DHS 157.03(320)(320) “Sanitary sewerage” means a system of public sewers for carrying off wastewater and refuse, but excluding sewage treatment facilities, septic tanks and leach fields owned or operated by the licensee or registrant. DHS 157.03(321)(321) “Scan” means the complete process of collecting x-ray transmission data for the production of a tomogram. Data may be collected simultaneously during a single scan for the production of one or more tomograms. DHS 157.03(322)(322) “Scan increment” means the amount of relative displacement of the patient with respect to the CT x-ray system between successive scans measured along the direction of such displacement. DHS 157.03(323)(323) “Scan sequence” means a pre-selected set of 2 or more scans performed consecutively under pre-selected CT conditions of operation. DHS 157.03(324)(324) “Scan time” means the period of time between the beginning and end of x-ray transmission data accumulation for a single scan. DHS 157.03(325)(325) “Scattered radiation” means ionizing radiation emitted by interaction of ionizing radiation with matter, the interaction being accompanied by a change in direction of the radiation. DHS 157.03(326)(326) “SCO-I” means a surface contaminated object (SCO) for which all of the following apply: DHS 157.03(326)(a)(a) The non-fixed contamination on the accessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 4 Bq/cm2 (10 -4 microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 0.4 Bq/cm2 (10-5 microcurie/cm2) for all other alpha emitters. DHS 157.03(326)(b)(b) The fixed contamination on the accessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 4x104 Bq/cm2 (1.0 microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 4x103 Bq/cm2 (0.1 microcurie/cm2) for all other alpha emitters. DHS 157.03(326)(c)(c) The non-fixed contamination plus the fixed contamination on the inaccessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 4x104 Bq/cm2 (1.0 microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 4x103 Bq/cm2 (0.1 microcurie/cm2) for all other alpha emitters. DHS 157.03(327)(327) “SCO-II” means a surface contaminated object (SCO) for which the limits for SCO-1 are exceeded and on which all of the following apply: DHS 157.03(327)(a)(a) The non-fixed contamination on the accessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 400 Bq/cm2 (10 -2 microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 40 Bq/cm2 (10 -3 microcurie/cm2) for all other alpha emitters. DHS 157.03(327)(b)(b) The fixed contamination on the accessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 8x105 Bq/cm2 (20 microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 8x104 Bq/cm2 (2 microcurie/cm2) for all other alpha emitters. DHS 157.03(327)(c)(c) The non-fixed contamination plus the fixed contamination on the inaccessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 8x105 Bq/cm2 (20 microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 8x104 Bq/cm2 (2 microcurie/cm2) for all other alpha emitters. DHS 157.03(328)(328) “Sealed source” means any radioactive material that is encased in a capsule designed to prevent leakage or escape of the radioactive material. DHS 157.03(329)(329) “Sealed Source and Device Registry” or “SSDR” means the national registry that contains all the registration certificates, maintained by the NRC that summarize the radiation safety information for the sealed sources and devices and describe the licensing and use conditions approved for the product. DHS 157.03(330)(330) “Secondary dose monitoring system” means a system that will terminate irradiation in the event of failure of the primary dose monitoring system. DHS 157.03(331)(331) “Secondary protective barrier” means the material that attenuates stray radiation. DHS 157.03(331g)(331g) “Security order” means any order that was issued by the NRC that required fingerprints and an FBI criminal history records check for access to any one of the following: DHS 157.03(331g)(c)(c) Risk significant material such as special nuclear material or large quantities of uranium hexafluoride. DHS 157.03(331m)(331m) “Security screening unit” means a non-human use open-beam or cabinet x-ray system with accessible openings designed for the detection of weapons, bombs, or contraband concealed in baggage, mail, packages or other commodities or structure. DHS 157.03(331r)(331r) “Security zone” means any temporary or permanent area established by the licensee for the physical protection of category 1 or category 2 quantities of radioactive material. DHS 157.03(332)(332) “Self-contained breathing apparatus” or “SCBA” means an atmosphere-supplying respirator for which the breathing air source is designed to be carried by the user. 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.