4 ms·

> Most nuclear reactors today operate well below 1,000 degrees Fahrenheit I have a background in chemical engineering and still had no clue that nuclear reacto

> Most nuclear reactors today operate well below 1,000 degrees Fahrenheit I have a background in chemical engineering and still had no clue that nuclear reactors operate at the temperature of a pizza oven. That's wild.

klodolph 6y ago
What’s amazing to me is that the kind of graphite used in nuclear reactors doesn’t burn until it’s white hot, somewhere around 1650°C.
- corty 6y ago
  That is not a property of the graphite, its a property of the atmosphere (CO₂, He) or lack thereof (H₂O, molten salts) around the graphite. The Chernobyl core started burning as soon as external atmosphere hit the graphite after an explosion.
  - klodolph 6y ago
    Actually, it is a property of graphite. You may be surprised. http://nucleargreen.blogspot.com/2011/03/does-nuclear-grade-graphite-burn.html http://nucleargreen.blogspot.com/2011/03/does-nuclear-grade-...
- sbierwagen 6y ago
  Graphite doesn't burn well, but it does erode away in a stream of hot oxygen or CO2. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660019918.pdf https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/196600... The CO2-based Advanced Gas-cooled Reactor runs at 650C to keep core lifespan reasonable. https://en.wikipedia.org/wiki/Advanced_Gas-cooled_Reactor https://en.wikipedia.org/wiki/Advanced_Gas-cooled_Reactor
Obi_Juan_Kenobi 6y ago
Using liquid water as your moderator really constrains how hot you can go.
- sbierwagen 6y ago
  St. Vrain was helium cooled and graphite moderated and it only ran at 1430F, which still caused some hair-raising operational problems: https://www.nrc.gov/docs/ML0403/ML040340070.pdf https://www.nrc.gov/docs/ML0403/ML040340070.pdf High temps are very good for efficiency, but are difficult for safety. Only China is building VHTRs right now. If anyone ever builds a supercritical water reactor then it would give you decent efficiency without the problems of exotic coolants.
dhsysusbsjsi 6y ago
Translations for SI units: 1000°F = 538°C 2000°F = 1093°C
- p1mrx 6y ago
  The SI units are 811 K and 1366 K (or 800 K and 1400 K, using a reasonable number of sig figs.)
  - mhh__ 6y ago
    Celsius is also an SI derived unit
    - dhsysusbsjsi 6y ago
      Oh thanks to both comments - I learned something !

klodolph 6y ago

What’s amazing to me is that the kind of graphite used in nuclear reactors doesn’t burn until it’s white hot, somewhere around 1650°C.

corty 6y ago
That is not a property of the graphite, its a property of the atmosphere (CO₂, He) or lack thereof (H₂O, molten salts) around the graphite. The Chernobyl core started burning as soon as external atmosphere hit the graphite after an explosion.
- klodolph 6y ago
  Actually, it is a property of graphite. You may be surprised. http://nucleargreen.blogspot.com/2011/03/does-nuclear-grade-graphite-burn.html http://nucleargreen.blogspot.com/2011/03/does-nuclear-grade-...
sbierwagen 6y ago
Graphite doesn't burn well, but it does erode away in a stream of hot oxygen or CO2. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660019918.pdf https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/196600... The CO2-based Advanced Gas-cooled Reactor runs at 650C to keep core lifespan reasonable. https://en.wikipedia.org/wiki/Advanced_Gas-cooled_Reactor https://en.wikipedia.org/wiki/Advanced_Gas-cooled_Reactor

Obi_Juan_Kenobi 6y ago

Using liquid water as your moderator really constrains how hot you can go.

sbierwagen 6y ago
St. Vrain was helium cooled and graphite moderated and it only ran at 1430F, which still caused some hair-raising operational problems: https://www.nrc.gov/docs/ML0403/ML040340070.pdf https://www.nrc.gov/docs/ML0403/ML040340070.pdf High temps are very good for efficiency, but are difficult for safety. Only China is building VHTRs right now. If anyone ever builds a supercritical water reactor then it would give you decent efficiency without the problems of exotic coolants.

dhsysusbsjsi 6y ago

Translations for SI units: 1000°F = 538°C 2000°F = 1093°C

p1mrx 6y ago
The SI units are 811 K and 1366 K (or 800 K and 1400 K, using a reasonable number of sig figs.)
- mhh__ 6y ago
  Celsius is also an SI derived unit
  - dhsysusbsjsi 6y ago
    Oh thanks to both comments - I learned something !