I have a simple idea that I would like to hear feedback on. Let me admit, right off, that I haven’t studied the nuclear reactor geometry in any detail, and this idea depends on such geometric (or layout) conditions.
As some of you may know, Fukushima is threatening (or has already begun), to go China Syndrome.
The simple idea is this: Build a wall around the Fukushima reactors, and start dumping in tin ball bearings. Very tiny ones, so that they are more space-filling, and can pour through smaller openings. If you need to, drill some holes through floors, tops of containments, etc.
If the nuclear materials are hot enough to melt concrete, then they are hot enough to melt the ball bearings. Concrete becomes “crumbly” at around 1000 C, and it’s constituent stone and sand don’t melt until 2600 C, according to this. The melting point of tin is 231.9 C.
Meanwhile, the thermal conductivity of tin is 67 W/(m.K), vs. .1- 1.8 W/(m.K) for concrete. (Ref).
Consequently, provided that you can get the tin ball bearings close enough to the bottom of the reactor where the nuclear materials are eating through the concrete, they should both melt faster than the concrete, and furthermore conduct the vast majority of heat upwards, through the mass of tin, rather than downwards.
Should the tin that’s enclosed become completely melted, you build a second wall, knock a hole in your first wall, to let the liquid tin pour through, and dump fresh tin ball bearings on the top of the reactor, within the circumference of the first wall. Repeat, as necessary. (I.e., as many additional walls as you need.
If you want to conserve energy, and the tin is not too radioactive, you can create a tin can factory, right there! 🙂 (I don’t think tin cans have tin, anymore. Just kidding, in this last paragraph.)
Tepco says that temperatures (assisted by water cooling) have been under 100C for a while, now. See http://www.tepco.co.jp/en/nu/f… . They also say “according to the gas sampling result in PCV, the gas caused by core concrete reaction is currently not detected. Therefore, it is estimated it is highly unlikely that the core concrete reaction still goes on.” My reference gives a source as the architect of the #3 reactor, but AFAIK, he doesn’t address the claims in the TEPCO report, point by point.