An earthquake measuring 6.5 on the Richter scale hit Japan’s Shizuoka Prefecture on Tuesday, injuring 87 people. Two reactors at the Hamaoka nuclear power station in central Japan were also shut down.

Hamaoka’s 4 and 5 reactors were the only two operating at the site. Unit 1 has been closed since 2001 after a pipe rupture caused by exploding hydrogen in the reactor’s heat removal system. Unit 2 was closed down in 2004 after similar problems were found in that reactor. A new reactor is being built on the site which is expected to replace units 1 and 2. Cracks were also found in the water pipes of Unit 3. Indeed, the Hamaoka reactors have something of a poor history.

On this occasion reactors 4 and 5 were shutdown safely. As it happens, the Hamaoka reactors ‘are located in the middle of an intraplate earthquake-prone region, where the Great Tokai Earthquake is expected to occur’. That’s the thing about building nuclear reactors in earthquake zones – you have to be lucky all the time but only unlucky once.