When the head of the world's nuclear watchdog died in July, his death was kept secret for four days. Many people didn't even know Yukiya Amano was sick. The process that will see his post finally filled this week is shrouded in just as much mystery.

The ambassadors of the 35 nations on the International Atomic Energy Agency's board will enter a sealed chamber at its headquarters in Vienna on Monday. Two lawyers acting as witnesses will stand guard as one-by-one each envoy slips a paper ballot into a wooden box. Votes are counted and if nobody receives two-thirds, the process is repeated.

It will be only the sixth time since the dawn of the nuclear age that the IAEA's board of governors convenes for the odd ritual, which has been compared to the conclave, the gathering of Catholic cardinals who select the new pope.