DHS 157.03(350)(350) “Special nuclear material” means plutonium, uranium 233, uranium enriched in the isotope 233 or in the isotope 235, and any other material which the nuclear regulatory commission determines to be special nuclear material; or any material artificially enriched by any of the foregoing. Special nuclear material does not include source material.

DHS 157.03(351)(351) “Special nuclear material in quantities not sufficient to form a critical mass” means uranium enriched in the isotope U-235 in quantities not exceeding 350 grams of contained U-235; uranium-233 in quantities not exceeding 200 grams; plutonium in quantities not exceeding 200 grams; or any combination of them under the following formula: For each kind of special nuclear material, determine the ratio between the quantity of that special nuclear material and the quantity specified above for the same kind of special nuclear material. The sum of such ratios for all of the kinds of special nuclear material in combination may not exceed one.

DHS 157.03 NoteNote: For example, the following quantities in combination would not exceed the limitation and are within the formula:

DHS 157.03(352)(352) “Special unit” means the alternative system of units for quantifying absorbed dose in rad, dose equivalent in rem and radioactivity in curie.

DHS 157.03(353)(353) “Specific activity” of a radionuclide means the radioactivity of the radionuclide per unit mass of that nuclide. The specific activity of a material in which the radionuclide is essentially uniformly distributed is the radioactivity per unit mass of the material.

DHS 157.03(354)(354) “Specific license” means a license, under requirements prescribed by the department by rule, to possess, use, manufacture, produce, transfer or acquire radioactive material or devices or equipment utilizing radioactive material.

DHS 157.03(355)(355) “Spot film” means a radiograph, which is made during a fluoroscopic examination to permanently record conditions that exist during that fluoroscopic procedure.

DHS 157.03(356)(356) “Spot-film device” means a device intended to transport and position a radiographic image receptor between an x-ray source and fluoroscopic image receptor. It includes a device intended to hold a cassette over the input end of an image intensifier for the purpose of making a radiograph.

DHS 157.03(357)(357) “Stationary beam radiation therapy” means radiation therapy without displacement of one or more mechanical axes relative to the patient during irradiation.

DHS 157.03(358)(358) “Stationary x-ray equipment” means x-ray equipment that is installed in a fixed location.

DHS 157.03(359)(359) “Stereotactic radiosurgery” means the use of external radiation in conjunction with a stereotactic guidance device to deliver a dose to a tissue volume from multiple sources of radiation simultaneously.

DHS 157.03(360)(360) “Stochastic effect” means a health effect that occurs randomly and for which the probability of the effect occurring, rather than its severity, is assumed to be a linear function of dose without threshold. Hereditary effects and cancer incidence are examples of stochastic effects.

DHS 157.03(361)(361) “Storage area” means any secure location, facility or vehicle that is used to store and secure a radiographic exposure device, a radiation machine, a storage container or a sealed source, when it is not in use.

DHS 157.03(362)(362) “Storage container” means a device in which sealed sources or radiation machines are secured and stored.

DHS 157.03(363)(363) “Stray radiation” means the sum of leakage and scattered radiation.

DHS 157.03(364)(364) “Structured educational program” means an educational program designed to impart particular knowledge and practical education through interrelated studies and supervised training.

DHS 157.03(365)(365) “S-tube” means a tube through which the radioactive source travels when inside a radiographic exposure device.

DHS 157.03(366)(366) “Subsurface” means below the surface of the earth.

DHS 157.03(367)(367) “Subsurface tracer study” means the release of a substance tagged with radioactive material to trace the movement or position of the tagged substance in the well-bore or adjacent formation.

DHS 157.03(368)(368) “Supplied-air respirator” or “SAR” means an atmosphere-supplying respirator for which the source of breathing air is not designed to be carried by the user.

DHS 157.03(369)(369) “Surface casing for protecting fresh water aquifers” means a pipe or tube used as a lining in a well to isolate fresh water aquifers from the well.

DHS 157.03(370)(370) “Surface contaminated object” or “SCO” means a solid object that is not itself classed as radioactive material, but which has radioactive material distributed on any of its surfaces.

DHS 157.03(371)(371) “Survey” means an evaluation of the radiological conditions and potential hazards incident to the production, use, transfer, release, disposal or presence of sources of radiation. When appropriate, an evaluation includes tests, physical examinations and measurements of levels of radiation or concentrations of radioactive material present.

DHS 157.03(371m)(371m) “Tailing” means the residual material resulting from the extraction of minerals from the earth.

DHS 157.03(372)(372) “Target” means that part of an x-ray tube or accelerator onto which a beam of accelerated particles is directed to produce ionizing radiation or other particles.

DHS 157.03(373)(373) “Target-skin distance” or “TSD” means the distance measured along the beam axis from the center of the front surface of the x-ray target or electron virtual source to the surface of the irradiated object or patient.