The unanswered questions over alarming uranium discovery at Heathrow Airport

During the lull between Christmas and the new year, something alarming flashed up on Heathrow Airport’s specialist scanning technology.

From the depths of a shipment of scrap metal, a radioactive signal.

While false alerts can sometimes be triggered, this one was not one of them.

Metal bars embedded with uranium had made the 3,700-mile journey to London from Pakistan, via Muscat in Oman.

Had it not been intercepted by Border Force officials on Dec 29, the substance would have reached its intended recipient - an Iranian business with premises in the UK.

When enriched, uranium could be used to build a "dirty" bomb, where nuclear substances are mixed with conventional explosives.

Counter-terrorism officers have launched an investigation into how and why this material managed to reach the UK, but they have said no “threat to public health or public safety” had been identified.

Professors and experts have echoed this, suggesting the reportedly small amounts of uranium are unlikely to have been part of a sinister plot - and that it shows that our precautionary technology is working.

But key questions still remain - why was this company forking out to ship scrap metal via air, something almost unheard of across the industry because it is so expensive? Why was it sent to an Iranian business?

"The terror threat is a huge concern," said retired colonel Hamish de Bretton-Gordon, former commander of UK and Nato Chemical, Biological, Radiological and Nuclear Forces.

He told The Telegraph: "The fact it was destined for an Iranian company really does raise the spectre of was this a sample?

"Iran supports global terror. I wouldn’t be at all surprised if they have their fingerprints all over this.

"Why would you ship scrap metal on an aeroplane? Imagine the cost, it would be phenomenal.

"There is no good reason to put uranium in the post, but there are a lot of bad reasons."

Depleted uranium - uranium-238 - is a dense metal produced as a by-product of enriching natural uranium to create nuclear fuel.

It can be used in the keels of yachts, as counterweights for aircrafts, for munitions and as the tips of tank missiles.

Researchers have suggested the uranium could have been picked up from used weapons on a battlefield by scrap merchants, given Pakistan’s proximity to Afghanistan, and then included in the consignment sent to the UK.

Prof Andrea Sella, University College London’s professor of inorganic chemistry, said uranium was used in weapons to give artillery shells, for example, added weight to penetrate armour.

“If it was actual metal and small amounts, you wonder whether this is the potential leftovers from the battlefield that might have been assembled by scrap merchants,” he said.

He said uranium was an unlikely source material for a dirty bomb, because of its weight and chunkiness compared with other radioactive substances that would produce a finer dust cloud.

“There are much more active radionuclides that could be used. If you are going to make a dirty bomb, you want to maximise how much radioactivity it produces. Things with shorter half lives than uranium are likely to be much more effective,” he said.

One theory under investigation is that the material ended up in a consignment of scrap metal because of mistakes and “poor handling” in Pakistan.

The discovery at Heathrow put the country, which was for decades at the centre of worldwide concerns about nuclear security, back under the microscope.

While safety watchdogs and terrorism experts say Pakistan's risk has reduced in the last 10 years, AQ Khan - its former nuclear weapons scientist - previously sold technology secrets to rogue regimes including Iran.

Asfandyar Mir, of the US Institute of Peace, said that although the country takes security seriously and safeguards had improved: “The concern has been and remains that the broader environment in which Pakistan's materials and infrastructure exists is always under enormous stress due to a range of terrorist and even rogue state actor threats."

Khan, who died last year, was considered by many intelligence agencies to be the most dangerous man in the world during the 1990s. He helped Iran establish its nuclear programme.

Prof Claire Corkhill, chairman in nuclear material degradation at the University of Sheffield and a member of the UK Government’s Committee on Radioactive Waste Management (RWM), said scrap metal can often be contaminated with radioactive substances.

Guidance from the Health and Safety Executive states that radioactive materials have become incorporated into the scrap metal chain previously, including when orphan sources of radiation have been melted into steel.

"Sometimes when scrap metal recycling happens they don't really check everything [that] gets thrown into the scrap metal recycler and then everything in that batch can be contaminated with depleted uranium", she said.

Meanwhile Prof Geraldine Thomas, a professor of molecular pathology at Imperial College, director of the Chernobyl Tissue Bank and a member of the RMW committee said the level of contamination discovered is likely to be "low".

"It's a bit like the fact that we knew that Chernobyl had gone off because the Swedish power stations picked up the radioactive cloud,” she said. “These things are incredibly sensitive.

“I know people are worried about uranium, but if you go swimming in the sea, you're exposed to uranium. This whole idea that any amount of radiation is going to damage your health is complete fallacy.

"It is highly unlikely that this is somebody who is going to set up a dirty bomb, it is much more likely to be from contamination because the rules have not been followed as well as they should have been in another country.”

Pakistan has four uranium mines near the cities of Qabul Khel, Nanganai, Taunsa, and Baghalchore, according to the James Martin Centre for Non-Proliferation Studies.

Security has improved in recent years, according to the Washington-based watchdog Nuclear Threat Initiative (NTI), though the country still languishes well down international rankings.

A league table of nuclear nations drawn up by NTI, puts Pakistan at 19 out of 22 for securing nuclear materials and 33 out of 47 for protecting facilities.