UNIT 3. TRANSMUTATION REACTIONS. FISSION AND FUSION REACTIONS.

1. Warming up

1.1What can you see in the pictures? What nuclear reactions do they show?

2. Reading

2.1. Pre-reading tasks

1. Study and learn the following structures:

1. Chemical changes are associated with the change in the chemical composition of the substance.

2. The radioactive elements, which tend to decay under natural conditions, are readily involved in chemical reactions to form new elements.

3. Fission as encountered in the modern world is a deliberately produced man-made nuclear reaction induced by a neutron.

4. The hydrogen bomb uses an atomic bomb in order to start fusion reactions.

5. The process of transmutation can be represented in terms of chemical reaction as it is also a conversion of one element into another.

2. Read the following key-terms. Try to explain their meaning. Use the dictionary if necessary:

Nuclear reaction, transmutation, artificial, bombard, fission, fusion

2.2. Mark the following statements as true or false. Read the text and check your ideas:

1. The process of transmutation can be done by artificial manner only.

2. Nuclear fission is either a nuclear reaction or a radioactive decay process.

3. The energy released by fusion is equal to the energy released by fission.

2.3. Read and translate the article:

TRANSMUTATION REACTIONS. FISSION AND FUSION REACTIONS.

We know that physical changes are associated with the change in the physical state of matter whereas chemical changes are associated with the change in the chemical composition of the substance.

The radioactive elements, which tend to decay under natural conditions, are readily involved in chemical reactions to form new elements (radioactive or non-radioactive) with the emission of some radiations. The reactions, which involve the radioactive materials to form new nuclei, are called nuclear reactions. The nuclear reactions must accelerate to achieve the extreme energies needed for their reactions.

Transmutation is a process in which nucleus changes in the number of protons to produce an atom with a different atomic number. The process of transmutation can be represented in terms of chemical reaction as it is also a conversion of one element into another. It can be done by artificial manner and also occurs naturally. First artificial transmutation was done by Lord Rutherford in 1911. He bombarded alpha particles on Nitrogen-14 to produce Oxygen-17 with protons. The process can be written as:

147N+42He→178O+11H714N+24He→817O+11H

Transmutation of elements results the formation of new elements from some radioactive elements with emission of radiation like alpha, beta or gamma rays. Natural transmutations are spontaneous process and usually occur with unstable radioactive elements. The series of chain reaction results the formation of stable elements like uranium 238 spontaneously transmutes to lead 206 that is a stable element. Unlike natural transmutations, artificial transmutation occurs in nuclear reactors with the bombardment of particles like neutrons. 

There are mainly two types of nuclear reactions: fission and fusion reactions.

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), often producing free neutrons and photons (in the form of gamma rays), and releasing a very large amount of energy.

Fission as encountered in the modern world is usually a deliberately produced man-made nuclear reaction induced by a neutron. It is less commonly encountered as a natural form of spontaneous radioactive decay (not requiring a neutron), occurring especially in very high-mass-number isotopes.

Nuclear fission produces energy for nuclear power and to drive the explosion of nuclear weapons. Both uses are possible because certain substances called nuclear fuels undergo fission when struck by fission neutrons, and in turn emit neutrons when they break apart. This makes possible a self-sustaining nuclear chain reaction that releases energy at a controlled rate in a nuclear reactor or at a very rapid uncontrolled rate in a nuclear weapon.

Nuclear fusion is the process of making a single heavy nucleus (part of an atom) from two lighter nuclei. Fusion happens in the middle of stars, like the Sun. Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion. The energy released by fusion is three to four times greater than the energy released by fission. On Earth, it is very difficult to start nuclear fusion reactions that release more energy than is needed to start the reaction. The only successful approach so far has been in nuclear weapons. The hydrogen bomb uses an atomic (fission) bomb in order to start fusion reactions. Scientists and engineers have been trying to find a safe and working way of controlling and containing fusion reactions that can generate electricity. They still have many challenges to overcome before fusion power can be used as a clean source of energy.