抄録
For the purpose of obtaining the knowledge of industrial grain irradiator design, the pilot plant of the new flow rate control type irradiator was made. This report presents the result of a study of the grain flow and the dose distribution in the irradiator.
Structure of irradiator
In this irradiator, grains are irradiated as they pass through annular cylinders and radiation source is located in the center tube. Grains are fed into each annulus by means of vacuum transfer system and reach to the bottom by gravity and pass through the slits of the annulus gate valves. The valves are used to control the flow rate and the dose is dependent on the flow rate in each annulus. The flow rate is controlled by the variation of shutting time of the valves and slit width. (See Fig. 1)
Experimental results
Fluidity:
1. Relative errors of vertical and horizontal components of flow velocity in each Irradiation Field were less than 1.9% and 2.9%, respectively.
2. The flow rate from the valve slits was independent on the curvature of the annular cylinders.
3. The flow rate was directly proportional to the slitwidth. (See (1))
4. There was a turbulence along the flow lane in the flow rate controller and the maximum staying time of rice in this turbulent region equals the time required rices travel a distance of about 20 cm in Irradiation Field. (See Fig. 2)
Dose distribution:
Relative errors of dose distribution in the irradiated rices were less than ±6.0%. (See Table 1)
The values of dose rate in Irradiation Field calculated by the introduced approximate formula agreed well with the data measured by cavity chamber.
(See Fig. 3)
Main merits of this irradiator
1. It is easy to irradiate large size of granules and to vary dosage.
2. The mechanical damage and the blocking troubles of grains at the slits are very little.
3. The dose uniformity in the irradiated grains is quite satisfactory, since the flow rate distribution is uniform in each Irradiation Field.
