Abstract: A neutron monitoring instrument, principally of the survey type, is provided with an inner neutron detector(s) enclosed in a layer of neutron attenuating material and one or more outer neutron detectors provided on the attenuating layer and enclosed in a layer of neutron moderating material. The inner detector(s) monitor neutrons in the 100 KeV to 15 MeV energy range, with the outer detectors monitoring neutrons in the thermal to 100 KeV range. Sensitivity across the spectrum and evenness of response are improved compared with the prior art to give better close equivalence determinations.

Abstract: The apparatus and method provide techniques through which both alpha and beta emission determinations can be made simultaneously using a simple detector structure. The technique uses a beta detector covered in an electrically conducting material, the electrically conducting material discharging ions generated by alpha emissions, and as a consequence providing a measure of those alpha emissions. The technique also offers improved mountings for alpha detectors and other forms of detectors against vibration and the consequential effects vibration has on measurement accuracy.

Abstract: The apparatus and method provide techniques for effectively implementing alpha and/or beta and/or gamma monitoring of items or locations as desired. Indirect alpha monitoring by detecting ions generated by alpha emissions, in conjunction with beta and/or gamma monitoring is provided. The invention additionally provides for screening of items prior to alpha monitoring using beta and/or gamma monitoring, so as to ensure that the alpha monitoring apparatus is not contaminated by proceeding direct to alpha monitoring of a heavily contaminated item or location. The invention provides additional versatility in the emission forms which can be monitored, whilst maintaining accuracy and avoiding inadvertent contamination.

Abstract: The apparatus and method provide a technique for significantly reducing capacitance effects in detector electrodes arising due to movement of the instrument relative to the item/location being monitored in ion detection based techniques. The capacitance variations are rendered less significant by placing an electrically conducting element between the detector electrodes and the monitored location/item. Improved sensitivity and reduced noise signals arise as a result. The technique also provides apparatus and method suitable for monitoring elongate items which are unsuited to complete enclosure in one go within a chamber. The items are monitored part by part as the pass through the instrument, so increasing the range of items or locations which can be successfully monitored.

Abstract: The apparatus and method provide a technique for more simply measuring alpha and/or beta emissions arising from items or locations. The technique uses indirect monitoring of the emissions by detecting ions generated by the emissions, the ions being attracted electrostatically to electrodes for discharge of collection. The apparatus and method employ a chamber which is sealed around the item or location during monitoring with no air being drawn into or expelled from the chamber during the monitoring process. A simplified structure and operations arises as a result, but without impairing the efficiency and accuracy of the detection technique.

Abstract: The apparatus and method provide an improved technique for detecting ions as the area from which ions are attracted to a detector is increased, consequently increasing the number of ions detected. This is achieved by providing the outer electrodes of the detector connected to the electrical potential, together with alternate intermediate electrodes. The other intermediate electrodes and preferably the housing are grounded. The technique renders such detection techniques more sensitive and gives them a lower threshold at which they can function.

Abstract: The apparatus and method provide a technique for improving detection of alpha and/or beta emitting sources on items or in locations using indirect means. The emission forms generate ions in a medium surrounding the item or location and the medium is then moved to a detecting location where the ions are discharged to give a measure of the emission levels. To increase the level of ions generated and render the system particularly applicable for narrow pipes and other forms of conduits, the medium pressure is increased above atmospheric pressure.

Abstract: An apparatus for succesively loading solid objects (19) into a tube (27), for instance, nuclear fuel pellets into a nuclear fuel tube, includes means (17) for feeding the objects towards one, open end (29) of the tube. A reduced pressure is induced between each solid object and the tube end prior to entry of the object into the tube.

Abstract: Processing apparatus and methods are provided which involve the selective ionization of a feed material; the separation of ionized and non-ionized species; a selective excitation of the still ionized species; introduction of a chemical material to cause selective transition to a non-ionized state of part of the feed; and a further separation of ionized and non-ionized species. Other improvements in selective excitation based processing are also disclosed. Separation of isotopes and/or elements from one another and changing chemical and physical form is provided in a single process from a variety of feeds.

Abstract: The invention provides apparatus and methods which facilitate movement of an instrument relative to an item or location being monitored and/or the item or location relative to the instrument, whilst successfully excluding extraneous ions from the detection location. Thus, ions generated by emissions from the item or location can successfully be monitored during movement. The technique employs sealing to exclude such ions, for instance, through an electro-field which attracts and discharges the ions prior to their entering the detecting location and/or using a magnetic field configured to repel the ions away from the detecting location.

Abstract: Apparatus for carrying out a process between first and second immiscible fluids comprises channels defining first and second primary flow paths for permitting fluid flow of the respective first and second fluids therethrough. Portions of the flow paths are disposed close to or adjacent one another and communicate with one another at a region where the flow paths are constructed and arranged so as to permit the fluids to form a stable interface between them. At least one of the fluids is induced to flow in a secondary direction perpendicular to the direction of its primary flow path at the region either by bending the primary flow path around a curve, or by positioning flow detectors within the flow path.

Abstract: Nuclear fuel assembly configurations are provided for mixed oxide fuels. Neutron poisons are provided within the MOX of certain fuel rods in the fuel assembly, those fuel rods being preferentially grouped towards the periphery of the fuel assembly. In this way, optimized reduction of reactivity is provided during the initial part of the fuel cycle but the neutron poison is burnt out so as not to interfere with the reactivity during subsequent parts of the cycle.

Abstract: This disclosure sets forth a method for processing metal waste incorporating substantial zirconium as exemplified by nuclear fuel rods which include enriched uranium and other nuclear products. This process contemplates conversion of the zirconium and other constituents into oxides by mixing with an acid, subsequently forming a solution or a gel which is either dried or frozen, thereby yielding a green shaped body. The green body is thereafter sintered to form a dimensionally and structurally stable monolith for disposal.

Abstract: Apparatus for carrying out a process between first and second immiscible fluids, comprises first and second channels defining flow paths, for permitting fluid flow of respective first and second immiscible fluids therethrough. Portions of the flow paths are disposed close to, or adjacent to, one another and communicate with one another to define a region in which, in use, a stable interface between the fluids is formed. One, or more, dimensions of the region are varied along the length of the interface in a direction of fluid flow to compensate for variation in the properties of the fluids during the carrying out of the process and thereby maintain stability of the interface.

Abstract: A fuel assembly for a nuclear reactor is described, the fuel assembly including: a plurality of fuel pins (12) extending substantially parallel to the axis of the assembly and to each other; at least two structural grids spaced apart from each other, the grids being in contact with said fuel pins (12) and maintaining said fuel pins substantially mutually parallel and preventing contact therebetween, wherein the fuel assembly further comprises at least one mixing grid (50) situated intermediate said at least two structural grids, the fuel assembly being characterized in that said mixing grid (50) is positioned and fixedly located out of substantial contact with said fuel pins (12), the mixing grid also having turbulence inducing means (61) to promote turbulence in a coolant (62) flowing through said fuel assembly in use and in that the mixing grid is formed from sheet metal wherein the plane of the metal sheet from which the mixing grid is formed lies in a plane which is transverse to the axis of the fuel pin

Abstract: Improved processing apparatus and methods are provided which involve the selective ionisation of a feed material and the separation of ionised and non-ionised species. Introduction of a chemical material to cause selective transition to a non-ionised and/or solid or liquid state of part of the feed is provided. The process offers high through puts by virtue of the ionised and non-ionised species being in equilibrium with one another.

Abstract: A gas generator comprising a layer of first material are provided with a layer of second material on one surface and a layer of third material on the other opposing surface is provided. The application of an external potential results in the flow of gas from one side of the generator to another due to the properties of the materials presented. The use of an electrolyte material as the first material and mixed conductors as the second and/or third materials is particularly beneficial in obtaining high flow rates. The use of the generator to produce oxygen for injection into a methane stream is particularly preferred.

Abstract: Radioactively contaminated material is cleaned by contacting the material with a decontaminating liquid comprising an aqueous solution of nitric acid containing an NOx generating agent. The NOx generating agent may be a nitrite, for example, sodium nitrite, or a ferrous metal. The material to be cleaned may comprise a plastics material contaminated with uranium or other actinides. Cleaning is effected by placing the material in a rotatable, apertured vessel in which the material is subjected to a leaching cycle by contact with the decontaminating liquid and then a washing cycle in which the material is contacted with a washing liquid.

Abstract: A lighting assembly (10) which extends through the thickness of a wall (14) having a first side (16) and a second side (20) is described. The lighting assembly (10) comprises at least one light source (46) to illuminate an area on the first side (16) of said wall (14) and means being included to enable replacement of said light source from the second side (20) of said wall (14) wherein said means includes at least one duct (30) extending at least part of the way from the first side (16) of the wall (14) to the second side (20) of the wall (14); light source carrier means (50) on which said light source is mounted, said light source carrier means (50) and said light source (46) being movable through said at least one duct (30) from said second side (20) to said first side (16); moving means (80) to move said light source (46) and said carrier means (50) through said at least one duct (30); and, power supply means to said light source (46).

Abstract: A process for the decontamination of radioactively contaminated metal which comprises contacting the metal with a decontamination reagent solution containing an organic acid and an oxidising agent, allowing said solution to react with the contaminated metal at a pH of up to 4.5, treating the resulting solution to cause substantially complete precipitation of dissolved metal together with radionuclides and separating precipitated material, containing radioactive contaminants, from said solution.