Nuclear Chemistry

The final type of beta decay is known as electron capture and also occurs when the neutron to proton ratio in the nucleus is too small. The nucleus captures an electron which basically turns a proton into a neutron. E.g. beryllium-7.

It is to slow down the neutrons produced in fission, because slow neutrons are much more likely to be captured by a U-235 nucleus, thus continuing the chain reaction.

Hydrogen-3 is also known as tritium. Gaseous tritium source exit signs are 'EXIT' sign boards, used to indicate emergency exit. They are the most widely used exit signs nowadays. Tritium exit signs are better compared to other traditional or hard-wire exit signs, because they do not require electricity. They work on the principle of radio-luminescence.

The alpha particle is a type of ionizing radiation. With its partners the gamma particles and beta particles, alpha particles are one of the most prevalent forms of radiation. An alpha particle is essentially a helium nucleus, which consists of two neutrons and two protons, without electrons, giving it a net positive charge. Due to its relatively high mass, alpha particles are the most destructive form of ionizing radiation.

The uranium decay-series contains several radioactive isotopes.U-238 decays by alpha emission into thorium Th-234. Th-234 decays by 2 alpha & 3 beta emission changes into Ra-220.

In a disease called Polycythemia vera, an excess of red blood cells is produced in the bone marrow. Phosphorus-32 is used to control this excess.

Yttrium-90 is used for treatment of cancer, particularly non-Hodgkin's lymphoma, and its more widespread use is envisaged, including for arthritis treatment. Lu-177 and Y-90 are becoming the main RNT agents.

A new field is Targeted Alpha Therapy (TAT) or alpha radioimmunotherapy, especially for the control of dispersed cancers. The short range of very energetic alpha emissions in tissue means that a large fraction of that radiative energy goes into the targeted cancer cells, once a carrier such as a monoclonal antibody has taken the alpha-emitting radionuclide to exactly the right place. TAT using lead-212 is said to show promise for treating pancreatic, ovarian and melanoma cancers.

The coolant prevents overheating in the reactor from . The coolant liquid carries the unused heat to an outside cooling tower. There is a large cooling tower at Nine Mile 2. Some of the heat is sent to a boiler to generate steam and turn the turbines that generate electricity. Shielding prevents radiation leaks; moderators slow down nuclear reactions; control rods absorb neutrons and halt the reaction.

Half-life depends on time. Factors like temperature, pressure, and volume have no effect. So, with the decrease in tempreture the half-life of a radioactive nuclide will remains the same.

Gamma rays are high-energy photons with a very short wavelength (0.0005 to 0.1 nm). The emission of gamma radiation results from an energy change within the atomic nucleus. Gamma emission changes neither the atomic number nor the atomic mass so it will remain unaffected by the electric field.

Beta particles have a charge of minus 1, and a mass of about 1/2000th of a proton. This means that beta particles are the same as an electron. They are fast and light. Beta particles have a medium penetrating power.

Gamma rays are high-energy photons with a very short wavelength (0.0005 to 0.1 nm). The emission of gamma radiation results from an energy change within the atomic nucleus. Gamma emission changes neither the atomic number nor the atomic mass so, they do not show acceleration in a magnetic field.

Geological dating covers thousands of years. Only isotopes with long half-lives can be used. The isotope with the longest half-life is uranium-238. Uranium-238 can be used to date rocks, fossils and meteorites. Carbon-14 is used to date matter that was once alive.

Only charged particles can have their kinetic energy increased in a particle accelerator. Electric and magnetic fields are used to speed up the particles and these field have no effect on uncharged particles. Neutrons have no charge so a particle accelerator can not increase the kinetic enegy of a neutron.

The coolant is substance in a pipe to the steam generator where water is boiled. This is where heat-exchange process occurs. Heat is absorbed by the coolant that is produced in the reactor. Typical coolants are water, carbon dioxide gas or liquid sodium.

Shielding prevents radiations to reach outside the reactor. Lead blocks and concrete enclosure that is strong enough of several meters thickness are used for shielding.

These rods absorb neutrons and stop the chain reaction to proceed further. These are made up of steel containing a high percentage of material like cadmium or boron which can absorb neutrons. When control rods are completely inserted into the moderator block then all the neutrons is absorbed and reaction comes to halt.   

The coolant material used here is either helium or carbon dioxide which transfers heat to the turbines.

In this reactor, water is used as coolant. The primary cooling water is at very high pressure so it does not boil. It goes through heat exchanger transferring heat to the loop which then spins the turbine.

Narora Atomic Power Station is located in Bulandshahar District in Uttar Pradesh, India. The first reactor was established in 1989 and second in 1991. 350 MW power produced in both the reactors. The plant is situated on the bank of the river Ganga.

The fissionable material used in the reactor is called as fuel. The commonly used fuels are Uranium, Plutonium or Thorium. It can be U-235, U-238, Pu-236 or Th-232. Uranium is mostly preferred as it has high melting point.

The isotopes have the same atomic number (number of protons), the same number of electrons, but a different atomic mass because the number of neutrons is different. U-233 is an isotope of U-235 so, their chemical properties are similar.

Only neutrons of a fairly low speed should be used to have controlled chain reaction. To slow down the speed fast moving neutrons produced during the fission process, moderators are used. Moderator reduces the speed of the neutron by absorbing its energy but not absorb neutron. Graphite, heavy water and beryllium are common moderators.

Considering the historical perspective, Radium was used in self-luminous paints, aircraft switches, clocks, nuclear panels and instrument dials.