Japan relaunched its nuclear program on Tuesday after a two-year hiatus. The government is eager to tap into the much-needed energy source, but a majority of Japan's citizens are against the move.

The decision to meet nation's energy needs with nuclear power is not only controversial in Japan. Nuclear developments meet resistance around the world due to the technology's track record.

Nuclear meltdowns are responsible for disasters such as Chernobyl in 1986 and Fukushima in 2011. The science is feared for its military capacities.

Despite the risks associated with nuclear energy, it has the lowest emissions of any electricity generator, apart from wind energy, according to a 2014 report from the Intergovernmental Panel on Climate Change.

What is nuclear energy?

Most nuclear power is created by the energy released during the continuous splitting – or fission – of atoms. The energy released from this process is harnessed as heat, in either gas or water. This heat produces steam to power the turbines that produce electricity.

Nuclear energy is also widely used in military technology, not only in bombs.

“There are nuclear reactors in submarines, aircraft carriers and ice breakers,” R. Andreas Kraemer, the Founder and Director Emeritus of Ecologic Institute, told DW.

This energy becomes the conventional electricity source that provided 10.8 percent of the world's power needs in 2014, according to the World Nuclear Industry Status Report in 2015.

Why is it controversial?

Nuclear power is mired in controversy because of its military uses. According to Kraemer, mass demonstrations against atomic energy date back to the 1950s.

“It is the contentious nature of the technology and its association with war and death,” he told DW. “It has never really escaped from that shadow, basically because it couldn't live up to the promises that it was sold by in the 1950s.”

There is also the concern of nuclear waste disposal, created when the reactor's fuel is changed. This issue is currently tackled in two ways: storing the spent waste or to reprocessing it to separate the different components of the fuel.

"For any nuclear program, there is a waste," Burnie told DW. "There is approximately 250,000 kilograms (551,000 pounds) of separated plutonium being stored around the world. It takes only 5 kilograms (11 pounds) to build one nuclear bomb."

What is nuclear energy's role in climate change?

Nuclear energy's role in fighting climate change remains uncertain. The nuclear industry has advocated atomic energy as a bridge to renewable energy in the shift away from fossil fuels because it only releases harmful carbon emissions into the atmosphere during the construction of the plant.

For Steven Kerekes, a senior media director for the Nuclear Energy Institute, atomic energy is vital to protecting the environment while ensuring reliable and affordable electricity.

“Nuclear energy is a proven way to drive economic growth and generate large amounts of carbon-free electricity on a 24/7 basis by splitting uranium atoms rather than burning a fossil fuel source,” he told DW.

Shaun Burnie, a senior nuclear campaigner for Greenpeace, disagrees with the NEI's arguments. Instead, he says nuclear plant owners are attempting to discredit renewable energy as the declining industry struggles to survive.

“They are arguing renewables aren't able to provide electricity at necessary levels because they are inefficient,” Burnie told DW. “But if you look where renewable have grown, such as in Germany, you find that renewable energy provides reliable energy without risk of nuclear accidents.”

“Nuclear is not in any way competitive with renewables as the market is dictating,” he added.

What is Germany's stance on nuclear?

Germany is in the midst of a transition away from nuclear energy that began in 2000. Following the Fukushima disaster, the German government voted to accelerate the process with the goal of being nuclear-free by 2022.

The coalition agreed to close eight of the country's 17 operational reactors immediately in 2011. The remaining plants are gradually being shuttered, with the first such site, Grafenrheinfeld, closed ahead of schedule in May.

Sylvia Kotting-Uhl, who is responsible for nuclear energy for the German Green Parliamentary Group, said that renewable energy holds a larger market share than nuclear energy in Germany, at 29 percent and 16 percent respectively.

“This proves our green argument right: we can substitute nuclear energy easily,” Kotting-Uhl told DW.

Burnie argued that the energy transition on a global scale is not as fast as it could be because “of the vested interests of oil, gas, coal and nuclear.”