Impact of spacer on inter sub-channel mixing of coolant in nuclear fuel bundle. A survey and future patterns of research and advances

Broad efforts have been ended in the last decade for the development of spacer and its effect on droplets that present in the vapour core. The spacers operate as droplet collectors and accumulate considerable amount of the droplet flux in an emblematic spacer section. This development paved the way for engineers and researchers to come up with spacer that exhibit better inter subchannel mixing in the reactor. The review is based on the correlation developed by different researchers for the spacer modelling, grey areas and challenges for further improvement in the prediction and some of the good models have been recommended. The effect of spacer on liquid films and droplet depositions before spacer and near spacer have been studied and finally based on this investigation a proposed LDV measurement techniques have been applied on 1/12^th segment of Advanced Heavy Water Reactor for further analysis of spacer effect on annular flow. Efforts are made to uncover the investigated gaps from the precedent literatures, as an effect of which it is concluded that there is extremely inadequate work published in the field of thermal-hydraulics incorporating spacer effect such as turbulent mixing, droplet deposition and liquid film thickness in the case of AHWR.