Misinformation about missing radioactive cylinder in Thailand fuels panic

“Caesium-137 disappeared in Prachinburi province for nearly 10 days," reads a Thai-language Facebook post, referring to a province east of Bangkok where a 25-kilo (55-pound) steel tube containing highly radioactive caesium-137 was reported missing from a power station on March 10.

"Some reports say it was lost even earlier on February 23 before it was eventually melted down. If this is true, the caesium's vapours will cover a distance of 1,000 kilometres, severely harming life."

The post warns the Caesium-137 in the missing cylinder poses a cancer risk and will take 100 years to break down.

"Look at the area the vapours could travel over. It covers the entire country of Thailand and even reaches its neighbours," it adds.

The post shows a Google Maps image of the area surrounding Prachinburi and a BBC Thai timeline of the crisis.

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A screenshot of the false post, captured on March 28, 2023

Caesium-137 is a radioactive chemical element that is a by-product of the fission process in a nuclear reactor.

Officials said on March 20 said they had found traces of Caesium at a steel mill -- where they suspect the tube was transported before being melted down -- located around 10 kilometres (six miles) away from the coal-fired power plant in Prachinburi province.

Authorities are still investigating the incident and it is unclear if all the missing cylinder has been found, as of March 31.

Prachinburi governor Ronnarong Nakornjinda said that if it had been melted, the radioactive material would have been contained within a "closed" area and there was no sign of contamination outside the plant.

Health officials added on March 24 that none of the mill's 70 workers were reported to be unwell.

But numerous online posts, including two here and here, have compared the incident to the Chernobyl nuclear accident of 1986, the worst disaster in the history of nuclear power generation. Studies have found that caesium-137 from the Chernobyl site affected European countries more than 1,000 kilometres (600 miles) away.

Comments from internet users suggested many believed that radioactive vapour from the Thai province could also travel 1,000 kilometres.

"This is so bad. What irresponsible behaviour! I do not feel safe. I am worried," one wrote.

Another said: "Feeling so sorry for myself right now as I live nearby!"

'Incomparable' to Chernobyl

However, nuclear experts told AFP that the risks from the incident in Thailand were not nearly as severe as portrayed in the social media posts.

Yuttana Tumnoi, deputy spokesperson for the Office of Atoms for Peace, the main authority for nuclear research in Thailand, said on March 29 that the loss of the cylinder was "a drop in the ocean" compared to the Chernobyl meltdown due to the vast difference in the amount of radioactive substances involved.

He said Thai scientists with his office estimated the cylinder contained 0.0005 grams of caesium-137 when it disappeared.

By contrast, the caesium-137 released at Chernobyl was 53 million times greater, according to Nanba Kenji, a professor at the Department of Symbiotic Systems Science at Fukushima University in Japan.

Kitiwat Khamwan, assistant professor and medical physicist in the Department of Radiology at Thailand's Chulalongkorn University, gave AFP a similar assessment on March 28.

"It is incomparable. It is impossible for these radioactive particles to spread over 1,000 kilometres nor is there a need for people to flee the country," Kitiwat said.

A senior director for nuclear materials security at a think tank based in Washington also told AFP on March 28 that the threat was being overplayed.

"0.0005 grams is a relatively small amount that should not pose a widespread public health hazard," said Ross Matzkin-Bridger at the Nuclear Threat Initiative.

"Even if this caesium were fully dispersed into the environment, it is highly unlikely that it would be able to travel long distances in any significant concentration required to impact human health," he added.

Yuttana said that even if the tube was melted down at the steel mill, the site is a closed-loop operation with safety measures in place, meaning only a small amount of caesium vapour "far less than one gram" would have been released.

His team has checked radiation levels within 10 kilometres of the mill and found no anomalies related to caesium-137, Yuttana added, but they will continue to monitor the readings for at least a year to ensure safety.

The false Facebook post uploaded on March 20 also makes the claim that the caesium "will decay over a timespan of 100 years". Yuttana told AFP that caesium takes about 300 years before it ceases to be radioactive.