The NHK has another surprising story, dated 10 March 2013 :
http://www3.nhk.or.jp/news/genpatsu-fukushima/20130310/index.html : As specialists had suggested that part of the water injected by fire-engine had leaked somewhere, the NHK procured by itself the unit 3 piping drawings and conducted a detailed analysis together with some specialists.
As a result, it was found that there is a byroad starting between the fire-engine and the reactor, and there is a possibility that water runs through the byroad and leaks into another device which is not the reactor.
At the end of the byroad, there is a device called "condenser" which is used to generate electricity and transforms steam back into water. Normally, the pump that is located there on the way, is running, so that the water is kept back, so that it does not flow into the condenser.
However, as we tested in an experiment with the help of the specialists, it was found that in the case where the pump is down, the water flows through without stopping, and there is a high probability that the water leaked during the Fukushima accident as all electric power had been lost.
This experiment result is corroborated by a press conference held by Tepco immediately after the accident, where Tepco indicated that at that time, unit 3's condenser was in a full-of-water status which cannot happen in normal time.
Furthermore, when unit 3's water flow generated by fire-engine injection is experimentally reconstructed and when that experimental result in used by specialists in a simulation, they find that 55% of the water volume leaks out instead of being injected into the reactor, and they conclude that this leaked amount is sufficient to explain why the meltdown could not be averted.
On the other hand, they conclude that if the leaked amount had been 25% or less, the meltdown could have been averted.
After the accident, fire-engines have been installed as a safety measure at every nuclear power plant in the country, but more than two years after the accident, what is emerging is that sufficient verifications have not been carried out about how certain it is that the water will enter the reactor.
According to Hosei University visiting professor Hiroshi Miyano, "the job is not finished after fire-pumps are installed, and it is meaningless if one does not check if a sufficient amount of water for cooling the nuclear fuel is coming into the reactor. The verifications made after the accident have not been sufficient."
http://www3.nhk.or.jp/daily/english/20130310_28.html (NHK World English version)
