**At the end of World War II, American planes dropped two atomic bombs on the Japanese cities of Hiroshima and Nagasaki, killing and maiming hundreds of thousands.

Six years later, four light bulbs in Idaho lit up. Their illumination was fueled by an experimental “breeder” reactor based on the infamous wartime technology used in Japan.

As the world’s first generation of electricity from nuclear power, it was the beginning of an era that still persists. Fast-forward to 2013: Today, about a third of the world’s energy needs are supplied by nuclear power plants.

What are the advantages and disadvantages of fission-based power? To answer this question, we’ll explore key nuclear energy pros and cons in the areas of reliability, efficiency, cost-effectiveness, and the environment.

Reliability

One of the biggest benefits of nuclear fission is its ability to supply base load energy to the electric grid. This is something any reliable source needs to be able to do. Currently, the dominant implement for the job is overwhelmingly coal, a fossil fuel with significant negative effects on the environment.

Nuclear power is considered reliable because it does not suffer from intermittence, or periodic ups and downs. Once set in motion, it runs 24/7, year-round. This characteristic makes it reliable enough to compete with coal on the grid, an achievement still eluding renewables like wind and solar. As a result, nuclear energy has come to supply about 20% of the electrical needs in the United States, and more globally.

Efficiency

Is efficiency one of the pros of nuclear power? Yes! While nuclear fusion would be the ultimate efficiency attainment, today’s fission-based power is already a very high-density source of energy relative to fossil fuels.

You can get about 8,000 times as much energy from a gram of uranium versus comparable amounts of oil or gas, according to figures published by the Institute of Physics.

Costs

Is nuclear power cost-effective? No; and yes—it depends on how you measure it. The economics of nuclear plants can be mind-boggling, but there are some definite trends to note. For example, the startup costs for a new facility and its continuous maintenance are steep, and usually require government subsidy.

Once established, nuclear-fired electricity is cheap, measured in kilowatts for the money. But then it produces radioactive nuclear waste, which turns out to be one of the most difficult materials in the world to store. Radioactive waste disposal is one of the costliest elements of nuclear power.

Environment

One of the most contested points, both nuclear advocates and opponents have strong opinions about the green merits of nuclear energy. From one perspective, nuclear offers a way out of coal's major role in electricity production. Nuclear-electric generation doesn't create climate-changing greenhouse gases, only steam.

Opponents counter that, although fission is carbon-free, other parts of the nuclear life cycle aren’t, such as uranium mining and transport. Further, nuclear energy is not renewable; it depends on a rare and finite supply of radioactive heavy metals that must be mined from deep underground, much like coal, oil and natural gas.

Of course, in the event of a nuclear meltdown or similar crisis, the emissions of biohazardous radiation can be enormous. It has been two years since the largest such catastrophe in a quarter of a century, at the Fukushima/Daiichi nuclear complex in northern Japan. The biosocial fallout from this incident continues today for thousands of “nuclear refugees.”

Much of the debate centers on what is considered a “safe” dose of radiation. Government and industry officials recognize safe levels of radiation, but these benchmarks are often based on political influences rather than hard science.

According to Dr. Helen Caldicott, Nobel Prize winner and founder of the non-profit Physicians for Social Responsibility, “there is no safe dose of radiation. The effects are cumulative.”

A long-time opponent of nuclear technology, Dr. Caldicott says that all exposure increases the likelihood of getting cancer.

Is nuclear power more environmentally-friendly than fossil fuels? In terms of direct emissions, yes. With regard to other possible impacts, however, the ecological benefits of nuclear energy are unclear at best and catastrophic at worst.

Nuclear energy could help us get off of coal-fired utilities and prevent global warming. But in the long run, it poses a significant environmental threat via externalizations that are difficult to contain.

Part of the Solution?"

Nuclear power is a hell of a way to boil water." These were the words of the founder of modern physics and atomic pioneer, Albert Einstein. It’s an ironic statement to have made amid fierce debates over the pros and cons of nuclear power.

The uniquely compelling advantages and disadvantages of this form of energy have made it perennially controversial, from its militant inception to the dramatic post-tsunami meltdowns in northern Japan early in 2011.

Is nuclear a part of the solution to environmental degradation? As a non-renewable resource associated with periodic, large-scale disasters, nuclear isn’t the best option for the environment or public health; as a relatively clean, efficient and reliable method, neither is it the worst.