Bevel-helical gearboxes B4 ns for operation Shaft seals Radial shaft seal Ta B4-HV-8-A

Flender/Flender Gear Units/Bevel-helical gearboxes B4

to the product. The intensity of radioactive source is measured in number of disintegrations per second; the unit of intensity is the curie, whichrepresents 3.7 /H1 1disintegrations per second. The radioactive source is different from conventional energy sources in that it is continuously emitting radiation. As it does, it decays, in the process of radioactive decay.The radioactive decay is assumed to follow rst-order kinetics, hence, changes in intensity with respect to time can be represented by /H1I 0exp (/H1dt) where Iis the intestity at time ,I0is the initial intensity, and dis the radioactive decay constant. Another term that is frequently used with respect to radioactive decay is half-life () of the radioactive isotope, which is dened as the time interval in which the intensity of radioactive source is reduced by one-half. It can be shown that /H1.6/ . Half-life of cobalt 6 is 5.2 years, of cesium 1, 3.2 years, and of radium, 1 years. 2.3.2 Dose The treatment received by the food product is characterized by the radiation dose, the quantity of energy absorbed by the food while it is exposed to the radiation eld. The 6 Lacroix et al. international unit of measurement is the gray (Gy); 1 Gy represents 1 of energy absorbed per kilogram of irradiated product. One gray is equivalent to 1 rad. The desired doseis achieved by the time of exposition and by the location of the product relative to thesource. The amount of energy absorbed by the food also depends on the mass, bulk density,and thickness of the food. For each kind of food, specic dose has to be delivered to achieve desired result. If the dose is less than appropriate, the intended preservation effect may not be achieved. If the dose is excessive, the food may be damaged and unac-ceptable for consumption. In 1, an international expert committee (Food AgricultureOrganization [FAO], International Atomic Energy Agency [IAEA], and the World HealthOrganization [WHO]) concluded, on the basis of the data avail