In a move that could signal trouble ahead for the anti-nuke crowd, uranium prices have posted remarkable strength in the past several weeks, trading close to $40 per pound in the spot market. That's up sharply from lows of $28 last summer. More importantly, it reverses a grinding three-year decline that seemed to signal the end of the nuclear era following the horrible 2011 disaster at Fukushima, Japan.

Is this just a typical bear market rally that will peter out? Or is the recent strength in uranium a sign of a new nuclear era ahead that will drive uranium prices and mining stocks even higher?

It's probably the latter. That will disappoint opponents of nuclear energy, but if you are an investor with a Warren Buffett-like timeframe of at least five years, it means it's time to buy the uranium miners that will benefit from some big trends creating a looming supply-demand imbalance that could make the controversial metal double from here over the next four years.

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Be warned, though: A lot of smart people think forecasts of a bull market in uranium are just bull, and we'll get to the bear case in a second. But global population growth will be so big over the next two decades, electricity is such a nice convenience and alternative sources of energy are either so dirty (coal) or inconsistent (wind and solar) that it seems a fair bet that nuclear power will play a much bigger role.

"Uranium offers a rare growth opportunity in metals and mining," says Morningstar analyst David Wang, who recently penned a bullish report on the metal. The global reactor fleet should grow 37 percent by 2025, which will drive 40 percent growth in uranium demand over the same time frame, predicts Wang.

Because power plants buy several years’ worth of supply in advance, uranium prices could start to move significantly higher as soon as 2017. He thinks the spot price of uranium could hit $75 a pound in 2019 in real terms (adjusted for inflation), for a 100 percent-plus gain from recent levels of $36. "We expect new reactor capacity to drive the strongest uranium demand growth in decades," he says.

If so, this will take a lot of analysts by surprise, because they are too focused on the current glut of uranium.

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Let's take a closer look at the trends that may catch them off guard.

A Global Population Boom

The United Nations predicts world population will grow to 8.7 billion by 2035 from about 7.3 billion now. Those newcomers are going to want electricity. The growth of the middle class in developing countries will compound the demand growth. The bottom line: There may be 81 percent demand growth for electricity by 2035 from 2011, according to the Organization for Economic Cooperation and Development.

That's big. So big that a lot of this electricity may have to come from nuclear generation. As good as renewable sources of energy are for the environment, they are intermittent because they depend on sunshine or wind. They can't yet provide the massive amount of daily electricity, known as base load, the way nuclear energy or coal can. Elon Musk at Tesla Motors (TSLA) and others are working hard to develop next-generation batteries that will store enough energy to help make intermittent renewable energy sources more viable. But so far, no cigar. And the problem with coal-fired power plants is that they create too much pollution — as China well knows.

That leaves nuclear power.

China Going Nuclear

China's coal-related pollution problem has gotten so bad, for example, the country is turning to nuclear power in a big way. The number of nuclear reactors there will grow from 23 to 86 over the next decade, predicts Wang. Its annual uranium demand will grow 167 percent, to 16,800 tons from 6,296 tons.

China is not alone. South Korea, India and Russia are also going to be backing away from coal and adding nuclear power in a big way to meet demand. Together, these three countries will increase their nuclear generating capacity by 54 percent over the next 10 years. Their annual demand for uranium will rise to 17,580 tons from 11,390 tons last year, says Wang.

The United Arab Emirates, Turkey, Belarus, Saudi Arabia, Vietnam, Bangladesh, Poland and Jordan also plan to add plants. The U.S., currently the biggest world producer, with 100 reactors as of last summer, has five plants under construction.

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