IEEE N42.18-2004 pdf free download – Specification and Performance of On-Site Instrumentation for Continuously Monitoring Radioactivity in Effluents.
4. Factors Influencing Selection of Instrumentation
4.1 Effluent Stream Factors.
4.1.1 fladlologlcal Characteristics of the Effluent Stream.
‘The radiological characteristics of an effluent stream influence system capability requirements. The concentration of each raiionuclide present with its particular hall-life and type (alpha. beta, and pltotorn and the energy of radiation emitted must he considered in the selection of detectors. Alpha and beta radiation may be particularly subject to energy absorption in the detector housing of the eiTluent materials, thus influencing the sensitivity of the system. Alpha and low-energy beta radiation will not be measured at all if there is any appreciable thickness of material between the effluent and the detector. If a detector housing or the wall of the effluent line separate the ellluent from the detector, the absorption of photons and charged particle equilibrium must be considered. In addition, a delay between sampling and measurement may significantly affect the detection capability of the system for radionuclides with short half-lists.
4.1.2 Physical Characteristics of the Effluent.
Physical cltaracterislics of a gaseous or liqukl effluent that may influence system capability include temperature. pressure. humidity, size and tiumber of suspended particles, and flow rate- Since the sensitivity of detection may be related to one or more of these physical characteristics, they must be considered so that the sample characteristics are accurately related to those of the effluent stream.
Tue size and distribution of suspended particles in the effluent will affect the choice and location of the sanspling device and detector It should he recognized that the density or accumulation of collected particles might came self- absorption losses and that the detector could become contaminated.
Effluent flow rate may also gosem the type of-sampling des’ice. particularly for an off-line nsortitoring system. Since nsost monitoring systems directly measure the concentration of radioactivity in an effluent stream, the stream floss rates must he determined accurately to derive the total released activity. And since most monitoring systems measure only a portion of the radioactivity in the effluent streans, a representative sample must he assured.
4.1.3 ChemIcal Characteristics of the Effluent.
‘The major chemical charactcris1ics that may influence system capability include sample plate out. corrosiveness, and combustibility. Plate out can result in differences in the concentrations of radksnuclides in the sample and in the efflueni The corrosiveness of the sample can damage the system components such as the detector, sampler, filter medium, piping and pump. Dansage of any of these could result in a nonrepresentative sample and eventual systens failure. If an effluent contains combustible or highly reactis’e materials, care must lie taken to present conditions that could permit explosion or combustion
4.2 Environmental Factors.
4.2.1 Temperature.
Roth the detector and the electronic portions of an effluent monitoring system may be influenced by tençerattwe variations. The effects may vary from minor calibration shifts to severe degradation of performance and, in sonse instances, permanent damage. When selecting monitoring instrumentation, therefore, it is particularly important to consider the manufacturer’s specifications in light of the anticipated ambient tlsermal operating extremes. Additionally, other heat loads, such as those from nearby instruments a from direct sunlight, must he taken into account.IEEE N42.18 pdf download.