It has since been repaired. Japan has many nuclear plants. They may be far ahead than any Western world in the development of nuclear power. I understand there is a research going on in Europe with the US joining. The last news I knew of, is that the US is leaving the research efforts behind.
Nuclear plants has three redundant controls and safety measures.
This means that when one system malfunction, the other two systems override the controls. It is a sad fact that nuclear power generation is tainted with the idea of being like an untamed dragon on a leashed. Please consider also, that any nuclear power project is a political issue. This means that when one system malfunction, the other two systems override the controls. This requires two of three alarm signals to cause a protective action.