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 Post subject: Haynes 242
PostPosted: Apr 18, 2013 5:13 am 
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Hastelloy N is the standard alloy for construction of molten salt reactors, but it's current production is almost nothing.

There is another alloy, Haynes 242, which has almost identical alloy makeup, and is produced in much larger quantities for containment of hydrogen fluoride and high temperature gas turbine parts.

http://www.haynesintl.com/pdf/h3079.pdf

It is also stronger than Hastelloy N. Looks like a superiour candidate for vessel, piping and heat exchanger.


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 Post subject: Re: Haynes 242
PostPosted: Apr 18, 2013 10:43 am 
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Hastelloy-N can be made if needed. I've visited Haynes' plant in Indiana several times and toured the entire length of their production line. They're perfectly happy to make Hastelloy N for you if you're ready to buy the entire heat (10,000 lbs if I recall correctly). What they're not anxious to do is to go and make a heat for someone who only wants a small coupon or a small section. Each heat of metal they pour needs to have a firm customer before it is produced. But if you wish to be that customer they are more than happy to make it for you.


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 Post subject: Re: Haynes 242
PostPosted: Apr 18, 2013 10:49 am 
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What would be needed to prove Haynes 242 is suitable for a LFTR?

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DRJ : Engineer - NAVSEA : (Retired)


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 Post subject: Re: Haynes 242
PostPosted: Apr 18, 2013 11:09 am 
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Kirk Sorensen wrote:
Hastelloy-N can be made if needed. I've visited Haynes' plant in Indiana several times and toured the entire length of their production line. They're perfectly happy to make Hastelloy N for you if you're ready to buy the entire heat (10,000 lbs if I recall correctly). What they're not anxious to do is to go and make a heat for someone who only wants a small coupon or a small section. Each heat of metal they pour needs to have a firm customer before it is produced. But if you wish to be that customer they are more than happy to make it for you.


I don't doubt it. It's the bag-of-money idea again. Did they mention a price? If it's not too much, say $20/pound (guess) then the heat would cost 200k.

The alloy 242 appears much stronger than Hastelloy N though. This is a major advantage for heat exchangers and vessels.


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 Post subject: Re: Haynes 242
PostPosted: Apr 18, 2013 1:36 pm 
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Stuff is attractive, but cobalt activation could be a problem.

Does anyone know why there is any chrome at all in Alloy_n
when it is going to spend almost all its life in an inert environment?


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 Post subject: Re: Haynes 242
PostPosted: Apr 18, 2013 3:59 pm 
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djw1 wrote:
Stuff is attractive, but cobalt activation could be a problem.


In other liquid cooled reactors, this would be a problem, but the molten salt reactor already has such immense activity from fission products, the added difficulty seems small. Even the second loop will have a large activity from delayed neutron activation.

However, cobalt is given as max so a low or zero cobalt version could be ordered, probably at a slight reduction in high temp properties.

Quote:
Does anyone know why there is any chrome at all in Alloy_n
when it is going to spend almost all its life in an inert environment?


I've wondered about this in the past, and found a couple of answers. ORNL needed primarily oxidation resistance on the other side of the vessel and HX shells, piping, from residual oxygen and moisture in the hot cell atmosphere. The alloy also must be protected from excessive ingress of oxygen during manufacture (especially high temp treatment) and handling. Molybdenum is particularly sensitive to oxygen poisoning because of a low melting molybdenum oxide.

I've speculated that a better approach is no chromium in the alloy but chrome coating on the hot cell face. But it could be that chromium has some other metallurgical or even electronegative role to play in this environment.


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 Post subject: Re: Haynes 242
PostPosted: Apr 25, 2013 2:17 am 
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I guess that the material for any MSR would have to be a composite:-
a. Core of metal alloys to take the loads at operating temperatures.
b. A coating/enamel to handle corrosion. SiC may be suitable in some conditions.


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 Post subject: Re: Haynes 242
PostPosted: Oct 27, 2013 3:03 pm 
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I believe that clad materials have a bright future for large structural elements such as vessels and possibly pipes. Use a more common oxidation resistant base alloy and then clad with pure Ni on the salt wetted surfaces to stop Cr migration into salt. One of the obvious problems with clad and composite materials in general is the challenge of getting the clad/composite material certified for nuclear use.


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 Post subject: Re: Haynes 242
PostPosted: Oct 27, 2013 4:01 pm 
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Lindsay wrote:
I believe that clad materials have a bright future for large structural elements such as vessels and possibly pipes. Use a more common oxidation resistant base alloy and then clad with pure Ni on the salt wetted surfaces to stop Cr migration into salt. One of the obvious problems with clad and composite materials in general is the challenge of getting the clad/composite material certified for nuclear use.


This is how today's reactors are typically constructed. All LWRs use a low alloy or carbon steel as the vessel and major piping material, clad with some nuclear grade stainless steel.

One big downside is much higher fabrication and installation costs. You're basically having twice the welds, and even fully factory prefabricated liners cost a fair penny. Sometimes, if you have a reasonable cost reasonable corrosion resistant material, it may be cheaper to use the reasonable cost material rather than using a cheap material clad with something expensive. Material cost can be higher but manufacturing and installation can be cheaper. It also simplifies the safety case, since you don't get any scenario with increased corrosion from cladding failure.

ORNL's experience with stainless steel was pretty good. Probably an entire loop can be made of a high performance stainless steel like SS316H, without cladding. Corrosion could be fought with increased thickness, really not a problem for the vessel to make it 0.5 mm thicker, and it only hurts slightly in HX performance, this may be the best option yet in my opinion.

For high temperature service, there simply aren't any really cheap alloys for base material anyway. The real cheap steels aren't suitable above 400C or so (certainly not above 500C from creep strength considerations alone).


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 Post subject: Re: Haynes 242
PostPosted: Oct 29, 2013 2:49 pm 
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Using homogeneous (unclad) structural materials makes them much easier to work with; and simplicity always has value. That said it would be nice to see further work done on clad materials as they can have potential to meet more challenging conditions or more challenging combinations of conditions.

Given the use of clad materials in LWR's one would hope that the NRC are already well versed in the issues associated with clad structural materials.


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 Post subject: Re: Haynes 242
PostPosted: Oct 29, 2013 4:51 pm 
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The NRC is certainly familiar with cladding, even whole inner containments are clad (steel lined reinforced concrete) to make them leak tight. It does bring up new issues such as differential thermal expansion, liner buckling, and such, that become more serious with high temperature service.

Given the predominance of lined containments and vessels in the nuclear industry, there must be some real economical advantage to it. In the case of cheap high volume concrete structures with high quality steel liners, I can definately see it. And for a 800 ton pressure vessel, some slight materials cost savings can be had with cheaper base material steel, but it starts to get dubious here already. Say you save $5000/ton over stainless (optimistically high figure IMHO). 800 ton x 5000 = $ 4 million. This means you must fabricate and weld overlay, and then qualify and x-ray test, a stainless steel liner for substantially below $ 4 million. I don't think that can be done, certainly not or a nuclear application which has 2-10x the quality control cost of anything that workers do onsite compared to conventional projects. Even if the liner costs nothing, you've saved 4 million in a multi billion dollar powerplant. And for a relatively thinwalled low pressure vessel of a molten salt reactor? In an application where any suitable structural alloy would be expensive anyway (creep resistant alloys)? I'd have to see some cost and performance figures before being very convinced of it for this application.

If the base material offers other advantages, such as it being more creep resistant and stronger at temperature, then it starts to get more interesting. But even then a cladding may not be needed. Redox controlled molten salts are a lot less corrosive to most superalloys than hot boiling water is to carbon steel. We might simply live with the increased corrosion, considering it's really just a surface type of corrosion for most superalloys (except the ones that are really not suitable, but you don't want to use those at all, not even with a liner. What if the liner fails and you have Davis-Besse#2?).


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 Post subject: Re: Haynes 242
PostPosted: Jan 15, 2015 5:15 pm 
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I've proposed this alloy to the doctoral student and co-principle investigator of the fluoride compatibility research about to start at Georgia Tech.

Comparing 242 directly with Hastelloy-N, I notice mainly the difference in Molybdenum (+8% in 242), the Cobalt (+1.7% in 242) and the smidgeon of Boron (0.006% max).

The PI, as a material scientist has apparently been heavily warned against Cobalt in any nuclear application. However, if we can get a hold of a sample, we may be able to justify testing this material on the ground of its similarity to Hastelloy-N as well as its potential use as a solar salt.

Does anyone know the cost/availability of coupons for this alloy?


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 Post subject: Re: Haynes 242
PostPosted: Jan 15, 2015 5:58 pm 
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Hi Vince.

Cobalt is mainly there to increase erosion/galling resistance which is typically not needed for a MSR vessel. It is mainly nice for things like die pressing which I think is a use for 242 alloy. Can't be sure but you can probably specify a low cobalt amount but you'd have to buy large orders or be lucky to find a low cobalt batch.

FOB prices for the 242 alloy range from $6000 to $25000/ton depending on shape and form. This is for large orders, expect to pay some multiple for kg amounts. What shape and form do you need? I can give you a quote from Chinese suppliers, they are cheap and good, but only if you buy minimum quantity (which is 1000 kg typically).


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 Post subject: Re: Haynes 242
PostPosted: Jan 15, 2015 7:40 pm 
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Thanks for the reply, Cyril.

I was just looking for small testing samples. I don't think the budget can justify 1000 kg of anything.
The FLiNaK is already going to expensive enough, even though he plans on buying 99.9% and doing the synthesis and purification in-house.

So would there be any way to get a small sample. Let's say under a kg?


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 Post subject: Re: Haynes 242
PostPosted: Jan 16, 2015 9:11 am 
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Vince,

Talk to Haynes. In some cases (eg Haynes 230) they put a cobalt upper limit into the composition
simply because some of the ores they use contain cobalt and for most purposes it is not a detriment.
They told me they would have no problem providing low cobalt 230 using a low cobalt ore.
Suspect the same will be true for 242.

But take a long look at stainless. SUS316 does a good job of standing up to fluoride salts
and has many advantages over high nickel.

Jack


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