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Water Desalination

Readily available drinking water is out of reach for as much as a fifth of the world’s population, a bar to human development. One solution is water desalination, which extracts salt from seawater to produce drinkable fresh water. Nuclear energy is being used for some desalination efforts, but the potential in this arena is enormous and has multiple benefits over the more common fossil-fuel based desalination.

Desalination – How and Where It Is Done

Desalination plants largely use fossil fuels, contributing to increased greenhouse gas emissions. There are about 15,000 plants producing desalinated water, most in the Middle East and North Africa—the largest is in Saudi Arabia.

Most desalination is accomplished through a process called reverse osmosis, which pressurizes seawater and forces it through a membrane against its osmotic pressure, extracting the salt. A second process, called multi-stage flash distillation, uses a steam-based process to filter salt and other minerals. It has proven less cost-effective than reverse osmosis even though it produces purer water. There are a few hybrid plants that use elements of both methods.

Any process to produce fresh water is extremely energy-intensive, which drives costs up. The cost of water differs significantly in different parts of the world.  The U.S. Environmental Protection Agency estimates that tap water averages about $2 per 1,000 gallons.  The Coquina Coast Seawater Desalination Project in Florida estimates its costs at between $6.27 and $7.74 per 1,000 gallons.

The cost differential is based on fossil-fuel-generated water. Using nuclear energy can achieve exceptional economies of scale, driving the cost down. Tunisia sponsored research on the topic and found that costs for nuclear-powered desalination were about a third to a half less than using fossil fuels, depending on the desalination technology used.

Nuclear Desalination Is Not New

Several countries have implemented nuclear desalination, including India, Japan and Kazakhstan. The latter operated a 750 megawatt thermal facility for over a quarter century, generating not only desalinated water, but process heat and electricity as well. Nuclear-energy-powered water desalination is a well-understood technology, with thousands of man-hours behind it.

Small Nuclear Reactors and Desalination: Perfect Together

More recently, Argentina, China and South Korea have developed small nuclear reactor designs specifically to generate both electricity and fresh water. These run from 5 to 330 megawatts thermal. Russia has designed a barge-like floating nuclear facility, operating at 80 megawatts thermal. Small reactor technology may be key to expanding clean, nuclear energy-based desalination.

Though nuclear energy has not displaced fossil fuels in water desalination projects, it has emerged from the background in the last several years, especially as climate change has become an important concern and small reactor technology has matured.

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