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Questions tagged [nuclear-engineering]

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

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Electronically controlled fusion reactor

It seems that currently, only two types of fusion reactor styles are being used for large scale testing: the Stellarator and the Tokamak. Both of these and a whole bunch of other designs have been ...
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0answers
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Determination of Dead time of a Geiger Muller counter using the two source method

While determining the dead time of a GM counter using the two source method, why do we ensure that only two sources are placed in the counter at all times i.e. while determining the counts when both ...
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42 views

Heavy water neutron slowing equation

How can I find some equations about neutron slowing effects of heavy water? how much heavy water is required to slow down a given percentage of neutrons to a required degree(For example how can I keep ...
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2answers
74 views

How do we contain nuclear fusion?

I understand that here on earth we create fusion at temperatures that are much hotter then our sun. What I want to know is how we contain those high temperatures safely. Also if any one can give an ...
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1answer
30 views

Heating effect of fast neutrons in Fast Breeder Reactors

Do fast neutrons play effective(meaningful) role in heating up the water in Fast Breeder Reactors? If so, how much do they?
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61 views

Why is Neon not used as a coolant for gas cooled nuclear reactors?

What is the reason that Neon is not considered as good coolant for gas cooled reactors? I haven't found any research nor experiment with Neon in this field. As I checked out Neon has small neutron ...
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1answer
68 views

Introduction to nuclear physics

I want to self-study nuclear physics in order to understand nuclear reactors and nuclear weapons, what books can you recommend?
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67 views

How is fusion reactor fuel initially accelerated?

If, in a nuclear fusion tokamak reactor, you start with neutral fuels, how do you accelerate the atoms fast enough to start the reactor? Or do all of the particles have to ionized to begin with?
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37 views

Interpertation of Motron Number

The Reynolds number is interpreted as the ratio of inertial to viscous forces in a flow. Are there similar interpertations for The Motron Number?
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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 ...
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1answer
44 views

What are the issues in highly enriched nuclear reactors?

The kinds of reactors used in submarines and rockets, are known to have highly enriched uranium ~80% and CO2 as the moderator in subs, and carbon(graphite) I guess in rockets. What are the extra ...
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2answers
112 views

Why do we not use cold neutrons in nuclear reactors?

Typical nuclear reactors use neutrons in the $10^{-2}$ eV range (thermal neutrons) which corresponds to a fission cross section of a few hundred barns. What stops us from using a super-cold moderator, ...
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1answer
27 views

Which elements or isotopes can be analyzed by Neutron activation analysis (NAA)?

Some sources name only a handful, but that might refer to the use of optical film. Others state more than 70. I would like to know which elemets or isotopes can be detectet/imaged by NAA.
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What determines direction of plasma current in tokamaks?

Plasma current is used to ohmically heat fusion plasmas and provide stabilization of grad-B drift in tokamaks as the resulting poloidal motion of the charged particles results in the particles ...
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1answer
64 views

Does plutonium need to be squeezed to produce an uncontrolled chain reaction?

I guess what I am asking is if in theory you could start with a certain amount of plutonium would it explode with out being squeezed together as is done in an atomic bomb ? Normally what happens ( ...
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2answers
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How is energy actually extracted from fission?

Every source I can find right now just says something like 'energy/ heat is released by nuclear fission' but I can't find a description of the specific mechanism. I know that the energy 'conversion' ...
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2answers
761 views

Why is specific nuclear activity (Bq/kg) not considering the surface area (cm^2)?

I have some basic questions regarding nuclear radiation: How come the specific activity (Bq/kg) only depends on the mass number and halftime of the emitter? Therefore, the emitted ions (let's say ...
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39 views

Optimal Deuterium-Deuterium fusion pressure equation?

I am building a Hirsch-Farnsworth Fusor (a simple D-D fusion reactor) and was wondering if there is an equation or algorithm that could be used to calculate the optimal pressure for deuterium-...
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35 views

What is the difference in energy density between molten salts and liquid metals?

Does sodium-potassium and lithium liquid metal mixture (NaK-Li) or transport molten salts (LiF-NaF-ZrF4) have a higher energy density? How much higher? Also, could either of these coolants be used in ...
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Observations of a mushroom cloud

In this video of a nuclear bomb detonation/mushroom cloud, a few peculiarities arise and I simply had a couple questions pertaining to observations in the animation: Following the detonation, the ...
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1answer
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What is realistic minimum possible size, weight and power output of an atomic battery for 100kWh? [closed]

AFAIK atomic batteries could become a single unit nuclear reactor, but what it is smallest feasible configuration by our current knowledge? (even at conceptual design level)
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1answer
79 views

Nuclear fusion difficulties

What is it that make nuclear fusion so difficult at low temperatures? There is plasma existing at low temperatures, so what does it make for fusion to be so difficult to reach at ambient temperatures?
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4answers
113 views

Nuclear Physics Modeling Software

I have a nuclear reactor design I would like to model. I would like to show the individual atoms and how they interact with each other in the reactor (specifically, I would like to model decay modes, ...
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1answer
54 views

Control of Nuclear Fission

What is it precisely which prevents current technology in nuclear fission from controlling the size of fission products; in other words, why is it not feasible, presuming that such an approach would ...
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1answer
85 views

Can radioactive decay particles be modeled as plasma?

Since plasma is simply ionized gas (ie. charged particles), with the exception of neutron ejection (no charge) and gamma radiation (photons), can the natural decays of an isotope be modeled as plasma? ...
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What is the shelf-life of a gravity-powered uranium bomb?

Inspired by this Worldbuilding question about making a booby-trap with a very long shelf life. The idea is to suspend one lump of fissile material say $3/4$ of a critical mass above another of the ...
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3answers
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Are the magnets in tokamaks variable in strength?

For example, if the plasma inside is beginning to terminate and collide with the walls of the confinement vessel, can the magnets account for this and realign the plasma?
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1answer
263 views

How many inches of lead would it take to stop the gamma rays equal to 8 inches of concrete ?

I have searched high and mighty on google and it is hard to find a comparison chart of different materials and their effectiveness to stop radiation from fallout. I am assuming the fallout source is ...
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0answers
157 views

What's the critical mass of elemental natural uranium? [closed]

What's the critical mass of elemental (ie metallic), natural (ie unenriched) uranium? If this isn't possible at standard temperature and pressure, how could they be changed to make a critical mass? Eg,...
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2answers
150 views

What would happen if you detonated a nuclear bomb inside a tank of liquid hydrogen?

Say you had a large bomb - take the 50 megaton Tsar Bomba. You then proceed to place it in the center of a spherical tank containing liquid hydrogen, and then detonate it. Could you start a fusion ...
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3answers
206 views

Nuclear reactor in a cruise missile. How?

So it is declared, that there are cruise missiles with nuclear reactors on board. As I understand, when it's working, the neutrons keep flying from off the fuel. Neutrons give induced radioactivity. ...
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0answers
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How are cages in fusers protected against ion damage?

I have a simple question. Nuclear fusers (like the Farnsworth Hirsh design) use charged cages to accelerate deuterium ions to high enough energies to fuse and produce neutrons and energy. While these ...
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How can we make a nuclear weapon more effective in shielding us against asteroids?

I know that nuclear weapons do not produce the nuclear blast as it would at see level. But would the thermal blast produce any trust to push any asteroid away? If so, how could we improve the ...
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Can a plasma ball be converted into a fuser?

I was looking at fuser designs as shown on the Internet (like on Make Magazine). I looked at the details of how it works, and to me it looks like essentially a transformer and a high voltage rectifier ...
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2answers
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How is the radius of a nuclear disaster affected area calculated?

For example, take the Chernobyl disaster of 1986. The government evacuated a $30\,{\rm km}$ radius. I don't understand why $30\,{\rm km}$, I mean it's radiation, right? It can travel at speed of light....
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2answers
111 views

What happens to molecules when a neutron is captured?

What happens to a molecule during neutron capture? Does the process release enough energy to break the molecule bond? In fission this is obviously the case, since the compound nucleus forms and then ...
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1answer
40 views

Calculating the energy produced in watts in Alcator C-Mod

I calculated the energy in joules that a deuterium-tritium fusion reaction releases and found 2.81829046e-12J. I then read on some MIT articles that the Alcator C-...
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2answers
134 views

How ready is the current fusion reaction technology for the mass production of electricity?

Could you give a clear summary statement about the maturity of the controlled fusion reaction technology and its readiness for the mass production of electricity? There are many articles on internet ...
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2answers
119 views

Why it took such a long time for an army of physicists to realize the atomic bomb, while in theory it seems pretty easy?

I think most of us know about the construction of the first atomic bomb at Los Alamos, with Robert Oppenheimer (who said he became "The destroyer of worlds", which goes to show he regretted his ...
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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) ...
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1answer
36 views

How to excite high spin nuclear state from ground state?

For example, the ground state of a nuclei is $0^+$, and we can excite $1^-$ state with a circular polarized gamma photon, which has a spin angular momentum $1\hbar$. This satisfies the selection rule ...
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38 views

Nuclear state notaion $J^\pi$

I have learned from nuclear physics literature that a nuclear state can be denoted as $J^\pi$, where $J$ is the spin and $\pi$ is the parity, such as $0^+, 1^+$. But when I read some papers on nuclear ...
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2answers
459 views

Why can't we harness the energy from neutron + protium = deuteron reaction?

The answer to this physics se question, established that 2.2Mev (Mega electron volts) of energy is emitted as a gamma ray photon when the hydrogen atom nucleus oka protium absorbs a slow moving free ...
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56 views

Could we create our own mini star?

If NASA were to work together with other space programs, could we accomplish the task of creating a mini star in the future. It wouldn't be huge, under a mile in diameter. We could make a core of ...
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1answer
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) ...
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2answers
108 views

Neutron Creation Machines [closed]

My question is specific "what methods are there to generate free neutrons"? With a few aside queries and confirmations of undertanding Now as I understand free protons are far easier to create than ...
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2answers
66 views

Is there any industrial scale nuclear transmutation currently in practice?

So I am aware that transmutation is used to reprocess radionuclides in nuclear waste to render them into shorter lived radioisotopes. But what about the potential for industrial scale nuclear alchemy ...
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1answer
86 views

What are the natural forces that slow the neutron down?

In a nuclear bomb, I've noticed that slow neutrons don't affect plutonium 239, if we're using this kind of atoms (plutonium 239), we need fast neutrons to make a sustainable chain reaction. Also I've ...
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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-...
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How to decide between sizes of particles for maximum light intensity for scintillation?

Are nanoparticles or microparticles or quantum dots better suited as scintillation materials as far as light yield intensity is concerned? I was unable to find literature that compares micro vs ...