What's Next for Nuclear?
Topics: Energy, Engineering, Physics, Television, Video
Science Education Collections: Energy, HS Physics
- Download HD (H.264)
- Copy and Paste to Embed
Despite the accident last year at a nuclear plant in Fukushima, Japan, here in the United States, some policymakers – including President Obama – are pushing to expand nuclear energy as a source of abundant carbon-free electricity.
“To meet our growing energy needs and prevent the worst consequences of climate change, we’ll need to increase our supply of nuclear power. It’s that simple,” said Obama in Feb. 2010, during a press conference at a Maryland nuclear plant.
Work has started on four new multi-billion dollar reactors in Georgia and South Carolina, the first to begin construction in the United States in more than 30 years. But observers disagree over exactly what this means.
“Today, we don’t know if there is a nuclear renaissance,” said Per Peterson, chair of the University of California, Berkeley’s Department of Nuclear Engineering. “That will depend on whether these new plants that are under construction now can be built on schedule, on budget, at a reasonable cost.”
Overall, nuclear energy provides 20 percent of U.S. electricity – far more than all solar, wind and other renewable sources combined. And a recent EPA study shows that in order for the country to reduce its carbon emissions enough to slow down climate change, it will need to boost its nuclear energy production.
But skeptics argue that the country doesn’t need nuclear energy to meet its goals.
“The notion that nuclear is the only option we have to reduce our greenhouse gas emissions is preposterous,” said Ralph Cavanagh, co-director of the energy program at the Natural Resources Defense Council, in San Francisco.
Cavanagh said that cost and risk have pushed utilities around the country away from nuclear energy and towards other renewable energy sources, energy efficiency and natural gas.
California has two nuclear plants, the Diablo Canyon Power Plant, near San Luis Obispo, and the San Onofre plant, near San Diego, which has been closed since Jan. 2012, after problems were found with some of the tubes that carry steam.
Prospects for the development of new nuclear plants in the state stalled long ago. The Rancho Seco nuclear plant, in Sacramento, was closed in 1989 after a public vote. And California still has in place a 1976 moratorium on building any new nuclear plants until the federal government creates a permanent site to dispose of nuclear waste.
In California and the rest of the country, nuclear accidents from the past continue to cast a shadow on the technology. The worst one to date happened with a devastating explosion and fire at the Chernobyl plant in Ukraine in 1986, which released radiation across Europe.
Twenty-eight rescue workers died from radiation exposure. Other health effects started to show up a few years later.
“The primary finding so far is an increased risk of thyroid cancer and other thyroid diseases in those who were children and adolescents at the time of the accident,” said Dr. Lydia Zablotska, an epidemiologist at the University of California, San Francisco.
The radiation increased the risk of leukemia among the 600,000 workers who cleaned up after the accident.
Researchers predict that the Chernobyl accident will cause 4,000 to 6,000 cases of thyroid cancer and 3,000 to 4,000 cases of leukemia. Fourteen deaths from thyroid cancer have been documented so far. And scientists are still following the population for other health effects that might appear later.
Proponents of nuclear energy say that the risks of an accident should be weighed against the health effects from burning fossil fuels. The American Lung Association estimates 13,000 people die in the United States each year from breathing soot particles from coal-fired power plants.
“The public health and environmental consequences of using fossil fuels are so enormous that they dwarf even the consequences of nuclear accidents,” said Per Peterson. “That said, we need to be moving towards new nuclear energy technologies that do not have the potential to release radioactive materials into the environment.”
Per Peterson and his students at UC Berkeley's Department of Nuclear Engineering are working on a new type of nuclear reactor they say would be safer and cheaper than those operating today.
Today’s nuclear reactors are cooled by water, which can cause problems if a plant loses power. The explosions at the nuclear plant in Fukushima, Japan, following an earthquake and tsunami on March 11, 2011, were brought on by a chemical reaction between water and the metal that protects the uranium fuel.
“At Fukushima, water reacted with the metal cladding of the fuel to release hydrogen, which ultimately caused explosions,” said Peterson.
And the water inside a nuclear plant can be problematic in other ways too.
“The water pressure built up inside the containment to very high pressures, causing leakage and requiring venting, which released radioactive materials,” said Peterson.
Whether it’s fueled by coal, natural gas or nuclear reaction, the goal at any power plant is to produce heat and turn water into steam. During a May visit to Pacific Gas and Electric’s Diablo Canyon Power Plant, Peterson stood on a hill above the plant’s two dome-shaped structures.
“Below us are the two reactor containment buildings that contain the nuclear reactors that are producing heat and boiling water,” he said. “The steam is going into that large turbine building behind and turning the turbines that turn generators and make the electricity that is going out over our heads into the center of California.”
In the mid-1980s, Diablo Canyon’s two reactors were the last to go into operation in California. Today, they produce 16 percent of Northern California’s electricity, enough to power about 2 million homes.
Nuclear reactions are an efficient way to produce heat. In a nuclear reaction, a particle called a neutron hits the nucleus of a uranium atom. The reaction – known as fission — breaks the nucleus in two and releases heat, as well as more neutrons that go on to create a chain reaction of nucleus-splitting.
Peterson aims to make nuclear plants safer by cooling the reactor’s core – where the nuclear reaction takes place – with a liquid other than water.
“The fluoride salts that we’re developing as coolants boil at extremely high temperatures – above 1,400 degrees centigrade – which means that under the conditions we operate at, they’re always at low pressure,” he said.
To further reduce risk, Peterson proposes storing the fuel inside graphite pebbles, which wouldn’t melt down in an accident.
The pebbles would also offer another advantage over today’s reactors, said Peterson. In a room at the nuclear engineering department, his students have built a model of the pebble-bed reactor they’re testing. They use colored plastic balls slightly smaller than golf balls in place of the graphite fuel pebbles. And for research purposes, they’ve replaced the fluoride salts with water, which is easier to work with.
The yellow, green and gray plastic balls move through a narrow plastic tank, mimicking the way in which graphite pebbles full of fuel might one day float through liquid fluoride salts in a real pebble-bed reactor. The moving pebbles would be an improvement over current reactors, which have to be closed down every 18 months to bring in fresh uranium rods, said Peterson.
“It takes about 30 days for a pebble to go through the core, before it’s removed, inspected, and possibly reinserted,” he said. “That means you’re continuously replacing the fuel and you don’t need to shut down for refueling outages.”
Peterson’s pebble-bed reactor could be in operation in 20 years, he said.Tags: Chernobyl, Diablo Canyon Power Plant, Lydia Zablotska, nuclear energy, Per Peterson, radiation, thyroid cancer