Effect of refueling of one channel on the quality, void fraction, and temperature at channel exit/header in 700 MWe PHWR

In 700 MWe PHWR, during reactor operating at full power, more than two channels are required to be refueled per day. To achieve radial flux flattening for maximum power output from core, a differential burn-up scheme is adopted. This is done by judicious adjustment of the relative refueling rates in different core regions. When the refuelling of channel is undertaken i.e. during 'ON POWER REFUELLING' both fuelling machine (F/Ms) are clamped on both end fitting (E/F) of same channel. During on-power refuelling of PHWRs, cold water enters the channel from Fuelling Machine, which may affect the void fraction and temperature at the outlet of the channel being refuelled. This kind of temperature perturbation which might affect the neighboring channels due to their communication with the refuelling channel through the common ROH. To estimate the temperature drop and void fraction at the exit of channel which has been refuelled, a computer code 'RECHAN' has been developed. (author)