Start-up of new Shimane unit delayed

15 February 2011

The fuelling and start-up of the Shimane 3 nuclear power reactor in Japan has been delayed by three months due to a fault with the control rod drive mechanism, Chugoku Electric Power Co announced.


Shimane 3 (Chugoku)
An artist's impression of Shimane 3 (Image: Chugoku)
Construction of Shimane 3 - a 1373 MWe advanced boiling water reactor (ABWR) - started in December 2005. As of the end of December 2010, the unit was 91.3% complete, according to Chugoku. The unit had been scheduled to begin commercial operation in December 2011.


However, Chugoku has now said that it discovered in late November 2010 that it could not smoothly insert the control rods into the reactor. A subsequent inspection found that there was distortion in the driving screws in some of the control rod drives (CRDs). It was found that 18 out of a total 205 CRDs had the fault.


Chugoku said that it assumes that the distortion in the driving screws was caused by foreign matter that probably came from water either within the reactor or in the CRD screw itself. The foreign matter was thought to be jamming the screw drive, thereby increasing the resistance of the screw beyond the driving force of the motor.


The utility said that all the CRDs will now be removed from the reactor and returned to supplier Hitachi-GE Nuclear Energy. Once they have been cleaned and inspected, the CRDs will be reinstalled. Chugoku said that, in order to avoid a repeat of the fault, it will clean the reactor itself and use clean water when the CRDs are reinstalled.


As a result, Chugoku has delayed fuel loading at Shimane 3 by three months, from March 2011 until June 2011. Commercial operation has correspondingly been put back from December 2011 to March 2012.


Researched and written

by World Nuclear News