During my playthrough of EI (0.4.2, haven't checked whether 0.5 fixed this) I noticed that my high-temp reactors were generating a neutron flow field even when they weren't operating, due to lack of heat input.

This can be abused to charge neutron containers, like so:
- build a high-temp reactor (or several), fill it with water
- build a single normal nuclear reactor as a heat source
- heat up the nuclear reactor to max temp, heating the HT reactors to over 925C (one U235 fuel cell should be enough)
- remove the nuclear reactor and any pipes/heat pipes or other supporting infrastructure
- insert a single fuel cell into HT reactor (thorium seems to be the cheapest overall, but any should work)
- build neutron collectors around the HT reactor (I can fit 8 directly adjacent)
- charge neutron containers with no extra cost
- profit!