Zirconium in nuclear waste

[dgjxqz]

Zirconium from fission product cannot be safely used as it contains ⁹³Zr which is radioactive. However, zirconium is also used for fuel cladding and building some other parts of a reactor, which is already a radioactive environment thus its own radioactivity is no longer a concern.
So, is it possible to economically extract zirconium from nuclear waste for something useful rather than burying it?

 

[phyzguy]

Is it possible to extract zirconium from nuclear waste - I'm sure it is possible.
Is it cheaper to produce zirconium this way than simply mining zirconium - almost certainly not.

 

[.Scott]

I think the major problem would be in the handling of the radioactive waste.
The other is that the neutron cross-section of Zr-92 is very low, which is why it is used. I don't know if Zr-93 shares that characteristic.

Aside from that, more that 5% of the waste is Zirconium-93 - and it is likely to be in a largely unoxidized form. So the chemistry for removing Zr from the waste should be easier than it is from ore. Also, if you wait a few months, the unstable isotopes remaining will be Zr-93 and Zr-95.

 

[.Scott]

Here are the cross-section tables for Zr-92 and Zr-93.

https://wwwndc.jaea.go.jp/cgi-bin/Tab80WWW.cgi?lib=J40&iso=Zr092
https://wwwndc.jaea.go.jp/cgi-bin/Tab80WWW.cgi?lib=J40&iso=Zr093

They are similar, but with many small (10%-ish) differences.
Perhaps someone familiar with reactor design could comment on which would be better - or if the differences are significant.

 

[Rive]

However, zirconium is also used for fuel cladding and building some other parts of a reactor, which is already a radioactive environment thus its own radioactivity is no longer a concern.

It is a big enough problem already that the used fuel is radioactive: nobody needs unused fuel which is radioactive. So, it is a concern.
I don't know how radioactive ⁹³Zr is. What I'm saying is just that the radioactivity of the input side does matters.

 

[nikkkom]

However, zirconium is also used for fuel cladding and building some other parts of a reactor, which is already a radioactive environment thus its own radioactivity is no longer a concern.

Just imagine the complications and associated costs of using contaminated Zr in a production of fuel cladding. All the production equipment becomes contaminated. What joy.

And the resulting fuel bundles now are radioactive and the rules for their handling are much more restrictive.

 

[nikkkom]

Aside from that, more that 5% of the waste is Zirconium-93 - and it is likely to be in a largely unoxidized form. So the chemistry for removing Zr from the waste should be easier than it is from ore.

Chemistry per se may be somewhat easy, but nuclear waste (after U and Pu removal) has radioactivity on the order of ~1 million R/h.

Doing anything with it is VERY expensive, that's why usually nothing is done with it. In US, nuclear industry even went with the route "we won't even bother with U/Pu removal step, let's just keep spent fuel securely stored in heavily shielded containers for now", and it makes economic sense.

 

[Astronuc]

Zirconium from fission product cannot be safely used as it contains ⁹³Zr which is radioactive. However, zirconium is also used for fuel cladding and building some other parts of a reactor, which is already a radioactive environment thus its own radioactivity is no longer a concern.
So, is it possible to economically extract zirconium from nuclear waste for something useful rather than burying it?

The fission yield of Zr-93 is very low, on the order of 1E-6. The yield of Zr-95, from thermal fission of U-235 is on the order of 0.06.

The half-life of Zr-93 is 1.6E6 years, so it would not be very radioactive. Recovery would require reprocessing of the spent fuel, which means dealing with all the other radionuclides. It would be more practical to use the irradiated Zr to combine with other radionuclides for final disposal.

Natural Zr is 0.5415 Zr-90, 0.1122 Zr-91, 0.1715 Zr-92, 0.1737 Zr-94 and 0.028 Zr-96.

Fuel assemblies use Zr-alloys for fuel rod cladding and endplugs, water rods (BWRs) or guide tubes (PWRs), spacer grids, and channels (BWRs). The Zr-alloys include Zircaloy-2 (BWRs), Zircaloy-4 (PWRs, and non-fuel components in BWRs), and more recently Zr-1Sn-0.6-1.0Nb-0.1-0.35 Fe or Zr-1Nb, where the coefficients represent wt%, with Zr being the balance. The compositions are tightly controlled, so beside the radioactivity, recycling irradiated Zr-alloys would be problematic, since some of the alloying elements become activated and would have to be separated and disposed in a manner similar to spent fuel.