Reactors Cooled by Ga Alloys: Benefits and Challenges

  • Thread starter snorkack
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In summary, reactors cooled by gallium alloys are useful due to their high neutron cross-section, low melting point, and potential for alloying with other low melting metals. The coolant mixture of Ga and Sn is less reactive and not poisonous when irradiated, making it convenient to handle. However, the price of gallium is significantly higher compared to other commonly used coolants such as sodium. In terms of cost comparison, the price of gallium is dependent on its enrichment and the cost of separative work units, while the cost of plutonium 239 is dependent on the cost of starting material and the process of irradiation and separation.
  • #1
snorkack
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How useful are reactors cooled by gallium alloys?

Ga has cross section for neutrons of 2,9 barns. Somewhat high - but K has 2,1 barns, and NaK is mostly (76 %) K.

Pure Ga melts under +30 Celsius. The reactor may freeze - but it is much easier to melt than Pb/Bi eutectic (+125 Celsius).

Ga melting point can be further lowered by alloying. While In, Cd and Hg are neutron poisons, the other low melting metals are reasonable - Pb, Bi, also Sn (0,62 barns) and Zn (1,1 barns).

Would a reactor with Ga-Sn coolant be convenient to handle? Ga/Sn melt is nowhere as reactive as Na/K melt, and also not poisonous until irradiated...
 
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  • #2
Gallium's price has been on the order of $650/kg but could be has high as $750 to $970/kg as compared to sodium at around $150/kg.

In a reactor, liquid metal embrittlement with fuel and structural materials is an issue. Liquid metals are usually used for fast reactors.
 
  • #3
Clementine managed to work with mercury coolant - despite its huge neutron cross-section.

How does the quoted price of gallium compare with the price of highly enriched uranium 235, or plutonium 239? These are presumably priceless because no one wants to sell them...
 
  • #4
snorkack said:
Clementine managed to work with mercury coolant - despite its huge neutron cross-section.

How does the quoted price of gallium compare with the price of highly enriched uranium 235, or plutonium 239? These are presumably priceless because no one wants to sell them...
It depends on the enrichment. One could develop a price based on the quantity of natural U (0.7%) needed to provide a particular enrichment and the cost of the separative work unit (SWU) to enrich it. Cost of Pu239 depends on cost of starting material (U), irradiation, and separation.
 
  • #5


Reactors cooled by gallium alloys have both benefits and challenges. On one hand, gallium has a relatively high neutron cross section, making it an effective coolant for nuclear reactors. It also has a lower melting point compared to other potential coolants such as lead or bismuth, making it easier to handle and melt if it were to freeze. Additionally, by alloying gallium with other low melting point metals such as tin, the melting point can be further lowered, making it even more convenient for use in reactors.

However, there are also challenges associated with using gallium alloys as coolants. The first is its relatively high neutron cross section, which can lead to increased neutron absorption and therefore decreased reactor efficiency. This can be mitigated by using other low melting point metals in the alloy, but this may also introduce other challenges such as reactivity and toxicity.

Another challenge is the potential for the reactor to freeze if the temperature drops below +30 Celsius. While this is easier to melt than other coolants like lead or bismuth, it still presents a potential issue for reactor operation and maintenance.

In conclusion, reactors cooled by gallium alloys have their benefits and challenges. While they may offer a lower melting point and potential for alloying with other low melting point metals, the high neutron cross section and potential for freezing must also be carefully considered. Further research and development is needed to determine the feasibility and usefulness of reactors cooled by gallium alloys.
 

What is a reactor cooled by Ga alloys?

A reactor cooled by Ga alloys is a type of nuclear reactor that uses liquid gallium as a coolant instead of traditional water. The gallium is circulated through the reactor core to remove heat and prevent the fuel from overheating.

What are the benefits of using Ga alloys as a coolant?

There are several benefits to using Ga alloys as a coolant in reactors. These include a higher boiling point, which allows for higher operating temperatures and more efficient energy production. Ga alloys also have a lower neutron cross-section, meaning they absorb fewer neutrons and allow for more efficient fuel usage. Additionally, Ga alloys do not corrode as easily as water, reducing maintenance costs and increasing the longevity of the reactor.

What are the challenges associated with using Ga alloys as a coolant?

One of the main challenges with using Ga alloys as a coolant is their reactivity with air and water. Gallium can react with oxygen and moisture in the air, forming a protective oxide layer that can impede heat transfer. This requires careful handling and maintenance procedures to prevent buildup of this oxide layer. Another challenge is the limited availability of gallium, making it a more expensive coolant option.

Are there any safety concerns with reactors cooled by Ga alloys?

Like any nuclear reactor, there are safety concerns with reactors cooled by Ga alloys. However, studies have shown that using Ga alloys as a coolant can actually improve safety by reducing the likelihood of accidents such as explosions or fires. The higher boiling point of gallium also allows for a larger margin of safety in case of a loss of coolant accident.

Are there any current reactors using Ga alloys as a coolant?

Yes, there are currently a few research reactors using Ga alloys as a coolant. However, the use of Ga alloys as a coolant is still in the early stages of development and has not yet been widely implemented in commercial nuclear reactors. Further research and testing are needed to fully understand the benefits and challenges of using Ga alloys as a coolant in large-scale reactors.

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