Comments on: Nature’s Nuclear Reactors

By: JarvisLoop

JarvisLoop — Sat, 16 May 2020 02:43:55 +0000

Doesn’t bode well for our efforts to store spent nuclear fuel.

By: Arkadia Moon

Arkadia Moon — Mon, 03 Aug 2015 16:07:42 +0000

The distinction between “PROMPT CRITICAL” and “CRITICAL” offered at the beginning of the thread is not exactly correct. “Prompt” and “delayed” are two kinds of criticality that happen within a nuclear reactor, with the obvious meaning: whether neutrons cause fissions immediately or with a small delay. But this has little to do with whether a mass of fissile material will explode. If prompt criticality alone were the threshold of explosion, nuclear reactors would be possible to construct, but any attempt to start them up would immediately (on a timescale of milliseconds) lead to very exciting results — exciting in this case having a very special meaning, and not a pleasant one to any normal human being.

Critical mass is the mass of a fissile material that supports a self-sustaining nuclear reaction. In a less than critical mass, the ongoing nuclear reaction will peter out over time. In a more than critical mass, the reaction will accelerate, heating the fissile material. The critical mass is not a fixed amount; whether a given mass is critical or not is influenced by its density, its geometry, the presence or absence of a moderator, and the presence or absence of a neutron-absorbing “reactor poison” like boron.

Nuclear explosions are caused by a barely-short-of-critical mass of fissile material being intensely compressed to a very high density at which the same mass is a long, long, long way past critical. This is not easy to achieve, even for technologically sophisticated humans. In order to work, nuclear explosives have to be engineered to incredibly demanding standards that make the finest Swiss watches look like flint knives by comparison. Manufacturing flaws invisible to the unaided eye are enough to make them fizzle out.

By: TravelBugBrit

TravelBugBrit — Wed, 20 Oct 2010 06:09:01 +0000

Agreed

By: Mullin

Mullin — Tue, 28 Jul 2009 01:08:36 +0000

Wow, great post Hermes.
These are the types of comments that actually make the site better, hopefully not your last post.

By: Hermes

Hermes — Mon, 27 Jul 2009 18:13:09 +0000

(better late than never) – In reading over these comments I can’t help but notice a fairly general misunderstanding of the difference between this phenomenon and intentionally built reactors. I see a lot of speculation regarding “how do they know…”, “but what about…”, etc.
Here is a link to an excellent and detailed article from Scientific American magazine a while back written by those directly involved in the research:
http://www.scientificamerican.com/article.cfm?id=ancient-nuclear-reactor
If you are interested in the science of this, it is a fascinating story about how they figured all this out. Of note: The total power output this reactor was “say, enough to run a few dozen toasters” (had it been harnessed to make elctricity, and if there were toasters a billion years ago) – this is no Chernobyl.
The by-products are no threat, since the longest-lasting radioactive by-products from a U-235 reaction are dangerous only for about 100,000 years, so while that time frame may pose an issue for reactors operating within our lifetimes, 10 times that period oftime has elapsed since these natural reactors stopped.
As for the possibility of using such things to make electricity, that ship has sailed. the proportion of U-235 among all uranium is the same everywhere in our solar system (except at the Oklo sites – where there is less of it, because the natural reaction used it up), and that proportion keeps decreasing over time (due to natural radioactive decay into other isotopes that can’t sustain a reaction). In the current era, the proportion is already too small for this to happen again. That is why power plants have to use “enriched” uranium, which is uranium processed to increase its U-235 proportion so that it can work.

Perhaps more info than anyone wanted, but hey, this is my first post here (bash away!)

By: Jospec5Star

Jospec5Star — Sat, 17 Jan 2009 22:58:31 +0000

Damn interesting indeed. I would say that prior to finding this site I was in no way interested in radioactive material or the like. However the writing style and stories themselves have completely changed that for me. Excellent job DI staff!

By: ValiantDefender

ValiantDefender — Tue, 25 Nov 2008 19:22:50 +0000

[quote]NastyGash said: “This storry could not possible be factal since the EARTH is ONLY 10,000 (aprox) year’s old. Dont you guy’s reed the Bibble?”[/quote]

I know you’re merely poking fun but a few questions about this. According to the Doctrine of my church, the Earth was Organized from materials. In other words, god didn’t “create” as in poof into existance, a planet. Rather, took of raw materials and created the earth. Much like a baker “makes” a cake. The cake is only a few minutes old, all toasty warm and moist. But the wheat used to make it 30 years old (there is some 30 year old wheat in my basement…I know, it has no nutritional value left). So, while the religious right contends the Earth is only 10k years old, the materials used to make it may be much, much older. This resolves many divergences between the religious point of view and the scientific point of view.

I’m not saying you have to agree with me or that my view supercedes yours. Just asking for common courtesy.

I think the article is great. I wish the site was still adding new stuff. It seems like the book is now the 100% focus. Dunno why,lol. It probably makes money =)

By: Nick

Nick — Thu, 25 Sep 2008 16:09:08 +0000

………maybe 400 million earth years ago, (just b4 dinosaurs became), this bygone civilization that had nuclear energy, & whatnot, blow themselves up in war or a big accident like a gigantic melt-down occurred, after this happened, years later or 100’s or 1000’s years later, reptiles became bigger becuase of radiation & there we have why dinosaurs were so large! just a thought, ( like the movie Godzilla) the intelligent beings that ruled were knocked down to just a few 100 after this event, (& lived underground) & were made sterile, & died out.

By: Mirage_GSM

Mirage_GSM — Tue, 05 Aug 2008 11:38:16 +0000

[quote]flstc2000 said: “Actually, this Earth that was created 10,000 years ago could have been formed from pieces of existing matter that were indeed millions and or billions of years old.”[/quote]
Cool! I can imagine God sitting there with a jigsaw of parts, clobbering together earth: “Hmm. Gabon… That’s the thing with tha old nuclear reactor I built as a kid. Let’s put it between Cameroon and Congo!
And regarding possible remaining nuclear waste: After 1,5 billion years you could probably handle a spent fuel rod from an atomic power plant with your bare hands without any ill effects.

By: Nezbitz

Nezbitz — Thu, 07 Feb 2008 03:55:00 +0000

[quote]Kao_Valin said: “Yes, you better correct yourself. The Bibble says its 20 thousand years old, because the Bibble is twice as good as the Bible. Older and wiser the Earth be, I say!”[/quote]

Two B or not Two B. That is the question :P