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PostPosted: Apr 02, 2010 5:07 pm 
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Lars wrote:
... any hot element from the far left or far right of the periodic table (excluding nobles) will be very reactive and will simply refuse to be elemental - it will combine with something.


Sodium's inertness to iron, uranium, and plutonium is a notable exception. http://www.fas.org/sgp/othergov/doe/lan ... 321482.pdf lumps all plutonium-alkali metal systems together in its entry for plutonium-cesium, which pair it say doesn't react, so probably it's also inert to lithium. Or anyway there's a chance. Like many a first-row element ... OK, like six or seven of them, it is much less similar to its heavier relatives than they are to each other.

The article about the 15-coordinate thorium says it is "stabilized", which has been imaginatively rendered here as "stable". What's truly stable are compounds such as thorium tetraboride, thorium hexaboride, and thorium nitride. A very little heat put into Th(alphabet soup)4 will trigger a highly exothermic decomposition into boride, nitride, and carbide of the metal, with the many hydrogens going free as H2.

Unless the stuff were dunked in lithium, which would provide loads of additional heat by combining with the hydrogen. (Lithium also combines exothermically with boron, cf. Mechanism of reaction synthesis of Li-B alloys, LIU Zhijian et al., Science in China Series E Vol. 46 no. 4, so if any of that were left over, that's probably what would happen to it.)

(How fire can be domesticated)


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PostPosted: Apr 03, 2010 12:38 am 
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If you mean to use liquid Li as your carrier fluid rather than H20 you would reduce confusion if it wasn't in a section titled aqueous.


Yes, that is confusing. When you start off with one type of system and describe many fundamental changes to it, at some point it turns into something else; something completely different.

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I'm not much of a chemist but I imagine any hot element from the far left or far right of the periodic table (excluding nobles) will be very reactive and will simply refuse to be elemental - it will combine with something.


I don’t think it matters if many lithium compounds form as lithium combines with waste products of the nuclear reaction inside the reactor vessel. Lithium will be easily dislodged when the waste is processed. What you said is true as follows:

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Combining lithium and fluorine makes for a very strong ionic bond and these two would rather be with each other than anything else.


Adding some fluorine during waste processing will clean out lithium from all the waste compounds.

IMHO, processing the waste stream from the Lithium Homogeneous Reactor (LHR) will be identical to the Lftr.

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The corrosion problem I think you must be referring to is tellerium granular attack. It will take a bit more R&D money to prove the results but ORNL made good progress and seemed confident of a resolution. The Russians and French both seem confident that this can be solved. The solution involves making small changes to the minor constituents of the Hastalloy-N. It represents virtually no production cost - just some R&D expense up front.


Iron is far cheaper than Hastalloy-N. Yes, Hastalloy-N will work but it is more prone to helium (alpha particles) damage than iron is. Iron can tolerate far more atomic displacements than Hastalloy-N can. By comparison, Nickel is not strong in that respect.

It is better and cheaper to use iron instead of Hastalloy-N if the chemistry of the reactor permits it. Iron or some alloy of it is simpler to manufacture and cheaper to buy.

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PostPosted: Apr 03, 2010 1:00 am 
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GRLCowan wrote:
Lars wrote:
... any hot element from the far left or far right of the periodic table (excluding nobles) will be very reactive and will simply refuse to be elemental - it will combine with something.


Sodium's inertness to iron, uranium, and plutonium is a notable exception. http://www.fas.org/sgp/othergov/doe/lan ... 321482.pdf lumps all plutonium-alkali metal systems together in its entry for plutonium-cesium, which pair it say doesn't react, so probably it's also inert to lithium. Or anyway there's a chance. Like many a first-row element ... OK, like six or seven of them, it is much less similar to its heavier relatives than they are to each other.

The article about the 15-coordinate thorium says it is "stabilized", which has been imaginatively rendered here as "stable". What's truly stable are compounds such as thorium tetraboride, thorium hexaboride, and thorium nitride. A very little heat put into Th(alphabet soup)4 will trigger a highly exothermic decomposition into boride, nitride, and carbide of the metal, with the many hydrogens going free as H2.

Unless the stuff were dunked in lithium, which would provide loads of additional heat by combining with the hydrogen. (Lithium also combines exothermically with boron, cf. Mechanism of reaction synthesis of Li-B alloys, LIU Zhijian et al., Science in China Series E Vol. 46 no. 4, so if any of that were left over, that's probably what would happen to it.)

(How fire can be domesticated)


Reference:

http://www-pub.iaea.org/mtcd/meetings/P ... orokin.pdf

1. The reference (Liquid metal coolants technology for fast reactors) is an evaluation of all the candidate liquid metal coolants for a fast reactor. I think lithium held up well in this trade study. Take away: Lithium is not as chemically reactive as Na or K.

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PostPosted: Apr 03, 2010 8:59 am 
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We need to split this thread off from the Aqueous thread. Axil, PM me and tell me the post where you want to split it, what you want the title to be, and what part of the forum you want it in.


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PostPosted: Apr 04, 2010 1:02 pm 
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Liquid lithium will also put one on alert! Another alkali metal, Sodium, has given a bad name to fast reactors. Liquid lithium or a hydride would be risky of fire hazard, to say the least. It is the low cost and safety of water that makes thermal reactors worthwhile, with uranium enrichment and once through profligate use of that enriched uranium. With the fast reactor's disadvantage of fire prone materials in the core, it is a big no-no.
Let the fluid fuel reactor be aqueous even if not homogeneous. High pressures are really bad but not as bad as fire-prone alkali metals. Even after granting their compatibility with metals. The water also has the advantage of providing steam for heat transfer and the medium on the turbine prime mover. A less reactive metal like lead could be more acceptable.
There is a separate thread on eutectic metal core reactors:-
viewtopic.php?f=2&t=1678


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PostPosted: Apr 04, 2010 2:58 pm 
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Kirk Sorensen wrote:
We need to split this thread off from the Aqueous thread. Axil, PM me and tell me the post where you want to split it, what you want the title to be, and what part of the forum you want it in.
(Kirk, please post this wherever the Lithium Homog. Rx thread winds up – thanks.)

To All Interested,

It is thermodynamically highly unlikely in the presence of free lithium metal for any hydride or deuteride (other than LiH of LiD) to be stable above 500C.

Thus, the complex hydride Thorium Aminodiboranate, Th(H3BNMe2BH3)4, has very little chance of being chemically stable, let along soluble, in hot Lithium. Easy kinetics (easiest initial reactions) with molten Li metal are:
Li atoms inserting in the polar N- / B+ bonds, then tearing C-N bonds apart to 1st make Li2C2 + Li3N. These two comp's next promptly disproportionate to Li2CN2 (Li Cyanamide) + free Li (figured out the latter while I worked on the Lithium MK50 Torpedowith Honeywell).

These fast first reactions are not the end products, however. The most thermodynamically-stable rearrangement products from putting (Th+4){[(H3B)2N(CH3)2)]-}4 with an excess of Li metal at ~500C+ are as follows:

• 48 moles of LiH. The *high* solubility of liquid Lithium Hydride in molten Li helps further favor its already-exothermic formation and *greatly* lower the partial pressure of H2 gas that's in equilibrium with the dissolved LiH. Li Deuteride in lithium should have even lower partial pressures than LiH.

• 1 mol ThN, the most stable nitride in this system (comparable if not even more stable than TiN or ZrN)

• 3 mol BN (mostly the hexagonal variety, like graphite)

• 5/6 mol "Li7B6," an intermetallic forming from the B not tied up as BN (For more on B's exothermic reactions w Li, see this paper's Conclusions)

• 4 mol Li2C2, Lithium acetylide (like MgC2 or CaC2, reaction w H2O forms acetylene gas). Acetylides form when carbon contacts hot (molten not necessary) Li, Mg, Ca, Sr, or Ba metal, but *not* with molten Na, K, Rb or Cs.

Even though molten Li is *much safer* than Sodium and even safer than Mg re. vapor pressure, flame temps & extinguishment, and although ThN, BN and Li boride & acetylide (unlike Li3N & LiH) are *insoluble* in Li, all non-fluoride fluid chemistries *LACK* a good method for transferring freshly-bred U233 to the Core.

With Fluoride-based Blankets, Fluorination easily moves U233 to the Core, and without any need to reduce the plant's power output by a single Iota. Pretty cool property possessed by Fluorides and LACKED by all liquid metals, including Bi & Pb!!

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PostPosted: Apr 04, 2010 3:40 pm 
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jagdish wrote:
Liquid lithium will also put one on alert! Another alkali metal, Sodium, has given a bad name to fast reactors. Liquid lithium or a hydride would be risky of fire hazard, to say the least. It is the low cost and safety of water that makes thermal reactors worthwhile, with uranium enrichment and once through profligate use of that enriched uranium. With the fast reactor's disadvantage of fire prone materials in the core, it is a big no-no.
Let the fluid fuel reactor be aqueous even if not homogeneous. High pressures are really bad but not as bad as fire-prone alkali metals. Even after granting their compatibility with metals. The water also has the advantage of providing steam for heat transfer and the medium on the turbine prime mover. A less reactive metal like lead could be more acceptable.
There is a separate thread on eutectic metal core reactors:-
viewtopic.php?f=2&t=1678



Lithium is a reactive caustic metal. It is routinely handled with minor deterioration of quality by oxidation, and with safety - if common sense precautions are taken.


Like many liquid metals, water as vapor or liquid is the most common enemy of solid lithium. Water vapor catalyzes the reaction of lithium with atmospheric gases to form nitrides, oxides, carbonates, and secondary products. The reaction with liquid water is strongly exothermic and forms lithium hydroxide and hydrogen. The rate of the reaction increases with the surface area. Thus, lithium foil reacts more rapidly than ingot. The heat of this reaction can cause lithium to melt, which can lead to burning. This can, in turn, ignite hydrogen/air mixtures with explosive force. The dense, white, chocking cloud of lithium oxide or hydroxide attacks skin and mucosa.


Today, the use of lithium is becoming pervasive in modern society. Cars; hybrids and full electric…portable electronic devices: laptops, Ipads…expose the customer to a lithium fire potential. Proper Lithium packaging can minimize this risk.


Metal quality and safe handling require that water vapor be minimized and liquid water be totally avoided. The usual ways to achieve this is with dry inert gaseous atmospheres, or dehumidified air, or an inert, saturated hydrocarbonated coating (LITH-X).


The reactivity of molten lithium is much greater than solid lithium. Blanketing with argon or dry air protects lithium and minimizes the possibility of fires. Molten lithium reacts explosively with concrete flooring, and any area wherein a liquid lithium spill may occur must have welded steel flooring. A steel confinement vessel will minimize a spill to a small area and to prevent contact with other materials.

The reactivity of liquid lithium is a negative tradeoff item against lithium fluoride salt but not something that can’t be handled through responsive engineering.

I think that the control of hydrogen is by far more changing and expensive in a dueteride moderated reactor including those using heavy water.

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PostPosted: Apr 04, 2010 4:20 pm 
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"The reactivity of liquid lithium is a negative tradeoff item against lithium fluoride salt but not something that can’t be handled through responsive engineering."

Actually the reactivity of liquid lithium is a negative tradeoff item against liquid lithium.

Lithium fluoride salt is not reactive - so no negative tradeoff here.


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PostPosted: Apr 04, 2010 4:38 pm 
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It is thermodynamically highly unlikely in the presence of free lithium metal for any hydride or deuteride (other than LiH of LiD) to be stable above 500C.


This propensity for deuteride to release from other elements as the temperature increases is the big positive tradeoff that one gets when fluoride is removed from lithium moderation in favor of deuteride moderation.

Detrude release provides a wonderful passive failsafe negative feedback control mechanism that instantaneously controls reactivity increase at both a local (hot spot) level as well as an overall system basis.

In the original Hyperion Power Generation Inc patent application: this reactor control mechanism is explained in detail.


I think this concept is a wonderful idea and is a tradeoff that makes a transition from fluoride moderation to deuteride moderation worthwhile just on it’s own merit.


Quote:
all non-fluoride fluid chemistries *LACK* a good method for transferring freshly-bred U233 to the Core.


In a slurry reactor, U233 can be introduced into the core as a slurry particle with a small fraction of U233 deuteride coming from protactinium sequestration formulated within a thorium-232 deuteride slurry particle matrix.

Just feed it slowly into the slurry input interface. I don’t see a problem here.

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PostPosted: Apr 04, 2010 4:47 pm 
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Lars wrote:
"The reactivity of liquid lithium is a negative tradeoff item against lithium fluoride salt but not something that can’t be handled through responsive engineering."

Actually the reactivity of liquid lithium is a negative tradeoff item against liquid lithium.

Lithium fluoride salt is not reactive - so no negative tradeoff here.



Yes, I meant what you said.

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PostPosted: Apr 05, 2010 2:30 pm 
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Was it in this forum that someone mentioned very finely pulverized sugar charcoal suspended in carbon monoxide as a moderator of sufficient fluidity to be also a coolant? It would be opaque, like lithium, but would not require any analogue of lithium-six to be removed.

(How fire can be domesticated)


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PostPosted: Apr 05, 2010 2:49 pm 
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The release time of deuterium from a 75 micron particle of U233- deuteride is 33 milliseconds when that particle is exposed to a overheat excursion temperature.

Since the speed of deuteride release is a direct function of the size of the deuteride particle, the release time of deuterium from a volume of lithium deuteride will be much faster then 33 milliseconds since release is done on a molecular size scale.

Hydrogen is unique among the elements in the absorption desorption behavior. For example AFAIK, carbon does not behave in this fashion (absorption desorption behavior).

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PostPosted: Apr 05, 2010 8:59 pm 
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In the original Hyperion reactor hydride design, there are two separate regions, the core and a hydrogen storage plenum just above the core that contains a hydrogen absorbing material. These two zones are insulated both radiologically and thermally. They are connected by a free flow of hydrogen.

Taking a page out of the Hyperion book, in the Lithium Homogeneous Reactor (LHR), the gas from the bubbler system would carry desorbed/absorbed deuterium between these two regions.

Under normal operating conditions only a fraction of a percent of the hydrogen stored within the core will be exchanged between the core and storage media to maintain equilibrium in the reaction. A very small percentage, only three parts in one thousand of the core deuterium content is needed to be exchanged in the hydrogen storage plenum to control the reaction.

This hydrogen storage plenum can contain finely powdered thorium 232 or pure lithium to absorbed/desorbed deuterium in the core during a reactivity excursion.

There is a direct temperature relationship between the plenum and the core. To heat the core, the plenum contents are heated. This causes hydrogen to migrate from the plenum to the core increasing reactivity. To cool the core the content of the plenum is cooled and deuterium is absorbed in the plenum.

A sudden temperature increase in the core will cause deuterium in the core to be released, transferred to the plenum and absorbed in the plenum limiting the core temperature increase; For example, in the event of a total power failure.

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PostPosted: Apr 19, 2010 1:31 pm 
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The liquid thorium reactor can be thought of as a nuclear fuel/waste reprocessing plant that just so happens to also produce some power. The reason---the majority of the impactful cost related issues involve fuel/waste reprocessing.

For this reason, a slurry based reactor is the most cost effective approach because such a reactor allows the most fuel/waste reprocessing flexibility and associated advantage.


First, since thorium does not leave the fuel slurry, only protactinium, Np237, Pu238, trace amounts of Pu239 and other transuranics, noble metals and rare earths.are found in the lithium coolant. There is no thorium/rare earth separation issue in the Lithium Homogeneous Reactor (LHR). For this reason, the waste stream volume is minimized.

Natural chlorine can be used to separate protactinium from the waste stream. Getting the Protactinium out is straightforward, as the PaCl4 bubbles out at 400C.

Next, the remaining wastes can be separated from lithium chloride as follows:

http://www.freepatentsonline.com/4274834.html

This process for purifying lithium chloride containing small amounts of impurities such as suspended nuclear waste products which comprises heating lithium chloride contaminated with these impurities to a temperature in the range of from about 270° to about 325° C., cooling the lithium chloride to ambient conditions, extracting said lithium chloride with isopropanol, separating the liquid phase from the solid phase, removing said isopropanol from said liquid phase, and recovering a solid lithium chloride product of high purity.

Lithium of high purity can then be formed from this lithium chloride product and be reintroduced to the core fluid.

The resulting extracted solid waste steam is composed of Np237, Pu238, trace amounts of Pu239 and other transuranics, noble metals and rare earths. After some cool down, this minimized waste stream can be sent to a central waste handling facility for additional processing/disposal.


Extraction of protactinium from the blanket is easy when the blanket is composed of Thorium(IV) chloride (melting point at 770C) since the PaCl4 bubbles out at 400C. Natural chloride can be used since the blanket will only see thermal neutrons.


As you can see, in a hot cell environment, the cost of implementing such a fuel/waste processing approach just can’t be beat.

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