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PostPosted: Nov 29, 2009 11:10 am 
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As most people here know, ORNL has been reprocessing some U-233 left over from the MSRE days.

I have been focusing my work these days on thinking about materials science aspects of handling various products both in reactors and in reprocessing schemes. Recently my 15 year old son has began to express some interest in metallurgy - though not in connection with nuclear work - and it lead me to think of hot wax casting of various Inconels, how it might work, and I came across this paper out of ORNL related to handling U(233)F6.

The issue concerned bellows delivered to ORNL that had SS welded to Inconel flanges, and obvious QA failure.

Predictably the bellows failed and an interesting analysis is carried out:

http://www.ornl.gov/~webworks/cppr/y2002/rpt/114428.pdf

I thought I'd share it with the group if anyone is interested.


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PostPosted: Nov 29, 2009 1:22 pm 
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Interesting. However this sort of test is of limited usefulness, in my opinion because performance of metal assemblies in corrosive fluid service depends on concentration, temperature, and what ever other species are present.

In some cases, for example, the formation of a protective film in high concentration environments means the assembly may survive longer than it would in a low concentration one.

I think one of the Hastalloys has pretty good all around HF resistance as well.

My advice to your son is to enter metallurgy via a grounding in general material sciences rather than any other path. The days where metallurgists could stick exclusively to their field are waining.


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PostPosted: Nov 29, 2009 8:22 pm 
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DV82XL wrote:
Interesting. However this sort of test is of limited usefulness, in my opinion because performance of metal assemblies in corrosive fluid service depends on concentration, temperature, and what ever other species are present.

In some cases, for example, the formation of a protective film in high concentration environments means the assembly may survive longer than it would in a low concentration one.

I think one of the Hastalloys has pretty good all around HF resistance as well.

My advice to your son is to enter metallurgy via a grounding in general material sciences rather than any other path. The days where metallurgists could stick exclusively to their field are waining.


I agree on the education of my son. Metallurgy is but one subset of "materials science." He's only 15 though, and however he approaches the topic is fine with me. (For the record, he's not as interested in science as in other topics.)

The problem here described at ORNL was that the supplier of bellows delivered bellows that was not fully Hastelloy where it was supposed to be fully Hastelloy. Apparently the supplier is looking into why they delivered the wrong thing. This is why it's a QA matter.

If you look at the report referenced, they did discuss the effect of temperature and composition. Actually the system was pretty simple. They had UF6, the 233 isotope, and HF generated by reaction of UF6 with water and water and not much else. at least from what I can tell.

This is the same sort of thing that would take place, by the way, isotope excepted, with the Fernald UF6, albeit on a grander scale.

When I've handled HF in the lab, we did it in polypropylene vessels. I can't really see a good conceptual reason why they can't do that either, since the system seems not to involve a lot of heat. I'm not sure though if the polypropylene is compatible with UF6 though. It works fine with HF.

They also neutralized it with NaOH and not Ca(OH)2.

I have seen recent publications that have suggested that the Fernald UF6 be used as a fluorination agent, to make HFC's for instance. Interesting approach, I think.


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PostPosted: Nov 29, 2009 9:48 pm 
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NNadir wrote:
When I've handled HF in the lab, we did it in polypropylene vessels. I can't really see a good conceptual reason why they can't do that either, since the system seems not to involve a lot of heat. I'm not sure though if the polypropylene is compatible with UF6 though. It works fine with HF..


Ya, most corrosive fluorides are dealt with with some sort of plastic these days, up to some rather impressive temperatures too if you can use Teflon, but for the time being its still going to have to be metal for high pressure or very high temp situations.

Generally however, just hanging a sample of a component into a solution, is a poor way to judge overall performance of the item in service.


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PostPosted: Nov 29, 2009 10:48 pm 
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DV82XL wrote:
NNadir wrote:
When I've handled HF in the lab, we did it in polypropylene vessels. I can't really see a good conceptual reason why they can't do that either, since the system seems not to involve a lot of heat. I'm not sure though if the polypropylene is compatible with UF6 though. It works fine with HF..


Ya, most corrosive fluorides are dealt with with some sort of plastic these days, up to some rather impressive temperatures too if you can use Teflon, but for the time being its still going to have to be metal for high pressure or very high temp situations.

Generally however, just hanging a sample of a component into a solution, is a poor way to judge overall performance of the item in service.


It depends on what the service is.

I like simple experiments that are fast and cheap.

I personally wish that teflon accessible temperatures were more impressive than they are. One can make Teflon decompose on an ordinary kitchen electric stove and kill one's parakeet in the process. Happens all the time.


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PostPosted: Nov 29, 2009 11:57 pm 
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NNadir wrote:
It depends on what the service is.

I like simple experiments that are fast and cheap.


They're a good starting point, but in the end you have to deal with a of other things in a valve, like flow and cavitation that can change attack rates; the stuff engineers have to worry about.

NNadir wrote:
I personally wish that teflon accessible temperatures were more impressive than they are. One can make Teflon decompose on an ordinary kitchen electric stove and kill one's parakeet in the process. Happens all the time.


True 250C isn't much but its better than nothing, hopefully there is something better in the works.


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