5 ms·

interesting topic, you'd perhaps do better reading the wikipedia article http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor http://en.wikipedia.org/w

by yread 13y ago

interesting topic, you'd perhaps do better reading the wikipedia article http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor they've found out about it because the uranium ore had smaller ratio of U235 than usual so they suspected that some of it might have been stolen for weapons. The reactor worked because U235 was more abundant naturally 2 billion years ago, now it has decayed more, so it's no longer possible. The reactor was periodically flooded with water which moderated the reaction. After 30 minutes of reaction all water would boil away. It is interesting for the study of nuclear waste disposal - this is 2 billion years old nuclear waste still sitting exactly in the place where it was created

Retric 13y ago
U235 is hardly waste it's fuel. Dangerous nuclear waste tends to contaminate useful things but the dangerous bits decay quickly which is what makes them dangerous in the first place. Read up on 'fuel reprocessing' and note that by simply leaving things alone for even just 100 years it becomes far cheaper to reprocess.
- ChuckMcM 13y ago
  In this case the nuclear "waste" in Oklo are the would be the same as you would get in any nuclear fuel process. It is the exact same process that created them. The upside is that the reactor only started and stopped and did not run continuously for long times apparently. The point about the viability of sequestration at Yucca Mountain is also interesting.
  - VLM 13y ago
    There is also an insightful bit that atoms don't split like legos, its more like a smooth graph, which has all kinds of implications. 1) The isotopic concentrations of waste from 2 billion years ago are about the same as you'd measure if you built it and lit it up today and then in theory let it sit around for two billion years, so to a zillion decimal places nothing has changed either in fission properties or decay rates in billions of years, which is interesting. 2) There exists no natural way to "kick" decay rates higher or lower. This being 2 billion years old, it's probably suffered thru billions of years of every crazy particle and field that can happen naturally in 2 billion years, none of which had any effect. So if you think there exists a way to speed up or slow down radioactive decay, its a minimum factor of two billion "un-natural" (more than two billion times the natural background of "techno-babble" radiation, or whatever) or perhaps most likely, it doesn't exist. So it appears to a zillion decimal places under varying natural conditions that nuclear decay rates are a constant. A pity, think how cool it would be to have a star trek like "thing" that decontaminates things. Or a controllable RTG that varies its power output by varying its decay rate. Or more negatively, if you could take a sphere of Co-60 the size of a softball, and increase its decay rate by a trillion or so, that would be a most impressive bomb. Or shine a magic disruptor beam at enemy troops or democracy activists or whatever and instantly all the C14 isotope in their body cooks off at the same time, that would be interesting.
    - wcoenen 13y ago
      > There exists no natural way to "kick" decay rates higher or lower. Some nuclei decay by electron capture, and their decay rates can be changed simply by bringing them in different chemical compounds. http://en.wikipedia.org/wiki/Electron_capture http://en.wikipedia.org/wiki/Electron_capture
ISL 13y ago
To a modern physicist, perhaps the most interesting thing about the Oklo reactor is that it gives us one of the biggest levers on the question "Have the laws of physics changed over time?" So far as anyone can tell, nuclear physics was the same back then as it is today.
- minikites 13y ago
  I didn't know this was in doubt, do you have any additional information on this debate? It sounds interesting.
  - maaku 13y ago
    It's not ind doubt so much as there is little intrinsic reason to support either side, and scant evidence. Maybe the laws of physics worked differently in the early universe -- how would you know? The answer of course is astronomical observations -- it's the only window into the past that we have, other than a few historical events like the OP, as the GP points out. But how do you interpret astronomical observations? By using the currently understood laws of physics, of course, so it becomes a bit of a circular argument. If you assume that certain constants change over time, that does help explain away current mysteries like inflation & dark energy, under some models. However too much deviation would contradict other observable evidence.
    - jsweojtj 13y ago
      > But how do you interpret astronomical observations? By using the currently understood laws of physics, of course, so it becomes a bit of a circular argument. One of the best ways to measure this is to use quasar absorption spectroscopy to probe the precise energy level spacing of atoms (like iron, magnesium, and so on) from billions of years ago with the energy level spacings found in the same atoms of today. If the fine-structure constant (for example) were different by some amount in the distant past, its effect is calculable -- and the spectroscopic signature of a different fine-structure constant is distinct from any other physical effect (redshift of the spectrum, etc.). There are some intriguing results that have come out over the past decade or so, with new information coming in all the time.

by yread 13y ago

Retric 13y ago

U235 is hardly waste it's fuel. Dangerous nuclear waste tends to contaminate useful things but the dangerous bits decay quickly which is what makes them dangerous in the first place. Read up on 'fuel reprocessing' and note that by simply leaving things alone for even just 100 years it becomes far cheaper to reprocess.

ChuckMcM 13y ago
In this case the nuclear "waste" in Oklo are the would be the same as you would get in any nuclear fuel process. It is the exact same process that created them. The upside is that the reactor only started and stopped and did not run continuously for long times apparently. The point about the viability of sequestration at Yucca Mountain is also interesting.
- VLM 13y ago
  There is also an insightful bit that atoms don't split like legos, its more like a smooth graph, which has all kinds of implications. 1) The isotopic concentrations of waste from 2 billion years ago are about the same as you'd measure if you built it and lit it up today and then in theory let it sit around for two billion years, so to a zillion decimal places nothing has changed either in fission properties or decay rates in billions of years, which is interesting. 2) There exists no natural way to "kick" decay rates higher or lower. This being 2 billion years old, it's probably suffered thru billions of years of every crazy particle and field that can happen naturally in 2 billion years, none of which had any effect. So if you think there exists a way to speed up or slow down radioactive decay, its a minimum factor of two billion "un-natural" (more than two billion times the natural background of "techno-babble" radiation, or whatever) or perhaps most likely, it doesn't exist. So it appears to a zillion decimal places under varying natural conditions that nuclear decay rates are a constant. A pity, think how cool it would be to have a star trek like "thing" that decontaminates things. Or a controllable RTG that varies its power output by varying its decay rate. Or more negatively, if you could take a sphere of Co-60 the size of a softball, and increase its decay rate by a trillion or so, that would be a most impressive bomb. Or shine a magic disruptor beam at enemy troops or democracy activists or whatever and instantly all the C14 isotope in their body cooks off at the same time, that would be interesting.
  - wcoenen 13y ago
    > There exists no natural way to "kick" decay rates higher or lower. Some nuclei decay by electron capture, and their decay rates can be changed simply by bringing them in different chemical compounds. http://en.wikipedia.org/wiki/Electron_capture http://en.wikipedia.org/wiki/Electron_capture

ISL 13y ago

To a modern physicist, perhaps the most interesting thing about the Oklo reactor is that it gives us one of the biggest levers on the question "Have the laws of physics changed over time?" So far as anyone can tell, nuclear physics was the same back then as it is today.

minikites 13y ago
I didn't know this was in doubt, do you have any additional information on this debate? It sounds interesting.
- maaku 13y ago
  It's not ind doubt so much as there is little intrinsic reason to support either side, and scant evidence. Maybe the laws of physics worked differently in the early universe -- how would you know? The answer of course is astronomical observations -- it's the only window into the past that we have, other than a few historical events like the OP, as the GP points out. But how do you interpret astronomical observations? By using the currently understood laws of physics, of course, so it becomes a bit of a circular argument. If you assume that certain constants change over time, that does help explain away current mysteries like inflation & dark energy, under some models. However too much deviation would contradict other observable evidence.
  - jsweojtj 13y ago
    > But how do you interpret astronomical observations? By using the currently understood laws of physics, of course, so it becomes a bit of a circular argument. One of the best ways to measure this is to use quasar absorption spectroscopy to probe the precise energy level spacing of atoms (like iron, magnesium, and so on) from billions of years ago with the energy level spacings found in the same atoms of today. If the fine-structure constant (for example) were different by some amount in the distant past, its effect is calculable -- and the spectroscopic signature of a different fine-structure constant is distinct from any other physical effect (redshift of the spectrum, etc.). There are some intriguing results that have come out over the past decade or so, with new information coming in all the time.