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Q & A: dry ice for Fukushima?

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Most recent answer: 03/22/2011
Q:
Does anyone know what would happen if those helicopters had dumped an equal tonnage of dry ice pellets instead of water into the damaged buildings? Being dry ice nothing more than solid carbon dioxide, I do not think it would cause any adverse chemical reaction. Physically, however, could the sudden lowering of temperature, say, open breaches in the containers? Anyway, what role, if any, could dry ice play in emergencies such as Fukushima, fire in refineries etc. (Obviously, I am neither in the dry ice market nor a firefighter, only a curious journalist.) Anyone having a plausible answer is invited to send it to me: ## mentioning Fukushima as the subject.
- Aldo Pereira (age way too long)
Sao Paulo SP Brazil
A:
Dry ice wouldn't particularly help with the cooling. The main cooling comes from the energy required to boil water, the latent heat of vaporization. For a given volume of material, water requires more heat to vaporize than does dry ice.

Mike W.

(published on 03/18/2011)

Follow-Up #1: dry ice cooling?

Q:
Thanks to Mike V. for helping me with the question. If I understood the thermodynamics involved, 1 gallon of water should require more heat to evaporate than 1 gallon of dry ice should to sublimate into gaseous CO2. Therefore, water should exert more cooling than an equal amount of dry ice. Kindly take into consideration I am a lay person in physics and chemistry trying to understand the difference of opinion between you and other engineers I have heard about the issue. On that (in)capacity, l ask: even you do not consider the beneficial effect of gaseous CO2 in putting down fire (an indirect cooling effect), should you not take time into account? After all, dry ice cools its surrounding space instantly, and water takes much longer. Thanks again, AP
- aldo pereira (age 78)
sao paulo
A:
You understood what we wrote precisely. These are very good questions and beyond our expertise. If engineers who are familiar with the problem say that CO2 does a better job than H2O at suppressing fires, we have no reason to disagree. I'm a little surprised that you say the dry ice cools more quickly, but maybe the engineers know something we don't about how different coolants manage to get in past the vapors to the rods.

Mike W.

(published on 03/20/2011)

Follow-Up #2: you're welcome

Q:
No further inquiry, only warm thanks to Mike V. for the patient and elucidative explanation.
- Aldo Pereira (age 78)
Sao Paulo
A:
vocÍ ť bem-vindo

Mike W.

(published on 03/22/2011)

Follow-up on this answer.