The tissrrc reaclioii t,o met,allic. aird iioririirt~allic impli~ii1,s i i i h e back rtiriscles of New Zealarid White Rabbits is preseiit,ed. These reac1,ioiis are graded aiid correlated with the t.race metal contained aroiirrd siich implaries. Corielat,ioiis are drawn as to t.he acceptability of various mat,erials for the maiilifactlue of siugical implants. * Suppoited by h'atiorial Institrite of Health Grant ARIIBW aiid repoited to the over 400 were uscd in this phahc of tlie study. 0 1 thopetlic ltesear cii Society, Chicago, Illiiioiz, Jariiiary 1965.135

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A solid-state bonding technique involving the use of gas pressure at elevated temperatures was investigated for the preparation of compartmented Zircaloy-clad flat-plate uranium dioxide fuel elements. 'These investigations involved development of methods for the surface preparation and assembly of fuel-element components for bonding, determination of optimum bonding parameters, development of barrier coatings for uranium dioxide to prevent reaction with Zircaloy, and extensive testing and evaluation of the bonded fuel elements. During the course of this work, the process was continually modified and refined in an effort to improve the quality of the bonded element and decrease the cost of fabrication. The surface-preparation studies indicated that satisfactory bonding could be obtained consistently with both machined and belt-abraded components. Belt abrasion is more economical and was used as the standard technique in the development phases of the program. Initially the elements were assembled into a stainless steel or Ti-Namel envelope which was evacuated and sealed prior to bonding. Later studies showed that the quality of bonded elements could be improved and process costs decreased by edge welding the Zircaloy components to form a gaslight assembly that was then bonded without use of a protective envelope. Further cost reductions were incorporated into the process by the use of piece Zircaloy components to form the picture frame. Optimum bonding with a minimum core-to-cladding reaction was achieved by pressure'bonding at 1500 to 1550 F for 4 hr using a helium gas pressure of 10,000 psi. A postbonding heat treatment for 5 min at 1850 F in a salt bath promoted additional grain growth at the bond interface during the alpha-to-beta transformation. Barrier layers of graphite, chromium, iron, molybdenum, nickel, niobium, palladium, and various oxides were investigated to prevent reaction between the UO2 ''ore and Zircaloy cladding. Graphite, in the form of a sprayed and buffed coating, and chromium were found to be relatively effective barriers. The graphite coating was easy to apply and less expensive than a chromium electroplate. cladding would possibly result in excessive corrosion and bulging or rupture of the compartments. In efforts to overcome this problem, barrier layers were investigated, and several were found to minimize or prevent the reaction between the uranium dioxide and Zircaloy, The program described in this report consisted of a study of pressure-bonding conditions of temperature, time, and pressure, a study of bonding-surface preparation, and a study of core-to-cladding reaction and of barrier layers to prevent the reaction. These basic studies were followed by a process-development study of elements bonded in containers, preliminary studies of bonding edge-welded elements with one-piece picture framies and then piece-component picture frames, and a process-development study of bonding edge-welded elements having piece-component picture frames. MATERIALS Both the reactor-grade Zircaloy-2 and th...