Today’s Nuclear Power

Nuclear power in the U.S. is made up of 99 commercial reactors — 65 pressurized water reactors and 34 boiling water reactors. In 2016 they produced a total of 805.3 terawatt-hours of electricity or almost 20% of the nation’s total electric energy generation. Majority of reactors in operation around the world are considered Generation II reactors. More Generation III reactors are coming online.

Nuclear power has been questioned about its safety. On March 28, 1979, equipment failures and operator error caused the loss of coolant and a partial core meltdown at the Three Mile Island Nuclear Power Plant in Pennsylvania. Though much of it was due to inadequate training and human factors, nuclear power plants lost credibility with the press and nation.

Other well-known accidents are the Fukushima Daiichi nuclear disaster in 2011 in Japan caused by a tsunami and an earthquake and Chernobyl disaster in 1986 in Ukraine.

The reality is that the nuclear industry in the U.S. has one of the best safety records in the world.

However, in 2012, the Union of Concerned Scientists found that leakage of radioactive materials was a major problem in almost 90 percent of all reactors in operation today. The U.S. Nuclear Regulatory Commission has indicated that radioactive tritium has leaked from 48 of the 65 nuclear sites in the U.S.

Next Generation Nuclear Power Reactors

Safety concerns and the high costs of development and operations have led to a new generation of advanced nuclear power designs.

Small Nuclear Power Reactors

Small nuclear reactors are becoming a cheaper and safer alternative to traditional nuclear power plant designs.

Advanced Nuclear Power Reactors

Newer advanced reactors are being built using simpler designs to reduce cost, increase fuel efficiency and make it safer.

 

Small Nuclear Power Reactors

Small nuclear power reactors are small modular reactors, which produce 50 to 300 megawatts compared to the traditional 1,000 megawatts of electricity. These modular reactors do not use electrically operated pumps and motors to circulate coolant and keep the reactor core at a low temperature. Rather, small nuclear power reactors have no pumps or motors. They rely on passive means using gravity and conduction to cool the reactors. This means that there are no pump or motor components that could break down, less electricity to run the reactor, and cheaper to build and maintain.

Another advantage is that they can be assembled at a factory rather than built at a project site. Instead of $10 billion or more to build traditional nuclear power plants that take a decade, small nuclear power reactors cost a fraction and can be up and running quickly.

NuScale, a nuclear reactor company, expects construction costs to be less than $3 billion for the first 12 modules. The key is to bring down the cost per megawatt per hour relative to other renewable energies. The U.S. Energy Information Administration estimates $50.90 per megawatt hour for wind, $58.20 per megawatt hour for solar, and $101 per megawatt hour for small nuclear power modules, which they hope to bring down to $85 per megawatt hour.

Generation III Reactors

Newer advanced reactors are more fuel efficient and safer. The nuclear power industry has been steady improving reactor technology for the past 50 years.

Third generation reactors are characterized by the following:

• A more standardized design vs. customized design to lower cost and speed up time to build

• Simpler yet more rugged design for easy operation and higher safety

• Safety mechanics to reduce the possibility of core meltdown, including more passive safety features (that rely on gravity, natural convection or resistance to high temperatures) that do not require active human intervention to avoid accidents

• Stronger structural design against aircraft impact

• Able to use fuel more fully and efficiently to reduce waste

• Greater use of burnable absorbers (or poisons) to extend fuel life

• Operate longer, about 60 years

Generation IV Reactors

Generation IV designs are still on the drawing board and will not be operational until 2020 – 2030. These designs will further improve safety, sustainability, efficiency, and cost.

Advantages of Generation IV reactors are as follows:

• 100 – 300 times more energy output from the same amount of nuclear fuel

• More diverse range of fuels, including raw fuels (non-pebble MSR, LFTR)

• Closed nuclear fuel cycle that consumes more nuclear waste in the production of electricity

• Improved safety features, such as not using pressurized operation, automatic passive reactor shutdown, no water leaks or boiling, and hydrogen explosion and contamination of coolant water

• Nuclear waste remains radioactive for a few centuries compared to a thousand years

Reactor Types

Generation IV reactors are broken out into thermal reactors and fast reactors.

Thermal Reactors

Thermal reactors use slow or thermal neutrons emitted by fission to make them more likely to be captured by the fuel.

Very-High-Temperature Reactor (VHTR)

VHTR uses a graphite-moderated core with a once-through uranium fuel cycle, using helium or molten salt as the coolant. Temperature can rise as high as 1,000℃. The high temperature allows heat or hydrogen production through the thermochemical iodine-sulfur process.

Molten-salt reactor (MSR)

MSR uses molten salt mixture as the primary coolant or even the fuel itself. MSR concepts rely on fuel that is dispersed in graphite matrix with the molten salt providing low pressure, high-temperature cooling. MSR has the possibility of a thermal nuclear waste-burner to help reduce nuclear stockpiles.

Supercritical-water-cooled reactor (SCWR)

SCWRs are light water reactors operating at higher pressure and temperatures with a direct, once-through heat exchange cycle. It operates at a much higher temperature than pressurized water reactors and boiling water reactors. Supercritical water oxidation is a process that occurs in water at temperatures and pressures above a mixture’s thermodynamic critical point. The water becomes a fluid with unique properties that can be used to destroy hazardous wastes. SCWRs are promising because of their high thermal efficiency (45% vs. about 33% efficiency for current light water reactors) and considerable plant simplification. The main objective of SCWR is generation of low-cost electricity.

Fast Reactors

Fast reactors directly use the fast neutrons emitted by fission to create a closed nuclear fuel cycle to burn all radioactive actinides during the production of electricity.

Gas-cooled fast reactor (GFR)

GFR is an evolution of a very-high-temperature reactor with a fast-neutron spectrum and closed fuel cycle for efficient conversion of uranium and management of actinides. The reactor is helium-cooled with a temperature of 850℃. It uses a direct Brayton cycle gas turbine for high thermal efficiency.

Sodium-cooled fast reactor (SFR)

SFR increases the efficiency of uranium usage by breeding plutonium and eliminating the need for transuranic (bigger than 92) isotopes to leave the site. The design uses an unmoderated core running on fast neutrons, consuming transuranic isotope from the waste cycle. It’s also passively safe. SFR is cooled by liquid sodium and fueled by a metallic alloy of uranium and plutonium or spent nuclear fuel or waste of light water reactors. The use of liquid metal instead of water as coolant eliminates the risk of explosion when sodium comes in contact with water.

Lead-cooled fast reactor (LFR)

LFR has a fast-neutron-spectrum lead or lead/bismuth eutectic (LBE) liquid-metal-cooled reactor with a closed fuel cycle. The fuel is metal or nitride-based containing uranium and transuranics. The LFR is cooled by natural convection with a reactor outlet coolant temperature of 550℃, up to 800℃ with advanced materials. The higher temperature enables the production of hydrogen by thermochemical processes.

These advanced nuclear power reactors are designed to improve safety, efficiency, cost, and longevity. It’s important that the public, politicians, and nuclear power industry help educate the benefits of the advanced designs that can help provide sustainable and safe energy for the U.S. and the world. Advanced nuclear power has to be part of our broader clean, renewable energy strategy to improve our