This is not the only accident that happend in Japan. About 9-10 years ago, the Meihama Nuclear Plant caused some radiation leak. Whether it was contained or not, I can not remember. The caused of the accident was fluid induced vibration on the tubes of the nuclear steam generator. 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.