MN Nukes Undergo Upgrades

Tuesday, March 6, 2012 @ 04:03 PM gHale

The owner of Minnesota’s two nuclear power plants is ready to spend $20 million to $50 million on safety upgrades and studies based on the lessons of the nuclear catastrophe in Japan.

Xcel Energy is buying more diesel pumps and portable generators that could quickly deploy at its Monticello and Prairie Island plants if all backup electricity went out, as it did at Japan’s Fukushima Dai-ichi plant.

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The U.S. nuclear industry said these and other actions over several years will enhance the safety of the nation’s 104 reactors at relatively modest cost. The U.S. Nuclear Regulatory Commission (NRC) last week approved the first post-Fukushima measures, and plant owners likely will receive specific orders this week, just days before the March 11 anniversary of the disaster.

Regulatory Commission Chairman Gregory Jaczko, who was among the four commissioners to approve the Fukushima-related orders last week, expressed concern about delays, especially for plants needing study of earthquake risks. “I simply cannot accept a timeline that puts this issue well into the later part of the decade,” he wrote.

Xcel’s two nuclear plants are the two-unit Prairie Island station near Red Wing, 50 miles southeast of the Twin Cities, and the one-unit plant at Monticello, 40 miles to the northwest. Monticello has a General Electric Mark 1 boiling water reactor like those damaged in Japan.

Xcel’s safety costs could climb as high as $250 million if the utility had to purchase nuclear-qualified equipment and take other costly steps such as building earthquake-proof off-site buildings to store and protect it, said Dennis Koehl, chief nuclear officer for the Minneapolis-based utility.

The Nuclear Energy Institute (NEI), which represents the industry, has directed members to order portable response equipment this month. Xcel has already acquired five additional pumps, adding to the two it purchased after 9/11.

Under the industry’s “flexible coping strategy” for a disaster, big-ticket items like filtration systems for radioactive water will be purchased by all plant owners and stored at one or more U.S. locations — ready to be flown to a stricken plant.

Three of six Fukushima units were running when a record earthquake struck last March. The subsequent tsunami wiped out power lines and in-plant diesel backup generators, leaving about eight hours of battery life to control the plant.

Operators couldn’t cool the reactors, resulting in damage to nuclear fuel and reactor cores, according to the NRC’s account. At three units, hydrogen produced during the crisis exploded, damaging upper walls and roofs, exposing pools of spent fuel rods and releasing high levels of radioactivity.

It took the rest of the year for plant owner Tokyo Electric Power Co. to bring the damaged units into a state called cold shutdown.

One of the lessons the U.S. industry and its critics don’t dispute is that nuclear power plants need more battery time to cope with a complete loss of power. That’s something the NEI said happened only once in the United States, at a Georgia reactor in 1990 and without disaster.

At many U.S. plants, including Monticello and Prairie Island, key batteries rate for just four hours. Plant owners now will need to extend that coping time, though the NRC hasn’t said how or for how long, leaving plants to propose solutions to regulators.

At Prairie Island, for example, that may mean switching emergency lighting to other batteries that aren’t critical to plant control, Xcel officials said.

Industry officials argue that many nuclear power plants, including Monticello, have multiple transmission lines connecting them to the grid, which lowers the risk of losing power. On the other hand, multiple-unit plants like Prairie Island have long counted on getting help during a disaster from an adjacent unit — an assumption that proved wrong in Japan.

U.S. regulators, in the first of three phases of their post-Fukushima response, will order plant owners to restudy earthquake and flood risks, improve emergency response and begin other safety-related improvements. Even in Minnesota, seismic studies will be a requirement, along with a fresh look at worst-case flood risks such as multiple dam failures.

Two other lessons from Japan are getting special attention. U.S. regulators want existing hydrogen vents on boiling-water reactors to be reliable during a crisis, which may require design changes. They also want more gauges to monitor pools holding spent fuel, which ended up exposed in the Japan disaster. Those fixes may not be in place for four years or more.

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