: , .: iii i UNCLASSIFIED ORNL 438 *. . . T . fi . * - ' : . T . . nk ,* * VIR 9. - - -? - - it .. . . . . :" * 1 .. . . ." It! ORN-P_438 civi" 22- det 6 1968 REACTIONS OF CESIUM-137 AND STRONTIUM-90 WITH SOIL MINERALS AND SESQUIOXIDESA, Tsuneo Tamura Health Physics Division Oak Ridge National Laboratory Oak Ridge, Tennessee Selective sorption reactions of cesium- and strontium-bearing soin- tions are of particular interest in ground-disposal operations of radioac- tive wastes, because such solutions contain macroconcentrations of stable ions, with only microconcentrations of radioactive ions. It is also evi- dent from fallout contamination studies that selective sorption plays un Iraportant part in reducing the movement of radioñuclides into the deeper soil layers and in reducing the uptake of radionuclides by plants. The reactions of both cesium and strontium have been intensively investigated, and both these elements have shown selective sorption reactions with . 2 - minerals. 1,2 In the ground, cesium is characterized by its high affinity for soil .. ..?? minerals and strontium by its greater mobility due to reduced exchange . Wir . by the minerals. Another often observed difference in behavior of these two nuclides is that pH is an important consideration in strontium reten- tion, whereas cesium retention by minerals is generally insensitive to St pH changes between pH 5 and 10. With standard clay minerals possessing ion-exchange capacity, strontium and cesium behavior can be predicted A S Sto be published in the Proceedings of the Eighth International Congress of Soil Science, held on August 30 to September 9, 1964, Bu- charest, Romania. - -- O Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carba 'e Corporation. RT . Y - - 1 - - using mass action equations; however cesium sorption cannot be explained solely by the ion-exchange capacity of minerals. This paper will be con- cerned mainly with the reactions of microconcentrations of cesium and strontiuni and will discuss the principal factors responsible for their selective sorption. -.? Cesium Sorption by Ciay Minerals The chemical property of sorption by soils is generally attributable to the clay minerals, and the ion-exchange properties of the clay min- t erals are responsible for the sorption of cesium.? The exchange of ions -Ups . by the different clay minerals in solutions whose ionic concentration is high is reported in standard soils and clay reference sources. However, systems under which cesium is sorbed from fallout contamination or from - . . radioactive waste-disposal operations contain very low molar concentra- . tions of cesiun. The sorption of the ion under the latter conditions : F may be very different than from macroconcentration systems. . t EXY ZAK Thus in a system where the cesium concentration was 4 x 10*4 Mard the sodium concentration was 6 M, illite, with a relatively low ion-exchange . capacity, was found to be a more effective sorbent than montmorillonite, kaolinite, or hydrobiotite." Tests by Graham and Killion" with 0.01 M Caci, solutions containing spiked Cs15? also showed that illite and Putnam Clay sorbed more cesium than montmorillonite, kaolinite, or fibrous peat. Berak" studied the cesium uptake by numerous minerals in a system with 80 ppm calcium, 12 ppm magnesium, and 23 ppm sodium. His study showed that illite was as effective as most of the montmorillonites tested. In addition to pure minerals, he investigated the sorption by a basanite ** . 13 lay TV which had undergone various degrecs of alteration. He reported that * S SEXY APA LO IM 1. 6 a ** V ** .' 1 ' .CN ! ! ! ! increasing uptuke of cesium was associated with a drop in ion-exchange capacity; furthernore the alteration that resulted in an increase in exchange capacity and decrease in cesium sorption was associated with bentonization, that is, formation of montmorillonites. He therefore con- cluded that the alteration resulted in the destruction of sites responsi- ble for cesium selectivity from microconcentrations. Tamura and Jacobs” also considered the uptake of cesium on minerals on the basis of selec- tivity and ascribed the highly selective response of 1111te to the 10-A C-axis spacing of this mineral, In order to demonstrate the importance of the 10-a c-axis spacing of the clay minerals, Tamura and Jacobs saturated a hydrobiotite with potassium; the treatment reduced the spacing from 12.5 A to 10 A. Sorp- tion of cesium by the material then increased, even though the ion-exchange capacity decreased from 70 to 16 meq/100 g. To further strengthen their concept of the c-axis spacing, they heated montmorillonites to 600 to 700°C prior to exposure to cesium, and the increased sorption which they ob- served following this heat treatment was interpreted as further evidence of the importance of the c-axis spacing, and, more specifically, the im- , portance of the 10-A c-axis spacing. The difference in behavior of cesium at very low concentration levels and at much higher levels was also discussed by Jacobs and Tamura.' Below 2 x 10"" med of cesium per unit exchange capacity, 11lite was superior to montmorillonite and kaolinite. Above this value, 11lite was inferior; and, from the cesium response curves and desorption studies, it was postulated that 1111te fixed cesium in interlayer sites at the edges of the mineral and that a c-axis spacing of 10 A was most favorable for this type of sorp- tion. Since the c-axis spacing of only 10 A, which includes 9.4 A for the 1 h 14, C NN' + . ', 'W . .. ) . . is . : . . , . ' ' .. 1' > ' . . ... . ' . 1. . " IN . . .. YK .7 UL. . . ......... .. .... . .": " alumino-silicate layer, would restrict the migration of the ions into 13.SI+= n2 lattice, only a small amount of cesium could be acconanodated. The spac- ing of 10 A is "maintained" by the potassium ions in minerals such as illite; hence exchange involves substitution of cesium for potassium, which is difficult for ions such as calcium, sodium, or hydrogen. Later work by the author using K-42 tracer hus revealed that 1 lite shows very little exchange with potassium ions; this was to be expected, since ex- change of potassium with potassium ions is involved. By increasing the concentrations of potassium or cesium, entrapment of the ions during the saturation process can occur. The mineral vermicu- lite is most effective for sorbing cesium by this mechanism. Advantage was taken of the enhanced sorption with collapse-inducing ions, such as potassium, rubidium, armonium, and cesium, by adding these ions into waste solutions and demonstrating more efficient removal of cesium. ° This behavior of the mineral is additional evidence of the importance of the structural parameter in the sorption of cesium, since high competi- tive ions are used to enhance rather than reduce sorption. Although the response by the different clay minerals has been vari- able when investigated over a range of cesium concentration, three dif- - - . ferent curves representing the different clay minerals can be illustrated with the hydrobiotite sample with appropriate pretreatment. These three curves are shown in Fig. 1, and they may be referred to as the kaolinite- montmorillonite type (Cs-saturation), the 11lite type (K-saturation), and the vermiculite type (natural-saturation). In its natural state with magnesium ions as the dominant exchange cation, the hydrobiotite sorbs the highest amount of cesium in the concentration range of 102 to 10 mg S :. . . . . . . .- . AT . .. * R * * i .. . NYIN F 2 . N ", AL L . . . . .. . .. . . . 11:. ..'.'. ! . ! . !! ! ! . M . A NI Ini Y"14. - T S . ALLA WALI - . tor * . S . Saturated with Several Cations. Fig. 1. Cesium Removal in 0.1 N NaCl Solution by Hydrobiowite . . E UME * donn e i m Wind im Monat appears **** * **Hai * ** him to the artwil. Mogun tebi, upen the wory W all Paw P* *** Marithany Moments to the the no 2, II".. in ! . .. ".- . ' : . :... :: Hapa kwan ini . . . *** UNCLASSIFIED ORNL-DWG 63-5247 ST POTASSIUM SATURATED NATURAL MATERIAL (m2/8) T CESIUM SATURATED 10°? 104 104 100 109 102 103 CESIUM CONCENTRATION (mg/liter) WWW i ANIMA", win,'' ..: W ,,* LA !!!,,, mWM WWW SEE of cesium per liter of solution. This response is due to collapse of the lattice during the exchange of cesium with the magnesium ions, and the response is characteristic of the mineral vermiculite. If the mate- rial is pretreated with cesium, the curve is similar to the ones obtained for kaolinite and montmorillonite, which showed little or no influence of the structural parameter over a wide rango of cesium concentration. This was to be expected for cesium-pretreated hydrobiotite, since struc- tural changes had already been induced. When potassium was used to pre- treat the hydrobiotite, the lattice collapsed, but when cesium was brought into contact with the material, the potassium was replaced selectively at the edges by the cesium. This type of curve is similar to that ob- served for 11lite and mica. In addition to the explanations based on structural changes, as out- lined above, other mechanisms have been considered for the behavior of cesium with clay minerals. Schulz and his co-workers' reported that carrier-free cesium was fixed by way of precipitation on surfaces of micaceous minerals. . This explanation is difficult to reconcile, however, with their observed result that pretreatment of vermiculite and montmoril- lonite brought about an increase in cesium fixation. Furthermore, they observed that illite and chlorite by the same treatment showed a reduction in fixation. Nishita and his co-workers tº explain their results on sorption of cesium and potassium on the basis of the hydration of the clay surfaces and of the activity of the lons. Their explanation was based on the be- havior of cesium with kaolinite and montmorillonite. For these two min- erals, Jacobs and Tamura explained their observed response on the basis . ihr I'. NVX 17"i . . . 23 2 - .' . Y of a single mass-action coefficient.' (See curve for cesium-saturated hydrobiotite in Fig. 1.) The explanation of Nishita and his co-workers thus differs from that of Jacops and Tamura by considering the activity of the ions instead of the concentrations of the ions. For clays whose lattice parameters remain relatively constant, such as kaolinite and montmorillonite, simple mass-action relationships serve well in describ- ing cesium sorption; however, for other clay minerals, such as illite, with exchange sites that are relatively inaccessible to most ions, or for clay minerals whose structure changes with sorption of ions, such as cesium or potassium, single mass-action relationships are difficult to justify when cesiva concentration varies from tracer to symnetry levels. Cesium-Potassium Relationships in Soils In addition to noting that cesium was sorbed quite effectively from soils, investigators soon found that tests designed to show the similarity in reaction between cesium and potassium in soils were difficult to inter- pret. Klechkovsky and his co-workerst noted that saturation with potas- sium on two Russian soils resulted in large increases in cesium sorption, - whereas the same treatment on a third soil showed very little difference - - - . . . . in sorption. The high sorption of cesium by the third soil without the potassium treatment reported by these authors suggests that 111ite may be the dominant mineral in this soil; and illites, because of their precol- lapsed state, would not be expected to show increases by this treatment. If montmorillonite or vermiculite or both were present in the other two soils, the increased sorption might be ascribed to the collapse of the C-axis spacing of these minerals following the treatment. Al.though the .. .. mineralogy of the soils was not reported, it is interesting to note that Klechkovsky and his co-workers report that the presorbed potassium was not totally available for isotopic exchange with potassium. This behavior of the presorbed potassium would be expected for montmorillonite and ver- miculite that had been collapsed from the previously expanded condition, since the collapse would no longer allow the potassium to undergo free interchange with ions in solutions, Frederickson and his co-workers12 found that carrier-free cesium was strongly fixed in nine Swedish soils, and they noted that two soils high in illite.content showed pronounced fixation. They further noted that, when carrier cesium was added, the 11litic soils gave the largest increase in cesium content in plants. They conclude that the fixation capacity must be very small. The finding of Jacobs and Tamura' on the sorption characteristic of illite is in agreement with this conclusion. When potassium was added to the Swedish soils, cesium uptake by plants was reduced. Two possible reasons may be given for this observation. The more obvious explanation would be based on the dilution by potassium of the cesium ion, since the ions may be similar to each other. The other explanation may be the increase in unavailability of the cesium by the collapse of minerals such as montmorillonite and vermiculite. From the data it is difficult to ascertain which mechanism was dominant. Schulz and his co-workers concluded that fixation of Cs+s' in soils in carrier-free amounts is an essentially different process from the proc- - esses predominant in the fixation of macroamounts of cesium. They also state that only in the minerals, 11lite and chlorite, is csést extractable by ions in a fashion similar to that observed in the soils. By pretreat- ing the soils and clay minerals with potassium in amounts equal to the 3 . . .: fixation of cesium, they were led to believe that cesiun and potassium are not fixed on the same sites. They also observed that the treatment resulted in a slight increase in cesium fixation by vermiculite and montmorillonite but a slight reduction in the case of illite and chlorite. These results for the minerals are in agreement with the findings of Tamura and Jacobs-3,6,7 Ion Exchange Equilibria of Strontium Sorption of strontium by the clay minerals has been considered to be an ion exchange reaction; on the other hand, sorption of this element by activated alumina and the hydrous sesquioxides is believed to be by a different mechanism than that for the clay mineral. To get a better un- derstanding of the nature of the reaction of strontiu, comparisons were made of the sorption of strontium with several sorbents using mass-action considerations to depict ideal ion-exchange behavior. Mass-action expressions have been used by several investigators to describe ion-exchange equilibria.,..) For the exchange of strontium on a sodium clay, one may write: Sr2+ + Na, Src + 2Na+ and the equilibrium expression as: Src Na K = whereby K = equilibrium constant, C = clay, and 1 = activity. In a system where the strontium is present in tracer quantities and the clay is essentially sodium saturated, the activity coefficients of the sodium clay, strontium clay, and strontium ion may be considered to be constant. One can rewrite Eq. (2) in the form: (Src) Na+2 K' = (3) (sr+2)(NA,C) whereby K' incorporates the constant activity coefficients and the () denotes concentrations. By definition, the distribution coefficient for strontium is: (Src and one may combine Eq. (3) and (4) to form: (Na,c) Kg = K' Since the clay remains essentially sodium saturated, Na C is a constant, and a log Kg vs 10g Nat plot should yield a straight line. The slope of the line is a function of the exponent of Na* and Kg, and, in this case, the slope is -2. If one varies the sodium ion concentration over a wide range, the activity coefficient for the sodium ion changes and activity should be " ; . . . . / . R . TI MO . REM . .. .. .......... -- -.. . . used in the plot. With clay size particles, dispersion of the material 18 observed below approximately 0.01 M sodium nitrate; and accurate meas- urements of. (Sr2+) 18 difficult to obtain below this concentration. For a more complete treatment of mass-action equilibria in ion-exchange reac- tions, one is referred to the paper by K. A. Kraus. "? Strontium Sortion by Clay Minerals The log ka plot for montmorillonite and hydrobiotite is shown in Fig. 2. Note that in less than 0.02 M sodium ion activity, the K, appears constant for the montmorillonite sample; this is believed to be due to the dispersion of the very fine particles of montmorillonite : in the low salt concentration. On the other hand, the hydrobiotite represents materials between 0.5 and 0.2 mm in diameter, and very little dispersion was noted. These two materials represent the more classic examples of clays which exhibit ion-exchange characteristics by isomorphic substitution, and they exhibit a slope of -2 as calculated. It is inter- esting to note that the K, is greater for the hydrobiotite with approxi- mately 70 meg/100 g of cation-exchange capacity than for the montmorillonite with 90 meq/100 g. In Fig. 3 similar data is given for two illite samples. Tests show that the sample from Wisconsin differs from the one from Illinois in degree of crystallinity and exchange capacity. The former material gives a strong sharp diffraction maximum at 10 A in contrast to a weak diffuse maximum for the latter. The ion-exchange capacity is approximately 22 meq/100 g for the Wisconsin sample and 17 meq/100 g for the Illinois sample. The data in Fig. 3 show that Wisconsin illite's response is simi- lar to that of montmorillonite and hydrobiotite and that the response N , S • * . 17 344 . TAL 'S m __ Fig. 2. Influence of Nano, Concentration on Strontium Sorption by Montmorillonite and Hydrobiotite. ty . XX. ". . i . " 2 . - .. . .... 3 4 5 6 nolu C 16169 S S 16849 S - - - C .. ... .. . PL .... . . . .. - -. . . . . - . . -. . . - 0 1 V 15 . i... ure -: . . • . • * . C . * . 1 . .. . - • • .:.. 1 M • 1 ..- 0 . . - - mind MA . . BODMAH Hill 1999 - - . . - . -- LE 41 ' 19. : 0,01 0.1 Sodium Concentration (1:lol ur Activity) L'wi'. .! . . i UN YA NUNUN " :! 2017 . . 1 " . - - 3 , IL - L E . . .. . .... Influence of Sodium Nitrate on Strontium Sorption by Illites. 13 . Fig. 3. . ht WÁK . * ' -. * -. . - .. . - - - . - v . - : 7.5 . . .. . . .. TV3 . . . . - - - . . -j.obooth of . . . . 1. - - • - r • . . . ܕܕ ܫ. . . . 1 .. (... . 1 . . . 2 . 10 - 100 POON Haliliambuild ! 1 - - 12B - . - . . .. . E . . .. -. : 1 - . . 1 - - D . ..fi . 11!0UM ROM . . . . :t:::: III. - . .:::: ' : III -- :: . IINIT BE IIIWIWI IMINUI. 001 1.0 0.01 0.1 Sodium Concentration (Molar Activity) WO her N Du . . STS . "" . 1 '. . : 11 14. 1 1 ot! : .1 ** W RIT.*'', IN .PL follows the predicted mass-action reaction. The slope obtained for the Illinois sample 18 less than that predicted for ideal exchange; the rea- son for this difference in behavior is not yet known. It is interesting to note that despite a lower exchange capacity for the Illinois 11lite, the Ka is higher than the Wisconsin 111ite at all levels of sodium nitrate concentration. Strontium Sorption by Alumina When activated alumina (F-20 grade) from Aluminum Company of America was similarly tested, the response curve differed greatly from that ob- served with clays. The K, remained essentially independent of the sodium ion concentration (Fig. 4). This type of response might be expected for a precipitation reaction whereby strontium aluminate or similar type of compound is formed. This behavior of activated alumina is further evi- dence that alumina and clay minerals sorb strontium differently. Although it is premature to postulate a mechanism for the reaction between strontium and the alumina, several interesting applications of Ś even the data to waste solutions can be mentioned. In tracer-level strontiun solutions, whose sodium nitrate activity exceeds 0.04 M, alunina is a more effective sorbent than even hydrobiotite; and, as the sodium nitrate concentration increases, alumina as a sorbent is even more favored. Tests with aluminum oxide powder, which has much lower surface area than acti- vated alumina, show similar type of curve, and at pH. 9 the K, is higher than that observed at pH 7. Hence it is expected that the activated ulumina will also show a much higher K, in alkaline systems; a strontiun K, as high as 30,000 has been measured using heated Gibbsite which is a powdered re form of activated alumina. 15 . . . . -FRA . . Fig. 4. Influence of Sodium Nitrate on Strontium Sorption by Acti- vated Alumina, AY RUXEL TW . A . . X 1 " . LY IS 67 691 M um. HIHAHIRITINIANNINI 436 791 TAHUI MIRCHHIAAN AL HRHUNDAKI HAWA Wali BOKACHATHIRAT :. : .' MNMN 1 ::1 :.: . : Lii - - - 1: F.: .. ::.-1:: 0 illimi 0 : : S :::1 : . UL 1 ::..! : 1 . : Hli: 1 HL:1:11 11 1 11 HAMRATORE Titan To . IMA. DU -- - - - - - U :::::: :: I . :1: • . 1 . 1 T . : : MUUTUNUM TIIT :. RIIKLU 0.01 1.0 0.1 Sodiwn Concentration (Molar Activity) 4 SO 1 . 3 i' o. Y 2. 1 ! V ! * . !.. - 16 Strontium Sorption by Soil Material In addition to activated alumina, it was found that precipitated hydrous oxides of aluminum and iron and minerals, such as limonite, sorb strontium selectively from simulated radioactive waste solutions. 24 These results strongly suggested that these sesquioxides may be playing an im- portant role in the Conasauga shale material which is used at the Oak Ridge National Laboratory to decontaminate radioactive was tes. To test this suggestion, the Ky's were determined in solutions of different sodium nitrate concentration on a sample of shale obtained near the waste pit. At pH 7, the change in K, with increasing sodium nitrate concentra- tion agreed excellently with the predicted mass-action relationship. Re- moving the free iron oxide by the method described by Jackson's did not result in a noticeable change in the slope of the response curve. At pH 7 ک نستنننن Miri 19 .2 2 . . the sesquioxides were not expected to influence the slope significantly, especially since the material contained only 4.8% Fe2O, and 0.6% Algoz. The Conasanga shale is used to sorb waste whose sodium ion concentra- - - . .;- tion is about 0.1 M or higher and whose pH is above 9; therefore it was deemed highly desirable to test the material at a higher pH. The data ob- tained at pH 9 is shown in Fig. 5. Prior to removing the free iron oxide, ..* . .., . . the shale shows a slope which is less than -2; after removal the slope approaches -2 which suggests that the residual clay sorbs according to the law of mass action. The nonideal behavior of the treated material may be due to incomplete removal of aluminum oxide since the applied treatment was primarily for removing iron oxides. Tests with reference clay minerals at pH 9 show that sorption is improved at the higher pH and the free iron oxide removal treatment did not affect the sorption. Ion-exchange capacity . . . . . . . . . . . , .. . . . . . ! . * . AL TE! JUL 4. ..17 WIS. . - 2 : 1 - . . . Influence of Sodium Nitrate on Strontium Sorption by Cona- Fig. 5. sauga Shale. : - - . 3 4 5 6 7 8 9 1 3 4 5 6 7 8 9 1 3 4 5 6 7 8 9 .. 0 : , ... 1 11! . . - O . III . . . 1:11. II. D . 4 1 3 : 4 - + 1.37: 37 - + . . . . . . : U 1 . . . . . . . .. . . . . ..... . T . . 1 . M :: ::: :: : . . . . . • • . • . . . . - TIIN Coragaure Shale :.:: - 4 . - LQV TIN: . OCLOIWraturated BORDOBatonloader TRerho - - • 11 • 1 1 IL .. . . - .. - • l.: 1115 10: i MUIARTI ww :.'.;... 0.001 0.01 1.0 - . 0.1 Sodium Concentration (Molar Activity) i ...... . . - -- - 11 - 75*** o . .. in USATI W TO W 1" cannot be an important factor in this change of Conasauga shale after the treatment since the capacity increased from 13.0 to 17.7 meq/100 g. Results similar to Conasauga shale were obtained with Fullerton silt loan soil samples. In contrast to the Conasauga shale which is predomi- nantly illitic, the Fullerton is predominantly kaolinitic. Tests with iron oxide which was coated on quartz sand particles show that strontium sorption was increased by three to four times over the pure sand. These os results are strong evider.ce of the direct participation of the sesquioxides in sorbing strontium, anc. their role increases in importance in systems containing over 0,1 M sodium nitrate, Tests are continuing, and it is hoped that a better understanding of the mechanisms involved in the sorp- tion of microconcentrations of ions - particularly cesium and strontium - will be gained. Summary Selective sorption reaction of cesium in microconcentration range is ar strongly favored by a 10 A 001 spacing of the 2:1 layer lattice silicates. Chemical and heat treatments which alter the 001 spacing of these minerals can drastically change the distribution coefficient for cesium. Explana- tions are offered for the observed influence of potassium treatments on LUR 8. cesium sorption in soils based on the lattice concept of selectivity. Sorp- tion data for strontium are presented for several reference clay minerals and activated alumina. The possible strong influence of soil sesquioxides ST in sorbing strontium from radioactive waste solutions is suggested from data on soil materials. " Liit - : - . . .. **ormula ASA their own PUTSADES ' REFERENCES 1. TAMURA, T. and E. G. STRUXNESS, 'Reactions Affecting Strontium Removal from Radioactive Wastes', Health Physics 9: p. 697-704, 1963. 2. WAHLBERT, J. S. and M. J. FISHMAN, 'Adsorption of Cesium on Clay Minerals', Geological Survey Bulletin 1140-A, U.S. Government Printing Office, Washington, 1962. 3. TAMURA, T. and D. G. Jacobs, 'Structural Implications in Cesium Sorp- tion', Health Physics 2: p. 391-398, 1960. 4. GRAHAM, E. R. and D. D. KILLION, 'Soil Colloids as a Factor in the Uptake of Co, Cs, and Sr by Plants', Soil Sci. Soc. Amer. Proc. 26: p. 545-547, 1962. 5. BERAK, L., The Sorption of Microstrontium and Microcesium on the Sili- cate Minerals and Rocks, The Institute of Nuclear Research, The Czecho- slovak Academy of Sciences, Final Report of IAEA Research Contract No. 97, 1961, 1962. TAMURA, T. and D. G. Jacobs, 'Improving Cesium Selectivity of Bentonites by Heat Treatment', Health Physics 5: p. 149-154, 1961. 7. JACOBS, D. G. and T. Tamura, 'The Mechanism of Ion Fixation Using Ra. dioisotope Techniques', Transactions of the Seventh Internat. Cong. Soil Science, Madison, Wisconsin, 1959, 2: p. 206-214, 1960. JACOBS, D. G., 'Mineral Exchange Work at Oak Ridge National Laboratory', The Use of Inorganic Exchange Materials for Radioactive Waste Treatment, USAEC Report TID-7644, p. 187-199, January 1963. 9. SCHULZ, R. K. and R. Overstreet and I. Barshad, 'On the Soil Chemistry of Cesium 137', So:il Sci. 89: p. 16-27, 1960. 10. NISHITA, H. et al., Influence of Stable Cs and K on the Reactions of Cs-137 and K-42 in Soils and. Clay Minerals, USAEC Report UCLA-496, University of California, November 1961. - - 91 KLECHKOVSKY, V. M. and L. N. Sokolova and G. N. Tsclishcheva, The Sorption of Microquantities of Strontium and Cesium in Soils', Proc. Second United Nations Internat. Conference on the Peaceful Uses of Atomic Energy, Geneva, 1958, 18: p. 486-493, United Nations, New York, 1958. 12. FREDERICKSON, L. et al., 'Studies on Soil-Plant-Animal Interrelation- ships with Respect to Fission Products', Proc. Second United Nations Internat. Conference on the Peaceful Uses of Atomic Energy, Geneva, 1958, 18: p. 449-469, United Nations, New York, 1958. 13. KRAUS, K. A., Ion Exchange, in Trace Analysis, John Wiley and Sons, New York, p. 34-101, 1957. . . . Vi . BS . EN -- - 14. TAMURA, T., 'Selective Ion Exchange Reactions for Cesium and Stron- tium by Soil Minerals', Colloque International Sur La Retention et La Migration dos Ions Rudioactifs Dans Les Sols, Presses Universi- taires De France, Paris, p. 95-104, 1963. 15. JACKSON, M: L., Soil Chemical Analysis - Advanced Course, published by M. L. Jackson, University of Wisconsin, Madison 6, Wisconsin, p. 47-64, 1956. .. ... .. .. M . re nemas. .. .. . : . . ' . . . . . . . . MAS DATE FILMED 11/ 25 / 64 : LEGAL NOTICE - This report was prepared as an account of Govornment sponsored work. Neither the United Sutos, nor the Commission, nor any person acting on behalf of the Cora mission: A. Makes any warranty or reprosentation, expressed or implied with respect to the accu- racy, comploteness, or usefulness of the information contained in this report, or that the uso of any information, apparatus, method, or process disclosed in this report may not infringe privately owned rights; or B. Assumos any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or procou disclosed in this report, As used in the above, "person actag on behalf of the Commission" includes any on- ployee or contractor of the Commission, or omployee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor propares, disseminatas, or provides accos.' to, any information pursuant to his employment or coatract with the Commission, or his employment with such contractor. END " . '.. ' ! wl. . .. 17 TA ' . W !