The Australian National University

Other

Australian Atomic Energy Commission

Australian Nuclear Science and Technology Organization

Australia Nuclear Science & Technology Organisation

Australian Nat'l Univ. of Acton

Eric J Ramm

Alfred E Ringwood

Wilhelmus J Bukyx

John G Padgett

Wilhelmus J Buykx

Albert E Ringwood

Processing of a dry precursor material

Waste material such as toxic compounds, radioactive waste materials and spent nuclear fuel rods are encapsulated in a container system which is subjected to a hot pressure process to cause a protective powder material located around the waste material to form a dense matrix and function as a highly corrosion resistant and protective shroud. Embodiments include hot isostatic pressing and hot uniaxial pressing, the use of metal powder such as copper powder for the protective powder material or alternatively ceramic powder and, depending upon the embodiment chosen, the use of a single container or dual container system in which a first container is located within an outer container. Either or both of such containers may be cylindrical with a bellows-like side wall to facilitate compression thereof in an axial direction.

Encapsulation of waste materials

A compressible bellows type metal canister is used in a hot pressing process for immobilizing high level radioactive nuclear waste material in the form of synthetic rock, the canister comprises a base wall and a corrugated bellows side wall of generally circular cross-section, concentrically arranged within the corrugated side wall is a cylindrical liner. In the center of the base wall a conically-tapered aperture is provided with a filter plug. Diametrically opposed apertures are provided in the base wall and are connected by an outlet pipe for removal of waste gases.

Hot pressing of bellows like canisters

A metal compressible bellows-type container or canister is used in a hot uniaxial pressing process with a mixture of high level radioactive nuclear waste material and a synthetic rock forming material filling the canister. The canister has a bottom wall, a convoluted bellows-like side wall, a lid or top wall and transverse metal apertured plates dividing the canister into three equally sized zones. Preferably the apertures are of a clover leaf configuration and are located at the center of the plates. Cylindrical liners can be provided to maintain a zone between each liner and the bellows-like side wall to prevent ingress of the particulate mixture of waste and synthetic rock forming material.

Heat transfer and stabilizing apparatus

A vibratory processing arrangement including an apparatus comprising three main stages. Namely, a high level waste vibrating impregnator, a vibrating calciner and a vibratory powder mixer. The waste impregnator comprises a downwardly inclined trough having flexible mountings and a vibrator at its upstream end, a hood structure and a series of liquid sprays connected to a high level waste supply tube. The vibratory calciner comprises a downwardly inclined tube connected to a downstream discharge tube. The discharge tube has an inlet pipe for entry of reducing gas. The reducing gas passes upwardly through the tubes to a gas discharge take-off tube near the upstream end of the downwardly inclined tube. A vibrator is tuned to provide the desired flow rate through the downwardly inclined tube. Calcined discharged powder falls downwardly into the vibratory mixer, which has a vibratory actuator and flexible mountings. Titanium powder is introduced into the vibratory mixer through a secondary inlet and is intimately mixed with the calcined discharged powder before being discharged into respective canisters.

Method of producing impregnated synthetic rock precursor

An apparatus for hot uniaxial pressing of heat resistant metal canisters containing synthetic rock components. A hydraulic press is provided in a furnace and has a fixed top press frame with refractory top pad and fixed base. The furnace comprises an electrical induction coil with a cylindrical metal sleeve functioning as a susceptor sleeve. The press is also provided with an upwardly acting hydraulic ram with ram head and refractory top pad. A platen is provided on a ram having a mounting shaft. The ram is actuable to laterally displace the platen so that columns extending on opposed sides of the press and having respective recesses are arranged to engage with complementary portions of the platen. The susceptor sleeve can be removed by swinging the platen around to extend below the region of the susceptor, but not into engagement with the column recesses, raising the platen and then releasing a clamping mechanism which normally grips the susceptor.

Apparatus for forming ceramics

A dry, pourable particulate mixture of nuclear waste and synthetic rock-forming components is produced by supplying the rock forming components in dry particulate form to a mixer, supplying the nuclear waste in liquid phase and operating the mixer to distribute the waste substantially uniformly through the synthetic rock components; the mixture is calcined to produce a precursor powder which is adapted to be used in a hot pressing process to form synthetic rock throughout which the radioactive nuclear waste is distributed and immobilized. A reducing gas atmosphere is preferably maintained in the calcining process stage, the gas being for example pure hydrogen or a mixture of hydrogen in nitrogen in proportions which are non-explosive. A screw type or paddle type conveyor can be used for the mixing and calcining stages although the calcining can be effected in a vertically downwardly directed tube device having associated heating means such as microwave heating.

Preparation of particulate radioactive waste mixtures

Particulate material is poured into a container which is decay and heat resistant, the container is sealed and subjected to axial compression at elevated temperature to cause densification of the material, there being an arrangement for preventing substantial radially outward deformation of the container during compression. An important application is to immobilization of nuclear reactor waste in a synthetic rock structure formed during the high temperature compression step, and advantageously the containers are secured within an outer metal cannister for subsequent safe handling and disposal. An important embodiment includes a bellows container which advantageously is upwardly pressed into an inverted metal cannister restrained by an upper abutment, the bellows container becoming an interference fit within the metal cannister during the final portion of compression, but the bellows container wall itself being substantially sufficient to prevent gross outward deformation of the bellows container.

Growing community of inventors

Lilli Pilli, Australia

Eric J Ramm