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Russia is accusing Ukraine of planning to use a so-called dirty bomb, an allegation dismissed by Kyiv and its Western allies as a false-flag operation that Moscow could use as a pretext to escalate the Kremlin’s war against its neighbor.

A dirty bomb is a weapon that combines conventional explosives like dynamite and radioactive material like uranium. It is often referred to as a weapon for terrorists, not countries, as it is designed to spread fear and panic more than eliminate any military target.

Ukrainian officials have repeatedly denied Moscow’s accusations and Kyiv’s foreign minister has invited UN inspectors to visit Ukraine to show they “have nothing to hide.”

Here’s what you need to know.

Without providing any evidence, Moscow claims there are scientific institutions in Ukraine housing the technology needed to create a dirty bomb – and accuses Kyiv of planning to use it.

The Russian Defense Ministry said in a briefing on October 24 it has information that shows Kyiv is planning a provocation related to the detonation of a dirty bomb.

“The purpose of this provocation is to accuse Russia of using weapons of mass destruction in the Ukrainian theater of operations and thereby launch a powerful anti-Russian campaign in the world aimed at undermining confidence in Moscow,” claimed Igor Kirillov, chief of Russia’s Radiation, Chemical and Biological Protection Forces.

Russian Defense Minister Sergei Shoigu made the claim in a call with US Defense Secretary Lloyd Austin on October 23, according to a US official familiar with the conversation.

Shoigu also made similar comments to his French and British counterparts.

Russia plans to raise its accusations against Ukraine at the UN Security Council on October 25, according to Reuters.

Russia’s allegations have been strongly refuted by Ukraine, the United States, the United Kingdom, the European Union and NATO, which have in turn accused Moscow of trying to launch its own false-flag operation.

“Everyone understands everything well, understands who is the source of everything dirty that can be imagined in this war,” Ukrainian President Volodymyr Zelensky said in his nightly address on October 23.

The White House said on October 24 it is “monitoring as best we can” any potential preparations for use of a dirty bomb in Ukraine but doesn’t see anything to indicate the imminent use of such a weapon.

The UN’s nuclear watchdog said on October 24 it will send inspectors to visit two nuclear locations in Ukraine after receiving a request to do so from authorities in Kyiv.

The International Atomic Energy Agency (IAEA) said it was “aware of statements made by the Russian Federation on Sunday about alleged activities at two nuclear locations in Ukraine,” according to a news release on the agency’s website.

The IAEA did not give the location of the two sites.

In a tweet on October 24, Ukrainian Foreign Minister Dmytro Kuleba said: “Unlike Russia, Ukraine has always been and remains transparent. We have nothing to hide.”

No.

The blast from a dirty bomb is generated by conventional explosives. The blast from a nuclear weapon is generated by a nuclear reaction, such as the atomic bombs the US dropped on Japan in World War II.

“A nuclear bomb creates an explosion that is thousands to millions of times more powerful than any conventional explosive that might be used in a dirty bomb,” according to a fact sheet from the US Department of Homeland Security (DHS).

The blast from a nuclear weapon can flatten entire cities. For instance, the atomic bomb dropped on Nagasaki in 1945 obliterated 2.6 square miles (6.2 square kilometers) of the city, according to ICAN, the International Campaign to Abolish Nuclear Weapons. The conventional explosives in a dirty bomb may only flatten or damage a few buildings.

Meanwhile, the mushroom cloud from a nuclear explosion could cover tens to hundreds of square miles, spreading fine particles of nuclear material – radioactive fallout – over that area, DHS says.

Most of the radioactive material from a dirty bomb would be spread over a few city blocks or a few square miles, according to DHS.

No.

In 1995, Chechen rebels planted but failed to detonate one in a Moscow park, according to the Council on Foreign Relations.

There have been reports that terrorist organizations such as al Qaeda or ISIS have built or tried to build a dirty bomb, but none has ever been detonated.

The DHS says it would be unlikely a dirty bomb could deliver high enough doses of radiation “to cause immediate health effects or fatalities in a large number of people.”

The Texas Department of State Health Services explains why.

To make a dirty bomb capable of delivering deadly doses of radiation, large amounts of shielding from lead or steel would be needed to keep the material from killing its makers during construction, it says.

But using such shielding material would make the bomb bulky and hard to move or deploy, probably requiring heavy equipment and remote handling tools, and it would limit how far the radiation could spread, according to the Texas state agency.

The radiation generated by a dirty bomb would cause similar levels of exposure to the amount received during dental X-rays, according to Texas health services.

“It is like breaking up a rock. If someone was to throw a large rock at you it would probably hurt and it may cause you physical damage,” the department explains. “If they take the same rock and break it up into grains of sand and then they throw the sand at you, the chances of it causing you any real damage are significantly lower.”

The severity of radiation sickness is affected by exposure over time, according to the DHS. Preventative measures can be as simple as walking away.

“Walking even a short distance from the scene (of the explosion) could provide significant protection since dose rate drops dramatically with distance from the source,” DHS says.

People should also cover noses and mouths to avoid ingesting any radiation, get indoors to escape any dust cloud, discard their clothing in a plastic bag and then gently wash their skin to remove contaminants, the DHS says.