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What is a 'dirty bomb,' and what damage can it cause?

As tensions over the nine-month war in Ukraine worsen, NBC News looks at what a so-called dirty bomb is and whether it can render any military advantage.

U.S. and Ukrainian alarm over a flurry of Russian claims that Kyiv plans to deploy a so-called dirty bomb have worsened fears that President Vladimir Putin could try to escalate the conflict to try to change the course of the war. 

Ukraine and its allies vehemently reject the Russian accusations, countering that, in fact, the Kremlin may be planning a “false flag” operation, blaming Kyiv for its own actions.

As tensions over the nine-month war worsen, NBC News looks at what a dirty bomb actually is, the damage it can cause and whether it can render any military advantage.

What is a dirty bomb? 

A dirty bomb, also known as a “radiological dispersion device,” is defined as a conventional weapon that has been augmented with a radioactive material. Traditionally, security experts have warned of dirty bombs’ being used by terrorist groups instead of militaries. 

The method of delivery could be a missile, an airplane stocked with radioactive materials or a strategically planted improvised explosive device, according to the Washington-based Center for Arms Control and Non-Proliferation.

It’s a basic, rudimentary device that’s easy enough to make with explosives and radioactive material, said nuclear expert Tom Plant, a senior associate fellow at the Royal United Services Institute, a defense and security think tank in London. 

A variety of radioactive materials could be used, he said, including materials used in nuclear medicine and for industrial purposes. When it’s deployed, the material doesn’t do anything to make the explosion any bigger, he said — it’s there purely to create contamination and, most likely, panic.

What damage can it cause? 

Just how devastating a dirty bomb can be depends on the type and size of the conventional explosives, as well as the potency and amount of radioactive material that has been added.

The main danger comes from the explosion, not the radiation, according to the guidance on radiological dispersion devices from the Centers for Disease Control and Prevention.

“Only people who are very close to the blast site would be exposed to enough radiation to cause immediate serious illness,” according to the guidance. “Still, radioactive dust and smoke can spread farther away and could be dangerous to health if people breathe in the dust, eat contaminated food or drink contaminated water.”

Pavel Podvig, a senior researcher at the U.N. Institute for Disarmament Research, said on Twitter that a “dirty bomb” contamination area is likely to be no more than a few hundred yards in diameter. 

“To create serious contamination over a large area one would have to blow up a nuclear reactor, Chernobyl-type,” Podvig said. 

Plant said the psychological damage from deploying a dirty bomb in Ukraine would probably be far-reaching.  

“The fact that it’s dirty — in that the contamination spreads around — is the kind of thing that people get scared of,” he said.

It could also overwhelm hospitals as people rush to get assessed for radioactive poisoning even if they aren’t sick, and it could cause widespread disruption as authorities undertake a potentially extensive clean-up, Plant said.

Why are we talking about a dirty bomb now? 

The Kremlin is claiming Ukraine plans to use a dirty bomb as a provocation to blame Russia for the resulting radioactive contamination as defense chief Sergei Shoigu says Ukraine is trending toward “a further uncontrolled escalation.”

The U.S. and Kyiv’s other Western allies have unanimously rejected the claims as “transparently false,” saying they could be a way for Russia to lay the groundwork for an escalation of its own as its military struggles to make progress on the battlefield. The State Department said Monday, however, that it still had no indication that Russia was preparing to use nuclear weapons or a dirty bomb.

Russia doubled down on its claims Tuesday, and it was expected to press the issue at the U.N. Security Council.

Who has the capabilities? 

The Russian Defense Ministry said Monday that Kyiv has the “scientific, technical and industrial potential” to create a dirty bomb.

It said that nuclear industry enterprises in Ukraine have stocks of radioactive substances and that two organizations have already received “specific instructions” to create the weapon. The ministry provided no evidence, and NBC News couldn’t verify the claims.

Kyiv has steadfastly denied it’s working to create or deploy a dirty bomb, and it has called for international monitors to confirm that.

Police officers in hazard suits secure the scene in a "hazardous material hot area" after the explosion of a "dirty bomb" during a simulated attack at a dock at the Port of Los Angeles on Aug. 5, 2004.
Police officers in hazard suits secure a "hazardous material hot area" after the explosion of a "dirty bomb" during a simulated attack at a dock at the Port of Los Angeles in 2004.David McNew / Getty Images file

Plant said both countries have the ability to create a “dirty bomb,” as does any country in possession of explosive and radioactive materials.

But an actual nuclear weapon would be a much bigger technical challenge, one the “Ukrainians haven’t ever investigated and have no capability to do,” Plant said, adding that “the Russians obviously have lots of nuclear weapons already.”

Russia has nearly 6,000 nuclear warheads, according to the Stockholm International Peace Research Institute. Ukraine, long part of the Soviet Union and before that the Russian empire, agreed to give up its nuclear arsenal after it became independent in exchange for security guarantees from Moscow and the West.

Would it give either side an advantage?

A dirty bomb attack has never been recorded, and if one were deployed in Ukraine, it would likely strike terror in the people immediately affected. Militarily, however, it would be unlikely to give either side much of an advantage, experts said.

“If somebody for some reason uses a ‘dirty bomb,’ it will not change anything militarily, politically or otherwise,” Podvig, of the U.N. disarmament institute, said in another tweet.

Plant said that given its relatively limited destructive power, the contamination a dirty bomb could cause wouldn’t be likely to deny the enemy much territory or make it hard to move through any given area. 

“It just wouldn’t have the same area-denial potential as, say, chemical weapons or a nuclear weapon or anything like that,” he said. 

“It’s completely the kind of thing that would just scare civilians.”