Patent Number: 043158315
Section: description

A number of examples illustrating the process of the invention are given hereinafter in a non-limitative manner. EXAMPLE 1 About 60 liters of solid radioactive waste are to be dry-encased. The following are introduced into a cylindrical mould: 130 kg of a glycol-maleophthalate-based polyester resin dissolved in styrene, marketed under the trade name "NS 574" by the CDF Chimie Company; PA1 150 kg of silica sand of grain size ranging between 0.1 and 1.2 mm; PA1 70 kg of borax (Na.sub.2 B.sub.4 O.sub.7, 10 H.sub.2 O); PA1 2.5 kg of silica gel; PA1 1.95 kg or 1.5% by weight based on the resin of methyl-ethyl-ketone peroxide. PA1 130 kg of polyester resin "NS 574"; PA1 150 kg of silica sand, grain size 0.1 to 1.2 mm; PA1 23 kg of polystyrene in the form of balls; PA1 700 g of silica gel; PA1 1.95 kg of methyl-ethyl-ketone peroxide; PA1 350 g of a retarding agent marketed under the trade name "NLC 10" by the Akzo France Company. PA1 10 kg of polyester resin "NS 574"; PA1 6 kg of polyethylene in the form of balls; PA1 14 kg of silica sand, grain size 0.1 to 1.25 mm; PA1 150 g of methyl-ethyl-ketone. PA1 40 kg of epoxy resin "LOPOX 200" (marketed by the CDF Chimie Company); PA1 11 kg of hardening agent "D 544" (marketed by the CDF Chimie Company); PA1 1.2 kg of accelerator "A 101"; PA1 75 kg of silica sand of grain size 0.1 to 1 mm; PA1 1 kg of silica gel. The complete mixture is mixed homogeneously for 20 minutes, followed by the addition of 120 g or 0.8% by weight based on the resin of cobalt naphthenate. The basket containing 60 liters of solid radioactive waste is then introduced and cross-linking takes place. A homogeneous block is obtained without cracks whose diameter is 60 cm, height 77 cm and volume 220 liters. Polymerisation shrinkage is small and no cracks are encountered. EXAMPLE 2 60 Liters of solid radioactive waste contained in a basket are encased under water, said basket being placed at the bottom of a conditioning pond. The following are introduced into a mould: The whole mixture is mixed for 30 minutes, followed by the addition of 130 g of cobalt naphthenate. Mixing is then continued for a further 15 minutes. The mould containing this mixture is then introduced into the pond vessel at a depth of about three meters. The basket containing the solid waste is then introduced into the mould. 50 minutes after the introduction of the accelerator (cobalt naphthenate) the start of solid setting is observed. The maximum temperature reached in the centre of the block is 95.degree. C. after about five hours, and this is followed by slow cooling. After 22 hours the temperature is 50.degree. C. Gas is given off at the time of the temperature maximum. In this way a solid cylindrical block is obtained of volume 230 liters containing 60 liters of radioactive waste. The weight of this block is 450 kg and the weight of the waste 120 kg. It is found that cross-linking has taken place correctly under a depth of three meters of water without any release of solid material. There is merely an evolution of gas at the time of solid setting. The block has a homogeneous appearance without cracks. It is pointed out that the solid polystyrene used as the plasticizer has a resistance to ionising radiation which is close to that of the polyester resin used. EXAMPLE 3 15 kg of solid radioactive waste placed in a basket at the bottom of a pond are encased under water. The following are introduced into a mould of volume 30 liters: The complete mixture is mixed for 15 minutes, followed by the addition of 15 g of cobalt naphthenate, followed by further mixing for 10 minutes. The mould containing this mixture is then placed in the pond vessel. The basket containing the solid radioactive waste is then introduced into the mould. Polymerisation starts 15 minutes after incorporating the accelerator. A homogeneous compact block is obtained. EXAMPLE 4 100 kg of solid radioactive waste placed in a basket are encased. The following are introduced into a container with a volume of 100 liters: The complete mixture is mixed for 15 minutes and then the basket containing the solid radioactive waste is introduced into the container. After a few hours a compact block is obtained. The block obtained has the same characteristics as that of Example 3.