radon in groundwater - Mark- och vattenteknik - KTH
radon in groundwater - Mark- och vattenteknik - KTH
radon in groundwater - Mark- och vattenteknik - KTH
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Kirlna Skeppström TRITA LWR.LIC 2032Detailed study on LjusteröThe results of the detailed study are presented<strong>in</strong> Fig.7. The observed concentrationof 222 Rn <strong>in</strong> <strong>groundwater</strong> tended to <strong>in</strong>creasewith <strong>in</strong>creas<strong>in</strong>g concentration of uranium(total U) and radium ( 226 Ra) <strong>in</strong> the solution.However, the correlations were weak, 0.16and 0.18 for 238 U and 226 Ra respectively. Thisobservation supports the concept that <strong>radon</strong>concentration <strong>in</strong> <strong>groundwater</strong> pr<strong>in</strong>cipallycomes from its parent elements ( 238 U and226 Ra) deposited on the surfaces of fractures(Åkerblom and L<strong>in</strong>dgren, 1997). Regard<strong>in</strong>gground measurements of equivalent uranium(eU) made directly on outcrops, it could beobserved that high <strong>radon</strong> concentrationscould occur <strong>in</strong> bedrock of low to moderateuranium content. It was also observed thatthe <strong>radon</strong> concentration <strong>in</strong> <strong>groundwater</strong> didnot <strong>in</strong>crease with <strong>in</strong>creas<strong>in</strong>g content of uranium<strong>in</strong> the bedrock. The same observationwas made for the analysis of 222 Rn <strong>in</strong><strong>groundwater</strong> and airborne uranium measurements.These observations could beexpla<strong>in</strong>ed by the fact that the bedrock identifiedby visual <strong>in</strong>spection above the groundsurface might not be the same <strong>in</strong> the subsurfacewhere <strong>groundwater</strong> is extracted. Anotherplausible argument relates to the migrationof radionuclides (ma<strong>in</strong>ly 226 Ra and238 U) <strong>in</strong> <strong>groundwater</strong> flow. The bedrockmight orig<strong>in</strong>ally conta<strong>in</strong> low concentrationsof act<strong>in</strong>ide but transportation of 238 U and226 Ra can contribute to <strong>in</strong>creas<strong>in</strong>g the <strong>radon</strong>concentration <strong>in</strong> the <strong>groundwater</strong>. The localconditions are difficult to identify <strong>in</strong> reality.The activity ratio of 226 Ra/ 238 U <strong>in</strong> solutionvaried between 0 and 12, which clearly <strong>in</strong>dicatesa state of disequilibrium <strong>in</strong> the<strong>groundwater</strong> system.(a)(b)(c)Fig. 7: (a) Relationship between 222 Rn anduranium <strong>in</strong> <strong>groundwater</strong>; (b) Relationshipbetween 222 Rn and radium <strong>in</strong> <strong>groundwater</strong>;(c) Relationship between 222 Rn <strong>in</strong> <strong>groundwater</strong>and measured uranium <strong>in</strong> bedrock outcrops.18