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(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. DHS 157.03(374)(374) “Technique factors” means the following conditions of operation: DHS 157.03(374)(a)(a) For capacitor energy storage equipment, peak tube potential in kV and quantity of charge in mAs. DHS 157.03(374)(b)(b) For field emission equipment rated for pulsed operation, peak tube potential in kV and number of x-ray pulses. DHS 157.03(374)(c)(c) For CT equipment designed for pulsed operation, peak tube potential in kV, scan time in seconds, and either tube current in milliamperes (mA), x-ray pulse width in milliseconds, and the number of x-ray pulses per scan; or the product of tube current, x-ray pulse width, and the number of x-ray pulses per scan expressed as mAs. DHS 157.03(374)(d)(d) For CT x-ray equipment not designed for pulsed operation, peak tube potential in kV, and either tube current in mA and scan time in seconds, or the product of tube current and exposure time in mAs and the scan time when the scan time and exposure time are equivalent. DHS 157.03(374)(e)(e) For all other equipment, peak tube potential in kV and either tube current in mA and exposure time in seconds or the product of tube current and exposure time in mAs. DHS 157.03(374m)(374m) “Telemetric position monitoring system” means a data transfer system that captures information by instrumentation or measuring devices about the location and status of a transport vehicle or package between the departure and destination locations. DHS 157.03(375)(375) “Teletherapy” means a method of radiation therapy in which collimated gamma rays are delivered from a source at a distance from the patient or human research subject. DHS 157.03(376)(376) “Temporary job site” means a location where any of the following occur: DHS 157.03(376)(a)(a) Radiographic operations are performed and sources of radiation may be stored other than at the location or locations of use authorized on the license or registration. DHS 157.03(376)(b)(b) Radioactive materials are present for the purpose of performing well logging or subsurface tracer studies. DHS 157.03(377)(377) “Tenth-value layer” or “TVL” means the thickness of a specified material that attenuates x-radiation or gamma radiation to an extent that the air kerma rate; exposure rate or absorbed dose rate is reduced to one-tenth of the value measured without the material at the same point.