Hydrogeology model of Ignalina region for Visaginas well field protection zone substantiation

Abstract

IAEA safety documents (Safety standarts… 1994; 1999a; 1999b) recommend assessing the safety framework of groundwater exploitation in the proximity of nuclear facilities. The main task of this study is to assess the results on the re-calculation of Visaginas town wellfield well protection zones (WPZ), since the Visaginas town wellfield is installed close to Ignalina Nuclear Power Plant (INPP) site and other sites of existing or planed new nuclear facilities. The numerical model used in this study is based on three-dimensional finite-element code FEFLOW 5.0 which allows modeling of groundwater flow and contaminant transport in a layered three-dimensional system. The calibrated model of Visaginas wellfield area simulated the groundwater flow in the Quaternary and Upper-Middle Devonian aquifers systems. The evaluation of well protection zones for wellfields exploiting groundwater is currently determined by the Lithuanian legal documents (HN 44:2006). As a result of modeling the groundwater formation sources were specified and dimensions of wells protection zones in sectors 3a and 3b were established. The groundwater modeling results of this study shows that the third sub-zone (3b) of WPZ should be 0.6- 1.1 km away from the wellfield fence. The long axis of WPZ extends for 4 250 m from north to south and for approximately 3 250 m from east to west. Visaginas wellfield capture zone during 50 years operation would reach the site for planned near-surface repository for radioactive waste in case of hypothetical very high wellfield capacity more than 70 000 m3/day.