Radiation DetectorsMISCELLANEOUS DETECTORSActivationFoilsandFluxWiresWhenever it is necessary to measure reactor neutron flux profiles, a section of wire or foil isinserted directly into the reactor core. The wire or foil remains in the core for the length of timerequired for activation to the desired level. The cross-section of the flux wire or foil must beknown to obtain an accurate flux profile. After activation, the flux wire or foil is rapidlyremoved from the reactor core and the activity counted.Activated foils can also discriminate energy levels by placing a cover over the foil to filter out(absorb) certain energy level neutrons. Cadmium covers are typically used for this purpose. Thecadmium cover effectively filters out all of the thermal neutrons.PhotographicFilmPhotographic film may be utilized in x-ray work and dosimetry. The film tends to darken whenexposed to radiation. This general darkening of the film is used to determine overall radiationexposure. Neutron scattering produces individual proton recoil tracks. Counting the tracks yieldsthe film’s exposure to fast neutrons. Filters are used to determine the energy and type ofradiation. Some typical filters used are aluminum, copper, cadmium, or lead. These filtersprovide varying amounts of shielding for the attenuation of different energies. By comparing theexposure under the different filters, an approximate spectrum is determined.Rev. 0 Page 53 IC-06
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