3 ms·

> They’re digging one mile (1.6 km) holes dropping low enriched nuclear fuel to the bottom, and filling them with water. > When the fuel is used up, they can l

by Someone 4mo ago

> They’re digging one mile (1.6 km) holes dropping low enriched nuclear fuel to the bottom, and filling them with water. > When the fuel is used up, they can leave it where it is since it’s below the water table. To do both, they’ll have to guarantee that that column of water stays isolated from groundwater for a long time after the fuel is used up. Reading https://www.deepfission.com/faq https://www.deepfission.com/faq, they answer that question with “Importantly, the mile-deep column of water in the borehole is expected to provide the pressure conditions required for safe reactor operation. Water within the borehole is also intended to contribute to the reactor’s thermal management system”. So, what do they do if their drill hole starts leaking, and they lose pressure? and “Our boreholes are expected to be lined with multiple layers of casing, including steel casing and concrete intended to maintain structural integrity and isolate surrounding geological formations” I don’t think those are good answers. They say what they want to do, but almost nothing about how they’ll do that, and try to avoid making hard statements on the what by using “is expected” and “is intended”.

cucumber3732842 4mo ago
>I don’t think those are good answers. Steel and concrete are what we use above ground so..... >They say what they want to do, but almost nothing about how they’ll do that, and try to avoid making hard statements on the what by using “is expected” and “is intended”. They say nothing about how because those are trivial problems in the well (and oil) drilling industry.
- AnimalMuppet 4mo ago
  We use steel and concrete. We don't usually expect them to last 10,000 years, though.
- bronson 4mo ago
  > those are trivial problems in the well (and oil) drilling industry. Ah yes, an industry well known for its adherence to safety standards and never having surprising blowouts.
Asooka 4mo ago
> To do both, they’ll have to guarantee that that column of water stays isolated from groundwater for a long time after the fuel is used up. I wonder if just letting the water gradually dissolve the uranium might not be fine, actually. If it is done far from wells and rivers used for drinking water, then the small amount of radioactive minerals that slowly seep out might not pose a danger. I can't find any studies to back it up, but I imagine there are places on Earth at which enriched uranium buried 1.6km underground poses no threat. I am no expert, so I would love to hear what others think.
- leonidasrup 4mo ago
  Of the all the radioactive elements in a nuclear reactor, uranium is one of the least dangerous (is very weakly radioactive, but it's toxic, it's a heavy metal). It's all the radioactive fission products (many have short half-life and in process of decay produces lot of ionizing radiation) and trans-uranic elements (because they have very long half-life and produce a bit small bits of ionizing radiation for very long time). One possible of measure of danger is median lethal dose LD50: Uranium LD50 in mice 114 mg/kg (about the same as Cocaine LD50 96 mg/kg) Plutonium LD50 in dog 320 μg/kg Caesium-137 LD50 245 μg/kg Polonium-210 LD50 10 ng/kg (estimated) https://en.wikipedia.org/wiki/Median_lethal_dose https://en.wikipedia.org/wiki/Median_lethal_dose There are places underground with high concentration of uranium, they are called uranium ore and sometimes they are mined for uranium. "The deposit is located at depth of 450 m (1,480 ft), surrounded by and isolated within a layer of water-impermeable illite-chlorite clay, within the Athabasca Sandstone formation. Its age is estimated to be 1.3 billion years. Due to natural containment and lack of any traces of radioactive elements on the surface, the deposit is used as an example of an effective natural deep geological repository." https://en.wikipedia.org/wiki/Cigar_Lake_mine https://en.wikipedia.org/wiki/Cigar_Lake_mine
  - JumpCrisscross 4mo ago
    On the upside, the half life of those byproducts is measured in days to decades (15 years for Pu-241, 88 for Pu-238, 30 for Cs-137 and 139 days for Po-210).
quotemstr 4mo ago
What a waste of perfectly good reprocessing input. "Spent" convention nuclear fuel retains 95% of its energy. Discarding "spent" fuel is a shamefully profligate energy practice we can get away with because we're using not nearly enough nuclear power, making and virgin fissiles are dirt cheap.
- pseudosaid 4mo ago
  they just recently nailed converting spent fuel into tritium

by Someone 4mo ago

cucumber3732842 4mo ago

>I don’t think those are good answers. Steel and concrete are what we use above ground so..... >They say what they want to do, but almost nothing about how they’ll do that, and try to avoid making hard statements on the what by using “is expected” and “is intended”. They say nothing about how because those are trivial problems in the well (and oil) drilling industry.

AnimalMuppet 4mo ago
We use steel and concrete. We don't usually expect them to last 10,000 years, though.
bronson 4mo ago
> those are trivial problems in the well (and oil) drilling industry. Ah yes, an industry well known for its adherence to safety standards and never having surprising blowouts.

Asooka 4mo ago

> To do both, they’ll have to guarantee that that column of water stays isolated from groundwater for a long time after the fuel is used up. I wonder if just letting the water gradually dissolve the uranium might not be fine, actually. If it is done far from wells and rivers used for drinking water, then the small amount of radioactive minerals that slowly seep out might not pose a danger. I can't find any studies to back it up, but I imagine there are places on Earth at which enriched uranium buried 1.6km underground poses no threat. I am no expert, so I would love to hear what others think.

leonidasrup 4mo ago
Of the all the radioactive elements in a nuclear reactor, uranium is one of the least dangerous (is very weakly radioactive, but it's toxic, it's a heavy metal). It's all the radioactive fission products (many have short half-life and in process of decay produces lot of ionizing radiation) and trans-uranic elements (because they have very long half-life and produce a bit small bits of ionizing radiation for very long time). One possible of measure of danger is median lethal dose LD50: Uranium LD50 in mice 114 mg/kg (about the same as Cocaine LD50 96 mg/kg) Plutonium LD50 in dog 320 μg/kg Caesium-137 LD50 245 μg/kg Polonium-210 LD50 10 ng/kg (estimated) https://en.wikipedia.org/wiki/Median_lethal_dose https://en.wikipedia.org/wiki/Median_lethal_dose There are places underground with high concentration of uranium, they are called uranium ore and sometimes they are mined for uranium. "The deposit is located at depth of 450 m (1,480 ft), surrounded by and isolated within a layer of water-impermeable illite-chlorite clay, within the Athabasca Sandstone formation. Its age is estimated to be 1.3 billion years. Due to natural containment and lack of any traces of radioactive elements on the surface, the deposit is used as an example of an effective natural deep geological repository." https://en.wikipedia.org/wiki/Cigar_Lake_mine https://en.wikipedia.org/wiki/Cigar_Lake_mine
- JumpCrisscross 4mo ago
  On the upside, the half life of those byproducts is measured in days to decades (15 years for Pu-241, 88 for Pu-238, 30 for Cs-137 and 139 days for Po-210).

quotemstr 4mo ago

What a waste of perfectly good reprocessing input. "Spent" convention nuclear fuel retains 95% of its energy. Discarding "spent" fuel is a shamefully profligate energy practice we can get away with because we're using not nearly enough nuclear power, making and virgin fissiles are dirt cheap.

pseudosaid 4mo ago
they just recently nailed converting spent fuel into tritium