DHS 157.03(333)(333) “Shadow tray” means a device attached to the radiation head to support auxiliary beam blocking material. DHS 157.03(334)(334) “Shallow dose equivalent” or “Hs” means the dose equivalent at a tissue depth of 0.007 centimeter (7 mg/cm2). “Shallow dose equivalent” applies to the external exposure of the skin of the whole body or the skin of an extremity. DHS 157.03(335)(335) “SI” means the abbreviation for the International System of Units. DHS 157.03(336)(336) “Shielded position” means the location within the radiographic exposure device, source changer or storage container that, by manufacturer’s design, is the proper location for storage of the sealed source. DHS 157.03(336m)(a)(a) “Shielded room” means a room housing a radiation generating device where, with the device at maximum technique factors, the exterior room environs meets the unrestricted area dose limits of 0.02 mSv (2 mrem) in any one hour and 1 mSv (100 mrem) in a year at 30 cm from the surface of the barrier. DHS 157.03(337)(337) “Shutter” means a device attached to the tube housing assembly which may totally intercept the useful beam and which has a lead equivalency not less than that of the tube housing assembly. DHS 157.03(338)(338) “Sievert” or “Sv” means the SI unit of dose equivalent. The unit of dose equivalent is the joule per kilogram. The special unit of dose equivalent (rem) is being replaced by the sievert. 1 Sv=100 rem. DHS 157.03(339)(339) “Single tomogram system” means a CT x-ray system which obtains x-ray transmission data during a scan to produce a single tomogram. DHS 157.03(340)(340) “Site area emergency” means an event may occur, is in progress, or has occurred that could lead to a significant release of radioactive material and require a response by offsite response organizations to protect people offsite. DHS 157.03(341)(341) “Site boundary” means that line beyond which the land or property is not owned, leased or otherwise controlled by the licensee or registrant. DHS 157.03(342)(342) “Source” means the region and material from which the radiation emanates. DHS 157.03(343)(343) “Source applicator” means a device used to place a radioactive source in a precise anatomical location within the body. DHS 157.03(344)(344) “Source assembly” means an assembly that consists of the sealed source and a connector that attaches the source to the control cable. The source assembly may include a ballstop to secure the source in the shielded position. DHS 157.03(345)(345) “Source changer” means a device designed and used for replacement of sealed sources in radiographic exposure devices and which may also be used for transporting and storing sealed sources. DHS 157.03(346)(346) “Source holder” means a housing or assembly into which a radioactive source is placed to facilitate the handling and use of the source in well logging operations. DHS 157.03(347)(347) “Source-image receptor distance” or “SID” means the distance from the source of radiation to the center of the input surface of the image receptor. DHS 157.03(348)(a)(a) Uranium or thorium, or any combination thereof, in any physical or chemical form. DHS 157.03(348)(b)(b) Ores that contain by weight one-twentieth of one percent or more of uranium, thorium or any combination of uranium and thorium. Source material does not include special nuclear material. DHS 157.03(349)(349) “Special form radioactive material” means radioactive material that satisfies all the following conditions: DHS 157.03(349)(a)(a) It is either a single solid piece or is contained in a sealed capsule that may be opened only by destroying the capsule. DHS 157.03(349)(b)(b) The piece or capsule has at least one dimension not less than 5 millimeters (0.2 in.). 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.