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Dan Vizine
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Disposal of Na from a breeder reactor
In an unusual twist, I've taken on a consulting role for a company who was awarded a government contract to dispose of steel drums which were used to
drain the sodium coolant fluid from an early breeder reactor. The drums were subsequently re-heated and the sodium was poured out. From 2 to 5 pounds
of sodium remained in the drum as a "heel". The drums were inerted and stored ~ 50 years ago.
The drums have developed a rust-coated surface. The proposed method of destruction that they plan on is compaction of the drums to a height of 6 or 8
inches, after that I don't have a clue. I have no need to know.
The concerns they'd like me to address include a thermodynamic analysis (easy) of the redox couple (rust & Na), a literature search (I have some
limitations), laboratory simulations of potential initiating incidents (the fun part) and a general hazard analysis.
Anybody who has ever looked at Goldschmidt reactions will remember that the fuel metal needs to very active and should possess a high enough bp to not
boil away from the reaction site. Thus, sodium is not usually considered for a smooth thermite reaction. But we're not concerned with a smooth
reaction, just whether or not one will occur at all.
The thermodynamics say this will be a spontaneous reaction. But whether it actually happens requires empirical data. Yesterday, I decided to try and
make a mixture of a stoichiometric amount of sodium and Fe2O3 using molten sodium. The idea was to make a intimate mixture of reactants, similar to Al
thermite, without trying to (powder?!) sodium or resort to making sodium sand. The molten sodium was contained in an argon-inerted 2 inch diameter
borosilicate test tube at ~ 130 C. The rust was added in portions, swirling vigorously in between additions. The sodium, as I feared, showed little
tendency to adhere to the oxide. I allowed the tube to cool until the argon-blanketed mixture started to stiffen ever so slightly. My plan was to then
gently mash the reactants together with a porcelain pestle.
Poof! That's all it took. Within a fraction of a second the mixture ignited and went pretty much to completion. Well, at least very little Fe2O3
powder was left. The reaction nuggets were magnetic.
Now that it is obvious that drum compaction, if molten sodium were present, could start a metallothermic reduction. How would molten sodium possibly
be present? Interaction with water. I was told that the drums may be wet. But wet how? No info.
The problem is now reduced to something that a few observations could have resolved (if they were made, which they weren't). Is there water? If so,
where? On the drum tops? Clinging to the inside drum walls? What does the sodium look like? Still solid? Liquid? In-between?
Does anyone have any experience that may be applicable? Personally, after 50 years, I feel that a boatload of moisture could have diffused in. I'd bet
that the top layer of sodium is now concentrated NaOH solution. The sodium layer is only about a half inch deep. I've seen sodium metal that remains
protected for decades with a layer of NaOH on top. What condition do you think the sodium would be in? Any real world experiences would be useful.
Thanks.
PS. No application of pressure has yet been able to cause ignition. I've tried 12 tons of pressure exerted slowly by a hydraulic press, a jig I built
that delivers reproducible 40 joule impacts via a SS rod, and (after 40 joules was not enough), I tried a sledge hammer at full force. Nothing.
[Edited on 2/19/2017 by Dan Vizine]
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Sulaiman
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Well at least all of the Na24 (the nasty one) should have decayed and almost all of the Na22, so no radioactivity problems.
CAUTION : Hobby Chemist, not Professional or even Amateur
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wg48
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Well you may want to pad out your report with various analyses but in the final analysis a steel drum with an unknown amount of sodium metal and or
sodium hydroxide/ carbonate solution in it cannot be crushed safely to a safe compact. Safe with the meaning used in US or UK industry. The sodium and
or caustic solution could be extruded/expelled during the crushing and you could left with a vary nasty compact that may still contain/contaminated
with sodium/caustic solution that is leaking. The crushing machine could be contaminated with sodium/caustic and then by water when the next drum is
crushed. Then you are still left with the problem of safely transporting and disposal of the compact with perhaps extruded sodium sticking out of it .
I suggest you recommend neutralising sodium or its reaction products and washing out the drum prior crushing it. I just thought the drum could
contain hydrogen/air mixture.
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Dan Vizine
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Sulaiman,
Absolutely correct, it has been an awful lot of half-lives.
wg48,
My thoughts exactly. I mentioned that, but they'd rather not for reasons that weren't explained to me. That's the industry standard for this
situation. They have other plans for disposal and liquids aren't desirable if they can be avoided.
As the sodium is in a 1/2 " layer and compaction to the desired height leaves ample un-compacted space, extrusion is not a huge concern. When new
drums are crushed similarly, the metal does not split or rip. But these drums are 50 years old.
Reading between the lines, maybe there still is a radioactivity concern. Otherwise, a cheaper, easier route would be taken I would guess. I am under
the impression that the drum crusher will be consigned to waste also. Contamination of some kind seems inevitable.
Full scale drum crushing tests with new sodium (they bought 300 pounds) are the next phase of their work (once I'm done in 4 weeks).
[Edited on 2/19/2017 by Dan Vizine]
"All Your Children Are Poor Unfortunate Victims of Lies You Believe, a Plague Upon Your Ignorance that Keeps the Youth from the Truth They
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unionised
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Among the issues I'd worry about would be the possibility of sodium peroxide formation too.
It may sound daft, but I'd start off by making sure that the process started off with a lot of water.
After that you would have hydrogen, scrap steel and dilute caustic.
You would convert an unknown hazard into well documented ones.
Obviously the dunk tank would need to be pretty much "remotely operated"; you certainly can't have anyone near it.
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Dan Vizine
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Hi Unionized,
Thanks for the post.
But here I guess I should reiterate the fact that it seems clear that the normal route of hydrolysis is not desirable.
In fact, to make a a few conclusions based on observations:
1) If some sort of residual radioactivity wasn't present, this entire project wouldn't exist, because otherwise it would just be a routine
chemically-contaminated drum operation
2) They just bought 300 pounds of Na for full scale testing of drum compaction. That this process is to meant to proceed with the residual sodium in
place is pretty clear. The entire project is written around it.
They have specified that inert gas and application of "asphyxiating silicate based soil cover" are on the table for hazard mitigation.
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unionised
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Fine, but Sulaiman's point still holds- you can't do this on a conventional crushing rig.
You need to assume that, at some point, there will be a sodium fire.
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Dan Vizine
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I think it's fair to say that the possibility of a sodium fire is only real if the drum splits on compacting.
IF the drum stays intact, I think the likely scenario is that, after opening and inerting and as compaction starts, any residual water on the drum
head may fall inward. In any rational world, this amount should be fairly small. This is because they have to open to inert with gas and the
asphyxiating agent (I think both should be used) and so any standing water would be removed already. The inward-falling water should not be capable of
starting a fire under these inert conditions. Aerosols of sodium hydroxide with some oxide and some peroxide wouldn't be surprising.
The full scale drum crushing experiments should suggest an answer as to drum integrity. But, with 50 year old drums, a lot of things are possible.
Perhaps the bottoms are fairly rusty and will split. I would like to say the full scale tests would be done on representative drums, but no pictures
are available. So, who knows?
Given the uncertainties, a fire or a number of external fires are not impossible.
Given the low caloric output of sodium fires (similar to an equal volume of wood) they are not horrible, but precautions will need to be in place.
The crusher isn't exactly a normal unit in that its lifetime is measured in hundreds of drums, then it will be waste, too.
Thanks for these comments. They are just what I hoped for.
[Edited on 2/19/2017 by Dan Vizine]
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phlogiston
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If the possibility of radioactive contamination is real then a sodium fire may be a more serious concern than it would normally be, as it could
disperse radioactive material.
It sounds like proposing an alternative approach is not part of your job, but how about enclosing the drums in bigger drums that are guaranteed by
design to not split open upon compaction? It would prevent a number of the mentioned issues. Mainly, it would remove any uncertainties related to how
the old drums will behave.
Also, if you could pierce the old drum after you put it in the new one and apply a vacuum for a while, you may be able to evaporate water that got
into the old drum.
-----
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unionised
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I'd agree- the fire isn't a massive problem- just let it burn out.
But the ash is caustic. If the ash is radioactive caustic then you have a big problem- essentially you need to enclose the whole lot and put filtered
ventilation in place.
Something like this, but run underwater would be another option
http://www.untha.com/en/applications/metals_a11
OK you get nasty caustic waste water- but whatever you use you will presumably need to wash it down afterwards.
And it's cool to watch anyway :-)
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j_sum1
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Interesting problem. I am really not sure why they want to crush while keeping the Na in metallic form. It would seem much more sensible to me to
convert to an inert salt of some kind or even to let it oxidise in air. I understand the desire to avoid large quantities of liquids but surely there
is a feasible method.
What are they going to do with the crushed leaky drums containing both rust and metallic sodium - with presumably some radiation hazard as well? That
would seem to me to be more of a hazard than the (semi) intact drums.
Is there any possibility of adding something to the drums before crushing? I am thinking of something like powdered alumina to dilute the contents
and lessen the chance of an uncontrolled reaction.
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Dan Vizine
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And then there's the question of what happens inside the compacts once the remaining argon diffuses out and any water settles. This is still a dynamic
system in a sense.
The lack of details baffles me. With a little bit of data this analysis could be so much more useful to them. Maybe I'm just a useful component to
them having secured the contract, but I get a feeling it runs deeper. If they had data, I'm sure they'd share it. As mentioned earlier, they couldn't
supply arguably the single most useful piece of easily collected data, a few pictures. They haven't actually seen the drums! Is that how jobs are put
out to bid? Without supplying any data to facilitate that which you want to accomplish?
Mine is not to reason why, I guess.
Again, and I have no evidence this is true, but I believe the goal is to avoid liquids at all costs. Notice that the only suppression agents allowed
are a gas and a solid? I think that the planned fate of the compacts may not be compatible with liquid waste.
It may well be that the compactor is situated within an area like a large fume hood. If we assume radioactive dust/spray is in the mix, really, how
could it be any other way?
[Edited on 2/19/2017 by Dan Vizine]
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Dan Vizine
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I located an IAEA paper which expanded on the radiological possibilities for the sodium.
As we all seem to be aware, the initially produced Na-24 will have experienced almost 30,000 half-lives in the past 50 years and has long since
decayed to magnesium.
Here is where the rest of the concern lies:
There are several sources of radioactivity in bulk Na or NaK from primary circuits:
− Activation of sodium and potassium by neutrons in the reactor core; 22Na and 40K are
the main generated radionuclides;
− Contamination by actinides and fission products due to initial surface contamination of
fresh fuel by fissionable material, fuel cladding failures during operation, or use of
leaking fuel pins. Typical actinide contaminants are Pu, Am, Cm and U isotopes; the
most common fission products are isotopes of caesium. Tritium is also present;
− Contamination by activated corrosion products from fuel cladding and primary circuit
structures, such as 54Mn and 60Co.
Small wonder that this very high purity sodium metal is not suitable for re-use.
PS. Talk about luck!! A reference had this to say about the very barrels in question, and included a picture(!!):
All of the drained sodium barrels located at
the INL’s Materials and Fuels Complex (MFC)
are known to contain less than 5 lbs (2.25 kg) of
residual sodium metal, which is below the 10-lb
threshold above which the barrels would be
regulated under the Resource Conservation
Recovery Act (RCRA) statues. The exact
amount of residual sodium in each barrel is
unknown, however, because the barrels also
contain a mixture of sodium oxides, sodium
hydroxides, and sodium carbonates. Over time,
air and water has leaked into the barrels to react
some of the residual sodium and convert it into
these other materials. Figure 1 shows a
photograph of the inside of one of the 1400 drained
barrels.
and
Additionally, the barrels are considered low
level radioactive waste because of their origin
and measurable radioactive content and must be
disposed according to the waste acceptance
criteria for the Radioactive Waste Management
Complex (RWMC) in southeastern Idaho or
other equivalent facility.
[Edited on 2/20/2017 by Dan Vizine]
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Magpie
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I presume that the final crushed drums should be free of elemental sodium and also be chemically unreactive with the atmosphere and any water
intrusion. To reach this state I would take off the drum lids and promote the burning of all residual sodium. This should be done in a HEPA
protected fume hood, remotely.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Dan Vizine
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No, Magpie, that isn't it....
The parameters of the disposal are seemingly set. I wasn't asked to comment on a recommended route. I was asked for a risk assessment of the intended
method of compacting the drums without any pre-treatment. I can't guess the intention after that, although I'd assume burial. But, it's neither here
nor there for my purposes. My task ends with a crushed drum, not on fire.
I think the paper that I found today is the answer I was searching for. There are analyses of 5 or 6 different drums and a picture. The sodium isn't
present as aqueous NaOH overlaying a sheet of sodium, it's more lumpy. I haven't read why yet....
But, beyond any doubt, there is a substantial amount of elemental sodium left.
PS. Not trying to be evasive about the paper, but this job came with a confidentiality statement and so I'd rather not identify the exact reactor. The
problem as stated could be any LMFBR and, of course, the company name wasn't given.
A couple well-worked-out wet methods exist. They hydrolyze to NaOH, concentrate it to 70% and when it cools it's suitable to bury. A refinement uses
carbon dioxide to arrive at the carbonate.
[Edited on 2/20/2017 by Dan Vizine]
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j_sum1
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Well, I think I share with Magpie and others a general unease that this is not the optimum treatment option. Common sense suggests rendering the
material as inert as possible in every sense of the word inert. And leaving the sodium in its elemental form in damaged vessels flies in the face of
that.
But, as you say, all this is out of your hands. The question remains open as to whether solid Na will react with iron oxides during the crushing
process. Now that you know a bit more about the drums, is it possible to do a mock up with a rusted tin can, a bit of sodium and a hydraulic press?
And dang... I nearly weep for 1400 drums each with a few pounds of elemental sodium being disposed of.
[edit] typo
[Edited on 21-2-2017 by j_sum1]
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Texium
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That's pretty
much all I've been thinking of as I've been following this thread. I mean, I'd take it, even if it was still slightly radioactive...
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wg48
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Wow, In total over two tons of hot sodium buried in the ground !!!
I guess at some point hydrogen will be ecaping from the top soil. Could be a big suprise for someone lighting a campfire there one day.
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MrHomeScientist
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Do we know what the purpose of crushing the barrels is? It introduces so many risks and hazards it seems like it's not worth it just to save a little
space in storage. Your initial testing certainly seems to indicate that pressing on a mix of sodium and rust is a bad idea.
Very unique problem, Dan. You have a pretty interesting job!
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Endo
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The super-compactor (hydraulic drum crusher) at the INL is located at the Advanced Mixed waste treatment plant (AMWTP) facility. I don't believe that
they are currently outfitted to work with inert gas blankets. Typically crushed drums (Pucks) are loaded into 100 gallon drums and bagged with a
filtered bag, The drum is lidded and a drum vent is installed into the 3/4 inch bung on top of the drum to prevent the container from building up gas
pressure.
I don't see how this waste would ever be legal to ship on a public highway, with the RCRA codes for reactivity and corrosives, as well as the
potential for hydrogen/flammable gas generation they would be able to do little except continue to store it onsite albeit with a smaller space
footprint.
Good luck!
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Dan Vizine
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Quote: Originally posted by MrHomeScientist  | Do we know what the purpose of crushing the barrels is? It introduces so many risks and hazards it seems like it's not worth it just to save a little
space in storage. Your initial testing certainly seems to indicate that pressing on a mix of sodium and rust is a bad idea.
Very unique problem, Dan. You have a pretty interesting job! |
I wondered the same thing. And then I found out it was 77,000 gals of sodium in 1,400 drums packed 80 to a cargo container. That's 18 cargo
containers. It would seem that that could be reduced to 5.
It doesn't seem reasonable that it could be buried like that.
I don't mean to sound like this is normal work for me. It just came out of the blue, probably once in a lifetime.
I also got confirmation that the radioactivity is very low. If it weren't reactive, it could be buried in Idaho as radioactive non-hazardous waste.
[Edited on 2/21/2017 by Dan Vizine]
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wg48
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77,000 gallons of warm (radioactive) sodium is considered “none hazardous" ... That’s a definition I have not come across before.
A lot more than a few pounds per barrel then.
Its not that long ago they would have opened the barrels and dumped them at sea. I think we (EU and US) don't do that anymore.
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Texium
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With the rising acidity of the world's oceans, it probably wouldn't hurt 
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j_sum1
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Here is how it used to be done. But apparently we now just crush and bury. I wonder if it is a significant improvement.
https://www.youtube.com/watch?v=HY7mTCMvpEM
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Fulmen
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I think the risks of a redox ( Goldschmidt) reaction between Na and iron oxide are quite real. I worked at a magnesium plant once, and we handled a
fair bit of scrap for recycling. We had at least one explosion/fire from this during unloading. Our makeshift test was to collect a sample of dust and
drop a glowing nut into it.
We're not banging rocks together here. We know how to put a man back together.
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