T 2 : :- ... . : .?" . .. . . . . 1. . A : ... 1. SA ** 1. n. 1 . ... . : LA M Wh .. 22:29 1 . . . . -. . . P F .- UNCLASSIFIED . - .. 4 ni " 1. * A s. . 4 . ... VL 1. nh , 1. W . 13 1 . . . 4 ! . s t . 1 ..! ' M . . . . " L A 11 he " 1' 111 . .... . . . W.. . . . ... . 15 y . :1! ; ! . . 1. . . I . .. ..... :) 1: . .' . Y- . Km $. INI 14 . itu.'' NI . .. TIJELO 23 17 . ORNL - . . 1: Se .. :- * 1 . .. . *.17 - > . * Sis: L. . . . . . YE. 406 :4. 1 1' - . . . . . ... . .. . . .. se ..., . . - - - - REPRODUCED FROM BEST AVAILABLE COPY ост .. .. . LEGAL NOTICE - Tuo report ni prepared As no kcount of Corrnancat poa Oind word. Keluher the Valled sures, so be Commolon, nor any person ucun on bell of the Coanluolon: A. Miks my warranty or representation, expressed or implind, nu respect to be accv- racy, completen sı, or wieludcu, of the labor mation contained to to report, or that the nee of any information, apparatus, melhod, or procesu dleclound ta No report may not fairing. prinitely owned rights; or . Anwar, uy liabilities of respect to the use of, or for denyu rosalung from the une ul any informatioa, apparatus, aetud, or proces. dixcloud in We report. A. und in the sbore, "peruo acung od tehall of the Commission" boci deo may A. ployee or contractor of the Commission, or employ of suce contractor, to the extent that lub emplojn of contractor of the Cometsolaa, or employee of auch noalreclor prepares, dienoinates, or prorides acces. l, may Information purnust to dla oployant or contruct o the Coloslon, or als employatni muh sub contractor. . . METALLOGRAPHIC PREPARATION OF DICARBIDES OF THORIUM AND THC RIUM-URANIUM 7h T. M. Kagley, Jr. and B. C. Leslie Metals and Ceramics Division Cok Ridge National Laboratory ABSTRACT Bocouse of the strong tendency of thC2 and (Th, UX, to hydrolyze, special techniques were required to metallographically propare these carbidos. Procedures developed included vibratory polishing inside a dry box and mechanical polishing outside a dry box. Pyrolytic carbon-coated particles and arc cost specimens were prepared using those procedures. Instead of the customary air etching, specimens were otched by immersing 1-5 min in 1:1 HNO-HC. The 1:1 HNO3-Hy solution possivatos the polished surface prowmably by forming a protective film which provents reaction with mols- ture during the period required for microscopic observation and photomicrography. short periods (to 1 min) of immersion in the 1:1 HNO HO solution produced a passivated surface, whilo longor periods (5 to 45 min) erched the dicarbide speci- inens. Polarizod light was particularly affective for observing the winned struc- tures of the dlaarbidos. - - - - - - - - Rosearch sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corporation. INTRODUCTION Ar Oak Ridge National Laboratory, metallography has played an important role in the investigation of coated fuel particles for use in graphite fuel elements for gas-soolad reactors. 2 ,4 This investigation included thorium -uraniun cor- bides in view of their possible application as breeder matarlals. This paper describes the methods developed at ORNL for preparing those carbides metallographically. Since carbides which contain thorium react readily with moisture, special techniques aris nacostory in the metallographic proporation of these carbides. Tech- niquer reportod by others 3,0,' employ mloth covered olishing wheels with the olishing abrasive suspended in a non-aqueous modium. In one instanco, carbide specimens wora preparad in an inert gas atmosphere maintained in a glove box.? In recent years vibratory polishing has been ostablished as an excellent moth- od for preparing samplas metallographically. Vibratory polishing is particularly effective for proporing specimens containing hard and soft constituents such as car- bides and graphite. AI ORNL vibratory pollshiny is used oxtensively, consequantly, o natural development was its extension to the polishing of carbides of uranium and thorium. Indeed, pyrolytic carbon-cooled uranium carbido jarticles have boon vi- bratorliy polished quite sacossfully using aluming abrasive and sillcona oll.' How #var, techniques used for uranium carbide specimens were not wocessful with thorium- containing corbido specimens because these specimens reacted with molsture from the room air surrounding the vibratory pollsher. The procedures developed for preparing these thorium-containing carbide specimens included vibratory pollshing within a dry box and mechanical polishing oustide a dry box. Specimens ware etched und/or pasivated by immersion in a nitric acid-water solution. Specimens prepared Included unsupported pyrolytic- carbon-coated carbicho particles, graphite spheres containing pyrolytie-carbon-coated carbide particles, and arc cost carbida specimens. The compositions of the specimens included thCg, and (Th, UX, with the composition varying from a Th/N ratio of 7 to a U/Th rotio of 9. INITIAL EXPERIENCE At first wo belloved that the procedures for vibratorlly polishing pyrolytic carbon-cooted UC, portiolas wero adequote for handling (Th, UX, particles of 0.6 Th/ ratlo since the first few of these particles had been prepared successfully using these procedures. Later it become apparent that these procedures were not adequato since the specimens sometimes reacted during the vibratory polishing steps. We found that by placing the vibratory polisher in a dry box these (Th, UX, articles could be polished consistently without reaction occurring. Figure I shows hwo coated (Th, UX, particles from the same botch; one particle was prepared with the vibratory pollsher in the room atmosphere, the other particle was prepared with the vibratory polisher in a dry box. In spite of the relatively low thorium content of the (Th,UX, and even though silicone oil was employed as the abrasive vehicle, the (th, UXC, parti- cla vibratorily polished in the room atmosphere has reacted. The other (Th,OX., particle which was vibratorlly polished in a dry box has not reacted. POLISHING PROCEDURES Two different procedures were developed for polishing the specimens, one omploying vibratory polishing inside a dry box and the other mechanical polishing outside outside a dry box. Vibratory polishing has the advantage that a grooter num- ber of specimens can be focossed with loss attention than can be processed by mo- chanical polishing. Also vibratory polishing generally produces a better quality polish thon mechanical polishina; that is, there are fewer scratches and a flatter surface is producod on a vitristorily folishad specimen. Mechanical polishing has the advantage that o single specimen can be repored much faster thon by vibrutory olishing. Also the mechanical polishing procedure does not require a dry box. The preliminary mounting and grinding ste,»s for both procedures were per- formed outside the dry box. Mounting and Crinding The specimons, which were mounted In epoxy resin, * were ground on 320, 400, and 600 grit silicon carbido powers using either silicone all or absoluta athy! alcohol as lubricants. Silicone oll** and ethyl alcohol ware found to be equally satisfactory as lubricants. Vibratory Polishing Proceduro Since vibratory polishing of ThC, and (Th, UX2 requires a dry box, perhaps o description of the dry box employed would be useful. * Araldite epoxy resin manufactured by Cibo Produchs Corporation, Falr- lawn, New Jersey. **Dow-Corning 702 Diffusion Pump Fluid. Dry Box The most desirable box would be a vacuum box which could be evacuatod and filled with an inert gas. Since such a box was not immediately available, a containment box o ft long, 3 ft CANOP ond approximatoly 23 $3 in volume was viod. Figure 2 shows the partlaular dry box arnployed in preparing the specimens. The alr within the box was driod with commercially available silica gel deslocant. * About I lb of silico gel was placed in the box and after the initial drying, replaced at about one to two week Intervals. The silica gel was regenerated for reuso by heat- ing of 150*C. The relative humidity of the air inside the dry box measured about 15%, as compared to a relative humidity of 55-65% for air outside the dry box. Although we would have preferred on air iock arrangement for transferring specimens to and from the cry box, wo were forced to transfer tho specimens through one of the glove parts. During a transfer the rubber gloves covering a part were re- moved for a period as brief as possible so as to minimize contamination of the dry air in the box fran moisture in the room air. Vibratory Polishing The specimens were prepared in the dry box by means of a 12-in, diameter vibratory polisher. Before being placod in the bowl of the polisher, specimens ware capped with stainless steal holders to provide the necessary weight (ou 370 g) for pol- fshing. Specimens were polishad 6-18 hr using a slurry of 10 g of 0.3 alumina and 100 ml of silicone all on a nylon cloth which wos secured at the bottom of the pol- ishing bowl. Further preparation was performed outside the dry box, but to retard reaction with moisture, a film of silicone oil was allowed to remain on the polished wrface, The specimens were first rough polished using a suspension of 0.3 y alumina and obsoluto ethyl alcohol on a variable spoed wheel covered with nylon cloth. The pollshing whool was oparated at low speeds (100-200 rpm) to retain obrasive on the wheel as much as possible. About 3 min woro required for rough polishing. Finol polishing was done using n diamond paste on a variable spood whool again operated at low speed. The wheel used in this step wat osvered with "Tol4aloallica gel manufactured by Davison Chemical Division, W. R. Grace Company., Baltimore, Maryland. Metcloth, * which seemed to leave fewer scratches than nylon cloth. The diamond paste was used without thinner. The final polishing step of about 3 min was nec- ossary in order that graphite contained in some of the carbide specimens would be retained and polishod. ETCHING Before the microstructure can be studied, o means must be ayallable for re- vealing the microstructure in the polished specimens. Investigators,º,' have fre- quently resorted to air olching as a means for revealing the microstructure of ThC, and (Th, UX, of greater than 30 wt % THC(0.43 TY N ratio). Air atching results from the exposure of polished surfaces of the corbidos to moisture contained in the ambient air. Thosa carbides may also be etched by the small amount of residual mois- ture contained in a glove box or even by moisture contained in optical immersion oil. Since moisture from the air reacts continuously with the carbide specimens, the speci- mens must be observed at an early stage before the polished surface has deteriorated. An example of an oir etched specimen is given in Fig. 3, which is a photomicrograph of a pyrolytic carbon-coated (Th, UXC, particle with a Th/ ratio of 2.2. Rather than air etching, we immersed freshly polished specimens in a lil HNO-HD solution. A short period of immersion in this solution placas a passive film on the specimen which prevents reaction with moisture, at least during the per- lod required for visual obsorvation and photomicrography. The HNO3-Hy solution inay also be used to atch the carbide specimens by lengthening the period of immersion. To illustrate the passivating and etching techniques, a pyrolytic carbon-coated (Th,U)C, particio of 2.2 Th/V ratio composition was selected from the same batch as the air etched particle shown in Fig. 3. This carbide particle was first parsivated by immersing 30 sec in lil HNO-Hyo. Figure 4a Illustrates the bright morallic appear- once of the massivated surface. The particle was thon immersed again for 4 min in the some solution, ofter which the article hart the etched appearance as shown with bright field Illumination in Fig. 5a. The longer immersion oprarently thlokaned the film suf- ficiently that interference colors were found which varied with the orientation of the substrate. Figure 5b shows the same etched porticle with polarizod light Illumination. Polarized light illumination particularly accants the twinning which occurs in the Th C2 and (Th,UX, specimens. It should be pointed out, however, that polarized light il- lumination would have shown the twinned structure equally as well had the particle been in the passivated condition shown in Fig. 40. Finally, the spealmon was vibra- tory polished 30 min in the room atmosphere, after which the particle appeared air atched as in Fig. 46. *Nopless cutton cloth from Buehler, Ltd., Chicago, Illinois. An important point should be noted. In order for tho passivating and etching treatments to be effective, the active polished surface should not be exposed directly .no room air. Hence, immediately after polishing the specinions were washed in obso- lute ethyl alcohol to remove any oil and immersed in the nitric acid solution beforo she alcohol evaporated completely from the polished surface. In other words, the pollshod specimen should not be allowed to dry in air before a possive film has been placod on it. After immersion in the nitric acid solution the specimens may be washed with absolute ethyl alcohol and dried with an alr orier. Pasivating with HNO 7-H90 At first, ThC2 specinions were passivated by either swabbing with or immersing in concentratad HNO,. Loter because the concentrated HNCig reacted with the epoxy mounting material, ol.1 HNO ZOH, O solution was chosen for barslvating. A i min Immersion parlod was chosen for passivating the ThC, although a shorter period might hove been sufficient. A 1:1 HNO-Hy solution ond a 1 min Immersion period were also used with (Th, UX, specimens, except that with specimens of 2.2 Th/N ratio or less it was necessary to use a shorter period in order not to etch the specimen. The passivating treatment presumably forms a protective film on the surface which provonds or rotards reaction with moisture. It should be emphasized that this treatment gives only limited protection, although the film gives sufficient protection from moisture for the period of an hour or so required for microscopic observation. Panivated Th Cong specimens containing graphite flakes appeared to be much moro re- active with moisture than passivated specimens containing no graphite. Apparently the graphite flokes disturb the continuity of the film so that it is less protective. Etching with nitric acid solutions, which will be mentioned subsequontly, also passivotes since the film fomed during otching givos the same limited protec- tlon noted for passivated specimens. Since the passivating and etching troatments gave only liniited protoction, specimens after examination were stored in desiccotors. Desiccator storage appeared to be adequate except for graphite-containing specimens of thC, and (Th, UX, of 7 Th/N ratio. Those graphite-containing specimons required a layer of petroleum jolly or silicone graasa to prevent reaction during storage. It might be pointed out that grease soomed to offer better protection than liquids such as silicone oil, kero- wene, ethylene glycol, and ethyl alcohol. Etching with HNOJ-H2O Etching of thorlum and uranium carbidas by immersion in nitric acid solutions depends not so much upon the preferontlal removal of material, such as from grain boundaries or from grains of particular orientations, but rather It depends upon the color contrast developed on the polished surface through the formation of an oxide film. Interference colors iroduced in the oxide film vary directly with the structure of the substrate. With the exception of ThC, and (Th, UX, of 7 Th/U composition, the speci- mens were etched by immersing 5 inin in freshly prepared 1:1 HNO-HO. À freshly prepared solution was used each time since much brighter colors wore obtained with a freshly mixed solution. By lengthening the immersion period to 45 min, Th, and (Th, UXC, of 7 Th/U composition wera etched, although the colors developed were inuch less brilliant than those developed in specimens containing more uranium. As Fig. 6 illustratas, the microstructure of atched Then is revealed much better with polarized light illumination than with bright field Illumination. Polorized light is partioularly offective for revealing the twinned structure of Th C, and (Th, UX, Generally, the brilliance of the colors cieveloped by the HNO 2-Hgo otchant in- creases as the uronium content of the (Th, UX, increases. Etching with HNC2-CH3COOH-H2O Uranium carbides are usually etched by immersing in a solution of aqual parts HINO2(706), CH3COOH (locial), and HyO. Pyrolytic carbon-cuoted (Th, UX2 particles of 0.6 TH/W composition, when etched with this solution, require 5 min Immersion as compared with 20-30 sec for UCg. A passivated surface can be pro- duced with this solution for all compositions of (Th, UXCg, but only specimens with Th/U ratios below I develop sufficient color contrast for observation with bright field Illumination. For the samo poriod of immersion, specimens immorsed in 1:1:1 HNO -CH2COOH-HyO are loss brilliantly colored thon those immersed in 1:1 HNO3-428. RESULTS Specimons which were prepared included wnsupported pyrolytic carbon-coated particles, fueled graphite bodies and arc cast material. To illustrate the results ob- talned, microstructures of sarna of those specimens ore prosented in Figs. 7 to 15. Examples of pyrolytic corbon-coated particles are presented in Figs. 7 to 9. Figuro 9 shows two coated particles which were embodded in a fuoled graphite sphere. Arc cost specimens of both thC, and (Th, UX, were metallographically pro- pered. Microstructures of arc cast Thcg and orc cast (Th,UX, with Thiu ratlos of 711, 3:1, 1:1,103, und 119 are presented in Figs. 10 to 15. The characteristic twinned structure was obsrved in both the ThCig ond (Th, UX, structures. All the arc cast (Th, UXC structuras contained excess graphite. Except for the prosence of excess graphite and small amounts of impurities, all the (Th, UX, compositions exhibited a single phase. As Figs. 6 and 10 show, o complex pattern of twins and cross twins was ob- served in the ThC, microstructure. Such a complex pattern is difficult to explain; it was suggested that at least part of the twinning observed might be due to the ma- tallographic procedure. To eliminato grinding and mechanical polishing effects, the Thcm, was electrolytically polished with a solution of 1:1 glacial acetic acid- Ortho phosphoric acid (70 %) by applying a direct current af 35 v for 1 min. After the Theory was electrolytically polished, the same complox pattern of twins was ob- served. Thus the complex pattern observed in the arc cast The specimen appears to be a true one. The twinning observed in Thon may be related to the transition (occurring at 1415 E 10°C) from the high temperature face-centered cubic form to the low temp- erature monoclinic form which Cavin and Hill reported. CONCLUSIONS 1. Satisfactory methods were doveloped for vibratorily and mechanically polishing dicarbides of thorium and thorium-uranium despite a strong tendency of thaso.carbides to hydrolyze. Specimens were vibratorily polished within a dry knox using 0.3 y alumina abrasive, silicono oll, and nylon cloth. Specimens were me.. chanically polished by rough polishing with a suspension of 0.3 y alumina in athy! alcohol on nylon cloth and final polishing with diamond compound on Metcloth. 2. Instead of the customary air etching, specimons of Th Cg and (Th, UXC, wara passivated and atched by immersion in 1:1 MNO).. Advantagos of this technique over air atching wores a.. Tho microstructures developed by the nitric acid erchant are con- siderably clearer and more definitive than thoso developed by air atching. b. The ThC, and (Th, UX, specimens can be observed in oixen air without the necessity of immersing the specimens under oll to provent re- action with moisturo. 8. Specimens atched or possívated with nitric acid solutions can be examined more deliberately than air atched specimens which must be exom- ined hurriedly because of continued reaction with moisture. ACKNOWLEDGEMENTS The authors wish to thank J. L, Cook, N. A. Hill, and E. S. Bomar of the Ceramics Group, and Mildred Bradley of the Chemical Technology Division for sup- plying the specimens as well as for their encouragenient of this work. We especially wish to thank R. J. Gray, F. L. Corison, Jr., and C. d. Mo- Hargue for their constructive approisol and review of this report. REFERENCES W. C. Harmis, "Coatech Particle fuel Development of the Oak Ridgo National Laboratory, Proceedings of a Symposium Hold at Batello Menorial Institute, November 5, 6, 1962, USAEC Report TID-7654 (1963), pp 72-79. 2. F. L. Corisen, Jr., E. S. Bomar, ons hiew. Harms, Development of fueled Graphite Containing Pyrolytic-Curbon Coated Particles for Nonpurged, Cas- Cooled Roactor Systems, presented at American Nuclear Soclety Mesting in New York, November, 1963, to be published in Nuclear Science and Engi- neering P. E. Reagan, File Carlsen, Jr., and R, Win Carroll, Fission-Gas Relooso frorn Pyrolytic-Carbon-Coated Fuel Particles Curing Irradiation, - Nuclear Science and Engineoring, 18, 301-318 (1964). 6. S. Bomor and R. J. Gray, Thorium-Uranium Carbides for Coated Particle Graphite Fuols,' in Nuclear Motallurgy, vol X, American Institute Mining, Metallurgical, and Petroleum Engineers, New York, 1964. H. A. Wilhelm and P. Chiosti, Thorlun-Carbon Systern, Trans. Am. Soc. Metals, 42, 1295-1310 (1750). A N. Brett, D. Law, and D. T. Livey, Some Investigations on the Uranium- Thorium-Carbon System, J. Inorg. Nucl. Chem., 13, 44-53 (1960). G. B. Engla, Nieto llography of Carbide Fuel Compounds, CA-2067 (March 1961). si ho Long, Jr. and R. J. Gray, Better Metallographic Tochniques... Pol- ishing by Vibration, 'Metal Progress, 74 (4), 145-43 (1958). (10) C.K.H. DuBose and R. J. Gray, Metallography of Pyrolytic Corbon Cooted and Uncoated Uranlum Carbide Spheras, ORNC-TM-91 March, 1962). 10. N. A, Hill and O. 8. Covin, Monoclinio-Cubic Transformation in Thorlum Dicarbide, ORNL-3588 (April 1964). LIST OF MIGURES Y-50949 (a) Y-52589 (b) Flg. 1. Effect of Amosphorie Environment on Vibratory Polishing of (Th, UX, Porticles of 0,6 Th/ Ratio. (a) Portiolo with rocollon, vibratorily polished in room omosphoro, (b) Particle without rocollon, vibratorlly pola Ishad In dry box. 500X, Y-54739 Fig. 2. Glove Box Und for Vibratory Polishing. Y-44075 Y-55256 () Y-55712 (6) Fig. 3. Air Etchod Pyrolytic Carbon-Cooted (Th,UX, Particle of 2.2 Th/ Rotlo. 200 X. Fig. 4. Pyrolytic Carbon-Coated (Th, UX, Porticle of 2.2 THU Ratio. (a) Passivatod by linmersing 30 sec in HNO 7-120. (b) Alr atched during vibro- tcy polishing in room omosphore. 200 X. Y-5528519) Y-55286 (b) Fig. 5. Pyrolytic Carbon-Cooned (Th, UX, Portlalo of 2.2 ThN Ratio. (a) Etched by immersing 5 min in HNO 7-1, 0, bright fleld. (b) Etchod as in (a), polarized light, 200 X. Y-56398 (a) Y-56379 (b) Fig. 6. Arc Cast Thc, Etched by Immorsing 45 min in 1:1 HNC-gatheo. (a) Bright field. (b) Polarizod light. 500 X. Y-53264 (a) Y-53265 (5) Fig. 7, Pyrolytic Carbon-Coated ThC, Particle Pasivated by Immaning 1 min in 1:1 HNO2-H2O. (a) Bright field. (63 Polarizad light. 500 X. Y-55531 (a) Y-55532 (b) Fig. 3. Pyrolytic Corbon-Coated (Th, UX, Porticles of 1.0 THN Ratio, Etched by Imnorsing 5 min in 1:1 HNO 7-,. Bright flold. (b) Polarized light. 250 X. Y-56493 (o) Y-56494 (b) Fig. 9. Pyrolytic Carbon-Coated (Th, UX, Porticles of 0.6 Th/U Ratio Embedded in Fueled Graphite Body. Etched by immersing 5 min in 1:1 HNO ,- H2O. (a) Bright field. (b) Polarized light. 250 X. Y-53542 (a) Y-53543, (15) Fig. 10. Arc Cast ThCn Passivated by Immersing I min in 1:1 HNO- : H2C. (a) Bright field. (b) Polárized light. 1000 X. Y-53154 (a) Y-53155 (6) Fig. 11. Are Cast (Th, UX2 of 7 Th/N Ratio with Excow Graphite, Passivated by Immersing 1 min in 1:1 HNO2-H2O. (a) Bright field. (b) Polar- izod light. 500 X. Fig. 12. Arc Cast (Th, UX, of 3 Th/U Ratio with Excos Graphito, Etched by Immersing 5 min in 1:1 HNOJ-H, O. (a) Bright fleld. (b) Polar- ized light. 500 X. Y-54989 (a) Y-34990 (b) -- or others moes on a.,16**** * ...*.*.*.*... ..**... *** Y-S488. (a) Y-54887 (b) Flo. 13. Aro Cast (Th, UX, of I Th/ Rullo with Exces Graphite, Etched by Immansing 5 min in l.1 HNO 7-H90, (o) Bright fleld. (b) Polor- ized light. 500 X.. Y-54993 (a) Y-54994 lo) Flg. 14. Aro Cast (Th,U)C, of 3 U/Th Ratio with Excos Graphite, Etched by Immersing 5 min in lil HNC, H, O. (a) Bright lleld. (b) Polar- isod light. 500 X, Fig. 15. Arc Cast (Th,UX, of 9 U/Th Ratio with Excos Graphite, Etched by immersing 5 min in lil HNC 7-H, O. (a) Bright llold. (b) Polura izod light. 500 X. Y-86108 (o) Y-56109 (6) CHES N ....-- (a) Y-50949 . I · soox . INCHES 21. I'm Le math - Tons (b) Y-52589 1:: - aisia ai! women xoos Fig. 1. Effect of Atmospheric Environment on Vibratory Polishing of (Th,U)C, Particles of 0.6 Th/U Ratio. (a) Particle with reaction, vibratorily polished in room atmosphere. (b) Particle without reaction, vibratorily polished in dry box. 500 X. به .. . ل ت سمم. . ... . . .م - . - - . د بسس | | سس وا ا ا : سسسسسس سسسمس: : 4 Fig. 2 (Y-54739). Glove Box Used for Vibratory Polishing. L. em 1 , no decisiones Fig. 3 (Y-44075). Air Etched Pyrolytic Carbon-Coated (Yh, U)C, Particle os 2.2 Th/N Ratio. 200 X. . (b)Y-55712 (a)Y-55256 A । . P Fig. 4. tory polishing in room atmosphere. (a) Passivated by immersing 30 sec in HNO3-H20. (b) Air etched during vibra- Pyrolytic Carbon-Coated (Th,U)C, Particle of 2.2 Th/U Ratio. . । . :...१० REVER REEEEEEEEEEEETINES ] .: - - : ... ..- - :- -. -- ... --.- - .- .: . -"- - , -. --- :- -.-. - : -. :: - - - - - - - -',.. ..... .. ... . . . . . . .- । ---- - - - -- -. . . - . . . f . L . . - -76 -.---- . . -2 -:- : . . . . .---'.. : - . . . . . - --- - K - ---- -:---- = - :.-.. - - (6) Y-55285 . ... -..--.- .. ... ... . . बबबबबबबबबबबबबबबबबE SHOMबबबबबबबबबबबब . . . ' . . (b)Y-55286 - .:: .. . ___Fig. 5. Pyrolytic Carbon-Coated (Th,U)C, Particle of 2.2 Th/U Ratio. (a) Etched by immersing 5 min in HNOT-H20, bright field. (b) Etched as in (a), polarized light. 200 X. | .. . .. .. san 3 - 3 - - - . 3 3 1 - (و) ۲ - 56398 3 . .. xos . مس به . . . مرمر "۱۰۰۰۰: 7 . . سنتی به همه ما ۱۱۱ ) INCHES و . . . . . د . (b) 7-56399 ل در . . ... .. . . ... . . , : مر حقہ :۔ مهم ز ا / ، سن۔ .. : a نه ............ 1 . . xoos . . . -- , . . . " . 1 . ا ::: کمتر از وب م : 3 ... کے ل یے ان ن مزید می بالانست. مدت ماند | م نسنسدے۔۔۔ مرد Fig. 6. Arc Cast ThC2 After 45 min Immersion in 1:1 HNO 3-H2). (a) Bright field. (b) Polarized light. 500 X. * : - INCHES ممننعمننضمنخعشسند منشمند TOO T 00" - (a) Y-53264 2 na . 12 3 m . 500x anime materiais i is : ...... INCHES 1 since it .... in (6) Y-53265 Toespraak nimesed i soox .com m i min . ..SI - Fig. 7. Pyrolytic Carbon-Coated Th Cz Particle Passivated by Immersing I min in 1:1 HNO3-H30. (a) Bright field. (b) Polarized light. 500 X. - > . . . . सब का सबब बबबबबब चला बsaharn - बबबबबबxo 52 (a)Y-55531 . . ...... ... ... , . बESHONI ब .... ................ .. . . ... .. : . . . . .. . (b) Y-55532 जब बजाज बबबबबब जका .. ...... ........... ..... ... ... .. ""urren. बबबबब xosब ... . -- .. .... * 2 . .. ......... .. . ...... . Milli- .................- . ------. --- - - - - Fig. 8. Pyrolytic Carbon-Coated (Th,U)C9 Particles of 1.0 Th/URatio, Etched by Immersing 5 min in 1:1 HNO3-H20. (a) Bright field. (b) Polarized light. 250X. - - - P VE S 41. , - ५ .in :... L ...... saHow . M .. (a) Y-56493 • 2...:... । : 1 बबबExose | .......... . .............. .. ......................................... ..... ... ... .. . R. RT . " ::: ... . saloni - . " (b) Y-56494 + . .. , . . .. बबबबबxose | - - . + . . . . . . - ___Fig. 9. Pyrolytic Carbon-Cocted (Th,U)C2 Particles of 0.6 Th/U Ratio Embedded in Fueled Graphite Body. Etched by immersing 5 min in 1:1 HNO3- H20. (a) Bright field. (b) Polarized light. 250X. 14.. INCHES (a) Y-53542 ool 2 و X000 ۔ ۔ ۔ نا ۔ ۔ INCHES ... ..... . ۔ ۔ (b) 7-53543 ۔ . سسسسسسسسسسست : 7 * --- Xo0ot a اسمسم به دین مد.. أما مسمسمعها ص ا ... : Fig. 10. Arc Cast Thc, Passivated by Immersing 1 min in 1:1 HNO2- H2O. (a) Bright field. (b) Polárized light. 1000 X. 1 مه .- . - - - - . . . . - - - - R an e r -* .* . - - . .... -- -. , - - - - ... - - - . - . . .. ... . -.--7- -*- ----- - -* S3HINI * * . -- : - - * . S3HNI * * * ** XOOS 000 INCHES 500 X con AX - * . -T ---- goo í - - - . i. Bilinmasina -, Fig. 11. Arc Cast (Th,U)C, of 7 Th/U Ratio with Excess Graphite, Passivated by Immersing 1 min in 1:1 HNO-H, O. (a) Bright field. (b) Polar- ized light. 500 X. . . . w indows Lined . ii, -... siis sino w ill visam * (a) Y-53154 (6) Y-53155 . , * EXY i 7 * :;* i'. . -.. .-. . ... - - - . .. .. . . . ... . .. .. F - - am INCHES INCHES gol su The 1.00 ..th (a) Y-54989 oos 500 . an como . I '" wono mai mic - decorac . INCHES * Onom L902 00" na.. - شد. ذهنما مهمه ی تسند where come we sawa ...:::::: sexo , (6) Y-54990 - - - en annenin menawani. in permanen dhe sind med m in m na - - - - - - - - -.- .: Fig. 12. Arc Cast (Th,U)C2 of 3 Th/U Ratio with Excess Graphite, Etched by Immersing 5 min in 1:1 HNO-H, O. (a) Bright field. (b) Polar- ized light. 500 X. . :-* . . .- - 2. ** INCHES landi (a) Y-54886 . .... - - - - - - - - M soox SOOX eisie word dan voeren .. mv .iis m com det mest har 1 wonder inte . - ishni (b) Y-54887 . . . . . - - . .. Y .- , - xoos 500x _ . S intime med Fig. 13. Arc Cast (Th,U)C2 of 1 Th/U Ratio with: Excess Graphite, Etched by Immersing 5 min in 1:1 HNO3-H20. (a) Bright field. (b) Polarized light. 500 X. TE:. . sakoni a . . . . . . ".---- . . .. . -- -- D ".com -- - - (a) Y-54993 -- - ... - - wamo - " - www.wore it become soox **.com, O, Corn INCHES (b) Y-54994 . in einem . hoe i , ',,'1',' Danny ! me on! !! ** Fig. 14. Arc Cast (Th,U)C2 of 3 U/Th Ratio with Excess Graphite, Etched by Immersing 5 min in 1:1 HNO3-H2o. (a) Bright field. (b) Polarized light. 500 X. Szom . moms.com.com . . . ...ma mm.2. (a) Y-56108 common 1.00 e - . . . - tops - ! - . e INCHES com via I c I (6) Y-56109 ---cc.... wo... Wemonómetimine xoos monicas do condood communion awards and becomes to Fig. 15. Arc Cast (Th,U)C, of 9 U/Th Ratio with Excess Graphite, Etched by Immersing 5 min in 1:1 HNO2-H20. (a) Bright field. (b) Polar- ized light. 500 X. . S . 3 . a os M AIL !! 49 . DATE FILMED 5/4 165 NY 12 MASA A : : : : . - LEGAL NOTICE - This roport was proporod as an account of Govornmont sponsored work. Noithor the United Statos, nor the Commission, nor any person acting on behalf of the Commissioni A. Makes any warranty or roprosentation, oxprossed or implied, with rospoot to the noou- raoy, completeness, or usefulnous of the information contained in this report, or that tho uso of any information, apparatus, mothod, or proo... disclosed in this roport may not infringo privately owned righto; or B. Assumes any liabilities with roopoot to the use of, or for damages rosulting from the use of any information, apparatus, method, or procesu dioclosed in this report, As used in the abovo, "person aoting on behalf of the Commission" Inoludes any om- ploy.. or contractor of the Commission, or omployee of such contractor, to the extent that suoh omploy.. or contractor of the Commicolon, or employee of such contractor preparos, dinnominates, or provides accomo to, any Information pursuant to his omploymont or contraot with the Commission, or his omployment with such contractor. . - - AY . 1 . . - 2 .27 11 - 27 - -- - W 21 C . . . END De YNI ' AIN KWELI . . . . I. . . . Y ALAL . 1. V AC"