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Neutron gaging was applied to the testing for moisture content in bulk powdered foods and in canned Army field rations. The technique is based on the moderation or thermalization of fast neutrons by hydrogenous matter and the measurement of thermal neutron intensity as a function of moisture content. A small californium-252 capsule, of approximate output 107 neutrons per second, was used as the source of fast neutrons.
It is concluded that a fast neutron moderation technique is feasible for the nondestructive measurement or control of moisture or both in near-dry bulk powdered foods. Samples must be measured under identical geometric conditions, that is, uniform bulk density and volume using a standard metal container or cell. For canned or otherwise prepackaged rations, measurement of moisture is interfered with by variations in fill weight among cans or packages of the same product. A gamma-ray attenuation gaging method proved to be of insufficient sensitivity to correct for fill weight variation and was further complicated by nonuniformity in can wall dimensions. Neutron gaging, however, appears to be quite useful for monitoring a standard packaged item for fill weight since the neutron signal is virtually unaffected by variations in container dimensions. The radiation dose imparted to a sample or package of food subjected to such a test is judged to pose no threat to humans from subsequent consumption of the food. An estimate is given for the cost range of a commercial neutron gage and of encapsulated radioisotopic neutron sources.
neutron radiography, nondestructive tests, fast neutrons, moisture content, food analysis, food, californium
Research chemist, Feltman Research Laboratory, Picatinny Arsenal, Dover, N.J.