COMPARISON OF CESIUM IODIDE AND SODIUM IODIDE FOR UNDERWATER RADIATION DETECTION SYSTEMS
NAVAL RADIOLOGICAL DEFENSE LAB SAN FRANCISCO CA
Pagination or Media Count:
Comparison is made between NaI and CsI scintillation detectors for application to an ultrasensitive underwater detection system. A series of measurements are reported on the response of each crystal to the gamma rays from 40K distributed in water, the attenuation of the integrated count rate by aluminum and steel absorbers surrounding the detector and the background count rate from contaminants on the crystal-phototube assembly and pressure housings. It is assumed in the discussion that NaI crystals will always have to be protected from thermal and mechanical shock by a pressure vessel and that CsI, which is much less susceptible to these types of shock, can be exposed to the hydrostatic pressures in the ocean without damage. The minimum detectable change in 40K concentration is calculated, based on the measured signal and background counts for a CsI crystal and several NaI assemblies with steel and aluminum pressure vessels. It is concluded that, for deep submergence work with detectors of equivalent size, a CsI system is the most sensitive and when compared in terms of a specific detection capability, the least expensive. To complete the evaluation, the assumption that CsI can be operated to all depths without a pressure vessel must be confirmed.
- Chemical, Biological and Radiological Warfare
- Nuclear Instrumentation