Self-disposal option for highly-radioactive waste reconsidered
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Self-disposal option for highly-radioactive waste reconsidered M. Ojovan1, V. Kascheev 2 and P. Poluektov 2 Department of Materials, Imperial College London, United Kingdom 2 Institute for Inorganic Materials OJSC (A.A. Bochvar VNIINM), 5 Rogova Street, Moscow, Russia 1
ABSTRACT Self-disposal option for heat-generating radioactive waste (HLW, spent fuel, sealed radioactive sources) known also as rock melting concept was considered in the 70s as a viable but alternative disposal option by both DOE in the USA and Atomic Industry Ministry in the USSR. Self-disposal is currently reconsidered with a novel purpose – to penetrate into the very deep Earth’s layers beneath the Moho’s discontinuity and to explore Earth interior. Selfdescending heat generating capsules can be used for disposal of dangerous radioactive wastes in extremely deep layers of the Earth preventing any release of radionuclides into the biosphere. Descending of capsules continues until enough heat is generated by radionuclides to provide partial melting of surrounding rock. Estimates show that extreme depths of several tens and up to hundred km can be reached by capsules which could never be achieved by other techniques. INTRODUCTION Self-disposal or rock melting concept [1-4] utilizes the heat generated by decaying radionuclides of radioactive waste inside a heavy and durable capsule to melt the rock on its way down. The heat from radionuclides within the capsule partially melts the enclosing rock. If the average density of the capsule (mass divided by volume) is higher than that of molten rock, the melt will be displaced upwards past the heavier capsule [5-8]. Eventually the melt cools and solidifies i.e.. it vitrifies to form a glassy material or partly recrystallizes to form crystalline phases, therefore sealing the route along which the capsule has passed through. Descending or self-disposal continues while enough heat is generated by radionuclides to provide melting of the surrounding rock. Estimates show that extreme depths of several tens to one-hundred km can be reached by capsules, which could never be achieved by other techniques. Thus self-descending heat generating capsules could be used for self-disposal of dangerous radioactive wastes in extremely deep layers of the Earth preventing any release of radionuclides into the biosphere. This idea which was considered in the 70s as a viable alternative disposal option by DOE is reconsidered now [9]. In addition to that, self-descending capsules were recently proposed as a unique tool to explore the deep Earth interior including its mantle e.g. depths which are not accessible by current drilling techniques [10-13]. Acoustic monitoring of the capsules was suggested as a mean to reveal data about the structure of the Earth’s interior. THEORY Self-descending was studied primarily in connection with self-disposal of radioactive wastes in USA, EU and in Russia [1–8]. The radiogenic heat from radioactive waste can be used for deep self-disposal of heat-generating high level radioactive waste (HLW) as
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