The study of radiation and radioactive materials and it's creation, safety, and applications.

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37
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8answers
12k 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, ...
23
votes
8answers
4k views

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 ...
16
votes
2answers
478 views

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 ...
14
votes
4answers
2k views

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 ...
11
votes
3answers
3k 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 ...
9
votes
2answers
3k views

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 ...
8
votes
6answers
2k 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, ...
8
votes
3answers
2k views

why aren't there nuclear powered aircraft?

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 ...
8
votes
2answers
1k views

Military-grade U-235 uses

In the news it is often mentioned that some countries are going to enrich uranium to "military grade" (i.e. 80%+) and that it is possible to use it for a nuclear bomb. 1) Is that correct that there ...
7
votes
3answers
146 views

Neutrons reflective materials in nuclear reactors

Nuclear reactors are driven away from criticality with the use of control rods which absorb neutrons. In case of overheating and melting of the core, the control rods may not be inserted any more ...
6
votes
1answer
296 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 ...
6
votes
3answers
4k views

How do you build a nuclear reactor in your garage?

When I came across this link earlier today, I was astounded. Nuclear reactors are immensely complex devices that took scientists years to develop, and are usually housed in huge facilities. The link ...
6
votes
2answers
517 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 ...
6
votes
4answers
1k 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 ...
5
votes
1answer
770 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 ...
5
votes
2answers
641 views

Do brick walls effectively protect against ionizing radiation from a nuclear explosion?

Of course it depends on the distance and the amount of radiation, so let's say its about 10,000 Rad. Now, can wall made of brick protect someone behind it from such radiation ?
5
votes
1answer
251 views

What causes the structure visible in first few milliseconds of a nuclear explosion?

Following on from this question, here is a high-speed photograph of a nuclear explosion, taken about 1 ms after detonation: (source) As anna v pointed out, several similar images can be seen in a ...
5
votes
0answers
92 views

What is the most stable nuclide of an isobar?

From the semi-empirical mass formula, the mass of an atomic nucleus is $$M\left(A,Z\right)=Zm_p+(A-Z)m_n-\frac{E_b(A,Z)}{c^2}$$ I've been told (at first) that for a given mass number $A$, the most ...
4
votes
6answers
714 views

Is there any inherent danger in operating a Thermonuclear Reactor?

Nuclear fusion research appears to promise sustainable, practically unlimited energy, and according to ITER it will be a perfectly safe, non-polluting source of energy. My question is if there are ...
4
votes
3answers
606 views

What is generating the hydrogen that has exploded in the Fukushima reactor?

The explosions at the Fukushima nuclear reactors were caused by a build of hydrogen. I was wondering where this hydrogen came from. This question Fukushima - Isn't the hydrogen presence a proof ...
4
votes
2answers
188 views

Can bad guys really hide “dirty bomb” material via bananas?

This one probably has some cross-over with Skeptics SE, but I thought it fits here a little better. The concept comes from the TV show NCIS:LA second season episode "Empty Quiver" Here, the villains ...
4
votes
1answer
102 views

Gaseous fission: Has it even been demonstrated experimentally?

I've been reading quite a bit about gas-core reactors, a theoretical reactor design where the fissioning of Uranium(along with Plutonium & possibly Thorium)occurs in gas phase. The result is that ...
4
votes
1answer
107 views

scrap iron for stopping a meltdown

Would it be possible in a Fukushima-style meltdown to halt the process (edit: I mean halting the meltdown process, not the actual nuclear processes) by dumping large amounts of iron into the vessel? ...
4
votes
0answers
137 views

Saturn V F-1 engines and beyond

I read that the F-1 engine from the 1st stage of the Saturn V rocket is the most powerful engine ever created by mankind, delivering ~200 gigawatts of power. Thus, I have got two questions: Will ...
3
votes
10answers
2k views

Can a nuclear reactor meltdown be contained with molten lead?

If lead can absorb or block radiation, would it be possible to pump molten lead into a reactor core which is melting, so that it would eventually cool and contain the radiation? Is there something ...
3
votes
2answers
968 views

Is the E-cat for real?

Does this thing really do what they say? http://www.youtube.com/watch?v=EhvD4KuAEmo If it does, it looks like this will probably be the biggest breaktrough in science ever :)
3
votes
4answers
315 views

Why was PACER abandoned?

The PACER project is described in this question: How much of the energy from 1 megaton H Bomb explosion could we capture to do useful work? Why was it abandoned? It seems that it is the only readily ...
3
votes
2answers
380 views

How much radiation exposure in the US was caused by the 105 nuke tests in the Pacific?

Between 1947 and 1962 the US conducted 105 tests of nuclear weapons in the "Pacific Proving Grounds". I'm wondering how much radiation exposure resulted on the west coast of the US. These were part of ...
3
votes
1answer
217 views

How is it possible to calculate the energy liberated by a given fission process?

How is it possible to calculate the energy liberated by a given fission process? For example, in the fission of a $^{235}$U induced by capturing a neutron?
3
votes
2answers
71 views

How to block neutrons

What is a good way to block neutrons and what is the mechanism that allows this? It's my understanding that polyethylene is somewhat effective. Why?
3
votes
1answer
65 views

The synthesis of $^{254}\text{No}$

How is $^{254}\text{No}$ synthesised? Could you explain the reaction where it is preceded by $^{208}\text{Pb}(^{48}\text{Ca}, 2\text{n})$? References to articles are well enough—I was somehow unable ...
3
votes
1answer
241 views

Why is the total interaction cross section larger for incident particles with lower energy?

The cross section of a nuclear interaction is a measurement of the probability of that interaction occuring. These probabilities are typically presented in terms of barns ($10^{-28}$ m$^2$) as a ...
3
votes
1answer
299 views

Nuclear Salt Water Rockets: viability and follow-up

This is the original paper by R. Zubrin proposing the Nuclear Salt Water Rocket design. Basically the design is that a capillar set of pipes store a uranium salt-water solution, inside a cadmium ...
3
votes
4answers
336 views

Is a Rubbia thorium reactor safer than other modern reactor types?

I keep wondering how a Rubbia thorium reactor would handle a natural disaster of Fukushima level intensity. As I understand it the nuclear chain reaction would stop instantly if the power is cut, but ...
3
votes
1answer
90 views

Containement system of a nuclear reactor: role of the water moderator

In a modern nuclear reactor for example a PWR there are multiple containment systems which prevent the release of radioactive material into the environment and shield the environment from the ...
2
votes
2answers
457 views

Russian Doll Teller Ulam?

Can you trigger a thermonuclear explosion from a smaller thermonuclear explosion in a scaling way, so that starting from a small laser ignited fusion within a small fissile container, using the X-rays ...
2
votes
3answers
424 views

Nuclear physics problem, Why do we use high weight atomic elements?

So as far as I know, nuclear fission uses high weight atomic elements to manufacture power. If the risk of runaway reactions are a major reason for not expanding this technology, why don't we use ...
2
votes
2answers
802 views

Nuclear reactor control rods

What is the relation between control rods surface exposed into a nuclear reactor and neutron energy? Is it linear? I mean, how do neutron absorbing rate change with the progressive immersion of ...
2
votes
5answers
339 views

Thorium radioactivty vs Uranium radioactivty nuclear power

May i please open this question by asking that if you intended to answer this please could you provide links based on your answer. I have read ( and posted one ) on thorium and a lot of the answers ...
2
votes
2answers
100 views

Can Deuterium undergo a nuclear fusion without the presence of Tritium?

I've been reading about fusion fuels for a while now, and I understand that in Lithium-Deuterium fuel, the neutrons from the fission reaction bombard the Lithium to produce Tritium and the D-T ...
2
votes
1answer
732 views

Why are we not using thorium for energy? [duplicate]

Possible Duplicate: What practical issues remain for the adoption of Thorium reactors? I have been reading and watching a bit on thorium TH 90 and cannot understand why this is not being ...
2
votes
1answer
94 views

Could one “build” elements?

I was wondering this: would it be possible to "construct" elements by arranging their constituent particles in high-energy environments? So apart from just fusion, could you sub-atomically manufacture ...
2
votes
2answers
314 views

Water-cooled fast neutron reactors

Can anyone explain why fast neutron reactor designs use sodium/lead/salt cooling, instead of water (heavy/light)? Is that because neutron absorption by water would not allow to break even in fuel ...
2
votes
1answer
70 views

Boiling water reactor

What are the typical power densities in conventional boiling water nuclear reactor per cubic centimeter of fission material?
2
votes
2answers
96 views

Would sea water moderate a nuclear submarine meltdown?

My son asked me: If nuclear submarines get sunk or blown up, what is to stop them going into nuclear meltdown? I thought about it and came to the conclusion that because they're in the sea the ...
2
votes
2answers
157 views

Why increase pressure to go from liquid to steam?

Assume the following phase diagram $T-H$ of water At a nuclear engineering course, I was told that in order to increase the performance of a pressurized water reactor, one has to increase the ...
2
votes
1answer
107 views

neutron transport approximations for nuclear rocket modelling

I'm pretty ignorant regarding neutron and nuclear transport modelling, but i'm interested in trying to pursue it for a particular pet project. It regards modelling of nuclear reactions like those ...
2
votes
1answer
561 views

Why did the Hydrogen in Fukushima explode *outside* the reactor vessel?

As pointed out before, it orginated inside the reactor vessel but exploded outside: how did it get there? Did it pass the shell by diffusion or was it released by the engineers?
2
votes
1answer
301 views

Fukushima - Isn't the hydrogen presence a proof of meltdown?

As I understand, the hydrogen is produced by water thermolysis, which need quite high temperature. This temperature is close to previously observed corium temperatures. So: Is the eutectic ...
2
votes
2answers
506 views

If there is a meltdown at the Fukushima reactors, would the control rods melt also?

According to the reports, the shutdown procedures at all the Fukushima reactors were successful, and all the control rods were fully inserted. So - if there was a meltdown, would the control rods ...