Abstract: Stretch-out operation mode can deepen the reactor burnup when the boron concentration is near 0 mg/L,in which the additional reactivity is introduced by the reducing of the moderator temperature and the decreasing of the load.Stretch-out is used in many nuclear power plants all over the world.The first stretch-out operation has been used for the first time in China..As a specific operation mode,which outruns the original reactor core design,the related and specialized design argument and safety analysis is required.As a consequence of the continuous or stepwise reduction of load and moderator temperature,the neurotic measurement system and the reactor control and protection system parameters should be modified specially.
Based on the schedule of the electricity production,the first stretch-out operation had been carried out from March 12 to March 21 2003.It successfully avoided the overlapping between 209 and 109 inspection shutdowns in Daya Bay Nuclear power station,and additional 30 GWH energies were produced.