Abstract
A decision-analysis methodology is applied to the problem of the migration of strontium-90 (90Sr) in ground water to the Pripyat Town water wells located near the Chernobyl Nuclear Power Plant in the Ukraine. The source of the radiostrontium is the diffuse contamination of the ground surface by radioactive fallout, which was released from the damaged reactor core in 1986. The hydrostratigraphy at the site is idealized as a three-layer system; a marl layer separates an upper, unconfined aquifer from a lower confined aquifer which is used as a source of water. Management strategies are evaluated using a risk-cost objective function. The risk is defined as the expected costs of well-field failure due to ex-ceedence of the 90Sr regulatory standard for drinking water. The probability of well-field failure is estimated using Monte-Carlo simulation techniques. This probability is most dependent upon the 90Sr regulatory standard and upon the hydraulic conductivity of the aquitard in a hypothesized annular facilitated-transport zone near the well casings. The risk-cost analysis indicates that a “no complex remedial action” alternative represents the preferred management strategy for the Pripyat Town water wells, but that the risk will increase in 25 years by about one order of magnitude. Therefore, efforts to obtain more reliable estimates of contaminant transport parameters, in particular 90Sr concentrations in the unconfined aquifer, appear warranted.
