The Australian National University

Other

Australian Atomic Energy Commission

Australia Nuclear Science & Technology Organisation

Australian Nat'l Univ. of Acton

Alfred E Ringwood

Eric J Ramm

John M Bird

John G Padgett

Wilhelmus J Bukyx

Wilhelmus J Buykx

An abrasive compact comprising 40 to 90 volume percent of cubic boron nitride (CBN) crystals bonded by 60 to 10 volume percent of a bonding matrix comprised mainly of an intimate mixture of silicon nitride and metallic diboride MB.sub.2 where M represents metal atoms chosen from the group of titanium, zirconium and hafnium atoms. The compact may be produced by a method which comprises intimately mixing particulate CBN crystals with a bonding agent in the proportion 95 to 60 volume percent of CBN and 5 to 40 volume percent of bonding agent, the bonding agent containing the metal atoms in the atomic proportions Si.sub.30 M.sub.70 to Si.sub.85 M.sub.15, subjecting the mixture of CBN crystals and bonding agent to temperatures in the range 900.degree. to 1800.degree. C. and pressures in the range 5 to 70 Kilobars, and maintaining the temperature and pressure conditions for a period of at least about 30 seconds, sufficient to cause most of bonding agent to form the bonding matrix.

Abrasive compact of cubic boron nitride and method of making same

Diamond compact possessing low electrical resistivity

Production of diamond compacts consisting essentially of diamond

Diamond compact composed of 60-95 volume % diamond crystals plastically deformed into a closely packed, rigid structure with contacts between the diamond crystals over extended mating surfaces arising from the plastic deformation. The diamond crystals are bonded together by an interstitial bonding material composed of a refractory carbide, such as silicon carbide, or a bonding material composed of a metal such as rhenium and a refractory carbide formed by reaction of a metallic bonding agent, such as tungsten, with carbon.

Diamond compacts

A diamond compact comprised of 60-95 volume percent of diamond crystals which have been plastically deformed so that they form a rigid framework structure in which contacts between the diamond crystals occur over surfaces arising from plastic deformation of the diamond crystals during formation of the compact under pressure and temperature conditions within the graphite stability field. The diamond framework structure is bonded together by interstitial refractory carbide phases or metallic phases comprised of metals not forming carbides in the presence of carbon. The phases have a melting point greater than 1600.degree. C. The compact comprises less than about 2 percent volume of graphite and possesses a compressive strength greater than 10 kbars.

Diamond compacts and process for making same

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 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.

Containment and densification of particulate material

Disclosed are two improved container alloys for radioactive nuclear waste. Radioactive nuclear waste can be contained over extended periods of time by encapsulating the waste materials in containers composed of these alloys and burying the containers underground in an impervious, stable rock formation.

Container for radioactive nuclear waste materials

Disclosed are two improved container materials for radioactive nuclear waste. Radioactive nuclear waste can be contained over extended periods of time by encapsulating the waste materials in containers composed of these alloys and burying the containers underground in an impervious, stable rock formation.

A process for immobilizing high level waste (HLW) sludge containing aluminium and/or iron compounds which comprises the steps of:

Process for the treatment of high level nuclear wastes

A process for immobilizing high level radioactive waste (HLW) calcine comprises the steps of:

Growing community of inventors

Redhill, Australia

Alfred E Ringwood