- Email: [email protected]
Neutron radiography sytem
=New equtpment Neutron radiography system An addition to the current range of available NDT techniques is being offered by Neu-Sight. Produced in a collaborative venture between Oxford Instruments and Rolls- Royce & Associates, the system is a neutron radiography development, consisting of a 12 MeV Oxford Instruments 'Oscar' superconducting cyclotron and advanced image acquisition and manipulation equipment from Rolls-Royce. The benefits of this technique derive from the physical properties of neutrons, which are strongly attenuated by hydrogenous materials, but penetrate with relative ease the heavier elements and alloys
Neutron demonstrator system from Oxford Instruments showing (I to r) cyclotron, target moderator shield, object translator and imaging system
normally used in engineering components. Hydrogenous materials can therefore be imaged within components made up of such metals or alloys, and include such
X-ray, (above) and neutron radiography (below) images of 9 m m ammunition. The hydrogenous propellant is highly attenuative to neutrons, which pass through the metal outer casing with relative ease
0963-8695/94/03/0169-07 O 1994 Butterworth-Heinemann Ltd
substances as oil and other lubricants, adhesives and resins, water, and indeed corrosion - which is made up of hydrated metal oxides. It is even possible to obtain images of the flow of different liquids within metal components by doping with gadolinium, which is strongly attenuative and can act as a 'marker' for other applications, The properties utilized by the equipment are not new, but past use of neutron radiography has relied upon tapping the neutron flux within a nuclear reactor to obtain a suitably intense source for image clarity and real-time imaging (requiring short exposure times). This system focuses a 100/tA proton beam from the cyclotron onto a beryllium target, yielding 4 × 1012 fast neutrons per second, with the beam current, and hence the neutron stream, controllable in 1 /~A steps. The energy of the neutrons is also varied by the temperature of the moderator through which the neutrons pass between the target and component under inspection. This means that very heavy metal components
NDT& E International 1994 Volume 27, Number 3
169
- N e w equipment can be imaged (including iron up to 15 cm thick) using 'cold' neutrons, and materials analysis can be carried out by detection of prompt gamma emissions caused by high energy neutrons. The system has a footprint of 2.3 m x 2.8 m and is fully transportable. It can be transported in a standard ISO container or mounted on a scissor-lift platform for inspection of large static objects such as aircraft. It is also suitable for installation as part of a production line inspection system, and when complemented by X-radiography provides the means to locate and identify a wide variety of materials and defects in virtually any component.
Neutron Demonstrator Facility, Oxford Instruments, Osney Mead, Oxford, OX2 0DX, UK
Cable insulation condition monitoring A multi-client project aimed at developing methods of nondestructive condition monitoring of cable insulation has been launched by ERA Technology. Testing, consultancy and failure analysis services are available under this scheme on a confidential, single-client basis. The launch follows the recent completion of a three-year multi-client research project into the life of extruded polymeric cable insulation which produced a number of important results. The work was conducted using specialist ERA techniques, such as the veneering of insulation into a continuous length of thin tape, followed by electrical testing, thermal analysis and infrared spectrometry.
170
One of the findings of the project was that the life of cross-linked polyethylene (XLPE) cable insulation is significantly reduced if the XLPE is in direct contact with the pvc sheath without the presence of an intervening impervious metallic barrier layer. During thermal ageing of such a cable, chemical products from the pvc migrate into the insulation and reduce its ac and dc electric strength. Migration of phthalate based plasticizer can be identified using infrared spectrometry, although the actual degradation process occurring in the XLPE is less well defined. Measurement of cables subjected to accelerated ageing at 9 0 C for one and two-year periods has shown a reduction in the dc electric strength of the insulation by as much as 50% and this has been related to the ac performance of the insulation. The influence on electric strength has been shown to be reduced if the ageing is carried out in nitrogen instead of air, and this provides some clue as to the mechanism of degradation. High ageing temperatures are not necessarily required for plasticizer migration, as it has been observed even after thermal ageing at temperatures as low as 40°C.
ERA Technology Ltd, Cleeve Road, Leatherhead, Surrey KT22 7SA, UK
Locating s e w e r and borehole faults ERA Technology, on behalf of a European consortium, has completed the first stage in the development of a radar system for inspecting the interior of sewers and boreholes.
N D T & E International 1994 Volume 27, Number 3
III
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Leaks in a sewer pipe can allow the surrounding soil to leach into the pipe, causing voids which increase progressively in size until the ground above collapses. It is therefore highly desirable to be able to detect the presence of these voids before failure occurs. Promising results have been obtained on a test rig using a 200 mm diameter sewer pipe, with voids as small as 50 mm diameter being detected in both dry and water-logged ground. A 150 mm plastic pipe running through the test rig at 90' was also detected, as was the air/soil interface 1 m above the sewer pipe. The final inspection system will consist of an electronically scanned, four-quadrant array, capable of detecting voids 360" around the pipe. The antennas and rf electronics will be mounted on a motor drive unit, with digital data being relayed to the surface via an umbilical link. Complex signal processing at the surface can be used to enhance the radar data, producing images of the surroundings.
ERA Technology Ltd, Cleeve Road, Leatherhead, Surrey KT22 7SA, UK
Calibration test systems for thermal imagers Sira Test & Certification (ST&C) has extended its calibration service by introducing radiometric calibration of test systems for thermal imagers. Traceable to national standards, the calibrations establish the amount of measurement distortion introduced by the test systems when they are
Neutron demonstrator system from Oxford Instruments showing (I to r) cyclotron, target moderator shield, object translator and imaging system
normally used in engineering components. Hydrogenous materials can therefore be imaged within components made up of such metals or alloys, and include such
X-ray, (above) and neutron radiography (below) images of 9 m m ammunition. The hydrogenous propellant is highly attenuative to neutrons, which pass through the metal outer casing with relative ease
0963-8695/94/03/0169-07 O 1994 Butterworth-Heinemann Ltd
substances as oil and other lubricants, adhesives and resins, water, and indeed corrosion - which is made up of hydrated metal oxides. It is even possible to obtain images of the flow of different liquids within metal components by doping with gadolinium, which is strongly attenuative and can act as a 'marker' for other applications, The properties utilized by the equipment are not new, but past use of neutron radiography has relied upon tapping the neutron flux within a nuclear reactor to obtain a suitably intense source for image clarity and real-time imaging (requiring short exposure times). This system focuses a 100/tA proton beam from the cyclotron onto a beryllium target, yielding 4 × 1012 fast neutrons per second, with the beam current, and hence the neutron stream, controllable in 1 /~A steps. The energy of the neutrons is also varied by the temperature of the moderator through which the neutrons pass between the target and component under inspection. This means that very heavy metal components
NDT& E International 1994 Volume 27, Number 3
169
- N e w equipment can be imaged (including iron up to 15 cm thick) using 'cold' neutrons, and materials analysis can be carried out by detection of prompt gamma emissions caused by high energy neutrons. The system has a footprint of 2.3 m x 2.8 m and is fully transportable. It can be transported in a standard ISO container or mounted on a scissor-lift platform for inspection of large static objects such as aircraft. It is also suitable for installation as part of a production line inspection system, and when complemented by X-radiography provides the means to locate and identify a wide variety of materials and defects in virtually any component.
Neutron Demonstrator Facility, Oxford Instruments, Osney Mead, Oxford, OX2 0DX, UK
Cable insulation condition monitoring A multi-client project aimed at developing methods of nondestructive condition monitoring of cable insulation has been launched by ERA Technology. Testing, consultancy and failure analysis services are available under this scheme on a confidential, single-client basis. The launch follows the recent completion of a three-year multi-client research project into the life of extruded polymeric cable insulation which produced a number of important results. The work was conducted using specialist ERA techniques, such as the veneering of insulation into a continuous length of thin tape, followed by electrical testing, thermal analysis and infrared spectrometry.
170
One of the findings of the project was that the life of cross-linked polyethylene (XLPE) cable insulation is significantly reduced if the XLPE is in direct contact with the pvc sheath without the presence of an intervening impervious metallic barrier layer. During thermal ageing of such a cable, chemical products from the pvc migrate into the insulation and reduce its ac and dc electric strength. Migration of phthalate based plasticizer can be identified using infrared spectrometry, although the actual degradation process occurring in the XLPE is less well defined. Measurement of cables subjected to accelerated ageing at 9 0 C for one and two-year periods has shown a reduction in the dc electric strength of the insulation by as much as 50% and this has been related to the ac performance of the insulation. The influence on electric strength has been shown to be reduced if the ageing is carried out in nitrogen instead of air, and this provides some clue as to the mechanism of degradation. High ageing temperatures are not necessarily required for plasticizer migration, as it has been observed even after thermal ageing at temperatures as low as 40°C.
ERA Technology Ltd, Cleeve Road, Leatherhead, Surrey KT22 7SA, UK
Locating s e w e r and borehole faults ERA Technology, on behalf of a European consortium, has completed the first stage in the development of a radar system for inspecting the interior of sewers and boreholes.
N D T & E International 1994 Volume 27, Number 3
III
I
i
I
f
Leaks in a sewer pipe can allow the surrounding soil to leach into the pipe, causing voids which increase progressively in size until the ground above collapses. It is therefore highly desirable to be able to detect the presence of these voids before failure occurs. Promising results have been obtained on a test rig using a 200 mm diameter sewer pipe, with voids as small as 50 mm diameter being detected in both dry and water-logged ground. A 150 mm plastic pipe running through the test rig at 90' was also detected, as was the air/soil interface 1 m above the sewer pipe. The final inspection system will consist of an electronically scanned, four-quadrant array, capable of detecting voids 360" around the pipe. The antennas and rf electronics will be mounted on a motor drive unit, with digital data being relayed to the surface via an umbilical link. Complex signal processing at the surface can be used to enhance the radar data, producing images of the surroundings.
ERA Technology Ltd, Cleeve Road, Leatherhead, Surrey KT22 7SA, UK
Calibration test systems for thermal imagers Sira Test & Certification (ST&C) has extended its calibration service by introducing radiometric calibration of test systems for thermal imagers. Traceable to national standards, the calibrations establish the amount of measurement distortion introduced by the test systems when they are