So if you're reactor is on the scale of meters the neutron length scales, it looks like a thermal neutron, is in the order of a tenth of a meter.

As the application window expands or contracts, this space will scale in proportion to the length of the spring.

At its finest scale, we should be able to probe down the "Planck length" which measures 10-35 meters. But the GEO600 experiment detected noise at scales of less than 10-15 meters.