Energy From Thorium Discussion Forum

Continuing from a different thread at viewtopic.php?f=3&t=4197&p=55577#p55589

Further on the subject of MSR vessel & HX materials for chloride salts, as mentioned previously, this is being developed for pyroprocessing equipment in both the US and S. Korea (and possibly other countries as well).
Here is an excerpt from an excellent reference posted here: http://www.if.uidaho.edu/~vutgikar/Fall2010/SNF/Lecture11.pdf

Pyroprocessing Lecture 11, 11/08/2010

Cathode Processor Crucible
Challenge
To Find a Material/Coating Compatible with Reactive Chloride Salts, Molten Uranium, and Harsh Thermal Environment (up to 1300 C)

Slide 13:
Cathode Processor Crucible Development
HfN-coated Nb crucible:
Several tests with irradiated products have shown minimal signs of reaction.

The neutronic properties of these materials - especially the bulk Nb wall plate - look acceptable in the fast spectrum.

One wonders if this hafnium nitride will stay on in a neutron flux if you're thinking of a vessel/primary loop application.

With sufficient redox control, Nb should be fine (even uncoated) as a reactor vessel and primary loop material. Tests would have to be done to check this.

Niobium has the advantage over most competing materials such as molybdenum, that it is ductile and easy to form.

Yes, the formation of helium inside the HfN could be a problem in a thick layer.
If it's just a thin layer -- implanted ions ? -- maybe it would last a long time.
Even better if clean Nb works.... maybe a function of temperature ?

If its thin it could also be abraded off or not be protective enough to be bothered with (the HfN has a certain porosity).

Nb corrosion in halides shouldn't be much of a function of temperature. This is because it is a pure element (not sensitive to diffusion of more vulnerable elements in an alloy). It should be largely a function of redox state. Excess chlorine easily corrodes niobium. Without an excess, the niobium chloride can't form.

In the application of a crucible carrying all sorts of chlorides, an oxidative environment can exist, so naked niobium is likely out of the question.

With Nb, it is important to prevent large amounts of oxygen/water in the melt from building up, though that is true for any alloy.

niobium suffers from enbrittlement if hard neutron spectrum, just like molybdenum for that matter, Tungsten on the hand does not.

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