Similarly, for plutonium based bombs, reactors will naturally produce plutonium. Typically reactors produce plutonium 239 (fissable) which then absorbs more neutrons to become plutonium 240. Making the mixture not weapons grade. However, if you swap out the fuel rods frequently enough you can increase the purity of Pu239 to weapons grade.
Essentially, nuclear waste from power plants is not weapons grade, but the infrastructure of the plant and supply chain is essentially the same infrastructure you would use to create weapons grade materials.
Also, even none weapons grade materials can ge used in dirty bombs.
Plus, once enough fuel has been accumulated, a breeder reactor can be set up to generate the necessary Pu238 & Pu239. This is something a nuclear power would want to do for legitimate purposes because plutonium yields are far higher than uranium.
So in some ways, yes, nuclear reactors make it "that easy" to manufacture nuclear weapons. Especially plutonium-based weapons. There's still the work needed to create a weapon from the source material, but that's an easier problem to solve.
> Most nuclear reactors that produce electricity only require fuel that is enriched to between 3-5% U-235.
> This fuel does not represent a proliferation threat primarily because of the critical mass issue — the amount of material necessary to maintain a self-sustaining neutron chain reaction. If the level of enrichment is low, then it holds that the amount of the material must go up in order for a chain reaction to be sustained. The size can quickly become impractical for weapons delivery, so low enriched uranium (LEU) is not a threat.
> Highly enriched uranium (HEU) is anything enriched above 20% and weapon-grade uranium is commonly considered to have been enriched above 90% U-235. However, some research reactors use 90% enriched U-235 to produce medical isotopes, so there are civilian applications for this fuel too.
From: https://armscontrolcenter.org/uranium-enrichment-for-peace-o...