Radiant energy – Invisible radiant energy responsive electric signalling – Including a radiant energy responsive gas discharge device
Reexamination Certificate
2002-08-20
2004-11-23
Gagliardi, Albert (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Including a radiant energy responsive gas discharge device
C250S489000, C250S505100, C250S375000
Reexamination Certificate
active
06822238
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
This invention concerns improvements in and relating to monitoring, particularly, but not exclusively for alpha emitter contamination on surfaces and/or long items.
2. The Relevant Technology
Instruments for detecting alpha emission are known but they are restricted in their applicability. Techniques in which the detector must be brought into very close proximity with the entire surface of the item to be monitored, i.e., closer than 5 cm, are problematical in implementing and time consuming to operate.
Other detectors, based around the detection of ions generated by alpha particle emission, are restricted to applications in which the item to be monitored is small enough to be completely enclosed for the purposes of monitoring.
BRIEF SUMMARY OF THE INVENTION
The present invention aims to provide a system for monitoring surfaces and/or large and particularly long items effectively whilst obtaining a true and accurate reading.
According to a first aspect of the invention we provide an instrument for monitoring alpha emitting sources on an item or location, the instrument comprising a detecting chamber defining a detecting volume, the detecting chamber being provided with an opening/inlet to which portions of the item or location can be presented, and with one or more electrodes for discharging ions produced in the detecting volume, the instrument further being provided to monitor ions discharged on the electrode(s), the opening/inlet to the detecting chamber being open to the presentation or passage of different portions of the item or location whilst sealing means are provided to reduce, and preferably at least substantially eliminate, the passage of ions from outside the detecting volume to within the detecting chamber.
In this way the presentation of an item or location to the instrument is possible, whilst avoiding false readings from ambient ions.
The detection chamber may be provided with an opening in one side. The opening may form a part or the whole of that side. The detection chamber may be in the form of a hood. The item/location may pass across the front of the opening. A gap between the edges of the chamber and the item/location may be provided.
The detecting chamber may be provided with an inlet and an outlet, the inlet to the detecting chamber being open to the passage of an item/location to be monitored from outside the chamber to inside the chamber, the inlet being closed to the passage of ions from outside the chamber to inside the chamber, the outlet from the detecting chamber being open to the passage of an item/location to be monitored from inside the chamber to outside the chamber, the outlet being closed to the passage of ions from outside the chamber to inside the chamber.
An instrument with an enclosing detecting chamber may thus be provided.
The chamber is preferably provided with an inlet and outlet on a common axis. The chamber may be cylindrical. The inlet and/or outlet may be provided in the end wall(s) of the cylinder.
The inlet and/or outlet may be provided within a further chamber. Preferably the inlet and outlet are each provided in a further chamber. The further chamber(s) may be provided with an opening to the surrounding environment. Preferably the further chamber aperture is axially aligned with the aperture (inlet/outlet) into the chamber. Most preferably the aperture of the inlet further chamber, the inlet to the chamber, the outlet from the chamber, and the aperture in the outlet further chamber are all axially aligned.
The inlet and/or outlet further chamber may be cylindrical.
The opening and/or inlet and/or outlet may be closed to the passage of ions into the chamber by an electric field. The sealing means may comprise means for generating an electric field.
The opening and/or inlet and/or outlet may be provided with one or more electrodes.
Where an opening is provided preferably the sealing means are provided in proximity to the gap. The sealing means may be provided around the external periphery of the gap. Continuous or a number of discrete sealing means may be provided.
Preferably the sealing means comprises one or more electrodes, most preferably planar electrode(s). The electrode(s) may be parallel to the item/location and/or to the detecting electrode.
Where an inlet and/or an outlet are provided preferably the electrode(s) are provided in further chamber(s).
An electrode extending along the axis of the inlet and/or outlet may be provided. The electrode may surround or substantially surround the axis of the inlet and/or outlet. A cylindrical electrode may be provided.
A plurality of electrodes may be provided extending along the axis of the inlet and/or outlet. The electrodes are preferably provided in opposition to at least one, and preferably all sides of the item/location. The electrodes may be provided in opposition to one another on opposing sides of the axis of the inlet and/or outlet. Two or more planar electrodes may be provided. A potential difference between the opposing electrodes may be used. Preferably the electrodes are at a different potential to the item/location. Most preferably the electrodes are at the same potential.
A potential difference between the electrode(s) and the item/location is preferably employed. Preferably the item/location is grounded or at least at a reduced potential compared with the electrode(s). Preferably an electric field of at least 50 Vcm
−1
separation between the electrode(s) and item/location is provided. A level of at least 75 Vcm
−1
and more preferably of at least 100 Vcm
−1
may be provided.
The potential may be an AC potential, but a DC potential is preferred.
The electrode(s) may be provided in proximity to the position occupied by the item/location in use. A separation of less than 20 cm may be provided, but preferably the separation is less than 10 cm or even less than 3 cm.
The opening and/or inlet and/or outlet to the chamber may be sealed to the passage of ions by a magnetic field.
Where an opening is provided preferably the magnetic field is generated around the gap and/or the periphery of the opening.
Where an inlet and/or outlet is provided preferably the magnetic field is generated within further chamber(s).
Preferably the magnetic field is configured to repel ions approaching entrance to the detecting volume and/or the inlet and/or outlet. Electromagnets and/or permanent magnets may be provided.
The detection chamber may be provided with one or more, preferably pairs of, opposing detection electrodes. Preferably the electrodes of a pair are provided such that the item passes between them. A potential difference between the opposing electrodes of a pair is preferably generated in use. An applied or electrostatic potential may be employed.
The detection chamber may be provided with one or more electrodes opposing the item/location. An applied potential or electrostatic potential may be employed.
The means for monitoring ions discharged on the electrode(s) may comprise electrostatic charge monitoring means. More preferably the means for monitoring ions discharged on the electrode(s) comprise current indicating means and more preferably current measuring means, such as an electrometer.
Preferably one or more of the electrodes is connected to an electrometer.
The item/location may be a surface, such as an area of floor, wall, ceiling, soil, rubble, part of the surface of a piece of equipment, such as a glove box, material traveling on a conveyor, or a discrete item such as a pipe, beam (such as an I beam), pole, fuel cladding, fuel element, cable, wire, rail or other elongate or large item.
The instrument may be provided with associate means for supporting the item/location and/or moving the item/location through the instrument. Such means may be provided on both sides of the instrument.
The instrument may be provided with means for supporting it on the item/location to be monitored. The support means may enable the instrument to be moved along the item and/or over the location.
According to a sec
Dockray Thomas
Luff Craig Janson
Macarthur Duncan Whittemore
Orr Christopher Henry
British Nuclear Fuels PLC
Gagliardi Albert
Workman & Nydegger & Seeley
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