Vol. 7, No 1, 2010 pp. 53 - 58
UDC 77.026.34:631.423:539.16 (662.6)
ANNUAL EFFECTIVE DOSE DUE TO COMBINED CONCENTRATION OF 226RA AND 228RA IN THE GROUNDWATER SYSTEM: A CASE STUDY OF THE UNIVERSITY OF ILORIN MAIN CAMPUS, NIGERIA
Levi I. Nwankwo
Department of Physics, University of Ilorin, PMB 1515 Ilorin, Ilorin 240003, Nigeria
levinwankwo@yahoo.com
Abstract. An estimation of the annual effective dose received by the population as a result of the ingestion of 226Ra and 228Ra in the groundwater within the Main Campus of the University of Ilorin, Nigeria has been made. Groundwater samples from existing boreholes sited inside the campus were analyzed by γ-ray spectroscopy to determine the suitability of the water for human consumption. The activity concentration values from the analysis range from 0.03±0.02 to 4.79±1.26 Bq l 1 for 226Ra and from 0.01±0.00 to 4.79±1.82 Bq l 1 for 228Ra. The computed annual effective dose received by the population as a result of the ingestion of 226Ra and 228Ra is thus estimated to range from 0 to 0.49 mSv y-1 and 0.003 to 1.21 mSv y-1 respectively. The total annual effective dose received as a result of the combined ingestion of 226Ra and 228Ra is consequently found to range from 0.003 to 1.45 mSv y-1 with an average of 0.59 mSv y-1. It is therefore, observed that although the average combined contribution of 226Ra and 228Ra activities to the committed effective dose from a year's consumption of drinking water in the study area is less than the ICRP’s recommended limit of 1 mSv y-1, the groundwater from some of the boreholes is more than 1 mSv y 1. For this reason, it is recommended that adequate measures should be taken to protect the young populace in the study area from consuming radiologically unsafe drinking water from the affected borehole.
Key Words: radioactivity, groundwater system, spectroscopy, effective dose and Nigeria
GODIŠNJA EFEKTIVNA DOZA USLED ZAJEDNIČKOG EFEKTA KONCENTRACIJA 226RA I 228RA U PODZEMNIM VODAMA: STUDIJA SLUČAJA NA UNIVERZITETU ILORIN MAIN CAMPUS, NIGERIJA
Izvršena je procena godišnje efektivne doze dobijene od stanovništva kao posledica unosa 226Ra i 228Ra iz podzemnih voda iz oblasti na kojoj se nalazi univerziet Ilorin u Nigeriji. Uzorci podzemnih voda iz postojećih bušotina na lokacijama u okviru samog univerziteta su analizirane upotrebom γ-zraka spektroskopije kako bi se utvrdila njihova pogodnost za ljudsku upotrebu. Vrednosti koncentracija dobijene na osnovu analize kreću se od 0.03±0.02 do 4.79±1.26 Bq l 1 za 226Ra i od 0.01±0.00 do 4.79±1.82 Bq l 1 za 228Ra. Izračunate godišnje efektivne doze kojima je izložena populacija kao posledica unošenja 226Ra i 228Ra u organizam je tako procenjena na vrednosti od 0 do 0.49 mSv y-1 i 0.003 do 1.21 mSv y-1 tim redosledom. Sveukupne godišnje efektivne doze koje se unesu kao posledica kombinovanog unošenja 226Ra i 228Ra se samim tim mogu naći u rasponu od 0.003 do 1.45 mSv y-1 sa prosečnom vrednošću od 0.59 mSv y-1. Smatra se da iako prosečna kombinacija 226Ra i 228Ra aktivnosti u efektivnoj dozi na osnovu jednogodišnjeg unosa upotrebom pijaće vode u navedenoj oblasti je manja od vrednosti koja je propisana i koja iznosi 1 mSv y-1, dok je vrednost uzorka iz nekih bušotina veća od 1 mSv y 1. Upravo iz ovog razloga, preporučuje se da se adekvatne mere preduzmu kako bi se mlađe populacije zaštitile od unosa radiološki neispravne vode za piće iz kontaminiranih bušotina.
Ključne reči: radioaktivnost, sistem podzemnih voda, spektroskopija, efektivne doze i Nigerija