5 ms·

I'm generally in favor of Nuclear, but they need to complete their whole-life planning before opening new plants. Presently, the status quo plan is to store nuc

I'm generally in favor of Nuclear, but they need to complete their whole-life planning before opening new plants. Presently, the status quo plan is to store nuclear waste at or near where it is generated in perpetuity. That's a pretty big unfunded liability in terms of risk management, security and maintenance. What is the future present value of managing a nuclear waste site for several hundred thousand years across risks we can't even imagine? That's a pretty big known unknown.

bootlooped 8y ago
I think the long term nuclear storage problem is at least partially, if not mostly or fully, a problem caused by political opposition. NIMBY essentially. They couldn't even get storage done at Yucca Mountain, and that's in the middle of the desert.
DennisP 8y ago
That's the status quo only because the government shut down its long-term storage facility, for which nuclear companies have already provided $46 billion. However, for the fast neutron reactors supported by this new law, long-term waste storage is less of a problem. 99% of our nuclear waste is U238 and transuranics, all of which are fissioned in fast reactors. The remaining 1% is fission products, which have much shorter half-lives. For those, the general idea is to encase them in glass blocks and bury them; they'll be back to the radioactivity of the original ore in 300 years.
- pcarolan 8y ago
  Are you saying that 99% of hazardous nuclear material is consumed in its own process? What does 'fissioned' mean in this context? Also can you comment on whether this requires more or less uranium ore inputs than prior generation reactors?
  - DennisP 8y ago
    "Fissioned" in any nuclear context means big atoms are split into small atoms. Natural uranium is 0.7% U235, and the rest U238. Only the U235 is fissionable by the slow neutrons in conventional reactors. For a nuclear plant, we have to enrich the uranium until it's at least 2% U235 (or a little more, depending on reactor design...the top is about 5%). The U238 in the reactor doesn't fission when hit by a neutron, but may absorb it and turn into plutonium, which is fissionable. About a third of a conventional reactor's energy output comes from fissioning plutonium. Other transuranics (elements heavier than uranium) are also produced in a conventional reactor as nuclei absorb neutrons without fissioning. The end product is a mixture of U238, unfissioned U235 and plutonium, other transuranics, and fission products. There's some fissionable material left over because some fission products absorb neutrons, poisoning the reaction; some countries, like France, "reprocess" this mixture to pull out the remaining fissionables. A fast reactor changes all this. In a conventional reactor, neutrons are purposely slowed down by materials like graphite and water. In a fast reactor, the neutrons from fission are left at the high energies they start with. These neutrons can fission U238 and all the transuranics. So the fast reactor can use all of the uranium, instead of just 1% percent of it (U235 plus some U238 that gets converted to plutonium). That does mean it only needs about 1% as much uranium input. A 1 GW coal plant uses a 100-car trainload of fuel every three days. A conventional nuclear plant uses an 18-wheeler load of fuel rods every 18 months. But a 1GW fast reactor uses just one ton of fuel per year, about the size of a beach ball. It can supply all the energy you need for your entire life, transportation included, from a piece of fuel the size of a golfball.
    - sandworm101 8y ago
      >> ...just one ton of fuel per year, about the size of a beach ball. Well, one hell of a hot beach ball. While the numbers are correct, that is how big one ton of uranium would be, for all practical purposes the fuel would be much bigger. The rods aren't 100% uranium. And they certainly aren't all transported in one spherical mass (boom). It would be moved a few kilos at a time, under escort. So there would still be lots of shipment/trucks transporting fuel to the reactor. It won't be pallet delivered by fedex ground every other year.
      - 8y ago

bootlooped 8y ago

I think the long term nuclear storage problem is at least partially, if not mostly or fully, a problem caused by political opposition. NIMBY essentially. They couldn't even get storage done at Yucca Mountain, and that's in the middle of the desert.

DennisP 8y ago

That's the status quo only because the government shut down its long-term storage facility, for which nuclear companies have already provided $46 billion. However, for the fast neutron reactors supported by this new law, long-term waste storage is less of a problem. 99% of our nuclear waste is U238 and transuranics, all of which are fissioned in fast reactors. The remaining 1% is fission products, which have much shorter half-lives. For those, the general idea is to encase them in glass blocks and bury them; they'll be back to the radioactivity of the original ore in 300 years.

pcarolan 8y ago
Are you saying that 99% of hazardous nuclear material is consumed in its own process? What does 'fissioned' mean in this context? Also can you comment on whether this requires more or less uranium ore inputs than prior generation reactors?
- DennisP 8y ago
  "Fissioned" in any nuclear context means big atoms are split into small atoms. Natural uranium is 0.7% U235, and the rest U238. Only the U235 is fissionable by the slow neutrons in conventional reactors. For a nuclear plant, we have to enrich the uranium until it's at least 2% U235 (or a little more, depending on reactor design...the top is about 5%). The U238 in the reactor doesn't fission when hit by a neutron, but may absorb it and turn into plutonium, which is fissionable. About a third of a conventional reactor's energy output comes from fissioning plutonium. Other transuranics (elements heavier than uranium) are also produced in a conventional reactor as nuclei absorb neutrons without fissioning. The end product is a mixture of U238, unfissioned U235 and plutonium, other transuranics, and fission products. There's some fissionable material left over because some fission products absorb neutrons, poisoning the reaction; some countries, like France, "reprocess" this mixture to pull out the remaining fissionables. A fast reactor changes all this. In a conventional reactor, neutrons are purposely slowed down by materials like graphite and water. In a fast reactor, the neutrons from fission are left at the high energies they start with. These neutrons can fission U238 and all the transuranics. So the fast reactor can use all of the uranium, instead of just 1% percent of it (U235 plus some U238 that gets converted to plutonium). That does mean it only needs about 1% as much uranium input. A 1 GW coal plant uses a 100-car trainload of fuel every three days. A conventional nuclear plant uses an 18-wheeler load of fuel rods every 18 months. But a 1GW fast reactor uses just one ton of fuel per year, about the size of a beach ball. It can supply all the energy you need for your entire life, transportation included, from a piece of fuel the size of a golfball.
  - sandworm101 8y ago
    >> ...just one ton of fuel per year, about the size of a beach ball. Well, one hell of a hot beach ball. While the numbers are correct, that is how big one ton of uranium would be, for all practical purposes the fuel would be much bigger. The rods aren't 100% uranium. And they certainly aren't all transported in one spherical mass (boom). It would be moved a few kilos at a time, under escort. So there would still be lots of shipment/trucks transporting fuel to the reactor. It won't be pallet delivered by fedex ground every other year.
    - 8y ago