Pressurized water reactor with upper vessel section providing both pressure and flow control

A method comprising:

• installing a reactor coolant pump comprising a pump motor, a driveshaft, an impeller, and a mounting flange on a pressurized water reactor (PWR) comprising a pressure vessel assembly comprising a vessel body and a vessel head secured thereto, a separator plate that separates the pressure vessel assembly into a pressurizer volume disposed above the separator plate and a reactor volume disposed below the separator plate, the installing including:
• pre-assembling the pump motor, the driveshaft, the impeller, and the mounting flange outside of the pressure vessel assembly to form a pump assembly as a unit disposed outside of the pressure vessel assembly in which the pump motor is connected with the impeller by the driveshaft,
• inserting the impeller and the driveshaft of the pump assembly through an opening of the pressure vessel assembly while the pump motor remains entirely outside of the pressure vessel assembly, the mounting flange being larger than the opening so that the motor will remain outside of the pressure vessel assembly while allowing passage of the impeller into the pressure vessel assembly, and
• securing the flange of the pump assembly to an outside of the pressure vessel assembly to mount the pump assembly on the pressure vessel assembly,
• wherein at least a portion of the pump motor of each reactor coolant pump is disposed above the separator plate.