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Nuclear Physics

Nuclear physics

Nuclear physics: Nuclear physics is that part of the physics that deals with the study of the building blocks and interactions of atomic nuclei.

Nucleus: Nucleus is the center of an atom; the nucleus is the positively charged and extremely dense part of an atom. The nucleus is composed of protons and neutrons.

Protons: Protons are positively charged particles.

Neutrons: There is no charge present on the nucleus.

Mass number (A): The mass number is the total of protons and neutrons. The mass number is represented by ‘A’

Atomic number: The total number of protons present in an atom is known as the atomic number. It is represented by ‘Z’

Neutron number: The total number of neutrons present in an atom is known as the neutron number.

Nuclear force:

The nuclear force is defined as the force that binds protons and neutrons inside the nucleus.

Characteristics of nuclear force include:

  • Independent of charge
  • Very short range
  • Much shorter than electric charge
  • The nuclear force favors the formation of pairs of nucleons with the opposite spin.

Nuclear binding energy:

The total mass of separated nucleons is greater than the mass of the nucleus is called the nuclear binding energy.

Binding energy:

The binding energy is that energy which used to break the nucleus apart from its separate constituents.

Binding energy per nucleon:

Nuclei with the largest binding energy per nucleon are more stable.

The largest binding energy per nucleon is 8.7 MeV, for mass number 56.

The nuclei are unstable beyond Bismuth, A=209.

Radioactivity

The nuclei of the naturally occurring elements that are heavy such as U, Th, Ra &b Po are unstable and keep emitting radiation or invisible rays spontaneously and become more stable elements. These elements are known as radioactive elements. The property of emitting such rays is called as the radioactivity of an element.

The nucleus of an atom of an element is disintegrated spontaneously to emit alpha, beta, and gamma rays.

The rays emitted by the radioactive elements are known as radioactive rays.

Radioactivity- The radioactivity is the phenomenon in which the nucleus of an atom of an element undergoes spontaneous and uncontrollable disintegration or decay and emit alpha, beta, and gamma radiations.

OR

Radioactivity is defined as the process of spontaneous disintegration of nuclei of a heavy element by the emission of certain types of radiation.

Ionization: Ionization is the process of addition or removal of an electron to create an ion.

Ionizing Radiation: it is defined as any type of particle or electromagnetic wave that carries enough energy to ionize or remove electrons from an atom. These radiations are of such high materials they can remove electrons. Ionizing radiation is hazardous to health because of this effect.

Non-ionizing radiation: Non-ionizing radiations are those by which we exposed daily in our day to day life. The sources from which we get non-ionizing radiation include:

  • Microwave ovens
  • Global positioning system
  • Cellular telephones
  • Television stations
  • FM & AM Radio
  • Baby monitors
  • Cordless phones
  • Garage door openers
  • Ham radios


There are some other non-ionizing radiations that have extremely low frequency (ELF) wave are mentioned below:

  • The magnetic field of the earth
  • Magnetic field exposure from proximity and transmission lines
  • Electrical appliances and household wiring

Source of radioactive materials:

Naturally occurring radioactive materials

Radioactive materials that occurring naturally and where the human activities increase the exposure of people to ionizing radiation are known by the acronym ‘NORM’.

NORM is the result of activities such as burning coal, making and using fertilizers, oil, and gas production.

Uranium mining exposes those who involved in NORM in the uranium orebody.

Radon in homes is one of the occurrences of NORM which may give rise to concern and action to control it, by ventilation.

All the materials and raw materials contain radionuclides of natural origin.

For the purpose of radiation protection, the most important radionuclides are U-238 & Th-232 in the decay series.

Examples of NORM are the long-lived radioactive elements such as uranium, thorium, and potassium and their decay products, such as radium and radon.

NORM sources:

The list of isotopes that contribute to natural radiation can be distributed into terrestrial (vast majority and the materials come from the ground) and cosmogenic (produces as a result of the interaction of atmospheric gases with the cosmic rays)

The levels of NORM are typically expressed in one of the two ways:

The level of general radioactivity or radioactivity due to a particular isotope is indicated by Becquerels per kilogram (or gram)

The concentration of a specific radioisotope in the material indicated by parts per million (ppm).

Terrestrial NORM

It consists of radioactive materials that are present in the Earth’s crust and mantle, and where the human activities result in increased radiological exposure. The materials can be original such as uranium and thorium or decay products thereof, forming part of a characteristic decay chain series, or potassium-40.

Potassium 40 (K-40) is another major source of terrestrial NORM. The long half-life of K-40 is 1.25 billion years that means it still exists in measurable quantities today. Its beta decays most of the calcium-40 and forms 0.012% of the natural potassium which is otherwise made by stable K-39 & K-41. The potassium is the 7th most abundant element found in Earth’s crust, and K-40 averages 850 Becquerel/kilogram. It is also found in food such as banana and indeed fills a necessary dietary requirement, ending up in the bones.

Cosmogenic NORM

The cosmogenic NORM is produced as a result of interactions between certain gases in Earth’s atmosphere and cosmic rays.  Since most cosmic radiation is absorbed by the Earth’s atmosphere and deflected by Earth’s magnetic field, very little reaches the Earth’s surface and cosmogenic radionuclides contribute more to dose at low altitudes than cosmic rays as such. At higher altitude dose increases due to both which means that the mountain dwellers are frequent flyers are exposed to higher doses as compared to others.

 

Table 1: Radiological characteristics of cosmogenic NORM

Nuclide

decay mode

half life

C-14

β-

5700 y

H-3 (tritium)

β-

12.32 y

Na-22

β+ and electron capture

2.6 y

Be-7

Electron capture

53.22 d

 

Industrial NORM production

Coal energy – combustion and ash: Produced from the burning of coal in coal-fired power plants. This ash contains a number of byproducts that are produced from the burning coal.

Coal mining- Coal mining also gives rise to a potential NORM issue itself. The coal mining is done either in open pits or underground mines. Underground coal mines are liable to increased radon levels, while raised degrees of radium and K-40 can be found in mining waste rocks and soil.

Oil and gas production- Investigation of oil and gas from a wide range of wells has indicated that the enduring uranium and thorium isotopes are not assembled from the stone arrangements that contain them. Anyway Ra-226, Ra-224, Ra-228, and Pb-210 are prepared, and show up for the most part in the water co-delivered during oil and gas extraction.

Metals and smelting- The processes and mining of metal ores, other than uranium, can also generate large quantities of NORM waste.

Mineral sands- Mineral sands contain zircon, rutile, and ilmenite, with xenotime and monazite. These minerals are mined in several countries with a production number of millions of tonnes per year of zirconium and titanium.

Tin production- Tin is a byproduct of mineral and sand production. Slag from smelting tin contains high levels of niobium and tantalum.

Tantalum and niobium- Tantalum can usually occur with the chemically similar niobium. Niobium slags may reach radioactivity levels in excess of 100kBq/Kg.

Rare earth elements- Rare earth materials are chemically similar to uranium and thorium they often found in conjunction with radionuclides.

Uranium production- Despite the fact that not ordinarily considered as NORM, squanders from the front finish of the atomic fuel cycle through to fuel manufacture might be treated as NORM, opening up more choices for removal. Such material incorporates uranium oxides. Radon introduction is additionally an issue in uranium mines.

Phosphor and fertilizer production- Phosphor rocks used for fertilizers can be a major NORM due to both uranium and thorium.

Building materials- Building material may contain elevated levels of radionuclides particularly including Ra-226, Th-232 & k-40. 

Recycling and NORM

Remediation for legacy sites

Radon- Radium-226 is one of the decay products of uranium-238, which is inescapable in many rocks and soils. At the point when this radium decays, it produces Radon-222, inert gas with a half-life of right around 4 days. (Radium-224 is a decay product of thorium, and it decays to radon-220, otherwise called thoron, with a 54-second half-life.) Because radon is so brief, and alpha-decay to various little girl items which are strong and fleeting, there is a high likelihood of its decay when taken in, or when radon little daughter products in dust are taken in. Alpha particles in the lungs are hazardous.