Seeking examples reliably safe fission reactor designs

  • Thread starter Thread starter treehouse
  • Start date Start date
  • Tags Tags
    Fission Reactor
Click For Summary

Discussion Overview

The discussion focuses on the exploration of reliably safe designs for fission reactors, particularly thorium reactors and other advanced reactor concepts. Participants examine various reactor designs, their safety features, and the implications of different cooling mechanisms. The scope includes theoretical considerations, technical specifications, and safety assessments.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants express interest in thorium reactors, suggesting they cannot melt down, although others challenge this by stating that any fission system can potentially melt down if cooling is inadequate.
  • One participant describes the ESBWR design, highlighting its passive safety features that allow for cooling without power for up to 72 hours.
  • There are mentions of sealed, passive reactor designs that utilize temperature feedback for control, which some participants argue enhances safety by preventing leaks of radionuclides.
  • Liquid nuclear fuel designs are discussed, with a participant noting that they operate in a melted state and rely on a fail-safe mechanism to manage overheating.
  • Concerns are raised about the risks associated with loss of coolant and heat sink in current commercial reactors, with the ESBWR's design being presented as a solution to these risks.
  • Participants seek mathematical insights into the dynamics of dangerous measurements in reactor systems and how quickly they can be controlled.
  • Some participants propose that increasing the thickness of containment materials could mitigate risks to humans from hazardous materials.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the safety of thorium reactors, as some assert they cannot melt down while others disagree. The discussion contains multiple competing views on reactor designs and their safety features, indicating that the topic remains unresolved.

Contextual Notes

Limitations include the dependency on specific reactor designs and the proprietary nature of detailed safety calculations, which may restrict access to comprehensive mathematical models.

treehouse
Messages
105
Reaction score
0
I'm writing about emerging technologies the richest people on Earth would be thrilled to have. In fact, its already hit the noosphere. Now I'm writing another appeal to investing in people (this one focusing more on biopersonal impacts than technosocial development) and wish to publish it with a concise explanation of intraplanetary post-scarcity.

What are some reliably safe designs for fission reactors? I'm particularly interested in thorium reactors as they cannot melt down1.

1http://www.physorg.com/news/2011-06-pint-sized-particle-nuclear-energy.html
 
Engineering news on Phys.org
The article in Physorg is about accelerator driven systems.

As for melting, thorium reactors certainly could meltdown.

Any fission system produces fission products, and fission products generate decay heat. If the heat is not removed via a cooling system, then the fuel material will melt.

Coolability is an inherent part of a reactor design. Some designs however can tolerate higher temperatures, e.g., reactor using TRISO fuel (with alternate layers of pyrolytic carbon and SiC or ZrC) in gas cooled environment driving a Brayton cycle. Thermal efficiencies increase with temperature, but then so does materials degradation in an irradiation environment or high temperature water/steam.

Thoria is desirable for its high thermal conductivity and higher melting point than UO2, although thoria systems would contain U-235, Pu-239 or U-233 which are fissile.

Accelerator driven systems could in theory produce fast neutrons for fission U-238 or Th-232, but also transmute longer-lived fission products to shorter-lived fission products. The feasibility however is yet to be determined.
 
The ESBWR design utilizes natural circulation and large accumulators, giving it 100% passive 72 hour safety capability, even under station blackout conditions.

There are also designs for sealed, passive reactors which use temperature feedback for control, which is also inherently safe.
 
treehouse said:
... I'm particularly interested in thorium reactors as they cannot melt down1.
There are liquid nuclear fuel designs, but no working implementations aside from a couple experimental reactors in the 1950s and 60s. In other words they operate in an 'already melted' state. Should the primary cooling mechanism of such a reactor stop or fail for some reason so that the fluid temperature continues to rise, the reactor releases the hot fluid by means of melting a fail safe freeze plug and then into a dump tank where the fluid can cool down safely. The dump tanks and freeze plug are shown in blue in this diagram:
http://upload.wikimedia.org/wikipedia/commons/0/08/Molten_Salt_Reactor.svg
 
QuantumPion said:
The ESBWR design utilizes natural circulation and large accumulators, giving it 100% passive 72 hour safety capability, even under station blackout conditions.

There are also designs for sealed, passive reactors which use temperature feedback for control, which is also inherently safe.

The sealed reactor designs sound safest as that suggests to me they don't leak radionuclides. Please tell me more about this.
 
QuantumPion said:
The ESBWR design utilizes natural circulation and large accumulators, giving it 100% passive 72 hour safety capability, even under station blackout conditions.

There are also designs for sealed, passive reactors which use temperature feedback for control, which is also inherently safe.

mheslep said:
There are liquid nuclear fuel designs, but no working implementations aside from a couple experimental reactors in the 1950s and 60s. In other words they operate in an 'already melted' state. Should the primary cooling mechanism of such a reactor stop or fail for some reason so that the fluid temperature continues to rise, the reactor releases the hot fluid by means of melting a fail safe freeze plug and then into a dump tank where the fluid can cool down safely. The dump tanks and freeze plug are shown in blue in this diagram:
http://upload.wikimedia.org/wikipedia/commons/0/08/Molten_Salt_Reactor.svg

Why are those reactor designs so safe? I need to express this as clearly as possible.

I'm thinking if current radionuclide storage techniques contain nearly all the hazardous materials, overscaling the thickness of the containment material will eliminate risks posed to humans by such.
 
QuantumPion said:
The ESBWR design utilizes natural circulation and large accumulators, giving it 100% passive 72 hour safety capability, even under station blackout conditions.

There are also designs for sealed, passive reactors which use temperature feedback for control, which is also inherently safe.

I need the math on how fast dangerous measurements can rise and the relative speed with which they can be brought under control.
 
treehouse said:
I need the math on how fast dangerous measurements can rise and the relative speed with which they can be brought under control.

Best information I have seen for ESBWR is the design certification descriptions at
http://www.nrc.gov/reactors/new-reactors/design-cert/esbwr.html. NRC site has other design certifications for AP1000 (in progress), ABWR and is in the process of reviewing others.

Math may be limited as much of the detailed design is considered proprietary. But if you need that level of information you probably need to team up with some technical experts to summarize the technical work. Even then, for the number of different designs, that could fill volumes.
 
Last edited by a moderator:
treehouse said:
Why are those reactor designs so safe? I need to express this as clearly as possible.

I'm thinking if current radionuclide storage techniques contain nearly all the hazardous materials, overscaling the thickness of the containment material will eliminate risks posed to humans by such.

The greatest risk factors for current commercial nuclear power plants is loss of coolant (e.g. by piping break) or loss of heat sink (e.g. by loss of feedwater flow due to station blackout). Since the ESBWR is designed to be cooled by natural circulation, even a total loss of power would not prevent the core from being cooled. Furthermore, the large accumulators allows the core to continue to be cooled by passive/gravity driven systems which do not require operator intervention or power to operate valves/etc for 72 hours, and minimal intervention allowing indefinite passive cooling.

The sealed reactors are small and therefore do not rely on active cooling to prevent damage, and are further protected by inherent nuclear design which precludes the possibility of a power excursion.
 

Similar threads

Safe zero base reactivity level nuclear fission reactor?
  • · Replies 2 ·
Replies
2
Views
2K
Graduate Seeking examples of nuclear reactions that generate heat but not radionuclides
  • · Replies 1 ·
Replies
1
Views
2K