Environmental Problems and the Need for Geochemical Modeling

In this chapter, we introduce some of the majorenvironmental problems that our societies face, and point out the need for using geochemical modeling.

What kinds of problems are addressed or can be addressed by geochemical modeling? Some important problems are as follows.

High-Level Radioactive Waste Disposal

Nuclear power generation and weapons production have resulted in tons of spent fuel and high-level nuclear wastes. These wastes are currently stored under temporary and deteriorating conditions and are awaiting disposal in a permanent repository. In the US A. the Department of Energy is directed by the Congress to investigate the suitability of Yucca Mountain, southern Nevada, to host a permanent geological repository for high-level nuclear waste (Figure 1.1). It is proposed that the thick unsaturated volcanic tuff in the Nevada desert will be a suitable location for a permanent geologic repository because: (1) a deep groundwater table is 800 to 1 000 feet (ca. 250 to 300 m) below the proposed repository: (2) the site is far from large populations; and (3) a desert climate that has rainfall less than 6 inches (ca. 15 cm) per year limits downward percolation of water and vapor (Figure 1.2).

Before Yucca Mountain can become the nuclear waste repository for the nation, a license must be issued by the US Nuclear Regulatory' Commission. Evaluation of the site for safe storage of high-level nuclear wastes for at least 10 000 years requires a broad spectrum of scientific disciplines. Mathematical models are developed to calculate the amount and type of radioactive materials that could be released into the environment due to different processes and events.