In a PWR core, one in every four fuel assemblies has a control rod in it, and in these special fuel.

In a PWR centre, one in entire impure fuel assemblies has a repress rod in it, and in these specific fuel assemblies, encircling one in entire ten rods is a repress rod. If the MFR in the centre (the fitness of the body of the moderator to the body of the fuel) is 4:1, venerate how divers repress rods there are in a bulky PWR centre.