[brutuss]

Commercial reactors are a bit different than naval reactors. They do indeed add boron to the primary water which acts as a chemical shim over core life. Initally the concentration is about 1200 ppm, reduced by 2 - 3 ppm per day, this allows all control rods to remain more or less fully withdrawn at all times (excepting axial power shaping rods which are positioned based on other criteria).

A shield water tank is not used, given that the larger available space allows for a massive solid vault to be used for biological shielding.

[P8riot]

A shield water tank is not used, given that the larger available space allows for a massive solid vault to be used for biological shielding.

Now that makes sense to me. I guess you get a little myopic sometimes operating on a single class of plant.