Spatial patterns of radiological dose from wells drilled near nuclear waste repositories

Abstract

This report describes methodology for assess ing the spatial patterns of radiological dose to man from wells drilled near nuclear waste repositories. Descriptions of the various categories of water wells and a model of a typical aquifer are presented. The equation governing the one-dimensional flow of waste in groundwater through porous media to a well is discussed. This is followed by development of a method for constructing lines of constant dose from a well located randomly in the plane of the aquifer. An "area of hazard," in which the dose to man from a well exceeds a given statuatory or •ecommended limit, is then defined within this dose pa-tern.This technique is then 1 used to compute dose and hazard profiles for wells adjacent to a reposi tory located in either impermeable or permeable bedded salt. The repository and geologic parameters employed in this example are taken from a Lawrence Livermore Laboratory report for which this report serves as a supporting document. Scenarios with impermeable salt involve waste entering the repository through the shaft/tunnel fracture zone and exiting through a single additional flaw (borehole). Permeable-salt scenarios involve waste escaping from the repository through a borehole and via interstitial flow. Cal culations are performed assuming both a single-layer (sandstone) aquifer and a double-layer (sandstone/ shale) aquifer in the strata overlying the repository, Results indicate a time-varying area of hazard from well drilling, whose size depends on the permeability of the salt, the regional hydrology, and the surface ecosystem assumed in the potential hazard calculation.ii THE ANALYTIC SCIENCES CORPORATION