One of the scariest sentences emanating from news coverage of Japan’s horrific natural disaster is packed with uncertainty.

"It was not immediately clear how much — if any — radiation had been released," wrote the Associated Press after Sunday’s hydrogen explosion at a nuclear plant, the second in three days.

As Japan digs itself out from the devastation of an earthquake and tsunami, it is balanced on the precipice of the worst nuclear disaster since the meltdown of the Chernobyl nuclear plant in 1986.

The circumstances are far different in Japan than they were then in the Ukrainian Soviet Socialist Republic. Japan’s nuclear plants are better constructed, and even a total meltdown probably would be mostly contained in steel and concrete tombs, averting massive radiation clouds.

But even as we hope for survivors and try to determine the extent of the meltdown, there is no doubting the impact the disaster will have on the future of nuclear power in our country and, indeed, in Missouri.

Opponents of nuclear power have seized the tragedy and are using it as ammunition against various proposals to construct new reactors in the United States. As Japan’s tragedy grows, their argument will gain momentum, as supporters of Ameren Missouri’s plans to build a second reactor in Callaway County surely have surmised.

Make no mistake: the Callaway plant is a world away, literally and figuratively, from the Fukushima Daiichi plant suffering through explosions and partial, if not total, meltdown. The New Madrid fault, for instance, is nowhere near as active a seismic zone as the volcano-ringed Pacific rim. It was the tsunami, not the earthquake, that knocked out the power to the Japanese plants.

Still, there’s no denying the uncertainty raised by questions of a massive nuclear plant failure. Mark Cooper, a senior fellow for economic analysis with the Institute for Energy and the Environment, said the one thing that is certain — and applicable to Missouri’s nuclear debate — is that costs for nuclear energy will continue to skyrocket.

"Whatever you thought the cost was going to be in Missouri, it’s going to be higher," Mr. Cooper told us.

Why? Because Wall Street is risk averse. That’s why, in 2009, Ameren Missouri asked the Missouri Legislature to change state law so that it could pass on to consumers the costs of building a second nuclear plant at Callaway. The Legislature demurred, but Ameren is back this year with a request for help with permitting costs.

The reason: Utilities can’t get Wall Street to finance the multi-billion-dollar plants because the risks and rising costs are unpalatable.

And, because of Japan, Mr. Cooper said, Wall Street and Washington regulators now will make the process even more expensive. He calls that sort of market-based approach "behaving responsibly."

Indeed, allowing the marketplace to work is the fundamental debate in Jefferson City over Ameren Missouri’s proposal. It’s not about whether lawmakers support or oppose nuclear energy. Most of them are squarely in favor of nuclear as one of the state’s future energy options, as are we.

The question is how Missouri pays for its energy future and whether consumers big and small take on an unfair amount of the risk. That risk, like it or not, just grew exponentially.

The market reaction to Japan’s cataclysmic event is sure to be cautious. Missouri lawmakers should adopt the same approach.