For anyone worried about this, the longest lived unstable isotope of oxygen (that is heavier than stable oxygen) has a half life of 26 seconds. Hydrogen can become deuterium which is stable, and finally tritium which is not.
Tritium has a long half life of 12 years, but is low energy and very easily shielded (just don't eat it).
There is very very little tritium - first you'd have to make deuterium (there isn't much), and then a deuterium would have to become a tritium, i.e. a rare event on top of a rare event.
CANDU (Canadian reactor design) is moderated via deuterium in which case there is a LOT of it circulating in the reactor core.
The heavy water is syphoned off to a tritium separation unit for recovery.
With a market value of $30,000 a gram, there is a clear incentive to recover it ;)
Some buddies who work on CANDU tell me they have tritium contamination everywhere as a result of this. From what they tell me it's not really a big safety issue, mostly more annoying than anything.
Not compltly accurate. It's true that the half-life of tritium is short compared to long lived actinides. However, like hydrogen, it diffuses very easily and it's not easy to contain. In fact, it's one of the few things emitted in the environment during normal reactor operations. As beta emitter, you are right that it's dangerous only when ingested, but it's very easy to breath of to get it from other ambient sources
> you are right that it's dangerous only when ingested
Not really. Tritium is Hydrogen. It cannot bioaccumulate. Each atom of Tritium will spread out to become one among the quadrillions of atoms of Hydrogen in our body. Most will get out of the body in a matter of days, long before they've had a chance to decay. Even when they decay, they undergo beta decay, which is not very damaging. But even if it were damaging, the damage would be very localized, it would affect at most one cell, and the immune system is easily able to handle that.
> Not really.... But even if it were damaging, the damage would be very localized, it would affect at most one cell, and the immune system is easily able to handle that.
you could not be more wrong about this. Alpha and Beta are fairly safe OUTSIDE the body. In the case of Alpha it is not able to penetrate the layer of dead skin on your hands.
Internal, it is VERY damaging because there is no "dead skin" to protect the internal organs.
"Some beta particles are capable of penetrating the skin and causing damage such as skin burns. However, as with alpha-emitters, beta-emitters are most hazardous when they are inhaled or swallowed."
I stand by what I said. Yes, beta-emitters are most hazardous when they are inside your body, if they are together and stay there for a long time. The main examples are Strontium-90 and Caesium-137. The problem with them is that they bioaccumulate. Strontium accumulates in the bones (it is chemically similar to Calcium) and Caesium in the pancreas (it's not clear why. it is chemically similar to Potasium, but it's not obvious why it should accumulate in the pancreas).
Tritium is very different. It is chemically just Hydrogen, which is present everywhere in the body. It just can't bioaccumulate.
In any case, if you don't believe me, here's a statement from the FDA regarding the tritiated water released by Fukushima:
Tritium presents an extremely low human and animal health risk if consumed and any health risk would be further minimized with the dilution effects of discharge into the ocean.
One tidbit on information damage that has stuck with me is that carcinogenic radiation damage is a second order process: to get a cancerous mutation you need both copies of DNA damaged, which would in most cases require two separate events.
To the extend this is true, it implies that it is the square of the radiation dose that determines carcinogenic effects: Half the dose would cause only a fourth of damage.
For anyone worried about this, the longest lived unstable isotope of oxygen (that is heavier than stable oxygen) has a half life of 26 seconds. Hydrogen can become deuterium which is stable, and finally tritium which is not.
Tritium has a long half life of 12 years, but is low energy and very easily shielded (just don't eat it).
There is very very little tritium - first you'd have to make deuterium (there isn't much), and then a deuterium would have to become a tritium, i.e. a rare event on top of a rare event.