ORNL-TM-2978 Contract No. W-7405-eng-26 METALS AND CERAMICS DIVISION COMPATIBILITY OF FUSED SODIUM FLUOROBORATES AND BF; GAS WITH HASTELLOY N ALLOYS J. W. Koger and A. P. Litman JUNE 1970 LEGAL NOTICE This report was prepared as an account of Guvernment aponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representation, expressed or implied, with reapect to the accu- racy, completeness, or uaefulnesa of the information contained in this report, or that the use of any information, spparatus, method, or process discloged in this repor! may oot infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resuiting from the use of any information, apparatus, method, or process disciosed in this report. Ag used in the above, ‘‘person acting on behalf of the Commisgaton” includes any em- ployee or contractor of the Comwlission, or employee of such contractor, to the extent that such employee or contracter of the Commission, or employee of such contractor prepares, disseminates, or provides access to, any {nformation pursuant to his employment or contract with the Commigsion, or his employment with such contractor. OAK RIDGE NATIONAL LABORATORY Oak Ridge, Tennessee operated by UNION CARBITE CORPORATION for the U.3. ATOMIC ENERGY COMMISSION SEITHINIRION OF THIS DO 700 [T UNLIMITED ¥ 5 \ i iii CONTENTS Abstract . Introduction . Experimental Methods and Materials . Results .o Effect of Salt Composition and BF; Pressure (Series I) Weight Changes . Salt Chemistry . Specimen Chemistry . Metallography Effect of Temperature (Series II) . Interpretation of Corrosion Rates Conclusions Acknowledgment . Page Qo ~1 ~1 ~1 WM 10 1l 13 14 16 17 COMPATIBILITY WITH FUSED SODIUM FLUOROBORATES AND BF; GAS OF HASTELLOY N ALLOYS J. W. Koger and A. P. Litmanl ABSTRACT Corrosion by NaBF,-NaF mixtures (4—8 mole ¢ NaF) low in oxygen and water was studied with 680C0-hr static tests at 605°C in standard Hastelloy N capsules with titanium-modified Hastelloy N specimens. Boron trifluoride gas was added to overpressures up to 400 psig. Specimens in the molten salts and at the interface showed both weight gains and losses. The gains decreased with increasing NaBF, content, and losses up to 0.03 mg/em? (< 0.0l mil/year) were observed for specimens in 4 mole ¢ NaF. Weight changes of specimens in vapor were very small and independent of overpressure. The main reaction was the oxidation of chromium in the alloy by iron fluoride in the salt to form Na;CrF, and deposit iron on both specimens and capsule. Metallographic examination showed only minor attack and no difference in the two Hastelloy N alloys. The rate of chromium depletion at 605°C was consistent with the rate of solid-state diffusion of chromium to the alloy surface. Additional tests from 538 to 760°C showed Arrhenius behavior that confirmed this mechanism, Fluoroborate salt mixtures were found compatible with Hastelloy N alloys under the conditions of these experiments, and comparison with other experiments showed that increases in water and oxygen content increased the chromium uptake and corrosion. INTRODUCTION The successful use of molten fluoride salts in a reactor system, as demonstrated by the Molten Salt Reactor Experiment (MSRE) at the Qak Ridge National Laboratory, has led to development studies for a Molten Salt Breeder Reactor (MSBR). One of the most promising features of molten salts has been the low corrosion rates experienced with materials of construction, principally nickel-base alloys. INow with AEC Division of Space Nuclear Systems, Washington, D.C. Theory and experiment?® have shown that the corrosion resistance of metals to molten fluoride salts varies directly with the "nobility" of the metal; that is, the resistance to attack varies inversely with the magnitude of the free energy of formation of the fluorides of metals in the container material, Therefore, the container alloy for the fluoride salt must have only a small percentage of constituents that are easily oxidized by the components of the salt. Considering these facts and utilizing information gained in corrosion testing of commercial alloys, ORNL developed® a high-strength nickel-base alloy, Hastelloy N, containing 174, Mo, 7% Cr, and 59 Fe, for use in the MSRE. These early experiments, as well as many recent corrosion tests* ™ ® in LiF-BeF,-ThF,, LiF-BeF,-UF,, and LiF-BeF,-UF,~ThF,, have shown that Hastelloy N is very resistant to attack and corrosion rates are below 0.1 mil/year. Recently the selection of a fluoride salt that can be used as a coolant to transfer heat from the fuel salt to a steam power conversion system has been seriously considered. Cost and melting point considera- tions favor the sodium fluoroborate mixture, NaBF,—8 mole ¢ NaF. However, little information exists on corrosion by fluoroborates., Initial corro- sion results were obtained from an impure fluorcborate salt (high in oxygen and water) in thermal convection loop tests,’ but these results were not considered indicative of behavior with purer salt. Since that time, new methods of preparation have greatly increased the purity of available salt with respect to oxygen and water. ¢J. H. DeVan and R. B. Evans III, Corrosion Behavior of Reactor Materials in Fluoride Salt Mixtures, ORNL-TM-328 (Sept. 19, 1962). *W. D. Manly, J. H. Coobs, J. H. DeVan, D. A. Douglas, H. Inouye, P. Patriarca, T. K. Roche, and J. L. Scott, "Metallurgical Problems in Molten Fluoride Systems," Progr. Nucl. Energy Ser. IV 2, 164-179 (1960). “J. W. Koger and A. P. Litman, MSR Program Semiann. Progr. Rept. Feb. 29, 1968, ORNL-4254, pp. 218-221. °J. W. Koger and A. P. Litman, MSR Program Semiann. Progr. Rept. Aug. 31, 1968, ORNL-4344, pp. 257-264. ®J. W. Koger and A. P. Litman, MSR Program Semiann. Progr. Rept. Feb. 28, 1969, ORNL-4396, pp. R43-246. 7J. W. Koger and A. P. Litman, Compatibility of Hastelloy N and Croloy 9M with NaBF,-NaF-KBF, (90-4-C mole ¢,) Fluoroborate Salt, ORNL-TM-2490 (April 19€9). The overall objective of this study was to determine the corrosion characteristics of pure (low oxygen and water) NaBF,-NaF mixtures under isothermal conditions. Of particular concern was the temperature- dependent dissociation of the salt into liquid NaF and BF, gas. Thus, we first determined the effects of varying the concentration of our salt mixture and the BF; pressure over it in 6800-hr tests at 605°C. 1In a later series of experiments we determined the rate of chromium uptake by NaBF,—8 mole ¢ NaF between 538 and 760°C in 1200-hr tests. EXPERIMENTAIL METHOD AND MATERIALS The capsule design used in studying the effect of salt composition and BF; overpressure (Series I) is pictured in Fig. 1. Each capsule con- tained three specimens of titanium-modified Hastelloy N, one located in the vapor space, one in the salt, and one at the liquid-vapor interface, The capsule was constructed of commercial Hastelloy N and was 2 in. in diameter X 6 in. high. The titanium-modified alloy is considered because of its superior radiation-resistant properties. PHOTC 76207A AS AND FILL LINES BAS AN DRAIN TANK CAPSULE SPECIMENS Fig. 1, Hastelloy N Capsule Assembly for Studying Effects of Salt Composition and BF; Overpressure. The capsule used in studying the effect of temperature (Series II) was basically the same. However, the test specimens were commercial Hastelloy N in the form of 0,030-in.-thick strips to provide more surface area., FEach capsule was 2 in. in diameter X 8.5 in. high and contained 16 specimens. The capsule 1s pictured in Fig. 2, and the test specimens are shown in Fig. 3. Table 1 lists the compositions of the alloys used for the capsules and specimens. PHOTO 76436A 5 F TANK ______ ‘,i:".".°fl " HASTELLOY N - PLATES ' ) 7 5*?“ A ‘ Fig. 3. Standard Hastelloy N Specimens Made to Provide Maximum Surface Area for Study of Temperature Effects. (a) End view. (b) Side view. ' - ’ ' : - | Table 1. Composition of Hastelloy N o a sgiizs Component Composition (wt ¢) Mo Cr e Si Mn Ti I Capsules - 15.8 7.4 2.4 0.2 0.3 0.02 Specimens 12.0 7.3 < 0.1 <0.,01 0.14 0.5 IT Capsules and 17.0 7.2 4.3 0.45 0.5 0.02 Specimens aBalance nickel. The salt for these tests was processed by the Fluoride Frocessing Group of the Reactor Chemisfry Division. The very pure (> 99.94) starting materials were evacuated to about 380 torr, heated to 150°C in a vessel lined with nickel, and then held for about 15 hr under these conditions. After the rise in vapor pressure was observed to be not excessive (indi- cating no volatile impurities), the salt was heated to 500°C while still under vacuum and agitated by bubbling helium through the capsule for a few hours. The salt was then transferred to the fill vessel and forced into the capsules with helium pressure. Salt chemistry 1s discussed under "Results" in this report. A1l capsules were heated in vertical muffle furnaces (Fig. 4) and monitored with Chromel-P vs Alumel thermocouples, which had been spot welded to the capsule and covered with shim stock. In our first series of tests all capsules were operated at 605°C, close to the maximum tem- perature proposed for the coolant salt in the MSBR. Capsule 1 of this series contained a helium overpressure of 4 psig and no added BFj. Capsules 2, 3, and 4 contained BF; corresponding to overpressures of 50, 100, and 400 psig, respectively. Initially the added BF, dissolved in the molten salt or combined with the NaF, but after a few minutes the pressure in the capsule gradually increased. However, when the capsules had been pressurized to the operating pressures, no changes in BF; con- tent were necessary during the test. The compositions of the salts calculated from amounts of BF; added are shown in Table Z. Photo 76727 Furnace Assembly 4. Fig. Table 2. Effect of Salt Composition and BF; Overpressure on Weight Changes of Hastelloy N Salt . 5 BF, Composition Weight Change (mg/cm?) Capsule Overpressure (mole ) (psig) _(mole %) Vapor Interface Liquid NaBF, NaF 1 0 92 8 —-0.03 +0.5 +1.3 2 50 94 6 —0.3 +0.4 +1.2 3 100 | 95 5 —0.4 +0.2 +0.06 A 400 96 & 0.0 —0.03 —0.03 After 6800 hr the salt in each capsule was removed and sampled. The capsules were opened and the specimens were removed, washed in warm dis- tilled water, dried with ethyl alcohol, and weighed., The specimens and capsules were examined metallographically and by x-ray fluorescence and microprobe analysis. The salts were analyzed before and after the tests. In our second series of experiments, the capsules were operated at 427°C (800°F), 538°C (1000°F), 649°C (1200°F), and 760°C (1400°F) with 5 psig He overpressure and calculated equilibrium BF,; pressures of 0,005, 0.07, 0.5, and 2.5 psia, respectively. After 1200 hr the salt in each capsule waS'removed and sampled for analysis. The salt had also been analyzed before test. RESULTS Effect of Salt Composition and BF, Pressure (Series I) Weight Changes The compositional changes in the salt effected by BF; gas additions in our first series of tests caused a measurable difference in the weight 'changes of our test specimens. As shown in Table 2, the weight changes were relatively small, and some specimens showed weight gains instead of the expected losses. There was no correlation between the pressure of BF; and the weight change of the specimens exposed to the vapor. | The speciméns immersed_in salt,in capsules 1, 2, and 3 showed pro- gressively decreasing'weight‘gains. The salt specimen -in capsule 4 showed - a weight loss equivalent to a corrosion rate less than 0.0l mil/year. The same weight change pattern was observed for the specimens at the interface. Thus, the weight gain of specimens in the liquid and at the interface increased as the amount of NaBF, in the salt decreased. Figure 5 shows the specimens éfter test. Very little corrosion was noted at any position on the specimens or capsules. " PHOTO 76206A VAPOR | ~—— INTERFACE SALT Fig. 5. Titanium-Modified Hastelloy N Specimens Aftter Exposure to NaBF,—8 mole 4 NaF at 605°C for 6800 hr. Numbers identify capsules. Salt Chemistry Chemical analyses of the salt before end after test for each capsule are given in Table 3. The most significant changes are an increase in chromium concentration and a decrease in iron concentration. No titanium concentrations are included in Table 3 because, as expected, Table 3. Salt Analyses Before and After Test (Series I) Concentration Element As Capsule Capsule Capsule Capsule Received 1 2 3 2 7 Welght Percent Na 21.9 21.4 21.0 21.8 21.0 9.57 9.54 9.48 9.48 9.49 68.2 £9. 2 68.5 68.7 68.8 Parts Per Million Cr 19 75 75 73 72 Ni 28 < 10 < 10 < 10 < 10 Fe 223 24 28 29 22 Mo < 10 <5 < 5 < 5 < 5 0 459 194 576 372 1420% H,0 400 400 460 350 460 aQnestionable result. no change was noted; only the test specimens contained titanium, and they constituted only a small part of the total system. The only change in the water and oxygen concentrations occurred in capsule 4. The high oxygen concentration reported for this capsule would normally have pro- duced highly oxidizing conditions® and high corrosion rates. The reported value is believed to be in error because close examination of the system disclosed no leaks or signs of oxidation. Apparently some BF3; escaped from the capsules after cooling and during opening, since the concentrations of sodium, boron, and fluorine in the salt were about the same in the final analysis of each capsule. The increase in chromium and the decrease in iron in the salt sug- gest a reaction of the type 8. E. McCoy, J. R. Weir, Jr., R. L. Beatty, W. H. Cook, C. R. Kennedy, A. P. Litman, R. E. Gehlbach, C. E. Sessions, and J. W. Koger, Materials for Molten-Salt Reactors, ORNI-TM-2511 (May 19692). 10 Cr(s) + FeF,(d) 2 CrF,o(d) + Fe(deposited) , (1) where (s) indicates solid solution in Hastelloy N and (d) indicates dissolved in salt. Any water or oxygen-type impurity in the salt would also have caused some oxidation of the container materials, but these impurities appear to have been negligible in this series of tests. 'Because the salt in these experiments contained NaF, the chromium fluo- ride in the corrosion product was found as NasCrFg. This material has also been identified in other corrosion experim.ents9 and its crystal structure has been determined by x-ray diffraction analysis.lo Also, the iron fluoride in these experiments may have existed as NasFeF¢, but this compound was not identified. Specimen Chemistry The proposed corrosion reaction was verified further by x~-ray fluorescence analysis of the specimens. Table 4 gives the composition of the near-surface region of a specimen from capsule 4. The composi- tion was determined by comparing x-ray intensities with those of a specimen not exposed to salt or vapor. For any given region in the capsule, the qualitative results from all the specimens were quite similar. These results show a depletion of chromium and enrichment of iron in the near-surface region. All specimens also showed a loss of titanium. Microprobe analysis showed essentially the same surface changes. A chromium gradient was seen but was so small that we could not distinguish between edge effects and an actual gradient. 1 According to Cantor, ! NaBF,—8 mole % NaF may also oxidize chro- mium by the reactions °J. W. Koger and A. P. Litman, Compatibility of Hastelloy N and Croloy 9M with NaBF,-NaF-KBF, (90-4-6 mole %) Fluoroborate Salt, ORNL-TM-2490 (April 1969). 105, Brunton, "The Crystal Structure of NasCrF¢," Mater. Res. Bull. 4, 621—626 (1969). = 11s. Cantor, MSR Program Semiann. Progr. Rept. Aug. 31, 1968, ORNI~4344, p. 160. 11 Table 4. Composition of Near-Surface Regions of Test Specimens as Determined by X-Ray Fluorescent Analysis Exposure Concentration (wt %) Conditions Mo Ni Fe Cr T4 Unexposed 12.0 79.9 0.1 7.5 0.5 Vapor 12.3 79.2 0.13 7.1 0.19 Interface 13.7 69. 6 13.4 3.0 0.2 Liquid 18.0 22.7 56. 4 2.7 0.16 (1 + x) Cr(s) + NaBF,(d) & NaF{(d) + CrFs(d) + CrXB(s) , (2) 3NaF(d) + CrFs(d) 2 NasCrFg(s) . (3) However, no borides were identified either on our specimens or in the salt, and the experimental evidence that iron replaced the chromium indicates that reaction (1) rather than (2) was the predominant mode of chromium oxidation. If essentially no iron fluoride compound were present in the melt, reaction (2) could well control the corrosion process. Metallography Figure 6 shows the microstructure of the specimen from the vapor region of capsule 1. There was some indication of a very thin, discon- tinuous deposit at the surface in the as-polished condition. After etching, this deposit was no longer visible; Figure 7 shows the speci- men that was exposed to salt in capsule 1. A deposit is visible on the as-polished specimen. Etching again removed the deposit but in this case produced considerable attack at the exposed surface. Metallographic observation of the capsule wall showed similar behavior. This deposit is apparently iron rich, and the area revealed by the etchant is chromium- depleted Hastelloy N. Thus, no difference in the behavior of titanium- modified and standard Hastelloy N was noted in this test. The interface between the salt and gas could be seen on the capsule, but no attack was noted there. 12 Fig. 6. Titanium-Modified Hastelloy N from Capsule 1 Exposed to BF3 Vapor for 6800 hr at 605°C. Weight change, +0.03 mg/cm?. 500x. (a) As polished. (b) Etched with glyceria regia. - i TN i e A Fig. 7. Titanium-Modified Hastelloy N from Capsule 1 Exposed to NeBF;~8 mole % NaF for 6800 hr at 605°C. Weight change, +1.3 mg/cm?. 500x. (a) As polished. (b) Etched with glyceria regia. oh X wy 13 - Effeet‘ef Tehperature (Series II) Our second serles of tests was des1gned to determine the effects of temperature on chromium.mass transfer from the Hastelloy N to the salt. The salt was analyzed(before and after test to determine 1nmmr1ty pickup The NaBF;—8 mole %‘N&F contained ‘approximately 400 ppm each of oxygen and water before and after test. rThe_chromium.concentration_in the salt . Increased while the iron decreased,'as'seen'in Table 5. No changes in the concentration of‘nickel and molyhdenumuwere noted. Again, the '-results suggest chromium oxidation by reduction of an iron fluoride compound. Metallography of: Hastelloy N from.this test showed, after \etching, no attack of the specrmen (Fig.-S) Table 5. Analy31s of Salt for Impurities Before and After Test o (Series II) - --Asz'erage-Concentrationa (ppm) Trpurity - As . Capsule Capsule Capsule Capsule Received ~~ 1 2 3 4 Cr 15 - 45 87 225 . 575 Fe 200 - 190 180 150 40 -0 460 430 - 450 . 412 550 “Hp0 - 320 - _ ;7400',' ' 530 480 . 490 SNickel and.molybdenumuwere not detected (( 10 ppm) in any sam@les. Fig. 8. Hastelloy N Exposed to NaBF4—8 mole % Na.F for 1200 hr at 760°C. Etched.with glyceria regis, 500x. 14 INTERPRETATION OF CORROSION RATES If the chromium surface concentration remainsg constant (only true if the salt contains an excess of iron) at any given point in the cap- sule, the amount of chromium leaving a capsule in Series I is given by the equationl? M = 20(Co — C) V/Db/7 () where MW = integral flux of Cr leaving metal, g/cm? p = density of metal, g/cm’ Co = initial weight fraction of Cr C_ = surface weight fraction of Cr D = diffusion coefficient of Cr in alloy, cm?®/sec t = exposure time, sec. Using the following informetion Salt in capsule = 282 g Cr increase in salt = 55 ppm (by weight) Capsule surface area = 142 cm? to obtain /AW and then using Co = 7.5% ¢, =0 (consistent with excess of Fe) o = 8.8 g/em? t = 6800 hr, we obtain Dagleg = 3-3 X 10-1° cm?/sec at 605°C. This compares favorably with 3 x 1071° cm?/sec at 605°C extrapolated from the range 700 to 850°C from datal?® of DeVan and Evans for chromium 12L. 8. Derken and R. W. Gurry, Physical Chemistry of Metals, McGraw-Hill, New York, 1953. 1°§. R. Grimes, G. M. Watson, J. H. DeVan, and R. B. Evans, "Radio- Tracer Techniques in the Study of Corrosion by Molten Fluorides," Pp. 559574 in Conference on the Use of Radioisotopes in the Physical Sciences and Industry, September 6-17, 1960, Proceedings, Vol. III, International Atomic Energy Agency, Vienna, 1962. 15 diffusion in Hastelloy N. From this comparison, we conclude that the controlling rate mechanism in this experiment was the solid-state dif- fusion of chromium in the alloy and that the oxidation potential of the salt was established by the presence of iron fluoride. Figure 9 shows the variation of chromium content with test temper- ature for the experiments of Series II. Included for comparison are chromium concentrations measured in loop tests after 1200 hr at various H,0 impurity levels.'*”17 An Arrhenius-type relationship appears to 147, W. Koger and A. P. ILitman, MSR Program Semiann. Progr. Rept. Feb. 29, 1968, ORNL-~4254, pp. 218-221. 157, W. Koger and A. P. Litman, MSR Program Semiann. Progr. Rept. Aug. 31, 1968, ORNL-4344, pp. 257—264. 167, W. Koger and A. P. Litman, MSR Program Semiann. Progr. Rept. Feb. 28, 1969, ORNL-4396, pp. 243—246. 175, W. Koger and A. P. Litman, Compatibility of Hastelloy N and Croloy 9M with NaBF,-NaF-KBF, (90-4-6 mole %) Fluoroborate Salt, ORNL-TM-2490 (April 1969). ORNL—-DWG 69— 12238R TEMPERATURE. (°C) 103 800 700 650 600 550 500 450 400 TN b ! ' I - ,‘4\@=22.0 kcal/mole |7 | \. A— - |- 5 N - . ] . N ,,_::.‘___‘(2000 ppm leo) ] . \‘\ (4000 ppm HZO) 2 b TN NS <‘O\O ppm HZ0) 1 | 10 — :fiifi; : ;f";_-w Cr CONCENTRATION IN FLUOROBORATE ({(ppm) 5 e T - — - ] 1 ——— e & ,| ' STATIC CAPSULE TESTS (1200 hr) s THERMAL CONVECTION LOOPS ] ----- CALCULATION BASED ON Cr DIFFUSION : IN HASTELLOY N 10 ' : ' ‘ ‘ 0.90 10 14 1.2 13 14 15 1000/r (o) Fig. 9. Temperature Dependence of Chromium Concentration in Sodium Fluoroborate Salt. 16 hold between 538 and 760°C. This would be expected if the rate of chromium buildup in the salt were controlled by solid-state diffusion of chromium to the capsule wall. Using diffusion data for chromium in Hastelloy N obtained by DeVan and Evans®® and assuming the chromium surface concentration to have been reduced to zero by the salt, we predict a chromium buildup shown by the dashed line in Fig. 9. The agreement between the slopes (activation energy) of the predicted and experimental curves, although not exact, gives credence to the assump- tion that chromium mass transfer to the salt is limited by solid-state diffusion of chromium to the Hastelloy N surface. CONCLUSIONS 1. Titanium-modified Hastelloy N specimens were exposed for 6800 hr to isothermal NaBF,-NaF salt mixtures containing only a few hundred parts per million oxygen and water and varying in composition from 4 to 8 mole % NaF. Specimens in the vapor region lost weight in all but the 96 mole ¢ NaBF, mixture. Specimens fully immersed in the salt gained weight in all but the 96 mole % NaBFs mixture. The weight gains decreased as the NaBF, content of the salt increased. 2. No differences in the corrosion of specimens in the vapor region were noted as a function of BF; overpressure to 400 psig. 3. In the main corrosion reaction, chromium from the alloy was oxidized by iron fluoride impurities initially in the salt. The iron that was reduced deposited on the specimens and capsule. 4. Metallographic observation of both standard Hastelloy N capsules and titanium-modified Hastelloy N specimens showed very little attack, although a thin discontinuous deposit rich in iron was observed at the surface of specimens exposed to vapor. 5. A diffusion coefficient for chromium in Hastelloy N calculated from the rate of chromium removal from standard Hastelloy N by NaBF,~8 mole % NaF held between 538 and 760°C agreed well with an extrapolation of published results. Thus, solid-state diffusion of chromium appeared to be the rate-controlling mechanism for corrosion in these tests. " 17 6. Under the condition of these experiments, the fluoroborate salt mixtures were compatible with the Hastelloy N alloys. By virtue of other experiments we conclude that increases in water as impurity increase the chromium uptake and the corrosion. ACKNOW LEDGMENT We wish to acknowledge E. J. Lawrence for his expert supervision of the fabrication, operation, and disassembly of the test capsules and F. D. Harvey for his handling of the test specimens. We are also indebted to H. E. McCoy, Jr., J. H. DeVan, and C. E. Sessions for con- structive review of the manuscript. Special thanks are extended to H. R. Gaddis and Helen Mateer of the General Metallography Group, Harris Dunn and others in the Analytical Chemistry Division, Graphic Arts, and the Metals and Ceramics Division Reports Office for invaluable assistance. 1-3. 4—5, 6—15. 16. 17. 18. 19. 20. 21. 22. 23. 24, 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43, 4te, 45, 46. 9394, 95. 96. 97. 19 INTERNAL DISTRIBUTION Central Research Library 47, ORNL — Y-12 Technical Library 48. Document Reference Section 49, Laboratory Records Department 50-52. lLaboratory Records, ORNL RC 53. ORNL Patent Office 54, MSRP Director's Office (Y-12) 55. G. M. Adamson, Jr. 56—65. J. L. Anderson 66. R. F. Apple 6'7. C. F. Baes 68. S. E. Beall 69. E. S. Bettis 70. F. F. Blankenship 71. E. G. Bohlmann 72. R. B. Briggs 73. S. Cantor T 0. B. Cavin 75. Nancy C. Cole , 76. W. H. Cook 77. J. L. Crowley 78. F. L. Culler 79. J. H. DeVan 80. J. R. DiStefano 81. S. J. Ditto ' 82. W. P. Eatherly 83. J. I. Federer 84. D. E. Ferguson g5. L. 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