Absorption-the action of a body, such as charcoal, in condensing amd holding a gas or soluble substance upon its surface; distinguished from absorption in which the material is taken up within the body by either physical or chemical forces.

Alpha particle-a positively charged nuclear particle consisting of two protons and two neutrons (essentially the nucleus of the helium atom.) Alpha radiation, the stream of alpha particles, is the most densely ionizing but least penetrating type of radiation; alpha particles can be stopped by several sheets of paper. Alphaemitting radionuclides are generally hazardous to humans only if they decay while inside the body. Anthropogenic-originated through human activities. Atom-a basic component of all matter; the atom is the smallest part of an element having all the chemical properties of that element; basically composed of protons and neutrons in the nucleus and electrons in outer orbits. Atomic mass-the mass of any species of an atom, expressed in atomic mass units (equal to 1/12 of the atomic mass of the most abundant carbon isotope, carbon-12). Atomic number-a number characteristic of an element taken to represent the positive charge on the nucleus of an atom of the element normally equal to the number of protons in the nucleus the atomic nunber is equal to the number of electrons outside the nucleus in a neutral atom.

Atomic weight-the relative weight an atom on the basis of carbon-12 defined as 12. For a pure isotope, the atomic weight rounded off to the nearest integer gives the total number of nucleons (neutrons and protons) making up the atomic nucleus.

Becquerel (Bq)-international unit of radioactivity equal to one nuclear disintegration per second.

Beta particle-an electron or positron emitted by the nucleus of an atom during radioactive decay. Beta radiation, a stream of beta particles, is, a more penetrating type of ionizing radiation than is alpha. Beta particles can be stopped by a thin sheet of metal. Most fission products in spent fuel and reprocessed waste (e.g., iodine-131, cesium-137, and strontium-90) are beta emitters. Beta-emitting nuclides are of concern mainly when they decay within the body.

Bioaccumulation-the build-up of radionuclides in living organisms. The chemical similarities between some radionuclides and naturally occurring elements in the human body makes this a potentially dangerous process. (For example, strontium-90 resembles calcium and concentrates in bones). A danger also exists in that marine organisms can bioaccumulate radionuclides and then be consumed by man.)

By-product material—"waste produced by the extraction or concentration of uranium or thorium from any ore processed primarily for its source material content, including discrete surface waste resulting from uranium solution extraction processes; excludes fission products and other radioactive material covered in 10 CFR Part 20.3 (3)". (DOE order 5820.2)

Cesium-137-a radioactive fission product with a 30-year half-life.

Chain reaction-a self-propagated fission of atomic nuclei continued by the further action of one of the products, best exemplified by the fission of a uranium nucleus by a neutron that causes the release of more neutrons that cause further fissions, etc.

Cladding-protective alloy shielding in which fissionable fuel is inserted; is relatively resistant to radiation and the physical and chemical conditions in a reactor core; may be stainless or some alloy such as zircaloy. Cosmic rays-radiation of intense penetrating power, emanating from outer space and consisting mainly of high energy positively charged particles.

Critical pathway approach—evaluation of a series of events through which radioactive material that is introduced into the marine environment is diluted or concentrated, and eventually reaches humans in food or from other contacts.

Curie-a measure of the rate of radioactive decay, equivalent to that of radium, in which exactly 3.7 x 101o disintegrations occur per second.

Decay product-nuclide resulting from the radioactive disintegration of a radionuclide, formed either directly or as the result of successive transformations in a radioactive series; may be radioactive or stable.