Radioactive Strontium in Bones 11/21/19

Biochemistry post by Richard Bleil

Back in 1986, I was working as an analytical chemist. Although I personally did not go, I was working with a company that became part of an international investigative team to try to discover what had went wrong that caused Chernobyl to blow. For those who don’t remember, Chernobyl was the first full-scale nuclear meltdown of a power plant in history. It was one of the worst nuclear disasters, and considered in many ways to be worse than the Fukushima disaster. As it turns out, experts believe that the absolute worst nuclear disaster was Three Mile Island, right here in the US in 1979. All the citizens were told was that it “vented radioactive steam”, and to this day little is known about it save that warning lights had been flashing for several weeks but went unnoticed because they were covered by inspection tags. In Chernobyl, a state-mandated test emergency shutdown had been successfully executed, but it was not coming back online as quickly as hoped (that is, as planned by the government), so they began turning off the fail-safes to speed up the process.

By the time the disaster occurred, almost all of the safety systems had been turned off. The plant began heating out of control leading to the meltdown. To make matters worse, at the core of the plant was a 1,700 ton carbon core which caught on fire and burned for years, generating so much heat that emergency crews couldn’t get close enough to do anything about it. In the meltdown, radioactive Strontium-90 was spewed into the atmosphere, making the city and surrounding countryside radioactive. Even today, the area is considered uninhabitable.

One common thread among the victims of the nuclear accident is the discovery of Strontium-90 in their bones. On the periodic chart, strontium is found just below calcium. It’s in the same column, meaning it’s the same family (the “Alkali Earth Metals”). Because they are in the same family, they have very similar chemical characteristics, and as it turns out, biological organisms cannot tell the difference between a calcium ion and a strontium ion.

So, the strontium is released into the atmosphere. It ends up in the soil, where it is absorbed by plants. Cows eat these plants, and absorb the strontium and produce strontium laced milk. (By the way, milk is not white because of the calcium. This is a misperception because milk is high in calcium and chalk, calcium carbonate, is a white mineral. In fact, milk contains a protein called “casein” in high concentrations. Casien is a white protein. Calcium, when dissolved, is colorless and clear. It’s the casein protein that makes the milk white.) The humans drink the strontium laced milk and absorb the strontium. The human body uses calcium for bone strength and growth, and because it cannot distinguish between calcium and strontium, the strontium ends up in human bones.

Radioactive bones. So the victims expose themselves to radiation from the inside out. Strontium-90 decays via beta emissions (high energy electrons) to form yttrium-90, which further decays via beta emissions to form zircon-90 which is stable. Beta radiation is moderately strong (alpha radiation is the weakest and can be stopped with a piece of paper, while gamma radiation is the strongest requiring thick lead to block like the bib your dentist puts on you for x-rays while telling you that it’s perfectly safe just before leaving the room and hiding behind a lead wall). It causes burn damage to tissue, so to have beta emitting from your bones will burn the tissue of surrounding organs.

Today, thirty years later, Mother Russia is permitting some approved small groups into the forbidden zone around Chernobyl. They always carry Geiger counters with them and the tour guides know where the radiation levels are moderately safe for short term exposure. This is why periodically you will see specials or photographs from the abandoned city of Chernobyl and the surrounding area. With a half-life of 28.8 years, any strontium-90 in the area is about half of the original concentration at the time of release. Yttrium-90 has a half-life of about 64 hours, so it decays rapidly relative to Strontium-90. In another 30 years (roughly 2040), the Strontium-90 will still be present; only half of what is there today will decay in the next thirty years. This means that by 2030, the Strontium-90 concentration will be roughly 1/4 of what it was at the time of release. By 2070, it will have decayed to about 1/8 the original concentration.


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