Law of Conservation of Electric Charge<\/a><\/li>\n<\/ul>\nCertain of these laws are obeyed under all circumstances. Others are not. We have accepted the conservation of energy and momentum. In all the examples given, we assume that the number of protons and the number of neutrons is separately conserved. We shall find circumstances and conditions in which this rule is not true. Where we are considering non-relativistic nuclear reactions, it is essentially true. However, where we consider relativistic nuclear energies or those involving weak interactions, we shall find that these principles must be extended.<\/p>\n
Some conservation principles have arisen from theoretical considerations. Others are just empirical relationships. Notwithstanding, any reaction not expressly forbidden by the conservation laws will generally occur, if perhaps at a slow rate. This expectation is based on quantum mechanics. Unless the barrier between the initial and final states is infinitely high, there is always a non-zero probability<\/strong> that a system will make the transition between them.<\/p>\nTo analyze non-relativistic reactions, it is sufficient to note four of the fundamental laws governing these reactions.<\/p>\n
\n- Conservation of nucleons<\/strong>. The total number of nucleons before and after a reaction are the same.<\/li>\n
- Conservation of charge<\/strong>. The sum of the charges on all the particles before and after a reaction are the same.<\/li>\n
- Conservation of momentum<\/strong>. The total momentum of the interacting particles before and after a reaction is the same.<\/li>\n
- Conservation of energy<\/strong>. Energy, including rest mass energy, is conserved in nuclear reactions.<\/li>\n<\/ol>\n
Reference: Lamarsh, John R. Introduction to Nuclear engineering 2nd Edition<\/p>\n
Activity – Specific Activity<\/h2>\n
<\/a>A measure of radioactivity<\/a> (activity) is based on the counting of disintegrations per second<\/strong>. The SI unit of activity<\/strong> is the becquerel<\/strong> (Bq), equal to one reciprocal second. The activity depends only on the number of decays per second, not on the type of decay, the energy of the decay products, or the biological effects of the radiation. It can be used to characterize the rate of emission of ionizing radiation. Specific activity<\/strong> is the activity per quantity of a radionuclide. Thus specific activity is defined as the activity per quantity of atoms of a particular radionuclide. It is usually given in units of Bq\/g, but another commonly used unit of activity is the curie (Ci), allowing the definition of specific activity in Ci\/g.<\/p>\nUnits of activity<\/strong> (the curie and the becquerel) can also be used to characterize an overall quantity of controlled or accidental releases of radioactive atoms<\/strong>.<\/p>\nUnits of Activity<\/strong><\/p>\n