Neutron Definition and 770 Threads

i need a help in solving ,using 1 group approxmation , estimate the critical size of cube consisting of 75% zirconium-91 and 25% plutonium--239 by volume , when the cube is surrounded by a vacumm. zr-91 microscopic cross section (capture)=0.00335 microscopic cross section (scattering )=5.89...

hello, I am new to MCNP, could somebody tell me how to use imp:n, what is imp:n=0 means, if neutron importance is 0 in one cell, why the F4 tally is 0 in this cell? how about imp:n=1 or some large number? Thanks for all.

Ok, I know neutron stars are mainly composed of neutrons. But also, they have some protons and normal nuclei at their surfaces. Is this crust of protons needed to keep the neutrons below stable? As in, if it disappeared, would the neutrons below start decaying back to protons to form its...

Why do different nuclei need different neutron speed to achieve fission?? My understanding is that U-235 requires a thermal neutron in order to be likely to cause a fission reaction, however Pu-239 requires the additional energy of a fast neutron in order to cause the nucleus to undergo fission...

Dear all, I just started using geant 4 to simulate neutron transport in the air considering three different types of collisions: elastic collision, inelastic collision, and neutron capture. Is there any similar examples in Geant 4 that I can refer to and play with? I know this is not a so...

Hello, I was reading about big bang nucleosynthesis recently (If it helps, I'm using Mukhanov) and it was calculating the abundance of neutrons. It seems to say that X_n→X_n^{eq} (It says that X_n^{eq} is the equilibrium abundance of neutrons) as t→0. So...does that mean that the neutrons...

There is a recent article about neutrons and how they escape to parallel universe. It is only a theory. You can probably find it by googling the title. How and when will they test for this? Is this likely to be true? Are there multiple universes or only an additonal universe plus are own?

After reading "The Five Ages of the Universe" by Greg Laughlin and Fred Adams, I wondered, if all matter composed of ordinary atoms (protons decay) decay, and black holes decay due to Hawking Radiation, do neutron stars decay in any way? They are composed entirely of neutrons that are kept...

I have had a question that I cannot get an answer for. I recently had an exam for energy in the nucleus which included a question about why lead nuclei would be inadequate for use as a moderator in a reactor. When I got the answer for the question, it stated that the lead nuclei reflect neutrons...

Hi, I'm a new member in the forum. I own two similar GM military grade meters with calibration certificates, calibrated for gamma-rays metering and each one has two tubes filled with helium, argon (or neon), halogen (or quenching) gases. When I am exposed to some radiation source, my GM meter...

Homework Statement What is the maximum kinetic energy (in keV to 3 significant figures) of an electron emitted in the beta decay of a free neutron? Write down the decay equation using accepted notation. Mass of a Neutron: 1.008665 u Mass of a Proton: 1.007276 u Mass of an Electron...

What is measured in a fast reactor for power calculation : fast neutron flux or overall ( fast + thermal) neutron flux ? My doubt is : The fission chambers used for measuring neutron flux undergo chemical reactions due to which type of neutron : fast or thermal ?

I need so advise on SPH open source code to use to look at mergers and rotating objects... if anyone has some links or tutorials? Thank you!

Hey, So i just read 2 articles, the first talked about the mathematical problem of 'packing', IE how many smaller objects of the same size can fit inside a shape without overlapping or covering the boundaries of the shape. and the second article was talking about a recent neutron star that...

Hello. I am wondering what are the properties of matter at the core of a neutron star. I read that it could be quark matter of strange matter, but overall uncertain. How can strange matter form if strange quarks decay very quickly into up quarks (the state of matter would last very shortly), and...

Thank for all if you understand my ideal. My problem is i don't know what's neutron which cause of fission in critical accident? seem it must be have the first neutrons, and then reaction fission occurred ? eg The critical model in some nuclear accident, what is neutron source? The...

and successfully fission. let's say a neutron approaches the spherical nucleus from a particular distance. its possible route to the nucleus has a conical shape. how far from the center can it strike and still fission? If it just nicks it just inside a tangent line will it fission?

ok, this is the question: neutrons scatter elastically at 1.0MeV. after one scattering collision, determine what fraction of neutrons will have energy of less than 0.5 MeV if they scatter from: a. hydrogen b. Deuterium c. Carbon-12 d. Uranium-238 solution process... the basic...

just thinking cross sections here. a neutron that is freed as a result of a fission of pure U235. travels @c/10(fast!) will its trajectory be perturbed by the gravitational force emitted by a nearby nucleus, or do things on the quantum level work differently?

a. it rotates faster b. it is smaller c. it is more luminous d. it has stronger pulses I'm stumped on this practice question for my final. I'm thinking that a. and d. contradict each other since doesn't an older, slower rotating neutron strong emit longer, stronger pulses? C. seems to...

1. How much energy is released during the fission of one uranium-235 nucleus? 2. e=mc2 lol :smile: 3. I thought of putting them together but then how to separate them? 1.67495×10-27+3.903 05×10–25×c2=1.7539207313048996244767495×10-7 By the way, the answer is 4.73×10-11

Homework Statement An open cluster is observed to contain 1000 stars. Clusters contain many more low mass stars compared to high mass stars, reflecting the star formation process. This depen- dence of the number of stars formed in a given mass range is expressed in the so-called initial mass...

Hello all, Does anyone know the weight of a neutron? Or, better yet, does anyone know offhand the weight of hydrogen subscript 2 (hydrogen isotope with two neutrons)? Thanks!

I have just attended a talk, where the speaker (a professor in Hong Kong University) claims that neutron stars don't collapse due to "nuclear forces". He further explains that those nuclear forces are residual strong forces (i.e. exchange of pions). However, the mainstream saying (according to...

How do you strip a neutron from a particle? Thanks

Could anyone provide a concise explanation of the function of a discriminator in what is basically a, Detector => Pre-Amp => Amp => Discriminator => MCA (Multi-Channel Analyzer), circuit. I have a basic knowledge of electronics, but I'm still new to this. Thank you!

Hello all, this is my first post so hopefully its not overly foolish. I propose a mechanical piston driven by a cylinder that is filled with Uranium Hexafluoride and an inert gas (Nitrogen?). As the piston descends, the the UF6 is compressed and the neutron flux spikes. The increased...

Hello, So I'm reading about isospin in Griffith's Introduction to Elementary Particles, but the concept seems rather fishy, and I'm not quite sure what to make out of it. For example, if p and n (proton and neutron) are seen as different states of the same system, then what does...

Is there a well-established theory for temperature and cooling processes of neutron stars as a function of time?

Hi, I was reading about PWR control system and I saw that control rods are stainless steel tubes encapsulating a Hafnium absorber material , it has Excellent mechanical properties and exceptional corrosion-resistance properties allow its use in the harsh environment of a pressurized water...

Dear Forum, I have been given a DT fusion spectrum where neutrons are produced in the following reactions, DT = 14.1 MeV DD = 2.45 MeV TT = 0-9.8 MeV (three body spectrum) The spectrum is given in the form dN/dE. I have converted this spectrum into the dE/dE by multipling the...

I have been reading research papers on this topic, such as Evolution of the magnetic field in magnetars J. Braithwaite and H. C. Spruit 2006 http://www.aanda.org/index.php?option=com_article&access=doi&doi=10.1051/0004-6361:20041981&Itemid=129 This is informative but takes the...

Can anyone tell me, in detail, about Neutron - Proton interaction. Newbie here, so please use easy words(i know enough about quarks and gluons as well as strong interaction forces)

I recently saw the Evaluated Nuclear Data File provided by Brookhaven national lab., where in i saw the plot of "Neutron Energy Vs cross section (total)" for different elements. http://www.nndc.bnl.gov/sigma/index.jsp?as=1&lib=endfb7.0&nsub=10 Now what i am interested in is, can we derive or...

I have a scientific background in materials science. However this is one type of material that we don't exactly learn about! Let's say you have a neutron star approaching a comparable mass black hole. As the neutron star approaches the event horizon for such a comparable black hole, tidal...

Dear all, I am gautama currently pursuing my M.Tech in Fast breeder reactor at IGCAR. The project is based on the fuel sub assembly bowing due to thermal, swelling gradients. Using a FEM software ANSYS i have modeled the Sub assembly, but i am not able to give swelling parameter in ANSYS...

Dear friend, I am getting confused in this question;what i learned till now is that number of proton+number of neutron=atomic mass. But while searching the net i got this equation atomic mass = mass a x fract a + mass b x fract b. can anyone tell me which is the correct (not approximate)...

Homework Statement In a reactor, we're making 56Mn by inducing thermal neutron capture. 2g sample of 55Mn is put into the reactor which has a flux of thermal neutrons of 3E13 neutrons/cm^2*s Sample is in the reactor for 8 hours and then removed. a. Calculate the amount and activity of...

Homework Statement DT fusion produces 14.1 MeV neutrons. A diagnostic for a total fusion yield is the Cu-63( n, 2n)Cu-62 reaction. A) what is the threshold for this reaction? Cu-63 also undergoes a radiative capture reaction yielding Cu-64. This reaction has a thermal cross section of 4.5b...

Neutron star is said to have masses so compact that 10 miles of it would have more mass than the sun. For example two neutron star collides, can a small fragment be separated from it forming a meteor? And if a small piece were to enter Earth atmosphere and reach land. Would the neutron star as...

Homework Statement In an experimental setup (shown in attachment) like this for neutron diffraction, how do I find the wavelength of the neutron. It should be around 2nm. Homework Equations \lambda = \frac{h}{mv}=\frac{396}{v} The Attempt at a Solution I am having trouble with...

Homework Statement In an experiment carried out with a beam of thermal neutrons it is found that on traversing a 2mm thick foil of 197Au, some 70% of the neutrons are removed. What is the total thermal neutron cross-section for this isotope of gold? (Density of gold: 19300 kg m-3) Homework...

An electron and a proton can not form a neutron because they are short about 800KeV of energy. If we place an electron 200 fermi from a proton there is a strong electrostatic attraction. As the electron moves towards the proton electrostatic potential energy is converted to kinetic energy of the...

If I have a low energy neutron and I bring it close to a nucleus it will be captured when it gets close enough. How can I calculate the shape of the potential well of the nucleus for neutron capture? I keep reading that it is due to the strong force, which I agree with. But it is some...

After a supernova what compels the left over core to be either a neutron star or a pulsar? is it decided before or after explosion? any thoughts would be appreciated.

Specifically, what happens to the identical fermions in a neutron star as the neutron star collects additional mass that makes it into a black hole. Fermions cannot occupy the same state according to the Pauli exclusion principle, what happens to them in the black hole?

Neutron stars are held together by extremely strong gravitational force. What would happen to a chunk of the star if it had been removed and left to stand alone? Same question for a chunk of a white dwarf?

I recently read an article that said that experiments in synchotrons had indicated that an electron was the most spherical object in the universe. It stated that if an electron were the same diameter as the solar system, the variation in its diameter would be less than the thickness of a human...

From https://www.physicsforums.com/showthread.php?t=40391 in gravitational time dilation. At the center of neutron star PSR J1614-2230 at 1.97 SM mass of Sun 1.9891×10^30 kg mass of PSR J1614-2230. 4 ×10^30 gravitational constant = 6.67300 × 10-11 m3 kg-1 s-2 radius(rough estimate) =...

Eur. Phys. J. C (2006) THE EUROPEAN PHYSICAL JOURNAL C Digital Object Identifier (DOI) 10.1140/epjc/s2006-02479-8 Ultra low momentum neutron catalyzed nuclear reactions on metallic hydride surfaces A. Widom 1, L. Larsen 2 1 Physics Department, Northeastern University, 110 Forsyth Street...