The earthquake and tsunami in Japan the disaster they caused at a nuclear power plant there are raising questions about the safety of Minnesota's two nuclear power plants.
Xcel Energy's Monticello plant, built in 1970, and the dual-reactor Prairie Island plant, built in 1974, both sit next to the Mississippi River. Together they produce one-quarter of the electricity Xcel's customers use.
Q: Are Minnesota's plants similar to the one having problems in Japan?
Xcel's plant at Monticello is similar in design to the Japanese plant: it's a GE boiling water reactor, and there have been safety concerns about this design for years.
Experts say a build-up of pressure in the core could destroy the containment vessel. American plants have made modifications over the years that allow venting to prevent pressure from building up -- but that could presumably allow radioactive material to escape, as it apparently has been doing in Japan.
The plant at Prairie Island is a pressurized water reactor, designed with a more robust containment vessel.
It's worth remembering that all nuclear plants operate basically the same way: the nuclear reaction heats water to drive a turbine that generates electricity.
Q: What is the safety record at Minnesota's plants?
The Prairie Island plant had what the Nuclear Regulatory Commission (NRC) calls "cross-cutting issues," meaning a pattern of human errors and other problems that indicated a problem with safety awareness. After about a year of extra inspections and a lot of hard work, Prairie Island was returned to standard status late in 2010.
The Monticello plant doesn't have a similar history of problems.
Q: The situation in Japan sounds like the worst possible combination of natural events. How would plants in Minnesota respond to similar challenges?
We do have earthquakes, but they're small ones. (Interestingly, the geologic stability in Minnesota is a factor that caused the federal government to put Minnesota on a short list of possible locations for long-term storage, years ago.) We have tornadoes and floods. Xcel Energy and the NRC say Minnesota plants are designed to withstand these natural events.
Xcel says both plants are well above the "1,000-year" flood level. Xcel pays attention to flood warnings, and follows a protocol of preparations. Xcel says it would shut down a plant before the river rose to the point of affecting equipment needed for plant operations.
As did the plant in Japan, Minnesota's plant has redundant backup systems. To keep the reactor core cool, two sets of back-up diesel generators and a set of batteries could operate pumps; if those lines of defense failed Xcel has portable pumps to bring water from the Mississippi River.
The NRC requires the batteries to be capable of lasting four hours. This is based on the reliability of the Minnesota electrical grid, the number of electric lines coming into the plant, and the safety record of the diesel generators.
Plant operators train in a simulator control room every six weeks. It has them run through computer-generated scenarios to mimic many possible events.
For neighbors, Xcel publishes an 18-page guidebook on nuclear safety issues and evacuation procedures. The company trains regularly with local law enforcement and emergency officials.
The Prairie Island Indian Community is located only about a block from the Prairie Island plant. The Community has complained for years about feeling left out of the loop; officials say they're not adequately informed about plant operations and problems.
On Tuesday, the Tribal council issued a statement expressing concern for the Japanese people dealing with natural and nuclear disasters. "Their reality is our biggest fear," the statement says. "The tragic events in Japan demonstrate that even the most stringent and redundant safety measures cannot guarantee our safety and security."
Q: How will this event affect the debate on removing Minnesota's moratorium on new nuclear plants.
Backers of the bill to eliminate the moratorium say it shouldn't make a difference: they say dropping the ban doesn't mean anyone would build a plant immediately. Currently the matter is in conference committee, and legislators are talking with Gov. Mark Dayton's staff. His concerns about the lack of options for long-term storage and the huge cost over-runs and delays in plant construction elsewhere have not been addressed in the legislation.
Q: Where do the Minnesota plants stand on renewal and expansion?
Monticello recently received a license extension for 20 years, and has applied to the NRC for an "uprate," an expansion of electricity production.
Prairie Island has state approvals for a license extension, increased on-site storage of nuclear waste, and an uprate. NRC approvals are pending. Xcel ways it will invest more than a billion dollars to prepare Prairie Island to operate for another 20 years.
Q: Is Xcel doing anything different as a result of Japan experience?
It's too early to tell, but Xcel and others in the industry do expect to learn from this event. The government and others will conduct an exhaustive analysis, to see how the industry can apply lessons to plants in the United States.