> Sodium absorbing a neutron creates a strong gamma emitter with a low half time.
Isn't that a feature? Is it 24Na that decays to 24Mg in 14 hours? In case of an accident, you can run away for a week and it will magically disappear. You don't need a long term storage of the waste.
Actually this might be sodium's biggest advantage.
Everyone knows that Uranium (or Plutonium) can sustain a chain reaction: when hit with a neutron, they split in 2 or 3 lighter atoms, and 2 or 3 new (and fast) neutrons. That can be used to produce a bomb, because the fission events grow exponentially. But it's not all that useful for a reactor, where you want the number of fission events per second to stay constant in time. Which means, on average, each out of the 2 or 3 neutrons produced in a fission event, exactly one will trigger another fission event, and the remaining 1 or 2 neutrons have to find some way to disappear. Roughly speaking they can be absorbed by: 1. by some heavy nucleus like uranium 2. some control rods 3. some neutron poison introduced in the reactor on purpose, such as boron, gadolinium or hafnium, 4. the moderator, like water, or sodium in this case, 5. the walls of the containment vessel.
If you think of it, it's such a waste. Many of these options result in radioactive elements. Some result in material embrittlement.
Given that, it may very well be that sodium could be the best option out there.
There’s an argument to be made that we should do a much better job of directing those neutrons to make tritium, since fission isn’t even something to discuss until we know how to make abundant tritium.
Yes. But fusion is not quite here yet. It's a difficult business proposition to store large quantities of tritium in the hope that you'll be able to sell to an operator of a fusion reactor three decades down the road (after about 80% of it has decayed).
On the other hand, when fusion is ready for prime time, one could use liquid lithium in a reactor. Liquid lithium has quite a number of advantages over sodium: in that temperature range it has more specific heat capacity than any metal, higher even than water. It has excellent conductivity.
And if it captures a neutron, it splits in helium and tritium plus energy. It could increase the energy production of a fission reactor by more than 5%. And you get that tritium for free, and ultra-rare helium-3 if you fancy some aneutronic fusion at some point.
A half-life of a few seconds and it will probably decay before it gets near a human.
A half-life of thousands years and it will give out it's energy so slowly you will probably be more worried about it's toxicity (e.g. plutonium).
The most dangerous ones are generally those that have half-lives of days or weeks. That is long enough to get into a human body and give out a lot of it's energy. The is particularly the case for elements that are readily absorbed by the human body (such as strontium which replace calcium IIRC).
On that basis radioctivity from sodium probably isn't too much of a threat. I would be more worried about it's reactivity.
(not an expert on this, but did consultancy for the nuclear industry some time ago)
> The most dangerous ones are generally those that have half-lives of days or weeks. That is long enough to get into a human body and give out a lot of it's energy. The is particularly the case for elements that are readily absorbed by the human body (such as strontium which replace calcium IIRC).
You're mistaken, the most dangerous waste is that with half lives measured in decades, like cesium-137 or strontium-90 which both have half lives of about 30 years. That 30 year half life means that it can take centuries for the waste to decay away to safe levels. More than hot enough to kill, and with the longevity to do so for several generations. Strontium-85 and strontium-89 half half lives measured in tens of days, but after a few years you don't have to worry about those anymore. It's the isotopes like strontium-90 that are the major concern.
for that specific waste, the coolant in a water cooled reactor isn't a huge problem either. The things that are "complicated" are the fuel rods that some people refuse to be convinced we can bury in storage until reprocessing becomes necessary.
The advantage is 24Na's short (14.9 hour) half-life, not the lack of solubility in water. Half of the original radiation will be gone in 15 hours, and close to 90% in two days.
I understand half life. My point moisture currents can spread water soluble things very far very quickly.
Think of it this way, what happens if there's a catastrophic sodium leak? The winds carry it far and the Na gets into everything because it will be diluted into the wind's moisture. Won't you breath the radioactive Na from the air's moisture?
I imagine drinking only bottled water for a week, and perhaps increase the intake of salt for the same time. (Be careful if you have hypertension, it may be more dangerous the additional salt than the radiation.) Beer and salted peanuts looks like a wonderful anti-radiation plan.
If you get enough radioactive sodium salts to get covered in a dust layer, you are probably in trouble anyway. It may help that sodium is soluble an it can be washed easily.
If the small hidden sodium salts leak to water streams, my guess is that the concentration will be smaller than the natural sodium, and eating some additional non-radioactive sodium may help to remove it from inside the body even faster. Something like the potassium iodine pills.
Isn't that a feature? Is it 24Na that decays to 24Mg in 14 hours? In case of an accident, you can run away for a week and it will magically disappear. You don't need a long term storage of the waste.