Nuclear Science and IndiaBy Dr. Roman Saini

Nuclear Science

● Nuclear Science is the study of the structure, properties, and interactions of atomic nuclei, which are the hearts of atoms.

● Atoms are the fundamental constituents of everything around us, and we ourselves are composed entirely of them.

● Nuclear science is the study of the atomic world.

● In nuclear science, the word 'nuclear' relates to the nucleus of an atom.

● The nucleus is the place where almost all of the mass of ordinary matter resides.

● Understanding the behavior of nuclear matter under both normal conditions and conditions very far from normal is a major challenge.

● Extreme conditions existed in the early universe, exist now in the cores of stars, and can be created in the laboratory during collisions between nuclei.

● Nuclear scientists investigate by measuring the properties, shapes, and decays of nuclei at rest and in collisions.

● Nuclear science is crucial to understanding our universe, our world, and ourselves at the atomic level.

● If we can understand how atoms come together, interact, and can be best combined with other atoms, then new, more efficient materials and medicines can be developed.

The Evolution of Universe

● The universe was created about 13.7 billion years ago in an event called the Big Bang.

● Around a microsecond after the Big Bang, the universe was populated predominantly by quarks and gluons. As the universe expanded, the temperature dropped.

● Eventually, the universe cooled enough to allow quarks and gluons to condense into nucleons, which subsequently formed hydrogen and helium.

● Interstellar space is still filled with remnants of this primordial hydrogen and helium.

● Eventually, density inhomogeneities allowed gravitational interactions to form great clouds of hydrogen.

● Because the clouds had local inhomogeneities, they gave rise to stars, which collected into galaxies.

● The universe has continued to expand and cool since the Big Bang and has a present temperature of only 2.7 Kelvin (K).

● After the hydrogen and helium created in the Big Bang condensed into stars, nuclear reactions at the cores of massive stars created more massive nuclei up to iron in a series of nuclear reactions.

● Higher-mass nuclei were created at the end of the star’s life in supernovae explosions.

● These elements were scattered into space where they later combined with interstellar gas and produced new stars and their planets.

● Earth and all its occupants, animate and inanimate, are the products of these nuclear astrophysical processes.

● Atoms are called the building blocks of matter.

● They are made of subatomic particles, the most known of which are

1. Protons,

2. Neutrons and

3. Electrons

● The atomic nucleus consists of nucleons—protons and neutrons.

● Protons and neutrons are made of quarks and held together by the strong force generated by gluon exchange between quarks.

Atom

● The proton is found in the nucleus and has a positive electrical charge equal to the negative charge of an electron and a mass similar to that of a neutron: a hydrogen nucleus.

● They have the mass of approximately 1 atomic mass unit (AMU).

● Proton symbol- p or p+1

Proton Number:

● The total number of protons in the nucleus is denoted by Z.

Proton

Neutron

● One of the basic particles that makes up a nucleus.

● It has no charge and is slightly heavier than a proton.

● Neutron symbol - n or n°.

● A neutron and a proton have about the same mass, but a neutron has no electrical charge.

Neutron number:

● The total number of neutrons in the nucleus is denoted by N.

● They are negatively charged particles represented as e-.

● The charge on an electron is equal, but opposite, to the positive charge on a proton.

● The mass of an electron at rest, symbolized me, is approximately 9.11 x 10-31 kilogram (kg).

● Electrons are arranged outside the atomic nucleus in orbits.

Electrons

● The mass of a neutral atom.

● Its value in atomic mass units (u) is approximately equal to the sum of the number of protons and neutrons in the nucleus of the atom.

● An atomic mass unit is defined as precisely 1/12 the mass of an atom of carbon-12.

● The relative atomic masses of all elements have been found with respect to an atom of carbon-12. Hence, the relative atomic mass of the atom of an element is defined as the average mass of the atom, as compared to 1/12th the mass of one carbon-12 atom.

Atomic Mass

Atomic Number:

● It is the number of protons found inside the nucleus of an atom.

● It is represented by the letter Z.

Mass Number or Atomic Mass Number:

● It is the total number of nucleons (protons and neutrons) found in the nucleus of the atom.

● It is represented by the letter A.

● A nucleus is identified by its atomic number Z (i.e., the number of protons), the neutron number N, and the mass number A,

where A = Z+N.

● In addition to its atomic number and mass number, a nucleus is also characterized by its size, shape, binding energy, angular momentum, and (if it is unstable) half-life.

Nuclear Binding energy:

● The energy that free nucleons give up in order to be bound inside a nucleus.

Nucleon:

● A constituent of the nucleus; that is, a proton or a neutron.

Nucleus:

● The core of the atom, where most of its mass and all of its positive charge is concentrated.

● Except for 1H, the nucleus consists of a combination of protons and neutrons.

Neutrino:

● An electrically neutral particle with negligible mass.

● It is produced in processes such as beta decay and reactions that involve the weak force.

Nuclear Reactor:

● A device in which a fission chain reaction can be initiated, maintained, and controlled.

● Its essential components are fissionable fuel, moderator, shielding, control rods, and coolant.

Isobars

● They are the atoms of different elements which have the same mass number (A) but different atomic number (Z).

● Thus, isobars have the same nucleon number.

● Example: Calcium has an atomic number 20 and Argon has an atomic number 18, but both have mass numbers 40.

Isotopes

● The atoms of the same element, having the same atomic number (Z) but different mass numbers (A).

● The isotopes have the same number of protons but different number of neutrons.

● The chemical properties of isotopes are similar but their physical properties are different.

Examples:

● Three isotopes of a hydrogen atom, namely protium, deuterium and tritium - 11H, 21H, 31H respectively.

● Carbon 12 and Carbon 14 are both isotopes of carbon having 6 protons but with 6 neutrons and 8 neutrons respectively.

Carbon-12 is the stable and abundant form of carbon whereas carbon-14 is radioactive.

● Uranium-235 and uranium-238 occur naturally in the Earth's crust.

● Radioisotopes are radioactive isotopes of an element.

● Radioisotopes are the unstable form of an element that emits radiation to transform into a more stable form.

● Radiation is easily traceable and can cause changes in the substance it falls upon. These special attributes make radioisotopes useful in medicine, industry and other areas.

● They can also be defined as atoms that contain an unstable combination of neutrons and protons, or excess energy in their nucleus.

Radioisotopes

● The best known example of a naturally-occurring radioisotope is uranium.

● All but 0.7 per cent of the naturally-occurring uranium is uranium-238; the rest is the less stable, or more radioactive, uranium-235, which has three fewer neutrons in its nucleus.

● The unstable nucleus of a radioisotope can occur naturally, or as a result of artificially altering the atom.

● Stable isotopes are non-radioactive forms of atoms.

● Although they do not emit radiation, their unique properties enable them to be used in a broad variety of applications, including water and soil management, environmental studies, nutrition assessment studies and forensics.

Applications of Radioisotopes

● The applications of radioisotopes in industry are numerous.

● Many types of thickness gauges exploit the fact that gamma rays are attenuated when they pass through a material.

● By measuring the number of gamma rays, the thickness can be determined.

● This process is used in common industrial applications such as:

1. The automobile industry—to test the quality of steel in the manufacture of cars and to obtain the proper thickness of tin and aluminium.

2. The aircraft industry—to check for flaws in jet engines

3. Construction—to gauge the density of road surfaces and subsurfaces

4. Pipeline companies—to test the strength of welds

5. Oil, gas, and mining companies—to map the contours of test wells and mining bores, and

6. Cable manufacturers-to check ski lift cables for cracks.

● In addition, there are manifold uses in agriculture. In plant research, radiation is used to develop new plant types to speed up the process of developing superior agricultural products.

● Insect control is another important application; pest populations are drastically reduced and, in some cases, eliminated by exposing male insects to sterilizing doses of radiation.

● Fertilizer consumption has been reduced through research with radioactive tracers.

● Radiation pellets are used in grain elevators to kill insects and rodents.

● Irradiation prolongs the shelf life of foods by destroying bacteria, viruses, and molds.

● The useful applications of radioisotopes extends to arts and humanities as well.

● Some radioisotopes used in nuclear medicine have short half-lives, which means they decay quickly and are suitable for diagnostic purposes; others with longer half-lives take more time to decay, which makes them suitable for therapeutic purposes.

● Industry uses radioisotopes in a variety of ways to improve productivity and gain information that cannot be obtained in any other way.

● Radioisotopes are commonly used in industrial radiography, which uses a gamma source to conduct stress testing or check the integrity of welds.

● A common example is to test aeroplane jet engine turbines for structural integrity.

● Radioisotopes are also used by industry for gauging (to measure levels of liquid inside containers, for example) or to measure the thickness of materials.

● Radioisotopes are also widely used in scientific research and are employed in a range of applications, from tracing the flow of contaminants in biological systems to determining metabolic processes in small some animals.

Advantages of Neutron

● Neutron activation analysis is extremely useful in identifying the chemical elements present in coins, pottery, and other artifacts from the past.

● A tiny unnoticeable fleck of paint from an art treasure or a microscopic grain of pottery suffices to reveal its chemical makeup.

● Thus the works of famous painters can be “fingerprinted” so as to detect the work of forgers.

● Neutron scattering has proved to be a valuable tool for studying the molecular structure and motion of molecules of interest to manufacturing and life processes.

● Accelerators and reactors produce low-speed neutrons with a wavelength appropriate to “see” structures of the size of magnetic microstructures and DNA molecules.

● Neutrons can penetrate deeply into bulk materials and use their magnetic moment or strong interaction forces to preferentially scatter from magnetic domains or hydrogen atoms in long chain nucleosomes.

● Neutrons are also used in materials surface and interface studies taking advantage of their reflectivity properties.

Radioactivity

● Radioactivity is defined as the property of certain elements to spontaneously emit energy and subatomic particles.

● The term radioactivity was actually coined by Marie Curie, who together with her husband Pierre, began investigating the phenomenon.

● The Curies extracted uranium from the ore and found that the leftover ore showed more activity than the pure uranium.

● They concluded that the ore contained other radioactive elements.● Ernest Rutherford, who did many experiments studying the properties of

radioactive decay, named these alpha, beta, and gamma particles, and classified them by their ability to penetrate matter.

● Atoms are radioactive if the protons and neutrons in the nucleus are configured in an unstable way.

● For low numbers of protons (Z), the number of neutrons (N) required to maintain a stable balance is roughly equal to the number of protons.

● For example, there are 6 protons and 6 neutrons in the nucleus of the most abundant form of carbon.

● For large numbers of protons in the nucleus, the repulsive electric force between protons leads to stable nuclei that favor neutrons over protons.

● A radioactive atom, lacking a proper balance between the number of protons and the number of neutrons, seeks a more stable arrangement through radioactive decay.

● In radioactive processes, particles or electromagnetic radiation are emitted from the nucleus.

● The most common forms of radiation emitted have been traditionally classified as alpha, beta, and gamma radiation.

● Nuclear radiation occurs in other forms, including the emission of protons or neutrons or spontaneous fission of a massive nucleus.

● Of the nuclei found on Earth, majority of them are stable.

● This is so because almost all short-lived radioactive nuclei have decayed during the history of the Earth.

● There are approximately 270 stable isotopes and 50 naturally occurring radioisotopes (radioactive isotopes).

● Thousands of other radioisotopes have been made in the laboratory.

Radioactive Decay

● The binding energy of a nucleus is the energy holding a nucleus together.

● This energy varies from nucleus to nucleus and increases as A increases.

● Because of variations in binding energy, some nuclei are unstable and decay into other ones.

● Hence, atoms with an unstable nucleus regain stability by shedding excess particles and energy in the form of radiation.

● The process of shedding the radiation is called radioactive decay.

● The radioactive decay process for each radioisotope is unique and is measured with a time period called a half-life.

● One half-life is the time it takes for half of the unstable atoms to undergo radioactive decay.

● The rate of decay is related to the mean lifetime of the decaying nucleus.

● In other words, the time required for half of a population of unstable nuclei to decay is called the half-life.

● Half-lives vary from tiny fractions of a second to billions of years.

Alpha (α) Decay● Alpha emission reduces the number of protons by two and also the

number of neutrons in the nucleus by two. ● In an alpha decay, the atomic number changes, so the original (or parent)

atoms and the decay-product (or daughter) atoms are different elements and therefore have different chemical properties.

● In an alpha decay, the nucleus emits a 4He nucleus, an alpha particle. ● Alpha decay occurs most often in a massive nuclei that have too large a

proton to neutron ratio. ● An alpha particle, with its two protons and two neutrons, is a very stable

configuration of particles.

● Alpha decay usually happens in larger, heavier atoms.

● Uranium-238 undergoes alpha decay in an attempt to be stable. It forms Thorium-234 and Helium after disintegration.

● The number of protons in the atom lessens by 2, therefore a new element is formed.

● This process of formation of a new element is called transmutation.

● Because alpha particles carry more electric charge, are more massive, and move slowly compared to beta and gamma particles, they interact much more easily with the matter.

Beta (β) Decay:● Beta decay occurs in a nucleus with too many protons or too many neutrons,

when one of the protons or neutrons is transformed into the other.

● Beta decay can proceed either by the emission of an electron and an antineutrino or by the emission of their antiparticles, a positron and a neutrino.

● In a beta plus decay, a proton decays into a neutron, a positron, and a neutrino.

● In a beta minus decay, a neutron decays into a proton, an electron, and an antineutrino.

● Beta particles are electrons or positrons (electrons with positive electric charge, or anti electrons).

● Beta decay changes the number of protons and the number of neutrons in the nucleus by converting one into the other.

● Inverse beta decay involves the capture of an electron by a nucleus.

● Beta particles are much less massive and move faster, but are still electrically charged.

● This kind of decay occurs when the atom has too many neutrons.

● Iodine 131 undergoes Beta emission.

Three very massive elements are

1. 232Th (14.1 billion year half-life),

2. 235U (700 million year half-life), and

3. 238U (4.5 billion year half-life)

Decay through complex “chains” of alpha and beta decays end at the stable 208Pb, 207Pb, and 206Pb respectively.

● In a gamma decay, a high energy photon leaves the nucleus and allows the nucleus to achieve a more stable, lower energy configuration.

● Spontaneous fission of a large-mass nucleus into smaller-mass products is also a form of radioactivity.

● In gamma decay, a nucleus changes from a higher energy state to a lower energy state through the emission of electromagnetic radiation (photons).

● The number of protons (and neutrons) in the nucleus do not change in this process, so the parent and daughter atoms are the same chemical elements.

Gamma (γ) Decay:

● It does not change the mass or atomic number, only the nucleus changes from a higher-level energy state to a lower level.

● Because gamma rays carry no electric charge, they can penetrate large distances through materials before interacting—several centimeters of lead or a meter of concrete is needed to stop most gamma rays.

Nuclear Energy-Fission and Fusion

● Fission occurs when the nucleus of an atom divides into two smaller nuclei.

● Fission can occur spontaneously; it may also be induced by the capture of a neutron.

● For example, an excited state of uranium (created by neutron capture) can split into smaller “daughter” nuclei.

● Fission products will often emit neutrons because the N/Z ratio is greater at higher Z.

Nuclear Fission

● With a proper arrangement of uranium atoms, it is possible to have the neutrons resulting from the first fission event to be captured and cause more uranium nuclei to fission.

● This “chain reaction” process causes the number of uranium atoms that fission to increase exponentially.

● When the uranium nucleus fissions, it releases a considerable amount of energy.

● This process is carried on in a controlled manner in a nuclear reactor, where control rods capture excess neutrons, preventing them from being captured by other uranium nuclei to induce yet another uranium fission.

● Nuclear reactors are designed so that the release of energy is slow and can be used for practical generation of energy.

● In an atomic bomb, the chain reaction is explosively rapid.

● The isotope 235U, with an abundance of only 0.7% in natural uranium, is commonly used to produce electricity in nuclear fission reactors.

● This isotope has the distinctive and useful property of undergoing nuclear fission through interaction with thermal-energy neutrons (neutrons with average speeds of only a few km/s).

● The other main isotope of uranium, 238U, does not undergo nuclear fission with thermal neutrons, but it does capture neutrons to form the isotope 239Np that then decays to 239Pu.

● This isotope of plutonium undergoes nuclear fission with thermal neutrons with a higher probability than that of 235U.

● The energy released in the fission of 235U and 239Pu, mainly in the form of kinetic energy of the fission fragments, provides the heat to run the turbines that generate electricity in a nuclear fission power plant.

The relevant nuclear reactions can be written as follows:

1. 235U +1n+----------->fission products + neutrons + energy (~200 MeV)

2. 238U +1n------------->239U + gamma rays

3. 239U------------>239Np-------------->239Pu (a series of beta decays).

● A typical pressurized (or boiling) water nuclear reactor consists of a core of fissionable material (enriched to 3.3% to 4% in 235U) in which the chain reaction takes place.)

● The energy released in the fission process, which is primarily in the form of the kinetic energy of the fission fragments, heats the water.

● The water serves both as a neutron moderator (it slows down the fission neutrons to thermal energies) and as a heat transfer fluid.

● Rods of neutron-absorbing material inserted into the core control the chain reaction.

● The thermal energy is removed from the core by water to an external thermal-energy converter.

● In the pressurized water reactor (PWR), thermal energy produces the steam for the turbine through the use of a heat exchanger, whereas in a boiling water reactor (BWR), the steam is produced for direct use in the turbine.

● Nuclear reactors manufacture their own fuel since they produce 239Pu from 238U.

● This 239Pu can be reprocessed from used fuel rods and used to power other reactors.

● It is actually possible to generate more 239Pu than is used up in the reactor by surrounding the core with a uranium blanket and generating 239Pu in this blanket. This is called a breeder reactor.

● A breeder reactor needs to be operated with fast neutrons, and so-called “fast breeder” reactor.

● In a fast-breeder reactor, water cannot be used as a coolant because it would moderate the neutrons.

● The smaller fission cross sections associated with the fast neutrons (as compared with thermal neutrons) leads to higher fuel concentrations in the core and higher power densities, which, in turn, create significant heat transfer problems.

● Liquid sodium metal may be used here as a coolant and heat- transfer fluid.

● Fusion occurs when two nuclei combine together to form a larger nucleus. Fusion of low-Z nuclei can release a considerable amount of energy.

● This is the Sun’s energy source.

● Four hydrogen nuclei (protons) combine in a multistep process to form a helium nucleus.

● More complicated fusion processes are possible; these involve more massive nuclei.

Nuclear Fusion

● Since the energy required to overcome the mutual electric repulsion of the two nuclei is enormous, fusion occurs only under extreme conditions, such as those found in the cores of stars and nuclear particle accelerators.

● To fuse higher-Z nuclei together requires even more extreme conditions, such as those generated in novae and supernovae.

● Because fusion requires extreme conditions, producing this nuclear reaction on Earth is a difficult technical problem.

● It is used in thermonuclear weapons, where the fusion reaction proceeds unchecked.

● Controlled fusion with the release of energy has occurred, but no commercially viable method to generate electrical power has yet been constructed.

● Nuclear fusion reactors, if they can be made to work, promise virtually unlimited power for the indefinite future.

● This is because the fuel, isotopes of hydrogen, is essentially unlimited on Earth.

Nuclear Reactions● Nuclear reactions and nuclear scattering are used to measure the

properties of nuclei.

● Reactions that exchange the energy of nucleons can be used to measure the energies of binding and excitation, quantum numbers of energy levels, and transition rates between levels.

● A particle accelerator which produces a beam of high-velocity charged particles (electrons, protons, alphas, or “heavy ions”), creates these reactions when they strike a target nucleus.

● Nuclear reactions can also be produced in nature by high-velocity particles from cosmic rays, for instance in the upper atmosphere or in space.

● Beams of neutrons can be obtained from nuclear reactors or as secondary products when a charged-particle beam knocks out weakly bound neutrons from a target.

● These fusion reactions occur only at the center of the Sun where the high temperature (~107K) gives the hydrogen and helium isotopes enough kinetic energy to overcome the long-range repulsive Coulomb force and come within the short-range of the attractive strong nuclear force.

● The reaction energy slowly percolates to the surface of the Sun where it is radiated mainly in the visible region of the electromagnetic spectrum

● Only the neutrinos escape from the Sun without losing energy.

Nuclear Weapons

● Nuclear weapons are with us to this day and could be with us in the future.

● Even if all conflicts among nations end, some nuclear weapons might be retained.

● Earth is vulnerable to impacts from comets and asteroids.

● Some scientists have proposed that nuclear weapons could possibly be used to deflect them from hitting our planet.

● Without a doubt, the development of nuclear weapons is one application of nuclear science that has had a significant global influence.

● Following the observation of fission products of uranium by Hahn and Strassmann in 1938, a uranium fission weapon became possible in the eyes of a number of nuclear scientists.

● It was Albert Einstein who signed a letter to Franklin Roosevelt, President of the United States, and alerted him to the potential development of a nuclear weapon.

● In 1945, a bomb using the fission of 235U was dropped on Hiroshima, while a bomb using the fission of 239Pu was dropped on Nagasaki.

● Radiation can be described as energy or particles from a source that travels through space or other mediums.

● Light, heat, and the microwaves and radio waves used for wireless communications are all forms of radiation.

● Radiation includes particles and electromagnetic waves that are emitted by some materials and carry energy.

● The kind of radiation discussed above is called ionising radiation because it can produce charged particles (or ions) in the matter.

Radiation

● X-rays, gamma-rays, alpha particles, beta particles and neutrons are all examples of ionising radiation.

● The sun is a major source of cosmic radiation, or radiation originating from space.

● Airline flights and skiing at high altitudes are activities that will increase exposure to this cosmic radiation.

● Many buildings also emit ionising radiation simply because the materials that were used to build them, such as clay bricks and granite, are naturally radioactive.

● Many forms of “radiation” are encountered in the natural environment and are produced by modern technology.

● Most of them have the potential for both beneficial and harmful effects.

● Even sunlight, the most essential radiation of all, can be harmful in excessive amounts.

● Most of the public attention is given to the category of radiation known as “ionizing radiation.”

Radiation in the Environment

● This radiation can disrupt atoms, creating positive ions and negative electrons, and cause biological harm.

● Ionizing radiation includes x-rays, gamma rays, alpha particles, beta particles, neutrons, and varieties of cosmic rays.

● All ionizing radiations, at sufficiently large exposures, can cause cancer.

● Many, in carefully controlled exposures, are also used for cancer therapy.

● Other effects of radiation, in part inferred from animal experiments, include an increased risk of genetic defects and, for exposures of the fetus before birth, of mental retardation.

● In terms of frequency of occurrence and severity of effects, cancer is the most serious consequence and receives the greatest attention.

● Radioactive waste contains radioactive elements that send out higher levels of radiation than natural background radiation.

● Radioactive waste can be classified into three main categories - low, intermediate and high.

Low-level waste

● Low-level waste emits radiation at levels which generally require minimal shielding during handling, transport and storage.

Radioactive Waste

Intermediate-level waste

● Intermediate-level waste emits higher levels of radiation and requires additional shielding during handling, transport and storage.

High-level waste

● High-level waste has higher levels of radiation which requires increased shielding and isolation from human contact and requires cooling due to its heat-generating capacity.

● It is produced from the operation of nuclear power plants.

● Radioactivity gradually diminishes as the radioactive elements decay into more stable elements, so waste gradually becomes less radioactive and safer to handle over time.

Applications of Nuclear Science

Human Health:

● Nuclear medicine and radiology are the medical techniques that involve the use of radiation or radioactivity to diagnose, treat, and prevent disease.

● About one-third of all procedures used in modern hospitals involve radiation or radioactivity. These procedures are safe, effective, and don't require anaesthetic.

● They are useful in a broad spectrum of medical specialties: from paediatrics to cardiology to psychiatry.

Environment:

● Nuclear science plays a valuable role in helping us understand the history of our environment, how environmental systems function and interact, and the impact that humans are having on the environment.

● Isotopic tracers are also used to study and monitor pollution sources, as well as transport and mixing in the lower atmosphere, in order to improve human health.

Food and Agriculture:

● Nuclear techniques are used in farming and agricultural communities to combat disease and provide other benefits.

● The process of treating food with radiant energy is not new; the sun's energy, for example, has been used for centuries to preserve meat, fruits, vegetables, and fish.

Industrial Application:

● A vast array of industries, from agriculture to manufacturing, use radionuclides to assess materials, products, and processes.

● Just as a medical X-ray allows a doctor to obtain a detailed picture of a bone fracture, an industrial X-ray or gamma-ray examination can provide a foundry worker with a detailed picture of an internal crack in a metal casting.

● Irradiation of a silicon ingot in a reactor accurately changes its semi-conducting properties.

● Bombarding silicon with neutrons for precise periods converts some silicon atoms to phosphorus.

● The computer and electronic industries have a strong demand for this precisely “doped” silicon, whose enhanced properties make it invaluable for use in high-quality electronics, such as those in satellites.

Mining and Minerals:● Radioactive sources are used widely in the mining industry. ● Examples include the non-destructive testing of pipeline blockages and

welds, measuring the density of a material to be drilled through, testing the dynamic characteristics of blast furnaces, measuring combustible volatile matter in coal, and on-stream analysis of a wide range of minerals and fuels.

● Mining companies use radionuclides to locate and quantify mineral deposits, to map geological contours using test wells and mining bores, and to determine the presence of hydrocarbons.

● In milling and flotation operations, instruments using radioactive sources are widespread. These devices have the advantage of providing reliable non-contact measurements.

Archeology:

● A wide range of nuclear techniques are used by archaeologists.

● Historical artefacts can be dated, and their authenticity verified, using nuclear techniques.

Irradiation Services:

● Irradiation is the best method for destroying any residual bacteria in human bones and tendons that are used for transplants and grafting in surgery.

● Irradiation is an alternative to spraying toxic pesticides.

Nuclear Energy:

● Nuclear power is one of the fastest growing energy options for countries seeking energy security and low-emission energy solutions.

In the Home:

● While natural radiation surrounds us every day, scientists have spent decades refining the use of radiation for the benefit of society.

● Radiation produced in nuclear reactors or cyclotrons has many other benefits that are integrated into common consumer and household items.

● Smoke detectors are helping save lives and property.

● Nuclear imaging is a diagnostic technique that uses radioisotopes that emit gamma rays from within the body.

How is nuclear imaging different from other imaging systems?

● There is a significant difference between nuclear imaging and other medical imaging systems such as CT (Computed Tomography), MRI (Magnetic Resonance Imaging) or X-rays.

● The main difference between nuclear imaging and other imaging systems is that, in nuclear imaging, the source of the emitted radiation is within the body.

Nuclear Imaging

● Nuclear imaging shows the position and concentration of the radioisotope.

● If very little of the radioisotope has been taken up, a ‘cold spot’ will show on the screen indicating, perhaps, that blood is not getting through.

● A ‘hot spot’ on the other hand may indicate excess radioactivity uptake in the tissue or organ that may be due to a diseased state, such as an infection or cancer.

● Both bone and soft tissue can be imaged successfully with this system.

How does nuclear imaging work?

● A radiopharmaceutical is given orally, injected or inhaled, and is detected by a gamma camera which is used to create a computer-enhanced image that can be viewed by the physician.

● Nuclear imaging measures the function of a part of the body (by measuring blood flow, distribution or accumulation of the radioisotope), and does not provide highly-resolved anatomical images of body structures.

● Though a CT scan uses radiation, it is not a nuclear imaging technique, because the source of radiation - the X-rays - comes from equipment outside the body (as opposed to a radiopharmaceutical inside the body).

Nuclear Science in India

Department of Atomic Energy (DAE)● The Department of Atomic Energy (DAE) was established on August 3,

1954 under the direct charge of the Prime Minister through a Presidential Order.

● The Secretary to the Government of India in the Department of Atomic Energy is the ex-officio Chairman of the Atomic Energy Commission.

● DAE has been engaged in the development of nuclear power technology, applications of radiation technologies in the fields of agriculture, medicine, industry and basic research.

● DAE comprises five research centers, three industrial organizations, five public sector undertakings and three service organizations.

DAE mandate

● Increasing the share of nuclear power through the deployment of indigenous and other proven technologies and also develops fast breeder reactors and thorium reactors with associated fuel cycle facilities.

● Building and operation of research reactors for production of radioisotopes and carrying out radiation technology applications in the field of medicine, agriculture and industry.

● Developing advanced technologies such as accelerators, lasers etc. and encouraging transfer of technology to industry

● Support to basic research in nuclear energy and related frontiers, areas of science, interaction with universities and academic institutions, support to research and development projects having a bearing on DAE's programmes and international cooperation in related advanced areas of research

● Contribution to national security.

Nuclear Energy Programme Of India

● The idea for India’s nuclear energy programme was conceived by Dr Homi Bhabha almost 4 decades ago, when India’s nuclear technology was nascent and there was a lack of sophisticated infrastructure supporting such technology.

Objectives:

● The Atomic Energy Act of 1948 defines the objective of the atomic energy programme for use of atomic energy solely for peaceful purposes namely the generation of electricity and the development of nuclear applications in research, agriculture, industry, medicine and other areas.

● The achievement of this objective is attributed to the presence of two naturally occurring radioactive elements in India:

○ Natural Uranium whose deposits are estimated to be around 70,000 tonnes.

○ Thorium deposits estimated to be around 3,60,000 tonnes.

Nuclear Power Programme of India

The Nuclear Power Programme of India has following three stages

1. STAGE I- Pressurized Heavy Water Reactor (PHWR)

2. STAGE 2- Fast Breeder Reactor (FBR) Technology

3. STAGE 3- Breeder Reactor (BR) Using U-233 Fuel

Stage 1-Pressurised Heavy Water Reactor● Natural UO2 is used as fuel matrix and Heavy water as moderator and

coolant.● Natural U isotopic composition is 0.7 % fissile U-235 and 99.3% is U-238.● India has achieved complete self- reliance in this technology and this stage

of the programme is in the industrial domain. ● The future plan includes

○ Setting up of VVER type plants based on Russian Technology is under progress to augment power generation.

○ MOX fuel (Mixed oxide) is developed and introduced at Tarapur to conserve fuel and to develop new fuel technology.

Stage 2- Fast Breeder Reactor (FBR) Tech.Main features of FBTR:

● Pu-239 is the main fissile element.

● Blanket of U-238 around fuel core undergoes nuclear transmutation to produce fresh Pu-239 as more and more Pu-239 is consumed.

● Besides a blanket of Th-232 around the core also undergoes neutron capture reactions leading to the formation of U-233.

● U-233 is the nuclear reactor fuel for the third stage of India’s Nuclear Power Programme.

● It is technically feasible to produce sustained energy output of 420 GWe from FBR.

● Setting up Pu-239 fuelled fast Breeder Reactor of 500 MWe power generation is in advanced stage of completion.

● Also, it is proposed to use thorium-based fuel, along with a small feed of plutonium-based fuel in Advanced Heavy Water Reactors (AHWRs) which are expected to shorten the period of reaching the stage of large-scale thorium utilization.

Stage3- Breeder Reactors Using U-233 Fuel

● U-233 is obtained from the nuclear transmutation of Th-232 used as a blanket in the second phase Pu-239 fuelled FBR.

● U-233 fuelled breeder reactors will have a Th-232 blanket around the U-233 reactor core.

● When the reactor is operational, more U-233 will be generated resulting in the production of more and more U-233 fuel from the Th-232 blanket.

● These U-233/Th-232 based breeder reactors are under development.● It is known that Indian thorium reserves an amount of 358,000 GWe per

year of electrical energy, which can meet the energy requirements during the next century and even beyond.

Research Reactors In India

● Research reactors comprise a wide range of different reactor types that are not used for power generation.

● The primary use of research reactors is to provide a neutron source for research and various applications, including education and training.

1. Kamini-(Kalpakkam-Mini):

● It has been established jointly by BARC and I.G.C.A.R. at Kalpakkam and has the capacity of 30kw.

● KAMINI operates from the fuel derived from thorium i.e. U-233 and is the world's 1st reactor to do so.

● It makes use of U- 233 produced by Poornima III.

● Light Water is used as the coolant and moderator.

● KAMINI is part of the third phase of India's nuclear power programme.

2. Dhruva:

● It was established by BARC at Trombay in 1985 and has the capacity of 100 Mw.

● It is the largest research reactor of India.

● It is the primary generator of weapons-grade plutonium-bearing spent fuel for India’s nuclear weapons program

● Some of the isotopes produced by DHRUVA are Indium -192, Iodine -131, dine -125, Molybdenum -90, Chromium -51.

3. Cirrus:

● It was established in 1960 at Trombay by BARC with Canadian assistance.

4. Poornima I:

● It attained criticality on May 18, 1972.

5. Poornima II:

● It is a modified version of Poornima I. It is situated at Trombay and was established by BARC in 1984.

6. Poornima III:

● It was commissioned by BARC at Trombay in 1990. It is the world's first reactor that converts Thorium into U-233.

7. Apsara:

● It was the first reactor to be established in Asia outside the former Soviet Union.

● Its capacity is 1MW.

● It was commissioned in 1956 at Trombay by BARC.

● India's nuclear research programme commenced with the commissioning of APSARA.

8. Zerlina:

● This zero energy reactor was established at Trombay by BARC in 1961.

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