The frequency of radiation used to sterilize things (like operating rooms in a hospital) is in the UVC range. UVC light is completely blocked by the earth's atmosphere: the UV light you are exposed to on the earth's surface is UVA and UVB.

Not at all. In fact, unlike power plants that use fossil fuels (like coal), fuel costs aren't a huge part of the cost of running a nuclear power plant anywhere, regardless of enrichment. (Caveat: nuclear power plants use relatively low fuel enrichments, like 5% or less. If you had an NPP with a very high enrichment, the cost could change, but NPPs don't need high enrichments.)

There aren't been any natural nuclear reactors any more. Over a billion years ago, the natural enrichment of uranium was much higher, because U-235 and U-238 have different half-lives.

The only place a natural reactor was ever thought to have operated was at Oklo, and it can't happen anywhere now.

The article you linked says they appear to grow, but is less clear about how much they actually do. It also says:

>Our ears are 90 percent grown by age six, and our noses are almost fully grown by the time we’re teens, but both can change shape and appear to enlarge as we age.

>NuScale and UAMPS attribute the construction cost increase to inflationary pressure on the energy supply chain, particularly increases in the prices of the commodities that will be used in nuclear power plant construction.

The biggest cost increases they list are for steel (shockingly high), but they also mention copper and electrical equipment. Plus, inflation is going up, which affects the cost of financing projects.

>Does the level of energy the neutron hit with, decide what new atoms and therefore how many neutrons are left over?

The kinetic energy of the incoming neutron can affect which pairs of atoms are produced. Higher energies generally result in more neutrons being released, which means that different fission products must result.

>Does this mean that when they enrich uranium/plutonium, reactors are run on lower energy?

Enrichment isn't done in a nuclear reactor. Typically, something like a centrifuge is used to separate the isotopes of uranium. U-235 is a little lighter than U-238, so the centrifuge can be used to get two output streams in which one has more U-235 than the input (higher enrichment) and the other has less U-235 (lower enrichment).

I think you might be asking about something like a breeder reactor, which can produce Pu-239 from U-238, or U-233 from Th-232. There have been very few of these, because some of the neutrons are used up in transmuting one element into another (by absorption without fission), which is a technical challenge. The usual technique is to use a fast reactor (high energy neutrons), so that there are more neutrons produced per fission.

There haven't been many breeder reactors because they are more complicated and expensive to build and operate than normal reactors. Uranium is pretty common and not that expensive, so we usually just mine it and use that. The uranium in power reactors is usually enriched a little. Natural uranium is 0.7% of the uranium you would find in the ground, and it is usually (but not always) enriched as high as 5% in nuclear power plants.

U-235 has 143 neutrons. When you strike it with one more neutron, the total is 144.
Fission usually splits one atom into two atoms, with some left over neutrons. There are a number of different pairs of atoms that are possible outcomes. Sometimes, the pairs of atoms produced add up to 141 neutrons, with three free neutrons left over, and sometimes they add up to 142 neutrons, with only two free neutrons left over.

For low-energy neutrons striking U-235, the chance of fission is about 6 times as high as absorbing the neutron and becoming U-236.

I was pretty surprised to see some of those (like U of Arizona, U of Utah) on the list, but not Brown or some other prestigious schools. I mean, UC Davis is a decent school, but one of the world's best?

I wouldn't say that uranium is scarce. Significant deposits of uranium are found on every continent (except Antarctica, so far). In a list of the elements that have more than trace quantities in the earth's crust, uranium appears around the middle.

It is certainly possible, and experimental reactors have been built to show that it could work.

Sixty or seventy years ago, people thought uranium was scarce, and that we would need breeder reactors (either on thorium/uranium or uranium/plutonium fuel cycles) to make nuclear power viable. However, breeder technology was never fully developed because uranium turned out to be a lot more plentiful and cheap than people expected. There just hasn't been any compelling reason to develop a new technology to make uranium when it's so much easier and cheaper to just dig it out of the ground.