Duane Arnold officials closely monitoring events in Japan

The majority owner of the Duane Arnold Energy Center is closely monitoring events unfolding at Tokyo Electric's massive Fukushima Daiichi nuclear power plant, which uses a similar reactor design.

Both the Fukushima Daiichi nuclear power plant and NextEra Energy's Duane Arnold Energy Center use GE-made boiling water reactors. They use heat from nuclear reactors to boil water, creating steam to turn a turbine that generates electricity.

NextEra Energy offered reassurances about the safety margin at the company's plants, but did not comment specifically on the Duane Arnold Energy Center in Palo.

All of the plants owned by NextEra are outside of known “high hazard” earthquake zones, the company said, and each plant has been specially designed to withstand natural events such as earthquakes, storm surges and flooding without losing capability to perform their safety functions.

“In fact, our designs and ongoing maintenance programs are specifically based on a number of factors including the likely worst-case seismic scenario for the location of the plant,” the statement said.

Duane Arnold Energy Center spokeswoman said it is difficult for NextEra to draw conclusions from the events at the Fukushima Daiichi nuclear power plant because the situation is still unfolding.

The Fukushima Daiichi plant's failure began after an extremely powerful earthquake Friday. The reactors shut down automatically, but power to the plant was cut off, preventing the cooling system from removing the “decay heat” that continues for a period of time after a reactor shutdown. Backup diesel generators failed due to the effects of the tsunami caused by the earthquake, and government officials evacuated the area after declaring a nuclear emergency.

Six Tokyo Electric workers were injured Monday in a hydrogen explosion at Unit 3 of the Fukushima Daiichi plant, the second hydrogen explosion at one of the plant's six  boiling water reactors.

Japan's energy secretary has said the plant's essential containment structures have survived the explosions, helping to minimize the release of radioactivity into the surrounding atmosphere. Much remains unknown, however, about the amount of releases and conditions inside the plant.

The Duane Arnold Energy Center uses a single GE BWR-4 boiling water reactor, and is not in a high-risk seismic zone. The 620-megawatt plant is one of the smaller nuclear power plants in the United States. It has been in operation since 1974, and recently received a 20-year extension of its original 40-year operating license, to the year 2034.