Imagine a world in which midsize cities, factories and towns in many countries have their own small nuclear reactors to generate electricity and heat. Some would be in remote locations unconnected to the national grid but others would be in densely populated zones that need local sources of constant power supply.

By replacing plants that use coal, gas or oil for fuel, these atomic generators — emitting almost no carbon dioxide, the main global gas from human activity — would make the world a greener place. But would it be a safer one?

The question is no longer in the realm of theory. The International Atomic Energy Agency (IAEA) has estimated that global demand for small reactors could reach 500 to 1,000 units by 2040 as more urban centers, industries and outback communities seek low-carbon power not just for electricity but also for low-cost heat to desalinate seawater for drinking, run energy-intensive mines and industries, produce biomass-based ethanol and even hydrogen fuel.

Today, nearly 440 big reactors in 30 countries generate about 15 percent of the world’s electricity — including about 25 percent of Japan’s power.

The spread of nuclear technology will create new regulatory and proliferation challenges, but it will help cut global warming emissions as small reactors replace old coal-fired plants and fossil fuel heat sources for industry. In the United States, the latter account for about 16 percent of greenhouse gas emissions.

The IAEA is the U.N. agency that both promotes and polices civilian nuclear power to try to ensure that atomic energy is used solely for peaceful purposes. It defines a small power reactor as one with a generating capacity of 300 megawatts (MW) of electricity or less.

A typical 1,000-MW nuclear plant today costs between $3 billion and $5 billion to build. But this high up-front capital investment is expected to fall sharply as a series of smaller, safer and easier to operate reactors come into service over the next 20 years.

Backed by many of the leading reactor designers and engineering companies, there are at least 15 different small reactors, ranging from around 30 MW to 300 MW in an advanced stage of development in Japan, the U.S., Russia, China, South Korea, South Africa and Argentina, according to the World Nuclear Association.

Many are designed to run underground and to suit operating conditions in developing countries and small states by conforming to the general rule that no single power reactor should be larger than 15 percent of national grid capacity. The small reactors are often modular and can be scaled up as power demand and the size of the grid increases. U.S. Energy Secretary Steven Chu has described small modular reactors as “one of the most promising areas” in the nuclear industry.

Although somewhat more expensive per kilowatt of electricity, they will be much easier to finance than big reactors that take far longer to build. A new small reactor could be installed within three years to start generating income from sales of electricity and heat to pay for the next and subsequent modules as needed.

The U.S. Nuclear Regulatory Commission is preparing to start the process of approving the first of seven small reactor designs from next October. The first to be submitted is expected to be Toshiba Corp.’s Super-Safe, Small and Simple (4S) reactor.

This “nuclear battery” system, which will be offered in 10 MW and 50 MW versions, has been developed by Toshiba of Japan and its U.S. unit Westinghouse, in collaboration with the Central Research Institute of Japan’s electric power industry.

The town of Galena in Alaska has given preliminary approval for Toshiba to install a 10 MW 4S reactor, which the makers say will be able to operate continuously for 30 years without refueling, something that normally takes place every few years with current power reactors. After 30 years, the radioactive 4S fuel would be allowed to cool for a year. Then it would be removed for above ground storage or underground disposal.

The whole 4S unit would be factory-built, transported to site and installed below ground level. Cooled by liquid metal sodium, it drives a high temperature steam cycle. Both the 10 MW and 50 MW versions are designed to produce heat at a constant 550 degrees Celsius, suitable for power generation with electrolytic hydrogen production.

Toshiba plans a worldwide marketing program to sell the units for power at remote mines, to fuel desalination plants and to make hydrogen. Eventually, it expects sales for hydrogen production to outnumber those for power supply as global demand for hydrogen from industry and as a pollution-free transport fuel rises rapidly.

Meanwhile, the U.S. Energy Department announced in March that it was awarding $40 million to two international groups to finish their conceptual designs and plans for next generation reactors by August.

Both groups are proposing to build small reactors cooled by helium gas, which reaches temperatures of about 850 degrees Celsius. The heat can be used not just to drive steam turbines to generate electricity but also for industrial and district heating. Industrial applications include refining petrochemicals, fertilizer manufacture, plastic refining and hydrogen production.

A combination of improved safety and lower capital investment costs may help remove two of the main barriers to the spread of nuclear power generation. However, it will bring to the fore public concerns over safe disposal of radioactive waste, nuclear security and proliferation risks that regulators and the nuclear industry must show they can manage.

Michael Richardson is a visiting senior research fellow at the Institute of South East Asian Studies in Singapore.

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