1.   It activated an automatic safety system, sending control rods down into the core of the plant.

2.   The balance is achieved in most cases using control rods that must be physically raised or lowered inside the reactor to absorb some of the neutrons.

3.   The control rods he sought to lower into the reactor jammed.

4.   The report recounts an incident in February in which a reactor operator inserted control rods into the reactor farther than he intended to.

5.   There were no control rods, they said.

6.   How many control rods were in the core at the time of the explosion?

7.   It was forced to shut down for six weeks last year because of faulty control rods in a reactor.

8.   It was forced to shut for six weeks last year because of faulty control rods in a reactor.

9.   Later, naval ships recovered a control rod, a fire extinguisher, two pieces of clothing and identification cards, but no wreckage was sighted.

10.   Operators at a problem-plagued Ukrainian nuclear power plant on Monday restarted a reactor they had shut down a day earlier because of a malfunctioning control rod.