Questions tagged [nuclear-engineering]

The study of radiation and radioactive materials and their creation, safety, and applications.

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Why is nuclear waste more dangerous than the original nuclear fuel?

I know the spent fuel is still radioactive. But it has to be more stable than what was put in and thus safer than the uranium that we started with. That is to say, is storage of the waste such a big ...
Anthony B's user avatar
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66 votes
5 answers
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Why isn’t CERN afraid of a fusion reaction in the LHC?

Given that they can reach terrifying energies and temperatures, why isn’t fusion of protons a concern? After all, they start with a plasma and ram protons into each other. At some point the strong ...
aquagremlin's user avatar
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59 votes
8 answers
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Is it possible to send all nuclear waste on Earth to the Sun?

If we neglect the danger of unsuccessful lift-off of the rocket and the cost, would it be physically possible to send all nuclear waste on Earth to the Sun? Will there be an obstacle that prevents ...
Mubin Icyer's user avatar
56 votes
10 answers
23k views

What practical issues remain for the adoption of Thorium reactors?

From what I've read on thorium reactors, there's enormous benefit to them. Their fuel is abundant enough to power human civilization for centuries, their fission products are relatively short-lived, ...
GordonM's user avatar
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49 votes
2 answers
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Cause for spikes in Trinity nuclear bomb test

In Richard Rhodes' book, The Making of the Atomic Bomb, I was reading about the Trinity nuclear test. High speed photos were taken and this one is from <1ms after the detonation. The book mentions ...
Ryan's user avatar
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44 votes
3 answers
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What stops us from creating a nuclear fusion reactor as we already have the hydrogen bomb working on the same principle of fusion?

I have been out of physics for some time now since my childhood, so please bear with me if the question below feels too novice. I grew up with the understanding that the nuclear fusion reaction is ...
Xinus's user avatar
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39 votes
10 answers
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Why don't modern spacecraft use nuclear power?

The Voyager 1 & 2 spacecraft launched in 1977 with Plutonium as their source of electricity. 34 years later they claim these two spacecraft have enough power to last them until at least 2020. That ...
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37 votes
3 answers
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Nuclear Fusion: Why is spherical magnetic confinement not used instead of tokamaks in nuclear fusion?

In nuclear fusion, the goal is to create and sustain (usually with magnetic fields) a high-temperature and high-pressure environment enough to output more energy than put in. Tokamaks (donut shape) ...
Valentina's user avatar
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36 votes
8 answers
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How large would the steam explosion at Chernobyl have been?

So the second episode of the HBO series began to cover the risk of a steam explosion that led to them sending three divers into the water below the reactor to drain the tanks. This occurred after the ...
Nick S's user avatar
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34 votes
4 answers
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Why is water a good neutron absorber?

I've seen this question asked multiple times, and the answer is never detailed. I initially assumed that either hydrogen or oxygen had relatively large neutron absorption cross sections, however that ...
ryani42's user avatar
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31 votes
5 answers
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Is it possible to build a thermoelectric nuclear power plant?

Current nuclear power plants are essentially an enhanced version of a kettle, which seems like a stupidity caused by a lack of other options. We heat the water which turns to steam which rotates the ...
hijarian's user avatar
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31 votes
2 answers
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How would a black hole power plant work?

A black hole power plant (BHPP) is something I'll define here as a machine that uses a black hole to convert mass into energy for useful work. As such, it constitutes the 3rd kind of matter-energy ...
Alan Rominger's user avatar
31 votes
5 answers
30k views

How do control rods work?

I understand the basic idea of nuclear fission: put a bunch of fissionable material together and let the neutrons fly. An atom gets split, kicking out a few more neutrons, which split other atoms, ...
Mason Wheeler's user avatar
30 votes
6 answers
18k views

Why are cooling towers at nuclear power plants shaped the way they are?

The iconic cooling towers at most nuclear power plants are shaped like hyperboloids. Wikipedia mentions that this is because the wide base promotes thin film evaporation and the narrow point ...
templatetypedef's user avatar
25 votes
5 answers
5k views

Help! An 8 year old asked me how to build a nuclear power plant [closed]

I would really like to give an explanation similar to this one. Here's my current recipe: (i) Mine uranium, for example take a rock from here (picture of uranium mine in Kazakhstan). (ii) Put the ...
crestmods's user avatar
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24 votes
15 answers
8k views

Why are nuclear fusion reactors difficult?

The first fission bomb was created in 1944, and the first fission reactor in 1951 (and actually productive one in 1954). This delay seems possible to explain by there being a larger amount of initial ...
user56834's user avatar
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24 votes
7 answers
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Is special relativity relevant to understand nuclear bombs?

It is often claimed that Special Relativity had a huge impact on humanity because its understand enabled the invention of the nuclear bomb. Often, the formula $E = mc^2$ is displayed in this context, ...
Turion's user avatar
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23 votes
1 answer
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Why is the graphite moderator in a nuclear reactor radioactive?

Some nuclear reactors (like the RBMK in Chernobyl) use graphite as a neutron moderator. As far as I understand, this graphite material, either in rods or as blocks with embedded channels, surrounds ...
shaiko's user avatar
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22 votes
4 answers
6k views

Why don’t nuclear reactors burn through most of their fuel before discarding it?

The question: Why don’t nuclear reactors use more of the fuel, eg, 50%, 80%, before discarding it? It looks like there is plenty of energy left, and uranium is expensive. Also, there would be an ...
11111's user avatar
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20 votes
7 answers
7k views

Why is it impossible for the reactor of the nuclear power plant to turn into an explosive nuclear bomb?

Is it true that both work on the same principle of operation: the interactive fission chain reaction 235U/239Pu and the bombardment of uranium-235 by fast neutrons produce a fission chain reaction ...
user avatar
20 votes
3 answers
1k views

Why do nuclear bombs make a mushroom?

Atomic bombs make mushroom. It's well-known and we've seen many images of atomic experiments around the world. My question is, what causes the mushroom shape? Do conventional explosives like TNT and ...
Saeed Neamati's user avatar
18 votes
5 answers
2k views

Which experiment gave scientists reason to believe nuclear fission/fusion produced energy?

Every piece of knowledge in science has a beginning lying in someone's experiment. I would like to know which experiment gave scientists the reason to believe nuclear fission/fusion existed and was ...
Klik's user avatar
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18 votes
1 answer
1k views

Why all the orifices, protuberances, hinged/bolted panels, etc. on a stellarator?

My question was inspired by this one - in particular the image it has (also shown here): Why does the external casing of the Stellarator (in particular, the Wendelstein 7-X shown in the above image) ...
pr1268's user avatar
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18 votes
2 answers
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Is there a sound theoretical argument against inner-shell induced nuclear chain reactions?

There is a claim often made about cold fusion, that it is excluded theoretically. The main theoretical argument is that electronic energies are too low to overcome the Coulomb barrier, since d-d ...
Ron Maimon's user avatar
17 votes
4 answers
17k views

Why aren't betavoltaics and alphavoltaics batteries widely used?

Betavoltaic batteries are devices which creates electricity from beta radiation of a radioactive material. Alphavoltaics operate similarly, using alpha radiation. The concept was invented roughly 50 ...
Suzan Cioc's user avatar
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16 votes
3 answers
3k views

Why do some gases transfer radioactivity and some don't?

I have recently read that helium is going to be used as coolant in Generation IV nuclear reactors, because Helium is radiologically inert (i.e., it does not easily participate in nuclear processes ...
FrantišekV's user avatar
16 votes
2 answers
3k views

How to detect a secret nuclear detonation here on the earth?

How can we know that North Korea and Iran (to name a few) are exploding nuclear weapons if no inspectors have ever been granted access to suspected nuclear sites in these countries? How can we ...
user avatar
16 votes
4 answers
15k views

Nuclear fuel pellets - when does the chain reaction start?

Questions about nuclear fuel: Does nuclear chain reaction start in fuel pellets even before they being installed in reactor? If not, why not? My understanding is that since the fuel pellets are ...
pipsi's user avatar
  • 895
16 votes
1 answer
514 views

Spallation neutron generation and pure U-238 reactors

Main question: Is it possible to achieve net power generation based on linear proton accelerator and U-238 target? In the proposed reactor design there is a proton beam with energy ~10 GeV, and on U-...
BarsMonster's user avatar
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15 votes
4 answers
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Why can't there be a trap door under nuclear reactors in case of meltdown?

This may be a naive question, but after the Fukushima Daiichi partial meltdown and studying the aftermath of Chernobyl it seems they could be helped by this idea. In Chernobyl, the liquidators that ...
Michael Papile's user avatar
14 votes
1 answer
4k views

What are the white lines in some nuclear bomb test photos?

What are those white lines connecting the ground to the sky on the left side of this photo? I've see these before in the nuclear bomb test films too. They're apparently already in place upon ...
Sparky's user avatar
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14 votes
2 answers
10k views

Why is Helium-3 better than Deuterium for fusion energy production?

I see that many websites and magazines with physics thematic are pretty excited about mining Helium 3 isotope on the Moon. But this seems to be a very hard-to-get resource. For more than one reason: ...
Tomáš Zato's user avatar
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13 votes
2 answers
2k views

Pictures of nuclear explosions some milli/nano seconds after detonation

Where I can find photos of nuclear explosions just after detonation (before 5-10 ms, the shorter the better)?
Anixx's user avatar
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13 votes
1 answer
1k views

Is it possible to make an all natural smoke detector from Brazil nuts?

After reading about Brazil nuts, I discovered they have very high levels of radiation due to trace amounts of Ra-226 and Ra-228 and their decay products. A kilogram of the nut, for instance, gives a ...
user148298's user avatar
13 votes
4 answers
6k views

Why aren't there nuclear powered aircraft? [closed]

I know this might sound like more of an engineering question that about physics, and it probably is, but bear with me: I'm still not sure if the answer to my question lies in the physics or in the ...
user56771's user avatar
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13 votes
3 answers
67k views

Would being underwater help survive a nuclear bomb?

If I jump in my pool, on the river near my house knowing that a nuclear bomb, or atomic or H-Bomb exploded around 10 km from my house, would I survive? The way I see it is that water will protect me ...
Conrad C's user avatar
  • 911
12 votes
9 answers
6k views

Why does nuclear fuel not form a critical mass in the course of a meltdown?

A BWR reactor core may contain up to 146 tons of uranium. Why does it not form a critical mass when molten? Are there any estimates of the critical mass of the resulting zirconium alloy, steel, ...
wnrph's user avatar
  • 1,287
11 votes
1 answer
3k views

Why does it take so long to make a nuclear bomb?

So as I know nuclear bombs are derived from fission reactions: By providing the nucleus with enough power to trigger a chain reaction. If uranium was present why does it take so much to make a nuclear ...
Mark's user avatar
  • 521
11 votes
3 answers
7k views

Why didn't the control rods in Fukushima shut down the reactor?

With all the hubbub over the reactors in Japan and nuclear safety, I was wondering why the insertion of the control rods in Fukushima did not shut down the reactor? Shouldn't they slow the fission ...
Ziplin's user avatar
  • 253
11 votes
3 answers
2k views

Nuclear fusion scaling with reactor size

Thinking about the physics of thermonuclear fusion, I have always had an intuitive sense that making fusion feasible is matter of reactor size. In other words I feel like: If the fusion reactor is ...
Prokop Hapala's user avatar
11 votes
4 answers
579 views

How did Enrico Fermi compute when the Chicago Pile-1 nuclear reactor would become critical?

I'm trying to understand the first nuclear reactor, the Chicago Pile-1, specifically the math Fermi did to figure out when the reactor would go critical. There's a nice report available from Fermi, ...
Stephen W.'s user avatar
11 votes
4 answers
8k views

What is the minimum amount of fissile mass required to acheive criticality?

Wikipedia gives the following definition for critical mass. A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. No mention is made of a ...
Alan Rominger's user avatar
10 votes
4 answers
25k views

*Why* were the Chernobyl control rods tipped with graphite?

I understand the graphite tips of the boron control rods displaced water (a moderator) which lead to an increased reaction rate, rise in temperature and steam pressure etc. Question: why were the ...
nox's user avatar
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10 votes
1 answer
2k views

What is the theoretical efficiency of fusion?

What is the theoretical limit of the amount of energy that can be extracted from a fusion reaction? I am not talking about the practical efficiency of a reactor, but rather what fraction of the mass-...
Anders Sandberg's user avatar
9 votes
4 answers
3k views

Does a proton have a binding energy?

When calculating the $Q$-value, $Q = \Delta M \cdot c^2$, of this reaction: $$ ^6Li \ (\alpha, p)\ ^9Be \quad \iff \quad \alpha + \ ^6Li \ \longrightarrow \ ^9Be + p $$ The $Q$-value can also be ...
João Bravo's user avatar
9 votes
3 answers
2k views

Can the High beta fusion reactor work?

Are the claims made about the http://en.wikipedia.org/wiki/High_beta_fusion_reactor realistic? Can such a small fusion reactor really work?
asmaier's user avatar
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8 votes
4 answers
2k views

Non-irradiative methods to create radioactive isotopes?

My understanding is that the primary methods with which one can create a radioactive isotope are 1) just waiting for the isotope you want (by means of nuclear decay), or 2) some kind of induced ...
DataScienceNovice's user avatar
8 votes
4 answers
768 views

China's "Artificial sun"

So I heard in the radio today about China's "Artificial sun". There is this hype about it having 5x the temperature of the core of the sun. It is, as I suspected, a fusion reactor. I admit I ...
George Menoutis's user avatar
8 votes
1 answer
2k views

Why isn't Neptunium used in nuclear power plants?

The elements on either side of neptunium (uranium and plutonium) are, of course, widely used in both power plants and nuclear weapons. So why isn't the highly fissile nuclide Np-237 used in reactors? ...
Kurt Hikes's user avatar
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8 votes
1 answer
1k views

In the event of a disaster at any nuclear power plant other than Chernobyl, would we be dealing with the emission of radioactive iodine isotopes?

Would any nuclear catastrophe emit radioactive iodine isotopes? Do some power plants have different cores that would emit other radioactive isotopes but not iodine isotopes?
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