Recent comments in /f/askscience

TheLostHippos t1_j4q7ykd wrote

Reply to comment by Tasty-Army200 in Which rodents have the largest territory? by WombatusMighty

Yes, but did you know most gophers are actually solo in their burrows outside of breeding?

While you may find 60 gophers in an acre, most are living in individual burrows.

"Gophers usually live alone within their burrow system, except when females are caring for their young or during breeding season. Gopher densities can be as high as 60 or more per acre in irrigated alfalfa fields or in vineyards."

https://ipm.ucanr.edu/home-and-landscape/pocket-gophers/pest-notes/?src=302-www&fr=3782#:~:text=Gophers%20usually%20live%20alone%20within,alfalfa%20fields%20or%20in%20vineyards.

"Habitat
Because gophers are territorial and more comfortable being alone, each of them stays inside their own burrow. Male and female gophers only dwell on each other’s places during mating season. Though some gophers can actually breed all throughout the year, most of them gather around summer and springtime to breed.
Soft, muddy soil
Edible plant in the surrounding"

http://www.minneapoliswildlife.com/gopher.html

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PlutoniumChemist t1_j4q3tia wrote

Reply to comment by Dravous in If nuclear fission in U-235 causes the atom to be split into 2 smaller atoms (such as Kr-92 and Ba-141) then how is it that U-236 is produced as waste since the U-235 was just split into smaller peices? by Ian98766

This is a great question, and yes. 239U has a half life of less than 30 minutes and will radioactively decay into 239Np. This happens because there are too many neutrons in the 239U nucleus, so one of the excess neutrons will "decay" into a proton & an electron (a form of radioactive decay called beta minus decay). When that happens, the nucleus goes from 92 protons to 93 protons, which makes it Np instead of U. The 239Np will then decay into 239Pu using the exact same method with a half life of a couple minutes.

That's how we create 239Pu for nuclear weapons.

The 239Pu has a half life of 24,000 years, so only a small amount of it will radioactively decay during irradiation. Some of it will fission in the reactor, but the rest of it has a chance to "capture" more neutrons to form heavier isotopes of Pu, like 240Pu, 241Pu, & 242Pu. If this is allowed to go on long enough, then the Pu is no longer suitable for a nuclear weapon. This is why commercial power reactors don't produce weapons grade Pu - the fuel sits in the reactor too long and produces these heavy isotopes of Pu

241Pu can decay into 241Am, which can capture neutrons and decay into heavier elements, which can then capture neutrons and decay into heavier elements again, etc etc. This process can repeat all the way up to the element Fm inside a nuclear reactor.

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maddumpies t1_j4q3cmd wrote

Reply to comment by AmphoraExplorer in If nuclear fission in U-235 causes the atom to be split into 2 smaller atoms (such as Kr-92 and Ba-141) then how is it that U-236 is produced as waste since the U-235 was just split into smaller peices? by Ian98766

While cross sections are heavily dependent on neutron speed, there are other factors that affect the cross section and other factors that influence the reaction rate.

The temperature of the medium also matters and you can have effects like doppler broadening that will affect the cross sections (an important part of reactor safety). Number density of course plays heavily into reaction rates and going beyond that, material geometry and type of course heavily influences a reactor design (reflectors, shielding, absorbers, etc...).

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UpperCardiologist523 t1_j4q24oq wrote

Reply to comment by RobusEtCeleritas in If nuclear fission in U-235 causes the atom to be split into 2 smaller atoms (such as Kr-92 and Ba-141) then how is it that U-236 is produced as waste since the U-235 was just split into smaller peices? by Ian98766

Not a scientist so forgive me if i mess this up.

I often hear that When you hit a U235 atom with a neutron, it splits and results in 2 OR 3 new neutrons. I've always wondered about this OR part and stuggle to grasp at this seemingly random result.

Would the chance of an U235 atom ABSORBING the neutron and becoming U236, be in the about same ballpark chance? I understand these two different actions to not be correlated/connected, but i want to understand more, struggle with reading theory on my own and just wonder.

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