Pore Solution Chemistry of Simulated Low-Level Liquid Waste. Incorporated in Cement Grouts

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1 RCVD WHC-SA-295-FP JAN OsTf Pore Solution Chemistry of Simulated Low-Level Liquid Waste. norporated in Cement Grouts DSCLAMR Thii report was prepared as an aount of work sponsored by an ageny of the United States Government. Neither the United States Government nor any ageny thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the auray, ompleteness, or usefulness of any information, apparatus, produt, or proess dislosed, or represents that its use would not infringe privately owned rights. Referene herein to any speifi ommerial produt, proess, or servie by trade name, trademark, manufaturer, or otherwise does not neessarily onstitute or imply its endorsement, reommendation, or favoring by the United States Government or any ageny thereof. The views and opinions of authors expressed herein do not neessarily state or reflet those of the United States Government or any ageny thereof. ~-~ ~ ~- Prepared for the U.S. Department of nergy Off ie of nvironmental Restoration and Waste Management Westinghouse Hanford Company Rihland, Washington Hanford Operations and ngineering Contrator for the U.S. Department of nergy under Contrat D-AC6-87RL193 Copyright Liense By aeptane of this anide, the publisher endlor reipient aknowledges the U.S. Government's right to retain a nonexlusive, royalty-free liensein and to any opyright overing this paper. ' Approved for Publi Release

2 WHC-SA-295-FP Pore Solution Chemistry of Simulated Low-Level Liquid Waste norporated in Cement Grouts v A. A. Kruger Date Published Deember 1995 Presented at 1995 Fall Meeting of the Materials Researh Soiety Boston, Massahusetts November 27-Deember 1, 1995 Prepared for the U.S. Department of nergy Off ie of nvironmental Restoration and Waste Management Westinghouse Hanford Company P. Box 197 Rihland, Washington Hanford Operations and ngineering Contrator for the U.S. Department of nergy under Contrat D-AC6-87RL193 Copyright Liense By aeptane of thi m k l e, the publisher andlor reipient aknowledges the U.S. Government's tight to retain a nonexlusive, roydtyfree liense in and to any opyright overing this paper. Approved for Publi Release

3 LGAL DSCLAMR This report was prepared as an aount of work sponsored by an ageny of the United States Government. Neither the United Stetes Government nor any ageny thereof, nor eny of their employees, nor any of their ontrators, subontrators or their employees, makes any warranty, express or implied, or assumes any legal liebility or responsibility for the auray, ompleteness, or any third party's use or the results of dh use of any information, apparatus, produt, or proess dislosed, or represents that its use would not infringe privately owned rights. Referene herein to any speifi ommerial produt, proess, or senn'e by trade name, trademark, manufaturer, or otherwise, does not neessarily onstitute or imply its endorsement, reommendation, or favoring by the United States Government or any ageny thereof or its ontrators or subontrators. The views and opinions of authors expressed herein do not neessarily state or reflet those of the United States Government or any ageny thereof. This report has been reprodued from the best available opy. Printed in the United States of Ameria DSCLM-2.CHP 11-91)

4 POR SOLUTON CHMSTRY OF SMULATD LOW LVL LQUD WAST NCORPORATD CMNT GROUTS Sadananda Sahu and Sidney Diamond Shool of Civil ngineering, Purdue University, West Lafayette, N 4797 sahu@en. purdue.edu and diamond@en.purdue.edu ABSTRACT xpressed pore solutions from simulated low level liquid waste ement grouts ured at room temperature, 5 C and 9 C for various duration were analyzed by standard hemial methods and ion hromatography. The solid portions of the grouts were formulated with portland ement, fly ash, slag, and attapulgite lay in the ratios of 3:3:3:1. Two different solutions simulating off-gas ondensates expeted from vitrifiation of Hanford low level tank wastes were made. One is highly alkaline and ontains the speies Na', PO:-, NO;, NOd and OH'. The other is arbonated and ontains the speies Na', PO:, NO;, NO;, and CO?-. n both ases phosphate rapidly disappeared from the pore solution, leaving behind sodium in the form of hydroxide. The arbonates were also removed from the pore solution to form alium arbonate and possibly alium monoarboaluminate. These reations resulted in the inrease of hydroxide ion onentration in the early period. Subsequently there was a signifiant redution OH- and Na' ion onentrations. n ontrast high onentration of NO; and Nod were retained in the pore solution indefinitely. NTRODUCTON Radioative waste management has drawn serious attention by the sientifi ommunity in reent times. t has been realized that there is a need to immobilize the radionulides as well as hazardous hemial speies before the final disposal. Blends of various ementitious materials onstitute a potential host matrix to immobilize most of the hemial speies [ Solidifiation of low level liquid waste in ementitious grouts has ertain inherent advantages over other methods. Hydrated produts may be formed by the partiipation of some of the waste hemial speies in the hydration proess; some speies may be absorbed in the several hydrated ompounds formed, and a signifiant amount of liquid ontaining soluble salts an be restrained and rendered somewhat immobile in the highly torturous porous network formed in the hardened grout. Traditionally the long term performane of ement waste forms are tested by examining their leahing behavior. This is sometimes misleading due to imperfet simulation of onditions that atually exist at the disposal site. Pore solution study, espeially at early ages, is an alternative supplementary method to help assess the long term performane of the grout, and the mobility of different waste speies in the system. n this study we have examined the behavior of a partiular ementitious blend ontaining attapulgite lay to the two different type of simulated off-gas waste ondensate solutions expeted to be generated during a proposed vitrifiation treatment proess to be applied to Hanford tank wastes.

5 XPRMNTAL The materials inorporated in the ementitious blend used in this study are a Type 1/11 portland ement (Ash Grove Cement Co., Durkee, OR), a Class F fly ash (Centralia, WA, purhased from Ross Sand and Gravel Co., Portland, OR), a granulated blast furnae slag ( Koh Minerals Co., Chiago, L), and attapulgite lay (ngelhard Co., selin, NJ). The hemial omposition of the materials, as provided by their respetive suppliers, are given Table. Table. Chemial omposition of the raw materials MnO LOT <o The solid blend used as the base of the grouts studied was blended in weight proportions of 3:3:3:1 respetively of ement, fly ash, slag, and attapulgite lay. The dry omponents were first mixed manually for a prolonged period by stirring and hrther homogenized in a rotary drum overnight. So-alled "Case 2" (alkaline) and ''Case 3" (arbonated) simulated off-gas solutions were prepared from the AR grade laboratory reagents at 45"C, in order to avoid preipitation of phosphate. The ioni onentrations of the simulated off-gas solutions are given in Table 11. "Case 1" solution, whih is aidi in nature and prone to produe gases during the grout hydration proess, has not been onsidered., The grouts were prepared at 45 C with a volume to weight, waste/solid ratio of 1, using a Hobart mixer at the lowest speed. The mixed slurry was poured into many repliate 1 plasti ointment jars and sealed in order to avoid any water loss due to evaporation. They were than allowed to reat isothermally at room temperature (22OC), 5 C or at 9 C. During the grouting proess a large amount of exothermi heat is generated due the reation of ementitious materials with the simulated waste solutions. Furthermore, in handling the real wastes an additional ontribution to heating is expeted from radiolyti heat generation [S, 61. Consequently it is expeted that the atual grouts will remain at elevated temperatures in the underground vaults for extended period of time. sothermal alorimetri study of similar grouts showed that the temperature may rise to as muh as 7 C with in 3 days and stabilizes at this temperature for an extended period (7). The present high-temperature exposures were employed to gain insight into the responses to be expeted under suh elevated temperature storage onditions.

6 Pore solutions from individual repliate speimens exposed at eah temperature were expressed at 12 hrs, and at 1, 3, 7, 28 and 9 days, aording to the proedure desribed previously [S. Table 11. oni Conentration of simulated off-gas solutions Case 2, mm 1 NO; NO; OH The pore Solutions were analyzed for the following ions: Na', K', NO;, NO;, SO:-, PO': and OH-. The ations were analyzed by atomi absorption spetrosopy and the anions (exept OH-) by ion hromatography.the OH- ion onentration was determined by titration with HC. RSULTS AND DSCUSSON The ioni onentrations of the pore fluids expressed from Case 2 and Case 3 waste forms at various ages up to 9 days at room temperature are presented in Figures 1 (a) and (b) respetively. A omparison of the results for the different ioni speies in the two ases show that similar trends are displayed in the both. Speifially, it was observed that the phosphate was entirely removed from the pore solution before 12 hrs in both ases. The removal of phosphate during the early hours of reation led to an inrease in OH- ion onentration in both the ases. The Case 3 waste form results indiated that arbonate was removed from the pore solution to preipitate alium arbonate and the alium monoarboaluminate phase [9]. These two reations appeared to result in inreases in the OH- ion onentration to a level approximately equivalent to that found for Case 2 waste form. n both ases the early redution of sodium ion onentration was signifiant, with the proess ontinuing but beoming very slow after 7 days. The NO; and N O i onentrations remained high throughout, indiating that these speies are not immobilized in the present systems. These results ontrasted strongly with reports onerning an alternate ementitious grout blend that inorporated a high volume of fly ash, and where the simulated waste solution was muh more alkaline. n those irumstanes zeolite was formed in situ, and espeially at higher temperature signifiant amounts of NO; and NO; were immobilized [ The other ions, mainly those released from the ement in early hydration period ( e g K' and SO:-) remain in the pore solution indefinitely.

7 H * i. a, -C N%- - \ 26-4 Sd \ 6 Kt 8 * 1 2 (a) 3:3:3: K a s e (b) 3:3:3:1/Case 3 Figure 1. oni onentrations of pore solutions of simulated off-gas waste forms at room temperature (22 C) H 12 r e-.h.a.. a m, 8 a, (a) 3:3:3:1/Case (b) 3:3:3:1/Case 3 Figure 2. oni onentrations of pore solutions of simulated off-gas waste forms (5 C) 1

8 z Ni3+ i P a, NO; A 4 v- 4 2 NO (a) 3:3:3: K a s e (b) 3:3:3:1/Case 3 Figure 3. oni onentrations of pore solutions of simulated off-gas waste forms (9 "C) * Lq 2 S4' a m 4 NO; L n ' - 6 Kf 8 Curing Temperature, OC (a) 3:3:3: K a s e 2 k 1 Curing Temperature, OC (b) 3:3:3:1/Case 3 Figure 4. oni onentrations of pore solutions of simulated off-gas waste forms (3 days uring)

9 8 z z 6 r i 'P z=! 44 a, a, 4 z ' (a) 3:3:3: K a s e (b) 3:3:3:1/Case 3 Figure 5. Conentrations of OH- ions in the pore solutions of simulated off-gas waste forms, as funtions of time and temperature The ioni onentrations derived from grout exposure at 5 C and 9 C are presented in Figure 2 and 3 respetively. At higher temperature the redutions in the onentration of Na' and OH- ions takes plae more rapidly. Only a small hange in NO; and NO; ion onentration was observed within 7 days, and thereafter they remained in the pore solution indefinitely. n Figure 4 (a) and (b) we show the influene of temperature on the onentrations of various hemial speies present in the pore solutions at 3 days for Case 2 and Case 3 grouts. Though Case 2 ondensate was highly alkaline and the Case 3 ondensate was arbonated, their immobilization behavior is seen to be almost similar. At 9 C there was a muh stronger redution in Na' and OH- ion onentrations in both ases than there was at room temperature. At higher temperatures there was a slight derease in nitrite onentration and orresponding inrease in nitrate onentration; most probably due to slow oxidation of nitrite to nitrate. There was a slight inrease in onentrations of both K' and SOT ions with temperature. n these systems the main soure of these ions is the ement, and at 9 C the ions are released faster to the pore solution. A more detailed examination OH- ion onentrations at all temperatures is given in Figure 5. Again both Cases yielded quite similar results. At room temperature the derease in OHonentration up to 7 days was similar for the two ases, but the redution was found to ontinue for longer periods in the Case 3 waste form. At and above 5 C most of the derease in OH-.

10 onentration ourred during the first 7 days; subsequent redution was limited. At 9 C after 9 days of hydration the OH-onentration in both the ases reahed an idential value. n both waste forms bleeding at early stages of hydration was a ommon problem, but generally higher amounts bleeding was observed with the Case 3 solution. A omparison of analyses for the separated bleed water (whih remained in ontat with hardened grout until removed) and expressed pore solution of 3 days old samples was made for samples hydrated at all three temperatures. t was found the variations in the ioni onentrations with temperature in the bleed water were found to losely math the orresponding data for the pore solutions as shown in Figure 4. This result indiates that at this early ages there is a fiee exhange of ioni speies between the pore solution and bleed water. CONCLUSONS The following onlusions were drawn from the present study. 1. n both Case 3 and Case 3 grouts all phosphate is removed from the pore solution with in a few hours. 2. The high initial onentration of dissolved arbonate in Case 3 grouts is rapidly removed from the pore solution, reating a solution environment similar to that present in the Case 2 grouts. 3. After a few hours of reation there is a signifiant inrease in OH' ion onentrations, but subsequently some Na' and OH-ions are removed from solution. 4. At higher temperatures signifiant additional amounts of Na' and OH- ions are removed fiom the pore solution. 5. Only a small amount of NO; is fixed or oxidized in the system leaving behind essentially all of the NO< and most of the NO; ions in solution indefinitely. ACKNOWLDGMNT This work was supported by the grant MTS-SVV-976 from the Westinghouse Hanford Company. RFRNCS 1. K. Brodersen, K. Berghman, F. P. Glasser, N. Longomazino, J. C. Nomine, and J. Wang, Radioative Waste Management and Disposal, edited by L. Celle, (lsevier Applied Sienes, Amsterdam,1991), p D.. Maphee and ;. P. Glasser, Mater. Res. SOC.Bull., 18(3.),p. 66 (1993). # 3, D.. Maphee, M. Atkins and F. P. Glasser in Sientifi Basis for Nulear Waste Management X, edited by W. Lutze and R. C. wing (Mater. Res. SOC.Pro. 127, Pittsburgh, PA, 1989), p M. Atkins and F. P. Glasser, Waste Management 12, p. 15 (1992). 5. R.. Lokken, J. W. Shade, and F. C. Martin in Sientifi Basis for Nulear Waste Management X, edited by W. Lutze and R. C. wing (Mater. Res. SOC. Pro. 176, Pittsburgh, PA, 199), p. 23.

11 L. Benny, "Disposing of liquid low level radioative tank wastes, Hanford site grout treatment faility" Conrete nternational, p. 14, July ( 199). 7. T. Bakharev, A. R. Brough, private ommuniation. 8. R. S. Barneybak, Jr. and S. Diamond, Cem. and Conr. Res., p. 279 (1981). 9. D. Bonen, et al. " Solidifiatiodstabilization of simulated alkaline nonvitrifiable low level radioative waste by early formation of arbonate bearing AFm phases" in Sientifi Basis for Nulear Waste Management XX, edited by W. M. Murphy and D. A. Kneht (Mater. Res. SOC.Pro., Pittsburgh, PA, 1996) in press. 1. A. Katz, A. R. Br-ough, T. Bakharev, R. J. Kirkpatrik, L. J. Struble and J. F. Young in Mirostruture of Cement-Dased SvstemslBondinn and nterfaes in Cementitious Materials, edited by S. Diamond et al. ( Mater. Res. SOC.Pr-o.37, Pittsburgh, PA, 1995), p A. R. Brough, A. Katz, T. Bakharev, G-. K. Sun, R. J. Kirkpatrik, L. J. Struble and J. F. Young in Mirostruture of Cement-Based Systems/Bondina and nterfaes in Cementitious Materials, edited by S. Diamond et al. (Mater. Res. SOC.Pro. 37, Pittsburgh, PA, 1995), p S. Ong and S. Diamond "Pore Solution studies of Simulated Low Level Waste Cement Grouts" presented in 96th Annual Meeting of Amerian Cerami Soiety, 1994 (unpublished).

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