Fabrication of the Fuel Elements

The grooTed side plates are prepared by gang milling sheets of 2S alumi nnm of proper thickness. The inside ends of these side plates are milled to provide proper fit for the end boxes, which are plug brazed into position. Combs milled from Alcoa No. 12 braze-clad aluminum sheet are placed at each end of the fuel assembly to aid in alignment and reinforcement at the center-line. 

Before final assembly, all parts except the fuel plates are carefully cleaned by processing, as follows (1) vapor degreasing, (2) air drying for 1 hr at 30D F, (3) acid dipping (10% HNOj), (4) water rinsing, and (5) air drying as above. The fuel plates are degreased only. 

In final assembly braze strips (silicon-aluminum alloy) are fastened to the edges of the fuel plates by bending over the ends. The brazing strip is then fluxed, and the fuel plate is inserted between the side plates, which are held in a jig. After all plates are inserted and the combs are in place, the jig is closed,to put the side plates into correct position. The whole assembly is then dried and charged into a box type electric furnace for preheating to SOO. C. After being preheated, the assembly is placed in another furnace at llOO C to accomplish final brazing. 

After cooling, the assembly is carefully inspected for spacing, plate curvature, overall dimensions aiid properly brazed joints. If the assembly passes this inspection, the end adapters are inserted, aligned, and plug welded into place ready for final machining. 

The final machining determines the position of the fuel assembly bodies relative to each other in the reactor core according to the bottom and top supporting grids. The sequence of operations is as follows  

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