Nuclear Waste Immobilization in Cement-Based Materials: Overview of French Studies
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NUCLEAR WASTE IMMOBILIZATION IN CEMENT-BASED MATERIALS: OVERVIEW OF FRENCH STUDIES
ROSEMARIE ATABEK, PASCAL BOUNIOL, ELIANE REVERTEGAT, JEAN OLIVER, PHILIPPE GEGOUT AND MICHEL JORDA Commissariat A l'Energie Atomique, CEN-FAR, DRDD/SESD, B.P N°6 92265 FONTENAY AUX ROSES CEDEX, FRANCE
ABSTRACT An overview of the different problems to be solved for waste form disposal in a shallow-land burial site is presented. Examples of cementbased materials used to immobilize concentrates are given in relation to cement chemistry. Experimental studies, undertaken to assess concrete durability, obviously indicate that pH is the starting parameter of chemical degradation reactions. It is found that blended cement (CLC) has a better cesium retention ability and a stronger resistance to chloride and sulfate attack than Portland cement. INTRODUCTION Hydraulic binders are currently used in France for civil engineering work and barrier construction in nuclear waste disposal as well as embedding materials for waste immobilization. The essential part of the waste production comes from Nuclear Power and Reprocessing plants, Nuclear Centres and fuel element factories, involving a large variety of problems which must be solved taking into account the working constraints of the waste producers: grouting of hulls and caps, embedment of solid wastes, solidification of sludges, highly-salt-ladened concentrates and ashes. Waste management policy in France provides shallow-land disposal for radioactive wastes with an alpha emitter activity not exceeding 3.7 MBq/kg (0.1 Ci/t). The production of Low and Medium level wastes is estimated at 500,000 cu.m for 30 years. The producers have to supply, to the French national waste management agency (ANDRA), precise informations on the waste package characteristics, to prove that the package abide acceptance criteria originating in Fundamental Safety Rule and to evaluate its long term behaviour. STORAGE CONDITIONS OF DISPOSAL CENTRE
LOW- AND
MEDIUM-LEVEL WASTES
AT THE
MANCHE WASTE
To be acceptable in installations for long-term disposal at a shallowland burial site, radioactive waste packages must comply with the activity limits defined according to the general principles set forth in Fundamental Safety Rule No.1-2 [1] and specified in the Technical Safety Requirements of the host Disposal Centre. The requirements stipulate the maximum specific activity limits of the packages and also set the activity thresholds above which the wastes must be embedded. They are applied by ANDRA for its different shallow-land disposal centres, currently for the Manche Disposal Centre and the future Aube Centre. For waste requiring embedment, the conditions to be met prior to authorization are set forth in Fundamental Safety Rule No.3-2e [2]. Two types of package can be distinguished: - homogeneous waste, which is embedded in a matrix, is in the form of a uniform dispersion of radioactive products in a container. The long-term containment of the radioactivity is mainly provided by the water leach resistance of the immobi
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