sexes. After the decay of the short-lived radionuclides which formed the earlier phase of population radiation exposure, the later phase was the radioactive fallout consisting of caesium iso- topes (Cs, Cs) as well as isotopes of strontium and plutonium which accounted for the radio- biological significance of contamination as they were released into the environment, thereby finding their way into the terrestrial food chain. These radionuclides, when accumulated in foods and water, constitute a direct route of exposure to hu- man population when the contaminated foods and water are consumed [4—6]. Thus, in the longer term, the concern for human health, ingestion doses 0168-9002/99/$ — see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 9 0 0 2 ( 9 8 ) 0 0 9 9 6 - 6