Reactors Cooled by Ga Alloys: Benefits and Challenges

  • Thread starter Thread starter snorkack
  • Start date Start date
Click For Summary

Discussion Overview

The discussion focuses on the potential benefits and challenges of using gallium alloys as coolant in nuclear reactors. It explores aspects such as neutron cross-sections, melting points, and economic considerations related to gallium compared to other materials like sodium and mercury.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • Some participants note that gallium has a neutron cross-section of 2.9 barns, which is relatively high compared to potassium and sodium, suggesting implications for reactor design.
  • There is a discussion about gallium's melting point being lower than that of lead-bismuth eutectic, which may make it easier to manage in reactor conditions.
  • One participant proposes that alloying gallium with other low melting metals like lead, bismuth, or tin could enhance its utility as a coolant, while noting that some metals like indium and cadmium are neutron poisons.
  • Concerns are raised about the cost of gallium, which is significantly higher than sodium, and how this might affect its feasibility as a coolant.
  • Liquid metal embrittlement is mentioned as a potential issue when using gallium alloys in conjunction with fuel and structural materials.
  • Comparative pricing of gallium to highly enriched uranium and plutonium is questioned, with considerations about the complexities of pricing based on enrichment and separation costs.

Areas of Agreement / Disagreement

Participants express differing views on the practicality and economic viability of using gallium alloys as coolant, with no consensus reached on the overall benefits versus challenges.

Contextual Notes

Limitations include uncertainties regarding the long-term behavior of gallium alloys in reactor environments and the implications of liquid metal embrittlement, which remain unresolved in the discussion.

snorkack
Messages
2,388
Reaction score
537
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...
 
Engineering news on Phys.org
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.
 
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...
 
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.