Conjecture about the consequences of the Fukushima nuclear melting in Japan, and why the fuel rods cannot be taken directly to prevent leakage of core melting

I believe many people have similar questions about the Fukushima nuclear power crisis caused by the earthquake and tsunami in Japan: what are the consequences of nuclear melting? Why can't we send robots to directly Remove fuel rods to prevent leakage of core melting cores? Since nuclear fuel is put together to produce a chain reaction or the temperature is too high, isn't it good to separate them into different containers?

I'm ashamed to say that I graduated from physics and claimed to have learned four mechanics, but I couldn't answer these high-tech questions. After searching for the Internet for half a day, I did not find the complete and persuasive information. I can only say that there may be the following statements:

1. after the earthquake, all nuclear reactors in Fukushima have been automatically shut down, and all the control rods have been inserted and there is no chain reaction. The problem is that even if the chain reaction has been stopped, its radioactive decay material continues to heat up and cannot be effectively cooled, resulting in core melting;

2. The fuel rod was originally wrapped in a zirconium alloy tube, which is relatively safe. Once the shell is melted, the fuel rod will be exposed and produce a large amount of radioactive gas, leading to dangerous nuclear leakage;

3. there are a large number of radioactive substances in the reactors, which may cause damage to other substances, including electronic devices. It is difficult to photograph and photograph the inside of the reactors. Therefore, ordinary robots cannot be close to each other, if people are close to each other, they will die. In a short time, they will not be able to create high-intensity anti-radiation robots;

4. the construction of the Fukushima nuclear power plant was relatively early, and the installation of equipment was not considered in advance to cope with this emergency. When the fuel rod is changed normally, the top cover should be opened to operate in case of low radiation, the temperature of the spent fuel rod for replacement is very high and it also needs to be cooled down. There are very complicated procedures for replacement. If there are hundreds of fuel rods and a few pounds of heavy stuff, they should be removed and processed one by one; in the case of no electricity and high radiation, it will be more troublesome to disassemble and remove the fuel rod. It will take longer. More radioactive substances are leaked, and an accident will be caused by carelessness, at this time, the decision makers will not take this risk. It is better to find a way to reduce the temperature. At the beginning, no one thought there would be a big problem and it was too late to wait until the core was melted;

5. if the core is completely melted, the resulting melting will contain all fuel rods, shells, control rods, water, decay products and other substances, and nuclear fuel of the same nature may be merged for a long time; in theory, the worst case is that the chain reaction may occur again when the critical state is reached, and the temperature will rise further, which may melt the secure Bottom Shell and fall underground, groundwater poses a greater threat to nuclear pollution. Of course, at present, it is unlikely that such a catastrophic event will happen.

The above content is purely personal speculation and is not published by authoritative authorities.