Cesium immobilization into potassium magnesium phosphate matrix

The possibility of isomorphous substitution of potassium ions by cesium ions in the structure of potassium magnesium phosphate KMgPO₄ ∙ 6H₂O (PMP) was shown. It was established, that the Cs included into the PMP matrix does not transfer to the environment during high temperatures heating process (11...

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Datum:	2017
Hauptverfasser:	Sayenko, S.Y., Wagh, Arun S., Shkuropatenko, V.A., Bereznyak, O.P., Hodyreva, Y.S., Tarasov, R.V., Virych, V.D., Ulybkina, Е.А., Pylypenko, O.V., Kholomeev, G.O., Zykova, A.V.
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Sprache:	English
Veröffentlicht:	Національний науковий центр «Харківський фізико-технічний інститут» НАН України 2017
Schriftenreihe:	Вопросы атомной науки и техники
Schlagworte:	Материалы реакторов на тепловых и быстрых нейтронах
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Zitieren:	Cesium immobilization into potassium magnesium phosphate matrix / S.Y. Sayenko, Arun S. Wagh, V.A. Shkuropatenko, O.P. Bereznyak, Y.S. Hodyreva, R.V. Tarasov, V.D. Virych, Е.А. Ulybkina, O.V. Pylypenko, G.O. Kholomeev, A.V. Zykova // Вопросы атомной науки и техники. — 2017. — № 4. — С. 65-73. — Бібліогр.: 16 назв. — англ.

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spelling	irk-123456789-1361352018-06-17T03:03:04Z Cesium immobilization into potassium magnesium phosphate matrix Sayenko, S.Y. Wagh, Arun S. Shkuropatenko, V.A. Bereznyak, O.P. Hodyreva, Y.S. Tarasov, R.V. Virych, V.D. Ulybkina, Е.А. Pylypenko, O.V. Kholomeev, G.O. Zykova, A.V. Материалы реакторов на тепловых и быстрых нейтронах The possibility of isomorphous substitution of potassium ions by cesium ions in the structure of potassium magnesium phosphate KMgPO₄ ∙ 6H₂O (PMP) was shown. It was established, that the Cs included into the PMP matrix does not transfer to the environment during high temperatures heating process (1176 ºС, 3 hours). Analysis of the IR absorption spectrum of the PMP sample has demonstrated that an increase in the amount of additive of the cesium chloride resulted in the shift of the main bands in the spectrum to the low-frequency region with average shift value 10 cm⁻¹, which indicates the strengthening of bonds in the crystal lattice of matter. The calculated degree of substitution of potassium by cesium during energy release process in the PMP matrix at the level of vitrified high level wastes is about 4%, i. e. the PMP matrix should correspond to the formula K₀̦₉₆Cs₀̦₀₄MgPO₄ · 6H₂O. Показана можливість ізоморфного заміщення іонів калію в структурі калій-магнієвого фосфату KMgPO₄ ∙ 6H₂O (КМФ) на іони цезію. Встановлено, що включений в КМФ-матрицю Cs не виходить у навколишнє середовище при нагріванні до високих температур (1176 °С, 3 год). Аналіз ІЧ-спектра поглинання КМФ-зразка показав, що зі збільшенням кількості добавки хлориду цезію основні смуги в спектрі відчувають зрушення в низькочастотну область, величина якої в середньому становить ~ 10 см⁻¹, що свідчить про посилення зв'язків у кристалічній решітці речовини. Розрахована ступінь заміщення калію на цезій при енерговиділенні в КМФ-матриці на рівні осклованих високоактивних відходів складає ~ 4%, тобто КМФ-матриця повинна відповідати формулі K₀̦₉₆Cs₀̦₀₄MgPO₄ · 6H₂O. Показана возможность изоморфного замещения ионов калия в структуре калий-магниевого фосфата KMgPO₄ ∙ 6H₂O (КМФ) на ионы цезия. Установлено, что включенный в КМФ-матрицу Cs не выходит в окружающую среду при нагревании до высоких температур (1176 ºС, 3 ч). Анализ ИК-спектра поглощения КМФ-образца показал, что с увеличением количества добавки хлорида цезия основные полосы в спектре испытывают сдвиг в низкочастотную область, величина которого в среднем составляет ~ 10 см⁻¹, что свидетельствует об усилении связей в кристаллической решетке вещества. Рассчитанная степень замещения калия на цезий при энерговыделении в КМФ-матрице на уровне остеклованных высокоактивных отходов составляет ~ 4%, т. е. КМФ-матрица должна соответствовать формуле K₀̦₉₆Cs₀̦₀₄MgPO₄ · 6H₂O. 2017 Article Cesium immobilization into potassium magnesium phosphate matrix / S.Y. Sayenko, Arun S. Wagh, V.A. Shkuropatenko, O.P. Bereznyak, Y.S. Hodyreva, R.V. Tarasov, V.D. Virych, Е.А. Ulybkina, O.V. Pylypenko, G.O. Kholomeev, A.V. Zykova // Вопросы атомной науки и техники. — 2017. — № 4. — С. 65-73. — Бібліогр.: 16 назв. — англ. 1562-6016 PACS: 28.41.Kw http://dspace.nbuv.gov.ua/handle/123456789/136135 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України
institution	Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection	DSpace DC
language	English
topic	Материалы реакторов на тепловых и быстрых нейтронах Материалы реакторов на тепловых и быстрых нейтронах
spellingShingle	Материалы реакторов на тепловых и быстрых нейтронах Материалы реакторов на тепловых и быстрых нейтронах Sayenko, S.Y. Wagh, Arun S. Shkuropatenko, V.A. Bereznyak, O.P. Hodyreva, Y.S. Tarasov, R.V. Virych, V.D. Ulybkina, Е.А. Pylypenko, O.V. Kholomeev, G.O. Zykova, A.V. Cesium immobilization into potassium magnesium phosphate matrix Вопросы атомной науки и техники
description	The possibility of isomorphous substitution of potassium ions by cesium ions in the structure of potassium magnesium phosphate KMgPO₄ ∙ 6H₂O (PMP) was shown. It was established, that the Cs included into the PMP matrix does not transfer to the environment during high temperatures heating process (1176 ºС, 3 hours). Analysis of the IR absorption spectrum of the PMP sample has demonstrated that an increase in the amount of additive of the cesium chloride resulted in the shift of the main bands in the spectrum to the low-frequency region with average shift value 10 cm⁻¹, which indicates the strengthening of bonds in the crystal lattice of matter. The calculated degree of substitution of potassium by cesium during energy release process in the PMP matrix at the level of vitrified high level wastes is about 4%, i. e. the PMP matrix should correspond to the formula K₀̦₉₆Cs₀̦₀₄MgPO₄ · 6H₂O.
format	Article
author	Sayenko, S.Y. Wagh, Arun S. Shkuropatenko, V.A. Bereznyak, O.P. Hodyreva, Y.S. Tarasov, R.V. Virych, V.D. Ulybkina, Е.А. Pylypenko, O.V. Kholomeev, G.O. Zykova, A.V.
author_facet	Sayenko, S.Y. Wagh, Arun S. Shkuropatenko, V.A. Bereznyak, O.P. Hodyreva, Y.S. Tarasov, R.V. Virych, V.D. Ulybkina, Е.А. Pylypenko, O.V. Kholomeev, G.O. Zykova, A.V.
author_sort	Sayenko, S.Y.
title	Cesium immobilization into potassium magnesium phosphate matrix
title_short	Cesium immobilization into potassium magnesium phosphate matrix
title_full	Cesium immobilization into potassium magnesium phosphate matrix
title_fullStr	Cesium immobilization into potassium magnesium phosphate matrix
title_full_unstemmed	Cesium immobilization into potassium magnesium phosphate matrix
title_sort	cesium immobilization into potassium magnesium phosphate matrix
publisher	Національний науковий центр «Харківський фізико-технічний інститут» НАН України
publishDate	2017
topic_facet	Материалы реакторов на тепловых и быстрых нейтронах
url	http://dspace.nbuv.gov.ua/handle/123456789/136135
citation_txt	Cesium immobilization into potassium magnesium phosphate matrix / S.Y. Sayenko, Arun S. Wagh, V.A. Shkuropatenko, O.P. Bereznyak, Y.S. Hodyreva, R.V. Tarasov, V.D. Virych, Е.А. Ulybkina, O.V. Pylypenko, G.O. Kholomeev, A.V. Zykova // Вопросы атомной науки и техники. — 2017. — № 4. — С. 65-73. — Бібліогр.: 16 назв. — англ.
series	Вопросы атомной науки и техники
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fulltext	ISSN 1562-6016. ВАНТ. 2017. №4(110) 65 CESIUM IMMOBILIZATION INTO POTASSIUM MAGNESIUM PHOSPHATE MATRIX S.Y. Sayenko 1 , Arun S. Wagh 2 , V.A. Shkuropatenko 1 , O.P. Bereznyak 1 , Y.S. Hodyreva 1 , R.V. Tarasov 1 , V.D. Virych 1 , Е.А. Ulybkina 1 , O.V. Pylypenko 1 , G.O. Kholomeev 1 , A.V. Zykova 1 1 NSC “Kharkov Institute Physics and Technology”, Kharkov, Ukraine E-mail: shkuropatenko@kipt.kharkov.ua, tel./fax +38(057)335-39-05; 2 Argonne National Laboratory, Argonne, USA The possibility of isomorphous substitution of potassium ions by cesium ions in the structure of potassium magnesium phosphate KMgPO4 ∙ 6H2O (PMP) was shown. It was established, that the Cs included into the PMP matrix does not transfer to the environment during high temperatures heating process (1176 ºС, 3 hours). Analysis of the IR absorption spectrum of the PMP sample has demonstrated that an increase in the amount of additive of the cesium chloride resulted in the shift of the main bands in the spectrum to the low-frequency region with average shift value 10 cm -1 , which indicates the strengthening of bonds in the crystal lattice of matter. The calculated degree of substitution of potassium by cesium during energy release process in the PMP matrix at the level of vitrified high level wastes is about 4%, i. e. the PMP matrix should correspond to the formula K0.96Cs0.04MgPO4 · 6H2O. PACS: 28.41.Kw INTRODUCTION In the process of water cooled nuclear power reactors operations, a large number of liquid radioactive waste are formed, and their activity, despite of low concentration, is determined by 134,137 Cs and 60 Co radionuclides [1]. High-temperature methods of radioactive waste (RAW) treatment, including vitrification, can provide the formation of environmentally stable solid products. However, in the process of high-temperature manufacturing of such products, volatile cesium can partially transfer into the gas phase. It is known that such process has began from heating temperature about 575 °C and almost completely cesium passes into the gas phase at 900 °C [2]. Therefore, the search and development of solid materials formed at low temperatures and provided a high safety barrier for cesium fixing are environmentally justified. Furthermore, it should be taken into account that the main parameter characterizing the quality of solidificated wastes is thermal stability. According to the requirements of standard GOST, solidificated wastes should possess specific properties provided no changes in structure and chemical composition at temperatures up to 550 °C [3]. In addition, there is a risk of a fire in the underground radioactive waste storage and the temperature can increase to higher values. For example, two fire incidents took place in 2014 at a pilot plant for the isolation of waste (USA), which resulted in contamination of an underground ventilation system by plutonium [4]. According to such risks, it is necessary to carry out research on the heat resistance of materials of RAW matrices over a wide range of temperatures. The aim of this study was investigation of synthesis of cesium-containing potassium magnesium phosphates and their thermal stability under high temperatures heating conditions. MATERIAL AND METHODS The heat treatment of samples of potassium magnesium phosphate (PMP) was carried out in a high temperature furnace Nabertherm P310 (Germany) in air. The phase composition of the material before and after heat treatment was investigated by X-ray diffraction methods (DRON-1.5, Cu Kα with nickel filter for reduction of Kβ component of the characteristic radiation) and infrared (IR) spectroscopy (IR spectrophotometer IKS-29 (LOMO). Samples for the IR spectra recording were prepared in the form of transparent compressed tablets of mixture of KBr as the matrix and the tested substance (in the amount of 1%, weighed 100 mg). Spectra were recorded in the spectral range 4000…400 cm -1 (middle infrared area). To determine the processes that occur during heating of the powders, differential-thermal analysis (DTA) by means of thermal analyzer SDT Q600 V20.9 Build 20 in the temperature range 20…1300 °C at a heating rate of 10 °C/min was made. Elemental analysis of the PMP samples with the addition of 10 wt.% CsCl was carried out on a laser mass-spectrometer EMAL-2 with a high-resolution and two-focus by Mattaukh-Herzog. The random error of the analysis results is characterized by the value of the relative standard deviation of 0.1–0.3. RESULTS AND DISCUSSION SYNTHESIS OF POTASSIUM MAGNESIUM PHOSPHATE For the synthesis of potassium magnesium phosphate KMgPO4 ∙ 6H2O, the following reagents were used: – magnesium oxide MgO; – potassium dihydrogen phosphate KH2PO4; – distilled water (pH = 5.5). mailto:shkuropatenko@kipt.kharkov.ua 66 ISSN 1562-6016. ВАНТ. 2017. №4(110) a b Fig. 1. X-ray diffraction patterns of initial components of PMP samples: a – MgO, heat treated at 1300 °С during 1 hour; b – KH2PO4 PMP samples were obtained under normal conditions (atmospheric pressure, room temperature) as a result of the acid-base reaction between MgO and KH2PO4 in water: MgO + KH2PO4 + 5H2O = KMgPO4 ∙ 6H2O. (1) To reduce the rate of reaction of magnesium oxide with potassium dihydrogen phosphate, the MgO powder was heat treated at 1300 °C for 1 hour in air. The magnesium oxide obtained after heat treatment is characterized by a strongly pronounced periclase structure (Fig. 1,a). The diffractogram of the second component, potassium dihydrogenphosphate, is shown in Fig. 1,b. It can be seen that along with the main phase of KH2PO4 (pH = 4.46), a certain amount of the concomitant less reactive phase of K2HPO4 is also presented and characterized by higher pH values In the case of synthesis of cesium-containing PMP samples, cesium chloride CsCl was used as a starting reagent. X-ray phase analysis (XRD) of the obtained PMP samples revealed that the x-ray lines are corresponded to the crystalline hexahydrate of potassium and magnesium double orthophosphate KMgPO4 ∙ 6H2O (ASTM 35-0812) (Fig. 2,a). The density of the obtained PMP samples is 1.7…1.8 g/cm 3 . The behavior of the PMP samples under heating process was determined using DTA/TG analysis (Fig. 4,a). It was found that the endothermic peak at a temperature of 120 °C corresponds to the dehydration of potassium-magnesium phosphate according to the following reaction [5]: KMgPO4 ∙ 6H2O → KMgPO4 + 6H2O. (2) a b Fig. 2. X-ray diffraction patterns of PMP samples: a – without heat treatment; b – heat treated at Т = 1300 °С, τ = 45 min This process is confirmed by a weight loss (~ 40%) on the TG curve, which corresponds to a decrease in the stoichiometric amount of bound water. A small exothermic peak near 400 °C seems to correspond to the reversible α-KMgPO4 → β-KMgPO4 phase transition detected by the authors [6] during heat treatment of K-struvite single crystals of MgKPO4 ∙ 6H2O at a temperature of 362 °C. After heat treatment of the PMP samples at a temperature of 1300 °C for 45 min, the lines of dehydrated potassium-magnesium phosphate phase α-KMgPO4 are observed (see Fig. 2,b). These data are in good agreement with the data of XRD analysis of synthesized anhydrous phosphate KMgPO4 with the addition of Eu [7]. CESIUM-CONTAINING POTASSIUM MAGNESIUM PHOSPHATE MATRIX To carry out experiments on the incorporation of cesium into the PMP matrix, weighed samples of the initial reagents were used for the following reactions: – 10 wt.% CsCl + 90 wt.% (MgO + KH2PO4); – 15 wt.% CsCl + 85 wt.% (MgO + KH2PO4). From the data of XRD analysis of PMP samples with cesium, it can be seen that the obtained material is identified as potassium-magnesium orthophosphate, which in general form can be represented as K1-xCsxMgPO4 ∙ 6H2O (Fig. 3). In addition, lines of magnesium chloride phosphate Mg2PO4Cl were observed on the diffractograms. It can be seen that with an increase in cesium content (from 0 to 10% by weight α-KH2PO4 β-KH2PO4 ISSN 1562-6016. ВАНТ. 2017. №4(110) 67 CsCl and up to 15% by weight CsCl), a small shift of the main X-ray lines KMgPO4 ∙ 6H2O toward smaller angles occurs (see Figs. 2,a; 3,a,b). This is typical for the case of substitution of atoms of material by other atoms with large ionic radii. In our case, the potassium atoms are replaced by cesium atoms. As can be seen from Tabl. 1, the replacement of alkali ions is accompanied by insignificant changes in lattice parameters, while the crystal structure remains unchanged. Table 1 Lattice parameters of PMP and PMP +10 wt.% CsCl samples а b Fig. 3. X-ray diffraction patterns of samples: a – PMP+10 wt.% CsCl; b – PMP+15 wt.% CsCl Composition Lattice parameters а b c KMgPO4 ∙ 6H2O [8] 6.903 6.174 11.146 KMgPO4 ∙ 6H2O 7.6178 6.8512 12.2876 K1-xCsxMgPO4 ∙ 6H2O 7.646 6.8748 12.2575 a b c d Fig. 4. DTA/TG analysis of samples: a – PMP; b – MP + 10 wt.% CsCl; c – PMP + 15 wt.% CsCl; d – CsCl 68 ISSN 1562-6016. ВАНТ. 2017. №4(110) To determine the behavior of cesium-containing potassium-magnesium phosphates during heating process DTA/TG analysis of PMP + 10 wt.% CsCl and PMP + 15 wt.% CsCl. was made. The DTA/TG analysis data (see Fig. 4,b,c) show no weight loss of PMP samples with cesium during heating process up to 1200 °C. The exception is the weight loss associated with the removal of water in the temperature range 0…700 °C. Above 700 °C the weight of the samples remains practically unchanged; while CsCl completely evaporates in the temperature range 648…863 °C (see Fig. 4,d). This process indicates that the potassium magnesium phosphate matrix can reliably retain cesium during the temperature increase up to 1200 °C. Endothermic peaks at temperatures of 1106 ºС (see Fig. 4,b) and 1080 ºС (see Fig. 4,c) are probably caused by the melting of the sample material without loss of their weight. Analysis of the diffractogram of the PMP sample + 10 wt.% CsCl after treatment at a temperature of 1050 °C showed that the lines of anhydrous phosphate K1-xCsxMgPO4 (Fig. 5) are expanded under the action of high temperature. Heat treatment of PMP samples with cesium of 2…3 g weight were made in air at temperatures of 700, 1050, and 1176 °C with different holding times: 1, 2.5, and 3 hours, respectively. Samples were placed in boats made from Al2O3. The carried out experiments have shown that weight loss was about 27…28% after heat treatment at 700 °C. The results are well corresponded to the removal of crystallization water. With a further increase in temperature up to 1150 °C, weight loss of the samples was about 1%. Near this temperature, the process of samples material melting took place. Appearance of the sample PMP + 10 wt.% CsCl in the boat after heat treatment at 1176 ºС and holding time 3 hours is shown in Fig. 6. Elemental analysis of PMP samples with the addition of 10 wt.% CsCl was performed using an EMAL-2 laser mass spectrometer. The results of elemental analysis of PMP + 10 wt.% CsCl are presented in Tabl. 2. From the table data, it can be concluded that with increasing of the processing temperature the amount of cesium in the PMP samples remains practically unchanged. It should be noted that the cesium content in the PMP sample also remains almost the same after heat treatment at 1176 °C and the holding time 3 hours. These conditions are corresponded to the sample melting process. The paper presents the results of research on cesium immobilization in a chemically stable matrix based on potassium-magnesium phosphate. In other words, Cs can be included in the crystal structure of struvite-K using acid-base reaction-synthesis of PMP at room temperature. The addition of cesium chloride during the reaction leads to changes in the unit cell size of the resulting phosphates, and confirms the partial replacement of potassium by cesium. The PMP samples have kept the rhombic crystalline structure during this process. The resulted PMP matrix is heat-resistant and Cs doesn’t transfer to environment even after high temperatures heating. Table 2 Elemental analysis of PMP +10 wt.% CsCl samples after heat treatment process Temperature ant time of heat treatment process Content of elements, wt.% K Mg P O Cs Cl Na Al Si Ca S 700 °C, 1 hour 9.9 24.1 14.6 30.8 10.27 5.9 3.5 0.02 0.17 0.07 0.67 1050 °C, 2.5 hours 7.15 25.5 21.1 32.3 10.3 0.03 2.43 0.36 0.12 0.12 0.59 1176 °C, 3 hours 17.04 22.5 14.7 30.4 10.75 0.03 3.33 0.83 0.18 0.09 0.15 Fig. 5. X-ray diffraction patterns of PMP+10 wt.% CsCl sample after heat treatment at Т = 1050 °С, τ = 2.5 hours Fig. 6. Molten sample of PMP + 10 wt.% CsCl after heat treatment 1176 ºС and holding time 3 hours ISSN 1562-6016. ВАНТ. 2017. №4(110) 69 Fig. 9. IR absorption spectrum of sample with PMP +15 wt.% CsCl composition IR SPECTROSCOPY OF THE POTASSIUM MAGNESIUM PHOSPHATE MATRIX Analysis of the IR absorption spectrum of the PMP sample showed that the main bands of the IR spectrum correspond to potassium magnesium phosphate KMgPO4 ∙ 6H2O: 570, 630, 760, and 1050 cm -1 [9] (Fig. 7) in a good agreement with XRD data (see Fig. 2,a). However, bands of other compounds are also present in the spectrum: 1. The doublet of 1430 and 1470 and the strong band of 3400 cm -1 are probably caused by the formation of magnesite (MgCO3), since this frequency range is characteristic for vibrations of the complex anion of CO3 and OH groups in the structure of this mineral [10]. The formation of carbonate phases containing CO3 2- ions can be caused by the absorption of atmospheric carbon dioxide during the synthesis and storage of PMP samples. 2. The band 860 and the band 950, 980, 1100 cm -1 are caused by the vibrations of P(OH)2 and the complex PO2 ion in the phosphate structure, which may be products of incomplete synthesis. According to the IR spectrum the phase composition of the PMP sample + 10 wt.% CsCl, is the same as for the PMP sample without the addition of CsCl, since all the bands in the spectrum are coincided (Fig. 8). The difference lies in the fact that the intensity of all the bands corresponding to phosphate phases has increased substantially, and the maxima have become narrower and more precise. Such changes in the spectrum are associated with a higher degree of crystallinity of this sample. The data on XRD analysis of PMP samples without additives and with the addition of CsCl also demonstrate the increase in crystallinity (see Figs. 2,a; 3). The bands corresponding to the carbonate phase (magnesite) retained the same shape and intensity. Fig. 7. IR absorption spectrum of PMP sample Fig .8. IR absorption spectrum of sample with PMP +10 wt.% CsCl composition 70 ISSN 1562-6016. ВАНТ. 2017. №4(110) The overall view of the IR spectrum of the PMP + 15 wt.% CsCl sample (Fig. 9) is, in general, similar to the spectrum of the sample with the addition of 10 wt.% CsCl (see Fig. 8). However, it is necessary to note the following differences: 1. The main bands corresponding to the KMgPO4 ∙ 6H2O phase (565, 620, 760, and 1040 cm -1 ) are shifted to the low-frequency region of the spectrum by 5…10 cm -1 , and the intensity is slightly reduced. Such a shift of the absorption bands to the low- frequency region can be caused by an increase in the mass of atoms in the process of the isomorphous substitution of a part of the K atoms by the Cs atoms [12]. 2. There are significant changes in bands associated with the carbonate phase (magnesite), in the region of 1400…1500 cm -1 and 3400 cm -1 (see Figs. 8, 9). Instead of a band with a triple maximum (1410, 1430, and 1470 cm -1 ), a doublet of bands of the same intensity, 1440 and 1410 cm -1 , is formed, which is shifted to the low-frequency region by 10…30 cm -1 . In addition, the 3400 cm -1 band corresponding to the stretching vibrations of H-O-H in the magnesite structure of MgCO3 disappears. These changes may be associated with an increase in the symmetry of the crystal lattice of the carbonate phase, which is caused by a decrease in the water content. In general, it can be noted that with an increase in the amount of the addition of cesium chloride, all the main bands in the spectrum undergo a shift to the low-frequency region by average value about 10 cm -1 (Tabl. 3). This fact indicates the strengthening of bonds in the crystal lattice of material. An exception is the 1630 cm -1 band corresponding to the deformation vibrations of H-O-H, which remains unchanged. The intensity of the band 1090 cm -1 associated with the products of incomplete synthesis is apparently reduced due to a decrease of the products amount. This process is confirmed by the shift of the band 985 cm -1 associated with this phase to the high-frequency region. ENERGY RELEASE OF THE POTASSIUM MAGNESIUM PHOSPHATE MATRIX CONTAINED 137 Cs To determine the degree of substitution of K for Cs from the point of view of the permissible heating limit of the PMP matrix for the immobilization of cesium, the following calculations were made. During the process of the radioactive cesium inclusion into the potassium magnesium phosphate matrix, problems will be arisen due to the heating of the obtained material and associated with the radioactive decay of cesium. There will be necessary to organize the heat removal from canisters with HLW during their storage. To estimate the degree of heating of the PMP matrix during the immobilization of cesium, calculations were made of the specific energy release at the maximum degree of substitution of potassium with cesium. For such calculations, material of composition corresponded to the formula CsMgPO4 · 6H2O was used. For this purpose, the specific energy release in the PMP matrix was calculated on the basis of the data [13] of the energy parameters of the decay of 137 Cs (half-life 30.17 years) and its 137m Ba daughter product (2.55 min), which are given in Tabl. 4. Based on the conception that all potassium is replaced by cesium, and all cesium is represented by the 137 Cs isotope, this value was 150 W/kg. In the calculations it was assumed that the total energy released by β- and -radiation during the decay of one 137 Cs nucleus is about 0.75 MeV [13], and all this energy is absorbed by the PMP matrix. However, since the chemical properties of all the isotopes of the same chemical element are the same, during the process of cesium separation from the stillage bottoms by chemical methods, cesium will be obtained as a mixture of isotopes. To estimate the isotope composition of cesium in the stillage bottoms of nuclear power plants, it was assumed that the accumulation of long-lived cesium isotopes during fission of uranium by thermal neutrons is from 6.23 to 6.7% [14]. According to some assumption that the release of cesium from bottoms will be carried out, for example, after 30 years of soaking (during this time, exactly half of the 137 Cs decays and the shorter-lived isotopes decay almost completely), this mixture will have an isotopic composition close to that given in Tabl. 5. The energy release of 135 Cs was not taken into account for the further calculations, since it is four orders of magnitude lower than 137 Cs energy release. After 30 years removal from the reactor the 137 Cs isotope (see Tabl. 4) will represent only 19% of the total cesium. Based on this fact, the energy release in the PMP matrix with such an isotopic composition will be approximately five times less than in the matrix, in which all the cesium is represented by the radioisotope 137 Cs, and will be ~ 28 W/kg. This energy release is several times higher than the energy release in glass containing radioactive waste obtained after chemical processing of spent nuclear fuel (SNF) of power reactors. According to our estimates, which are based on the initial data [15, 16], 30 years after fuel unloading from the reactor, the energy release of vitrified HLW obtained after SNF processing is about 1.5 W/kg. To reduce the energy release in the PMP matrix to the level of vitrified HLW, according to our calculations, it is necessary to reduce the degree of substitution of potassium by cesium to ~ 4%, i. e. the PMP matrix should correspond to the formula K0.96Cs0.04MgPO4·6H2O. In the case of 10 wt.% substitution of potassium by cesium, the energy release of the PMP matrix is ~ 3.6 W/kg, which is almost 2.5 times higher than in vitrified HLW. This fact should be taken into account in the process of the storage organizing and final disposal of PMP matrix with cesium. ISSN 1562-6016. ВАНТ. 2017. №4(110) 71 Table 3 Bands description in the IR spectra of potassium-magnesium phosphates Table 4 The main energy parameters of radionuclide 137 Cs decay and its daughter product 137m Ва [13] Type of radiation Decay scheme Frequency, % Average energy release, MeV Integral of energy release, MeV -particles 137 Cs  137 Ва 5.64 0.41626 0.023477 137 Cs  137m Ва 94.36 0.17432 0.164488 -quantums 137m Ba  137 Ва 84.99 0.661659 0.562344 Sum of 1 decay: 0.750309 Table 5 The parameters of the cesium isotopes mixture with atomic masses 133, 135, and 137, generated by thermal fission of 235 U, at various time intervals after unloading from the reactor Isotopes Т1/2 Fission yield 235 U, % [14] Mixture content, % one month after 30 years after 133 Cs Stable 6.70 34.4 ~ 41 135 Cs 2.3 · 10 6 years 6.55 33.6 ~ 40 137 Cs 30.05 years 6.23 32.0 ~ 19 CONCLUSIONS 1. Potassium magnesium phosphate KMgPO4·6H2O was synthesized as a result of acid-base reaction between MgO and KH2PO4 in water under normal conditions (atmospheric pressure, room temperature). The evolution of the phase composition of potassium magnesium phosphate under heating to a temperature of 1300 °C has been studied. 2. The results of research on cesium immobilization in a chemically stable matrix based on potassium IR spectra, cm -1 Description of the bands 9–11 KMgPO4·6H2O KMgPO4·6H2O + 10 wt.% CsCl KMgPO4·6H2O + 15 wt.% CsCl 570 555 570 445, 550 565 deformation vibrations in the phosphate structure M-O (М-metal) 630 630 620 760 765 760 deformation vibrations of POH (out of plane) 860 860 850 stretching vibrations of Р(ОН)2 950 980 1050 1100 950 980 1050 1090 940 985 1040 1090 deformation vibrations of Р(ОН)2, stretching asymmetric vibrations of РО4 1430 1470 1410 1430 1470 1410 1440 vibrations of С-О in the magnesite structure MgCO3 1620 1630 1630 deformation modes of Н-О-Н 2360 2360 2310 stretching vibrations of Н-О-Н in KMgPO4·6H2O structure 2910, 3210 2930 2920 3400 3400 3360…3150 stretching vibrations of Н-О-Н in the magnesite structure MgCO3 72 ISSN 1562-6016. ВАНТ. 2017. №4(110) magnesium phosphate are presented. The addition of cesium chloride during the reaction leads to changes in the size of the unit cell of the resulting phosphates, and confirms the partial replacement of potassium by cesium. The included into the PMP matrix Cs does not transfer to the environment during high temperature heating process. 3. Analysis of the IR absorption spectrum of the PMP sample showed that the main bands in the IR spectrum are corresponded to potassium magnesium phosphate KMgPO4 ∙ 6H2O. With an increase in the amount of the cesium chloride addition, the main bands in the spectrum demonstrate a shift to the low-frequency region with average value about 10 cm -1 . This fact indicates the strengthening of bonds in the crystal lattice of obtained material and the isomorphous substitution of a part of the K atoms by the Cs atoms. 4. The calculations of the energy release of 137 Cs in the PMP matrix have shown that to reduce the energy release in the PMP matrix to the level of vitrified HLW, the degree of potassium replacement for cesium should be about 4%, i. e. the PMP matrix should correspond to the formula K0.96Cs0.04MgPO4 · 6H2O REFERENCES 1. С.А. Кулюхин, Н.А. Коновалова, М.П. Горба- чева и др. Извлечение 60 Co и 137 Cs из модельного раствора трапных вод АЭС // Радиохимия. 2013, т. 55, №3, с. 242-248. 2. А.И. Орлова, Е.Е. Логинова, А.А. Логачева и др. Кристаллохимический подход при разработке фосфатных материалов для формирования экологически безопасных химических форм утилизации Cs-содержащих отработанных ферроцианидных сорбентов // Радиохимия. 2010, т. 52, №5, с. 391-396. 3. ГОСТ Р 50926-96. Отходы высокоактивные отвержденные. Общие технические требования. М.: Изд-во стандартов, 1996, с. 7. 4. US Department of Energy, Waste isolation pilot plant recovery plan. Washington, DC, DOE, 2014. 5. Siyu Zhang, Hui-Sheng, Shao-Wen Huang, Ping Zhang. Dehydration characteristics of struvite-K pertaining to magnesium potassium phosphate cement system in non-isothermal condition // J. Therm. Anal. Calorim. 2013, v. 111, p. 35-40. 6. G. Wallez, C. Colbeau-Justin, T. Le Mercier, M. Quarton, and F. Robert. Crystal Chemistry and Polymorphism of Potassium-Magnesium Monophospate // Journal of Solid State Chemistry. 1998, v. 136, p. 175-180. 7. Suyin Zhang, Yanlin Huang, Hyo Jin Seo. Luminescence properties and structure of Eu 2+ doped KMgPO4 phosphor // Optical Materials. 2010, v. 32, p. 1545-1548. 8. A.S. Wagh. Chemical bonded phosphate ceramics. Elsevier, Argonne National Laboratory, USA, 2004, 283 p. 9. Frost, Ray L., Xi, Yunfei, Palmer, Sara J., Tan, Keqin, & Millar, Graeme J. Vibrational spectroscopy of synthetic archerite (K, NH4)H2PO4: and in comparison with the natural cave mineral // Journal of Molecular Structure. 2012, v. 1011, p. 128-133. 10. Van der Marel, H. Beutelspacher. Atlas of infrared spectroscopy of clay minerals and their admixtures. Amsterdam: Elsevier scientific publishing company, 1976, p. 396. 11. Vilas Bhagawat Suryawanshi, Ravindranath Teniram Chaudhari. Synthesis and Characterization of Struvite-k Crystals by Agar Gel // Journal of Crystallization Process and Technology, 2014, v. 4, p. 212-224. 12. А.С. Поваренных. Связь ИК-спектров минералов с кристаллохимическими факторами // Минерал. сборник Львовского государств. университета. 1970, в. 1, №24, c. 12-29. 13. Интернет-ресурс: http://www.nucleide.org/DDEP_WG/Nuclides/Cs- 137_tables.pdf . 14. В.М. Колобашкин, П.М. Рубцов, П.А. Ру- жанский и др. Радиационные характеристики облученного ядерного топлива: Справочник. М.: «Энергоатомиздат», 1983, с. 384. 15. В.М. Ажажа, В.А. Белоус, С.В. Габелков и др. Ядерная энергетика: обращение с отработанным ядерным топливом и радиоактивными отходами / Под ред. акад. И.М. Неклюдова. Киев: «Наукова думка», 2006, с. 253. 16. Ж.С. Ажажа, Л.Н. Ледовская, А.В. Пили- пенко, С.Ю. Саенко, Г.А. Холомеев. Теплофизи- ческие аспекты выбора параметров глубинного хранилища высокоактивных отходов и отработанного ядерного топлива // Ядерна та радіаційна безпека. 2012, в. 1 (53). Статья поступила в редакцию 21.06.2017 г. ИММОБИЛИЗАЦИЯ ЦЕЗИЯ В КАЛИЙ-МАГНИЙ-ФОСФАТНУЮ МАТРИЦУ С.Ю. Саенко, А.С. Ваг, В.А. Шкуропатенко, Е.П. Березняк, Ю.С. Ходырева, Р.В. Тарасов, В.Д. Вирич, Е.А. Улыбкина, А.В. Пилипенко, Г.А. Холомеев, А.В. Зыкова Показана возможность изоморфного замещения ионов калия в структуре калий-магниевого фосфата KMgPO4 ∙ 6H2O (КМФ) на ионы цезия. Установлено, что включенный в КМФ-матрицу Cs не выходит в окружающую среду при нагревании до высоких температур (1176 ºС, 3 ч). Анализ ИК-спектра поглощения КМФ-образца показал, что с увеличением количества добавки хлорида цезия основные полосы в спектре испытывают сдвиг в низкочастотную область, величина которого в среднем составляет  10 см -1 , что свидетельствует об усилении связей в кристаллической решетке вещества. Рассчитанная степень замещения ISSN 1562-6016. ВАНТ. 2017. №4(110) 73 калия на цезий при энерговыделении в КМФ-матрице на уровне остеклованных высокоактивных отходов составляет ~ 4%, т. е. КМФ-матрица должна соответствовать формуле К0,96Cs0,04MgPO4·6H2O. ІММОБІЛІЗАЦІЯ ЦЕЗІЮ У КАЛІЙ-МАГНІЙ-ФОСФАТНУ МАТРИЦЮ С.Ю. Саєнко, А.С. Ваг, В.А. Шкуропатенко, О.П. Березняк, Ю.С. Ходирєва, Р.В. Тарасов, В.Д. Вірич, К.А. Улибкіна, О.В. Пилипенко, Г.О. Холомєєв, Г.В. Зикова Показана можливість ізоморфного заміщення іонів калію в структурі калій-магнієвого фосфату KMgPO4 ∙ 6H2O (КМФ) на іони цезію. Встановлено, що включений в КМФ-матрицю Cs не виходить у навколишнє середовище при нагріванні до високих температур (1176 °С, 3 год). Аналіз ІЧ-спектра поглинання КМФ-зразка показав, що зі збільшенням кількості добавки хлориду цезію основні смуги в спектрі відчувають зрушення в низькочастотну область, величина якої в середньому становить  10 см -1 , що свідчить про посилення зв'язків у кристалічній решітці речовини. Розрахована ступінь заміщення калію на цезій при енерговиділенні в КМФ-матриці на рівні осклованих високоактивних відходів складає ~ 4%, тобто КМФ-матриця повинна відповідати формулі К0,96Cs0,04MgPO4·6H2O.

Cesium immobilization into potassium magnesium phosphate matrix

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