Long-term experimental evidences of saturation of compacted bentonite under repository conditions

M. V. Villar, P. L. Martín, I. Bárcena, J. L. García-Siñeriz, R. Gómez-Espina, A. Lloret

Resultado de la investigación: Article

21 Citas (Scopus)

Resumen

This paper summarises the information gathered in the last 15. years on the saturation of compacted bentonite obtained from different laboratory-scale tests, a large-scale mock-up test, and a real-scale in situ test, that were performed to simulate the conditions of the bentonite barrier in a high-level radioactive waste repository and to better understand the hydration/heating processes. In all the tests the bentonite used was the Spanish FEBEX bentonite, the maximum temperature in the system was 100. °C and the water used was of the granitic type, with low salinity. Some of the tests were running for more than thirteen years.The migration of water vapour in areas affected by the high temperature induced by the radioactive waste decay is very rapid, its extent depending on the actual temperature and bentonite porosity. The water vapour condensates in cooler areas and this causes water content increases in internal zones of the barrier where the liquid water coming from the host rock has not yet arrived. The hydration kinetics is initially quicker when the temperature is high, provided no vapour phase is formed. Nevertheless, the major effect of the thermal gradient on saturation is a delaying of it in the inner parts of the barrier, which can be very persistent and depends on the actual thermal gradient and consequently, on the barrier thickness and boundary conditions.During the transient period in which the barrier is saturating, important changes in the water content and dry density of the bentonite are generated, which induce bentonite density and water content gradients along its thickness. These gradients could eventually disappear once the barrier is fully saturated, depending on the irreversibility of the deformations.The average density of the water in the saturated barrier will be higher than 1g/cm 3, due to the predominance of high-density, interlayer water in the compacted bentonite, and consequently, more water than expected, according to calculations made considering the density of free water, would fit in the bentonite pores.The rate of hydration of the barrier depends on the bentonite and surrounding media hydraulic properties (that is, water availability), waste temperature and buffer thickness and geometry.

Idioma originalEnglish
Páginas (desde-hasta)57-69
Número de páginas13
PublicaciónEngineering Geology
Volumen149-150
DOI
EstadoPublished - 2 nov 2012

Huella dactilar

Bentonite
bentonite
repository
saturation
Water
hydration
Hydration
Water content
water content
Radioactive wastes
Thermal gradients
radioactive waste
Water vapor
water vapor
water
Temperature
Industrial heating
in situ test
dry density
temperature

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Geology

Citar esto

Villar, M. V. ; Martín, P. L. ; Bárcena, I. ; García-Siñeriz, J. L. ; Gómez-Espina, R. ; Lloret, A. / Long-term experimental evidences of saturation of compacted bentonite under repository conditions. En: Engineering Geology. 2012 ; Vol. 149-150. pp. 57-69.
@article{712aa66e4a71446488a9755be471fc4f,
title = "Long-term experimental evidences of saturation of compacted bentonite under repository conditions",
abstract = "This paper summarises the information gathered in the last 15. years on the saturation of compacted bentonite obtained from different laboratory-scale tests, a large-scale mock-up test, and a real-scale in situ test, that were performed to simulate the conditions of the bentonite barrier in a high-level radioactive waste repository and to better understand the hydration/heating processes. In all the tests the bentonite used was the Spanish FEBEX bentonite, the maximum temperature in the system was 100. °C and the water used was of the granitic type, with low salinity. Some of the tests were running for more than thirteen years.The migration of water vapour in areas affected by the high temperature induced by the radioactive waste decay is very rapid, its extent depending on the actual temperature and bentonite porosity. The water vapour condensates in cooler areas and this causes water content increases in internal zones of the barrier where the liquid water coming from the host rock has not yet arrived. The hydration kinetics is initially quicker when the temperature is high, provided no vapour phase is formed. Nevertheless, the major effect of the thermal gradient on saturation is a delaying of it in the inner parts of the barrier, which can be very persistent and depends on the actual thermal gradient and consequently, on the barrier thickness and boundary conditions.During the transient period in which the barrier is saturating, important changes in the water content and dry density of the bentonite are generated, which induce bentonite density and water content gradients along its thickness. These gradients could eventually disappear once the barrier is fully saturated, depending on the irreversibility of the deformations.The average density of the water in the saturated barrier will be higher than 1g/cm 3, due to the predominance of high-density, interlayer water in the compacted bentonite, and consequently, more water than expected, according to calculations made considering the density of free water, would fit in the bentonite pores.The rate of hydration of the barrier depends on the bentonite and surrounding media hydraulic properties (that is, water availability), waste temperature and buffer thickness and geometry.",
keywords = "Bentonite, Engineered barrier, Hydration, Radioactive waste repository, Temperature",
author = "Villar, {M. V.} and Mart{\'i}n, {P. L.} and I. B{\'a}rcena and Garc{\'i}a-Si{\~n}eriz, {J. L.} and R. G{\'o}mez-Espina and A. Lloret",
year = "2012",
month = "11",
day = "2",
doi = "10.1016/j.enggeo.2012.08.004",
language = "English",
volume = "149-150",
pages = "57--69",
journal = "Engineering Geology",
issn = "0013-7952",
publisher = "Elsevier",

}

Long-term experimental evidences of saturation of compacted bentonite under repository conditions. / Villar, M. V.; Martín, P. L.; Bárcena, I.; García-Siñeriz, J. L.; Gómez-Espina, R.; Lloret, A.

En: Engineering Geology, Vol. 149-150, 02.11.2012, p. 57-69.

Resultado de la investigación: Article

TY - JOUR

T1 - Long-term experimental evidences of saturation of compacted bentonite under repository conditions

AU - Villar, M. V.

AU - Martín, P. L.

AU - Bárcena, I.

AU - García-Siñeriz, J. L.

AU - Gómez-Espina, R.

AU - Lloret, A.

PY - 2012/11/2

Y1 - 2012/11/2

N2 - This paper summarises the information gathered in the last 15. years on the saturation of compacted bentonite obtained from different laboratory-scale tests, a large-scale mock-up test, and a real-scale in situ test, that were performed to simulate the conditions of the bentonite barrier in a high-level radioactive waste repository and to better understand the hydration/heating processes. In all the tests the bentonite used was the Spanish FEBEX bentonite, the maximum temperature in the system was 100. °C and the water used was of the granitic type, with low salinity. Some of the tests were running for more than thirteen years.The migration of water vapour in areas affected by the high temperature induced by the radioactive waste decay is very rapid, its extent depending on the actual temperature and bentonite porosity. The water vapour condensates in cooler areas and this causes water content increases in internal zones of the barrier where the liquid water coming from the host rock has not yet arrived. The hydration kinetics is initially quicker when the temperature is high, provided no vapour phase is formed. Nevertheless, the major effect of the thermal gradient on saturation is a delaying of it in the inner parts of the barrier, which can be very persistent and depends on the actual thermal gradient and consequently, on the barrier thickness and boundary conditions.During the transient period in which the barrier is saturating, important changes in the water content and dry density of the bentonite are generated, which induce bentonite density and water content gradients along its thickness. These gradients could eventually disappear once the barrier is fully saturated, depending on the irreversibility of the deformations.The average density of the water in the saturated barrier will be higher than 1g/cm 3, due to the predominance of high-density, interlayer water in the compacted bentonite, and consequently, more water than expected, according to calculations made considering the density of free water, would fit in the bentonite pores.The rate of hydration of the barrier depends on the bentonite and surrounding media hydraulic properties (that is, water availability), waste temperature and buffer thickness and geometry.

AB - This paper summarises the information gathered in the last 15. years on the saturation of compacted bentonite obtained from different laboratory-scale tests, a large-scale mock-up test, and a real-scale in situ test, that were performed to simulate the conditions of the bentonite barrier in a high-level radioactive waste repository and to better understand the hydration/heating processes. In all the tests the bentonite used was the Spanish FEBEX bentonite, the maximum temperature in the system was 100. °C and the water used was of the granitic type, with low salinity. Some of the tests were running for more than thirteen years.The migration of water vapour in areas affected by the high temperature induced by the radioactive waste decay is very rapid, its extent depending on the actual temperature and bentonite porosity. The water vapour condensates in cooler areas and this causes water content increases in internal zones of the barrier where the liquid water coming from the host rock has not yet arrived. The hydration kinetics is initially quicker when the temperature is high, provided no vapour phase is formed. Nevertheless, the major effect of the thermal gradient on saturation is a delaying of it in the inner parts of the barrier, which can be very persistent and depends on the actual thermal gradient and consequently, on the barrier thickness and boundary conditions.During the transient period in which the barrier is saturating, important changes in the water content and dry density of the bentonite are generated, which induce bentonite density and water content gradients along its thickness. These gradients could eventually disappear once the barrier is fully saturated, depending on the irreversibility of the deformations.The average density of the water in the saturated barrier will be higher than 1g/cm 3, due to the predominance of high-density, interlayer water in the compacted bentonite, and consequently, more water than expected, according to calculations made considering the density of free water, would fit in the bentonite pores.The rate of hydration of the barrier depends on the bentonite and surrounding media hydraulic properties (that is, water availability), waste temperature and buffer thickness and geometry.

KW - Bentonite

KW - Engineered barrier

KW - Hydration

KW - Radioactive waste repository

KW - Temperature

UR - http://www.scopus.com/inward/record.url?scp=84866548879&partnerID=8YFLogxK

U2 - 10.1016/j.enggeo.2012.08.004

DO - 10.1016/j.enggeo.2012.08.004

M3 - Article

AN - SCOPUS:84866548879

VL - 149-150

SP - 57

EP - 69

JO - Engineering Geology

JF - Engineering Geology

SN - 0013-7952

ER -