Environmental modeling of the intercompartmental distribution of low-level radioactive wastes

Abstract

The uranium mining in Portugal was active almostduring one century in 62 different sites. One of these sitesrefers to the former Urgeiriça uranium mine, anunderground mine which was considered to be the mostimportant uranium exploitation in the country. Thisformer mine is surrounded by small farms and countryhouses and most of the local population lives in a villagelocated at 2 km from the mine.The Urgeiriça mine was exploited between 1913 and1944 for radium extraction and from 1951 to 1991 for theproduction of uranium concentrates. The ores from thismine, as well as from other uranium mines exploited inPortugal, were processed in the Urgeiriça uranium millfacility. About 2,5 million tones of low level radioactivewastes from this facility were disposed in an open air areaoriginating the largest tailings pile of the mining area,named as the Old Dam, with an average height of 14meters covering 13,3 hectares in this region (Figure1).Fig. 1. Aerial photo of the Urgeiriça Old Dam.Since 1996 the Portuguese government had to dealwith the decommissioning of the mines, mills and otherfacilities and the rehabilitation of the mining sites.In particular, for the remediation of the Urgeiriça site,the reclamation program was announced in 2005. For thissite the rehabilitation of the Old Dam was considered akey element of the overall environmental reclamationprogram [1].Radioactivity measurements done at the Old Damshowed high concentrations for the radionuclides of the238U decay series [2]. It is also well known that thesetailings were a source of external radiation andfurthermore, a powerful source of radon originatinghigher radiation levels comparing to the backgroundvalues. Due to precipitation, water, wind and soil erosion,radionuclides could be transported and redistributed inthis region as well as in its vicinity. Therefore, peopleliving in the nearby areas could be exposed to additionallevels of radiation. This study intended to evaluate theenvironmental impacts from the Old Dam tailingsdisposal to the soil, water, and air.