NUCLEAR POWER PROCESS - NUCLEAR FISSION PROCESS - RADIOACTIVE DECAY

Radioactive decay, also known as nuclear decay or radioactivity, is the process by which a nucleus of an unstable atom loses energy in the form of radiations. A material that spontaneously emits this kind of radiation - which includes the emission of energetic alpha particles, beta particles, and gamma rays - is considered radioactive. When unstable nuclei decompose in nature, the process is referred to as natural radioactivity or spontaneous radioactivity. When the unstable nuclei are prepared in the laboratory, the decomposition is called induced radioactivity.

Fission is a splitting of something into two parts.

In nuclear physics and nuclear chemistry, nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei).

The fission process often produces free neutrons and photons (in the form of gamma rays), and releasing a very large amount of energy. When a nucleus fissions, it splits into several smaller fragments. These fragments, or fission products, are about equal to half the original mass. Two or three neutrons are also emitted. The sum of the masses of these fragments is less than the original mass. This 'missing' mass has been converted into energy according to Einstein's equation:

                                                E = mc²

Fission can occur when a nucleus of a heavy atom captures a neutron, or it can happen spontaneously.

The Fission Process

A neutron travels at high speed towards a uranium-235 nucleus. A neutron travels towards a uranium-235 nucleus. The neutron strikes the nucleus which then captures the neutron. The nucleus changes from being uranium-235 to uranium-236 as it has captured a neutron. The uranium-236 nucleus formed is very unstable. It transforms into an elongated shape for a short time.

The uranium-236 nucleus formed is very unstable. It transforms into an elongated shape for a short time. The uranium-236 nucleus formed is very unstable. It transforms into an elongated shape for a short time. It then splits into 2 fission fragments and releases neutrons. It then splits into 2 fission fragments and releases neutrons.

Nuclear Chain Reactions:

A chain reaction refers to a process in which neutrons released in fission produce an additional fission in at least one further nucleus. This nucleus, in turn, produces neutrons, and the process repeats. The process may be controlled (nuclear power) or uncontrolled (nuclear weapons). 

Image from University of Florida

U²³⁵ + n → fission + 2 or 3 n + 200 MeV

If each neutron releases two more neutrons, then the number of fissions doubles each generation. In that case, in 10 generations there are 1,024 fissions and in 80 generations about 6 x 10 ²³ fissions.

1 MeV (mega electron volts) = 1.609 x 10 ^-13 joules

Uranium-235 combines with a neutron to form an unstable Uranium-236, which quickly splits into barium-144 and krypton-89 plus three neutrons in the process of nuclear fission.

Image from University of Dehli

Energy from Fission

Both the fission fragments and neutrons travel at high speed.  The kinetic energy of the products of fission are far greater than that of the bombarding neutron and target atom.

E_K before fission << E_K after fission

Energy is being released as a result of the fission reaction. The energy released can be calculated using the equation:

                                    E = mc²

Where:

E = energy released (J)

m = mass difference (kg)

c = speed of light in a vacuum (3 x 10⁸ ms^-1)

The energy released from this fission reaction does not seem a lot. This is because it is produced from the fission of a single nucleus. Large amounts of energy are released when a large number of nuclei undergo fission reactions. Each uranium-235 atom has a mass of 3.9014 x 10^-25 kg.

The total number of atoms in 1 kg of uranium-235 can be found as follows: No. of atoms in 1 kg of uranium-235 = 1/3.9014 x 10^-25.  No. of atoms in 1 kg of uranium-235 = 2.56 x 10²⁴ atoms

If one uranium-235 atom undergoes a fission reaction and releases 2.385 x 10^-11 J of energy, then the amount of energy released by 1 kg of uranium-235 can be calculated as follows:

total energy = energy per fission x number of atoms

total energy = 2.385 x 10^-11 x 2.56 x 10²⁴

total energy = 6.1056 x 10¹³ J

Critical mass:

Although two to three neutrons are produced for every fission, not all of these neutrons are available for continuing the fission reaction. If the conditions are such that the neutrons are lost at a faster rate than they are formed by fission, the chain reaction will not be self-sustaining.

At the point where the chain reaction can become self-sustaining, this is referred to as critical mass.

In an atomic bomb, a mass of fissile material greater than the critical mass must be assembled instantaneously and held together for about a millionth of a second to permit the chain reaction to propagate before the bomb explodes. To maintain a sustained controlled nuclear reaction, for every 2 or 3 neutrons released, only one must be allowed to strike another uranium nucleus.

If this ratio is less than one then the reaction will die out; if it is greater than one it will grow uncontrolled (an atomic explosion). A neutron absorbing element must be present to control the amount of free neutrons in the reaction space.

Most reactors are controlled by means of control rods that are made of a strongly neutron-absorbent material such as boron or cadmium.

The nuclear force (or nucleon–nucleon interaction or residual strong force) is the force between two or more nucleons. It is responsible for binding of protons and neutrons into atomic nuclei. The energy released by such binding causes the masses of nuclei to be less than the total mass of the protons and neutrons which form them; this is the energy used in nuclear power and nuclear weapons. The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers, but rapidly decreases to insignificance at distances beyond about 2.5 fm. At very short distances less than 0.7 fm, it becomes repulsive, and is responsible for the physical size of nuclei, since the nucleons can come no closer than the force allows. So, if you feel anything important missed from here so you can comment below and mention How Electrical.

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ELECTRICAL CIRCUIT COMPLETE TRAINING COURSE

We launched "Electrical Engineering Training Course"  in sub-branch of electrical engineering to learn about How electrical works and what is the latest technology in Electrical field and what's going on? So, the course name is "Electrical Circuit" in this course you can learn about these following topics,

• DC Circuits
• Ohm's law
• Kirchhoff's laws
• voltage
• current
• voltage and current division
• nodal and mesh analysis
• network theorems
• AC circuits analysis
• phasor concepts
• AC power
• Three phase AC circuits
• Introduction to electronics and digital logics

You should have a background of the following topics:

1. Coulomb's Laws
2. Magnetic and electric fields.
3. Dielectrics and capacitice.
4. Resistance and electric curcuits.
5. Electromagnetic induction.

Upon successful completion of this course, the student should be able to:

1. Understand the definitions of basic electrical quantities, Ohm's and Kirchhoff’s laws, and differences between practical/ideal sources.

2. Analyse simple series and parallel resitive circuits and simplify series/parallel connected sources and resistors.

3. Implement general nodal and mesh analysis and other circuit analysis techniques and select between them to achieve optimal solution.

4. Understand the concept of the sinusoidal forcing function and anlayse R/L/C cirucits in the frequency domain and convert the solution to the time domain.

5. Three phase circuits, and power calculations.

6. Basic electronics, and Basic Operational Amplifier circuits and systems.

7. Basic Digital Logic gates and Systems. Introduction to Programmable Logic Controllers (PLC)

Course Topics:

Units, charge, current, voltage, and power. Independent and Dependent voltage and current sources. Ohm's law.

Branches, nodes, paths, loops, and meshes. Kirchhoff's current and voltage laws. Single node and loop circuits. Reduction of series or parallel circuits. Voltage and current division.

Nodal voltage analysis and super-node. Mesh current analysis and super-mesh. Nodal vs. mesh analysis. Computer aided circuit analysis.

Linearity and superposition. Thevinin's and Nortons theorems, Source transformations, max. Power transfer, delta () – wye (Y) conversion. Selecting an optimal technique for solution.

The capacitor and inductor. Inductance and capacitance combinations.

Characteristics of sinusoids. The phasor and relationships of single phase for R, L, and C elements. Impedance and admittance. Circuit analysis techniques. R, L& C series and parallel resonance circuits. Phasor diagrams. Three-phase circuits, Wye (Y) and Delta () balanced sources and loads.

Power calculations for single and three phase circuits; power factor, power triangle. Power factor (improvement) correction.

Basic electronics including; p-n junction, diodes, transistors, simple transistor amplifier circuits, basic Operational Amplifiers (OPAMP), and applications.

Basic digital logic systems including: Numbering systems, Boolean’s algebra, Basic logic gates, basic digital circuits and systems. Introduction to Programmable Logic Controllers (PLC).

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WHY WE USE AC MOTOR INSTEAD OF DC MOTOR - APPLICATIONS OF AC MOTORS AND APPLICATIONS OF DC MOTORS

For electrical technology, Motor is known as the main unit of electrical technology. because of motor use in all industries with all machines and usually all the places normally. the Electrical motor is the main sub-sub-branch of electrical engineering because it is not easy to learn all concepts about electrical motor technology. There are many types and kinds of electrical motors like,

1. AC motors
2. DC motors

and there are also differents kinds in AC motors and DC motors as synchronous motors, induction motors, explosion proof, low voltage and motor with permanent magnet etc.

Where We Use AC Motors:

The alternating current electric motor (AC motors) are ideal for most applications linear, for fans, pumps, compressors, mills, machine tools, boilers, robots, generators and in many other products categories.
As regarding the choice of the type of electric motor for a given application, this is influenced by different factors, starting from the costs of purchase and operation, the yield, the efficiency, the periodic maintenance.

Where We Use DC Motors:

A DC motor is an electric motor that runs on direct current power. In any electric motor, the operation is dependent upon simple electromagnetism. A current carrying conductor generates a magnetic field, when this is then placed in an external magnetic field, it will encounter a force proportional to the current in the conductor and to the strength of the external magnetic field Resources and Information. is a device which converts electrical energy to mechanical energy. It works on the fact that a current carrying conductor placed in a magnetic field experiences a force which causes it to rotate with respect to its original position. Practical DC Motor consists of field windings to provide the magnetic flux and armature which acts as the conductor.

Applications of DC Motors

Series Motors

The series DC motors are used where high starting torque is required, and variations in speed are possible. For example – the series motors are used in Traction system, Cranes, air compressors.

Shunt Motors

The shunt motors are used where constant speed is required and starting conditions are not severe. The various applications of DC shunt motor are in Lathe Machines, Centrifugal Pumps, Fans, Blowers, Conveyors, Lifts, Weaving Machine, Spinning machines, etc.

Compound Motors

The compound motors are used where higher starting torque and fairly constant speed is required. The examples of usage of compound motors are in Presses, Shears, Conveyors, Elevators, Rolling Mills, Heavy Planners, etc.

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ELECTRICAL POWER | ENERGY METER DISCUSSIONS

Theory: - 

Energy meter is an instrument which measures electrical energy. It is also known as watt-hour (Wh) meter. It is an integrating device. There are several types of energy meters single phase induction type energy meter are very commonly used to measure electrical energy consumed in domestic and commercial installation. Electrical energy is measured in kilo watt-hours (kWh) by this energy meter. 

Construction: - 

A single phase induction type energy meter consists of driving system, moving system, braking system and registering system. Each of the systems is briefly explained below. 

Driving system: -

This system of the energy meter consists of two silicon steel laminated electromagnets. M1 & M2 as shown in fig.1The electromagnet M1 is called the series magnet and the electromagnet M2 is called the shunt magnet. The series magnet M1 carries a coil consisting of a few turns of thick wire. This coil is called the current coil (CC) and it is connected in series with the circuit. The load current flows through this coil. The shunt magnet M2 carries a coil consisting many turns of thin wire. This coil is called the voltage coil (VC) and is connected across the supply it consist of current proportional to the supply voltage. Short circuited copper bands are provided on the lower part of the central limb of the shunt magnet.

By adjusting the position of these loops the shunt magnet flux can be made to lag behind the supply voltage exactly 90° . These copper bands are called power factor compensator (PFC). A copper shading band is provided on each outer limb of the shunt magnet (fc1 &fc2) these band provides frictional compensation.

Moving system: -

The moving system consists of a thin aluminium disc mounted on a spindle and is placed in the air gap between the series and the shunt magnets. It cuts the flux of both the magnet forces are produced by the fluxes of each of the magnets with the eddy current induced in the disc by the flux of the other magnets. Both these forces act on the disc. These two forces constitute a deflecting torque.

Braking system: -

The braking system consists of a permanent magnet called brake magnet. It is placed near the edge of the disc as the disc rotates in the field of brake magnet eddy current are induced in it. These eddies current react with the flux and exert a torque. This torque acts in direction so that it opposes the motion of disc. The braking torque is proportional to the speed of the disc.

Registering system: -

The disc spindle is connected to a counting mechanism this mechanism records a number which is proportional to the number of revolutions of the disc the counter is calibrated to indicate the energy consumed directly in kilo watts-hour (kWh)

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DC NETWORK THEOREM - ELECTRICAL ENGINEERING BASIC

Current: “Rate of flow of electric charge.”

time

Charge

I = Coulombs/Sec or Ampere

Note:-

1. Direction of current is same as the direction of motion of +Ve charge or opposite to the direction of

motion of –Ve charge.

Voltage: “Energy required in transferring a charge of one coulomb from one point to

another point.”

Charge(Q)

Energy(W)

V = Joule/Coulomb or Volts

EMF (Electromotive force): “The EMF of a voltage source is the energy imparted by

the source to each coulomb of the charge passing through it.”

Charge(Q)

Energy(W)

E = Joule/Coulomb or Volts

Potential Difference: “The pd between two points is the energy required in transferring a

charge of coulomb from one point to another point.”

Charge(Q)

Energy(W)

pd = Joule/Coulomb or Volts

Voltage drop: “The voltage drop between two points is the decrease in energy required

in transferring a charge of coulomb from one point to another point.”

Charge(Q)

Energy(W)

Voltage drop = Joule/Coulomb or Volts

Resistance: “Electric resistance is the property of material which offers opposition to the

flow of current and dissipates energy.”

a

l

R = ñ Ohm or _ (Law of resistance)

Where l = Length of the wire

a = cross − sectional area of the wire

ñ = Resistivity or Specific Resistance of the material

Note:-

1. Resistance also depends on temperature.

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WHAT IS COHESIVE DEVICES? DISCUSSIONS

Coherence in writing means achieving a consistent relationship among parts. Cohesive devices show the logical relationships between the various parts of an essay as well as between sentences and paragraphs.

Cohesive devices include: transitional words and expressions,  paragraph hooks

cohesive devices are like bridges between parts of your paper

They are cues that help the reader to interpret ideas in the way that you, as a writer, want them to understand cohesive devices help you carry over a thought from one sentence to another, from one idea to another, or from one paragraph to another with words or phrases.

cohesive devices link your sentences and paragraphs together smoothly so that there are no abrupt jumps or breaks between ideas.

Cohesive words and phrases  are used to link sentences and paragraphs, to show which direction your thought patterns are going, to help the reader accurately follow your train of thought.

They signal the relationships among the various parts of your subject.

Types Of Cohesive Devices

There are several types of cohesive devices, and each category leads your reader to make certain connections or assumptions about the areas you are connecting.

Some lead your reader forward and imply the "building" of an idea or thought,

while others make your reader compare ideas or draw conclusions from the preceding thoughts.

Before, meanwhile, later, soon, at last, earlier, thereafter, afterward, by that time, from then on, first, next, now, presently, shortly, immediately, finally

Likewise, similarly, once again, once more

But, yet, however, although, whereas, though, even so, nonetheless, still, on the other hand, on the contrary As a result, consequently, therefore, hence, for this reason

I knew my dieting had gotten out of hand, but when I could actually see the movement of my heart beating beneath my clothes, I knew that I was in trouble. At first, the family doctor reassured my parents that my rapid weight loss was a “temporary phase among teenage girls.” However, when I, at fourteen years old and five feet tall, weighed in at 63 pounds, my doctor…

Transition words are audience cues that help the reader shift from one paragraph to the next.

These connections between paragraphs help the reader see the relationships of the various parts.

Transition words or phrases at the beginning of a new paragraph—such as first, second, next, another, finally, on the other hand, however—show the reader where the essay is going next.

In addition to transition words, writers often tie paragraphs together by repeating a key word or idea from a previous paragraph in the opening sentence of the next paragraph.

This “hooks” the paragraphs together, creating for the reader a logical flow of thought.

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DC MACHINES AND COMPUTER AIDED DESIGN QUESTIONS FOR PRACTICES

1. Determine diameter and length for 100 Kw, 230V, 750 rpm, 6 pole dc machine. How the choice is made for selecting pole numbers in a dc machine.

2. Find the suitable number of poles and the dia. of the core of a 400Kw, 550 V, 180 rpm d.c. generator having 92% efficiency. Assume an average flux density in the air gap of about 0.6 wb/m² and ampere conductor per meter to be 35000.

3. Explain the use of a digital computer in designing of an electrical machine giving its advantages and limitations.

4. Give Computer Aided Design approaches  by the following methods:

(a)    Analysis

(b)   Synthesis

(c)    Hybrid

5. Give concept of optimization as applied to the design of electrical machines. Name some of the optimization techniques employed in design and briefly describe its general procedure.

6. Explain the design procedure for design of stator of a 3-phase turbo-alternator and write a flow chart to estimate the main dimensions. What statements will have to be changed to make the same program valid for a water wheel generator.

7. If the design data of a single phase transformer is known, write flow chart for determining % regulation and efficiency at different load currents and power factors.

8. Give design procedure for design of rotor of a wound rotor induction motor.

9. Explain, with flow chart, how the performance of a water wheel generator may be estimated from the design data and what steps can be taken to improve the performance.

10. Write a flow chart to design a d.c. machine and estimate its efficiency.

11. Write a procedure to obtain the leakage reactance of a 3-phase core-type transformer with concentric winding with its relevant computer flow chart and indicate how the value of leakage reactance be controlled by design parameters.

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INDUCTION MOTOR QUESTIONS FOR PRACTICES

1.      Drive the output equation of a 3-phase induction motor and also explain how the magnetic and electric loading is selected.

2.      Write down the steps to find out the main dimensions of a 3-phase IM. Also draw a flow chart for it.

3.      Explain and find out flux density in stator teeth.

4.      Explain how the rotor is designed of a 3-phase ship ring induction motor. Also draw a flow chart for it.

5.      Estimate the stator slot leakage reactance for 1-Layer winding.

6.      Write down step by step how the circle diagram is drawn for an induction motor?

7.      Calculate the main dimension, turns per phase, Number of conductors, slots, cross-section of the  conductor of a 50 KW, 415 volts, 3 phase,, 50 Hz, 1000 RPM, slip ring  induction motor. Given B_av = 0.52T, η= 0.9, pf =0.89 lagging, =32000 ac /m, δ= 5A /mm².

8.      A 20-kw, 3-phase, 6-pole, 50-Hz, 400 V delta connected cage rotor induction motor has 54 stator slots, each containing 10 conductors. Design suitable number of rotor slots and determine the value of bar and end ring currents. The machine has efficiency of 85% and power factor 0.85 lagging. Also find the bar and end ring sections, if current density is 6.0 A/mm². Assume rotor mmf as 85% of the stator mmf.

9.      Describe the significance of B₃₀ in a  3-phase induction motors. A 75 kw, 3300V, 50 Hz, 8-pole, 3-ph, star connected induction motor has a magnetizing current which is 35% of full load current. Calculate the number of stator winding turns per phase if the mmf required for flux density at 60⁰ from the inter polar axis is 500 A. Assume winding factor = 0.95, full load efficiency = 0.94 and full load power factor = 0.86.

10.  Estimate the main dimensions & air gap length for a 3-phase, 20 HP, 400 V, 6-pole, 50 Hz, 970 RPM induction motor suitable for a star-delta starting. Assume magnetic and electric specific loadings as 0.45 wb/m² and 23000 ac/m respectively, ratio of core length to pole pitch 0.85, full load efficiency 0.88 and power factor 0.89.

11.  Estimate the main dimensions, number of radial ducts, number of stator slots, number of turns per phase, conductors per slot and slot dimensions for 7.5 kW, 415 V, 3-phase, delta-connected, 4-pole, 50 Hz squirrel-cage induction motor. The flux per pole is 0.015 Wb. Assume efficiency 85% and power factor as 0.85 lagging.

12.  Determine the main dimensions, turns per phase, number of slots, conductor section and slot area of 200 H.P, 3 phase, 50Hz, 400 Volts, 1480 r.p.m. slip ring induction motor. Assume Bav = 0.5 wb/m², ac = 30,000 amp conductor / meter, efficiency = 0.9 and power factor = 0.9, current density = 3.5 amp per mm².

13.  Design a 10 HP, 415 V, 3-phase, 50 Hz, 1440 rpm, squirrel cage induction motor. The machine is to be started by a star delta starter. Assume all suitable data yourself.

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