The security surrounding its departure on Jan. 21 indicates that something out of the ordinary is aboard. The Pacific Sandpiper and several sister ships make no port calls on their voyages between Europe and Japan because they carry potentially lethal nuclear material.

In the Pacific Sandpiper's hold on this journey to Japan via the Panama Canal is only one item of cargo — a giant cylinder weighing more than 100 tons. Inside are 28 containers, each made of stainless steel nearly one-third of a meter thick. They are packed with 14 tons of highly radioactive waste that has been turned into solid glass form to make it safer and easier to handle.

It is the first of a series of such shipments planned for next few years to Japan from Britain's Sellafield nuclear storage and reprocessing complex. Three years ago, a dozen similar shipments from France to Japan were successfully completed. Used fuel from nuclear power reactors that generate about one-third of Japan's electricity has been shipped to Europe for reprocessing since 1969, while vitrified waste has been sent back to Japan by sea since 1995.

There have been over 170 of these ocean shipments covering more than 8 million km without any incident involving the release of radioactivity, according to the Euro-Japanese company that operates the fleet of purpose-built vessels.

But the elaborate and costly arrangement casts light on two of the most problematic and controversial aspects of civilian nuclear power — how to prevent the spread of nuclear weapons material and knowhow to terrorists and rogue states, and how to store nuclear waste safely for the long-term when it can remain radioactive for hundreds of years.

With the number of power reactors expected to rise from 435 in 31 countries to nearly 570 in 42 countries by 2020, and with much of this expansion expected to take place in Asia and the Middle East, the need for safeguards on uranium or plutonium processing that could be used to make nuclear weapons is obvious.

Recycling fuel from nuclear reactors under strict national and international regulations is one method being developed. When uranium oxide fuel has been used in a reactor for three or four years, it becomes less efficient and is replaced with fresh fuel.

The spent fuel can then be chemically treated to recover usable uranium, associated plutonium and radioactive waste, a system known as reprocessing. Although expensive, this cycle provides up to 25 percent more energy from the original uranium. It also reduces the volume of high-level waste to about one-fifth of what it would otherwise be.

Eventually, advances in reprocessing and a new generation of fast reactors may be able to recover and re-burn even more of the fissile and radioactive material from used fuel, further reducing waste and the proliferation risk.

So far, about 90,000 tons of used fuel from commercial power reactors have been reprocessed, mainly in Britain, France and Russia. By 2030, another 400,000 tons of used fuel is likely to pile up, an average of 20,000 tons a year.

At present, annual global reprocessing capacity is about 3,800 tons per year for normal uranium oxide fuel, and about 1,700 tons for other nuclear fuels, according to the World Nuclear Association.

Much of the spent fuel piled up by 2030 will be in Asia. Japan, India, China and South Korea aim to emulate the main reprocessing centers in Europe and Russia. They see the technology as the key to a lucrative nuclear service industry as well as being one that is vital to their own energy security.

Meanwhile, power reactors in most countries have been built without safe long-term underground storage arrangements being put in place, mainly because of the high cost involved and public resistance at potential sites.

In the United States, which generates 20 percent of its electricity from nuclear power, opponents of a plan for a national repository beneath Yucca Mountain in Nevada, have stymied it for years.

A recent analysis by the U.S. Government Accountability Office said it could cost as much as $67 billion to build the Yucca facility and operate it for about 150 years.

High-level radioactive waste is accumulating at a rate of about 12,000 tons per year worldwide. When used fuel is removed from a reactor, it must cool for up to 50 years under water in secure pools or in dry storage, where circulating air gradually removes the heat.

The level of both radioactivity and heat from spent fuel, or from the dangerous waste material extracted from the fuel during reprocessing, fall rapidly in these years down to about one-thousandth of the level when the fuel was removed from the reactor.

During this period, storage may be at one central place, as in Britain's Sellafield complex, or at the reactor site where the spent fuel was removed, as in the U.S.

But either way, the time for permanent storage of the most toxic waste deep underground in geologically stable rock, salt or clay in countries that have been generating electricity from nuclear power for decades is fast approaching.

Without a long-term solution, the pile of radioactive "rubbish" will become so big and so widely dispersed that it may be impossible to manage safely.