In the wake of the Fukushima accident, Japan and Germany, the third and fourth largest economies in the world, reexamined the place of nuclear power in their energy mix. Within a year, Japan had shut down all but two of its 50 main nuclear reactors for testing and evaluation of safety systems, with the remaining two scheduled for shutdown and evaluation soon thereafter. Two years after the tsunami shut down the Fukushima nuclear power plant, no nuclear reactors in Japan were operating; the first nuclear plant was restarted in August 2015. In 2011 Germany shut down 8 of its 17 reactors and planned to shut down the remainder by 2022. Even France, which generates more than 75% of its electricity using nuclear power, spent the first half of 2013 studying whether to reduce its reliance on this energy source.

289

Nuclear power has not proven to be as cheap or as clean as some pundits have argued. Nevertheless, nuclear power will continue as a significant source of energy over the next 50 years, and engineers are trying to improve safety at existing nuclear power plants, as well as attempting to make the nuclear power plants of the future safer still.

Regulatory agencies around the world reassessed the design and operation of nuclear power plants following the accident at Fukushima. In the United States, the Nuclear Regulatory Commission released a list of recommendations for improving nuclear power plant safety. The list included three main measures: (1) Planning for multiple natural disasters or other threats and building the capacity to support the safety functions of all reactors at a site simultaneously; (2) improved monitoring of pools containing spent fuel rods and robust backup systems for cooling spent fuel rod pools; (3) better systems for venting reactors of the type at Fukushima, in case of power loss.

Another general recommendation was for each nuclear power plant to reanalyze the earthquake and flood risks and to assess how communication and safety equipment would perform with extended power loss. The experiences at Three Mile Island, Chernobyl, and Fukushima are also influencing the design of new power plants, which include safety features that were not part of earlier nuclear power plants.

The latest nuclear power plant designs are simpler and rely more heavily on passive safety systems instead of active ones. The new designs rely more on natural forces, such as gravity and heat convection, and less on mechanical systems, such as valves and pumps. The actions of human plant operators are also less critical to ensuring safety in these newer reactor designs.

At the end of 2011, the U.S. Nuclear Regulatory Commission approved two new power plants that incorporate such principles. One of them, the Westinghouse AP1000, will be the first new nuclear power plant built in the United States since 1996. One of the advantages of this power plant is that it is much simpler structurally than were earlier plants. For example, the AP1000 has substantially fewer pumps, less control cable, less piping related to safety, and fewer safety valves. The volume of the earthquake-resistant building is also smaller (Figure 9.34). The simpler design of the AP1000 is intended to reduce construction and maintenance costs, decrease construction time, and improve safety.

290

The AP1000 is also designed to shut down safely without the need for any action by human operators and without electrical power or pumps in the event of a design failure, such as a break in a coolant pipe. Because the AP1000 uses gravity, passive circulation, and compressed gases to cool the reactor core and containment structure, there is no potential danger from failures of backup generators and pumps. There are also many active components designed into the AP1000 power plant, but they are not part of critical safety functions or are redundant to the passive safety systems.

In Europe and Japan, spent uranium fuel is reprocessed and reused, which increases efficiency and reduces nuclear waste. To recycle the fuel, depleted uranium and plutonium must be separated from certain waste materials produced during fission. The uranium and plutonium are then combined to create a fuel known as MOX (Mixed Oxide Fuel), which can be used in nuclear reactors.

MOX accounts for just 2% of the nuclear fuel used today. But if all the spent nuclear fuel in present use were recycled into MOX, it could replace three years’ worth of uranium extracted from mines around the world. One factor preventing wider adoption of MOX fuels is that plutonium can be used in nuclear weapons. Some fear that the wider commercial use of plutonium could increase nuclear proliferation. In the United States, no recycling takes place currently.

Some scientists believe that they can “bottle up the Sun” and develop a controlled nuclear fusion reaction here on Earth. Although they have succeeded in producing small experimental fusion reactors, known as tokamaks, the amount of energy required to run the reactors is far greater than the amount of energy they release. The International Thermonuclear Experimental Reactor currently under construction in France could represent the first step toward a working fusion-powered generator. If successful, it will produce 500 megawatts of power. Initial experiments are scheduled to begin in 2020.

291