Nuclear Energy Flashcards
What are the criticisms of nuclear energy?
Too dangerous, too slow, too expensive
Approximately how many nuclear plants are there in Country US?
Country US has about 96 nuclear plants.
Which three countries are the top users of nuclear power?
The top three countries using nuclear power are the United States, France, and China.
What percentage of global electricity was generated by nuclear power in 2018?
Nuclear power generated about 10% of electricity globally in 2018.
How many nuclear reactors are operating worldwide?
420 reactors are operating worldwide.
How many operational reactors are there in the UK, and what is their total capacity?
15 operational reactors in the UK at 7 sites, with a capacity of 8.9GW.
What types of reactors are among those operational in the UK and give an example?
The UK has 14 Advanced Gas-cooled Reactors (AGR) and 1 Pressurised Water Reactor (PWR), for example, Hinkley Point B
What percentage of the UK’s electricity needs are generated by nuclear power?
15%
What are some safety features of the Hinkley Point C PWR?
- Double containment for aircraft impact resistance
- Core melt spreader to prevent criticality
- Refueling water storage tank.
Who are the key players in the current status of nuclear power in the UK?
EDF and they have plans for subsequent European Pressurised Reactors (EPR) at Sizewell in Suffol
Why do some isotopes release radiation ‘spontaneously’?
Some isotopes are unstable and decay ‘spontaneously’, releasing radiation as a part of reaching a more stable state.
What role do neutrons play in the nucleus?
Neutrons act like glue within the nucleus, due to the strong force and their interaction with quarks, to hold the nucleus together.
What determines the chemical element of an atom?
The number of protons in the nucleus determines the chemical element.
What can a nucleus eject during radioactive decay?
A nucleus can eject alpha particles (Helium nucleus), beta radiation (electron), and emit gamma rays, which are waves indicating a change in nuclear energy levels.
How can neutrons induce nuclear processes?
Neutrons, having no charge, readily penetrate the atom and can hit the nucleus, leading to neutron scattering (neutron bounces off), neutron absorption (increasing atomic mass, possibly followed by alpha or beta decay), or fission.
What happens during fission?
During fission, the nucleus fragments into two or more smaller elements, known as fission products, generating heat and releasing more neutrons. This process typically occurs with large nuclei like Uranium and Plutonium, which are known as fissile materials, and releases between 2 and 3 neutrons.
What is the result of the decay of fission product fragments?
Fission product fragments undergo radioactive decay, which further contributes to the release of energy and radiation.
How many neutrons are produced on average in each fission event of U-235 and Pu-239?
On average, each fission event produces 2.47 neutrons for U-235 and 3 for Pu-239.
What is necessary for a chain reaction to occur in nuclear fission?
For a chain reaction to occur, enough neutrons must cause further fission events, with the potential for the reaction to become self-sustaining if the conditions allow.
What is a cross-section in the context of nuclear fission?
In nuclear fission, the cross-section is the probability that fission or any other neutron-induced reaction will occur.
What happens to neutrons during fission?
During fission, neutrons could either fly out or scatter, be absorbed, or cause further fission.
What are the two main fissile isotopes of natural uranium used in reactors?
The two main fissile isotopes of natural uranium used in reactors are U-235 and U-238.
How can U-238 become a fissile material?
U-238 can become fissile by undergoing neutron capture and beta-decay to become Pu-239
What happens to the fission cross-section as neutron velocity is reduced?
increases particularly in the resonance region
How can a nuclear chain reaction be maintained?
To maintain a nuclear chain reaction, the amount of U-235 can be increased through enrichment, or the neutrons can be slowed down through moderation
What distinguishes thermal reactors from fast reactors in terms of fuel and neutron speeds?
Thermal reactors slow down neutrons to thermal energies using a moderator. Fast reactors do not use moderation but require a higher enrichment level, around 20% U-235.
Why are most nuclear reactors thermal?
Most nuclear reactors are thermal because the chances of fission occurring are much higher when neutrons are moving at slower speeds, around 10^3 meters per second, which can be achieved by moderating the neutrons to thermal energies.
What happens during neutron moderation?
During neutron moderation, the speed of neutrons is reduced to enhance the likelihood of fission. This is typically achieved through elastic collisions with atoms that have low atomic masses.
Can you name some examples of moderators used in nuclear reactors?
Examples of moderators used in nuclear reactors include graphite, H2O (light water), and D2O (heavy water).
What is the effective neutron multiplication factor, and what does K_eff = 1 indicate?
Measures the change in the neutron population from one generation to the next in a reactor. K_eff = 1 indicates a state of criticality, where the reactor is stable and the chain reaction is self-sustaining without increasing or decreasing in intensity.
How must a reactor run to sustain a chain reaction with the help of delayed neutrons?
A reactor must run sub-critical in terms of prompt neutrons but rely on delayed neutrons, which are released fractions of a second after fission, to sustain the chain reaction.
