Indistructive Portable Control Equipment
Development of Fast Neutron Radiography and Tomography Methods Based on a Portable Equipment
Tech Area / Field
3 Approved without Funding
All-Russian Research Institute of Automatics, Russia, Moscow
- FIAN Lebedev, Russia, Moscow
- Massachusetts Institute of Technology (MIT), USA, MA, Cambridge\nTechnische Universität München, Germany, Munich\nLawrence Livermore National Laboratory, USA, CA, Livermore\nInternational Atomic Energy Agency, Austria, Vienna
Project summaryThe main objective of the Project is the development of fast neutron radiography and tomography methods employing a portable neutron equipment to give a new instrumentation for non-destructive inspection "in situ", that is, where the object is located or produced.
The Project accumulates the experience, know-how and results obtained by the participating Institutions during the implementation of the ISTC Project #211-95 «Development of Industrial Transportable Neutron Defectoscope for Testing of Materials and the Most Important Items in Aircraft, Space, Fuel and Atomic Industries - DEFEKTOSKOP ». Implementation of the Project will result in the development of the integrated equipment providing in situ realisation of neutron radiography and tomography methods both with thermal and fast neutrons and due to that will increase possibilities of practical application of the results of the previous Project.
Fulfilment of the Project tasks will help to make fast neutron radiography and tomography methods available in many fields of industrial and non-industrial inspection. In particular adoption of these methods will allow to increase reliability of some critical components of high-risk technologies and to prevent those failures which could have catastrophic consequences in terms of losses of human lives, environment disasters and loss of expensive equipment. Key examples of these components include metallic and ferroconcrete frameworks of civil buildings, bridges, gates of shipping locks and so on. In view of problems of global security possibility to inspect content of metallic containers and vessels is of grate importance for preventing illegal trafficking and smuggling of nuclear arms and materials, narcotics, explosives and toxic chemicals. Bringing fast neutron radiography and tomography into practice will allow:
· to get a new instrumentation for inspection of a wide range of articles containing concurrently light and heavy chemical elements, isotopes as well;
· to diminish, to great extend, limitations on size and chemical composition of inspected articles often met when X-ray and thermal neutrons are used;
· to perform non-destructive testing “in situ” using high penetration ability of neutrons.
Nowadays the main activities in the considered area are related to:
· study of potential fields of application of fast neutron radiography and tomography methods;
· development of various fast neutron sources (including mobile);
· development of novel efficient detectors for imaging fast neutron fields;
· development of data processing algorithms.
The development of a stationary facility for radiography of fuel elements and assemblies has been carried out in the Hanford laboratory (USA) (C.N Jackson, J.P. Barton, E.A. Proudfoot, "Materials Evaluation", 1979, v. 37, N 7, 55-61). With a productivity of 240 radiograms per 8 hours, this device is a rather specialised and bulky facility, because the neutron source is a reactor.
Systematic work on the development of fast neutron tomography has been carrying out for a decade at the Technical University of Munich (TUM) (Germany) on the basis of the FRM-I research reactor (G. Pfister, A. Schatz, C. Siegel, E. Steichele, W. Waschkowski, and T. Bucherl, Nuclear Science and Engineering: 110, 303-315, 1992). The method developed up to the moment is based on the use of a few neutron counters and therefore has a low productivity (about one hour per projection). The type of the source does not allow to use it for “in situ” inspection.
Broad activity on the development of mobile fast neutrons sources and detectors is observed nowadays in Japan (Koji Yoshi, Kenzo Miya, Norihiko Katoh, Journal of Nuclear Science
and Technology, 30 (12), 1275-1282, 1993). A rather efficient two co-ordinate detector has beendeveloped on the basis of a silicon image converter and luminescent screen optimised for fast neutrons. At present, isotope sources, a cyclotron and a nuclear reactor are used in Japan for the fast neutron radiography development. It is necessary to note, that up to now these sources have not been used for “in situ" inspection due to low luminosity, deficient ecological safety, and rather large size, as well.
Development of a transportable radiographic installation utilising fast neutrons is being carried out actively in the USA (R.C. Lanza, D.W. Fink, E.B. Iverson, et. al. Proceedings of the 5-th World Conference on Neutron Radiography, 99-104, June 17-20, 1996, Berlin, Germany).
The analysis of state of the art in the considered field shows, that the prospects for wide practical application of fast neutrons are concerned with the development of an efficient and ecologically safe portable (or movable) equipment. One of perspective ways to make such an equipment available is use and enhancement of abilities of fast neutron generators with sealed neutron tubes and development of computerised registration systems based on a two-dimensional efficient detector and sophisticated software.
The participating Institutions occupy advanced positions in the key areas of the Project. The ideas forming the basis of the Project and some related results have been published in:
· Proceedings of the 5-th World Conference on Neutron Radiography, pp. 456-462 (June 17-20, 1996, Berlin, Germany);
· Proceedings of the V International Seminar on Interaction of Neutrons with Nuclei, pp. 269-275, E3-97-213, (Dubna, Russia, May 14-17, 1997);
· Reports of the International Atomic Energy Agency: 1) IAEA/PS/RCM97-1 (IAEA HQ, Vienna, 15-18 July, 1997), 2) IAEA/PS/RCM98-2 (IAEA HQ, Vienna, 17-20 November, 1998);
· Abstracts of the 6-th World Conference on Neutron Radiography pp. 74, 194 (Osaka, Japan, May 17-21, 1999,);
· Proceedings of the International Conference “Nuclear Energy in Central Europe ‘99” vol. 2, pp. 725-730, 747-754 (Portoroћ, Slovenia, September 6-9, 1999);
· Journal “Nuclear Instruments and Methods in Physics Research”, A 424 (1999) 48-52.
The Project implementation will allow:
· to develop a portable equipment and on its basis a technology of non-destructive in situ inspection in high risk industries being in compliance with the up-to-date requirements;
· to develop scientific and technological background for manufacturing a portable equipment for neutron radiography and tomography;
· to develop mathematical apparatus, algorithms and software for real time processing and visualising radiographic and tomographic data;
· to elaborate recommendations for practical use of the developed equipment and methods;
· to combine efforts of the partners on putting the results into practice.
The Project implementation will also secure a peaceful alternative engagement of weapon scientists of participating Institutions. Financial support of the Project would provide stable activity of the Project team in the considered area and prevent its dissolution and unwanted dispersal.
Foreign collaborators occupy advanced positions in the area of the Project as well. The Munich Technical University (Germany) has been developing fast neutron radiography and tomography methods for many years now.
The Massachusetts Institute of Technology (USA) has also been working in this area along with other US laboratories. The P.N. Lebedev Physics Institute co-operates with the TUM in the frame of the Agreement about academic co-operation on neutron radiography and tomography, with other European Institutions via the European Co-operation program on Science and Technology (COST action 524) and with the MIT in the frame of the IAEA co-ordinated research program “Bulk Hydrogen Analysis using neutrons”. There is a routine of information exchange, joint experiments and publications. The Project implementation will allow to broaden the existing practice to participating of foreign collaborators in:
· development of general technical requirements for the facility;
· testing of the generator, detector system, pilot sample of the facility and software;
· investigation of prospects of practical application of the results.
The results of the Project will be presented as joint reports and publications on meetings of the European Neutron Radiography Working Group, meetings concerned with the COST action 524, World Conferences as well.
The technical approach is based on use of:
· original technical solutions for the development of portable neutron generators;
· know-how for the development of two co-ordinate fast neutrons detectors;
· stochastic methods for the development of mathematics of algorithms;
· mathematical simulation of fast neutrons interaction with units of the facility and samples made of different materials.
The necessary characteristics (efficiency of generation, reliability, resource, etc.) of the neutron generator will be provided by means of:
· special configuration of the magnetic field ensuring more efficient deuterium and tritium ionisation in the neutron tube;
· circuit of the high-voltage source with a feedback;
· built - in microprocessor system for the tube parameters monitoring;
· original algorithm for monitoring the tube operation;
· designing of a built-in cooling system.
Conceptually the two co-ordinate detector is a luminescent detector and consists of a luminescent screen, a photosensitive device, a fast optics and an image intensifier. While developing the detector it is planned to carry out:
· comparative study of applicability of various luminescent materials;
· comparative study of applicability of such photosensitive devices as: a CCD-matrix, a CMOS-chip, a MRS-structure and a bipolar matrix device;
· experimental investigation of radiation resistance of the detector elements for fast neutron and gamma-radiation;
· investigation of contribution of the background radiation to the image.
It is quite important that the algorithm of data processing has to take into account correctly the peculiarities of measurements with fast neutrons.
In this connection it is supposed to investigate:
fast neutrons interaction with samples of various structure and sizes calculating spectrum, amount and angular distribution of scattered neutrons, doses and spectrum of gamma-radiation;
· impact of measurement conditions on characteristics of the neutron image;
· factors determining the image quality;
· ways of decreasing the background caused by scattered neutrons and gamma-radiation.
Mathematical simulations of the facility operation and necessary experiments will be carried out for this purpose.
Advantages of the Maximum Likelihood Algorithm developed by the Project team will be used for tomographic reconstruction to solve problems concerned with low signal-to-noise ratio of the data due to comparatively low luminosity of the neutron source.
Total labour costs for the whole project is 597.47 man-months; project duration - 30 months.
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