The uranium fuel rods in nuclear reactors are too hazardous for use in atomic weapons.

The uranium fuel rods in nuclear reactors are too massive and almost impossible to transport during military use.

Without further treatment, uranium fuel rods in nuclear reactors will explode during transportation if used for atomic weapons.

Without further processing, the U-235 enrichment of uranium fuel rods in nuclear reactors is not high enough to be fit for use in atomic weapons.