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38 Radiation for Radionuclide Users where punctures are possible. In addition, all sharps should be disposed of in a designated sharps container. Radiation Monitoring In order to ensure that internal and external doses to radiation are kept ALARA , it is essential that: (1) all radioactive materials remain confined to designated storage and work locations; and that (2) radiation levels resulting from the storage and use of these materials are adequately known and controlled. These objectives can only be met through the routine practice of various radiation monitoring activities. Contamination Surveys The undesired or uncontrolled presence of radioactive material on any surface is referred to as “contamination”. Radiation monitoring procedures designed to assess the locations and extent of such contamination are referred to as contamination surveys. Depending upon the types and quantities of radioactive materials in use, contamination surveys may be made directly with portable survey instruments or indirectly by wiping surfaces (approximately 100 cm 2 ) with a filter paper and counting the wipes in a liquid scintillation counting system. Contamination consisting of 3 H, 14 C, or 35 S is best detected through the use of wipes and liquid scintillation counting, since the beta emissions from these radionuclides are not sufficiently energetic to be efficiently detected by portable survey instruments (e.g., 3 H cannot be detected at all by such instruments). The use of wipes may also be appropriate when attempting to detect contamination in areas with higher than background radiation levels. For example, the use of a GM survey meter to detect 32 P contamination on the lip of a hood would not be practical if radiation levels at that point were already elevated from 32 P stored within the hood. When radiation levels in an area are at normal background levels, portable survey instruments can be quite effective in detecting certain types of radioactive contamination. Most GM meters can detect 32 P with efficiencies exceeding 20%. 125 I can be detected at efficiencies nearing 20% with a thin crystal NaI scintillation probe. Dose Rate Surveys In addition to contamination monitoring, it is also important to assess external dose rates resulting from the storage and use of relatively large quantities of high energy beta particles or gamma ray emitters. This information is important in planning and evaluating the control of the factors of time , distance and shielding for the particular situation in order to minimize doses to