Western officials were quick to dismiss Russia’s claims over the weekend that Ukraine was planning to use a so-called dirty bomb on its own territory. The United States and its allies have issued a series of statements accusing the leadership in Moscow of making “manifestly false allegations” in order to create a pretext for escalating the war.
But the intense exchanges over the past few days have drawn attention to the concept of the dirty bomb itself.
It is a type of weapon that was conceived and tested more than three-quarters of a century ago, in the early years of the nuclear age, but was never used by a military force.
After the September 11 attacks, government officials occasionally warned that terrorists could use radioactive materials used in many commercial industries to build one, and dirty bombs became a bogeyman, an object of fear, in the public consciousness.
The bombs’ more formal name – Radiological Dispersal Devices, or RDD – provides a fairly simple description of what these weapons are and how they work.
Essentially, they are improvised bombs that use conventional explosives to spread radioactive material around the area. But the fact that no military is known to have one in their arsenal is a good indicator that they’re not useful on the battlefield.
What are these weapons?
The most commonly presented version is generally small enough to fit in a backpack and contains perhaps 20 pounds or less of explosives with a smaller mass of radioactive material placed on top.
That’s about the magnitude, although such a weapon could potentially be made much larger.
However, there are some inherent problems with this concept that limit a bomb maker’s chances of success. First, the size of the main charge: use too much explosive material and the radioactive substance could be largely consumed by the intense heat from the bomb’s detonation. Use too little and the device would not spread the radioactive material very far.
Another consideration is that few radioisotopes commonly used for medical purposes or to generate electricity are suitable for use in this type of device.
A radiological propagation device is not a “nuclear weapon” in the classical sense, since there is no fission, fusion, massive release of energy, or destruction of cities.
What happens when one explodes?
When everything works correctly — and as an improvised bomb, there are many potential points of failure — a dirty bomb blasts radioactive material into tiny pieces and emits it into the surrounding air. It creates a localized contamination problem, not a global one.
People who breathe or ingest radioactive dust could be injured or killed, and contaminated buildings would have to be bulldozed and sent to a landfill. Excavators would likely dig up a meter of contaminated soil and tear down nearby trees – all of which would also go to landfill.
But many of the effects would depend on atmospheric conditions.
Temperature gradients would affect how high the cloud of radioactive material could rise in the air, and wind speed and direction would determine how far it could travel from the blast.
A scholarly paper published in a US military magazine on the subject in 2004 found that “economic and psychosocial effects are likely to be the most serious mechanisms of harm from the use of an RDD.”
“Fear of ionizing radiation is a deep-seated and often irrational holdover from the Cold War,” states the report. And while an attack using this type of device is “unlikely to cause mass deaths,” it has the potential to cause “great panic and huge economic losses.”
Are there other risks?
When building this type of weapon, there is a significant risk for the bomb maker.
For the weapon’s radiation to be lethal, the radioisotope used would need to be of an intensity strong enough to harm humans.
When the bomb makers acquire radiological material contained in a shielded container—that is, a ship designed not to emit harmful rays—they face a critical decision: whether or not to attempt to remove the radioactive material .
The bomb makers may think that removing the shielding will allow for better distribution of the radioactive material. However, doing so can expose them to close-range exposure to harmful ionizing radiation long enough to cause real harm to their bodies – a fundamental hazard of working around radioactive materials.
The closer the attacker gets to a dangerously radioactive material—and to construct such a device one would typically have to be in range to do so—the more intense its damaging effects would be. The bomb makers could be exposed to a lethal dose of radiation before they even finish their job.
Then there’s a chance the attacker will be spotted en route to planting the bomb, with a strong radioactive source potentially triggering detectors along highways and bridges alerting law enforcement.
Has the US military ever built such a weapon?
According to government documents, from 1948 to 1952 the US military experimented with radiological propagation equipment at the Dugway Proving Ground in Utah, but that work was eventually halted.
Aside from these tests, which involved building radiological propagation devices of various types, there is no evidence that the US military or any other military force has ever used such a weapon for combat use.