6 ms·
"liquid sodium, whose boiling point is more than 8 times higher than water’s" Ew, multiplicative temperature comparisons in unspecified units. Sodium's boilin
by Jabbles 3y ago
"liquid sodium, whose boiling point is more than 8 times higher than water’s"
Ew, multiplicative temperature comparisons in unspecified units.
Sodium's boiling point is 882'C.
"so it can absorb all the extra heat"
Confusion of temperature and heat? Sodium's specific heat capacity is ~1/3 of water, so sodium's higher boiling point doesn't by itself mean that it can absorb more heat, though ofc the combination is still in sodium's favour.
- sandworm101 3y agoBut sodium's reactive, fire-starting, go-boom, good pair of running shoes temperature is considerable lower than water's.
- jebarker 3y ago> Ew, multiplicative temperature comparisons in unspecified units In the previous paragraph he's said that water boils at 100 C
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- tempodox 3y agoI'd expect a multiplicative temperature comparison to refer to Kelvin, not Celsius.
- jebarker 3y agoAh, TIL that Celsius is "non-multiplicative". From ChatGPT: "When using Celsius as the unit for temperature, it is not meaningful to say that one temperature is a certain number of times higher than another. The Celsius scale is based on the freezing point (0°C) and boiling point (100°C) of water, which are not absolute values. Thus, the Celsius scale has negative values, and simply multiplying temperatures does not provide an accurate representation of relative differences. If you want to compare temperatures in a more meaningful way, you should use the Kelvin scale. The Kelvin scale is an absolute temperature scale, with its zero point (0 K) representing absolute zero. In this scale, it is appropriate to say that one temperature is a certain number of times higher than another because the scale starts at an absolute zero point. To convert Celsius temperatures to Kelvin, add 273.15 to the Celsius value. Once the temperatures are in Kelvin, you can then make meaningful comparisons using multiplication or division."
- _a_a_a_ 3y agoYeah, kelvin strictly speaking, but for reactors on earth (not in 3 kelvin outer space) with a baseline earth-ambient temperature, perhaps multiplicative C is valid, very approximately? I don't know, I guess I'm asking.
- ethbr0 3y agoSpecifying "times" in Celsius is fine... as long as you stay either positive or negative. Implying that you can only specify multiples in Kelvin is being pedantic.
- sgjohnson 3y agoBut not really. 100°C times two is not 200°C. 100°C times two is 473°C
- ethbr0 3y agoHowso? If the conversion to Kelvin is additive (as opposed to something more complicated), and multiplying in Kelvin is fine, then how is multiplying effectively-unsigned in Celsius not fine?
- sgjohnson 3y agoOk, another example. Is 10°C 10 times as hot as 1°C? No. Multiplying kelvin is fine because kelvin is an absolute scale.
- _a_a_a_ 3y ago> No. For a given baseline, perhaps yes?. Kelvin has its baseline inherent, for C you can pick what you like if you're clear about it. Perhaps. (Edit: and using only positive or negative temps as pointed out above)
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- hermitcrab 3y agoOr Rankine for a US reactor, surely? ;0)
- DarkNova6 3y agoSodium is such a nightmarish coolant. Yes, there are advantages in building and engineering a sodium cooled reactor, but from an operating point of view... oh boy. Sodium catches fire when exposed to air. Sodium reacts violently with water (used in some designs as secondary cooling cycle). Sodium absorbing a neutron creates a strong gamma emitter with a low half time. Sodium reactors have always had low availability times, caused by constant technical problems. However unlike lead as coolant, no advances in material sciences are required to get an operational Gen 4 reactor. On the upside, you can pretty much use Sodium (fast) reactors right now... but maybe you shouldn't?
- gus_massa 3y ago> Sodium absorbing a neutron creates a strong gamma emitter with a low half time. Isn't that a feature? Is it 24Na that decays to 24Mg in 14 hours? In case of an accident, you can run away for a week and it will magically disappear. You don't need a long term storage of the waste.
- wolfram74 3y agofor that specific waste, the coolant in a water cooled reactor isn't a huge problem either. The things that are "complicated" are the fuel rods that some people refuse to be convinced we can bury in storage until reprocessing becomes necessary.
- sbaiddn 3y agoRun away where? To the next river basin? Na will dissolve into any moisture and be carried away by any moisture.
- meepmorp 3y agoThe advantage is 24Na's short (14.9 hour) half-life, not the lack of solubility in water. Half of the original radiation will be gone in 15 hours, and close to 90% in two days.
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- rvnx 3y agoA higher boiling point means that the coolant can absorb more heat without turning into a gas, which is crucial for efficient heat transfer in the reactor. The statement about the boiling point being "8 times higher" refers to the boiling point comparison, not the specific heat capacity (which is +/- 3.4 times higher).
- Gwypaas 3y agoHere is a read on the horror of building a sodium cooled reactor. Makes Vogtle look like a walk in the park. https://en.wikipedia.org/wiki/Monju_Nuclear_Power_Plant https://en.wikipedia.org/wiki/Monju_Nuclear_Power_Plant
- natmaka 3y agoAfter bout 60 years and many heavily-financed large projects there isn't a single one industrial breeder reactor ready for deployment. https://en.wikipedia.org/wiki/Breeder_reactor#Development_and_notable_breeder_reactors https://en.wikipedia.org/wiki/Breeder_reactor#Development_an...
- Mistletoe 3y ago>As of June 2011, the reactor had only generated electricity for one hour since its first testing two decades prior. It would be hilarious if not for the wasting of a trillion Yen on this.
- sbaiddn 3y agoHis understanding appears worse than that. Heat capacity is important, but as a second order. Absolute temperatures is the real deal since it sets the Carnot efficiency. Another way to look at it, if I were doing a back of the envelop calculation (the most important calculations), I wouldn't look up the Cp of Na. Id only look up its boiling T High Cp, low Cp... that can be remedied to some extent by running the pump faster or slower.
- pyrale 3y agoThe text also kind of blanks the part where 2/3rd of world's nuclear reactors are PWRs, with typical water boiling temperature around 275°c. Overall, the piece is a very flattering take on the technology, where all drawbacks are forgotten, and the comparison with competitors is not really honest.
- anonuser123456 3y agoI don’t think the specific heat matters so much. The key is the boiling point is so high, the thermal flux will cool the system before pressurizing it. IIRC, thermal flux is proportional to the temperature differential.