Daya Bay Unit 2 restarted, Unit 1 still failing safety tests

In the continuing saga of the Daya Bay nuclear power plant control rods, Unit 1 continues to fail safety tests, but Unit 2 has been restarted. Unit 2 went on line on May 20, completing its annual refueling outage. During the outage, eight additional control rods were added to its original 53. The control rods regulate the power level of the reactor. “This will further ensure that the reactor can be shutdown, if needed, well within the safety requirements,” said Dominique D?got, Framatome International Operations managing director.

A series of stringent requalification tests were carried out before restart, including a control rod drop time test. After a close study of the test results, the National Nuclear Safety Authority, the Chinese safety regulatory body, gave approval for the restart.

Unit 1 has also been down for scheduled refueling and overhaul since mid-December 1994. The unit was originally to restart in February, but the shutdown has been extended after unsatisfactory test results on seven of its 53 control rods. Tests are still under way.

Framatome, the French builder, is considering using guide tubes from an older design to rectify the situation. Other possibilities include adding control rods, as they did in Unit 2, or a complete control rod replacement. Framatome has agreed to pay for the repairs under warranty, which will run out 21 days after this outage is completed.