radioactive pollution - yourpedia.in...radioactive pollution is defined as the release of ionizing...

========================================================================

YourPedia

For any query or detail Contact us at: 9855273076, or visit at www.yourpedia.in

1

RADIOACTIVE POLLUTION

Radiation is the emission or transmission of energy in the form

of waves or particles through space or through a material medium. This includes:

Electromagnetic radiation, such as radio waves, microwaves, infrared, visible

light, ultraviolet, x-rays, and gamma radiation (γ)

Particle radiation, such as alpha radiation (α), beta radiation (β), and neutron radiation

Acoustic radiation, such as ultrasound, sound, and seismic waves (dependent on a

physical transmission medium)

Gravitational radiation, radiation that takes the form of gravitational waves, or ripples

in the curvature of space time.

Radioactivity is the emission of ionizing

radiations or particles caused by the spontaneous

disintegration of atomic nuclei. e.g. spontaneous

emission of proton (α-particles), electrons (β-

particles) and gamma rays (short wave

electromagnetic waves) due to disintegration of

atomic nuclei of some elements.

Radioactive Pollution is defined as the release of

ionizing radiations or particles into the

========================================================================

YourPedia


2

environment by human activities which may represent

significant health risk to the living thing and also to the

environment. The human activities that involve

activities with radioactive materials such as mining,

handling and processing of radioactive materials,

handling and storage of radioactive waste, as well as the

use of radioactive reactions to generate energy (nuclear

power plants), nuclear explosions etc.

Types of Radiations

Radiation is often categorized as either ionizing or non-ionizing depending on the energy of

the radiated particles. Ionizing radiation carries more than 10 eV, which is enough

to ionize atoms and molecules, and break chemical bonds.

1. Ionizing radiations

Radiations with sufficiently high energy

can ionize atoms. Ionization is the process by which an

atom or a molecule acquires a negative or positive charge

by gaining or losing electrons, often in conjunction with

other chemical changes. The resulting electrically

charged atom or molecule is called an ion.

Ionizing radiations have high penetration power and

cause breakage of macro molecules. They include X-rays,

cosmic rays and atomic radiations (radiations emitted by

radioactive elements).

Because living cells and, more importantly, the DNA in

those cells can be damaged by this ionization, exposure to ionizing radiation is considered

to increase the risk of cancer.

Most ionizing radiation originates from radioactive materials and space (cosmic rays-

which are generated by stars and certain celestial events such as supernova explosions),

and as such is naturally present in the environment, since most rocks and soil have small

concentrations of radioactive materials.

========================================================================

YourPedia


3

Ionizing radiation has many practical uses in medicine, research and construction, but

presents a health hazard if used improperly. Exposure to radiation causes damage to

living tissue; high doses result in Acute radiation syndrome (ARS), with skin burns, hair

loss, internal organ failure and death, while any dose may result in an increased chance of

cancer and genetic damage;

The molecular damage may produce short range (immediate) of long range (delayed)

effects.

(i) Short range effects include burns, impaired metabolism, dead tissues and death of

the organisms.

(ii) Long range effects are mutations (changing of structure of genes), increased

incidence of tumors and cancer, shortening of life-span and developmental changes.

(iii) The mutated gene can persist in living organisms and may affect their progeny.

========================================================================

YourPedia


4

The actively dividing cells such as Embryo, fetus, cells of skin, intestinal lining, bone

marrow and gamete forming cells are more sensitive to radiations.

Some species of animals and plants preferentially accumulate specific radioactive

materials. For example, oysters deposit 65Zn, fish accumulate 55Fe, and marine animals

selectively deposit 90Sr.

Types of radiation particles:

α-particles

They consist of two protons and two neutrons bound together. Alpha particles

are helium-4 nuclei i.e. Alpha particles are helium nuclei. The best known source of

Alpha particles is Alpha decay of heavier atoms.

Alpha particles don’t travel very fast (compared to beta particles) because they have

such a large mass. Their low speed means that they tend to collide with plenty of other

atoms and cause a lot of ionization on their way. An alpha particle can ionize thousands

of air particles before it slows down. All these collisions mean that they lose energy

quickly, so they have a short range in the air.

Alpha particles can be blocked by a piece of paper and human skin. They interact with

matter strongly due to their charges and combined mass, and at their usual velocities

only penetrate a few centimeters of air, or a few millimeters of low density material

(such as the thin mica). This means that alpha particles from ordinary alpha decay do

not penetrate the outer layers of dead skin cells and cause no damage to the live tissues

below. Some very high energy alpha particles compose about 10% of cosmic rays, and

these are capable of penetrating the body and even thin metal plates. However, they are

of danger only to astronauts, since they are deflected by the Earth's magnetic field and

then stopped by its atmosphere.

========================================================================

YourPedia


5

Alpha radiation is dangerous when alpha-emitting radioisotopes are ingested or

inhaled (breathed or swallowed). This brings the radioisotope close enough to

sensitive live tissue for the alpha radiation to damage cells.

β-particles

A beta particle, also called beta ray or beta radiation, is a high-energy, high-

speed electron or positron emitted by the radioactive decay of an atomic nucleus during

the process of beta decay. There are two forms of beta decay, β− decay and β+ decay,

which produce electrons and positrons respectively.

Beta decay of a neutron transforms it into a proton by the emission of an electron

accompanied by an antineutrino i.e. An unstable atomic nucleus with an excess

of neutrons may undergo β− decay, where a neutron is converted into a proton, an

electron, and an electron antineutrino (the antiparticle of the neutrino). β− decay

========================================================================

YourPedia


6

commonly occurs among the neutron-rich fission byproducts produced in nuclear

reactors.

Or

conversely a proton is converted into a neutron by the emission of a positron (positron

emission) with a neutrino, thus changing the nuclide type i.e. Unstable atomic nuclei with

an excess of protons may undergo β+ decay, also called positron decay, where a proton is

converted into a neutron, a positron, and an electron neutrino.

========================================================================

YourPedia


7

Neither the beta particle nor its associated (anti-) neutrino exist within the nucleus prior to

beta decay, but are created in the decay process. By this process, unstable atoms obtain a

more stable ratio of protons to neutrons.

Of the three common types of radiation given off by radioactive materials, alpha, beta

and gamma, beta has the medium penetrating power and the medium ionizing power.

Being composed of charged particles, beta radiation is more strongly ionizing than

gamma radiation.

Beta particles can penetrate through skin, while can be blocked by some pieces of glass

and metal. Beta particles which are about 100 times more penetrating than alpha particles.

Beta particles can be used to treat health conditions such as eye and bone cancer and are

also used as tracers. Strontium-90 is the material most commonly used to produce beta

particles.

Beta particles are also used in quality control to test the thickness of an item, such

as paper, coming through a system of rollers.

Beta-plus (or positron) decay of a radioactive tracer isotope is the source of the positrons

used in positron emission tomography (PET scan).

========================================================================

YourPedia


8

PET scan machine

γ- Rays or radiations

Gamma (γ) radiation consists of photons with a wavelength less than 3x10−11 meters and are

electromagnetic waves with very high frequencies and energy (greater than 1019 Hz and 41.4

keV). Gamma radiation emission is a nuclear process that occurs to rid an

unstable nucleus of excess energy after most nuclear reactions. Alpha and Beta decay are

almost always accompanied by Gamma Decay. Both alpha and beta particles have an electric

charge and mass, and thus are quite likely to interact with other atoms in their path. Gamma

radiation, however, is composed of photons, which have neither mass nor electric charge

and, as a result, penetrates much further through matter than either alpha or beta radiation.

Gamma rays can penetrate easily to human skin and damage cells on its way through,

reaching far, and can only be blocked by a very thick, strong, massive piece of concrete.

A nucleus which is in an excited state may emit one or more photons (packets of

electromagnetic radiation) of discrete energies. The emission of gamma rays does not alter

the number of protons or neutrons in the nucleus but instead has the effect of moving the

nucleus from a higher to a lower energy state (unstable to stable).

========================================================================

YourPedia


9

Gamma ray emission frequently follows beta decay, alpha decay, and other nuclear decay

processes.

Gamma rays and X-rays are both electromagnetic radiation and they overlap in

the electromagnetic spectrum; the terminology varies between scientific disciplines.

Gamma rays are ionizing radiation and are thus biologically hazardous. Due to their high

penetration power, they can damage bone marrow and internal organs. Unlike alpha and beta

rays, they pass easily through the body and thus pose a formidable radiation

protection challenge, requiring shielding made from dense materials such as lead or concrete.

However, they are less ionizing than alpha or beta particles, which are less penetrating.

Natural sources of gamma rays on Earth include gamma decay from naturally

occurring radioisotopes such as potassium-40, and also as a secondary radiation from various

atmospheric interactions with cosmic ray particles. Some rare terrestrial natural sources that

produce gamma rays that are not of a nuclear origin are lightning strikes and terrestrial

gamma-ray flashes, which produce high energy emissions from natural high-energy voltages.

A large fraction of such astronomical gamma rays are screened by Earth's atmosphere.

Notable artificial sources of gamma rays include fission, such as occurs in nuclear reactors,

as well as high energy physics experiments, such as neutral pion decay and nuclear fusion.

Gamma radiation is often used to kill living organisms, in a process called irradiation.

Applications of this include the sterilization of medical equipment, the removal of decay-

causing bacteria from many foods and the prevention of the sprouting of fruit and vegetables

to maintain freshness and flavor. Despite their cancer-causing properties, gamma rays are

also used to treat some types of cancer, since the rays also kill cancer cells.

========================================================================

YourPedia


10

2. Non-ionizing radiations

Non-ionizing radiation is described as a series of energy waves composed of oscillating

electric and magnetic fields traveling at the speed of light.

The kinetic energy of particles of non-ionizing radiation is too small to produce charged ions

when passing through matter. For non-ionizing electromagnetic radiation, the associated

particles (photons) have only sufficient energy to change the rotational, vibrational or

electronic valence configurations of molecules and atoms. Thus Non-ionizing (or non-

ionising) radiation refers to any type of electromagnetic radiation that does not carry

enough energy per quantum (photon energy) to ionize atoms or molecules. Instead of

producing charged ions when passing through matter, non-ionizing

electromagnetic radiation has sufficient energy only for excitation, the movement of an

electron to a higher energy state.

Near ultraviolet, visible light, infrared, microwave, radio waves, and low-frequency radio

frequency (long wave) are all examples of non-ionizing radiation. By contrast, far ultraviolet

light, X-rays, gamma-rays, and all particle radiation from radioactive decay are ionizing.

========================================================================

YourPedia


11

The region at which radiation becomes considered as "ionizing" is not well defined, since

different molecules and atoms ionize at different energies.

Visible and near ultraviolet electromagnetic radiation may induce photochemical reactions,

or accelerate radical reactions. Near ultraviolet radiation, although technically non-ionizing,

may still excite and cause photochemical reactions in some molecules.

The energy of particles of non-ionizing radiation is low, and instead of producing charged

ions when passing through matter, non-ionizing electromagnetic radiation has only sufficient

energy to change the rotational, vibrational or electronic valence configurations of molecules

and atoms. This produces thermal effects.

Even "non-ionizing" radiation is capable of causing thermal-ionization if it deposits enough

heat to raise temperatures to ionization energies. These reactions occur at far higher energies

than with ionization radiation, which requires only single particles to cause ionization.

The possible non-thermal effects of non-ionizing forms of radiation on living tissue have

only recently been studied. Much of the current debate is about relatively low levels of

exposure to radio frequency (RF) radiation from mobile phones and base stations producing

"non-thermal" effects. Some experiments have suggested that there may be biological effects

========================================================================

YourPedia


12

at non-thermal exposure levels, but the evidence for production of health hazard is

contradictory and unproven.

Non-Ionizing radiation originates from various sources: Natural origin (such as sunlight or

lightning discharges etc.) and man made (seen in wireless communications, industrial,

scientific and medical applications). The NIR spectrum is divided into two main regions:

optical radiations and electromagnetic fields. The optical radiations are centred around

visible light; those with higher energies are termed UV radiation and those with lower

energies IR radiation. Sources of UV radiation are the sun, arc welding, oxy-gas welding,

sun lamps, lasers (UV), sterilization (germicidal) lamps, low pressure gas discharge lamps,

high pressure discharge lamps. Sources of IR radiation are from hot processes such as

steelmaking, glassmaking, welding, and also lasers (IR). Microwaves are used in

telecommunications, radar/satellite links, mobile phones, microwave ovens, TV transmitters.

RF is used in radio communications, visual display units, television sets. Extremely low-

frequency (ELF) electric and magnetic fields (EMFs) surround electrical machinery, home

appliances, electric wiring, and high-voltage electrical transmission lines and transformers.

Non-ionizing radiations affect only those components which absorb them and have low

penetrability.

radioactive pollution - yourpedia.in...radioactive pollution is defined as the release of ionizing...

Documents