Questions tagged [nuclear-engineering]
The study of radiation and radioactive materials and it's creation, safety, and applications.
373
questions
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1answer
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How to mantain plasma current in a tokamak?
I know that a toroidal plasma current is an essential feature on tokamaks as it creates the poloidal magnetic field essential to avoid separation between negative and positive charges.
The current is ...
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1answer
35 views
How do cyceling moltant salt reactors do nuclear fission?
I only have an understand of how PWR's do nuclear fission, looking at the diagram for the salt reactors it's a bit confusing. Where is the fission taking place if the salt is cycling throughout the ...
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1answer
53 views
Why free neutrons are usually produced in a Nuclear Fission?
The production of neutrons is a feature of fission reaction. Usually 2-3 free neutrons are produced in the fission. Why is that so?
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1answer
36 views
Does Build up factor actually make it worse to have shielding?
I'm having a little trouble understanding Build up factor in radioactive shielding equations. I learned that the equation for shielding with the Build up factor is:
$$I = I_0 \cdot B e^{-ux}$$
And I ...
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0answers
33 views
What went wrong with the nuclear boy scouts breeder reactor?
If I recall correctly the Nuclear boy scout tried to build a breeder reactor but the experiment gave him radiation poisoning because the neutron emitter was to emitting to many neutrons.
Does anyone ...
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1answer
45 views
Why are PWR's being build instead of FBR's or LMFBR's?
Why are PWR's still being built in modern times when we have the option to use designs that allow intake of raw uranium without the need for enrichment and allow for recycling of waste material.
I don'...
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0answers
24 views
Energy from fission of Pb?
The fission of lead has been demonstrated as a result of proton or photon bombardment. The process releases energy from the mass defect between the original Pb nucleus and the fission products.
...
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0answers
27 views
How does a radiation meter equipped with a Geiger-Mueller Tube measure radiation dose?
The GM-tube typically operates in saturation and an incident particle will result in total discharge. Therefore, as I understand, the height of generated pulse is independent on the energy of the ...
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1answer
27 views
Silly question: make deuterium, tritium and Oxygen-17 and Oxygen-18 from nuclear waste
Here is a silly question. Atoms of Nuclear waste isotopes usually have extra neutrons. Can regular hydrogen and oxygen come into contact with those atoms and take the extra neutrons away? Then the ...
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1answer
51 views
Can we use tritium instead of helium-3 for nuclear fusion reactors?
I know that tritium isn't entirely stable (half-life of about 12.3 years) and might require a lot of energy to create large amounts (and transport/handle safely), but wouldn't that still be easier (...
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3answers
153 views
Why is a nuclear fusion reactor not currently possible? [closed]
Nuclear fission reactors are fairly common, but what technological/physical limitations are currently impeding developing the nuclear fusion reactor? The H-bomb is capable of creating nuclear fusion ...
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1answer
48 views
Are the presense of neutron reflecters the only difference between a hydrogen bomb and a neutron bomb? [closed]
From what I understand, a hydrogen bomb usually has neutron reflectors, like graphite, to increase the yield of the explosion. A neutron bomb does not have those reflectors. Are there any other ...
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3answers
51 views
What is the exponential (or geometric) rule (or law) for uranium enrichment?
Uranium ore starts at about .72% U-235...
At ~20% U-235, it is considered to be about '90% of the way' to weapons-grade uranium, which is about ~90% U-235...
Because uranium enrichment in centrifuges ...
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1answer
33 views
Can a gamma ray or x-ray cause an isotope change of a nucleus with all its electrons stripped away?
I learned that Sodium22 atoms decay to Neon 22 by ($\beta$+) (positron) emission. Also some other radioactive elements isotopes can undergo positron emission or electron absorption with a similar ...
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1answer
50 views
What is the quickest way to stop nuclear fusion without removing the fuel?
Would dumping enormous amounts of liquid nitrogen cool it quickly thus extinguishing it? Could a bomb disperse the fuel preventing fusion? Could adding a material stop the fuel from fusing? Is there ...
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2answers
91 views
How can a nuclear chain reaction start?
A nuclear chain reaction occurs when neutron amounts are multiplied by fission. A neutron triggers a
fission, which causes the fissioned atom to release multiple neutrons. If of those multiple ...
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0answers
48 views
High Level Nuclear waste disposal
Can anybody please explain 50 years and 5 years that has been written over here- https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-wastes/storage-and-disposal-of-radioactive-...
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2answers
68 views
Formula of decay heat for a fraction of radioactive materials
What is the formula of decay heat for a fraction of spent fuel? (say 50% spent fuel)
The Wigner-Way formula has not any parameter relating to the amount of fuel. Is there any other formula?
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2answers
37 views
Relevancy between (Atomic weight and neutron energy loss) and selection of materials for reactors
As we know, the relationship between atomic weight and neutron energy loss can give the number of collision between a neutron and nucleus to slow down (average logarithmic energy decrement.)
I was ...
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1answer
43 views
Enrichment needs of a uranium sample to convert all of the Uranium 238 into plutonium
I am being asked the following question for a homework:
"Uranium 238 is not fissible, but it is fertile. If you have 10,000 kg of
Uranium, how enriched would it need to be in order to ...
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1answer
41 views
Radiation in nuclear power system [closed]
What are the 3 high level groups of sources of alpha, beta and gamma radiation in nuclear power systems?
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1answer
52 views
Criticality of a reactor [closed]
How criticality of a reactor can be defined in terms of neutron interaction with matter(neutron capture, elastic scattering and fission)?
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2answers
66 views
Nuclear reaction [closed]
If boron reacts with a thermal neutron and produces an excited lithium and a ground state helium, what will be the function of this reaction in a nuclear reactor?
Will the potential energy of the ...
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1answer
39 views
Nuclear Binding Energy Graph
I know it is a silly question to ask, but I am confused with the following concept. Can anyone please clear it?
As we know, the binding energy of H-1 is zero, so the fusion process would start from ...
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1answer
198 views
Nuclear Binding Energy Curve
As we know, anything to the left of Iron-56 in Binding Energy curve can be created by nuclear fusion reaction. The same with the fission products to the right side of Iron-56.
But in case of this ...
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2answers
43 views
Cycle length of a LP for a PWR reactor
How to obtain the cycle length as a function of the loading pattern for a pressurized water reactor?
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1answer
35 views
Is there any significant scale nuclear transmutation currently in practice?
There was a similar question in place but the details of the answer may suggest another solution.
So I am aware that transmutation is used to reprocess radionuclides in nuclear waste to render them ...
2
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2answers
123 views
What determines whether a water-cooled nuclear reactor has a positive or negative void coefficient? [closed]
If I'm not mistaken it is the case that in water-cooled reactors the water acts both as a neutron absorber (negatively contributing to the amount of fission) and as a moderator (positively ...
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1answer
48 views
Math in Nuclear Reactor [closed]
I don’t understand the meaning of equations in nuclear reactor physics. How do I learn the relevant content? Those complicated formulas and symbols often confuse me. How can I learn reactor physics ...
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1answer
53 views
Shaped charges/explosive lenses and implosion in the Fat Man design for the Nuclear Bomb: how do these actually cause implosion? [closed]
This is gone into at some length but not much detail (that I could understand) in "The Making of the Atomic Bomb" by Rhodes. The basic story is that the Americans were having trouble getting ...
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2answers
50 views
How many atoms does a relativistic ion dislodge?
Given a large chunk of some hard, refractory material e.g. graphite, diamond, tungsten, at low temperature surrounded by vacuum, and an impacting relativistic ion – to be specific, say an alpha ...
1
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1answer
74 views
If Pu-239 is irradiated in a neutron flux, will a fizzle detonation occur? How much flux would be required?
I understand that adding flux does not change criticality. I'm not looking for K values here, just an estimate of the added neutron flux required to disable a typical ICBM warhead. I would like to ...
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1answer
60 views
Why is 20% enrichment for uranium considered the minimum for making a nuke? [closed]
I get that this is the physical limit - an infinite mass of uranium would produce a runaway reaction. But an infinite mass is impossible.
Really, what is the minimum % of enrichment of uranium which, ...
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1answer
49 views
What are the major difficulties to the production of elements?
Searching online about this topic only gives results about nucleosynthesis (making elements by nature) and the 24 radioactive artificial elements.
Why isn't there any information about methods to make ...
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1answer
33 views
Do you need to account for relativistic effects for neutron-nucleus collisions in nuclear physics?
When you calculate the kinetic energy or the angle of deflection, etc, do you need to take in account relativistic effects (whether you are in the center of mass or in the laboratory system)?
I mean ...
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2answers
30 views
Does the Doppler broadening in nuclear physics also change the interaction type of the particles involved?
Relative motion of the nucleus due to the temperature causes the Doppler effect broadening. But does the change of temperature also change the type of interaction, directly or indirectly? For example, ...
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1answer
147 views
What is Fermi age? What does it represent? [closed]
What does the lethargy represent? What are its units? What is the range of the lethargy? (Is it between 0 and 1?)
The definition of lethargy is:
$u = \ln \frac{E_0}{E}$
and the average increase in ...
0
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5answers
109 views
Could you theoretically build an nuclear-blast-proof safe? [closed]
Some bulletproof safes are sturdy enough to handle grenade impacts. Could we theoretically make an analogous atomic-proof safe that will handle something like an Hydrogen Bomb? It doesn't matter the ...
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3answers
86 views
Why arent'the best neutron absorbers always the ones with the largest cross sections? Does the reaction product have something to do with it?
There used to be a question (and answer) here that mentioned why isotopes of cadmium, xenon, hafnium, etc. that have larger cross-sections than boron-10 weren't as good at being neutron absorbers in ...
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3answers
96 views
Destroying Nuclear Waste with Neutrons?
is it possible to safely dispose of nuclear waste by bombarding it with neutrons, and if so, what energy/temperature of neutron is required? Are thermal neutrons sufficient or must they be fast? ...
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0answers
36 views
Why does U-238 have a higher cross section for fast neutrons vs U-235?
Apparently the absorption of any neutron, even without attached kinetic energy, is enough to overcome the binding energy of U235, and fast neutrons scatter more vs thermal neutrons, so thermal ...
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2answers
355 views
What prevents fissile materials from fully undergoing nuclear fission?
As I have realised, most of the Uranium and Plutonium inside an Atomic Bomb do not actually fission together, even if the critical mass is used. In fact, for Little Boy, only 1.09 kg out of 64 kg of ...
0
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1answer
34 views
Charge state in Accelerator physics
while asking for calculation of magnetic rigidity for accelerators, I am seeing notations like '238-U-28+' & '197-Au-77+
Previously I was comfortable seeing charge state like 40-Ca-1+ ions before. ...
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1answer
56 views
How bad would it be to dump nuclear waste into the atmosphere?
Before I say any further, this is just a thought experiment, it's a crazy idea and I'm not suggesting otherwise!
A key pro/anti nuclear argument goes like so: nuclear waste storage is hard, but on the ...
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3answers
100 views
Could there (at least theoretically) ever be a way to prevent radioactive atoms from decaying?
I mean, in such a way as to make it feasible to have a collectible sample of an element like astatine, francium, or protactinium (ignoring their chemical toxicity, which could probably be contained in ...
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0answers
56 views
Why do Xe-135 and Zr-88 have a surprisingly large thermal neutron capture cross-section?
Why do Xe-135 and Zr-88 have surprisingly large thermal neutron capture cross-sections?
The probability that a nucleus will absorb a neutron—the neutron capture cross-section—is important to many ...
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1answer
54 views
In the Tchernobyl nuclear plant of the 1986 accident, were there a secondary circuit, or were there only a primary circuit? [closed]
In a typical modern nuclear plant, there are :
a primary circuit, which allows to transfert the heat of the fission (transfered to the water) to a secondary circuit.
a secondary circuit, which ...
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0answers
42 views
Why is the French Wikipedia of Tchernobyl plant stating the the power is of 1000 MW while English version states that this is 3200 MW?
The power of a given reactor for the Tchernobyl plant is, according to Wikipedia : 3200 MW (12800 /4 reactors)
Reference :
https://en.wikipedia.org/wiki/Chernobyl_Nuclear_Power_Plant
"Reactors ...
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2answers
80 views
What is the origin of radioactivity that appears *sometimes* in rivers close to a nuclear plant? [closed]
What is the origin of radioactivity that appears sometimes in rivers close to a nuclear plant? (due to nuclear plant activity) ?
In particular, is it due to primary circuit that would contaminate the ...
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0answers
2k views
What substance is being sprayed during this scene in Chernobyl?
In HBO's Chernobyl series, after reactor no. 4's meltdown, soldiers (Chernobyl's liquidators) splash a light-brown liquid onto the ground, both streets and forest, and for washing vehicles; for this ...
