Why Does UXO Degrade Over Time?

Unexploded ordnance (UXO) refers to explosive ordnance which has been primed, armed, fused or otherwise prepared for action. It may have been buried, dropped, fired, launched, projected, thrown, abandoned or placed in such a manner as to constitute a hazard and remains unexploded either by design, malfunction or for any other cause.

Over time, UXO degrades due to various environmental, chemical, and physical factors, which can alter its stability and increase the danger it presents.

Environmental exposure

Items of UXO are often exposed to elements such as moisture, oxygen, and salts. This exposure can lead to corrosion of metal casings, weakening the structural integrity of the ordnance.

The type of soil or water in which UXO is embedded can also significantly affect its rate of degradation. Acidic or alkaline soils can accelerate chemical reactions with the munition materials, leading to faster deterioration.

In underwater settings, factors such as salinity, temperature, and microbial activity further influence the corrosion process. For instance, in the Baltic Sea, it’s estimated that approximately 300,000 tons of UXO lie dormant, gradually corroding and posing environmental hazards. Studies have shown that the casing material of UXO determines its susceptibility to corrosion, impacting its condition after decades underwater.

Chemical decomposition

Breakdown of explosive compounds

Explosive materials within items of UXO, such as TNT, can chemically degrade over time. This degradation may result in the formation of more sensitive compounds, increasing the risk of unintentional detonation. Additionally, the leaching of these chemicals into surrounding soil or water poses environmental hazards, contaminating ecosystems and potentially entering the food chain. This could include toxic substances, such as heavy metals and explosive residues, which can persist for decades.

Deterioration of detonators and fuses

The components designed to initiate explosions, including detonators and fuses, are susceptible to ageing. Factors such as corrosion, moisture ingress, and material fatigue can compromise their functionality, making the UXO more unpredictable and sensitive to disturbances. The condition of the casing is a relevant factor to consider in preparation for UXO handling, as it affects the sensitivity of explosive materials and the functionality of the fuse.

Physical disturbances

It’s important to note that while UXO degrades over time, they typically do not spontaneously explode; an external trigger is usually required. However, degradation can make these devices more unstable, increasing the likelihood of detonation upon disturbance. Factors such as changes in temperature, vibrations, or direct impacts – common during activities like excavation or construction – can serve as triggers. In some cases, disturbances may reactivate mechanical components within the fuse, leading to detonation.

UXO can also be subjected to physical stresses from environmental events like earthquakes, floods, or wildfires. These disturbances may cause cracks or displacements in the ordnance, altering internal pressures and potentially triggering detonation.

The dangers of UXO

So far nobody in the UK has been killed by a UXO incident, however, there sadly have been several fatalities in Europe where construction workers and EOD engineers have been seriously injured or killed by UXO-related incidents. One example of this was in 2014 when a construction worker in Germany was killed after a power shovel struck a WWII bomb. Two others were also critically wounded in this terrible incident.

Another example of the dangers posed by ageing UXO occurred in October 2024 at Miyazaki Airport in Japan. A 500-pound WWII bomb, buried beneath a taxiway, detonated unexpectedly. Luckily there were no injuries, however, the explosion caused extensive damage to the runway, leading to significant flight disruptions and highlighting the ongoing risks posed by historical ordnance.

Investigations suggested that environmental degradation had weakened the casing, allowing an external factor, possibly vibrations from taxing aircraft, to trigger the detonation. This incident reinforces the need for thorough UXO risk mitigation ahead of construction or development work, particularly in areas with known wartime contamination.

UXO risk mitigation services

Despite the passage of time, UXO remains incredibly hazardous. In some cases, degradation processes can make them more sensitive, heightening the risk of detonation. Therefore, it is imperative that any suspected UXO is reported to authorities and handled exclusively by trained explosive ordnance disposal (EOD) professionals.

Brimstone specialises in UXO risk mitigation. Our team provides risk assessments, UXO surveys, on-site support and disposal services to protect your projects and ensure compliance with safety regulations. If you suspect the presence of UXO or need professional guidance, visit our website to learn more about our services and how we can assist you.

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