All exercise Short Questions of Neuron Physics and Nuclear Fission of book Nuclear Physics for BS/MSc Physics students.
What is the classification of neutron according to energy?
The study of interaction of nuclei with neutron, the neutron is classified according to energy as follow.
- Slow neutron
- Fast neutron
- Intermediate neutron
- Very fast neutron
- Ultra fast neutron
What do you know about slow neutron?
Neutron whose kinetic energy is below about 1ev which is equal to 1.60217646×1019 J slow neutron frequently undergoes elastic scattering interaction with atomic nuclei.
What is monochromatic?
Special instrument for selecting highly mono chromatized neutron in the energy region known as monochromatic.
How we discuss about the categorized of slow neutron?
There are four categories of slow neutron.
- Cold neutron
- Thermal neutron
- Epithermal neutron
- Resonance neutron
What is the difference between cold and thermal neutron?
Cold neutron:
These have energy less than 0.002ev. They show very high penetrability through crystalline and poly crystalline material.
Thermal neutron:
Thermal neutron any free neutron that has an average energy motion corresponding to the average energy of particles of thr ambient materials.
Which neutrons are available in cosmic rays?
Ultra fast neutrons are available in cosmic rays.
What is epithermal neutron?
A neutron having an energy in the range immediately above the thermal range, that is having an energy between a few hundredths and approximately 100ev.
Why neutrons are not electrically charged?
Because the quarks that make up a neutron cancels each other.
Why neutron cannot lose energy by ionization?
Elastic scattering is the only way that low energy (below about 0.5Mev) neutron can be slowed as neutron have no charge and hence cannot be slowed by ionization energy losses.
Who is Fermi?
Encino Fermi was an Italian physicist and the creator of world’s first nuclear reactor the Chicago pile 1. He has been called the “Architect of the nuclear age and of the atomic bomb”.
Who discovered nuclear energy?
Encino Fermi.
What show that Fermi and his colleagues?
In 1934 they showed the neutron are slowed down in hydrogenous materials and the slower neutron have greater probability of inducing radioactivity then do more energetic neutron.
What is neutron moderator?
This is type of material in a nuclear reactor that works to slow down the fast neutron.
How do you make slow neutron?
In reactor when a large fissile atomic nucleus such as uranium-235 undergo nuclear fission.
Why are heavy nuclei not used as moderator?
The moderators used have light nuclei. Heavy nuclei will not serve the purpose because substances with heavy nuclei do not occur in liquid at room temperature.
Why does nuclear radiation occur in heavy nuclei but not in light nuclei?
Because the nuclei of heavy elements contain a large number of proton packed together in a very small space.
What is nuclear fission?
The subdivision of heavy nucleus into two fragments is called nuclear fission.
Who is James Chadwick?
He was on English physicist who was awarded the 1935 Nobel Prize in physics for his discovery of the neutron in 1932.
What do you know about James Chadwick experiment?
In 1932 Chadwick conducted an experiment in which he bombarded Beryllium with alpha particles from the natural radioactive decay of Polonium. The result is radiation show high penetration through a lead shield, which couldn’t be explained via the particles known at that time.
What is transuranic element?
The chemical elements with z>92 are called transuranic element.
Who is Bohr and John wheeler?
John Archibald Wheeler was an American theoretical physicist and invents the theory of nuclear fission. Niels Henrik David Bohr was a Danish physicist who made foundational contribution to understand atomic structure and quantum theory.
What is Bohr Wheeler theory of nuclear fission?
In 1939 they developed a theory of nuclear fission in term of deformation parameter or the on the basis of the liquid drop model of the nucleus.
What is the maximum binding energy of per nucleon?
A=56
What is region of stable nuclide?
The shaded region between A=50 to A=60 is called region of very stable nuclide.
Difference between fusion and fission region?
The region on left side of shaded region is called as fusion region.
The region on right side of shaded region is called as fission region.
What is the binding energy of per nucleon?
The nuclei near A=240 have binding energy per nucleon is 7.6Mev.
What is the maximum binding energy per nucleon?
The maximum binding energy of per nucleon is about 8.9Mev.
What is the binding energy per nucleon of middle nuclei?
The binding energy per nucleon of middle nuclei is about 8.5Mev.
What is the Q value of fission reaction?
The Q value of fission reaction is
Q= (Mx-MY-MZ) C2
What is the rest mass energy of any nucleus?
MC2=ZmpC2+NmnC2-EB
OR
Rest mass of stable nucleus of stable atom is always less than the sum of masses of constituent nucleons. The difference is called mass defect. The energy is known as binding energy.
Which has minimum binding energy per nucleon?
The binding energy of per nucleon is lowest for very light nuclei such as 2He4 is greatest around A=60 and then decreases with increasing A.
What is the nucleon number formula?
Nucleon Number is the number of proton plus the number of neutron.
What is the minimum value of nucleon number is?
The minimum value of A for which this fission is energetically favorable such that no external energy is needed can be calculated.
Is volume energy term avA will remain same before and after fission?
Yes, it is same.
The volume energy of two fragments Y and Z after fission.
Evy Evz=avA/2+avA/2
EvyEvz=avA
Difference between surface and coulomb energy?
The surface energy is the drop model wants to keep the nucleus spherical whereas coulomb energy wants to deform it.
What is surface energy in nuclear physics?
The surface energy is the reduction in the Binding Energy due to nuclear surface effect.
What is the difference between coulomb and asymmetry energy in nuclear physics?
The coulomb energy is the repulsion between protons.
The asymmetry energy is the reduction in B.E which occurs when there are more neutron then proton.
What is pairing energy?
The pairing energy is estimated as the,
Q=MxC2-MyC2-MzC2
Why pairing energy Eδ(A,z) is remain same?
The pairing energy term Eδ(A,Z) remain same because fission is taken as symmetric.
What is the unit of Q value?
Mev
What happened when Q value come our positive in pairing energy?
The Q value come our positive for A>100. It means there is spontaneous fission or energetically favorable fission for nuclei A>100. But there are so many nuclei with A>100 which are very stable. They don’t undergo in spontaneous fission.
Who can explain the fission mechanism by using liquid drop model?
Bohr and John Wheeler.
What is Bohr Wheeler theory of nuclear fission?
Bohr and Wheeler (1939) developed a theory of nuclear fission on the basis of the Liquid Drop Model of nucleus. On the basis of theory it is possible to calculate activation energy and critical energy for fission of different nuclei.
In first stage why nucleus start deforming?
The nucleus starts deforming because of some energy deposition.
What is deformation?
The deformation refers to modification of shape or size of an object due to applied forces or a change in temperature.
What do you about deformation parameter?
Bohr and Wheeler consider the nucleus as two loops. The distance between center of mass of these loops is taken as deformation parameter.
Define activation energy?
The difference between maximum energy and zero deformation energy is known as activation energy.
How do you calculate the magnitude of surface energy and coulomb energy for each stage of shape?
The magnitude of surface energy and coulomb energy for each stage of shape can be calculated by using semi empirical formula.
What is the semi empirical formula?
The semi empirical formula is
M (Z, A)=Zm(1H)+Nmn-B(Z,A)/C2.
Where is B.E B (Z, A) given by the following formula. We will now study each term in semi empirical mass formula.
Who gave semi empirical formula?
The German Physicist Carl Frie Drich Von Weizaker.
Does fission require activation energy?
In nuclear physics, the fission barrier is the activation energy required for a nucleus of an atom undergoes fission.
What do you know about fissile material?
The materials such as U235 which undergo in fission immediately are fissile material.
Which material absorb low neutron?
The fissile energy material absorb low neutron without facing any barrier.
Write the name of any two fissile materials?
Uranium – 233 and Plutonium – 239.
How we can calculate activation energy of 92U239??
The activation energy of 92U239 nucleus calculated by liquid drop model is 6.2Mev.
Write the characteristic of fission reaction?
The fragments X and Y are immediately formed when excited uranium –236 undergo in fission. There is no unique pair of fragment nuclei. It has different possibilities.
Which product of the nuclear fission of uranium—235 is utilized to cause further fission of nuclei?
The neutrons are the product of the nuclear fission of uranium—235 which are utilized to cause further fission of its nuclei.
Why uranium—238 can’t be used for fission?
Uranium can’t support a chain reaction because inelastic scattering reduces neutron energy below the range where fast fission of one or more next generation nuclei is probable.
What is a yield fragment?
The reaction products barium, krypton, xenon, strontium, cesium, rubidium, iodine, and yttrium in these reactions are called yield fragments.
Initial nucleus 2XA at A is E0.Nucleus at A/2 is E1.
Which model is not able to explain the asymmetric distribution?
Liquid drop model is not able to explain the asymmetric distribution.
What is symmetric fission?
The symmetric fission refers to any fission process where the end products are symmetric about some points.
What is excess neutron?
Light nuclei close to the N=Z line, but the stable isotopes of heavier nuclei require an excess of neutron to be stable.
Why are excess neutrons unstable?
Too many neutron or proton upset this balance disrupting the B.E from the strong nuclear forces making the nucleus unstable.
The Z—proton of initial nucleus are distributed in how many protons?
The Z—protons of initial nucleus are distributed as Z1 proton and Z2 proton in fragments.
What’s means that point (·) on dotted line indicates the ratios?
It means when a nucleus splits close to A/2 in two parts, the ratio N/Z remain same for these two parts as shown by points (·) on straight line. These points (·) are fragments.
What is prompt neutron?
These neutrons are emitted immediately after the fission. So the fission time scales are something like 10-14s to 10-14s. These neutrons called prompt neutron.
What is delayed neutron?
This is emitted by an excited nucleus among the fission product at an appreciable time interval after fission has occurred.
How are delayed neutron generated?
Delayed neutrons originate in the decay by neutron emission of nuclei produced in the β– decay of certain fission product with gradually decreasing intensity over a period of minutes.
Why does negative beta decay occur?
Beta decay tends to allow the nucleus to approach the optimal proton/ neutron ratio. When there are too many neutron related to the proton.
How does beta decay help unstable nuclei become more stable?
Beta decay changes proportion between number of protons and neutrons. This may in this way make a nucleus more strongly bound so more stable.
What do you means by fission fragments?
Fission fragments are themselves complex nuclei with usually between one-third and two-third the charge Z and mass A of the parent nucleus.
Is xenon is radioactive?
It will undergo through beta decay to get stability
54Xe140 55cs140 56Ba140 57La140 58Ce140 (stable)
These chain show 4 β-1 particles are emitted. Hence 4 neutrons are converted into proton one by one to attain stability.
What is chain of fission fragment of strontium and how many β-1 particles are emitted?
38Sr94 39Y94 40Ba94 (stable)
These chain show 2 β-1 particles are emitted. Hence 2 neutrons converted into protons one by one to attain stability.
What are fission fragments of uranium—235?
A common pair of fragments from uranium—235 fission is Xenon and Strontium.
What is prompt gamma ray?
The activation analysis is a measurement technique for nondestructive elemental analysis.
What is delayed gamma ray?
The most common form of delayed radiation. But are not the only form. It is common for the short lived isotopes to have delayed emission of various particles. In these cases, it is commonly called a beta delayed emission. This is because the delayed until beta decay take place.
Why it is difficult to trap antineutrino?
Because they pass through all kind of matter without interacting.
What is nuclear chain reaction?
A chain reaction refers to a process in which neutron released in fission produce an additional fission in at least one further nucleus.
What is the ratio of F/A depends upon?
The ratio F/A depend upon the amount of fissionable and non fissionable material and on their cross sections for fission and neutron captive.
Difference between critical mass and critical size?
The size of fission able material for which the multiplication factor K=1 is called critical size and its mass is called critical mass.
What do you know about Enrico Fermi led?
The team that built the first nuclear reactor, a controlled chain reaction machine. The reactor was built during the early days of world war second.
What was the “Manhattan Project”?
The code name for the effort to develop atomic bomb, for the united state during world war second. The first controlled nuclear reaction took place in Chicago in 1942.
Why was it called “Manhattan project”?
The name itself “Manhattan Project” is commonly thought to be a misnomer, but its first office was actually in Manhattan, at 270 Broadway.
What is Breeder Reactor?
Breeder reactor, nuclear reactor that produces more fissionable material than it consumes to generate energy.
What is meant by boiling water reactor?
The (BWR) boiling water reactor actually boils the water. In both types, water is converted to steam, and the recycled back into water by a part called condenser, to be used again in the heat process.
What is generator turbine?
To transform the energy of water, steam or wind into mechanical energy that will make the generator spin.
Write any two factors depend on nuclear reactor?
The nature of fuel.
The nature of the moderator.
Write any five basic part of the nuclear reactor?
- Coolant
- Moderator
- Reflector
- Shielding
- The fuel core
Difference between coolant and reflector?
The reactor coolant is a fluid. It should have high boiling point and low induced radioactivity known as coolant. The reflector is made up moderating material.
What is moderator?
A material such as ordinary water, heavy water, or graphite that is used in a reactor to slow down high- velocity neutron, thus increasing the likelihood of fission.
Which is used as moderator in reactor?
Water (sometime called “light water” in this context) is the most commonly used moderator (roughly 75% of the world’s reactor). Solid Graphite (20% of reactors) and heavy water (5% of reactors) are the main alternatives.
Write the name of any two good moderators?
H2, D2, and c12.
What is shielding?
Concrete or lead are used as main shielding materials, to safe guard and personal and equipment from the damaging effects of the radiation coming out from the reactor core.
What is heavy water?
Heavy water is mostly just like ordinary water (H2O) but with the regular hydrogen atom (H-1) replaced by atoms with an extra neutron (H-2). Unlike a lot of isotopes, H-2 has a special name we can call it besides hydrogen: Deuterium. Deuterium is sometimes given the symbol “D” so heavy water can be referred to as D2O. The name ‘heavy water’ is used because deuterium is twice as heavy as regular hydrogen.
What do neutron look like?
Neutrons are invisible just like all forms of electromagnetic and particle radiation (except for the visible portion of the light spectrum).
What is liquid metal fast breeder reactor?
A liquid metal fast breeder reactor (LMFBR) is nuclear reactors capable of producing more fissile product than it take in. breeder exhibit remarkable fuel economy compared to light water reactor.
Why neutrons are neutral?
Neutrons are made up of two down and one up quarks. One up quark has a charge +2/3, and the two down quarks each have a charge of -1/3. The fact that these charges cancel out.
Why free neutron is unstable?
When the mass of this nucleus is higher than the sum of the masses of the daughter nucleus + electron + antineutrino. It is stablished in the opposite case. In this energy balance, the very small mass of the antineutrino is often neglected.
Nuclei with A>100 are feasible for decay but remain stable?
An atom is stable if the forces among the particles that makeups the nucleus are balanced.
What is the function of pressurized water in reactor?
The core inside the reactor vessel creates heat. Pressurized water in the primary coolant loop carries the heat to the steam generator. Inside the steam generator, heat from the primary coolant loop vaporizes the water in a secondary loop, producing steam.
What are the properties of ideal moderator?
The moderator should efficiently slow down the neutron. It should be in pure form. It should be thermally stable. It should have good heat conducting property.
What is the function of control rod?
A rod, plate, or tube containing a material such as hafnium, boron, e, t, c, used to control the power of a nuclear reactor. By absorbing neutron, a control rod prevents the neutrons from causing further fission.
What are fissile materials?
The materials such as U235 which undergo in fission immediately are called fissile material?
Difference between delayed neutron and prompt neutron?
Prompt neutron.
These neutrons are emitted immediately after the fission. So the fission time scale is 10-14s.
Delayed neutron.
Which is emitted by an excited nucleus among the fission product at an appreciable time interval after fission is occurred.
Differentiate between power reactor and research reactor?
Research reactors are small nuclear reactors that are primarily used tp produce neutron, unlike power reactor, which are larger and used to generate electricity.
U233 Is a fissile material but U238 is not, Give reason.
U cannot sustain a nuclear fission chain reaction because too many neutrons produced by the fission of U238 have lower energies than the original neutron.
