Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Oklo, the Earth's Two-billion-year-old only Known Natural Nuclear Reactor (2018)

iaea.org

Post reply on HN
Print view View original

81–90 of 124 posts

Re: Oklo, the Earth's Two-billion-year-old only Known Natural Nuclear Reactor (2018)

#81

Post by Manuel_D »

bobmcnamara wrote: post #80
Manuel_D wrote: post #62

Earlier quoted context omitted.

You can dig in bedrock that has no groundwater. Furthermore, naturally occurring uranium exists in groundwater and needs to be filtered out in places where levels exceed safe limits. So it's not like burying waste is creating a new problem: https://www.kqed.org/stateofhealth/120396/uranium-contaminat...

Heavy metal and radiological exposure is not a boolean safe/unsafe.

Sure, but the important point is that we already have infrastructure deployed to detect and remove uranium from the water supply on account of naturally occurring uranium.

Re: Oklo, the Earth's Two-billion-year-old only Known Natural Nuclear Reactor (2018)

#82

Post by kretaceous »

philipkglass wrote: post #16
Aardwolf wrote: post #8

> All natural uranium today contains 0.720% of U-235. That's related to the material of our solar system all coming from the same supernova explosion or similar, right? Does this apply to our entire milky way or just the solar system? What if parts collided with material of _other_ origins and some of that is on Earth, then there could be different mixes, right?

It's related to how long ago the uranium was formed: https://world-nuclear.org/information-library/nuclear-fuel-c... We can calculate the abundances of U-235 and U-238 at the time the Earth was formed. Knowing further that the production ratio of U-235 to U-238 in a supernova is about 1.65, we can calculate that if all of the uranium now in the solar system were made in a single supernova, this event must have occurr…

I don't understand so bear with me.

If the Uranium came from multiple supernovae, then why is it shocking that earth has different concentrations of U235? Moreover, how is it proof of a past fission reaction?

What if that "part" of U235 came from a separate supernova which is a little older and some more of its U235 had already decayed?

Re: Oklo, the Earth's Two-billion-year-old only Known Natural Nuclear Reactor (2018)

#83

Post by keepamovin »

philipkglass wrote: post #16
Aardwolf wrote: post #8

> All natural uranium today contains 0.720% of U-235. That's related to the material of our solar system all coming from the same supernova explosion or similar, right? Does this apply to our entire milky way or just the solar system? What if parts collided with material of _other_ origins and some of that is on Earth, then there could be different mixes, right?

It's related to how long ago the uranium was formed: https://world-nuclear.org/information-library/nuclear-fuel-c... We can calculate the abundances of U-235 and U-238 at the time the Earth was formed. Knowing further that the production ratio of U-235 to U-238 in a supernova is about 1.65, we can calculate that if all of the uranium now in the solar system were made in a single supernova, this event must have occurr…

This is excellent. I love your depth of knowledge in this subject. I learned a lot from this clear comment.

Re: Oklo, the Earth's Two-billion-year-old only Known Natural Nuclear Reactor (2018)

#85

Post by datatrashfire »

legitster wrote: post #25

Richard Rhodes brought this up in an interview. He made it a point for critics who say nuclear waste can't be safely disposed of through burial. Well, we have pretty good natural evidence that nuclear fission products can remain buried and undisturbed for a pretty long time!

Except for Finland nobody has actually created a long term geologic disposal site. Like so many problems, the issue is dominated by political coordination, not physical limits.

Re: Oklo, the Earth's Two-billion-year-old only Known Natural Nuclear Reactor (2018)

#86

Post by rkagerer »

glompers wrote: post #48
joe_the_user wrote: post #38

Earlier quoted context omitted.

I don't disagree that nuclear waste can be disposed of safely under good conditions[1]. But I think a fallacy to claim that natural phenomena should inherently be considered "environmentally safe" in human terms. There are coal seam fires that have been going on for centuries and the pollution of these is just as bad as the pollution generated by human created coal mine fires (and that's truly awful, a significant so…

> There are coal seam fires that have been going on for centuries and the pollution of these is just as bad as the pollution generated by human created coal mine fires (and that's truly awful, a significant source of carbon pollution). Has CO2 fire suppression been unsuccessfully attempted in these seams? Since nobody is underground and we know how to inject CO2 into underground deposits at various pressures, it seem…

I have a question on rotary steerable drilling. I gather we're only talking about a degree or less of deflection on the steering head. But how does the km's long rest of the stack behind the head snake through the curves? Is it like rail cars, with a little bit of angular bend allowed at the connection of each segment?

Re: Oklo, the Earth's Two-billion-year-old only Known Natural Nuclear Reactor (2018)

#87

Post by Manuel_D »

bobmcnamara wrote: post #79
Manuel_D wrote: post #53

Earlier quoted context omitted.

2) I asked about waste buried in the ground, not in transit. 3) if a waste barrel explodes, somehow, underground how does the waste make it's way through a mile of bedrock? 4) Again, how does a fire bring the wast up through a mile of bedrock? 5) This is just a vague statement. 6) So the concern is that future society will forget that this is a waste site, mine a mile deep and retrieve waste, and never figure out tha…

2/3/4) Please see historical data above regarding three burial sites. Practically today, these sites are built by mining. 5) Industry term. Operationalizing any significant system will involve human beings, and with it their workplace culture. You can read about it here: https://mshasafetyservices.com/fostering-a-culture-of-safety... . Many mining hese were written in blood. 6) No, the concern is that people may be h…

The example you linked above is disposal of nuclear weapons waste, not nuclear power generation. This isn't even the same material (plutonium vs uranium). Sure, there were plenty of bad nuclear waste disposal programs in the early cold war, but this has quite limited relevance to nuclear power generation.

And again, the question remains how people may be harmed by nuclear waste buried in bedrock half a kilometer underground? A even if a buried waste canister spontaneously combusts, how does the waste make it through half a kilometer of rock? In order for an unknown harm to occur, harm first has to actually occur.

This kind of appeal to an unknown harm can be used to arbitrarily object to anything.

"We need to stop building solar panels and wind turbines because they have the potential to cause an unknown harm. You disagree that these systems have the potential to cause harm? Well of course you can't know this, because it's an unknown harm that we're trying to prevent. How can you possibly disprove the existence of an unknown harm?"

Re: Oklo, the Earth's Two-billion-year-old only Known Natural Nuclear Reactor (2018)

#88

Post by ReaLNero »

kretaceous wrote: post #82
philipkglass wrote: post #16

Earlier quoted context omitted.

It's related to how long ago the uranium was formed: https://world-nuclear.org/information-library/nuclear-fuel-c... We can calculate the abundances of U-235 and U-238 at the time the Earth was formed. Knowing further that the production ratio of U-235 to U-238 in a supernova is about 1.65, we can calculate that if all of the uranium now in the solar system were made in a single supernova, this event must have occurr…

I don't understand so bear with me. If the Uranium came from multiple supernovae, then why is it shocking that earth has different concentrations of U235? Moreover, how is it proof of a past fission reaction? What if that "part" of U235 came from a separate supernova which is a little older and some more of its U235 had already decayed?

There were unusual elements characteristic of the decay chain following a fission.

After a U-235 atom undergoes fission, one of the outcomes is it releases Barium and Krypton (and some neutrons), which then eventually decay to stable/semi-stable elements. If one of those stable elements is common in the deposit but otherwise rare naturally, it would point to a nuclear reaction having occurred.

Also note that the U-235 decay chain generally looks different from the decay chain following a fission reaction of U-235.

Re: Oklo, the Earth's Two-billion-year-old only Known Natural Nuclear Reactor (2018)

#89

Post by Alupis »

jvanderbot wrote: post #59
b800h wrote: post #3

The Oklo region has now-exhausted Uranium deposits. From Wikipedia: "Some of the mined uranium was found to have a lower concentration of uranium-235 than expected, as if it had already been in a nuclear reactor. When geologists investigated they also found products typical of a reactor. They concluded that the deposit had been in a reactor: a natural nuclear fission reactor, around 1.8 to 1.7 billion years BP – in t…

100 kW for a few hundred thousand years is basically the best sales pitch for nuclear power I've ever heard. Even of "just" heat output.

Its impressive the amount of clean, cheap energy that's been locked away because of fearmongering tales from well before many were even alive.

Re: Oklo, the Earth's Two-billion-year-old only Known Natural Nuclear Reactor (2018)

#90

Post by bobmcnamara »

Manuel_D wrote: post #81
bobmcnamara wrote: post #80

Earlier quoted context omitted.

Heavy metal and radiological exposure is not a boolean safe/unsafe.

Sure, but the important point is that we already have infrastructure deployed to detect and remove uranium from the water supply on account of naturally occurring uranium.

That's...not a very good point.
Post reply on HN