ENGINEERING RESEARCH INSTI'ITUL'E UNIVERSITY OF MICHIGAN ANN ARBOR FINAL REPORT PART II. THE KINETICS OF DISSOLUTION OF SPECIAL TYPES OF ZIRCONIUM AND ZIRCALLOY-II IN HYDROFLUORIC ACID (- ' BRUCE G. BRAY ERIC H. DXtERENZ J. J. MARTIN Project Supervisor Project 2121-2 U.S. ATOMIC ENERGY COMMISSION CONTRACT NO. AT(10-1)-7355 March, 1954

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TABLE OF CONTENTS Page INTRODUCTION 1 EXPERIMENTAL PROCEDURE 2 Preparation of the Samples 2 Preparation of the Acid Solutions 2 The Constant-Temperature Reaction Vessel and GasCollecting Apparatus 2 Conduct of the Run 4 DATA AND EXPLANATION OF CALCULATIONS Sample Calculation 14 Observations during the Runs 16 CONCLUSIONS 17 BIBLIOGRAPHY 24 ii

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN FINAL REPORT PART II. TBE KINETICS OF DISSOLUTION OF SPECIAL TYPES OF ZIRCONIUM AND ZIRCALLOY-II IN HYDROFLUORIC ACID INTRODUCTION As a result of preliminary work at the University of Michigan on the effect of oxidation and surface coating on the dissolution rates of zirconium and Zircalloy reported in June, 1953, 1 and recommendations made in an Engineering Research Institute progress report of September, 1953,2 interest was shown in further experimentation in this field. Several selected samples with various surface coatings were received from the Phillips Petroleum Company, together with a revised schedule of research from the U.S. Atomic Energy Commission, Idaho Operations Office. These samples had various surface coatings which were to be investigated for their effect on the dissolution rate of the material. Both zirconium and Zircalloy-II samples were received. The samples were designated as types A, B, and C: type A was Zircalloy-II with a black oxide coating, type B was a zirconium crystal bar with a white oxide coating, and type C was a zirconium crystal bar with a black oxide coating. Pure zirconium and Zircalloy-II were available here and similar tests were run on them, The experimental runs were made at 100~C, near the refluxing temperature of the hydrofluoric acid solutions used, Gas evolution was measured for two rates of acid addition to the sample. Tables and graphs of the data taken are presented in this report along with a method of transforming the dat;a to dissolution rates.

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN EXPERIMENTAL PROCEDURE Preparation of the Samples The samples of types AY B, and C were run in the as-received condition from the Phillips Petroleum Company. They were individually wrapped in tissue when received and were handled only preceding a run when being weighed and measured. The samples of uncoated zirconium and Zircalloy-II were machined from pieces received earlier from the American Cyanamid Company. These samples were washed, degreased with acetone, and then weighed and measured. Preparation of the Acid Solutions In the dissolution experiments reported earlier (Progress ReportlO, September, 1953) samples of metal were placed in large volumes of hydrofluoric acid solutions of given concentrations and allowed to react. In the work reported here the procedure was quite different. Each sample was immersed in distilled water which was maintained at about 1000C. At zero time strong hydrofluoric acid (about 48*) was allowed to start dropping into the water. The acid flow was continued until the total fluoride ion in the reaction vessel was 7.4 molar. This point was determined from the quantity of distilled water used, the amount of 48% acid added, and the specific-gravity - concentration tables prepared by Elving, et al.3 The total quantity of acid was dependent on the mass of the metal to be dissolved, 1 gram of 100% HF being added for every gram of metal, The Constant-Temperature Reaction Vessel and Gas-Collecting Apparatus A schematic diagram of the equipment used is shown in Fig. 1. A copper reaction vessel, three gas-collecting burettes, and a jacketed temperature vessel were the main pieces of equipment. Auxiliaries consisted of a hydrofluoric acid dropping funnel, a condenser, and pieces of tubing. The hydrofluoric acid dropping funnel was constructed from a small polyethylene bottle and a 1/16-inch-ID polyethylene tube. The bottle was suspended 6 feet above the reaction vessel to minimize variation in acid rate due to hydrostatic head loss. A pinch clamp was placed in the line to control the flowrate. At a distance of 3 inches above the entrance into the reaction vessel the small tubing was joined to a 3/8-inch-ID tube in order to facilitate measurement of the acid addition rate, Drops of acid were

P pinch clamp for EF control polyethylene A, B, C, D three way glass stopcocks container and tubing Glass equipment from condenser on. hood _P 2-500 ml gas buri_ H20 ettes thermometer -+ K-Cu reaction vessel 1-100. gas burette steam,m * -tW 1 +steel and Cu bomb __- - - shown in Report, Sept. 1953, Ftig. 7 high boiling oil condensate Fig. 1. Schematic Diagram of the Equipment.

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN counted in order to maintain a constant flowrate. The apparatus was calibrated in grams per minute versus drops per minute. The reaction vessel was constructed from a piece of 2-inch-ID purecopper pipe with one end sealed. A polyethylene-coated rubber stopper with openings for the acid addition tube and a glass condenser provided the top for the vessel. The reaction vessel was placed in a bath of oil held in a steamJacketed container (Fig. 7, in the September, 1953, Progress Report). The temperature of the oil was controlled by regulating the steam pressure to the jacket. The hydrogen evolved in the course of the reaction passed through a glass condenser to the collection burettes. Any entrained or vaporized water or hydrofluoric acid was collected on the sides of the condenser to drip back down into the reaction vessel, Although glass is subjected to attack by hydrofluoric acid, polyethylene does not have the required heat-transfer properties to condense water and hydrofluoric acid. Preliminary tests made with a glass condenser indicated that there was no appreciable attack on the glass during the length of time required for a run. The hydrogen passed from the condenser into one of three gas-collecting burettes. At the start and conclusion of each run the gas was collected in a 100-mi burette. At these times the reaction rate, and thus gas evolution, were small enough to permit collection in the i8TGWml burette without danger to the operator. During the middle portion of each run the gas was collected alternately in two 500-ml burettes, which were large enough to handle the gas safely at a fairly high rate. While gas was being collected in one burette, it was being vented to the hood from the other. Conduct of the Run The samples were suspended in the reaction vessel by a polyethylene support that touched the sides of the sample only at two small points. The apparatus resembled a pair of ice tongs, which held the sample satisfactorily in a vertical position, allowing the acid to contact all sides of the sample. A known amount of water was placed in the reaction vessel with the suspended sample and the stopper containing the condenser was placed in position and the condenser connected to the gas burettes. The reaction vessel was then put in the hot oil and heated to 100~C before the acid addition~ A stopclock was started when the first drop of acid was observed to fall into the reactors The acid rate was regulated to a predetermined value and the gas was collected as described previously. The acid was shut off at the time calculated from the rate of acid addition and the total amount of acid needed. The reaction was allowed to go to completion and then the reactor was

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN dismantled and removed from the oil bath, The final solution containing any undissolved residue was poured out for examination. The system was tested for air leaks before proceeding with the experimental run. The number of samples provided permitted only two runs to be taken at any one acid rate for any one type of coating. DATA AND EXPLANATION OF CALCULATIONS The volume of gas evolved was corrected to standard conditions from the average temperature of the gas recorded during the run. This was also checked stoichiometrically against the theoretical volume predicted by the equation for the reaction, Zr + 4HF = Zr F4 + 2H2 In checking the Zircalloy, all the sample was assumed to be pure zirconium and any reactions involving alloying constituents were neglected. In all cases reported here this balance was well within the expected error, considering the system used. In the single case where this value did not check, an appreciable air leak was found; this run is not reported. The volume of H2, corrected to standard conditions, is plotted as a function of time for the acid addition rate used (see Tables III through VII and Figs. 2, 3, 4, 6, and 7). From these graphs the number of moles of zirconium dissolved is calculated from the stoichiometric reaction, The mass is then the molecular weight times the number of moles, Expressed in symbols this is.Mz dissolved L(cm3 H2 evolved.)(MW7r) Mzr dissolved = (22,400) (2) By assuming uniform attack by the acid, the mass balance around a typical sample (shown above) may be written, The mass of zirconium dissolved is the density, p, times the change in volume of the sample. Expressed in

TABLE I PHYSICAL CHARACTERISTICS OF COATED SAMPLES Initial Initial SaType Coating Identiicatin Weight, Dimensions, Sample Coating Numbers gm in. A-I 2 --- 7 11.0183 (0.950)(0093)(1.173) A-II 2 --- 6 12.3763 (0.946)(0.114)(1.083) B-I 1 --- 8 13.,6908 (o.669)( O104 ) ( 1.905 ) B-II 1 --- 9 14.4535 (.666 ) (.111)(1.891) C-I 599T - 201 11.7636 (0.380)(0.223) (1344) C-III 1060 - 1828B 17.4635 (0.502)(0.213)(1.583) Uncoated Zr-I pt-e P-I 9.2493 (0.595)(0.129)(1.221) Uncoated Zr-II r pu P-EF 8.5742 (O. 523) (0.144 ) (1.225) Uncoated- 8,7215 (0.478)(O.170)(1.027) Uncoated ~ %a-Ji 9.4878 (O 503)(O. 169)(1.068) A-III, 2 -- 1 - 7292 12.9368 (0.877)(0.117) (1179) *B-III 1 --- 1 15.1692 (0 719)(0.106)(1.897) *B-IV 1 --- 4 15.4490 (0O721) (0108) (1.906) C-IV 223 - 690B 18.4030 (O.480)(0.241)(1.532) Uncoated Zr-III p. ci_ - 1'7 4.7194 (0.481 ) ( 0.110) (.979) Uncoated i_ WtII 8.9595 (0.581)(0o164)(0.910) *Reaction too rapid to measure gas volume.

TABLE II EXPERIMENTAL CHARACTERISTICS OF COATED SAMPLES Theoretical Total Wt.'- Total Wt. Type of Vol.of Gas Released Acid Rate 48% HF H20 Present Gas Coating at Std. Cond., gm/min Added, at Start, Temp. cm3 gm m A-I 5410.50 21.5 57.2 314 A-II 6077.50 235.0 64.2 309 B-I 6722.50 26.5 71.0 320 B-II 7097.50 28.0 75.0 311 C-I 5776.50 22.5 61.0 312 C-III 8575.50 33.0 90.6 315 Uncoated Zr-Ipc. P —I 4541.50 18.0 48.0 301 Uncoated Zr-II 'c- P-2 4210.50 16.5 45.6 314 Uncoated-f ~ 47I_ 4282.51 17,8 45.3 313 Uncoated -Zi - 4 I 4659.50 18.5 49.2 311 A-III 6352 1.14 26.2 67.1 314 *B-III 1.14 78.7 C-IV 9036 1.24 40.0 95 5 321 Uncoated Zr-III?,Ae'J 12317 1.20 10.2 26.8 319 Uncoated J;2 & 4399 1.33 19.9 46.5 311 *B-IV 1.23 80.2 *Reaction too rapid to measure gas volume.

TABLE III TIME AND TOTAL VOLUME AT STANDARD CONDITIONS OF H2 EVOLVED FOR TYPE A A-I A-IT A-III Time, H2 Evolved Time, H2 Evolved Time, H2 Evolved min sec cm3 | min sec cm3 min sec c Cm3 13 30 87 11 39 88.4 6 28 87 18 22 522 13 25 177 9 17 521 20 30 956 16 51 618 10 46 956 22 26 1391 18 32 o1060o 11 58 1390 24 25 1826 20 00 1502 13 08 1825 26 30 2260 21 37 1944 14 22 2259 28 58 2695 23 31 2385 15 41 2694 31 46 3130 25 55 2827 17 03 3128 35 02 3565 28 39 3269 18 34 3563 38 22 3999 31 42 3711 20 14 3997 41 50 4434 34 58 4152 22 04 4432 42 35 4521 38 30 4594 24 05 4866 47 10 4956 42 08 5036 27 47 5388 48 36 5043 46 32 5478 33 44 5822 50 40 5129 52 05 5831 35 37 5909 53 45 5216 55 00 5920 37 51 5996 56 00 5260 58 46 6008 40 36 6083 58 55 5303 62 27 6052 44 14 6170 63 13 5347 73 30 6070 49 23 6257 70 35 5390 55 40 6344 79 25 5412 _,,,,,~'.....,... i, _ ~ ~,,,_, ~,_,~-,,, ~ il 8.,

TABLE IV TIME AND TOTAL VOLUME AT STANDARD CONDITIONS OF H2 EVOLVED FOR TYPE B B-I B-II B-III Time, H2 Evolved Time, H2' Evolved Time, H2 Evolved min sec cm3 min sec cm3 min sec cm3 7 33 64 10 33 88 7 14 88 8 24 85.3 11 44 176 7 30 513 10 04 171 13 13 614 11 46 597 14 01 1053 12 49 1024 15 01 1492 14 08 1450 17 04 1931 B-IV 16 36 1878 20 06 2370 5 23 89 18 57 2304 23 43 2809 7 45 515 21 48 2730 27 12 3248 8 20 998 24 48 3158 30 43 3687 28 09 3583 34 21 4126 31 22 4008 38 00 4565 34 38 4438 41 56 5003 37 54 4860 45 45 5442 41 17 5290 49 23 5881 44 29 5718 52 54 6520 47 53 6142 56 09 6759 52 37 6563 62 30 7089 56 02 672o 60 00 6723...._.....|, ->.9

TABLE V TIME AND TOTAL VOLUIVE.AT -STANDARD CONDITIONS OF H2 EVOLV-ED FOR TYPE C C-I -III C-IV Time, H2 Evolved| Time, H2 Evolved Time, H2 Evolved min sec cm3 min sec m3 min sec cm3 4 10 22 7 14 43 3 44 85 4 52 44 8 24 87 5 41 510 5 18 66 9 38 173 6 52 936 5 39 88 12 40 607 8 00 1361 6 35 175 14 46 1040 9 09 1786 9 27 613 16 34 1474 10 22 2211 12 02 1050 18 32 1907 11 45 2637 14 20 1488 21 00 2341 13 20 3062 17 27 1925 24 12 2774 15 00 3487 20 48 2363 27 39 3208 16 42 3912 24 30 2800 31 13 3641 18 28 4338 28 15 3238 34 50 4075 20 15 4763 32 16 3675 38 27 4508 22 03 5188 36 22 4113 42 23 4942 23 52 5613 40 30 4550 45 28 5375 25 42 6039 44 58 4988 48 29 5809 27 32 6464 51 00 5425 51 44 6242 29 29 6889 51 30 5447 55 12 6676 31 27 7314 51 58 5469 58 56 7109 33 36 7740 52 26 5491 63 00 7543 36 25 8165 52 57 5513 67 32 7976 40 52 8590 54 04 5556 72 23 8267 4'2 12 8675 55 23 5600 74 39 8354 44 00 8760 56 53 5644 77 46 8440 45 45 8845 58 45 5688 61 32 5731 82 15 8527 48 15 8930 63 30 5753 84 25 8570 51 45 9015 68 30 5775 54 30 9029 10

TABLE VI TIME AND TOTAL VOLUME AT STANDARD CONDITIONS OF H2 EVOLVED FOR UNCOATED PURE ZIRCONIUM Uncoated Zr-I P -IZI Uncoated Zr-II?-L Uncoated Zr-III T L Time, H2 Evolved Time, H2 Evolved Time, H Evolved min sec cm3 min secm3 mi secm3 2 05 91 2 07 87 2 25 428 6 08 544 5 23 521 4 39 856 9 40 998 8 50 955 7 04 1284 13 44 1451 13 07 1389 10 00 1712 17 46 1908 17 19 1823 12 13 1892 21 39 2358 20 52 2257 13 46 1977 25 36 2812 24 10 2691 15 42 2063 29 34 3265 27 56 3125 18 20 2149 33 42 3719 32 12 3559 21 50 2234 34 37 3809 38 44 3993 27 09 2320 35 33 3900 41 29 4080 36 28 3991 45 56 4166 37 31 4082 50 30 4210 38 50 4172 40 32 42653 43 14 4354 47 58 4444 51 40 4490 56 48 4535 11

TLABIE VII TIME AND TOTAL VOLUME AT STANDARD CONDITIONS EVOLVED FOR UNCOATED _4 a Uncoatedcx Z Uncoated: -Z E Uncoated -i r I Time, H2 Evolved Time, H2 Evolved Time, H2 Evolved min sec e cm3 min sec c3 min sec | cm3 4 12 436 1 57 88 2 43 439 7 27 872 5 25 527 4 17 878 10 58 1308 8 46 966 5 54 1317 14 02 1744 12 43 1405 7 35 1756 17 12 2180 16 53 1844 9 21 2195 20 41 2616 20 54 2283 11 10 2634 24 21 3052 24 50 2722 13 07 3074 28 24 3488 28 53 3161 15 04 3512 33 10 3924 33 04 3600 17 39 3951 41 00 4282 37 29 4039 19 13 4127 39 41 4223 20 24 4214 41 03 4311 22 06 4302 42 43 4399 25 35 4390 44 59 4487 27 30 4404 48 25 4574 55 49 4662

TABLE' VIII TABLE OF DISSOLUTION RATES FROM PREVIOUS WORK AND CALCULATED VALUES FOR COATED C-III Temp., 1/T, K Dissolution Rate, (.m/cm2-sec) 105 OC.75MHF 1.05MHF O..46MHF 1. Previous Work* 30.0033 6 11 50.0031 7.5 16 80.00283 10.5 24 2. Calculated Values 100.00268 27.7 19.4 33 *Interpolated data from September, 1953, Progress Report. 13

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN the symbols used in the sketch, where a, b, and c are the initial dimensions, Mzr dissolved = P [a c I + a b I + b c I - 13] Combining these two expressions for the mass of zirconium dissolved, (cm3 H2 evolved.) (zr) = p [(a c + a b + b c) I - 1)] * (22,400)(2) At any point on the curve all quantities but I are known and this may be calculated. Assume 13 = 0 for the first approximation. Calculate I, and then observing that 13 is to be subtracted from the I term, assume a slightly larger value of 1, and recalculate. For the first several points on the curve the approximation 13 = 0 will actually be good, as a very small amount of zirconium has been dissolved. The area of the sample at this time will be A = 2 [(a - )(b - 1) + (a - l)(c - I) + (b - )(c - I)] The slope of the curve at this time, multiplied by the factor (MWzr)/(22400)(2) gives the instantaneous weight loss in gm/min. Dividing by the area gives the dissolution rate at that time. From knowledge of the rate at which acid was added in moles/min, the time, and the moles of zirconium dissolved, the acid concentration for the point can be calculated. The point calculated for curve C-III in Fig. 4 at 10, 30, and 70 min. are plotted in Fig. 5. They are checked against previous rates reported2 for pure zirconium by extrapolation of a plot of log. Dissolution rate versus 1 'T. It is seen that they are well within the range predicted by the extrapolation. The variation is probably due to the assumption of a uniform attack on the sample. At the low value of 10 min it is seen from Fig. 4 that the reaction is just starting. The attack is probably taking place at a few cracks that have appeared in the surface coating; not all of the total initial area is exposed to the attacking acid solution as was assumed. At the high value of 70 min, the area is again questionable, since any rounding of corners or pitting of the sample would change the area from the assumed value. The center portion of the curves probably represent a reacting area closest to that which was assumed. Sample Calculation Sample calculations for point 1 of Fig. 5, using data from curve C-III of Fig. 4 to give the reaction rate as a function of HF concentration, are shown below:

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Molecular weight of zirconium = 91.22 Initial dimensions a = 0.502 in. = 1.275 cm b = 0.213 in. = 0.541 cm c = 1.583 in. = 4.021 cm Initial weight = 17.4635 gm. At T = 10 min on Fig. 4, cm3 H2 at Standard Conditions = 225 Slope curve C-III at 10 min = 90 cm min From the combined expression I is calculated, neglecting the term -13 for the moment; (225)C91.22) (22,400) (2) (1(17.4635)(1) [(1.275) ~.541 + 1.275' 4.021 +.541- 4.021] (1.2"j'5)(.541)(4.021) Z = 0.009 cm Then, 13 = -0.729 x 10-6 and is negligible, as was assumed. A = 2 [(1,266)(.532) + (1.266)(4.012) + (.532)(4*012)] A = 15.774 cm2 Dissolution Rate = (90)(91.22) = 0.0116 gm (44,800 )(15774) cm2-min Acid Rate = 0.50 gm/min of 48% acid for 10 min Remaining Moles of HF = [(10)(050)(0.48) _(225)(2) = 0.100 20 22, 400 Molarity = -(lOO)(o.100)L = 1,05M 90.6 + (0.5)(10) The term in the denominator is a volume correction for the addition of 48% acid for 10 min to the water already in the reactor. 15

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN By similar calculations the reaction rate at 30 min is found to be 0.0198 gm/cm2-min and the acid concentration is 0.46 molar. At 70 min the rate is 0.0166 gm/cm2-min at an acid concentration of 0.75M. Observations during the Runs In the runs with pure uncoated zirconium and uncoated Zircalloy-II, the reaction proceeded as expected with very little or no initial delay, the reaction starting immediately on addition of acid. This is shown by the immediate evaluation of gas. The reaction proceeded as a direct function of time and rate of acid addition until the acid was shut off and the area of attack became small. As expected, the faster the acid rate, the faster the reaction rate (Figs. 6 and 7). With the coated samples, types A, B, and C, the reaction proceeded somewhat differently. There was an initial delay before the main reaction started due to the surface film's resistance to attack. During this time the acid concentration builds up to a higher value than if the reaction had been proceeding. When a crack or break in the film occurs the reaction proceeds for a time at a higher rate than the equilibrium rate. This period is represented by the first straight-line portion of the curves in Figs. 2, 3, and 4. The hump approximately one-third of the way along the curve is due to the reaction slowing down as the rate approaches the equilibrium reaction rate. The second straight portion of each curve represents the equilibrium rate, which is established by the rate of acid addition and is not primarily dependent on the initial buildup of acid. Then as the acid is shut off and the area becomes smaller, the rate dries off as shown by the curvature of the final section of the graphs. Since in all cases there was an excess of acid, the volume of gas collected goes up to the theoretical value predicted from the stoichiometric balance and stops rather than approaching an asymptotic value. The variation in slope between two individual samples of the same type at the same acid addition rate, e.g., curves C-I and C-III in Fig. 4, may be explained by the fact that C-III has a larger surface area than C-I. This indicates that the mass transfer of H2 from the surface to the solution or in the reverse direction has an appreciable effect. Assuming that the rate of Hp transfer is constant, and that the metals are exactly the same below the surface coating, a greater surface area will correspond to a greater reaction rate. With no mass-transfer effects present, the rates should be exactly the same on a gm/cm2-min basis. No external agitation was employed. The spraying action of the Hn evolved from the reaction and the gentle refluxing supplied the only agitation. 16

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN In all the solutions containing the coated samples and the solutions containing the uncoated Zircalloy, a residue remained. In the uncoated Zircalloy-II solution the residue was a black spongy-looking material. It might be undissolved alloying constituent. This same black spongy residue was present in the solutions from type A along with material that looked like the surface film itself. It seems that the acid, once having cracked the film, worked underneath it and caused it to peel off. Bubbles of H2 would force off bits of coating which would drop to the bottom of the solution. The same flaky material was present in the runs from both types B and C. In the case of type B, it resembled little white granules. At no time were these residues appreciable in relation to the sizes of the samples. They were not weighed, but it was estimated that the black spongy material weighed less than 2 percent of the total weight and the flaky residue less than 0.5 percent. The temperature remained constant in the reaction vessel, as the copper provided good heat conduction during the reaction. On removal of one of the samples from the reactor before the reaction was complete, it was found that the assumption of uniform attack was not completely correct. The sample was rough and pitted, possibly because of heat treatment or crystal structure variation. CONCLUSIONS The most important results and observations have been mentioned in the preceding section. At an acid addition rate of 0.5 gm/min of HF, the reactions in all cases proceeded smoothly with rates that could be handled with the experimental equipment. At roughly twice this acid rate (1.14 to 1.23 gm/min)-the type B samples got out of control. The initial buildup of acid started such a fast reaction that the gas could not be collected. The portions of the curves that were obtainable are presented in Fig. 3. In all cases the delay in initiation of the reaction seems to decrease with increased acid addition rate, probably because the acid builds up more quickly to a concentration that will attack the imperfections in the coatings and cause breakdown. This speed of breakdown does not increase proportionately with the acid buildup, however, as evidenced by the extreme rate encountered with type B at the higher acid addition rate. 17

7000 6000 5000 loooO 0o00 3W)O Fig. 2. Total Volume H2 at Standard Conditions Liberated Versus Time for Type A. 2000 x A-I A A-III 1000 -' 0 10o 20 3o 40 tim0(mi) 60 7o no 9o

8000 7000 x 6000 I/ /x K "a l/ 4000 / A/ 2000 I~oo r ~ / Fig. 3. Total Volume H2 at Standard Conditions Liberated Versus Time for Type B. Cx B-I 1900I~~ F X S|B-III / B-IV 0 10 20 50 40 50 60 70 time (min) 19

10,000 9ooo000 8000 oo x 7000 -- 6000 5000 4000 3000 2000- Fig. 4. Total Volume H2 at Standard Conditions Liberated Versus Time for Type C. 0 C-I 1000 x C-III C-IV 0 10 20 30 40 50 60 70 80 90 time (min) 20

8 - 774 Fig. 5. Check of Calculated Points for C-III 4 - to Extrapolated Previous Values. C)Batch Dissolution of Zr 2 from Report 10, Sept. 1955 L Calculated Values from H2 Evolution, Curve C-III, Fig. 4 21

5000 4000 3000 El 2000 Fig. 6. Total Volume H2 at Standard Conditions Liberated Versus Time for Uncoated Zirconium. O P-I 1000 x P-II A P-III 0 10 20 30 40 50 60 70 time (min.) 22

6000 5000 4000// C9 ) 3000 o 2000 Fig. 7. Total Volume H2 at Standard Conditions Liberated Versus Time for Uncoated Zircalloy II. 1000 0 ZA-I x ZA-II A ZA-III O 10 20 30 40 50 60 70 time (min.) 23

BIBLIOGRAPHY 1. Bray, B.G., Doberenz, E.H., Welshans, L.M., and Martin, J.J., "The Effect of Oxidation on Dissolution Rate", Preliminary Report, Univ. of Mich., Eng. Res. Inst. Proj. 2121, June 25, 1953. 2. Bray, B.G., Doberenz, E.H., Welshans, L.M., and Martin, J.J., "The Kinetics of Dissolution", Progress Report 10, Univ. of Mich., Eng. Res. Inst. Proj. 2121, September, 1953. 3. Elving, P.J., et al., "Control Indices and Analytical Procedures", Progress Report 3, Univ. of Mich., Eng. Res. Inst. Proj. 2121, August, 1953. 4. American Cyanamid Company Report No. ACCO-4210 (Classified). 5. Argonne National Laboratory Report No. 4872 (Classified). 6. Baumrucker, J.E., "Dissolution of Zirconium in HF", Argonne National Laboratory Report No. 5020, March, 1950. 24

UNIVERSITY OF MICHIGAN 3I 9l0 Ill)IlIIl 111 9 I I 6I90l 111 1 11111IIII11II1I 3 9015 02519 6901