Climate Change Report

#676
#676
AM64 said:
As far as I can tell Germany, unlike Japan, isn't often subject to earthquakes and tsunamis. Germany is subject to some brutally cold weather from time to time and often limited sunshine. Putting all your eggs in wind and solar energy is risky business unless you have dragged enough firewood into your cave.
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Seems to be working pretty well for another cold weather country.

Renewable energy in Scotland - Wikipedia
 
#677
#677
#678
#678
NorthDallas40 said:
Out of curiosity and no idea if you can answer in a public domain. But the sizing of a single rod. Is the mass sized so that no single rod is a threat by itself and they only go critical when combined with other rods in close proximity and no control rods inserted? I am assuming that’s why a new fuel element is relatively safe?
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Yes, the amount and configuration of fissile material is carefully controlled to prevent inadvertent criticality. Typically there needs to be a neutron moderator to slow them down so that they can be absorbed by fuel (water works well because of the hydrogen in it) and something to reflect them back into the fuel region.
 
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#679
#679
Wafflestomper said:
Yes, the amount and configuration of fissile material is carefully controlled to prevent inadvertent criticality. Typically there needs to be a neutron moderator to slow them down so that they can be absorbed by fuel (water works well because of the hydrogen in it) and something to reflect them back into the fuel region.
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Ok thanks for the explanation!
 
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#682
#682
Orange_Vol1321 said:
So, if I've heard it once I've heard it a 100 times today. "Once in a lifetime generation of cold hitting the US next few days."

Libs when they hear this



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That is not how the global warming thing works. Individual weather events are not how global temps are monitored.
It just looks stupid to post this every time we have a snow.
 
#684
#684
NorthDallas40 said:
Out of curiosity and no idea if you can answer in a public domain. But the sizing of a single rod. Is the mass sized so that no single rod is a threat by itself and they only go critical when combined with other rods in close proximity and no control rods inserted? I am assuming that’s why a new fuel element is relatively safe?
Click to expand...

Wafflestomper filled you in pretty well. It's always touchy answering a lot of questions like this because if you simplify the answer too much, it may not get the real meaning across and someone else will hang you for getting it wrong ... so it's complicated. Generally the fission concept is that when an unstable fissile atom "splits", it ejects one or more neutrons (neglecting all the other stuff to be simple). Those neutrons if absorbed by another fissile atom make that atom unstable and it splits and so on ... the chain reaction. The touchy part is "critical mass" having enough fissile material arranged properly to sustain the fission chain. That is dependent on moderator, geometry, poisons (like boron) in the coolant, control rods, and the fuel itself (enrichment, type, etc). An ejected neutron (this again is with U-235 as fuel) is called a fast neutron (high energy); the "cross section" (probability that a neutron will be absorbed in an another U-235 atom) is low for fast neutrons but higher for "thermal" neutrons. A neutron being about the same atomic mass as a hydrogen atom can be moderated or caused to lose energy by multiple collisions with hydrogen atoms in water or carbon (like the pool ball thing - the energy is distributed between both balls in an impact).

Light water reactors (like those used in commercial plants) use highly purified water as both the moderator and coolant. To give an example of how things aren't quite as simple as they might seem. As the water is heated in the reactor and becomes a mix of water to steam, the moderator density decreases - that's called a negative coefficient of moderation. Most solids and liquids behave that way, but plutonium has a weird characteristic under which it will expand reasonably normally and then suddenly condense as reaches a certain temperature ... it's been way too long to remember all the details, but I think it had to do with the crystal lattice rearranging. So you get a reasonably normal negative thermal coefficient of reactivity and then a sharp positive change. The point is that there are a lot of variables that affect the whole process, and since there is a a significant temperature gradient form the bottom of the reactor to the top all those temperature coefficients are different along the entire fuel element ... top to bottom and radially.

On it's own, a single commercial fuel element (new or spent) cannot go critical. Casks, other containers, and storage systems for moving and storing new or irradiated fuel are carefully designed to preclude accidental criticality. One of the great things about the UT Nuclear Engineering program is the proximity to Oak Ridge and the access to different facilities there for labs. I distinctly remember one facility where we were introduced to storage and avoiding accidental approach to criticality. The only real fuel related thing I did after graduation was something called neutron noise analysis. It's basically using neutron flux detectors (ex-core for power level and in-core for flux distribution); except you study (Fourier analysis) the variation in the signal to determine core barrel and fuel assembly motion in an operating reactor.
 
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#686
#686
AM64 said:
As far as I can tell Germany, unlike Japan, isn't often subject to earthquakes and tsunamis. Germany is subject to some brutally cold weather from time to time and often limited sunshine. Putting all your eggs in wind and solar energy is risky business unless you have dragged enough firewood into your cave.
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Having spent a few years in Germany in the 60's I can attest that it's damn cold there. Actually it was the coldest place I've ever lived in my life. It was the only place that you "had" to wear gloves to keep your hands from freezing when you went outside. Them actually believing that solar can work there is kind of humorous.
 
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#687
#687
VolStrom said:
Having spent a few years in Germany in the 60's I can attest that it's damn cold there. Actually it was the coldest place I've ever lived in my life. It was the only place that you "had" to wear gloves to keep your hands from freezing when you went outside. Them actually believing that solar can work there is kind of humorous.
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I know. I guess it's maybe possible to get by with gas heating, but after seeing gas explosions lately, I'm beginning to have some questions about that. The other thing is that gas from another country makes you pretty susceptible to economic blackmail when you dump all your other options. And when the European manufacturers are pushing more toward electric cars requiring more electric power; it really makes you wonder who is doing the strategic thinking around the world. Although, I just can't see the German people giving up fast cars and autobahns.
 
#691
#691
Grand Vol said:
Still not good to put all your eggs in one basket.
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I agree to an extent. I think fossil fuels will remain an essential and cheap part of developing economies for quite a while. In the U.S. and elsewhere I think (hope) that renewables will displace most everything else. Storage solutions being the big hang up for now. Electricity is cheaper than gas.
 
#698
#698
jvol1 said:
And if the rocket explodes in the atmosphere....

No worries, right Marie Curie didn't die straight away
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Not that I think launching waste into space is a good idea, but nuclear is statistically safer than renewables in deaths per kwh.
 
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#699
#699
Wafflestomper said:
Not that I think launching waste into space is a good idea, but nuclear is statistically safer than renewables in deaths per kwh.
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Statistics occasionally lie. Apparently, no one ever dies that's that's involved with hydroelctric power, who knew? Go hydro, be immortal!

Risk in construction and management is different that the risk disposing in the waste or by-product of nuclear, aka the environmental concerns.
 
#700
#700
This just in, the climate is changing in Western, KY. Ice on the windshield this morning......High of 61 by Sunday......world comes to an end on Monday, 12 years ahead of schedule.
 
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