Diffusion of radioactive materials in the atmosphere.

Author:Ajlouni, Abdul-Wali
 
FREE EXCERPT

INTRODUCTION

The artificial creation of radionuclides may result from physical processes involving nuclear fission, nuclear fusion and neutron activation. The most important source of artificially created radionuclides is neutron-induced nuclear fission. The chemical and physical forms of the active species determine deposition, migration and uptake are radioactivity by living organisms.

A variety of systems and processes may introduce radioactivity into the environment. Human activities involving nuclear weapons and the nuclear fuel cycle (including mining, milling, fuel enrichment and fabrication, reactor operation, spent fuel storage and reprocessing and waste storage), leading to significant creation and release of radioactivity. Human technology also releases pre-existing natural radionuclides, which would otherwise remain trapped in the earth's crust (1).

The physical and chemical form of radionuclides may vary depending on the release and transport conditions in addition to the element properties. A general distinction can be made between gases, aerosols and particulate material. The most serious dispersion of radioactive materials in the environment is that related to escaping of noble gases, halogens and aerosols of non-volatile radioactive materials, from the reactor containment in the event of a sever reactor accident (1). In this study we try to make a mathematical simulation of radionuclide dispersion in the environment by matching the mathematical tools which are the partial differential equations, mainly the diffusion equation and the technical data of the nuclear reactors. This simulation may help in determination of radiation dose may received by the public during a sever reactor accident. A demonstration, with a computer program, reflecting the Jordanian atmosphere, will be carried out; the results from this demonstration will be compared with real data taken from the field. The study is arranged as follows. First, we introduce the main concepts of the Partial Differential Equations (PDEs) and their applications. Then, we introduce the main features of transport phenomena with emphasis on the diffusion equation and its application in dispersion of radioactive materials as atmospheric pollution. Finally, arithmetic calculations related to Jordan atmosphere is carried out.

MATERIALS AND METHODS

Partial differential equations: A PDE is an equation that contains partial derivatives, in which the unknown function depends on several variables, e.g., temperature depends both on location x and time t. The variables x and t are called independent variables, whereas the unknown variable which we differentiate, e.g., temperature, is called dependent variable (2-4)

Most physical phenomena, whether in the domain of fluid dynamics, electricity, magnetism, mechanics, optics, or heat flow, can be described in general by Partial Differential Equations (PDEs). Simplifications can be made to reduce the equations in question to ordinary differential equations, but, nevertheless, the complete description of the systems resides in the general area of PDEs. Most of the natural laws of physics, such as Maxwell's equations, Newton's laws of motion and Schrodinger equation, are stated, or can be, in terms of PDEs, that is, these laws describe physical phenomena by relating space and time derivatives. Derivatives occur in these equations because the derivatives represent natural things, like velocity, acceleration, force, friction and current. Hence, we have equations relating partial derivatives of some unknown...

To continue reading

FREE SIGN UP