Borehole RW Disposal Concept and Prospects of its Implementation in Russia

Kochkin, B. T.; Bogatov, S. A.

doi:10.25283/2587-9707-2022-2-85-99

Cited by 4 publications

(10 citation statements)

References 8 publications

(13 reference statements)

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“…Advantages of boreholes for high-level heat-generating waste disposal, including that of the REE-MA fraction, are as follows [106,110,115,121]: long-term safety due to the large depth of disposal; economical access to rocks with high insulating properties; low infrastructure requirements and small area of ground structures; short construction time, waste loading and sealing of the storage facility; the possibility of creating waste near the site of waste generation; low probability of unauthorized access; minimal control after the facility is closed; high water salinity, which prevents convection due to heat released by HLW; low solubility of actinides under reducing conditions; and instability of the colloids in brines.…”

Section: Discussionmentioning

confidence: 99%

“…However, long periods (30-50 or more years) from the start of searching for sites for a mine disposal facility to the start of its construction [103] make the alternative option of HLW disposal in deep boreholes attractive [104][105][106][107][108][109][110][111]. The first nuclear-waste storage facility in deep boreholes can be created within five to ten years [105], which is an order of magnitude shorter than the construction time of traditional mine storage facilities.…”

Section: Assessment Of the Possibility For Deep-borehole Disposal Of ...mentioning

confidence: 99%

“…The preferred types of HLW forms for placement into deep wells [108][109][110][111][112][113][114][115] are waste with high heat release, including chlorides and fluorides of Cs and Sr; cesium-strontium fractions; actinide-containing waste in a stable matrix, including Pu-containing waste; and the REE-actinide fraction of HLW. The advantages of the borehole disposal of HLW over mines include the following: long-term safety due to the large burial depth and extremely low solubility of actinides under reducing conditions; economical access to rocks with high insulating properties; lower infrastructure requirements and significantly smaller surface area; shorter terms of construction and placement of HLW; significantly lower cost; the possibility of creating waste in close proximity to the place of waste generation; extremely low probability of unauthorized access to radioactive materials; minimal control after HLW placement and storage-facility closure.…”

Section: Assessment Of the Possibility For Deep-borehole Disposal Of ...mentioning

confidence: 99%

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Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

Yudintsev,

Ojovan,

Malkovsky

2024

J. Compos. Sci.

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The current policy of managing high-level waste (HLW) derived in the closed nuclear fuel cycle consists in their vitrification into B-Si or Al-P vitreous forms. These compounds have rather limited capacity with respect to the HLW (5–20 wt%), and their properties change over time due to devitrification of the glasses. Cardinal improvement in the management of HLW can be achieved by their separation onto groups of elements with similar properties, followed by their immobilization in robust waste forms (matrices) and emplacement in deep disposal facilities. One of the possible fractions contains trivalent rare-earth elements (REEs) and minor actinides (MAs = Am and Cm). REEs are the fission products of actinides, which are mainly represented by stable isotopes of elements from La to Gd as well as Y. This group also contains small amounts of short-lived radionuclides with half-lives (T1/2) from 284 days (144Ce) to 90 years (151Sm), including 147Pm (T1/2 = 2.6 years), 154Eu (T1/2 = 8.8 years), and 155Eu (T1/2 = 5 years). However, the main long-term environmental hazard of the REE–MA fraction is associated with Am and Cm, with half-lives from 18 years (244Cm) to 8500 years (245Cm), and their daughter products: 237Np (T1/2 = 2.14 × 106 years), 239Pu (T1/2 = 2.41 × 104 years), 240Pu (T1/2 = 6537 years), and 242Pu (T1/2 = 3.76 × 105 years), which should be immobilized into a durable waste form that prevents their release into the environment. Due to the heat generated by decaying radionuclides, the temperature of matrices with an REE–MA fraction will be increased by hundreds of centigrade above ambient. This process can be utilized by selecting a vitreous waste form that will crystallize to form durable crystalline phases with long-lived radionuclides. We estimated the thermal effects in a potential REE–MA glass composite material based on the size of the block, the content of waste, the time of storage before immobilization and after disposal, and showed that it is possible to select the waste loading, size of blocks, and storage time so that the temperature of the matrix during the first decades will reach 500–700 °C, which corresponds to the optimal range of glass crystallization. As a result, a glass–ceramic composite will be produced that contains monazite ((REE,MA)PO4) in phosphate glasses; britholite (Cax(REE,MA)10-x(SiO4)6O2) or zirconolite ((Ca,REE,MA)(Zr,REE,MA)(Ti,Al,Fe)2O7), in silicate systems. This possibility is confirmed by experimental data on the crystallization of glasses with REEs and actinides (Pu, Am). The prospect for the disposal of glasses with the REE–MA fraction in deep boreholes is briefly considered.

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Section: Discussionmentioning

confidence: 99%

Section: Assessment Of the Possibility For Deep-borehole Disposal Of ...mentioning

confidence: 99%

Section: Assessment Of the Possibility For Deep-borehole Disposal Of ...mentioning

confidence: 99%

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Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

Yudintsev,

Ojovan,

Malkovsky

2024

J. Compos. Sci.

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“…Образование значительных объемов высокоактивных отходов (ВАО) при переработке отработавшего ядерного топлива (ОЯТ) (варианты PUREX-процесса 1 ) является препятствием для широкомасштабного развития современной ядерной энергетики [1,2]. Согласно рекомендациям Международного агентства по атомной энергии 2 и действующим нормативным актам стран, эксплуатирующих атомные электростанции, жидкие ВАО подлежат кондиционированию с целью сокращения объема и перевода в конечную форму, пригодную для экологически безопасного длительного хранения и захоронения в геологические формации на глубине не менее 500 м [1][2][3][4][5]. Получаемая матрица должна обладать химической, термической и радиационной устойчивостью, сохранять изолирующую способность на протяжении не менее 1000 лет 3 .…”

Section: Introductionunclassified

“…Расшифровку рентгенодифракционных данных и идентификацию фаз осуществляли в программном пакете Match! (Crystalimpact Gmbh, Германия) и базе данных ICDD-2 5 .…”

Section: Introductionunclassified

A study of the mechanical and thermophysical properties of crystal matrices for the immobilization of high-level wastes

Kuznetsov,

Zobkova,

Kalenova

et al. 2024

Fine Chem. Technol.

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Objectives. The aim of the study was to confirm the compliance of the mechanical and thermophysical properties of titanate-zirconate mineral-like matrices intended for immobilization of the rare-earth-actinide fraction of high-level waste (HLW) with pyrochlore structures (Nd2ZrTiO7) and orthorhombic titanate of rare earth elements (Nd4Ti9O24+TiO2) with the Russian requirements for the final forms of radioactive waste sent for disposal. With regard to fractionated radioactive waste, this type of matrix is preferable when compared with conservative aluminophosphate and borosilicate glasses. This is due to larger capacity, and a better level of chemical, thermal, and radiation resistance.Methods. The synthesis of mineral-like matrices was carried out by remelting a granular precursor consisting of mineral-forming metal oxides and a solution imitating the rare earth-actinide fraction of HLW in an induction furnace with a cold crucible. The thermal diffusivity was determined by the laser flash method. The heat capacity of the matrix samples was measured by differential scanning calorimetry. Ultimate flexural and compressive strengths were determined using universal test machines. The elastic moduli (Young’s) were measured by the acoustic method. The temperature coefficients of linear expansion were determined using a high-temperature dilatometer.Results. The ultimate strength of the matrices (Nd2ZrTiO7) and (Nd4Ti9O24+TiO2) was found to be 150–179 and 20.6–57.8 MPa in compression and bending respectively. Young’s moduli vary from 3.7 ∙ 107 to 2.15 ∙ 108 kN/m2. With an increase in temperature from 50 to 500°C, the values of thermal conductivity have a pronounced tendency to decrease from 1.71 to 0.91 W/(m∙K). The temperature coefficients of linear expansion increase from 6.96 ∙ 10−6 to 1.01 ∙ 10−5 K−1 in the same temperature range.Conclusions. Comprehensive studies of titanate-zirconate mineral-like matrices show that their mechanical and thermal properties in certain cases significantly exceed the minimum requirements of regulatory documentation for the final forms of HLW.

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Zirconolite Matrices for the Immobilization of REE–Actinide Wastes

et al. 2023

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The structural and chemical properties of zirconolite (ideally CaZrTi2O7) as a host phase for separated REE–actinide-rich wastes are considered. Detailed analysis of both natural and synthetic zirconolite-structured phases confirms that a selection of zirconolite polytype structures may be obtained, determined by the provenance, crystal chemistry, and/or synthesis route. The production of zirconolite ceramic and glass–ceramic composites at an industrial scale appears most feasible by cold pressing and sintering (CPS), pressure-assisted sintering techniques such as hot isostatic pressing (HIP), or a melt crystallization route. Moreover, we discuss the synthesis of zirconolite glass ceramics by the crystallization of B–Si–Ca–Zr–Ti glasses containing actinides in conditions of increased temperatures relevant to deep borehole disposal (DBD).

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Borehole RW Disposal Concept and Prospects of its Implementation in Russia

Abstract: The paper evaluates the prospects of borehole disposal considering a number of solidified RW types generated at Russian enterprises, which was done based on analyzed world literature sources discussing the safety of radioactive waste storage facilities of mine and borehole types.

Cited by 4 publications

References 8 publications

Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

A study of the mechanical and thermophysical properties of crystal matrices for the immobilization of high-level wastes

Zirconolite Matrices for the Immobilization of REE–Actinide Wastes

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