Source holder

The process is carried out in an air-tight chamber—originally a simple bell jar and now normally in commercial production purpose-built plant some metres in diameter and length. The chamber is fitted with the necessary pumping system, work holder, source holder, power supply, control equipment, and gauges. It is possible for an experienced operator to control the process with the precision necessary but for routine production to a specified standard automatic control is regarded as essential. 

Fig. 1.27. Schematics of the PACIS with flow tube reactor attached to the source nozzle, (a) magnetic valve for buffer gas (He), (b) Macor insulator, (c) electrodes (the cluster material is contained in the cathode), (d) cooling coil, (e) nozzle, (f) source holder, (g) flow tube reactor, (h) reaction gas inlet, (i) pumping chaimels...

Figure 5.2S A gas-flow counter with removable thin window and movable source holder.

Figure 4.3. Californium-252 source holder used at Gulf Research and Development Company.

Another important aspect of the holder is its cleanliness. Sometimes the pipette solutions can dirty the holder, forming a thin film of salt in its internal surface, which consists in an important noise source. Holders have to be soaked with methanol and dried with dry clean air or nitrogen before use, and each time that a contamination with salt solutions is suspected. 

Insert the radioactive standard under the counter tube. Use shelf number two of a source holder for U3O8 and shelf number one for other weaker sources. 

The core plate consists of a circular plate with round openings. The core plate provides horizontal support and guidance for the control rod guide tubes, incore flux monitor tubes, peripheral fuel supports, and startup neutron source holders. The last two items are also supported vertically by the core plate. The entire assembly is bolted to a support ledge in the core shroud. The core plate also forms a portion within the core shroud, which causes the recirculation flow to pass into the orificed fuel support and through the fuel assemblies. 

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