11.   The control rods, which regulate the speed of the nuclear reaction, were changed last March as part of routine maintenance.

12.   The Qingshan plant has been shut down for three months for work on control rods, a safety mechanism.

13.   The three operators found damage from small jam nuts that may not have been tightened correctly, raising a risk of damage to a tab control rod.

14.   Water levels in the core were abnormally low, and too few control rods were in the reactor.

15.   Experts found loosened nuts securing a control rod to the mechanism lying next to the track.

16.   The unit received approval from the National Nuclear Safety Bureau to restart after French suppliers, Framatome SA, provided temporary replacements for defective control rods, it said.

17.   The unit received approval to restart from the National Nuclear Safety Bureau after French suppliers, Framatome SA, replaced faulty control rods, it said.

18.   The graphite control rods are inserted into the fuel rods to slow down the nuclear reaction.