If a material reflects neutrons perfectly without absorbing them, we could make the reactor much smaller with using such material as reflector. But we haven't had such ideal material so far. Here is an idea for reflecting neutrons more effectively than using usual reflectors.

 

http://hecoaustralia.fortunecity.com/rotative/reactor2.htm

Water (most reactors don't use heavy water) is more a moderator than a reflector, and its density is not going to change because of rotation because it's essentially incompressible. You aren't going to get the behavior you're after, and I don't think the neutrons are going to behave as a fluid anyway.

 

Why not just put a really dense material on the outside of the reactor vessel, which will act as a reflector?

Gamma ray lensing can be done though using an Alu plate with an array of exact size holes at exactly the correct distance apart and then these plates are stacked as a laminate allowing you to "Focus" gamma rays to a smaller point.

 

I`m not sure if the same could be done with neutrons though????

Gamma ray lensing can be done though using an Alu plate with an array of exact size holes at exactly the correct distance apart and then these plates are stacked as a laminate allowing you to "Focus" gamma rays to a smaller point.

 

I`m not sure if the same could be done with neutrons though????

 

Potentially, but this wouldn't reflect the neutrons back.

 

There are a couple of other ways of focusing neutrons:

http://www.ncnr.nist.gov/instruments/neutfocus.html

 

Also, though they are neutral, they have a magnetic moment, so you can focus them magnetically