Uranium Fact Sheet Health Physics Society（铀简报保健物理学的社会）.pdf

Fact Sheet Adopted: February 2011 Health Physics Society Specialists in Radiation Safety Uranium Adopted from “A Citizen’s Guide to Uranium” uranium isotope determine its contribution to the radio- by Steven H. Brown, CHP activity of natural uranium. The table below lists the relative mass (weight), half-life, and radioactivity of the What is uranium? three primary isotopes of uranium (U.S. Public Health Uranium is a naturally occurring metallic element that Service 1999). has always been present, since the formation of the earth. Like many other minerals, it has been deposited Uranium Mass, Half-Life, and Radioactivity on land by volcanic action, dissolved by rainfall and, in Isotope % Mass Half-Life (years) % Radioactivity some places, carried into underground formations. U-238 99.3 4.5 billion 48.9 Sometimes chemical conditions resulted in its concentra- U-235 0.72 704 million 2.2 tion into “ore bodies.” It is a fairly common element in Earth’s crust (soil, rock) and in sea and groundwater. U-234 0.005 245,000 48.9 Uranium has exactly 92 protons in its nucleus. It also has approximately 146 neutrons, for a total atomic How much uranium is there in our environment? weight of approximately 238,