When the Cold War ended, many people believed the world was finally safe from nuclear weapons. But in the chaos that followed the dissolution of the Soviet Union, a new threat emerged: nuclear terrorism. The threat has only grown more dire in recent decades. If terrorists were to get their hands on nuclear materials, they could cause death and destruction on a whole new scale.

This is not a far-off scenario. Today, nuclear technology is used all over the world. But not every nuclear facility has proper security. Each year, more than 100 thefts and incidents involving radioactive materials are reported. Some are minor, but others are troubling. Criminals were recently caught trying to sell highly enriched, bomb-grade nuclear materials in Moldova and Georgia. Armed intruders broke into a nuclear site in South Africa. A hacker tried to sabotage a power reactor in Lithuania. And this is just the tip of the iceberg.

What does nuclear terrorism look like?

So far, we have not seen a terrorist group pull off a nuclear or radiological attack—but there are several ways it could happen. They could steal a bomb, build one, attack a nuclear facility, or make a “dirty bomb” from stolen radioactive material.

Obtaining a nuclear weapon from a country’s stockpile is hard to do—but not impossible. To date, no nuclear bomb has been known to have been stolen, and most are held in highly secure military sites.

A terrorist group could also try to build a nuclear bomb using stolen highly-enriched uranium or plutonium. In one worrisome incident in 2001, the former head of Pakistan’s Khushab Plutonium Reactor met with Osama bin Laden to discuss how al-Qaeda might obtain a nuclear bomb.

Attacking a nuclear power plant would also be difficult—but less so. Terrorists could find a way to sabotage a plant, causing radiation to escape into the environment. In 1992, for example, a hacker named Oleg Savchuk was arrested for trying to sabotage the Ignalina Nuclear Power Plant in Lithuania using a computer virus. Other people have successfully broken into reactors and attempted to damage them with explosives, but so far none of these attacks caused a major release of radioactivity.

But the most likely scenario for a nuclear terror attack is a radiological dispersal device, known as a “dirty bomb.” Terrorists could use small amounts of highly radioactive material combined with conventional explosives to create a device that contaminates large areas with harmful radiation. While this wouldn’t produce a nuclear blast, it would cause severe damage.

A history of close calls

Theft and smuggling of nuclear and radioactive material happen more often than you might think. As of December 2015, the International Atomic Energy Agency (IAEA) had recorded 762 instances of loss or theft, and 454 instances of unauthorized possession.

Some of the most worrying incidents happened during and after the breakup of the former Soviet Union, which left scores of nuclear sites vulnerable. But it’s not only ex-Soviet sources that we need to worry about. We’ve also seen dangerous incidents in South Africa, Iraq, and Japan, and elsewhere.

If the international community doesn’t do more to secure nuclear sites and reduce their excess stockpiles of nuclear materials, we can expect to see more of these incidents. And it’s only a matter of time before terrorists are successful.

What’s being done to protect nuclear materials?

After the terror attacks of 9/11 and the emergence of large, global terrorist organizations like Al Qaeda, countries have started working together to improve the security of nuclear materials around the globe. A number of initiatives have sprung up to support this effort.

We have to do more

Globally we’ve made progress on nuclear security, but there are still too many gaps. Despite the growing number of international fora and initiatives to improve nuclear security, many governments around the world aren’t convinced of the severity of the nuclear terrorism threat.

As long as weapons-grade materials are available, there is a risk that they’ll be stolen.

Many of the world's civilian nuclear facilities are not well protected against terrorist attacks—in some cases, there aren’t even armed guards. Insider threats and cyber security are not adequately addressed. There are over 70 civilian research reactors in 20 countries that continue to use highly enriched uranium, which can be used in nuclear bombs, instead of converting to low-enriched uranium. About a dozen countries own plutonium that they have separated out from their spent reactor fuel. These plutonium stocks are growing, and there is no international agreement to halt—let alone reverse—this trend.

If countries don’t work together to rise to the challenge, it’s only a matter of time before we face the consequences. But what can be done?

There are now two major, legally binding international agreements that require countries to protect nuclear materials and facilities from sabotage and terrorism. But neither provides specific guidance on actual security standards. IAEA documents and recommendations are more specific, but adherence to those guidelines is voluntary. Sharing of information about terrorist threats, actual security incidents, and countries’ responses is still too limited and needs to be improved.

A more stringent international system of standards should hold countries accountable for not following proper guidelines and security measures—including measures to prevent cyber attacks. It could involve mandatory peer review, publication of information, and participation in security initiatives.

All nations need to commit to reducing stockpiles of bomb-grade uranium (HEU) at civilian facilities and use low-enriched uranium (LEU) in research reactors instead. As long as weapons-grade materials are available, there is a risk that they’ll be stolen.

For security reasons, most countries are reluctant to commit their military materials to the same scrutiny as their civilian stockpiles. But countries need to explore ways to ensure that they’re secure.

Above all, we must keep the threat of nuclear terrorism in the political conversation. As citizens, we need to remind our representatives that these issues are important and keep them in the public sphere.

So far, the world has been lucky that we haven’t seen a catastrophic incident of nuclear terrorism. Now we need to be smart, too.