Preliminary corrosion studies of glass ceramic code 9617 and a sealing frit for nuclear waste canisters

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1 93 g vt A Preliminary corrosion studies of glass ceramic code 9617 and a sealing frit for nuclear waste canisters I D Sundquist Corning Glass Works POSTADRESS: Kåmbrånsf^åk»rh»t, Fåck Stockholm. Tffon

2 PRELIMINARY CORROSION STUDIES OF GLASS CERAMIC CODE 9617 AND A SEALING FRIT FOR NUCLEAR WASTE CANISTERS I F Sundquist Corning Glass Works Denna rapport utgör redovisning av ett arbete som utförts på uppdrag av KBS. Slutsatser och värderingar i rapporten är författarens och behöver inte nödvändigtvis sammanfalla med uppdragsgivarens. I slutet av rapporten har bifogats en förteckning över av KBS hittills publicerade tekniska rapporter i denna serie.

3 PRELIMINARY CORROSION STUDIES OF GLASS- CERAMIC CODE 9617 and a SEALING FRIT FOR NUCLEAR WASTE CANNISTERS J. D. Sundquist Corning Glass Works Corning, New York March 1, 1978 for Karnbranseisakerhet Order No. 166 Stockholm, Sweden

4 PRELIMINARY CORROSION STUDIES OF GLASS- CERAMIC CODE 9617 AND A SEALING FRIT FOR NUCLEAR WASTE CANNISTERS J. D. Sundquist ABSTRACT At the request of ASEA-ATOM, Sweden, a study was initiated to evaluate glass-ceramic Code 9617 and a sealing frit (glass Code 186AYU) to determine the suitability of these materials for use in the construction of a cannister to contain and permanently isolate spent nuclear fuel rods. The study was aborted after one quarter of the work was completed. Nevertheless, results obtained define test conditions for future work and provide preliminary estimates of corrosion rates. The granite repository storage conditions included ground water in contact with bentonite clay plus sand with temperature cooling from 100 to 0 C in 500 years. The water exchange rate is 1 ml per cm* of cannister surface per year. Tests were conducted at 60,, 130, and C. Most of this preliminary work was done with distilled water with a few tests in water containing bentonite and sand or salt. It is recommended that future tests be conducted under conditions which embrace the actual storage temperatures, thus allowing prediction of long term rates from an extrapolation of time rather than from the accelerated effect of increased temperature which our results indicate may alter the reaction mechanism. Other test conditions should also simulate real conditions as nearly as possible. Of particular importance is a consideration of the changing chemistry of the test solutions when "static" conditions arc used; i.e., when the test solution remains in contact with the test specimen for long periods of time. Preliminary data suggest that the glass-ceramic would lose about 0.1 en of thickness in the first 1000 years of storage. presents a comparison of estimated corrosion rates as a function of temperature for a flowing and a static water system. o There is little evidence to suggest that the corrosion rate in u ground water/bentonite/sand mix or in salt water would differ by more than an order of magnitude. z.1 It appears that the spodumene o fraction of the glass-ceramic is very corrosion resistant, even at C. os.01 O This suggests that modifications in bulk composition or processing could dramatically decrease overall corrosion.001 rates. The figure shown below 100 T ( C) 200

5 March 1, Introduction At the request of ASEA-ATOM, Sweden, a study was initiated in July, 1977, to evaluate glass-ceramic Code 9617 as a cannister material for the containment of spent nuclear fuel rods. Corning was to have one year to determine whether it could fabricate the large (1$ by 8 foot) cylinders, seal them and assure that they would survive the environment in which they would be stored. There were three areas of study: 1. feasibility and cost of fabrication 2. physical durability of the cannister in the proposed environment, and 3. chemical durability of the cannister in the 'proposed environment. The project was discontinued October 31, This report details the chemical durability study (item 3) up to that time. The objectives were to: 1. evaluate methods of testing, and 2. use the best methods to predict corrosion over a 1,000 year span. We have completed objective 1 and have some preliminary data concerning objective 2. In this report, I: 1. discuss the proposed site conditions, 2. describe the experimental approach 3. provide an evaluation of the various methods and techniques, and. estimate corrosion rar:es from the preliminary data, and discuss possible'mechanisms of attack.

6 March 1, 1978 (Sundquist, J. D.) Problem Definition-Repository Conditions The proposed repository conditions are summarized below: a mixture of 9 parts sand and 1 part bentonite will be packed around the spent fuel rods contained in the cannister, the cannisters will be stored in shafts 500 meters deep in granite and surrounded with the 9 sand and 1 bentonite mix, the temperature is initially 100 C, cooling to 60 C after 100 years, 0 C after 500 years and 25 C after 3000 years, (see zeolite, Figure 2), 'the ground water flow through the granite will be 1 Iiter/meter2/year, the ground water composition will be as shown in Table 1. Figure 1, represents the proposed storage configuration as we understand it: cannister 9' sandal bentonite.".- Figure 1. Proposed Repository Configuration.

7 March 1, o 100 u 1 50 u DRY QUARTZ SAND DAY ZEOLITE (MOST LIKELY) WET ZEOLITE WET QUARTZ normal, jite_ temperature 7k * 7öV JL OT5 IÖÖ" TIME AFTER DEPOSITING (YEARS) "SöV7/ / b!ro' Figure 2. Temperacure decay curve in granite repository. (Spent fuel rods are stored 10 years before placing in cannisters.then stored 0 years before being placed in the repository.) (Reference J.)

8 March 1, ASEA-ATOM Addendum to Inquiry of February Water chemistry for materials selection: PH Ca Mg Na K Cl SO* HCO 3 NO 3 P0 F SiOj II Fe Mn II mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 Table 1. ASEA-ATOM Definition of Ground Water at Repository' Site.

9 March 1, For one cannister I have made some calculations from the previous information to aid in our experimental design, method and evaluation: LATERAL SHAFT: Void Volume Surface Area 36.8 ma 53.6 m 2 VOLUME OCCUPIED BY CANNISTER OUTSIDE SURFACE AREA- (SHAFT VOLUME) - (CANNISTER VOLUME) * 36. m 3 (9) sand + (1) bentonite packing density «sand density «0.39m 3.86m x 10 3 I 1.63 gms/cc 2.35 gms/cc bentonite density 2.0 gms/cc sand/bentonite mix 707. solid and 30% void FINAL VOID SPACE - (30%) x (36. x 10 3 )L WATER LEAK RATE IN - TIME TO FILL VOID x 10 3 L 56.6 L/year 200 years SOLUTION VOLUME TO CANNISTER SURFACE AREA RATIO cc/cm 2 RATE OF CHANGE OF SOLUTION = 1.1 cc/year/cm 2 of cannister

10 March 1, Equipment and Test Conditions The time interval over which we seek to predict corrosion is extremely long. To shorten laboratory testing time we frequently accelerate tests by increasing temperature and/or solution corrosivity and then extrapolate back to the real-life condition. This is relatively easy when predicting for a few years. To apply this technique to a 1,000 year interval requires further consideration. The changing test solution chemistry becomes critical as does the changing on-site chemistry. Also, the increased temperature required may introduce new variables. In this light our present and proposed test procedure and methods of evaluation were studied in detail. 3.1 Equipment The glass-ceramic candidate (CGW Code 9617) and frit (experimental) were tested at temperatures of 60,, 130, and C. We purchased high temperature ovens and constant temperature baths from the Blue M Company, Long Island, New York and reaction vessels (high temperature bombs) from the PARR Instrument Company, Chicago, Illinois. Chemically resistant glass test tubes were obtained from our company. Figures 3 and show some of the equipment. 3.2 Test Conditions The glass-ceramic and frit durabilities were studied in distilled, deionized water at the four temperatures indicated in 3.1. The variables evaluated included time, temperature and the ratio of test solution volume to test sample surface area. The latter will hereafter be referred to as "the ratio" or "R".

11 March 1, We also obtained some data on the effect of a 9 sand and 1 bentonite mixture and on the effect of an aqueous solution of sodium chloride on durability. Our evaluation methods included weight loss, atomic absorption analysis of the test solution, and 5 methods of sample surface analysis. These methods were scanning electron microscopy, transmission electron microscopy, transmission x-ray energy dispersion analysis; x-ray diffraction and H profiling by. Data N bombardment. A considerable amount of data was obtained. Because the project was terminated many experiments were not concluded. Other experiments, though completed, have not been validated with replicates. In Sections 5 and 6 1 discuss the results which we feel are significant.

12 M.~rch 1, 1978 (Sundquist. J.D.) Figure ml High-Temperature Nickel Coated Reaction Vessels. (Bombs)

13 March 1, (A) (B) (C) Figure ; Photographs of some of the equipment. (A)-constant temperature bath. (B)-oven. (O- mini-reactor. - -

14 March 1, Study of Test Methods This section includes the evaluation of the test equipment and an evaluation of the various analytical tools that were employed throughout the study. 5.1 Equipment High temperature reaction vessels ("bombs") of various composition and size were considered. Materials considered were tantalum, monel, stainless steel and nickel. Corrosion resistance, cost and delivery time led us to select nickel-plated 22 milliliter bombs. Fifty milliliter Corning Code 770 test tubes with screw tops were used for most of the low temperature work. They were pre-aged in hot hydrochloric acid. Ås the tests proceeded th? decision was made to switch to plastic test tubes since the relatively large surface area of the tubes compared to the samples gave high blank values. The ovens and baths functioned well. The mini-reactor was not evaluated since it was received after the work was finished Corrosion of Stainless Steel Bombs. We rejected high quality stainless steel bombs as test containers because of their extremely poor resistance to attack by NaCl. The steel, #316, is molybdenum doped which improves its resistance to chloride attack. In a sodium chloride solution at both 130 and C for four days the steel bomb was deeply corroded and the test solutions discolored. Figure 5 shows a photograph of the tops of the two bombs after they had been "cleaned" by sand blasting compared with an unused bomb.

15 March 1, (Sundquist, J.D..) B Figure 5. Photograph of High Quality Stainless Steel (316) Containers After Exposure to an Aqueous NaCl Solution for Short Periods of Time. A» Blank, B C/ days, C = C/ days Incidentally, Code 9617 glass-ceramic by comparison is hardly touched! Corrosion of Code 770 Glass Tubes. Chemically resistant CGW glass Code 770 test tubes were used in the constant temperature baths at temperatures less than 100 C. Code 770 glass corrosion rate in water is 0.15 cm/1000 year (Y), However, because of the relatively large surface area of the test tube compared to the test specimen (ranging from 100/1 to 50/1) the blank contribution by the tubes becomes significant. Because of this high blank it is recommended that plastic tubes be used for small samples. 5.2 Analytical Tools Several analytical techniques were evaluated including weight loss, flame spectrometric analysis, microscopy and hydrogen ion profiling.

16 March 1, iy/ö Weight loss has the advantages of ease and speed as well as the availability of much historical data on other materials that can be used as references. It has the disadvantage of requiring a major disruption of a test when interim data is required as the test proceeds. This disruption is not only inconvenient but will affect the results since it introduces a sample cooling and drying step before weighing. A better method for monitoring tests as they progress is the flame spectrometric analysis of test solution aliquots. This can be done with less disturbance, especially if the solution volume is large (> 100 ml) and the test is not being run in high temperature bombs. Disadvantages include the possibility that all the products of corrosion might not be in solution, the decrease in solution volume or the change in solution chemistry if the removed volume is replaced with fresh water, the fact that the use of the bombs requires the cooling of the test solution before an aliquot can be removed and the fact that the bombs are of a small volume (22 ml). The effect of these drawbacks can be lessened with the use of the 300 ml mini-reactor which we purchased. removal of solution in situ. This bomb permits the addition and Scanning and transmission electron microscopy are useful in visually assessing surface effects. A technique for H + profiling of the surface of materials 2 to a depth of a few micrometers has also been used. A linear accelerator produces N atoms which collide with hydrogen in the sample to yield gamma rays in proportion to the concentration of hydrogen present. the energy of the glass-ceramic surfaces.. Depth of analysis is changed by changing N. This method was used to profile reacted The technique is also capable of

17 March 1, providing other ion profiles such as lithium which is present in the glass-ceramic composition. It is not yet clear whether this method can be used to predict corrosion rates. 5.3 Experimental Variables Experimental variables studied include the ratio (R) of the test solution volume to test sample surface area (ml/cm*), ph, time, temperature, and the effects of the sand plus bentonite mix, and sodium chlcride. Ground water composition effects were nut evaluated initially since we preferred to study the principal variables in a simple matrix - pure water. Once these were understood we planned Go introduce ground water as an effect. We used very small sample sizes (0.5 to 2 cm?) in order to fit them into the small bombs. This small sample size introduces two additional variables, neither of which we have evaluated. They are the error in determining the geometric area of small samples and the "edge effect". With large samples (> 5 cm 2 ) this effect is negligible but becomes more important as one uses sample sizes in the regime in which we have. The corrosion rate at the sharp edges of a material is accelerated over that rate for a flat surface. The smaller the sample size, the greater the proportion of edge length to total surface area and the greater this effect. This relationship for various shapes of rectangles is plotted in Figure Preliminary Rate Prediction This section presents our comments and conclusions regarding various aspects of the data. None of the conclusions and predictions have been supported with replicate experiments. The corrosion rates were calculated assuming linear attack (etch).

18 March 16, u «OUR WORKING RANGE (1.5) NORMAL WORKING RANGE (0.01) SURFACE AREA (cm 6 ) Figure 6. increased Importance of Edge Effect with Lower Surface Area Samples. Rate of Change of Ratio in Parentheses This is probably not the case, but it provides a high estimate. 6.1 Ratio Efiect The first variable studied in detail was the effect of test solution volume to sample surface area (R). This is an important consideration since R affects the rate of change of solution chemistry with time. An example of this effect is shown in Figure 7. Here, corrosion rate in cm/1000 years is plotted versus time at 8 C for two values of R. Apparently, the lower ratio test solution becomes saturated with corrosion products at a faster rate than the higher one and reduces the rate of attack by the solution.

19 - March 1, r T t C 60 o oo 1 >s. R * M03 O 1 n *****--*«^^_^ Rs 0. 9 i i i TEST TIME (HOURS) 1 00 Figure 7. The Effect of the Ratio of Test Solution Volume to Sample Surface Area (ml/cm*) on Corrosion Rate for the Code 9617 Glass- Ceramic Since the proposed system is nearly static (a key assumption from the calculated rate of change of solution which was ~ 1 ml/cm* of glass-ceramic/year) we need to determine the saturated solution corrosion rate to predict the long term corrosion. One can determine this equilibrium corrosion rate by extending the time of experimentation to the point where the corrosion rate becomes constant. To assure that this holds true for any ratio the experiment should be done for more than one starting ratio. Also, if the experimental time becomes prohibitive one can extrapolate a family of curves to a point where they coincide. This is shown graphically in Figure 8.

20 March 1, 1978 (Sundquist, J. D.) -16- T» C K S M w o X long term equilibrium ratio Ö TEST TIME equilibrium corrosion rate TIME Figure 8. Predicting Equilibrium Long-Term Corrosion Rate and Ratio This should then be dune for several different temperatures so that one could extrapolate to the actual test site temperature range. After having gathered some data in this manner, it has become apparent that the use of high temperature tests creates many problems. Control of the experiment is difficult and we have indications that there is a change in the corrosion mechanism at the higher temperatures that prevents a straight forward extrapolation to the lower temperatures. (This change is discussed later in this report.) Rather than accelerating the corrosion of the materials and extrapolating down to actual conditions to obtain the long term corrosion rate, I feel that the best approach in the future

21 March 1, would be to take corrosion data under conditions very close to those predicted for the repository site. By using a low enough solution volume to surface area ratio, we would probably approach the equilibrium quite rapidly even at the lower temperatures of 60 and C. 6.2 Corrosion Rate Estimates Based on data so far obtained I have calculated the ceramic and frit water corrosion rate as a function of temperature and ratio: Sample R Test Corrosion Rate Temperature( C) (cm/1000 Y^ 78 Glass-ceramic Time (days) Frit Table 2. Estimated Corrosion Rate of the Code 9617 Glass- Ceramic and Experimental Sealing Frit. NOTE: That as the ratio is lowered the corrosion rate drops.

22 March 1, 1978 Extrapolation of these data back to a zero ratio should give an estimate of the equilbrium (long term) corrosion rate under static conditions. In Figure. 9 below I have done this for the data in Table 2, The glass-ceramic C data are not linear. This may be a change in glass corrosion mechanism or an error in the data. Glass-Ceramic C I Glass-Ceramic C 10 RATIO Figure 9. Corrosion Rate as a Function of the Ratio of Solution Volume to Surface Area. Zero Ratio is Equivalent to Corrosion Over the Lone Term.

23 March 1, The predicted long term corrosion rates from this extrapolation are shown below in Table 3. Material T C O Corrosion Rate (cm/1000 Y) Glass-Ceramic 8 to Frit 2 Table 3 Predicted Long Term Corrosion Rates from the Extrapolation of Data to a Zero Ratio. Figure 10 shows the glass.-ceramic corrosion rate plotted as a function of temperature for ratios of 0 (obtained by extrapolation), 5, 10, and 20 ml/cm*. The zero ratio curve represents our best guess for the long term corrosion rate. To obtain an accurate predict:ion of actual total corrosion we need to consider the effects of cooling. Using the cooling curve shown earlier in Figure 2, the following calculations can be made: Average Temperature ( C) Total Time Interval (yrs) Rate (cm/1000 Y) R " 20 R < < Material Removed (cm) R = 20 R = < p_._003 < CK Table. Estimated Glass-Ceramic Taking Into Account the cooling of the repository Site. Sample is Assumed Wet at Time of Deposit.

24 SO n> rt H> O M» O»1 09 C 1 ro CORROSION RATE (cm/1000 y) o n 1 o I» o 3 o o o o o c ^ 3 O Q. 3- J3 w - rt» 00 rt zr ro o i-» to w W 1 Oro i» a o 50 n> rt ro p> w» o> o rt lon o H ro a o ro 1 t» c t n i» a CL H W w JO5.TUR td O in o i-» o o» o (o O O IS) o

25 March 1, These estimated rates are well within the limit of 1 cm/1000 years that we were targeting. Note that if it is taken into account t.har the repository void space is not filled with watt, until 200 years these estimates are high. 6.3 The Effect of Sand and Bentonite The preliminary data on.the effect of sand and bentonite on corrosion are shown below: Material Frit Glass-ceramic Glass-ceramic Test Matrix 9 sand/1 bentonite/h 2 0 c 9 sand/1 bentonite/h sand/1 bentonite/h 2 0^ 9 sand/1 bentonite/h 2 0 H 2 0 R ~ 2 Temperature C 60 ~ 60 Estimated Corrosion Rate cm/1000 Y k ~ 0.01 b Table 6. Preliminary Corrosion Estimates on the Effect of the Sand Bentonite Mix c Compared to Pure Water from Figure 9; from Figure 10; C 9 grams sand + 1 gram bentonite made up to volume with H 2 0 These values indicate the corrosion in the mix to be within accepted limits considering that the data are for ratios higher than the expected equilibrium ratio of zero.

26 March 1, The Effect of Solution Flow The rate of influx of ground water is estimated to be about 1 milliliter per centimeter of glass-ceramic per year. This low rate was considered insignificant in its effect on the chemistry of the system and was not investigated. 6.5 The Effect of the Composition of the Ground Water work. This was to be studied later in the course of our 6.6 Sodium Chloride Corrosion A small amount of data was obtained on corrosion by aqueous salt'solution (0.5 gms/ml). Some of the data was confounded by corrosion of the stainless steel test containers. In these instances, the glass-ceramic showed little corrosion relative to the steel. Table 6 shows the corrosion rate estimates for aqueous salt attack on the frit and the glass-ceramic. Material Glass-Ceramic Solution NaCl H 2 O R Time (Hours) Temperature C Corrosion R. cm/ NaCl H 2 O NaCl H A 1.8 Frit NaCl H NaCl H.O Table 6. Preliminary Data on the Corrosion Rate of NaCl Solution Compared to H2O for the Glass-Ceramic and the Frit. These corrosion rates seem to be comparable to water corrosion rates.

27 March 1, Corrosion Mechanism We have evaluated the corrosion mechanism on a macro and an atomic scale. 7.1 Selective Attack The next two sections address these topics The Code 9617 glass-ceramic is a composite of several phases as shown below: 0-spodunene (Li 2 O-Al 2 O 3 -x SiO 2 ) ( x - 5 to 7) ~ 7. rutile (TiO 2 ) - 3 spinel (Mg or Zn*Al 2 O ) ~ 3 residual glass (high Zn)* ~ 5 determined by scanning transmission electron energy dispersion. Because of this, one would expect the composite material to exhibit different localized corrosion rates. This appears to be the case. Scanning electron microscopy of the H 2 0 corroded glass-ceramic surface showed the glass phase to be removed leaving the crystalline phases relatively untouched. Figure 11. A B Scanning Electron Micrographs Comparing Water Attacked Surface (B) with Unattacked Surface (A). Attack was h Hours at e C in H 2 0

28 March 1, Figure 12 shows the remaining crystalline phases in greater detail. Figure 12. Higher Magnification Scanning Electron Micrograph of Glass-Ceramic Showing Only Crystals Remaining After Days at C in Water

29 March 1, This evidence coupled with the cloudiness of the solution suggests the mechanism of attack described below in Figure 13. TIME» 0 rutile & spinel TIME t T ORIGINAL SURFACE Figure 13. Suggested Corrosion Mechanism: Selective Leaching Away of Glassy Phase Followed by Dislodging of Unreacted Crystalline Phase. Improving the durability of this glassy phase should improve the overall glass-ceramic durability. This was demonstrated using an S0 2 treatment, a common method in the glass container industry to improve the durability of some glasses. Hot, wet S0 2 provides free H + ions which exchange with alkali at the surface of the glass. The surface then reconsolidates into a more durable high silica skin. At the temperature of treatment

30 March 15, (~ 550 C) the crystalling phases are probably not affected. Chemical durability results on some S0 2 treated samples is shown in the table below compared with untreated samples. Sample Time (Days) Temperature C Corrosion Rate (cm/1000 Y) Untreated S0 2 Treated Untreated SO 2 Treated Untreated SO» Treated U Table 7. The Effect of SO2 Treatment on Ceramic Durability, Glassy Phase Durability Is improved (R» 0.9) Though the improved durability only lasts until the silica-rich skin is removed the long range durability will be improved by holding off attack until the cannister and its surroundings have cooled to a condition of lesser corrosivity. The proposed corrosion mechanism presents other opportunities for improving chemical durability; 1, reduction of the amount of glassy phase 2. changing the composition of the glassy phase. It is worth noting that the spodumene phase appears to be highly durable in a water environment and efforts to improve ceramic durability should aim at increasing the amount of 0 spodumene. 7.2 Ion Exchange Hydrogen ion profiling of the reacted sample surface may aid in understanding the corrosion mechanism on an atomic scale.

31 March 1, Hydrogen and/or water migration into the surface of materials, especially glass and glass-ceramics, play a major role in the corrosion process. Until recently, there has been no method available for profiling this reacted surface. work by Dr. William Lanford at Yale University has provided Recent us with a method for determining hydrogen ion profiles in glass and glass-ceramics. The generally agreed upon model for H 2 0 corrosion of glass is shown schematically in Figure 1. In: Step 1: H ions replace free alkali ions in the glass by ion exchange (leaching) Step 2: The presence of the alklai ions in the water raises its ph and the resulting hydroxyl groups attack the Si-O-Si network breaking the Si-0 to form Si-OH (etching). Lanford f s work suggests that hydronium ions not hydrogen ions (H + ), are the exchanging species, (in Step 1). Figure 15 shows a typical H + profile and how it relates to the glass (or glass-ceramic) surface.

32 March 1, 1978 (Sundquist, J. D.) LEACH (STEP 1) Figure 1. Corrosion Mechanism on An Atomic Level

33 March 1, DEPTH ALL Li EXCHANGED ETCH GEL EXCHANGE BULK Figure 15. Typical Hydrogen Ion Profile by It Relates to the Sample 15 N and How The horizontal line in the figure labelled "All Li Exchanged" corresponds to the point where the H ion concentration is three times the concentration of the Li ions in the bulk ceramic as calcuated from the composition. That is, we assume that one H 3 0 ion exchanges for one Li ion. The hydrogen ions in excess of this value are assumed to correspond to bulk water that saturates the ion exchanged silica skin. This is called the hydrated gel layer. The depth of exchange below the gel/bulk interface is called the exchanged layer.

34 March 1, From H profiles measured by Lanford and weight loss data we have computed the thickness of the etch, gel and ionexchanged layers for several test conditions: Time (hours) Test Conditions Temperature ( C) Etch Gel lon-exchanpe (?) (?) (?) Table 8. Some Preliminary Calculations of Etch, Gel and Ion- Exchange Layers from Weight Loss and Hydrogen Ion Profile Data (R - 0.9) The sharp increase in the thickness of the gel and ion-exchange layer at 08 hours -"C is suggestive of a mechanism change. More work is necessary to fully understand this. 8. Conclusions The first objective, learning how to best do experiments for long term prediction under the specified conditions has been achieved. Some tentative conclusions can be drawn from the data regarding the second objective-predicting the extent of corrosion over a 1000 year span. Information has also been obtained regarding other chemical environments such as an aqueous salt system and modifications to the storage site and/or the cannister

35 March 1, material to prolong the storage life. The optimum test conditions would embrace the actual time, temperature, chemistry and flow conditions to be found at the repository site. Since this cannot be done, it is preferable to conduct the tests at test site temperatures and extrapolate to the longer times required for prediction. Mechanism changes seem to occur when increased temperature is used and this could invalidate conclusions. However, a few tests at elevated temperatures might be used to rapidly identify possible "worst case" situations. Such worst case situations should then be validated under expected site temperatures. Extreme care must be taken in the design and interpretation of experiments to assure that the chemistry simulation is accurate, and/or that deviations are understood and accounted for. not enough. Simply duplicating the initial chemistry of the system is This is particularly true in a situation that is expected to be "static" regarding ground water movement. If further work is to be done in the system described in this report, the following is recommended: 1. Temperature - 30, 60,, and 120 C 2. Time - as long as practical 3. Initial solution - ground water in equilibrium with 9 sand and 1 bentonite. Solution volume to sample surface area ratio - very high, very low 5. Determine - Weight loss, ions in solution (Si, Li, etc.) - Electron micrographs of surface and cross-section - Hydrogen and possibly lithium ion profiles. Composite "sandwiches" of the ceratiic-frit-ceramic body should be tested as well as small samples from an actual cannister.

36 March 1, (Sundquist, J. D.) The data obtained at this point indicate that the ceramic would be reduced in thickness by about 0.1 cm in 1000 years under the specified conditions. The experimental frit candidate tested would apparently be corroded to a depth of about 1 cm in 1000 years. The corrosion rates in cm/1000 years for the glass-ceramic are estimated in Figure 10 (zero ratio «static condition). Typically, rates in flowing conditions are 2 cm/1000 Y at 100 C, 0.1 at 50 C; in static conditions, 0.2 cm/1000 Y at 100 C and at 50 C. Corrosion rates in aqueous salt systems do not appear to differ dramatically from those found in water; if anything they appear,to be lower. In limited testing we found a static corrosion rate of about 0.1 cm/1000 Y. These data may have been affected by the stainless steel corrosion products from the test container. The strong dependency of the corrosion rate '6n the ratio" of solution volume to sample surface area in actuality represents the effect of different concentrations of dissolved ions, probably silicon and aluminum complexes. This suggests that any potential corrosion of a cannister stored in a water cooled basin could be decreased by appropriate chemical additions to that water. The /3-spodumene crystal fraction of the glass-ceramic seems to be extremely corrosion resistant to near neutral (ph ~ 7) solutions. The glassy phase is apparently the less durable fraction. It is probable that more resistant glass-ceramics could be designed by either adjusting the composition or the ceramming process.

37 March 1, Any further studies should include the evaluation of the effects of radiation damage on corrosion, the possibility of crystal growth and resultant fracture in the fritted seal joint and the change in physical strength as corrosion proceeds. Two major concerns emerge: 1. the limited results on water in contact with bentonite and sand suggest that the rate of corrosion could be different than for water, and 2. the H profile results suggest that, long term, there could be a mechanism change to accelerate the corrosion process. Finally, note that the bulk of these conclusions regarding corrosion rates and mechanisms rests on limited data and should be further studied.

38 March 1, References Private Communication from L. Hyden to J. D. Sundquist, July/77. 2 W. A. Lanford, 15 N Hydrogen Profiling, Scientific Applications" Presented at 3rd Int. Cont. on Ion Beam Analysis, Washington, D. C. June 27 - July 01, USERDA Contract No. EY-76-C ACKNOWLEDGMENT I would like to thank Mr. Russell LaFever for doing most of this work and keeping a good record of all of it. Dr, R. A. Burdo and Messrs. Thresher and Robinson provided many timely analyses without which this report could not be. Mrs. E. L. Cross did an excellent job of organizing the tables of data and typing the report. elc 3/15/78

39 March (Sundqulnt, J.D.) APPHND1X I. CLASS CERAMIC CODE 9617 Corrosion Test lint» Ref It 9ft * Vest Description II,O 11,0/9 sand/1 bentontt* (3 RnMi) II,O 11,0 II,O II,O II,O tlio lit O II»O HlO 11,0 II,O II,O change 11,0 once/veek change 11,0 once/week ll,o/9 SIO,/I bentonlte (5 gms) 11,0/9 StO,/I bentonlte (10 gm») HjO/9 SIO,/I bentonlte (5 *ms) M,0/N.iCI(0.5 Buffered'( >lt-8.5) RuFfcreO 2 (.ll-b.6) Buffereil'(pH-8.5) Buffered? (pm=«.6) Ratio (ml/cm») Time (Day») U A I* Temperature CO Flnnl pil 7.7 B ft. 8.3 ft.fi Wt. Loss (mg/cm») «8 $ /. <0.0« <0.0l < < <0.0l <0.0l <0.0l n.nm Extracted Solution )my./cro«) StO, Al.Oi Lt,0 ZIIO < <0.02 < < detailed In Appendix 3 (MytlroKy-methyl) umlno ncthanetllcl BornteillCl Note: no data excluded although some may be spurious.

40 March (3umln<»l»t. J.O.) APPr. X I - continued - Page 2. «ef.?2 8 so 52 5* » J IO2 It 9 ' US % ,0 II,O II,O II,O 11,0 Teat Description lt,0/imcl(0.5 K"M/«>> n»ff»r»<j l (pll-8.5) 1,0 <glaaa-cerainlc SO, treated) n, o' II,O II,O II,O II,O H,0 H,0 3 11,0 K,0 M,0 II,O 11,0 11,0 11,0 11,0 n,o HtO M,O experimental glas«>e*raialc/h,0 " experimental Rlns!»-c«ri»mlc/H,0 experimental glasa-ceramle/mjo experimental gla«a-ceramlc/ll,0 H,0/KiCl(6»«««/"il)' ll,0/n.ici<6 RHM/»II)' ll,0/».ici<ft RiM/ml) 3 lt,o/n»cl(6 Rms/ml) 3 H t 0/tilinn-c*Tmii\c (flo'. continue!) -SO, treated II.0 (rl.tn-fotamlc SOi trrntrh) ".atlo (»l/cm») U II * ] 20 II ,9 n.9 Time (day») t, /6 1 1/ /6 6 1 t Temperature CO 130 no UO IJO mo 'JO mo ino in») inn tnn ino mo Final PH M J f> fl.*» Wt. I.OS < o.oi ,5» 0.10 O.M?..2 J , J K7 0. I0 J 0.<ift 3 O.S » o.on 0.C2 o.on sto, * * 'We some Extracted Solution (««/cn>) M.o. _ llio JWL. ZnU < A O0O } » : no data excluded may be spurious , OO althc

41 March 1, 1978 (Sundquist, J.U.) Kef H 2 0 a APPENDIX II Experimental Frit Glass Code 186AYU. Corrosion Test Description 0 H 2 0 change solution (10 gms) once/wk H 2 0/sand/bentonite (10 gms) H 2 0/NaCl H 2 0/NaCl Ratio ' Time (davs) 63 1/6 1-1/6 16 1/6 1-1/6 1/6 1-1/6 70 1/6 16 Temperature Test Final ii Data Wt Los (-ng/cn 0.19* Ö Solution extraction < 0.03 mg/cm* PbO Ndte: no data excluded although some may be spurious

42 March 1, 1978 APPENDIX III-A -H : 0 Solution Analysis for Glass-Ceramic (fresh water once a week) Ref R Tine (Weeks) APPENDIX 1II-B -HjO ii: tic 3/17/ S Temoerature rc) 130 Solution ianalysis fot Frit (fresh water SIP» PbO 1.3 < < < < SiO, Al,0, < ms./cm> < < < < < < < < < < ! Li.O a Note: no data excluded although may be spurious. MgO once a 1some ZnO < < < week)

43 March 1, 1978 APPENDIX IV - Compositions A. Water Solution After Contact with 9 Sand & 1 Bentonite Mix a (1 gram/20 ml) Conditions Time (days') Temperature ( C) SiO, Concentration in Solution (ppm) A1,O, Li?0 MgO Na,0 ZnO

44 FÖRTECKNING ÖVER KBS TEKNISKA RAPPORTER 01 Källstyrkor i utbränt bränsle och hög.iktivt avfall fr.'in i>n TWR beräknade med 0R1GLN Nils Kjellbert AB Atomenergi I'M angående värmeledningstal hos jordmaterial Sven Knutsson Roland Pusch Högskolan i Luleå Deponering av högaktivt avfall i borrhål med buffertsubstans Arvid Jacobsson Roland Pusch Högskolan i Luleå Deponering av högaktivt avfall i tunnlar med buffertsubst.ins Arvid Jacobsson Roland Pusch Högskolan i Luleå Orienterande temperaturberäkningar för slutförvaring i berg av radieaktivt avfall, Rapport 1 Roland Blomqvist AB Atomenergi Croumlwater movements around a repository, Phase 1, State of the art and detailed study plan Ulf lindblom Hngronsult AB Resteffekt studier för KBS Del 1 Litteraturgenomgång * Del 2 Beräkningar Kim l.kborg Nils Kjc-1 lbert Göran Olsson AB Atomenergi l't läkning av franskt, engelskt och kanadensiskt glas med liiig.ikt i vt avfal 1 Göran Blmnqvist AB Atcincnergi

45 09 Diffusion of soluble materials in a fluid filling a porous medium Hans Häggblom AB Atomenergi Translation and development of the BNWL-Ceosphere Model Bertil Crundfelt Kemakta Konsult AB Utredning rörande titans lämplighet som korrosionshärdig kapsling för kärnbränsleavfall Sture Henriksson AB Atomenergi Bedömning av egenskaper och funktion hos betong i samband med slutlig förvaring av kärnbränsleavfall i berg Sven G Bergström Göran Fagerlund Lars Rombén Cement- och Betonginstitutet Ur läkning av använt kärnbränsle (bestrålad uranoxid) vid di rektdeponering Ragnar Gel in AB Atomenergi Influence of cementation on the deformation properties of bentonite/quartz buffer substance Roland Pusch Högskolan i Luleå Orienterande temperaturberäkningar för slutförvaring i berg av radioaktivt avfall ' Rapport 2 Roland Blomquist AB Atomenergi Översikt av utländska riskanalyser samt planer och projekt rörande slutförvaring Åke Hultgren AB Atomenergi augusti The gravity field in Fennoscandia and postglacial crustal movements Ai tie Bjerli.immar Stockholm augusti Rörelser och instabilitet i den svenska berggrunden Ni Is-Axel Mörner Stockholms Universitet augusti St tid i er av rw-otektoni sk aktivitet i mellersta och norra Svrrif/N f1 y^,bi lds^f nomj;ång och geofysisk tolkning av rrrent.1 f iirknsl ni ng.ir Robert l.aj',«-i"»äck Herbert Hi'iikel Sveriges Geologiska Undersökning september 1977

46 20 Tekionisk analys av södra Sverige, Vättern - Norra Skåne Kemier t Röshoff Erik Lagerlund Lunds Universitet och Högskolan Luleå september Earthquakes of Sweden , Ota Kulhänek Rutger Wahlström Uppsala Universitet september The influence of rock movement on the stress/strain situation in tunnels or bore holes with radioactive consisters embedded in a bentonite/quartz buffer mass Roland Pusch Högskolan i Luleå W.iter uptake in a bentonite buffer mass A model study Roland Pusch Högskolan i Luleå Beräkning av utlakning av vissa fissionsprodukter och aktinider från en cylinder av franskt glas Göran Blomqvist AB Atomenergi Blekinge kustgnejs, Geologi och hydrogeologi Ingemar Larsson KTH Tom Lundgren SG1 Ulf Wikl änder SGU Storkholm, augusti Bedömning av risken för fördröjt brott i titan Kjell Pettersson AB Atomenergi A short review of the formation, stability and cementing properties of natural zeolites Arvid Jacobsson Högskolan i Luleå Värmeledningsförsök på buffertsubstans av bentonit/pitesi11 Sven Kmitsson Högskolan i Luleå Deformationer i sprickigt berg Ove Stephansson Högskolan i Luleå Rot.lid.il ion of escaping iniclides from a final depository Iv.irs Neretnieks Kungliga Tekniska Högskolan Stockholm I5fclö:;ining nv kurrosionsbeständighpten hos material avsedda for k.ipsling av kärnbränsleavfall. Lägesrapport s.rnt kompletterande yttranden. KiMTosiiMisinstitutet och dess referensgrupp

47 32 Long term mineralogii.il properties of bentonite/quartz buffer substance Preliminär rapport november 1977 Slutrapport februari 1978 Roland Pusch Arvid Jacobsson Högskolan i Luleå 33 Required physical and mechanical properties of buffer masses Roland Pusch Högskolan Luleå Tillverkning av bly-titan kapsel Folke Sandelin AB VBB ASKA-Kabel Institutet för metal 1 forskning Stockholm november Project for the handling and storage of vitrified high-level waste Saint Cobain Techniques Nouvelles October, Sammansättning av grundvatten på större djup i granitisk berggrund Jan Remier fel t Orrje & Co, Stockholm Hantering av buffertmaterial av bentonit och kvarts Hans F.igerström, VBB Björn Lundahl, Stabilator Stockholm oktober Utformning av bergrutnsanläggningar Arne Finne, KBS Alf Engelbrektson, VBB Stockholm december Konstruktionsstudier, direktdeponering ASKA-ATOM VBB Väst eras 0 Ekologisk iransport och stråldoser frän grundvattenburna radioaktiva ämnen Ronny Bergman Ulla Bergström Sverker Evans AB Atomenergi 1 Säkerhet och strålskydd inom kärnkraftområdet. Lagar, normer och bedömningsgrunder Clir i st i na Gyl lander Siegfried F Johnson Stig Rolindson AB Atomenergi och ASEA-ATOM

48 2 Säkerhet vid hantering, lagring och transport av använt kärnbränsle och förglasat högaktivt avfall Ann Margret Ericsson Kemakta november Transport av radioaktiva ämnen ned grundvatten frän ett bergförvar Bertil Grundfelt Kemakta november 1977 Beständighet hos borsilikatglas Tibor Lakatos Clasteknisk Utveckling AB 5 Beräkning av temperaturer i ett envanings slutförvar i berg för förglasat : adioaktivt avfall Rapport 3 Roland Blomquist AB Atomenergi Temperaturberäkningar för använt bränsle Taivo Tarandi VBB 7 Teoretiska studier av grundvattenrörelser Preliminär rapport oktober 1977 Slutrapport februari 1978 Lars Y Nilsson John Stokes Roger Thunvik Inst för kulturteknik KTH 8 The mechanical properties of the rocks in Stripa, Kråkemåla, Finnsjön and Blekinge Graham Swan Högskolan i Luleå Bergspänningsmätningar i Stripa gruva Hans Carlsson Högskolan i Luleå l.akningsförsök med högaktivt franskt glas i Studsvik Göran Blomqvist AB Atomenergi november Seismotechtonic risk modelling for nuclear waste disposal in the Swedish bedrock F Ringdal H Gjöystdal E S Hysebye Royal Norwegian Council for scientific and industrial research 52 Calculations of nuclide migration in rock and porous media, penetrated by water H Häfcjgblom AB Atomenergi

49 53 Mätning av diffusionshastighet för silver i lera-sand-blandning Bert Al lärd Heino Kipatsi Chalmers tekniska högskola Groundwater movements around a repository 5:01 Geological and geotechnical conditions Håkan Stille Anthony Burgess Ulf E Lindblom Hagconsult AB september :02 Thermal analyses Part 1 Conduction heat transfer Part 2 Advective heat transfer Joe L Ratigan Hagconsult AB september :03 Regional groundwater flow analyses Part 1 Initial conditions Part 2 Long term residual conditions Anthony Burgess Hagconsult AB oktober :0 Rock mechanics analyses Joe L Ratigan Hagconsult AB september :05 Repository domain groundwater flow analyses Part 1 Permeability perturbations Part 2 Inflow to repository Part 3 Thermally induced flow Joe L Ratigan Anthony S Burgess Edward L Skiba Robin Charlwood 5:06 Final report Ulf Lindblom et al Hagconsult AB oktober Sorption av långlivade radionuklider i lera och berg Del 1 Bestämning av fördelningskoefficienter Del 2 Litteraturgenomgång Bert Allard Heino Kipatsi.1an Rydberg Chalmers tekniska högskola Radiolys av utfyllnadsmaterial Bert Al lärd Hrino Kipatsi.lan Rydberg Chalmers tkniska högskola

50 57 Stråldoser vid haveri under sjötransport av kärnbränsle Anders Appelgren Ulla Bergström Lennart Devell AB Atomenergi Strålrisker och högsta tillåtliga stråldoser för människan Gunnar Walinder FOA november Tectonic lineaments in the Baltic from Gävle to Simrishamn Tom Floden Stockholms Universitet Förarbeten för platsval, berggrundsundersökningar Sören Scherman Berggrundvattenförhållande i Finnsjöområdets nordöstra del Carl-Erik Klockars Ove Persson Sveriges Geologiska Undersökning januari Penneabilitetsbestämningar Anders Hult Gunnar Gidlund Ulf Thoregren Geofysisk borrhålsmätning Kurt-Åke Magnusson Oscar Duran Sveriges Geologiska Undersökning januari Analyser och åldersbestämningar av grundvatten på stora djup Gunnar Gidlund Sveriges Geologiska Undersökning Geologisk och hydrogeologisk grunddokumentation av Stripa försöksstation Andrei Olkiewicz Kenth Hansson Karl-Erik Almén Gunnar Gidlund Sveriges Geologiska Undersökning februari Spänningsmätningar i Skandinavisk berggrund - förutsättningar, resultat och tolkning Sten G A Bergman Stockholm november Säkerhetsanalys av inkapslingsprocesser Göran Carleson AB Atomenergi Nfigra synpunkter på mekanisk säkerhet hos kapsel för kärnbränsleavfall Fred Nilsson Kungl Tekniska Högskolan Stockholm februari 1978

51 67 Mätning av galvanisk korrosion mellan titan och bly samt mätning av titans korrosionspotential under ~jf- bestrålning. 3 st tekniska PM. Sture Henrikson Stefan Poturaj Maths Åsberg Derek Lewis AB Atomenergi januari-februari Degraderingsmekanismer vid bassänglagring och hantering av utbränt kraftreaktorbränsle Gunnar Vesterlund Torsten Olsson ASEA-ATOM A three-dimensional method for calculating the hydraulic gradient in porous and cracked media Hans Häggblom AB Atomenergi Läkning av bestrålat U0--bränsle Ulla-Britt Eklund Ronald Forsyth AB Atomenergi Bergspricktätning med bentonit Roland Pusch Högskolan i Luleå Värmeledningsförsök på buffertsubstans av kompakterad bentonit Sven Knutsson Högskolan i Luleå Self-injection of highly compacted bentonite into rock joints Roland Pusch Högskolan i Luleå Highly compacted Na bentonite as buffer substance Roland Pusch Högskolan i Luleå Small-scale bentonite injection test on rock Roland Pusch Högskolan i Luleå Experimental determination of the stress/strain situation in a sheared tunnel model with canister Roland Pusch Högskolan i Luleå Nuklidvandring från ett bergförvar för utbränt bränsle Bert i 1 Grundfel t Kemakta konsult AB, Stockholm 78 Bedömning av radiolys i grundvatten Hilbert Christenssen AB Atomenergi

52 79 Transport of oxidants and radionuclides through a clay barrier Ivars Neretnieks Kungl Tekniska Högskolan Stockholm Utdiffusion av svarlösliga nuklider ur kapsel efter kapselgenombrott Kavin Andersson Ivars Neretnieks Kungl Tekniska Högskolan Stockholm Tillverkning av kopparkapsel Kåre Hannerz Stefan Sehlstedt Bengt Lönnerberg Liberth Karlson Gunnar Nilsson ASEA, ASEA-ATOM 82 Hantering och slutförvaring av aktiva metalldelar Bengt Lönnerberg Alf Engelbrektsson Ivars Neretnieks ASEA-ATOM, VBB, KTH 83 Hantering av kapslar med använt bränsle i slutförvaret Alf Engelbrektsson VBB Stockholm april Tillverkning och hantering av bentonitblock Alf Engelbrektsson Ulf Odebo ASEA, VBB 85 Beräkning av kryphastigheten ho # s ett blyhölje innehållande en glaskropp under inverkan av tyngdkraften Anders Samuelsson Förändring av krypegenskaperna hos ett blyhölje som följd av en mekanisk skada Göran Eklund Institutet för Metal 1 forskning september april Diffusivitetsmätningar av metan och väte i våt lera Ivars Neretnieks Christina Skagius Kungl Tekniska Högskolan Stockholm Diffusivitptsmätningar i våt lera Na-lignosulfonat, Sr 2+, Cs* Ivars Neretnieks Christina Skagius Kungl Tekniska Högskolan Storkholm Ground water chemistry at depth in granites and gneisses Gunnar Jacks Kungl Tekniska Högskolan Stockholm april 1978