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nuclear 2 Flashcards

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1
Q

Who proposed the idea of atoms and what was his proposal?

A

Democritus, in the 5th century BC, proposed the idea that all matter was made up of little, identical lumps called “atomos.”

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2
Q

Who proposed the atomic theory in 1804, and what were its key points?

A

John Dalton proposed the atomic theory in 1804, suggesting that matter was made up of tiny spheres (atoms) that couldn’t be broken up. He believed that each element was composed of a unique type of atom.

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3
Q

What significant discovery did J. J. Thomson make about atoms nearly 100 years after John Dalton’s proposal?

A

J. J. Thomson discovered that electrons could be removed from atoms, demonstrating that Dalton’s theory, which suggested that atoms were indivisible, was not entirely accurate. This discovery challenged the notion that atoms could not be broken up.

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4
Q

What model of the atom did J. J. Thomson propose?

A

J. J. Thomson proposed the “plum pudding” model of the atom, suggesting that atoms were spheres of positive charge with tiny negative electrons embedded within them, similar to fruit in a plum pudding.

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5
Q

Who was the first to propose the idea of the nucleus, and what was the significance of this proposal?

A

Ernest Rutherford was the first to suggest the idea of the nucleus. This proposal was significant because it challenged the prevailing notion that atoms had uniformly distributed charge and density, leading to a new understanding of atomic structure.

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6
Q

What experiment did Rutherford and Marsden conduct in 1909?

A

Rutherford and Marsden fired a beam of alpha particles at thin gold foil.

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7
Q

How did Rutherford and Marsden detect the deflection of alpha particles in their experiment?

A

They used a circular detector screen surrounding the gold foil and the alpha source to detect alpha particles deflected by any angle.

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8
Q

What did Rutherford and Marsden expect to observe in their experiment regarding the deflection of alpha particles?

A

They expected that the positively-charged alpha particles would be deflected by the electrons by a very small amount if the plum pudding model of the atom was true.

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9
Q

What unexpected observation did Rutherford and Marsden make regarding the behavior of alpha particles in their experiment?

A

Instead of being deflected by a small amount as expected, most of the alpha particles passed straight through the foil, while a small number were deflected by a large angle.

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10
Q

What particularly surprising observation did Rutherford and Marsden make about the deflection of alpha particles in their experiment?

A

Some alpha particles were deflected by more than 90°, sending them back in the direction they came from. This unexpected result was confusing at the time and prompted the need for a significant change to the model of the atom.

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11
Q

What conclusions did Rutherford draw from the results of his scattering experiment?

A

*Most of the atom must consist of empty space, as most alpha particles passed straight through the foil.

*The nucleus must possess a large positive charge, as some positively-charged alpha particles were repelled and deflected by a large angle.

*The nucleus must be small, as very few alpha particles were deflected back.

*Most of the mass of the atom must reside in the nucleus, since fast alpha particles (with high momentum) were deflected by the nucleus.

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12
Q

What approach can be used to determine how close an alpha particle can get to a gold nucleus in Rutherford scattering?

A

The initial kinetic energy of the alpha particle is known when it is fired at the gold nucleus.
An alpha particle that “bounces back” and is deflected through 180° reaches a point where its electric potential energy equals its initial kinetic energy.
This is based on the principle of conservation of energy and can be used to find how close the particle can get to the nucleus.
Coulomb’s law can be employed to calculate the electric potential energy.

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13
Q

What equation is used to calculate the electric potential energy in Rutherford scattering?

A

Ek = Eelec = Qgold x Qalpha/4πε0r

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14
Q

What does the distance of closest approach in Rutherford scattering provide an estimate of, and how does it compare to the values obtained from electron diffraction?

A

The distance of closest approach in Rutherford scattering provides an estimate of the nuclear radius, giving a maximum value for it

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15
Q

What type of particle are electrons, and how does this relate to their interaction with the strong nuclear force?

A

Electrons are a type of particle called a lepton. Leptons do not interact with the strong nuclear force, unlike neutrons and alpha particles. This lack of interaction allows electron diffraction to be an accurate method for estimating the nuclear radius.

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16
Q

What concept allows electron beams to be diffracted?

A

Electrons, like other particles, exhibit wave-particle duality, meaning they can exhibit both particle-like and wave-like behavior. This allows electron beams to be diffracted.

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17
Q

What is the equation for the de Broglie wavelength associated with a beam of moving electrons?

A

λ =hc/ E

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18
Q

Why must the wavelength of electrons be very small to investigate the nuclear radius, and what does this imply about their energy?

A

The wavelength of electrons must be very small to investigate the nuclear radius effectively. This implies that the electrons will have very high energy.

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19
Q

What happens when a beam of high-energy electrons is directed onto a thin film of material in front of a screen?

A

A diffraction pattern will be observed on the screen.

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20
Q

What is the equation for the angle at which the first minimum appears in the diffraction pattern of electrons?

A

sin θ = 1.22λ/2R

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21
Q

What does the diffraction pattern of electrons resemble?

A

The diffraction pattern of electrons resembles that of a light source shining through a circular aperture, with a central bright maximum (circle) containing the majority of the incident electrons, surrounded by other dimmer rings (maxima).

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22
Q

What does the diffraction pattern of electrons resemble?

A

The diffraction pattern of electrons resembles that of a light source shining through a circular aperture, with a central bright maximum (circle) containing the majority of the incident electrons, surrounded by other dimmer rings (maxima).

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23
Q

How does the intensity of the maxima change as the angle of diffraction increases, and what type of graph might represent this intensity?

A

The intensity of the maxima decreases as the angle of diffraction increases. A graph showing the relative intensity of electrons in each maximum may be presented, and it could be a logarithmic plot where the difference in peak heights is less pronounced.

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24
Q

What is the approximate radius of an atom?

A

The approximate radius of an atom is about 0.05 nm which is equivalent to 5 × 10–11 m

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25
What are nucleons, and what is the nucleon number of an atom?
Nucleons are the particles that make up the nucleus, including protons and neutrons. The nucleon number represented by A is the total number of nucleons in an atom. As more nucleons are added to the nucleus, it increases in size.
26
What factors can contribute to the instability of a nucleus?
Having too many neutrons, Not having enough neutrons, or Having too much energy in the nucleus.
27
What process describes the transformation of an unstable nucleus into a stable form?
The process is called radioactive decay, during which the nucleus releases energy and/or particles until it reaches a stable form.
28
What term describes the phenomenon when a radioactive particle knocks off electrons from an atom, creating an ion?
This phenomenon is known as ionizing radiation, and radioactive emissions are also referred to as ionizing radiation because they have the ability to create ions by knocking off electrons from atoms.
29
Is radioactive decay predictable?
No, individual radioactive decay events are random and cannot be predicted.
30
What is the function of a cloud chamber in detecting ionizing particles?
A cloud chamber contains air saturated with vapor at a very low temperature. When an ionizing particle passes through, it leaves a visible track of condensed vapor droplets due to ionization of the air.
31
What type of tracks do alpha particles produce in a cloud chamber?
Alpha particles produce straight tracks that radiate from the source and are easily visible. The tracks are all of the same length, indicating that the alpha particles have the same range.
32
What type of tracks do beta particles produce in a cloud chamber?
Beta particles produce wispy tracks that are easily deflected as a result of collisions with air molecules. The tracks are not as easily visible as alpha particle tracks because beta particles are less ionizing.
33
What is the count rate, and how is it calculated?
The count rate is the number of counts detected per unit time. It is calculated by dividing the number of counts by the time taken.
34
What must be done before testing a radioactive source to measure its count rate?
Before testing a radioactive source, the count rate due to background radioactivity must be measured. This is the count rate without the source present.
35
What is done to determine the corrected count rate from a radioactive source?
The count rate is measured with the source at a fixed distance from the detector tube without any absorber present. Then, the background count rate is subtracted from the count rate with the source present to give the corrected (true) count rate from the source.
36
What is done to compare the effect of an absorber on the count rate from a radioactive source?
The count rate is measured with the absorber in a fixed position between the source and the detector tube. Then, the corrected count rates with and without the absorber present can be compared to assess the effect of the absorber.
37
How does paper and thin metal foil interact with alpha radiation?
Alpha radiation is absorbed completely by paper and thin metal foil.
38
How does about 5mm of metal interact with beta radiation?
Beta radiation is absorbed completely by about 5mm of metal.
39
How does several centimeters of lead interact with gamma radiation?
Gamma radiation is absorbed completely by several centimeters of lead.
40
What is the Geiger tube?
The Geiger tube is a sealed metal cube containing argon gas at low pressure.
41
What purpose does the thin mica window serve in the Geiger tube?
The thin mica window allows alpha and beta particles to enter the tube.
42
How does the Geiger tube detect gamma photons?
Gamma photons can enter the tube through the tube wall.
43
What is the function of the metal rod in the Geiger tube?
The metal rod down the middle of the tube is at a positive potential.
44
How is the Geiger tube connected to a power supply?
The tube wall is connected to the negative terminal of a power supply and grounded.
45
What does the dead time represent in a Geiger tube?
The dead time represents the time taken for the tube to regain its non-conducting state after an ionizing particle enters it.
46
How does the dead time affect the count rate in a Geiger tube?
During the dead time, another particle that enters the tube will not cause a voltage pulse. Therefore, the count rate should be no greater than about 5000 counts per second.
47
What is the range of alpha radiation in air?
The range of alpha radiation in air is fixed but depends on its energy, ranging up to about 100 mm.
48
What is the range of beta radiation in air?
The range of beta radiation in air can be up to about 1 meter.
49
How does the range of gamma radiation in air behave?
The range of gamma radiation in air follows the inverse square law
50
How does alpha radiation behave in a magnetic field?
Alpha radiation is deflected in a magnetic field.
51
How does beta radiation behave in a magnetic field compared to alpha particles?
Beta radiation is deflected in the opposite direction to alpha particles and is more easily deflected.
52
What is the behavior of gamma radiation in a magnetic field?
Gamma radiation is not deflected in a magnetic field.
53
What is the absorption capability of paper or thin metal foil for alpha particles?
What is the absorption capability of paper or thin metal foil for alpha particles?
54
How thick of aluminum can stop beta particles?
How thick of aluminum can stop beta particles?
55
What material can stop or significantly reduce gamma radiation?
Gamma radiation is stopped or significantly reduced by several centimeters of lead.
56
How many ions per millimeter in air does the ionization of alpha radiation produce at standard pressure?
The ionization of alpha radiation produces about 10^4 ions per millimeter in air at standard pressure.
57
How many ions per millimeter in air does the ionization of beta radiation produce at standard pressure?
The ionization of beta radiation produces about 100 ions per millimeter in air at standard pressure.
58
What is the ionization effect of gamma radiation?
Gamma radiation has a very weak ionizing effect.
59
How did Rutherford demonstrate the nature of alpha particles?
Rutherford devised an experiment in which alpha particles were collected as a gas in a glass tube fitted with two electrodes. When a voltage was applied to the electrodes, the gas conducted electricity and emitted light.
60
What did Rutherford observe when he analyzed the light emitted by the alpha particles?
Using a spectrometer, Rutherford proved that the spectrum of light from the tube was the same as from a tube filled with helium gas.
61
What changes occur during alpha decay?
Alpha decay reduces the mass number of the element by -4 and the atomic number by -2.
62
What is the composition of an alpha particle?
An alpha particle consists of two protons and two neutrons, making it identical to a helium-4 nucleus.
63
What is beta minus decay?
Beta decay is the release of an electron and an electron neutrino by the change of a neutron to a proton.
64
What is beta plus decay?
Beta plus decay occurs when a proton turns into a neutron, emitting a positron (anti-electron) and an electron neutrino.
65
What is electron capture?
Electron capture is a process in which a parent nucleus captures one of its orbital electrons and emits a neutrino.
66
What is the abbreviation for atomic mass unit?
the abbreviation for atomic mass unit is u
67
How is the atomic mass unit defined?
The atomic mass unit is defined as 1/12 of the mass of a carbon-12 atom.
68
69
Why is ionizing radiation hazardous to living cells?
Ionizing radiation affects living cells by damaging cell membranes, leading to cell death, and by damaging vital molecules such as DNA directly or indirectly.
70
How does ionizing radiation damage vital molecules like DNA?
Ionizing radiation can damage DNA directly or indirectly by creating 'free radical' ions, which react with vital molecules. This affects normal cell division, damages nuclei, and may cause cells to divide and grow uncontrollably, leading to tumor formation, which may be cancerous.
71
What are the potential long-term consequences of DNA damage caused by ionizing radiation in sex cells?
Damage to DNA in sex cells (i.e., eggs or sperm) may cause mutations that can be passed on to future generations.
72
Why must anyone using equipment that produces ionizing radiation wear a film badge?
Anyone using equipment that produces ionizing radiation must wear a film badge to monitor their exposure to ionizing radiation.
73
What does a film badge contain?
A film badge contains a strip of photographic film in a light-proof wrapper.
74
How is exposure to different forms of ionizing radiation estimated using a film badge?
Different areas of the film are covered by absorbers of different materials and thicknesses. When the film is developed, the amount of exposure to each form of ionizing radiation can be estimated from the blackening of the film.
75
What happens if a film badge is overexposed?
If the badge is overexposed, the wearer is not allowed to continue working with the equipment.
76
How are risks associated with ionizing radiation reduced?
Risks associated with ionizing radiation are reduced by increasing the distance from sources and shortening the time of exposure.
77
What is background radiation?
ackground radiation is radiation that occurs naturally from sources such as cosmic radiation and radioactive materials in rocks, soil, and the air.
78
How does background radiation vary with location?
Background radiation varies with location due to local geological features. For example, radon gas, which is radioactive, can accumulate in poorly ventilated areas of buildings in certain locations.
79
What are some sources of background radiation in the UK?
Sources of background radiation in the UK include cosmic radiation and radioactive materials in rocks, soil, and the air.
80
Why should storage of radioactive materials be in lead-lined containers?
Storage of radioactive materials should be in lead-lined containers because most radioactive sources produce gamma radiation as well as alpha or beta radiation. The lead lining of a container must be thick enough to reduce the gamma radiation from the sources in the container to about the background level.
81
What additional requirements do regulations impose on the storage of radioactive materials?
Regulations require that containers storing radioactive materials are under 'lock and key' and that a record of the sources is kept.
82
What is the purpose of using handling tools for transferring radioactive sources?
The purpose of using handling tools is to ensure that the material is as far from the user as practicable, reducing the intensity of the radiation from the source at the user to as low as possible. Additionally, it ensures that the user is beyond the range of alpha or beta radiation from the source.
83
How should liquid and gas sources, as well as solids in powder form, be stored?
Liquid and gas sources, as well as solids in powder form, should be stored in sealed containers.
84
What is the purpose of storing these materials in sealed containers?
Storing them in sealed containers ensures that radioactive gas cannot be breathed in and radioactive liquid cannot be splashed on the skin or ingested.
85
What happens to the nucleus of a radioactive isotope when it emits an alpha or beta particle?
When a nucleus of a radioactive isotope emits an alpha or beta particle, it becomes a nucleus of a different element because its proton number changes.
86
How does the number of nuclei of the initial radioactive isotope change after emitting alpha or beta particles?
The number of nuclei of the initial radioactive isotope decreases.
87
What happens to the mass of the initial radioactive isotope as the number of nuclei decreases?
The mass of the initial isotope decreases gradually as the number of nuclei decreases.
88
What is a decay curve?
A decay curve shows how the mass of the isotope decreases with time.
89
How does the mass of the isotope change with time according to measurements?
Measurements show that the mass decreases exponentially, meaning that the mass drops by a constant factor (e.g., x0.8) in equal intervals of time.
90
What is the half-life of a radioactive isotope?
The half-life of a radioactive isotope is the time taken for the mass of the isotope to decrease to half the initial mass.
91
How is the half-life represented?
The half-life is represented by the symbol T(1/2)
92
ow does the mass of a radioactive isotope decrease over time?
The mass of a radioactive isotope decreases exponentially over time due to radioactive decay being a random process.
93
What is the activity of a radioactive isotope?
The activity (A) of a radioactive isotope is the number of nuclei of the isotope that disintegrate per second.
94
What is the unit of activity for radioactive decay?
The unit of activity is the becquerel (Bq), where 1 Bq = 1 disintegration per second.
95
What is the formula for radioactive decay?
The activity (A) of a radioactive isotope equals the decay constant (λ) times the number of radioactive nuclei (N). A=λN
96
What is the formula for the number of radioactive nuclei after a certain time in radioactive decay?
The number of radioactive nuclei (N) equals the initial number of radioactive nuclei (N0) times e raised to the power of negative (λ * t) N=N0e^-λt
97
What is the formula for the activity of a radioactive substance at a certain time in terms of its initial activity and decay constant?
The activity (A) equals the initial activity (A0) times e raised to the power of negative (λ * t). A=A0e^-λt
98
What is the decay constant (λ) in radioactive decay?
The decay constant (λ) is the probability of an individual nucleus decaying per second
99
What is the formula for calculating the half-life (T₁/₂) of a radioactive isotope?
T₁/₂ = ln(2) / λ
100
what does ln 2 =
0.693
101
How is carbon-14 (^14C) formed in the atmosphere?
Carbon-14 is formed in the atmosphere when cosmic rays knock out neutrons from nuclei, which then collide with nitrogen nuclei to form carbon-14 nuclei.
102
How is carbon-14 dating used to determine the age of organic material?
Carbon-14 dating relies on measuring the activity of carbon-14 in organic material. Living plants take in carbon dioxide containing carbon-14 through photosynthesis, maintaining a constant level of carbon-14. When a plant dies, it stops taking in carbon-14, and the existing carbon-14 decays over time. By comparing the activity of carbon-14 in a dead sample to that of living material, scientists can calculate its age.
103
How is trapped argon used in dating ancient rocks?
Trapped argon, resulting from the decay of potassium-40 (^{40}K), is used to date ancient rocks. When potassium-40 decays, it captures an inner-shell electron, converting a proton into a neutron and emitting a neutrino. This process forms argon-40 (^{40}Ar), which gets trapped in the rock. By measuring the ratio of potassium-40 to trapped argon-40, scientists can determine the age of the rock
104
What is a radioactive tracer used for?
A radioactive tracer is used to follow the path of a substance through a system. This is achieved by introducing a radioactive isotope into the substance and then measuring its presence or concentration at various points in the system.
105
What are the characteristics of a suitable radioactive isotope for use as a tracer?
should have a half-life stable enough for necessary measurements but short enough to decay quickly after use. It should emit alpha or beta radiation, or gamma radiation, so it can be detected outside the flow path.
106
What does a graph of neutron number (N) against proton number (Z) for all known isotopes reveal about nuclear stability?
Stable nuclei lie along a belt curving upwards with an increasing neutron-proton ratio from the origin to approximately N = 120, Z = 80.
107
What is the neutron-proton ratio like for beta minus and beta plus emitters?
The neutron-proton ratio is high for beta minus emitters and low for beta plus emitters.
108
What is the largest stable nuclide?
209-83Bi
109
Where do most alpha-emitting nuclides lie on the N-Z plot?
Most alpha-emitting nuclides lie above the top of the stability belt on the N-Z plot.
110
Where do alpha-emitting nuclides smaller than 209Bi typically lie on the N-Z plot?
Alpha-emitting nuclides smaller than 209Bi typically lie below the N-Z stability belt on the plot.
111
What relationship exists between the numbers of protons (Z) and neutrons (N) for stable nuclei with light isotopes?
For stable nuclei with light isotopes (Z from 0 to no more than 20), the relationship is represented by the straight line N = Z. These nuclei have equal numbers of protons and neutrons.
112
What happens to the neutron/proton ratio as the atomic number (Z) increases beyond about 20?
As the atomic number (Z) increases beyond about 20, stable nuclei have more neutrons than protons. This increase in the neutron/proton ratio helps to bind the nucleons together without introducing repulsive electrostatic forces as more protons would do.
113
What is a metastable state?
A metastable state refers to a long-lived excited state of a nucleus. In this state, the nucleus remains in an excited state long enough to be separated from the parent isotope.
114
What is the purpose of a technetium generator in hospitals?
A technetium generator is used in hospitals to produce a source which emits gamma radiation only. It separates technetium isotopes, particularly technetium-99m, which is widely used in medical imaging.
115
What is the purpose of a gamma camera in medical imaging?
A gamma camera is designed to "image" internal organs and bones by detecting gamma radiation from sites in the body where a gamma-emitting isotope such as 99Tc(m) nuclei is located. It is used, for example, to locate bone deposits using a phosphate tracer labeled with 99Tc(m).
116
What equation did Einstein propose in his theory of special relativity?
Einstein proposed the equation E=mc^2, which shows the equivalence of mass and energy, stating that the mass of an object increases (or decreases) when it gains (or loses) energy.
117
What is the binding energy of the nucleus?
The binding energy of the nucleus is the work that must be done to separate a nucleus into its constituent neutrons and protons.
118
What is the mass defect of a nucleus?
The mass defect Δm of a nucleus is defined as the difference between the mass of the separated nucleons and the mass of the nucleus.
119
How is the binding energy of a nucleus calculated?
the binding energy of a nucleus is calculated as the product of the mass defect and the speed of light squared: E = mc^2.
120
How does an alpha particle form and escape from a nucleus?
An alpha particle forms when two protons and two neutrons bind together as a cluster within a large nucleus. Due to its high binding energy (about 7 MeV per nucleon), the alpha particle gains enough kinetic energy to tunnel out of the nucleus, a process known as quantum tunneling.
121
What is the binding energy per nucleon of a nucleus?
The binding energy per nucleon of a nucleus is the average work done per nucleon to remove all the nucleons (protons and neutrons) from a nucleus. It is a measure of the nucleus's stability. For example, the binding energy per nucleon of the 212Bi nucleus is 8.4 MeV per nucleon.
122
What is nuclear fission?
Nuclear fission is the process in which a large unstable nucleus splits into two fragments, which are more stable than the original nucleus.
123
What is nuclear fusion?
Nuclear fusion is the process of making small nuclei fuse together to form a larger nucleus. The product nucleus has more binding energy per nucleon than the smaller nuclei.
123
What is induced fission?
Induced fission is the process in which a nucleus undergoes fission when bombarded with neutrons, leading to the splitting of the nucleus into two approximately equal fragments.
124
What is a chain reaction in nuclear fission?
A chain reaction in nuclear fission occurs when fission neutrons released in a fission event collide with other 235U nuclei, causing further fission events and the release of more fission neutrons, leading to a self-sustaining reaction.
125
Why does nuclear fusion require high-speed collisions?
Nuclear fusion requires high-speed collisions to overcome the electrostatic repulsion between the two nuclei, allowing them to come close enough to interact through the strong nuclear force.
126
What are the components of a thermal nuclear reactor in a nuclear power station?
The components include fuel rods, control rods, a coolant (such as water in a pressurized water reactor), a reactor core, a heat exchanger, steel pipes, a pump, and turbines.
127
What is the composition of enriched uranium in fuel rods?
Enriched uranium consists mostly of U-238 and about 2-3% U-235.
128
What is the function of control rods in a nuclear reactor?
Control rods absorb neutrons to regulate the rate of fission reactions and maintain a constant energy output.
129
What is the function of control rods in a nuclear reactor?
Absorb neutrons;The function of control rods in a nuclear reactor is to absorb neutrons.
130
How are the depth of control rods in the core adjusted?
Automatically;The depth of control rods in the core is automatically adjusted.
131
Why is the depth of control rods adjusted in a nuclear reactor?
To keep the number of neutrons constant;The depth of control rods is adjusted to keep the number of neutrons constant.
132
What effect does pushing the control rods further into the core have on the rate of fission energy release?
Reduces the rate of fission energy release;Pushing the control rods further into the core reduces the rate of fission energy release.
133
Why do fission neutrons need to be slowed down significantly?
To cause further fission of U-235 nuclei;Fission neutrons need to be slowed down significantly to cause further fission of U-235 nuclei.
134
Why would fission neutrons be unable to cause further fission if they are traveling too fast?
They would be traveling too fast to cause further fission;If fission neutrons are traveling too fast, they would be unable to cause further fission.
135
What surrounds the fuel rods in a nuclear reactor to slow down neutrons?
Moderator;Fuel rods in a nuclear reactor are surrounded by a moderator to slow down neutrons.
136
What is the purpose of a moderator in a nuclear reactor?,
To slow down neutrons;The purpose of a moderator in a nuclear reactor is to slow down neutrons.
137
Why is the reactor described as a thermal nuclear reactor?
Because fission neutrons are slowed down to kinetic energies comparable to the moderator molecules;The reactor is described as a thermal nuclear reactor because fission neutrons are slowed down to kinetic energies comparable to the moderator molecules.
138
In a Pressurized Water Reactor (PWR), what substance acts as both moderator and coolant?
Water;In a Pressurized Water Reactor (PWR), water acts as both moderator and coolant.
139
What condition must be met for a chain reaction to occur in a fissile material?
Mass must be greater than the critical mass;For a chain reaction to occur, the mass of the fissile material must be greater than the critical mass.
140
Why is it important for the mass of the fissile material to exceed the critical mass?
To prevent too many fission neutrons from escaping;It's important for the mass of the fissile material to exceed the critical mass to prevent too many fission neutrons from escaping.
141
Why is a mass less than the critical mass insufficient for sustaining a chain reaction?
Too many fission neutrons escape due to high surface area to mass ratio;A mass less than the critical mass is insufficient for sustaining a chain reaction because too many fission neutrons escape due to the high surface area to mass ratio.
142
What is the critical mass?
Minimum mass required for a chain reaction;The critical mass is the minimum mass required for a chain reaction.
143
What is the purpose of the thick steel vessel surrounding the reactor core?
To withstand high pressure and temperature;The thick steel vessel surrounding the reactor core is designed to withstand high pressure and temperature.
144
What role does the thick concrete walls of the reactor building play?,
,Absorb neutrons and gamma radiation;The thick concrete walls of the reactor building absorb neutrons and gamma radiation.
145
How are fuel rods inserted and removed from the reactor?
By remote handling devices;Fuel rods are inserted and removed from the reactor by means of remote handling devices.
146
Why are fuel rods much more radioactive after removal from the reactor?,
Due to fission byproducts accumulating in the fuel rods;Fuel rods are much more radioactive after removal from the reactor because of fission byproducts accumulating in the fuel rods.
147
How is intermediate-level radioactive waste stored?
Sealed in drums encased in concrete;Intermediate-level radioactive waste is sealed in drums encased in concrete.
148
Where are these drums stored?
In specially constructed buildings with walls of reinforced concrete;These drums are stored in specially constructed buildings with walls of reinforced concrete.
149
How is high-level radioactive waste stored in some countries?
In the same way as intermediate-level waste, or in underground caverns;In some countries, high-level radioactive waste is stored in the same way as intermediate-level waste, or in underground caverns.

physics (11 decks)

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