A report on Nuclear Energy Systems

                                   A report on Nuclear Energy Systems

Objectives

• To state the advantages and disadvantages of conventional nuclear reactor systems
• To plot the Kr- 85 decay cycle
• Recommend most applicable Nuclear reactor systems
• Address nuclear energy and waste management challenge

Introduction

Nuclear energy offers green power that is conducive to the environment. Currently, about 16% of the world’s electricity is supplied from atomic reactors. The USA only has about 435 operating nuclear reactor plants. Nuclear energy is effectively green energy at the front-end and back -end of a fuel cycle. Nuclear reactor plants are quite reliable and easy to construct. Due to this reason. Governments and utilities around the world are always reassessing the nuclear plant options as conditions change. Public opinion regarding these plants is now changing, and more nuclear reactor plants being set up. It has led to an additional 276 nuclear plant setups.

The primary material used in nuclear reactions is Uranium. The content is mined through either open pit, underground, or in-situ leaching method. Holes are drilled around 50meters apart, and a leaching solution is inserted on to the center hole. The solution consists of water, an oxidant aba ionic complex element designed to mobilize and dissolve Uranium. The solution is pumped out through the remaining hole, and Uranium is removed through the ion exchange method. The expelled solution is deoxidized, restored to proper pH, and recycled in the system.

Pressurized light water reactor systems (PWR)

It utilizes water pressure to send heat to produce high amounts of erythema core of the reactor is heated, and water at high pressures is pumped to the core. Heat energy produced at the fusion of atoms is carried away by the pressurized cold water and vaporizes power the main turbine generator hence creating electrical energy. These are the most common reactors in the US.

Advantages

Less power is produced as heat increases. By lowering the temperatures of the core, more energy can be created. Therefore, it is easy to operate and run. The reactors are also safe and easy to control since the materials used are less fissile and, therefore, fewer chances of later fusion reactions. Reactor plants are also clean and free of any form of contamination. The turbine cycle is set up in a manner that primary and secondary loops are separated; hence no contamination occurs.

Disadvantages

The reactor requires water to remain highly pressured so as for the reactor to function. However, this requires very strong pipes that are expensive to acquire. Therefore, construction costs are quite high. Also, the operating life span of the reactor plant is limited. A byproduct of the reaction is boric acid, which is corrosive and may damage the pipes. Replacing these is very expensive.

Boiling water reactors (BWR)

It utilizes normal tap water n a primary circuit below the boiling point. Steam is produced at a secondary circuit at 12 to 60 atm, at about 330 degrees Celsius steam and water are produced in the core of the reactor.

Advantages

The reactor plant does not require a generator or turbines to run. The reactor operates under low pressure hence does not require expensive piping to set up. Therefore, the operating lifespan of the BWR is higher than that of PWR.

Disadvantages

the nuclear recharging is required after every 18 months. It is, however, impossible to recharge without completely stopping the operations of the reactor. There is also a possibility of contamination that could lead to a plant explosion, mainly because it is hard to eliminate integrating contaminants in the reactor.

Sodium cooled fast reactors (SFR)

These utilize a temperature of 500-530 degrees Celsius in their outlets, at a pressure of approximately 1atmosphere.they are rated at 1000-5000 MWth and use metal oxide or metal alloy as fuel. The estimated burnout is about 100-150 GWD at an estimated conversion ratio of 0.5 -1.3 and an average power density of 350 MWth/cubic meter.

Advantages

The sodium liquid used as a coolant has a high ability to absorb heat; hence it is very useful as a coolant.it has a high specific heat capacity and therefore prevents overheating of the reactor system. Sodium does not require to be pressurized; hence it does not corrode steel pipes. It is also easy to pump molten sodium using electromagnetic pumps due to its electrical conductivity nature.

Disadvantages

Sodium is highly reactive, and if mishandled, it can cause fires. Also, it may be impossible to prevent sodium leakages.

Very high-temperature reactor systems (VHTR)

They have a reactor power of 600MWth and operate at reactor temperatures of 640/1000 degrees Celsius. They utilize Helium at a mass flow rate of 32kg/sec. The fuel component is a ZrC coated inform of pins pebbles or blocks. The plant has a net efficiency of of50%.

Advantages

Graphite rods used are non-reactive; hence the reactors are safe.it are also stable since graphite has high heat capacity. Its fuel is coated, and this allows for high burnouts of fission products.it has a higher life span of up to 60 years

Disadvantages

The reactors require material that is above the capacity of mostly operating reactors. Most of the needed materials, such as specific graphite standards are hard to manufacture.

Kr-85 decay cycle

It has a half-life of 10.16 years. Beta-decay yields 173Kev, followed by gamma decay yielding 514 Kev.

Discussion and conclusions

Despite nuclear energy offering clean green energy, most established reactors come with advantages and disadvantages. The reactor is classified depending on the energy production processes. Commonly used reactor systems include pressurized light water systems (PWR), boiling water reactors (BWR), heavy water reactors (CANDU), sodium-cooled fast reactors (SFR) and very high-temperature reactors (VHTR).

Among other fourth-generation reactors, sodium and gas-cooled reactors are more suitable. Sodium reactors are efficient and have a long lifespan. On the other hand, gas-cooled reactors are effective since they produce both hydrogen and electricity hence require low running costs. These would offer the best nuclear solutions for the USA.

When it comes to nuclear waste management, recycling is the solution. Disposable waste proves fatal to the environment. Therefore, policymakers should advocate for different ways to recycle the most; if not all, nuclear wasteful recycled waste can be safely stored within the plant to prevent harm to the natural ecosystem.

References

PowerPoint class notes on Energy Systems and Resources, Nuclear Science and Engineering Institute, University of    Missouri