On the contrary ...
The planted particle benefits from being larger than the typical nickel fuel particle as part of a plan which makes it likely to be tested. Having enriched isotope already inside the tube prior to the loading is not enough, and you want to make sure it gets noticed at the unloading. That is - in order to make certain that the salted particle gets analyzed, the obvious strategy is to make it conspicuous and easy to pick up with tweezers, which of course means it must be larger. From: Axil Axil The Ni62 ash particle is unlikely to be a plant because it is a huge paticle(600 by 1000 microns) far larger than any fuel particle in the fuel load and it was melted onto the surface of the center of alumina tube. Ø C’mon guys the Lugano report of that 62Ni is an impossible bit of data, there is no way that only 62Ni would be recorded as it would surely not be so pure as to not show minor tramp amounts of other nickel isotopes. That number is bogus by gross error or intent. Get over it, just toss that piece of BS out the window into the garden where it might do some good.