Hi, Dr. Zoom! I read something recently about people losing radioactive sources – hundreds of them each year. How does this happen? And with all those sources being lost, are we all in danger?
That does sound a bit worrisome – in the 2023 Nuclear Material Events Database, the Nuclear Regulatory Commission notes that there were about 28,000 records of radioactive materials “events” between 1990 and 2023 – that comes out to more than 800 events each year. Of those, 2046 were lost, abandoned, or stolen radioactive sources between 2014 and 2023 – about 200 each year. That’s an awful lot of sources. But here’s the thing – not all of them are dangerous.
When I was working at a university we lost two radioactive sources – they were delivered to the university (or, at least, one of the technicians signed for them) but they were never delivered to the laboratory that ordered them. We searched and searched but weren’t able to find them – we had to report them to the regulators as having been lost. Here’s the thing – the amount of radioactivity contained in these sources was too small to ever pose a risk to anyone. Not only that, but they were “unsealed sources” – a few grams of radioactive liquid used for scientific experiments. There was too little radioactivity to harm anyone, even if a grad student decided to drink the stuff, but we had to report the loss to our regulators – this went down as two lost radioactive sources. Most of the nation’s – and the world’s – lost radioactive sources are like that – they’re radioactive, they’re lost, but they’re not a risk to anybody.
The International Atomic Energy Agency (IAEA) has categorized radioactive sources according to how much risk they might pose if people run across them unknowingly. The IAEA puts sources into one of several categories based on that risk. The sources that we have to worry about – the sources that might hurt people – are called Category 1 and Category 2 sources. The sources my university lost were Category 4 or 5 sources. In fact, most lost sources are like the ones we lost – of 145 lost sources reported globally in 2023, none were Category 1 (most dangerous), three were Category 2, and two were Category 3 (other categories are considered to be relatively innocuous).
The report I mentioned goes into a lot of details about each of these incidents, none of which I’m going to go into here because the details aren’t really relevant to your question. What is relevant is that there were 145 incidents in which radioactive sources were reported as having been lost in 2023 and, of those, only five (about 3%) had the potential to cause serious harm – and all of them were resolved fairly quickly without any injuries to anyone. The great majority of the lost sources were like ours – they had to be reported even though the amount of radioactivity wasn’t dangerous.
But this makes sense – there are a LOT more low-activity sources than there are high-activity sources, just as there are a lot more grains of sand than there are boulders. Which is just another way of saying that most of the lost radioactive sources are unable to cause harm. Losing a source is never a good thing to have happen – but most of the time it’s not a dire event. If you do discover a source is missing, do your best to try to find it, keep track of everything you try, report it to your regulators if you’re required to do so, and document everything. You might still get a violation, but at least your regulators will know that you’re taking the event seriously and are doing your best to make things right.