write on (i) Cloud chamber (ii) pressurized water reactor (iii) breeder reactor
(i) Cloud Chamber:
A cloud chamber is a scientific device used to visualize and study the paths of charged particles, such as cosmic rays or particles from radioactive decay. It consists of a sealed, transparent container filled with a supersaturated vapor (usually alcohol or water vapor). To create a cloud in the chamber, the air pressure is lowered, causing the vapor to condense and form tiny droplets. When a charged particle passes through the chamber, it ionizes molecules along its path, causing the droplets to condense into visible wisps or tracks, revealing the particle's trajectory.
To understand the working principle of a cloud chamber, you can follow these steps:
1. Obtain a clear, airtight container: You can use a glass jar or a rectangular box with a transparent side.
2. Prepare a volatile fluid: Alcohol or a mixture of isopropyl alcohol and water is commonly used in cloud chambers. Ensure that the fluid is clean and free from impurities.
3. Cool the container: You can achieve this by placing a cooling plate or a layer of dry ice at the bottom of the container. Cooling helps in supersaturating the vapor.
4. Seal the container: Make sure the container is tightly sealed to prevent any airflow.
5. Create a pressure difference: Use a vacuum pump to reduce the pressure inside the container. Alternatively, you can create a temperature gradient by applying heat at the top to cool the bottom. This temperature difference will initiate condensation at the cool end.
6. Observe particle tracks: As charged particles, such as alpha or beta particles, pass through the chamber, the vapor molecules along their paths will ionize, causing condensation trails or tracks to form. These can be observed by illuminating the chamber with a light source at an angle or using a source of ionizing radiation nearby.
Remember that cloud chambers require appropriate safety precautions since they involve handling volatile substances and potentially radioactive sources for particle generation.
(ii) Pressurized Water Reactor (PWR):
A pressurized water reactor, commonly abbreviated as PWR, is a type of nuclear power reactor used to generate electricity. It operates by utilizing enriched uranium fuel to produce heat through nuclear fission, which is then used to produce steam to drive a turbine-generator system. Here's a simplified explanation of how a PWR works:
1. Fuel and control rods: The reactor core contains fuel assemblies composed of enriched uranium fuel pellets. Control rods are also inserted into the core to help regulate the nuclear reaction.
2. Coolant circulation: Water serves as the coolant and moderator in a PWR. It is maintained at high pressure to prevent boiling. The pressurized water is circulated through the reactor core to absorb the heat generated by the fission reactions.
3. Heat transfer: As the hot pressurized water passes through the fuel assemblies, it absorbs the heat produced by nuclear fission and becomes even hotter.
4. Steam generation: The hot water from the primary loop transfers its heat to a secondary loop via a heat exchanger. In the secondary loop, another water source is converted to steam, which is then used to drive a turbine.
5. Turbine and electricity generation: The high-pressure steam flows through the turbine, causing its blades to spin. The turbine converts the steam's kinetic energy into mechanical energy, which is used to turn a generator and produce electrical power.
6. Cooling and condensing: After passing through the turbine, the now low-pressure steam is condensed back into water in a condenser. The condensed water returns to the heat exchanger to be reheated and restart the cycle.
(iii) Breeder Reactor:
A breeder reactor is a type of nuclear reactor designed to produce more fissile material than it consumes while generating electric power. It achieves this through the process of nuclear transmutation, where non-fissile materials, such as uranium-238, are converted into fissile materials, like plutonium-239. The basic working principle of a breeder reactor is as follows:
1. Fuel and coolant: Similar to other nuclear reactors, a breeder reactor uses a fuel, commonly a combination of uranium and plutonium, in the form of ceramic pellets. The coolant, usually liquid sodium or a molten salt mixture, circulates through the reactor core to transfer the heat generated by the nuclear reactions.
2. Neutron multiplication: Neutrons, which are released during nuclear fission, are crucial for sustaining the chain reaction. In a breeder reactor, the core design and the presence of fertile materials allow for a higher number of neutrons produced than consumed. These surplus neutrons are used to convert non-fissile materials into fissile ones.
3. Breeding process: As the reactor operates, non-fissile uranium-238 captures neutrons and transmutes into plutonium-239. The generated plutonium-239 can then be extracted, reprocessed, and used as fuel in the reactor.
4. Control systems: Breeder reactors require precise control mechanisms to optimize the breeding process and avoid excessive neutron absorption or fuel losses. Control rods made of materials that absorb neutrons, such as boron or hafnium, are used to regulate the neutron population and prevent potential instabilities.
5. Energy production: Like conventional reactors, a breeder reactor transfers the heat generated by nuclear reactions to a coolant, which then drives a turbine-generator system to produce electricity.
It's worth noting that breeder reactors have the potential to significantly increase fuel efficiency and reduce plutonium waste, but they also pose challenges in terms of complex design, safety, and waste management.