I feel as though I'm writing amid history and portent. It's been precisely one year since the tragic explosion of the Transocean (NYSE: RIG) Deepwater Horizon drilling rig in the Gulf of Mexico and the start of the months-long cataclysm that followed. And we're also just over a month beyond the tragic 8.9 magnitude earthquake, tsunami, and nuclear catastrophe that rocked northern Japan and petrified the world.

Largely as a result, I'm hard-pressed to execute the mental gymnastics necessary to identify a time when our approach to energy reached today's levels of confusion and contentiousness. Such circumstances would be of far less moment without the impact that energy exerts on our economic vitality and national security. But unfortunately, we can't easily escape those relationships.

Last year's disaster was one occurrence for an industry that has drilled 14,000 domestic deepwater wells without significant incident. Nevertheless, it likely will serve as a justification for riding our national brakes regarding the regeneration of active drilling programs in the Gulf. As to the onshore world, where advancing technology has created new opportunities and economics with lightning speed, I find it difficult to confidently wager that we can avoid a game of "chicken" between generally legitimate environmental concerns and the expansion of that still-emerging technology.

Unraveling nuclear
 Long-controversial nuclear is even more confounding. Perhaps I'm driven to that conclusion since I live a stone's throw from the next U.S. reactor to be fired up (in 2012) at Tennessee Valley Authority's Watts Bar unit. But no, the picture's far bigger than that. Following the March 11 cataclysm at Tokyo Electric Power's Fukushima Dai-Ichi plant, nation after nation -- from Germany to Switzerland to India and on to China -- has stepped up to declare a reconsideration of its nuclear future.

Obviously, a key result has been the passage of similar concerns about nuclear energy onto the likes of General Electric (NYSE: GE) and Siemens (NYSE: SI), both of which cast a shadow on the sophisticated world of producing the reactors and other equipment that make up nuclear facilities. Further down the chain, on the uranium end, companies such as Canada's Cameco (NYSE: CCJ) and Uranium Energy (AMEX: UEC) are now at well below mid-March levels. Obviously then, the question becomes one of the tense -- past or future -- that should be tied to nuclear as an investment opportunity.

My approach in drawing opinions about the group calls for an especially careful, bottoms-up approach, an exercise from which opportunities are presented or withdrawn. With Siemens, for instance, nuclear has been on somewhat shaky ground since before the earthquake. On the one hand, the company appears perplexed about the partner with which it ultimately wishes to dance. A number of years ago, it formed a venture with France's Areva, SA. But that deal appears to have been sold and wound down in favor of a spin around the floor with Rosatom, Russia's state-owned atomic energy company. However, that deal also is no slam-dunk. 

Angela's ashes
Furthermore, Chancellor Angela Merkel is clearly unenthusiastic about nuclear for Germany -- where Siemens has played a big role in the lion's share of the nuclear plants. And the company's CEO, Peter Loscher, has also glommed onto the "green" movement, featuring the usual list of (still uneconomic) wind and solar suspects. As such, I'd treat Siemans as "nuclear agnostic," neither buying its potential in the area, nor avoiding it for the same reason.

The vibes at General Electric remain more positive for nuclear, but it still shouldn't be considered a deal maker or breaker. The Fukushima plant was the product of a GE reactor design. That includes the No. 1 unit that, with a 1971 start-up, predates many Fools' arrivals. Nevertheless, the company and its partner Hitachi (NYSE: HIT) are active in a nuclear safety movement that will have Southern Co. (NYSE: SO), the biggest of the publicly held utilities, hoping for construction and operating licenses for a new safety design by the Westinghouse unit of Toshiba by the end of 2011.

When looking at GE relative to its nuclear business, however, an even bigger factor should be its role in the growth of its broadly based energy unit. It also covers renewable "green" initiatives, along with a more conventional gas-fired turbine business and a top-notch producer of VetcoGray subsea wellhead systems. In the process, the unit generates revenues of about $37.5 billion, of which nuclear remains a small part. So without slipping into a pattern, I'd add GE, whose shares are about flat with their March 11 level, to the "buy or reject it for other reasons than nuclear" category.

Reacting to the cake mix
Which brings us to the uranium-related types, including Cameco and Uranium Energy. It shouldn't be surprising if this phase of business doesn't give you more pause than do the bigger, more insulated types. Nevertheless, it's well to remember the critical mass of the U.S. nuclear business alone. Indeed, about 20% of our nation's electricity is generated from 104 operating nuclear reactors. And since you can't burn, say, cake mix in those reactors, the demand for uranium isn't about to disappear. And with the two named uranium companies trading at least 20% below their March 11 perches, can the conclusion be other than an opportunity?

So there you have it -- at least as much as anyone can wrap their arms around nuclear's complexity six weeks beyond Japan's tragedy and the world's subsequent skittishness. To track the changes that will inevitably continue in the industry, I'd recommend adding as many of the above names as possible to Foolish watchlists.