A Q&A from my company regarding the Japan nuclear incident:
What happened in Japan?
After the earthquake, all the operating reactors at the ***ushima Daiichi and ***ushima Daini nuclear plants shut down automatically, as they are designed to do. However, due to the loss of off-site power and failure of the backup diesel generators due to the tsunami, there were difficulties powering the waste heat cooling systems at the ***ushima Daiichi plant.
What steps did the operators of the plants in Japan take to mitigate the problem?
Residents were evacuated from a 12.5-mile radius around the Daiichi plant and about two miles around the Daini plant. Other precautionary measures taken to evacuate residents near the sites were intended to prevent or mitigate any radiation dose from radiation releases that might occur as the situation develops.
To reduce the resulting increase in containment pressure, Tokyo Electric Power Co., vented steam—containing small amounts of radioactive material—from the primary cooling circuit of Units 1 and 3. The released vapor passed through filters designed to remove radioactive components such as iodine and cesium. Upon release, the slightly radioactive vapor dispersed into the atmosphere. A buildup of hydrogen gas in the secondary containment structure at Daiichi Unit 1 and Unit 3 led to explosions at that plant. However, the integrity of the primary containment structure was not compromised and there were no large leaks of radiation from the reactor core.
When the immediacy of the situation in Japan is behind them, Americans will still find that a diverse mix of energy including nuclear will be needed in order to meet the needs of this country.
Fuel rods in the reactor vessel of Unit 2 at the ***ushima Daiichi Power Plant were temporarily uncovered from cooling water Monday, March 14, but seawater injection has raised the water level to the halfway point. Seawater is now being used to cool all three Daiichi reactors that were shut down after the March 11 earthquake.
How is the U.S. nuclear industry helping in Japan?
The U.S. Nuclear Regulatory Commission has sent 11 experts to Tokyo to provide assistance requested by the Japanese government.
Could this type of incident happen in the U.S.?
While there are risks associated with operating nuclear plants and other industrial facilities, the chance of an event similar to what happened in Japan occurring in the U.S. is very low:
* An 8.9 earthquake combined with a tsunami striking one region is very rare, even in the high seismic activity region that includes Japan
* Japan’s earthquake last Friday was the fifth largest recorded in history
Since Sept. 11, 2001, additional safeguards and training have been put in place at U.S. nuclear reactors that allow plant operators to cool the reactor core during an extended power outage or failure of backup generators, sometimes referred to as “blackout conditions.”
How will this event affect the future of nuclear energy in the U.S.?
The events in Japan are still unfolding; however, when the immediacy of the situation in Japan is behind them, Americans will still find that a diverse mix of energy including nuclear will be needed in order to meet the needs of this country:
* Meeting growing demand for electricity with non-emitting generation sources.
* Fueling economic growth with reliable and affordable electricity.
* Securing energy independence from foreign nations.
I’ve heard so many references on the news to Three Mile Island and Chernobyl. Exactly what happened in those incidents?
On March 28, 1979, a combination of equipment failure, inadequately designed instrumentation and the inability of plant operators to understand the reactor’s condition culminated in an accident at Three Mile Island Unit 2 in Pennsylvania. The fuel was heavily damaged, but the plant’s design features worked, and there were no adverse impacts on public health and safety. Although a small amount of radiation was released, no deaths, injuries or direct health effects were caused, according to over a dozen independent studies. However, Unit 2 of the plant was shut down permanently.
On April 26, 1986, an accident occurred at Unit 4 of the nuclear power station at Chernobyl, Ukraine, in the former Soviet Union. The accident, caused by a sudden surge of power, destroyed the reactor and released massive amounts of radioactive material into the environment. The Chernobyl reactors are of the RBMK type: high-power, pressure-tube reactors, moderated with graphite and cooled with water. At the time of the Chernobyl accident there were 17 RBMKs in operation in the Soviet Union and two in Lithuania.
Pripyat, the town near Chernobyl where most of the workers at the plant lived before the 1986 accident, was evacuated several days after the accident, because of radiological contamination. It was included in the 30-km Exclusion Zone around the plant and is closed to all but those with authorized access.
What lessons were learned from Three Mile Island?
Lessons from TMI-2 transformed the nuclear industry into one of the safest in the nation.
* Improved equipment provides operators better tools to identify and correct equipment and operational problems.
* Improved training enables operators and engineers to prevent and address equipment issues before they become a potential safety concern.
* Simulator training enables the industry to train and test operators in emergency situations using real-life examples such as TMI-2.
* The industry formed emergency plans at nuclear power plants and improved communications with off-site local, state and federal responders.
TMI-1, which remained in operation, is now one of the best performing plants in the country – recently completing a world record-breaking 688 days of continuous operation for a pressurized water reactor.
What lessons were learned from Chernobyl?
According to the NRC, U.S. reactors have different designs and controls to protect them against the combination of lapses that led to the accident at Chernobyl. Although the NRC has always acknowledged the possibility of major accidents, its regulatory requirements provide adequate protection, subject to continuing vigilance, including review of new information that may suggest weaknesses.
An April 1989 report and other NRC analysis since then has concluded that no changes were needed in the NRC's regulations regarding the design or operation of U.S. commercial nuclear reactors directly as a result of Chernobyl. The NRC recognizes that the Chernobyl experience should remain a valuable part of the information to be taken into account when dealing with reactor safety issues in the future.
