Assessment of individual and mixed alkali activated binders for solidification of a nuclear grade organic resin loaded with 134Cs, 60Co and 152+154Eu radionuclides

Assessment of individual and mixed alkali activated binders for solidification of a nuclear grade organic resin loaded with 134Cs, 60Co and 152+154Eu radionuclides

Accepted Manuscript Title: Assessment of individual and mixed alkali activated binders for solidification of a nuclear grade organic resin loaded with...

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Accepted Manuscript Title: Assessment of individual and mixed alkali activated binders for solidification of a nuclear grade organic resin loaded with 134 Cs, 60 Co and 152+154 Eu radionuclides Authors: M.R. El-Naggar, E.H. El-Masry, A.A. El-Sadek PII: DOI: Reference:

S0304-3894(19)30491-1 https://doi.org/10.1016/j.jhazmat.2019.04.063 HAZMAT 20580

To appear in:

Journal of Hazardous Materials

Received date: Revised date: Accepted date:

9 January 2019 18 April 2019 19 April 2019

Please cite this article as: El-Naggar MR, El-Masry EH, El-Sadek AA, Assessment of individual and mixed alkali activated binders for solidification of a nuclear grade organic resin loaded with 134 Cs, 60 Co and 152+154 Eu radionuclides, Journal of Hazardous Materials (2019), https://doi.org/10.1016/j.jhazmat.2019.04.063 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Assessment of individual and mixed alkali activated binders for solidification of a nuclear grade organic resin loaded with 134Cs, 60Co and 152+154Eu radionuclides

M.R. El-Naggar, E.H. El-Masry, A.A. El-Sadek

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Hot Laboratories Center, Atomic Energy Authority, Post Code 13759, Cairo, Egypt

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Corresponding author. Tel.: +20-55-234-5895; fax: +20-2-462-0796. E-mail address:[email protected] (M.R.El-Naggar).

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Single, binary and ternary binders with at least 8% KY-2 have been well optimized. Comparative leaching of 134Cs, 60Co and 152+154Eu radionuclides were assessed. Leachability indexes were high and sometimes be twice the waste acceptance criteria. The ternary binders were radiation stable while the solidified hot beads were not. A three-step mechanism of such instability of the solidified hot beads was proposed.

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    

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Highlights

Abstract

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Individual metakaolin-based alkali activated binder (AAB) was utilized to optimize binary and ternary

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ones having feldspar⁄metakaolin and slag⁄(feldspar + metakaolin)ratios of 0.3 and 0.4, respectively. These three AABs had the ability to directly solidify 10.0 (FMK0-10R), 8.0 (FMK3-8R) and

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12.0% (S4FMK3-12R) of the nuclear grade KY-2 beads, respectively, recording compressive strength values greater than twice the waste acceptance criteria. Leaching of 134Cs, 60Co and 152+154Eu, whether

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singularly or multiply loaded, was assessed. The multi-radionuclidic systems recorded greater leached fractions in the order of: 152+154Eu>134Cs>60Co. Among the studied systems, S4FMK3-12R formulations recorded the lowest diffusion coefficient values (D). Gamma-irradiation made a desired influence on all studied leaching systems with inverse relationships with the applied irradiation doses. Irradiating the optimized ternary AAB with 3.0 KGy (S4FMK3-12R-ɣ3) yielded the lowest D value (6.65 × 10-13 1

cm2/s), when single component-60Co was diffused. The leachability indexes of all irradiated AABs were not only greatly exceeded the value of 6 but also sometimes be twice such value. XRD, FT-IR and SEM examinations of S4FMK3, S4FMK3-12R and S4FMK3-12R-ɣ3 reflected their multi-layered semicrystalline natures and to what extent these AABs and the solidified beads had good and poor

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radiation stabilities, respectively, with a proposed three-step mechanism of such instability.

Key words: Geopolymeric microstructures, Direct immobilization, Organic ion-exchangers, fission/activation products, Leaching.

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1. Introduction

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Nuclear facilities such as plants of nuclear power and fuel reprocessing, research reactors and centers,

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…etc. produce different waste streams requiring treatment for process chemistry dominance and/or

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decontamination purposes [1]. Egypt holds 22 MW open pool type research reactor (ETRR-2) at Inshas

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area (~1.0 km2; longitudes of 31° 20′ & 31° 30′ E and latitudes of 30° 15′ & 30° 25′ N). Radioactive

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hazardous materials from ETRR-2 should be controlled in the pool water and the out of core pipework to alleviate the levels of activation and fission products and the uncontrolled neutron capture

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reactions. Abdelhady mentioned the estimated nuclide concentrations (Bq/m3) in the pool water of

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ETRR-2 [2]. Both cesium (134Cs and radionuclides (152Eu and

154Eu;

137Cs;

t1/2 of 2.06 and 30.17 y, respectively) and europium

t1/2 of 13.54 and 8.69 y, respectively), as fission products, and cobalt

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(60Co; t1/2 of 5.27 y), as an activation product, were represented. Ion exchange is one of the most common techniques that can be efficiently fulfill the nuclear industry demands. Nuclear grade resins (NGRs) are ion exchangers with specific higher properties in terms of purity, conversion rate, particle size uniformity, mechanical integrity that are widely applied in the nuclear sector [3] in large volumes. KY-2 and AN-31 beads are strongly acidic (cationic) and weak basic (anionic) NGRs, respectively, which 2

were produced in USSR [4] and were installed in Inshas rad-waste treatment plant [5]. Such treatment facility includes combined processes of chemical precipitation, sand filtration and two stage demineralization cation and anion NGRs of about 10 m3 in order to treat the collected low- and intermediate-level liquid rad-wastes. Generally, replacement of NGRs should be scheduled depending

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on either their depletion or the significance of their contained radioactivity [6]. International Atomic Energy Agency (IAEA) recommends the direct solidification of the spent NGRs into suitable matrices rather than their regeneration (produces highly acidic and caustic radioactive waste streams) and thermal treatments (special regimes are required for treatment of α-bearing wastes) [7-8]. Although

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ordinary Portland cement (OPC) is the traditional material to solidify rad-wastes [9], its limited

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application regarding NGRs due to swelling, cracking and poor integrity of formulations made the

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assessment of alternatives to be an appealing research arena.

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Alkali activated binders (AABs) are eco-friendly unique amorphous to semi-crystalline structures of

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coordinated aluminosilicates in a polycondensation reaction [10]. Recently, AABs are considered as

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alternatives to OPC in many applications due to their superior properties in terms of mechanical strength, acid and fire resistances, thermal and radiation stabilities, solidification of hazardous wastes

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with low energy consumption [11-16]. Many industrial products (feldspar [17], kaolin [18], red-mud

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[19]) and bi-products (concrete and granite wastes [20-21], fly ash [22]) can produce such binders. Egypt has large reserves of kaolin and feldspar, distributed between different localities [23-24], beside

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an annual production of blast furnace slag of about 300,000 tons [25] that could make such technology be applicable. Majority of researchers dealt with the immobilization of inorganic wastes containing heavy metals using individual AABs [26-29]. While, considerable efforts were performed to assess the performance of individual and binary component AABs to immobilize rad-wastes of inorganic origin [30, 16]. Additionally, little studies were observed regarding the direct solidification of 3

organic rad-wastes into AABs. Cantarel et al. [31] and El-Naggar et al. [32] succeeded to directly stabilize/solidify wastes of organic origin using individual metakaolin-based AABs. Also, AMEC Nuclear Slovakia established its licensed product (SIAL® matrix) to directly solidify the spent resins at the Dukovany Nuclear Power Plant, Czech Republic [33]. Hence, investigation of more complex AAB

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systems could be appreciated towards wider applications of geopolymer technology.

Therefore, the aim of the present study is to assess different AABs (individual, binary and ternary

mixtures) of metakaolin, feldspar and blast furnace slag, as efficient alternatives to OPC, to directly solidify KY-2 resin since the later spikes the majority of the contained radioactivity. The assessment

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criteria were based on investigations of mechanical integrity (compressive strength, MPa) in parallel

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to leaching of 134Cs, 60Co, 152+154Eu and their ternary radionuclidic mixture from either non-irradiated

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or γ-irradiated optimized formulations. The yielded behavioral data of the optimized ternary AABs

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were related to their microstructural characteristics by means of X-ray diffraction (XRD), Fourier

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2. Materials and methods

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transform infrared (FT-IR) and scanning electron microscope (SEM) examinations.

Concerns have been expressed about the suitability of individual, binary and ternary alkali activated

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2.1. Materials

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binders to solidify cationic ion exchange resins of nuclear interest.

Metakaolin (MK), feldspar (F) and blast furnace slag (S) were the raw binders for the synthesis of

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different formulations. Metakaolin (SiO2 = 55.91 %; Al2O3 = 34.34 %; total minor oxides = 9.75% [11]) was obtained by the calcination (750°C/4 h; 5°C/min.) of the local kaolin (Abo-Zenama district, west Sinai, Egypt) using a programmable electric furnace. Feldspar (SiO2 = 72.37 %; Al2O3 = 11.97 %; total minor oxides = 15.66% [24]) was obtained from Road Eshab locality of the Eastern Desert, Egypt, while the water quenched blast furnace slag (SiO2 = 33.25 %; Al2O3 = 12.23 %; CaO = 45.42 %; total 4

minor oxides = 9.10 % [16]) was obtained from the Egyptian Iron and Steel Company. Sodium metasilicate (assay: ≥ 97%) and europium oxide were products of Sigma-Aldrich. Sodium hydroxide, nitric acid and the chloride salts of cesium and cobalt ions were products of British Drug Houses chemicals (BDH). The NGR (Russian; KY-2) was obtained from the Egyptian low-level rad-waste plant,

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Inshas, Egypt. It is a highly acidic cationite (𝑆𝑂3 𝐻) of polystyrene plus 8% divinylbenzene (DVB) having a particle size range of 0.3-1.2 mm [4]. Table (1) indicated the analysis of the applied ground water which was obtained from Bilbies formation (Inshas, Qalubia, Egypt). The geological studies of Bilbies formation which were reported by Abdel-Karim et al., including the direction of ground water flow, were

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considered [34-35]. Simulated liquid rad-wastes were prepared by labeling the single and ternary

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aqueous solutions by 134Cs, 60Co and/or 152+154Eu radionuclides which were produced at ETRR-2.

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2.2. Elaboration of resin beads

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2.2.1. Cold damp resin

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Cold “non-radioactive” resin was elaborated for compressive strength experiments. The KY-2 beads

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were employed in their unloaded hydrogen form. An appropriate quantity was packed in a borosilicate glass column (1.6 cm i.d. × 10 cm height) and then was washed with water at a rapid flow

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rate to obtain a neutral effluent. The wet resin was then collected and was placed into a tight fitted

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polypropylene container which was modified to accept 15 psi air line and a glass wool filtered drain. Pressure was applied to remove the interstitial water from the wet resin. Resin prepared by this

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method was termed as cold damp resin which assured both saturation and uniformity of water content.

2.2.2. Hot damp resin Radionuclide-contaminated (hot) resin beads of known composition have been laboratory-prepared for leachability investigations. Chloride salts of cesium and cobalt ions as well as europium oxide were 5

utilized to prepare their single and ternary aqueous solutions having initial concentration of 2 × 103 mg/L each. These solutions were prepared by dissolving appropriate quantities (that satisfy the theoretical capacity of KY-2; 4.7 meq/g) of the corresponding metal ion salt in bi-distilled water. Each prepared solution was labeled by its respective radionuclide (134Cs, 60Co, 152+154Eu or their ternary

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mixture). A quantity of as received KY-2 resin was washed with water by the method described above and then was dried at 110°C for 18 h. Such dried quantity was divided into four portions which were soaked in their respective radioactive solution (2 × 103 mg/L) for at least 18 h with occasional stirring. Resins were then drained, collected and transferred to the aforementioned tight fitted polypropylene

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containers in order to obtain hot damp resins. Control waste forms containing the uncontaminated

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resin (cold) were employed throughout.

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2.3. Development of alkali activated binders

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Alkali activated binders were developed and tested in laboratory scale. Individual and mixed binders

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(45 µm each) were designed according to Table 2 by the blending of different ratios between feldspar

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and blast furnace slag to metakaolin and feldspar plus metakaolin, respectively. Table 2 was designed using the one-factor-at-a-time method to achieve a primary goal which is getting AABs with better

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performance toward solidification of spent ion exchange resins. A good binder has to withstand the

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compression and record lower values of the leached fractional activities. Thus, Table 2 was divided into three main groups (G I-III) in which the 1st and 2nd groups has been allocated to the mechanical

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strength investigations by the aid of two and three sub-groups, respectively. While, the 3rd group was allocated to consider the leachability of the radionuclidic systems. Alkaline silicate solution (ASS) was prepared (24 h prior to its use) at 𝑆𝑖𝑂2 ⁄𝑁𝑎2 𝑂 , 𝑆𝑖𝑂2⁄𝐻2 𝑂 and 𝑁𝑎2 𝑂⁄𝐻2 𝑂 ratios of 1.35, 0.44 and 0.33, respectively. Such solution was applied to produce the AABs at different solid⁄liquid range from 0.75 to 0.85, depending on the raw blends. 6

2.4. Solidification investigations 2.4.1. Mechanical strength The mechanical properties of waste forms are of concern within the disposal sites. Waste form failure under load may lead to cracking or friability creating a larger effective surface area from which activity

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can be leached. Compressive strength tests, expressed as the maximum applied load divided by the cross-sectional area of a specimen, were performed as a measure of mechanical integrity.

Measurements were achieved by a load compression machine (model WF, Eng., UK) according to the British Standard, with test data accuracy of ± 1%. All pastes of the AABs were prepared by placing the

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desired binders on smooth non-absorbent surfaces, and craters were formed into centers.

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Appropriate volumes of ASS were poured into craters and then the vigorous mixing operations were

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completed using a helix grout mixer (1500 rpm for 4 min). Pastes were cast into acrylic moulds (40 ×

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40 × 40 mm i.d.), were vibrated for 2 min to remove entrained air and were covered with a

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polyethylene thin sheet to prevent water evaporation. The prepared moulds were kept at ambient

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conditions for 24 h then were demoulded and were kept for 28-days curing time Fig. 1a. Both groups I and II (Table 2) were designed to explore the 28-days compressive strength. The former group has

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been allocated to explain the effects of feldspar and blast furnace slag when added to individual MK

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and F-MK binary blends, respectively. While, the later group has been allocated to consider the effect of different percentages of cold damp resin when added to the individual MK (FMK0) as well as their

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optimized binary (FMK3) and ternary (S4FMK3) blends with feldspar and slag. A good binder is expected to withstand the maximum achievable compression (MPa) which accompanied by good workability with suitable setting time. 2.4.2. Leachability investigations

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If the geopolymerization of NGR is to be accepted as a suitable process for subsequent disposal process it must be possible to show that it impedes the flow of radionuclides into the biosphere. To demonstrate this purpose, leaching of 134Cs, 60Co and 152+154Eu from the examined AABs into ground water, with the composition given in Table 1, were comparatively performed by the IAEA’s standard

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static leaching test that proposed by Hespe [36]. The present study replaced the demineralized water (proposed by Hespe, 1971 [36]) by the presented ground water in order to simulate the reality in the burial site at Inshas area. Forty eight acrylic cylinders (20 × 10 mm i.d.; Fig. 1b) were used to cast

pastes of group III given in Table 2. The acrylic choice was selected to assure that it will withstand the

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involved severe alkaline conditions without any chemical reaction with the casted pastes. Effects of

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AAB type and γ-irradiation on leaching of radionuclides from single and multiple component (SC and

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MC, respectively) loaded resins were investigated. After 28 curing time, cylinders were demolded and

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sub-divided into four sub-groups. Only one group was directly immersed in the leaching medium.

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While, others were firstly subjected to the γ-irradiation before immersion. Three cumulative γ-

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irradiation doses (1.0, 2.0 and 3.0 KGy) were applied at a dose rate of 670.687 Gy/h using the 60Co gamma cell (MC-20, Russia) which installed at the Cyclotron Project, Inshas, Egypt. An irradiation

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experiment was performed because that the internal environment of the waste form is of concern in

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the radioactive waste disposal site. A good binder is expected to exhibit lower cumulative leached fractional activities of the immobilized radionuclides, with respect to irradiation. Containers of

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leaching were selected to be not sorbent toward the ions involved in the test procedure without any reaction with leachants. The ratio between volume of leachant and the exposed surface area of specimen was not more than 10 cm [36]. Samples of the leaching solution were withdrawn at the frequency of: daily during the first week, once per week for the following four weeks and once per month during the following three months. Radiological analyses were carried out using a multichannel 8

analyzer coupled with a high purity germanium coaxial detector (Model GX 2518, Canberra Series, USA). Calibration was done using a mixed sealed source of the radioisotopes; 155Eu (86.5 and 105.3 keV), 57Co (122.1 and 136.5 keV), 137Cs (661.6KeV), 54Mn (834.8 KeV) and 65Zn (1115.5 KeV). The radionuclidic assessments were done by tracing the net area under the respective gamma-ray peaks.

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Results were obtained in terms of the cumulative leach fractions (CLF, cm) which were calculated according to Eq. 1 [36]: ∑ 𝐴𝑛

𝐶𝐿𝐹 = (

𝐴0

𝑉

)( )

(1)

𝑆

Where, ∑ 𝐴𝑛 is the cumulative radioactivity leached (count/min.), 𝐴𝑜 is the radioactivity initially

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present in the alkali activated specimen (count/min.), V is the volume of the specimen (cm3), and S is

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the exposed surface area of the specimen (cm2). A good binder is expected to impede leaching of the

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immobilized radionuclide(s) recording lower values of CLF (cm-1).

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2.5. Characterizations

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X-ray diffraction (XRD) patterns of the optimized ternary alkali activated blend (S4MKF3, S4MKF3-12R

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and S4MKF3-12R-γ3) were collected and compared with of the raw binders (metakaolin, feldspar and slag) using a Philips X-ray diffractometer (nickel filter of Cu Kα radiation type; λ = 1.54056 °A; 2θ range

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of 1 - 70°). Patterns were used to determine the mineralogical changes accompanying the alkali

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activation, resin loading and γ-irradiation. Scanning electron microscope (SEM; JEM-1200EX II) was used to investigate the surface morphologies S4MKF3, S4MKF3-12R and S4MKF3-12R-γ3 which

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associated to the chemical interaction between KY-2 resin and AAB matrix. Fourier transform infrared (FT-IR) spectra of S4MKF3, S4MKF-12R and S4MKF-12R-γ3 tablets mixed with KBr were recorded on Nicolet iS10 (Thermo Scientific) and compared with cold and hot KY-2 resin. The collected spectra were used to ascertain the structural bond vibrations of the ternary AAB and the loaded cold resin types as affected by γ-irradiation. 9

3. Results and discussion 3.1. Compressive strength Compressive strength experiments were carried out on the 28-days old AABs in order to investigate their mechanical integrity (Figs. 2&3). Fig 2 was conducted aiding to set the initial compositional

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conditions of the binary (Fig 2a) and ternary (Fig. 2b) formulations prior to loading of damp resin. Fig 2a optimized the mass ratio of F/MK to be up to 0.3 beyond which great effects on the ultimate

compressive strength were observed which may be due to the un-dissolved particles of feldspar [37]. Although FMK1 recorder higher strength (53 MPa) than FMK3 (50 MPa) the later was selected to be

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the optimized binary mixture especially as the reduction in compressive strength was limited to 5.65

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%. Selection was carried out on the basis of two objectives. The first is that the concentrated ASS

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could destroy the structure of feldspar providing additional system alkalinity and hence reducing the

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consumption of sodium hydroxide [38]. While the second objective was to achieve higher amounts of

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calcium silicate hydrates as a result of an expected pozzolanic reaction when adding slag. Besides

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that, different ternary mixtures were designed according to Table 2 and were alkali activated to optimize the addition of slag to FMK3 mixture. Data in Fig. 2b monitored a positive effect of adding

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slag toward improvement the compressive strength of the optimized binary formulation (FMK3).

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These results were in harmony with those obtained by Xu and van Deventer who stated that the three component geopolymer which based on fly ash, kaolinite and albite possessed the highest

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compressive strength [33]. The illustrated data in Fig. 2b revealed that the highest and the second highest compressive strength values (68.0 and 65.0 MPa) were recorded by S10FMK3 and S4FMK3 ternary formulations, respectively. Inspection of early aged S10FMK3 and S4FMK3 pastes cleared that the former was characterized by rapid setting causing significant problem to adequately cast the fresh pastes. This accelerated setting time may be due to the formation of calcium silicate hydrates in 10

conjunction with geopolymer microstructure. S4FMK3 was selected to be the optimized ternary mixture where the highest amount of feldspar (g) and comparable amounts of slag and metakaolin (g) was utilized recording non-significant difference in compressive strength, compared with S10FMK3. The efficiencies of the selected individual (FMK0), binary (FMK3) and ternary (S4FMK3) formulations

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were examined toward their abilities to solidify different ratios (6-14%) of cold KY-2 (Fig. 3). Generally, all percentages decreased the compressive strength of the three selected formulations, at different extents. The highest values which greater than twice the waste acceptance criteria (WAC; [3]) were 48.3, 48.0 and 45.2 MPa and belonged to loading of S4FMK3, FMK0 and FMK3 by 12.0, 10.0 and 8.0 %

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resin, respectively. These respective percentages were selected for the further radionuclidic leaching

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experiments.

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3.2. Leachability investigations

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3.2.1. Leached fractional activities of radionuclides

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3.2.1.1. Effect of binder type

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Experiments were designed according to the IAEA’s standard leaching test [36]. The CLFs that leached from the solidified KY-2 were varied according to type of the binder as well as type of the studied

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radionuclide (Fig. 4). In general and regardless to the binder type, all radionuclides were leached in

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greater fractions for the MC systems than for the SC ones in the following order for both systems: 152+154Eu

>134Cs >60Co. Plots of CLFs vs. time were sub-divided into three regions: I) 1-21 day in which

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the CLFs of both 134Cs and 60Co began leaching, II) 21-90 day in which 152+154Eu began leaching beside the dramatic increase in the CLF for all radionuclides and finally III) 90-120 day. The impact of binder type on CLFs was clear where S4FMK3 formulations were ranked first in lowering the leached fractional activities for all radionuclides, either in SC or MC loading systems. El-Naggar and Amin stated that the ability of metakaolin/slag-based AABs to prevent leaching of the immobilized species 11

could be attributed not only to their hardness but also to their sorption capabilities [39]. In this context, while only 0.49 % of the initial activity of SC-loaded 60Co was leached from S4FMK3 at a time when 8.05 and 39.41 % of the initial activities of SC-loaded 134Cs and 152+154Eu, were leached from FMK0 and FMK3 formulations, respectively. This may be due to the adsorptive properties of the

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evoluted calcium silicate hydrates [39]. However, which binder was ranked second or third was

dependent on the radionuclide loading type. FMK0 formulations were ranked second in both systems of 134Cs as well as the SC system of 152+154Eu. While, FMK3 formulations were ranked second in both systems of 60Co as well as the MC system of 152+154Eu, with the consequent third ranking of others.

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3.2.1.2. Effect of ɣ-irradiated binder types on the leached activities

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Fig. 5 depicts the influence of γ-irradiation on the CLFs of SC- and MC-loaded134Cs, 60Co and 152+154Eu

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from KY-2 resin which solidified into different AABs. Generally all formulations recorded higher CLFs

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of MC-loaded 134Cs and 60Co than SC-loaded ones, and vice versa regarding 152+154Eu. Likewise what

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hinted earlier in Fig. 4, plots of Fig. 5 were sub-divided into three regions in which the CLFs of 134Cs

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and 60Co started to leach earlier than those of 152+154Eu. Gamma-irradiation of the studied formulations made a desired influence where all CLFs were reduced to lowered values having inverse

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relationships with the cumulative irradiation doses. For instance, the 39.41% of the initial activity of

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SC-loaded 152+154Eu that leached from FMK3-8R formulation was reduced to 33.5, 22.18 and 13.45% when 1.0 (FMK3-8R-γ1), 2.0 (FMK3-8R-γ2) and 3.0 (FMK3-8R-γ3) KGy were applied, respectively. Since

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AABs are known to be radiation stable such desired influence of ɣ-irradiation may be due to an expected changes on the microstructure of the solidified resin beads. The subsequent SEM investigations may specifically explain the impact of gamma-irradiation on the solidified beads through the filament-like structures. 3.2.2. Effective diffusion coefficients 12

Leaching of radionuclides from a waste form may be governed by different mechanisms like diffusion, dissolution, chemical reactions and combinations thereof. Since the diffusion is a well established mechanism depicting leaching and its coefficient is a material constant for rad-waste form, IAEA suggested that these coefficients may be used to compare leaching data [40]. The quantity of

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radionuclide leached out from a unit surface area during time, tn is given by: 𝐷𝑡𝑛

𝐴𝑛 = 2𝐴𝑜 √

(2)

𝜋

Where, An is the activity leached out after time tn, Ao the initial activity in the composite and D is the diffusion coefficient, cm2/s. Hence, the cumulative leached fractions can be expressed as:

∑ 𝐴𝑛 𝐴𝑜

2𝑆𝐴𝑜 √𝐷 ∑ 𝑡𝑛

𝑆

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𝐴𝑜

𝑆

] [𝑉 ] =

𝐴𝑜 𝑉

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∑ 𝐴𝑛

𝐷 ∑ 𝑡𝑛

= 2 (𝑉) √

𝜋

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[

(3)

(4)

𝜋𝑚2 𝑉 2 4𝑆 2

(5)

D

𝐷=

M

Values of D can be calculated from the slopes m of the linear plots of (∑ 𝐴𝑛 ⁄𝐴𝑜 ) vs. √𝑡𝑛 :

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The American National Standards Institute (ANSI) defines a material parameter of the leachability of

𝛽

𝐿 = 𝑙𝑜𝑔 (𝐷)

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diffusing species. This parameter is called the leachability index, L, and is defined as [41]: (6)

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Where, β is a defined constant (1.0 cm2/s) and D is the diffusion coefficient of the species (cm2/s)

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assumed to be independent of time during the course of leaching. 3.2.2.1. Effect of binder type The effect of AAB type on plots of (∑ 𝐴𝑛 ⁄𝐴𝑜 ) vs. √𝑡𝑛 was explored (Fig. 6) for subsequent calculation of diffusion coefficients (D, cm2/s) and leachability indexes (L).The presented plots explained that all formulations behaved in initial fast and subsequent slow steps for all the designed leaching systems. 13

The calculated average values of D and their corresponding L values were given in Table 3. Generally, data in Table 3 indicated that all the studied radionuclides were diffused faster when loaded in their MC systems with exceptions of 152+154Eu, when diffused from FMK3-8R and S4FMK3-12R formulations. The S4FMK3-12R formulations exerted a notably better behavior to prevent the leaching of the

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studied radionuclides regardless their loading type. These formulations recorded the lowest D values in the order of 60Co <134Cs <152+154Eu. The FMK0-10R and FMK3-8R formulations were oscillated

between the second and third ranking depending on the radionuclide and its loading types. Regarding the radionuclide type, the former formulation was ranked second for the D values of SC-134Cs and SCWhile regarding the radionuclide loading type, ranking of the later formulation did not

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152+154Eu.

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changed from the second position for the D values of 134Cs but it was changed to the third position for

A

the D value of MC-152+154Eu. The lowest D value (2.90 × 10-12 cm2/s) was recorded by S4FMK3-12R

M

formulation, when SC-60Co was diffused. While, the highest D value (1.96 × 10-8 cm2/s) was recorded

D

by FMK3-8R formulation when SC-152+154Eu was diffused. The corresponding L values for all studied

TE

systems were calculated using Eq. 6, as listed in Table 3, and greatly exceeded the value of 6, which is the minimum value for WAC [41].

EP

3.2.2.2. Effect of ɣ-irradiated binder types on diffusivity coefficients

CC

Fig. 7 showed the effect of ɣ-irradiation doses of FMK0-10R, FMK3-8R and S4FMK3-12R formulations on the diffusion coefficients of

134Cs, 60Co

and 152+154Eu radionuclides. Likewise what observed in Fig.

A

6, data in Fig. 7 explained that ɣ-irradiation doses did not change the two-step diffusion behavior of any studied formulation. The average D values (cm2/s) were calculated according to Eq. 5 and were given in Table 4. Data in Table 4 indicated that the irradiated formulations behaved like the nonirradiated ones in the faster diffusion of radionuclides when were loaded in their MC systems with exceptions of 152+154Eu as mentioned in the earlier section. However, the effect of ɣ-irradiation doses 14

was clear in narrowing the gap between the D values (cm2/s) of SC- and MC-loading types which became narrower as the irradiation doses were increased from 1.0 to 3.0 KGy. The S4FMK3-12R formulations kept their positions of being the best in preventing the leaching of the studied radionuclides. However, the order of D values was varied depending on the radionuclide loading type

SC RI PT

to be either 60Co < 134Cs < 152+154Eu or 60Co < 152+154Eu < 134Cs for SC- or MC-loading types, respectively. The lowest D value (6.65 × 10-13 cm2/s) was recorded by S4FMK3-12R-ɣ3 formulation, when SC-60Co was diffused. While, the highest D value (1.41 × 10-8 cm2/s) was recorded by FMK3-8R-ɣ1 formulation, when SC-152+154Eu was diffused. The effect of ɣ-irradiation doses on the corresponding L values for all

N

the value of 6 but also sometimes be twice such value.

U

studied systems were calculated using Eq. 6, as listed in Table 4, that were not only greatly exceeded

A

3.3. Characterizations

M

3.3.1. XRD examinations

D

Fig. 7 showed the XRD patterns of S4FMK3, S4FMK3-12R and S4FMK3-12R-γ3 samples in comparison

TE

to raw binders. Phases were analyzed using MATCH! Software (Version 2.2.1. Build 315). The S4FMK3 was semi-crystalline in nature with a broad hump (21-39°2θ) [16, 32, 42-43]. In all samples, quartz was

EP

the predominant crystalline phase which was detected at different 2θ degrees with varied intensities.

CC

Also other minerals were detected (albite, hematite, kaolinite and microcline) with different quantities along samples. Absence of kaolinite mineral in metakaolin sample confirmed its high

A

reactivity. Detection of albite and microcline phases in AABs may indicate the presence of un-reacted feldspar forms which may affect on the ultimate compressive strength. Loading of the S4FMK3 sample with the tested resin type (S4FMK3-12R and S4FMK3-12R-γ3) not only increased the broadness of the amorphous hump (21-39°2θ) but also increased its height from the base line. This may be due to the amorphous nature the tested resin type that made patterns to be noisy. The effect of ɣ-irradiation 15

was obvious through the slight shift of quartz peaks to higher degrees. This may be attributed to the expected formation of the smoky quartz which is a common form of quartz due to high energetic ɣrays. 3.3.2. FT-IR examinations

SC RI PT

The optimized S4FMK3 and their cold resin-loaded formulations (S4FMK3-12R and S4FMK-12R-γ3) were qualitatively analyzed by FT-IR technique and compared with loaded and unloaded KY-2 resin beads (Fig. 8). All the structural vibrations of S4FMK3 were presented in Fig. 8a. No significant

differences between loaded and un-loaded resin beads were detected in Fig. 8 d&e. Bands arising at

U

688 cm-1 may be assigned to the formation of AlIV as an essential component in the geopolymeric

N

environment [11] or phenyl out-of-plane bending vibrations. The stretching and bending vibrations of

A

Si – O – Si were observed at 585 and 450 cm-1, respectively [16]. Loading of the sulphonated

M

polystyrene divinyl benzene resin into the optimized mixed AABs led to overtones at several

D

wavenumbers (Fig 8 b&c). The aromatic C=C vibrations are usually detected around 1600, 1490 and

TE

1440 cm-1 [44]. Fig. 8b&c showed that the three characteristic stretches of the aromatic C=C were detected at lower wavenumbers which may be due to the sulphonate group para-substitution. Two

EP

bands of them made overtones with the stretching vibrations of carbonate group (1457 cm-1) and the

CC

bending vibrations of the physically adsorbed water (1658 cm-1). While, the third band of the aromatic C=C was detected at 1412 cm-1. Another overtone was observed (Fig. 8b-e) as a very sharp and broad

A

band with two maxima at 1032 and 1011 cm-1 (symmetrical stretches of S=O and Si – O – Al, respectively) and sifted shoulders at 1140 cm-1 (asymmetrical stretches of S=O). Bands arising at 835 cm-1 (Fig. 8 d&e) may be due to the C – H out of the plane of the para-disubstituted aromatic ring which were shifted to lower wavenumbers (867 cm-1; Fig. 8 b&c) due the alkaline activation of binders. Bands arising at 1182 cm-1 (Fig. 8d&e) may be assigned to asymmetrical stretches of S=O. 16

Bands arising at 775 and 421 cm-1 may be due to the aromatic C – H out-of-plane deformation and the SO2 twisting vibrations, respectively. The appearance of the broad band at 2284-2343 cm-1 proofed the presence of sulphonate group in its hydrated form (–SO3-…H3O+). The observed very weak bands arising at 2921-2860 cm-1 may be attributed to the stretching vibrations of CH2 in the alkyl polymeric

SC RI PT

chain. A very broad and sharp bands were observed at 3462 cm -1 which may be due to the

symmetrical stretching vibrations of O – H bonding alone (Fig. 8a) or overlapped with the aromatic C– H stretchings (Fig. 8 b&c). The destructive effect of gamma irradiation was clear in reducing all

skeletal vibrations of the loaded resin. This was accompanied by no changes in the intensities of

U

structural geopolymeric bands reflecting a radiation stability of the examined alkali activated binder

N

mixture.

A

3.3.3. SEM examination

M

The microstructural features of S4FMK3, S4FMK3-12R and S4FMK3-12R-γ3 ternary AABs were shown

D

in Fig. 9 a-i. The surface morphologies of the optimized resin-free formulation (S4FMK3) were

TE

displayed in Fig. 9 a-c. The muli-layered structures, with their interfaces between them, were distinguished via their densifications. These layers were of better homogeneity, continuity (crack

EP

diameter of 0.24-1.11 µm) and less amounts of un-reacted raw materials constituting an alkali

CC

activated binder mixture of good quality [11]. As an organic damp resin was loaded (S4FMK3-12R; with no applied ɣ-irradiation) the surface morphologies were changed to be rough with projections of

A

different diameters (Fig. 9 d-f) which may be due to the wrapping of the loaded resin with geopolymeric structures. Also, larger porous cracks (0.52-5.39 µm) left by the evaporation of water, which was included into the solidified damp resin, were observed with their un-favored effects on the continuity of the matrix. These observations may interpret why the compressive strength of formulations were decreased upon loading the resin in its damp form. The effect of ɣ-irradiation (3.0 17

KGy cumulative dose) on the resin loaded formulations (S4FMK3-12R-γ3; Fig. g-i) was great. Such micrographs clarified the shape transformation of the solidified resin, along three stages, from spherical to filamentous. During the first stage (Fig. 9 g) resin particles were erupted to form blowzylike structures which emit protrusions (< 2.91 µm) during the second stage (Fig. 9 h). Finally, such

SC RI PT

protrusions were transformed into microfilaments having diameters less than 0.51 µm (Fig. 9 i). These microfilaments may play a crucial role in filling the porous micro-cracks addressing their adverse effects on leaching of the immobilized radionuclides. 4. Summary and Conclusions

U

Optimization efforts on metakaolin (MK), feldspar (F) and blast furnace slag (S) have done to produce

N

individual (MK-based; FMK0), binary (𝐹 ⁄𝑀𝐾 = 0.3; FMK3) and ternary (𝑆⁄(𝐹 + 𝑀𝐾)= 0.4; S4FMK3)

A

AABs suitable for direct solidification nuclear grade cationic resin (KY-2). Uncontaminated (cold) and

M

radionuclide-contaminated (hot) KY-2 beads were laboratory-elaborated and utilized for compressive

D

strength and leaching investigations, respectively. Cold resin beads could be solidified into S4FMK3,

TE

FMK0 and FMK3 by 12.0 (S4FMK3-12R), 10.0 (FMK0-10R) and 8.0% (FMK3-8R) yielding compressive strength values (48.3, 48.0 and 45.2 MPa, respectively) of twice the waste acceptance criteria. and

152+154Eu

radionuclides were used to prepare single- (SC) and multi-component (MC) hot

EP

60Co

134Cs,

CC

resin beads for leacing investigations. Regardless the binder type, all radionuclides were leached in greater fractions for the MC systems than for the SC ones in the following order for both systems: > 134Cs > 60Co. S4FMK3-12R formulations were ranked first in lowering the leached fractional

A

152+154Eu

activities for all studied systems. Regarding SC systems, only 0.49 % of the initial activity of leached from S4FMK3-12R at a time when 8.05 and 39.41 % of the initial activities of 152+154Eu

60Co

was

134Cs

and

were leached from FMK0-10R and FMK3-8R formulations, respectively. ɣ-irradiation of the

studied systems made a desired influence where all CLFs were reduced to lowered values having 18

inverse relationships with the applied cumulative irradiation doses. S4FMK3-12R formulations recorded the lowest values of diffusion coefficients (D, cm2/s) in the order of

60Co

<134Cs <152+154Eu.

Gamma irradiation doses narrowed the gap between the D values of the SC and MC systems which became narrower as the irradiation doses were increased from 1.0 to 3.0 KGy. S4FMK3, S4FMK3-12R

SC RI PT

and S4FMK3-12R- ɣ3 were characterized using XRD, FT-IR and SEM techniques. Their semi-crystalline natures were observed in XRD patterns with the associated quartz, albite, gehlenite, hematite, kaolinite and microcline minerals. Visual comparison of FT-IR spectral intensities reflected to what extent the resin-free ternary formulation was radiation stable and the radiation stability of the

U

solidified KY-2 resin was poor. SEM examinations detected interfered multi-layer structures of better

N

homogeneity and continuity which were changed to be rough with projections of different diameters

A

upon solidification of KY-2 resin. The effect of ɣ-irradiation on such solidified resin was great where a

M

desired three-step shape transformation was detected. The performance of the studied AAB revealed

D

that it can be utilized as an alternative to OPC for solidification of spent ion exchange resins due to

TE

their radiation stability, higher compressive strength values and lower leached fractional activities. All binders behaved well especially ternary ones. Thus, future studies will be appropriated toward

EP

examination of such binders in pilot scales.

CC

Acknowledgments

Authors are acknowledged members of the Rad-waste Management and the Radioactive Isotopes &

A

Generators Depts., Hot-Lab. Center, Egyptian Atomic Energy Authority.

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SC RI PT

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[4] M.R. El-Sourougy, M.I. El-Dessouky, H.F. Aly, Assessment of some ion exchangers for the treatment of low-level radioactive liquid waste solutions, Arab J. Nucl. Sci. Appl. 27(3) (1994) 75-88.

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study of geopolymers obtained from alkali-activated natural pozzolan feldspars, Ceram. Int. 43 (2017)

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[19] G. Ascensão, M.P. Seabra, J.B. Aguiar, J.A. Labrincha, Red mud-based geopolymers with tailored alkali diffusion properties and pH buffering ability, J. Cleaner Prod. 148 (2017) 23-30. [20] A. Vásquez, V. Cárdenas, R.A. Robayo, R. Mejía de Gutiérrez, Geopolymer based on concrete demolition waste, Adv. Powder Technol. 27 (2016) 1173-1179.

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[21] L.N. Tchadjié, J.N.Y. Djobo, N. Ranjbar, H.K. Tchakouté, B.B.D. Kenne, A. Elimbi,D. Njopwouo, Potential of using granite waste as raw material for geopolymer synthesis, Ceram. Int. 42 (2016) 30463055. [22] X.Y. Zhuang, L. Chen, S. Komarneni, C.H. Zhou, D.S. Tong, H.M. Yang, W.H. Yu, H. Wang, Fly ash-

SC RI PT

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glass and ceramics industries, Minerals Engineering 7(9) (1994) 1193-1201.

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(Cr2O72−, MnO4−and Fe(CN)63−) in metakaolin based geopolymers: a preliminary study, Ceram. Int. 44

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using fly ash-based geopolymer with chemical agents, Constr. Build. Mater. 151 (2017) 394-404. [28] B.I. El-Eswed, O.M. Aldagag, F.I. Khalili, Efficiency and mechanism of stabilization/solidification of

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Pb(II), Cd(II), Cu(II), Th(IV) and U(VI) in metakaolin based geopolymers, Appl. Clay Sci. 140 (2017) 148 156.

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[30] Q. Li, Z. Sun, D. Tao, Y. Xu, P. Li, H. Cui, J. Zhai, Immobilization of simulated radionuclide 133Cs+ by fly ash-based geopolymer, J. Hazard. Mater. 262 (2013) 325-331. [31] V. Cantarel, F. Nouaille, A. Rooses, D. Lambertin, A. Poulesquen, F. Frizon, Solidification/ stabilisation of liquid oil waste in metakaolin-based geopolymer, J. Nucl. Mater. 464 (2015) 16-19.

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Dukovany Nuclear Power Plant, Czech Republic-12367, WM Conference, Phoenix2012, Direct

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investigations of cesium and strontium adsorption onto clay of radioactive waste disposal, Appl. Clay

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[41] American Nuclear Society Standards committee, Measurement of the leachability of solidified

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low level radioactive wastes by a short term test procedure, ANSI/ANS-16.1-1986, American Nuclear

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[43] Q. Wan, F. Rao, S. Song, R.E. García, R.M. Estrella, C.L. Patiňo, Y. Zhang,Geopolymerization reaction, microstructure and simulation ofmetakaolin-based geopolymers at extended Si/Al ratios,

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[44] A.R. Katritzky and R.A. Jones, Infrared absorption of heteroaromatic and benzenoid sixmembered, monocyclic nuclei: Part IX. Ortho- disubstituted benzenes. J. Chem. Soc., 1959, 3670-

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24

SC RI PT

Fig. 1. Photographs of damp KY-2 resin-loaded (a) cold cubes (40 × 40 × 40 mm) of FMK3-8R and S4FMK3-12R and (b) 48-hot tablets (15 × 10 mm) of individual, binary and ternary matrices. Cold

A

CC

EP

TE

D

M

A

N

U

samples contain non-radioactive damp resin while hot ones contain damp resin spiked with134Cs,60Co, 152+154Eu radionuclides or their mixture.

25

80 (a)70 (b) 60 50 40 WAC 30 20 10 FMK0 FMK1 FMK3 FMK4 FMK100 Binder mix design S0FMK3 S1FMK3 S3FMK3 S4FMK3 S10FMK3 Fig. 2. 28-days compressive strength (MPa) of different binary (a) and ternary (b) alkali activated

SC RI PT

Compressive strength, MPa

80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0

-12R

-14R

TE

WAC

EP

18.0 12.0 6.0 0.0

-10R

D

54.0 48.0 42.0 36.0 30.0 24.0

-8R

A

-6R

M

72.0 66.0 60.0

CC

Compressive strength, MPa

N

U

binders. WAC: waste acceptance criteria.

FMK0

FMK3

S4FMK3

Binder mix design

A

Fig. 3. Effect of KY-2 resin addition (%) on 28-days compressive strength (MPa) of individual, binary and ternary alkali activated binders. FMK0: individual MK; FMK3: binary of F/MK = 0.3; S4FMK3: ternary of F/MK = 0.3 & S/(F+MK)=0.4; WAC: waste acceptance criteria.

26

0.27

FMK0-10R FMK3-8R S4FMK3-12R

0.020

MC-loading

(a)

FMK0-10R FMK3-8R S4FMK3-12R

0.018

(I) (II)

0.12

(III)

CLF, cm-1

0.18

0.45 0.40

0.014

0.35

0.012

0.30

0.010

(I)

(II)

0.008

0.09

0.006

0.06

0.004

0.03

0.002

0.00

(b)

FMK0-10R FMK3-8R S4FMK3-12R

(II)

0.25

SC-loading

MC-loading

(I)

(c)

FMK0-10R FMK3-8R S4FMK3-12R

FMK0-10R FMK3-8R S4FMK3-12R

(III)

(II)

0.20 0.15 0.10 0.05

0.000

0.00

0 10 20 30 40 50 60 70 80 90 100 110 120 130

0 10 20 30 40 50 60 70 80 90 100 110 120 130

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Time, day

Time, day

Time, day

Fig. 4. Effect of alkali activated binder type on the cumulative fractional activities of a)

134Cs,

b) 60Co

CC

EP

TE

D

M

A

N

U

and c) 152+154Eu leached from solidified KY-2 damp resin.MC = multiple component; SC = singular component.

A

CLF, cm-1

0.21

0.50

MC-loading

FMK0-10R FMK3-8R S4FMK3-12R

0.016

0.24

0.15

SC-loading

CLF, cm-1

0.30

SC-loading

SC RI PT

0.33

27

SC-loading MC-loading 0.20 FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R- 0.18 FMK3-8R- FMK3-8R-

(a)

0.18

0.14

0.14

0.14

0.10

(I)

0.08 0.06

(III)

(II)

0.04

0.02

0.00

0.00

0.018

SC-loading FMK0-10R-1 FMK0-10R- FMK0-10R-

0.016 0.014

Time, day MC-loading FMK0-10R- FMK0-10R- FMK0-10R-

0.016 0.014

Time, day SC-loading MC-loading FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R-

0.018

(e)

0.014

0.006

0.004

0.004

0.002

0.002 0.000

0.000

0.28

0.36 0.32 0.28

0.24

(III)

EP

0.20

(II)

0.16

0.08 0.04 0.00

CC

0.12

CLF, cm-1

(I)

0.24 0.20

SC-loading FMK3-8R- FMK3-8R- FMK3-8R- MC-loading FMK3-8R- FMK3-8R- FMK3-8R-

0.006

Time, day SC-loading MC-loading S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R-

U

0.40

(h)

0.36 0.32

(i)

0.28

(II)

(III) 0.24

(I)

0.20

(II)

(III)

0.16 0.12

(I)

0.08

0.08

0.04

0.04 0.00

0.00 0 10 20 30 40 50 60 70 80 90 100 110 120 130

Time, day

Time, day

A

0.008

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Time, day

0 10 20 30 40 50 60 70 80 90 100 110 120 130

0

10 20 30 40 50 60 70 80 90 100 110 120 130

Time, day

Fig. 5. Effect of different doses of γ-irradiation on cumulative fractional activities of (a-c) 60Co

(III)

0.000

0.16 0.12

(II)

0.002

D

0.32

(g)

TE

0.36

0.40

(I)

0.004

CLF, cm-1

Time, day SC-loading MC-loading FMK0-10R-1 FMK0-10R- FMK0-10R- FMK0-10R- FMK0-10R- FMK0-10R-

(III)

Time, day SC-loading MC-loading S4FMK3-12R- S4FMK3-12R- (f) S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R-

0.010

0 10 20 30 40 50 60 70 80 90 100 110 120 130

0 10 20 30 40 50 60 70 80 90 100 110 120 130 0.40

(II)

(I) 0.008

N

0.006

0.010

A

(III)

(II)

0.008

0.016

0.012

M

(I)

CLF, cm-1

0.010

0 10 20 30 40 50 60 70 80 90 100 110 120 130

10 20 30 40 50 60 70 80 90 100 110 120 130

0.012

0.012

(III)

0.00

0.018

(d)

(II)

0.02

0

0 10 20 30 40 50 60 70 80 90 100 110 120 130

(I)

0.08

0.04

0.04

0.02

0.10

0.06

(III)

(II)

(c)

0.12

SC RI PT

(I)

0.08

0.12

CLF, cm-1

0.10

CLF, cm-1

0.16

0.12

SC-loading MC-loading S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R-

0.20

0.16

0.06

CLF, cm-1

(b)

0.16

CLF, cm-1

CLF, cm-1

MC-loading SC-loading 0.20 FMK0-10R-1 FMK0-10R- FMK0-10R- FMK0-10R- 0.18 FMK0-10R- FMK0-10R-

CLF, cm-1

0.22

0.22

0.22

134Cs,

(d-f)

and (h-j) 152+154Eu leached from FMK0-10R, FMK3-8R and S4FMK3-12R formulations. MC = multiple

component; SC = singular component.

28

0.030 0.027

0.00150

SC-loading FMK0-10R FMK3-8R S4FMK3-12R

MC-loading FMK0-10R FMK3-8R S4FMK3-12R

0.00135

MC-loading

FMK0-10R FMK3-8R S4FMK3-12R

0.00120

(b)

FMK0-10R FMK3-8R S4FMK3-12R

0.033 0.030 0.027

0.00105

0.024 An/Ao

0.021 0.018 0.015

0.00075 0.00060

0.012

SC-loading FMK0-10R FMK3-8R S4FMK3-12R

MC-loading FMK0-10R FMK3-8R S4FMK3-12R

(c)

0.024

0.00090

0.021 0.018 0.015 0.012

0.00045

0.009

0.009

0.00030

0.006 0.003

0.00015

0.000

0.00000

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

0.006 0.003 0.000

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

Fig. 6. Fractional activities vs. square root of time for a)

134Cs,

b) 60Co and c)

U

t , day

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

t1/2, day

t1/2, day

1/2

152+154Eu

leached from

CC

EP

TE

D

M

A

N

FMK0-10R, FMK3-8R and S4FMK3-12R formulations. MC = multiple component; SC = singular component.

A

An/Ao

0.036

SC-loading

(a)

An/Ao

0.033

SC RI PT

0.036

29

0.016

MC-loading FMK0-10R- FMK0-10R- FMK0-10R-

SC-loading FMK0-10R-1 FMK0-10R- FMK0-10R-

0.014 0.012

0.016 0.014 0.012

0.004

0.004

0.002

0.002

An/Ao

0.004 0.002 0.000

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

t1/2, day

t1/2, day 0.0010

0.0007

N

0.0005

0.0006 0.0005 0.0004

0.0003

0.0003

0.0002

0.0002

0.0001

0.0001

D

0.0004

0.0000

(e)

0.0009 0.0008

t1/2, day

0.024

(g)

0.015

CC

0.012

An/Ao

0.018

0.009 0.006

A

0.003

0.027 0.024

EP

0.021

MC-loading FMK0-10R- FMK0-10R- FMK0-10R-

0.0002 0.0001 0.0000 -0.0001

t1/2, day

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

SC-loading MC-loading FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R-

0.030

(h)

0.027 0.024

0.021

0.021

0.018

0.018

0.015 0.012

t1/2, day

SC-loading MC-loading S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R-

0.012 0.009

0.006

0.006

0.003

0.003 0.000 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

t1/2, day

t1/2, day

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

t1/2, day

Fig. 7. Effect of different doses of γ-irradiation on fractional activities of SC- and MC-loaded (a-c) 134Cs, (d-f)

60Co

and (h-j)

152+154Eu

(I)

0.015

0.009

0.000

0.000

0.0004 0.0003

An/Ao

SC-loading FMK0-10R-1 FMK0-10R- FMK0-10R-

0.027

0.030

(f)

0.0005

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

TE

0.030

SC-loading SC-loading S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R-

0.0007

0.0000

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

t1/2, d

0.0006

A

0.0006

0.0008

SC-loading MC-loading FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R-

0.0010

M

0.0007

0.0009

An/Ao

0.0008

(d)

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

U

0.0010

SC-loading FMK0-10R-1 FMK0-10R- FMK0-10R- MC-loading FMK0-10R- FMK0-10R- FMK0-10R-

0.008 0.006

0.000

0.0009

SC RI PT

0.006

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

An/Ao

0.012

(c)

0.010

0.008

0.006

0.000

An/Ao

0.014

An/Ao

0.008

SC-loading MC-loading S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R- S4FMK3-12R-

(b)

0.010 An/Ao

An/Ao

0.010

0.016

SC-loading MC-loading FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R- FMK3-8R-

(a)

leached from FMK0-10R, FMK3-10R and S4FMK-12R formulations, vs.

square root of time. MC = multiple component; SC = singular component. 30

SC RI PT U N A M D TE EP CC A Fig.7. XRD patterns of raw materials (metakaolin, feldspar and blast furnace slag) in comparison to S4FMK3, S4FMK3-12R and S4FMK3-12R-γ3 ternary formulations, after 28-days curing time. 31

SC RI PT

(e)

835

(d) (c)

1182

2343

(b) 2284

867

(a)

U

2860

1412

A

N

2921

4000

3600

3200

M

3462

2800

2400

421

775 688

1457 1658 1140 1032

2000

1600

1200

585 1011

800

450

400

-1

D

Wavenumber, cm

A

CC

EP

TE

Fig. 8. FT-IR spectra of (a) S4FMK3, (b) S4FMK-12R and (c) S4FMK3-12R-γ3 ternary formulations, after 28-days curing time, in comparison to (d) unloaded and (e) loaded KY-2. (b) and (c) were loaded with cold damp resin.

32

SC RI PT U N A M D TE EP CC A

Fig. 9. Micrographs of S4FMK3 (a-c), S4FMK-12R (d-f) and S4FMK3-12R-γ3 (g-i) ternary formulations, after 28-days curing time. AS = alkaline silicates; A-S-H = aluminosilicate hyrates; C-S-H = calcium silicate hydrates.

33

Table 1. Analysis of a ground water sample obtained from Bilbies geological formation [34-35].

M

A

TE EP CC A

34

Ground water 0.620 7.100 800.0 531.0 320.0 230.0 90.00 284.0 284.0 0.00 0.00 99.70 36.00 0.00 3.700 78.00 92.10 21.90 < 0.01 0.306

SC RI PT U

N

Unit NTU µS/cm mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l µg/l mg/l mg/l mg/l mg/l mg/l

D

Parameters Turbidity pH Electric conductivity Total Dissolved Solids Total Hardness (CaCO3) Calcium Hardness (CaCO3) Magnesium Hardness (CaCO3) Total Alkalinity Bicarbonate(𝐻𝐶𝑂3− ) Carbonate(𝐶𝑂32− ) Hydroxide(𝑂𝐻 − ) Sulfate(𝑆𝑂42− ) Chloride (𝐶𝑙 − ) Nitrite(𝑁𝑂2− ) Nitrate (𝑁𝑂3− ) Sodium (𝑁𝑎+ ) Calcium (𝐶𝑎2+ ) Magnesium (𝑀𝑔2+ ) Total iron Manganese(𝑀𝑛2+ )

Table 2. Designs of individual, binary and ternary blends of metakaolin, feldspar and blast furnace slag. Ratios between binders

Σ γirradiation dose, KGy

Group

Symbol

Feldspar Metakaolin

GI

FMK0 (pure metakaolin) FMK1 FMK3 FMK4 FMK10

0.0 0.1 0.3 0.4 1.0

0.0 0.0 0.0 0.0 0.0

0.0 0.0 0.0 0.0 0.0

0.0 0.0 0.0 0.0 0.0

S0FMK3 S1FMK3 S3FMK3 S4FMK3 S10FMK3 FMK0-6R FMK0-8R FMK0-10R FMK0-12R FMK0-14R

0.3 0.3 0.3 0.3 0.3 0.0 0.0 0.0 0.0 0.0

0.0 0.1 0.3 0.4 1.0 0.0 0.0 0.0 0.0 0.0

0.0 0.0 0.0 0.0 0.0 6.0 8.0 10.0 12.0 14.0

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

FMK3-6R FMK3-8R FMK3-10R FMK3-12R FMK3-14R

0.3 0.3 0.3 0.3 0.3

0.0 0.0 0.0 0.0 0.0

6.00 8.00 10.0 12.0 14.0

0.0 0.0 0.0 0.0 0.0

0.3 0.3 0.3 0.3 0.3 0.0 0.0 0.0 0.0

0.4 0.4 0.4 0.4 0.4 0.0 0.0 0.0 0.0

6.00 8.00 10.0 12.0 14.0 10.0 10.0 10.0 10.0

0.0 0.0 0.0 0.0 0.0 0.0 1.0 2.0 3.0

FMK3-8R FMK3-8R-γ1 FMK3-8R-γ2 FMK3-8R-γ3

0.3 0.3 0.3 0.3

0.0 0.0 0.0 0.0

8.00 8.00 8.00 8.00

0.0 1.0 2.0 3.0

S4FMK3-12R S4FMK3-12R-γ1 S4FMK3-12R-γ2 S4FMK3-12R-γ3

0.3 0.3 0.3 0.3

0.4 0.4 0.4 0.4

12.0 12.0 12.0 12.0

0.0 1.0 2.0 3.0

A

SC RI PT

U N A

M D TE

CC

G III

S4FMK3-6R S4FMK3-8R S4FMK3-10R S4FMK3-12R S4FMK3-14R FMK0-10R FMK0-10R-γ1 FMK0-10R-γ2 FMK0-10R-γ3

EP

G II

Blast furnace slag Resin, % Feldspar + Metakaolin

F = feldspar; MK = metakaolin; S = blast furnace slag

35

Table 3. Effects of alkali activated binder type on diffusion coefficients and leachability indexes of 134Cs, 60Co

and 152+154Eu leached from FMK0-10R, FMK3-8R and S4FMK3-12R formulations. Diffusion coefficient, D (cm2/s)

FMK3-8R

S4FMK3-12R

134Cs

60Co

152+154Eu

SC

7.34E-10

4.36E-12

5.91E-9

MC

5.97E-9

3.00E-11

1.14E-8

SC

7.78E-10

3.53E-12

1.96E-8

MC

8.09E-9

2.18E-11

5.85E-9

SC

6.54E-10

2.90E-12

3.21E-9

MC

4.02E-9

1.94E-11

1.09E-9

A

CC

EP

TE

D

M

A

N

MC = multiple component loading; SC = singular component loading.

36

134Cs

60Co

152+154Eu

SC RI PT

FMK0-10R

Radionuclide loading type

U

Formulation

Leachability index, L

9.13

11.36

8.23

8.22

10.52

7.94

9.12

11.45

7.71

8.09

10.66

8.23

9.18

11.54

8.49

8.40

10.71

8.69

Table 4. Effect of γ-irradiation dose on diffusion coefficients and leachability indexes of 134Cs, 60Co and 152+154Eu

leached from FMK0-10R, FMK3-8R and S4FMK3-12R formulations.

Formulation

Radionuclide loading type

Irradiation dose, KGy

Diffusion coefficient, D(cm2/s)

FMK3-8R

8.77

2.00

1.14E-10 2.70E-12 1.57E-9

9.94

11.57

8.80

3.00

9.34E-11 1.70E-12 1.18E-9

10.03

11.77

8.93

1.00

2.90E-9 1.76E-11 5.85E-9

8.54

10.76

8.23

2.00

2.22E-9 9.81E-12 4.86E-9

8.65

11.01

8.31

3.00

1.18E-9 7.82E-12 2.65E-9

8.93

11.11

8.57

1.00

7.69E-10 2.98E-12 1.41E-8

9.11

11.53

7.85

2.00

2.24E-10 1.77E-12 5.67E-9

9.65

11.75

8.25

3.00

2.04E-10 7.52E-13 1.86E-9

9.69

12.12

8.73

1.00

3.30E-9 1.60E-11 5.26E-9

8.48

10.80

8.28

2.53E-9 8.48E-12 3.35E-9

8.60

11.07

8.48

3.00

2.04E-9 3.21E-12 1.41E-9

8.69

11.49

8.85

1.00

3.70E-10 2.15E-12 1.60E-9

9.43

11.67

8.80

2.00

7.86E-11 1.67E-12 1.24E-9

10.10

11.78

8.91

3.00

5.61E-11 6.65E-13 9.08E-10 10.25

12.18

9.04

1.00

2.65E-9 1.29E-11 9.84E-10

8.58

10.89

9.01

2.00

1.83E-9 5.24E-12 7.32E-10

8.74

11.28

9.13

3.00

9.73E-10 1.06E-12 2.23E-10

9.01

11.97

9.65

2.00

MC

A

CC

S4FMK3-12R

EP

SC

U

11.43

TE

MC

152+154Eu

9.20

N

SC

60Co

6.29E-10 3.71E-12 1.70E-9

A

MC

134Cs

1.00

M

FMK0-10R

152+154Eu

D

SC

60Co

SC RI PT

134Cs

Leachability index, L

37