News Room – Frequently Asked Questions (FAQ)

What is the basis for the NuScale design?

NuScale plant designs are based on decades of operating experience with light water reactor technology. Water acts as the primary coolant within the reactor system. Water that is turned into steam within the steam generators also turns the turbine generator that makes electricity. NuScale fuel is similar to the fuel used in current operating nuclear plants except that NuScale fuel rods are six feet long instead of 12 feet. Each module contains 17 rows and each row holds 17 fuel rods.

What are some of the differences in the NuScale design?

First, the reactor vessel is integrated into the containment vessel and the steam generators are integrated into the reactor vessel. Instead of the large, reinforced concrete dome-shaped containment buildings seen at existing plants, the NuScale containment is a three-inch thick steel cylinder that is 60 feet long and 14 feet in diameter. The steel reactor vessel fits inside the containment vessel. There are two "helical coil" steam generators within the reactor vessel.

Second, instead of motor-operated pumps, the NuScale reactor system uses natural circulation - a convection process – to circulate water through the reactor. The NuScale design eliminates concerns about a Loss of Coolant Accident (LOCA) in other designs that could result from a break in the large pipes that connect the reactor to steam generators. In addition, there are no pumps on the reactor system that require an emergency electrical power supply for cooling if power is lost to the site.

What is meant by passive cooling and natural circulation?

Natural circulation is a passive process that does not require active mechanical equipment, such as a pump, to move water through the reactor and keep it cooled. In the NuScale system, water is heated as it passes over the nuclear fuel. As it is heated the water becomes lighter and rises within the reactor vessel cylinder.

As the water reaches the top of the cylinder, it is drawn down over the steam generator tubes where it passes its heat to a second enclosed system to produce the steam that makes electricity. When it transfers heat, the water cools, becoming more dense or heavy. Gravity pulls the heavy water down the outside of the cylinder where it is then drawn back inside the cylinder by the heat of the fuel. The overall result is a natural circular flow of water during both normal operations and when the system is shut down.

Will NuScale plants require less water for cooling?

NuScale plants will need about the same amount of water per megawatt of capacity as other thermal power plants.

How much will it cost to build a NuScale power plant?

The NuScale design has a number of economic advantages. It is modular and the components can be manufactured and fabricated at a number of facilities that already exist in the U.S. Many of the major components also use existing off-the-shelf designs. Modular components can be made off site, then shipped and installed on site, lowering costs and construction times. Modular design also enables manufacturing in volume to keep costs low.

NuScale plants also are scalable allowing multiple 40 MWe modules to operate within a single facility. Once the basic plant infrastructure is in place, new power production modules can be added and put into operation while existing modules continue to operate. The benefits resulting from volume manufacturing, shorter lead and construction times and the ability to add capacity as needed, should keep the cost of NuScale plans competitive with that of other commercial nuclear plant designs.

How long will it take to build a NuScale plant and when will the first one go into operation?

Because of the modular and scalable design, NuScale anticipates construction timeframes of 30 to 36 months from breaking ground at a site to power generation. Additional modules can then be added as needed. NuScale projects that the first plant can go into operation from 2015 to 2016.

What is the projection for NuScale operating efficiency in terms of capacity factor – the percent of time over the course of a year that a plant operates at full power?

NuScale plants are expected to operate at capacity factors in excess of 90 percent, producing full power about 330 days or more per year.

How often will each module need refueling?

Under the current design, a NuScale module will need refueling every 24 months.

What will happen to the used fuel after refueling?

NuScale expects plant owners will follow the same protocol as current operating nuclear power plants. Once removed from the reactor, after creating the heat that ultimately produces electricity, the used or spent fuel will be stored on site and allowed to cool further in a water filled pool. If an additional period of on-site storage is needed, the spent fuel can be stored safely in specially designed casks.

What type of approval does NuScale need for its design?

The U.S. Nuclear Regulatory Commission must provide Design Certification for any new nuclear plants like those being designed by NuScale. Two factors benefit NuScale in this process. First, its design is based on existing light water reactor technology and the NRC already has extensive knowledge and experience with this established technology. Second, NuScale already has a one-third scale test facility in place at Oregon State University and can run or verify its tests and models there.

NuScale had the first of four pre-application review meetings with the NRC in July 2008. NuScale plans to submit its full application for Design Certification in 2010. The Design Certification proceeding is expected to take 24 to 36 months after the application has been submitted.