Metropolitan Police Office, Ranipokhari on Thursday said it has seized what it called a highly radioactive material, around 2.5 kg, from Boudha.

Four people have been arrested.

According to Senior Superintendent Sushil Singh Rathour, spokesperson for the Metropolitan Police Office, Ranipokhari, the arrest was made on a tip-off.

“We were informed that some people were trying to sell uranium after which our team raided the house of one of the arrestees at Boudha and arrested her and three others,” said Rathour. “The arrestees have been kept in Kathmandu Metropolitan Police Range for further investigation.”

Police claim the seized radioactive material to be uranium-238.

Uranium-238 is the most common isotope of uranium found in nature and accounts for more than 99 percent of all naturally occurring uranium.

This form of uranium, though highly radioactive, is said to be of no use for making nuclear weapons.

Police said they were yet to ascertain the worth of the confiscated material.

According to preliminary investigation, said police, one of the arrestees had the material at her home in Boudha “for a very long time.”

“Her father-in-law used to work in uranium mines in India some two decades ago. The man brought home some uranium with him and had kept it at his home,” said Senior Superintendent Ashok Singh, chief of Kathmandu Metropolitan Police Range.

Her father-in-law is now 86 years old and currently lives in the United States, according to Singh.

“After learning that it was a high-value material, she tried to sell it with the help of three other people,” said Singh. “We confirmed from the Nepal Academy of Science and Technology that the confiscated item was raw uranium-238.”

Dr Suresh Kumar Dhungel, spokesperson for the Nepal Academy of Science and Technology, however, said they were yet to verify if the confiscated material is uranium-238.

“From the sample, we found out that the substance contains highly radioactive material, but we are yet to ascertain what exactly it is,” Dhungel told the Post over the phone.

Uranium is used in nuclear plants and nuclear weapons but there is no agency, technology or centre in Nepal where this material can be used, according to Dhungel.

But the form of uranium used in nuclear plants and nuclear weapons is uranium-235 and not uranium-238, which the police claim to have seized from the arrestees. Uranium-235 makes up about 0.72 percent of natural uranium.

Unlike uranium-238, the predominant form of uranium found in nature, uranium-235 is fissile, which means it can sustain a fission chain reaction.

To use uranium-238 in nuclear weapons, it must be enriched. It was not clear immediately whether the confiscated material, even if it is uranium-238, can be turned into a dirty bomb.

“However, this is a cause for concern if someone is making an attempt to sell or smuggle uranium,” said Dhungel. “Police must carry out a thorough investigation, as smugglers could use Nepal as a transit point to smuggle radioactive materials into neighbouring countries like India and China.”

The District Administration Office, Kathmandu, has granted permission to keep all four arrestees in custody for five days for further investigation under the Explosive Act-2018, Singh told the post.

“Further investigation is underway,” he added.

Police said that this is the first of its kind arrest in the country, where people were trying to sell uranium.