Has any determination been made on whether it would be desirable to separate the isotopes of Boron so only pure B11 could be used.  Presumably the gas centrifuge would be a possible device for this, but in the case of U235/U238 separation, it is an expensive and time consuming process.  Would this even be necessary to achieve peak efficiency or desirable to avoid side reactions which could create neutrons?

Separating the isotopes of Boron is much easier than Uranium because the ratio of the mass differences is much larger.

Boron is used extensively in fission power plants as a neutron absorber - here B-10 +n -> Li-7 +He-4.  Also there are well established industrial processes for purifying and enriching Boron for this purpose (where they want the B-10) so the ‘depleted’ B-11 is already there as a byproduct.

B-11 is also used in preference to B-10 in electronics, especially in high radiation environments like satellites.  Where you want to avoid the B-10 +neutron reaction at best flipping bits or worse permanently damaging the semiconductor.

James