Thermodynamics: Rankine Cycle and Efficiency

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Questions and Answers

What is the purpose of the Pilot Operated Safety Relief Valve (POSRV) in the pressurizer system?

To control the temperature of the reactor

To enhance the heating capacity of the coolant

For over-pressure protection and safety depressurization (correct)

To increase the coolant flow rate

Which material is used for the steam generator tubes to improve durability?

Carbon Steel

Titanium Alloy

Inconel 690 (correct)

Stainless Steel 304

What feature is included in the design of the reactor coolant pump to reduce leakage?

Single stage impeller design

Horizontal discharge

Vertical bottom suction

Face-type mechanical seals (correct)

How many tubes are used in each steam generator?

13,102 Signup and view all the answers

What is the primary function of the reactor vessel in the coolant system?

To contain the nuclear fission process Signup and view all the answers

What type of turbine is used in the power generation system?

Tandem-Compound Turbine Signup and view all the answers

What is the role of the coolant volume at full power in the pressurizer design?

Provide stability against RCS transients Signup and view all the answers

What is the speed of the turbine used in the generator?

1,800 rpm Signup and view all the answers

What happens to vapor in the Rankine Cycle after it expands through the turbine?

It generates electricity by spinning the turbine. Signup and view all the answers

What is the formula for thermodynamic efficiency in the Rankine Cycle?

η = Net Work Out / Heat Added Signup and view all the answers

In calculating the Carnot efficiency, what does THOT represent?

Temperature of the hot reservoir in absolute terms Signup and view all the answers

What is the absolute temperature conversion from 50°C?

321 K Signup and view all the answers

Which of the following represents an ideal cycle for thermal efficiency?

Carnot Cycle Signup and view all the answers

What phase occurs immediately after the vapor (wet) enters the condenser in the Rankine Cycle?

It turns back into liquid water. Signup and view all the answers

In a fossil fuel steam power plant, what type of energy is NOT directly converted?

Transition Energy Signup and view all the answers

What is initially done to the molten salt in a concentrating solar power plant?

It is heated to high temperatures using sunlight. Signup and view all the answers

What is the primary function of a Pressurized Water Reactor (PWR) in its cooling system?

To heat a steam generator to produce steam for power generation Signup and view all the answers

Which type of nuclear reactor uses thermal neutrons with energies less than 1 eV?

Thermal reactors Signup and view all the answers

What percentage of global electricity production was attributed to nuclear energy in 2012?

11% Signup and view all the answers

Which reactor type is known for its dual-loop cooling system?

Pressurized Water Reactor Signup and view all the answers

What is a unique characteristic of nuclear power that sets it apart from other energy sources?

Specialized technology and design knowledge Signup and view all the answers

Which of the following best describes the function of decay heat in nuclear reactors?

Generates thermal energy even after the reactor is shut down Signup and view all the answers

What type of nuclear reactor uses deuterium as a moderator?

Heavy Water Reactor Signup and view all the answers

Which energy source contributed 67% to global electricity production in 2012?

Fossil fuels Signup and view all the answers

What is the primary role of the fuel cladding in nuclear reactors?

To contain heat and seal the fuel pellets Signup and view all the answers

How many power reactors are currently under construction worldwide?

69 Signup and view all the answers

In which reactor type does water vaporization occur directly in the reactor core?

Boiling Water Reactor Signup and view all the answers

Which factor significantly influences the selection of nuclear reactor designs?

Neutron energy and moderator used Signup and view all the answers

What does the acronym GWe stand for in the context of nuclear power?

Gigawatts of electricity capacity Signup and view all the answers

What is the principal reason nuclear power tends to favor large-capacity power plants?

Economy of scale Signup and view all the answers

What critical factor is emphasized for nuclear power in terms of investment?

Considerable up-front investment Signup and view all the answers

Which technology is currently not in widespread use and is mentioned in relation to nuclear energy costs?

Carbon-capture technology Signup and view all the answers

How is nuclear power described in comparison to renewable sources of energy?

Cost-competitive Signup and view all the answers

What challenge is primarily associated with nuclear power due to its scale?

Need for large financial resources Signup and view all the answers

What is a potential disadvantage of nuclear energy mentioned concerning environmental technologies?

Lack of carbon-capture technology Signup and view all the answers

Why might large corporations find nuclear power appealing despite its costs?

Consistent energy output Signup and view all the answers

What is a common misconception regarding the financial aspects of nuclear power?

It has negligible upfront costs Signup and view all the answers

What is the primary purpose of Levelized Cost of Electricity (LCOE)?

To compare unit costs of different technologies over their economic lives Signup and view all the answers

Which of the following costs is NOT included in the LCOE calculation?

Employee salaries Signup and view all the answers

What does a high discount rate indicate regarding perceived investment risks?

It indicates a higher perceived investment risk Signup and view all the answers

How is the present value calculated in relation to future cash flows and the discount rate?

Future Value at time t divided by (1+r)^t Signup and view all the answers

Which variable is directly described as the interest rate used to evaluate future cash flows?

Discount rate (r) Signup and view all the answers

In the context of LCOE, what does 'E' represent?

Cost of producing electricity in year 't' Signup and view all the answers

Why must the discount rate (r) and time (t) be compatible in calculations?

To reflect the correct compounding intervals Signup and view all the answers

What does the term 'time-value of money' indicate in the context of the discount rate?

Money available now is worth more than the same amount in the future Signup and view all the answers

What does capital intensity reflect in power generation?

The vulnerability to changes in output price and demand Signup and view all the answers

Which power generation technology is mentioned as potentially having higher long-term cost efficiency?

Nuclear power plants Signup and view all the answers

What is the major contributor to lifetime cost (LCOE) according to the cost structure?

Capital investment Signup and view all the answers

Which of these risks is classified under market risk?

Electricity price fluctuations Signup and view all the answers

What is a noted challenge in the construction of new reactors?

Common construction delays and expenses Signup and view all the answers

For gas-powered plants, what is the largest contributor to LCOE?

Fuel costs Signup and view all the answers

What does the 5% discount rate indicate in the cost structure?

Different allocation of total cost components Signup and view all the answers

What is a noted uncertainty factor for carbon capture and storage technologies?

Considerable cost uncertainties Signup and view all the answers

Which risk relates to the licensing and approval processes for energy production plants?

Regulatory risk Signup and view all the answers

What factor impacts the operational costs and availability of power generation plants?

Consumer demand fluctuations Signup and view all the answers

Study Notes

Rankine Cycle Process

Vapor (dry) expands through turbine, causing the turbine to spin and generate electricity.
Vapor (wet) then enters the condenser.
The cycle restarts at point 1.

Thermodynamic Efficiency

Efficiency (η) is calculated as Net Work Out / Heat Added.
The Carnot Cycle efficiency (ηc) is calculated as (THOT - TCOLD) / THOT, where THOT is the high temperature and TCOLD is the low temperature.
Absolute temperature (T) is calculated as T(Absolute) = T(Centigrade) + 273°.
The Rankine cycle is less efficient than the Carnot cycle.

Fossil Fuel Steam Power Plant

Water is converted into steam.
Steam passes through a throttling valve.
The main turbine uses the steam to produce electricity.
The main condenser lowers steam temperature and pressure.
Chemical energy is converted into thermal, kinetic, and mechanical energy, finally to electrical energy.

Concentrating Solar Power Plant

Sunlight is concentrated by heliostats to a receiver.
Molten salt is pumped through the receiver and heated to 1050°F.
The heated salt is stored in a hot salt tank.
Molten salt is pumped from the hot salt tank through a steam drum to create steam to power a turbine and generator.
Cold salt flows back to the cold salt tank.

Nuclear Fueled Steam Plant

Nuclear energy is converted to thermal energy, then to kinetic energy and finally to mechanical energy and then into electrical energy.

Nuclear Fission Energy

Fissioning 1 kg of U-235 is equivalent to burning 3,000 tons of coal.
Uranium in nature is mostly U-238 (99.3%) and a smaller amount is U-235 (0.7%).

Where the Thermal Energy (Heat) Comes From

UO2 fuel pellets are enriched to 3-5% U-235.
The typical nuclear power system involves a reactor vessel, reactor core, containment structure, and turbine/generator/condenser.

Global Electricity Production (2012)

Fossil fuels make up 67% of global electricity production.
Renewables account for 22%.
Nuclear energy accounts for 11%.
Other sources including hydro, wind, solar, geothermal and biomass make up the remaining percentage.

World Nuclear Energy Production

Production has risen steadily from the 1980s, reaching a peak just before 2010.
The Fukushima nuclear accident in 2011 led to a drop in production.

Current Status of World Nuclear Power

The world currently has 439 nuclear reactors.
Approximately 380 GWe of installed capacity;
There are plans to build new capacity.
Current data is from January 2012.

Greenhouse Gas Emissions

The median life cycle GHG emissions for various sources show nuclear power as a much lower emission technology compared to others.

Energy Demand & CO2 Emissions

World primary energy demand is increasing, especially around 2020.
Fossil fuels still dominate energy demand and CO2 emissions.
Renewable energies are gaining market share.

Safety, Safeguards, and Security

Nuclear fuel, decay heat, nuclear waste and dual-use are unique characteristics of nuclear power plants

Typical Nuclear Power System

The essential components of a typical nuclear power plant.

NSSS - Reactor Vessel Internals

Fuel rods are grouped into assemblies.
Ceramic fuel pellets are stacked inside a metallic alloy case to form the fuel rod.
Fuel assembly is an organized structure.

Types of Nuclear Power Reactors

Reactors are categorized by neutron energy (thermal or fast) and moderator/coolant type.
Key reactor types include Light Water Reactors (PWR, BWR), Gas-cooled Reactors, and Heavy Water Reactors (CANDU).

Boiling Water Reactor (BWR)

Reactor coolant boils directly in the core, producing steam that drives the turbine.
Condensation and return to core complete the cycle.
Design is simpler than the PWR.

Pressurized Water Reactor (PWR)

Reactor coolant heats a separate steam generator, creating steam to drive the turbine.
Two distinct water circuits (primary and secondary) are used.

Canadian Deuterium-Uranium Reactors (CANDU)

Two distinct loops (primary and secondary) are used.

Gas-Cooled Reactor - Magnox CO2

Two loops are used in the gas-cooled reactor.
The graphite moderator, pressure vessel, fuel rods, etc, are all crucial components.

Nuclear power plants in commercial operation

Different reactor types, main countries, operational capacity, and fuel/coolant/moderator information.

Pressurized Water Reactor

The primary and secondary water loops do not mix.
Steam is generated in a secondary system and drives the turbine.

Reactor Power System Layout

Schematic presentation of the complete layout of a power reactor.

APR1400 Nuclear Steam Supply System in Containment

An illustration of the nuclear steam supply system within the containment.

NSSS - Reactor Vessel

The vessel's design and function as a pressure boundary.

NSSS - Reactor Coolant System

Configuration details of the coolant system, including components like a reactor vessel, pressurizer, steam generators, and circulating pumps, etc

NSSS - Steam Generator (SG)

Steam generator tube design and improvements for stability.

NSSS - Pressurizer

Pressurizer volume, values and pilot operated safety relief valves, protection of over pressure.

NSSS – Reactor Coolant Pump (RCP)

Vertical bottom suction, horizontal discharge, single stage impeller, shaft seal assembly, etc

Turbine & Generator

Details on the turbines (HP and LP turbines), generator type and voltage, frequency, etc.

What are the costs?

Costs related to power plant siting, licensing, construction, fuel, operations, maintenance and decommissioning.

Construction Costs

Comparison of construction costs for different energy sources.

Fuel Costs

Fuel costs for different power production technologies.

Operations and Maintenance Costs

O&M costs for different power production technologies.

Land Use & Cost of CO2 Emissions

Land use and carbon tax costs of various energy sources.

What are some incentives?

Government support (tax incentives, subsidies, loan guarantees) and industry options (consortia, alternative options, public opinion) for energy projects.

Economic Considerations

Levelized cost of electricity (LCOE) comparison methodology and calculation.

Discount Rate (r)

Interest rate determination of present value of future cash flows.
Accounts for time-value of money and investment risk.

Effect of Risk on Capital Costs: Intensity

Capital intensity analysis concerning the change in output prices and demand.

Cost & Capacity Comparison

Comparing costs and capacities using median case specifications.

Cost Structure

Cost Structure analysis considering 5% and 10% discount rates.

Main Risk Factors for Investment in Power Generation

Risk factors related to plant operation, market forces, regulation and policy measures, to be considered when estimating LCOE.