I've been wondering if any design ideas could be pulled from these.
http://www.structint.com/tekbrefs/sib96138/fig3.gif
It's a picture of a reactor jet pump. I used to do the instrumentation for them. The drive flow from the recirc pump would come up the middle and split in half in the rams head. From there the drive flow would entrain 2 times the volume of water from around the nozzles. Then they would build pressure in the diffuser to be able to force the water through the core. Normal core flow at 100% power was 102.5 million lbs/hr with only 30 million lbs/hr from the pumps themselves.