3 ms·

That’s why we should be using reprocessed MOX fuel not once through and bury.

PaulHoule 4y ago
Exactly. The plutonium in nuclear waste is not waste, it's a fuel at least as valuable as ²³⁵U. Reprocessing not only reuses the Pu, with fast reactors it can be used to convert almost all ²³⁸U to ²³⁹Pu which is a valuable fuel. This allows us to get 60x more energy out of natural uranium -- we can stop enriching uranium and fuel our civilization for hundreds of years based on the "waste" that is already above. The waste that remains after reprocessing in a fast cycle are fission products that will decay so much in 1000 years that the waste is less radioactive than the original uranium ore.
- Schroedingersat 4y ago
  What's the concentration of Pu in the output of a modern high burnup reactor? What is the ratio of that to the concentration of fissile products needed for fuel? Cs137 and Sr90 lasting 'mere' centuries isn't helping your case any. Especially when existing MOX programs spill more than Fukushima and TMI combined as standard operating procedure.
  - FredPret 4y ago
    When working on a timescale of 10E2 or 10E3 years, it seems practical to me to bury it in a sealed drum in a concrete cube inside a stable mountain. With larger timescales, my understanding is that the mountain itself might disrupt the cube + drums, opening Pandora’s box. Perhaps an actual geologist can weigh in and correct me.
    - PaulHoule 4y ago
      People have built structures on Earth that have lasted 1000 years so that is in our experience. It seems likely that people will still be able to read English in the next 1000 years. It is in our realm of experience. 100,000 not so much. All kinds of things can go wrong. It is expected for instance that as Yucca Mountain cools down water will infiltrate. Uranium is water soluble so some will migrate in the direction of Death Valley. Uranium is toxic the same way lead and mercury are and that is more dangerous than the radiotoxicity of uranium. A "once through" repository will contain valuable plutonium and uranium. People might want to drill into it 10,000 years from now because they want to use it as a power source or to make nuclear explosives. For that matter we could change our minds and decide we want to recycle the waste in Yucca Mountain after all so we have to be able to retrieve the waste in the first 100 years. A waste repository used for fission products can use highly secure but difficult to reverse approaches such as encapsulation in a salt dome or burial in areas at sea where sedimentation is taking place where waste would get deeper and deeper year after year and be blocked from migration by the tendency of ions to get trapped in clay.
      - FredPret 4y ago
        I like the sedimentation plan. After sedimentation it’ll get pushed down below the crust right?
philipkglass 4y ago
That was originally the plan for surplus weapons plutonium. In 2007 the United States started building a MOX facility at Savannah River for turning the old weapons plutonium into power reactor fuel. Its cost and time to completion ballooned far beyond original estimates and it was ultimately canceled. "Cost estimate for MOX facility at Savannah River Site swells to $47.5 billion" https://www.augustachronicle.com/story/news/2015/04/22/cost-estimate-mox-facility-savannah-river-site-swells-475-billion/14371088007/ https://www.augustachronicle.com/story/news/2015/04/22/cost-... "US MOX facility contract terminated" https://world-nuclear-news.org/Articles/US-MOX-facility-contract-terminated https://world-nuclear-news.org/Articles/US-MOX-facility-cont... https://en.wikipedia.org/wiki/Savannah_River_Site#MOX_Fuel_Fabrication_Facility https://en.wikipedia.org/wiki/Savannah_River_Site#MOX_Fuel_F...

Exactly. The plutonium in nuclear waste is not waste, it's a fuel at least as valuable as ²³⁵U. Reprocessing not only reuses the Pu, with fast reactors it can be used to convert almost all ²³⁸U to ²³⁹Pu which is a valuable fuel. This allows us to get 60x more energy out of natural uranium -- we can stop enriching uranium and fuel our civilization for hundreds of years based on the "waste" that is already above. The waste that remains after reprocessing in a fast cycle are fission products that will decay so much in 1000 years that the waste is less radioactive than the original uranium ore.

Schroedingersat 4y ago
What's the concentration of Pu in the output of a modern high burnup reactor? What is the ratio of that to the concentration of fissile products needed for fuel? Cs137 and Sr90 lasting 'mere' centuries isn't helping your case any. Especially when existing MOX programs spill more than Fukushima and TMI combined as standard operating procedure.
- FredPret 4y ago
  When working on a timescale of 10E2 or 10E3 years, it seems practical to me to bury it in a sealed drum in a concrete cube inside a stable mountain. With larger timescales, my understanding is that the mountain itself might disrupt the cube + drums, opening Pandora’s box. Perhaps an actual geologist can weigh in and correct me.
  - PaulHoule 4y ago
    People have built structures on Earth that have lasted 1000 years so that is in our experience. It seems likely that people will still be able to read English in the next 1000 years. It is in our realm of experience. 100,000 not so much. All kinds of things can go wrong. It is expected for instance that as Yucca Mountain cools down water will infiltrate. Uranium is water soluble so some will migrate in the direction of Death Valley. Uranium is toxic the same way lead and mercury are and that is more dangerous than the radiotoxicity of uranium. A "once through" repository will contain valuable plutonium and uranium. People might want to drill into it 10,000 years from now because they want to use it as a power source or to make nuclear explosives. For that matter we could change our minds and decide we want to recycle the waste in Yucca Mountain after all so we have to be able to retrieve the waste in the first 100 years. A waste repository used for fission products can use highly secure but difficult to reverse approaches such as encapsulation in a salt dome or burial in areas at sea where sedimentation is taking place where waste would get deeper and deeper year after year and be blocked from migration by the tendency of ions to get trapped in clay.
    - FredPret 4y ago
      I like the sedimentation plan. After sedimentation it’ll get pushed down below the crust right?

philipkglass 4y ago

That was originally the plan for surplus weapons plutonium. In 2007 the United States started building a MOX facility at Savannah River for turning the old weapons plutonium into power reactor fuel. Its cost and time to completion ballooned far beyond original estimates and it was ultimately canceled. "Cost estimate for MOX facility at Savannah River Site swells to $47.5 billion" https://www.augustachronicle.com/story/news/2015/04/22/cost-estimate-mox-facility-savannah-river-site-swells-475-billion/14371088007/ https://www.augustachronicle.com/story/news/2015/04/22/cost-... "US MOX facility contract terminated" https://world-nuclear-news.org/Articles/US-MOX-facility-contract-terminated https://world-nuclear-news.org/Articles/US-MOX-facility-cont... https://en.wikipedia.org/wiki/Savannah_River_Site#MOX_Fuel_Fabrication_Facility https://en.wikipedia.org/wiki/Savannah_River_Site#MOX_Fuel_F...