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Device for High-Energy Neutronography

#3474


Creation Possibility Substantiation and Development of Experimental Device for Visualization of Neutron Flow with Energy of More than 10 MeV Flowed through High Density Object

Tech Area / Field

  • ENV-MIN/Monitoring and Instrumentation/Environment

Status
3 Approved without Funding

Registration date
01.03.2006

Leading Institute
VNIIEF, Russia, N. Novgorod reg., Sarov

Supporting institutes

  • Institute of General Physics named after A.M. Prokhorov RAS, Russia, Moscow

Collaborators

  • Los Alamos National Laboratory / Nonproliferation and International Security Division, NIS-5, Safeguards Science & Technology, USA, NM, Los-Alamos

Project summary

The main goal of the project is to prove the possibility of creation and to develop the experimental device, which transduces high-energy neutron flow, passed through the explored high-density object to the image of high quality.

Last decades besides widely used X-radiography some branches of industry use neutronography (Dynamic Neutron Radiography-DNR) as the additional method for investigation of some objects. Geography and scope of application of this research method constantly extends. It is possible to judge it from the materials, for example, of Sixth World Conference on Neutron Radiography (Osaka, Japan, May 17-21, 1999).

Researches demonstrating the possibility to use fast neutrons (high-energy neutronography) for study of high-density objects that can’t be studied by other nondestructive methods, including X-radiography, are now being conducted (for example, /1/).

High-energy neutronography (with neutron energy of 10-15 MeV) is rather new method having advantages over usual X-radiography. These advantages are rather essential at determination and investigating of the objects having construction elements made of substance with low Z-value and strongly shielded by substances with high Z-value. Advantages are caused by stronger ability of high-speed neutrons to penetrate through high-density materials. Now in papers of Livermore National Laboratory (LLNL) /1/ it is reported, that spacial resolution of ~1 mm is achieved in high-energy neutronography. However, it is approximately ten times worse than in X-radiography. Improvement of this parameter of neutronography will sharply increase opportunities for high-density objects internal structure studying. Creation of converters with better characteristics will make it possible to expand high-energy neutronography application area. Now the significant efforts in this field are applied to the decision of this very problem /2-7/, /http://www.me.psu.edu/faculty/cimbala.html/.

In this project the possibility of creation of the device with special resolution, which is not worse than that of modern converters (for example, of flat plastic scintillator) and with higher brightness of the image is considered. Scientists involved in the project suppose that higher brightness of the image will enable to reduce time of exposition, and also to increase contrast and resolution. It enables to use more wide range of neutron sources – from radioactive neutron sources to accelerators and pulse nuclear reactors.

In this project it is proposed to improve design and manufacturing technique of the device with such parameters as high brightness and spacial resolution that is not worse than that of modern converters used in neutronography.

Basic novelty. As against used in neutronography flat plastic scintillator, the suggested device transforms neutron energy at two stages. At the first stage paraxial neutron beam flows through researched object and gets to the active element of the device, in which there are thin (of ~ 2-5 micron) layers made of highly enriched fissile material - U235. Getting in uranium layers, neutrons cause U235 nuclear fission. At the second stage high-energy (of ~100 MeV) U235 fission fragments escape to chamber (channel) filled with mix of rare gases. U235 nuclear fission products lose energy in gas mix and excite it. Excitation of the gas causes optical radiation, which is registered at the exit from the channel by digital pyroelectric chamber. Optical radiation intensity is almost proportional to neutron flow intensity.

Suggested project is the applied research. New direction in physics and high-energy neutronography technique will be created during project performance. The software for modeling, calculation and optimization of neutron flow energy transformation to fission fragments energy and for image registration of researched objects internal structure will be developed. It will enable to evolve methods of suggested neutronography technology optimization.

Scientists involved in this project have great experience of researches in the area of using and conversion of neutron flux energy to optical radiation for various scientific and applied purposes. These results were many times published in different scientific magazines and were submitted to conferences /8-38/. High qualification level of project participations and large preliminary work guarantee successful accomplishment of the project.

Russian weapon scientists and engineers will be involved in the project. Their total effort and amount of financing come to 65%. Research team close cooperation with the collaborators will promote integration of Russian scientists into the international scientific community. The project provides for carrying out of researches in new area of high-energy neutronography, and will promote both different products technical control opportunity development and solving the problem of studying internal structure of high-density objects that can’t now be controlled and investigated by the method of X-radiography. As the result of project accomplishment the group of performers involved in it will get steady scientific relations that will further enable to develop both fruitful international scientific programs, to expand their scope and, thus, to require the financial help of the state less. Thus, accomplishment of the project will promote transition to the market economy meeting to civil needs.

Expected duration of the project is 3 years.

All expected amount of work is pided into main tasks, including:

  • theoretical substantiation of opportunity to make the device converting high-energy neutron energy to optical radiation with high image brightness in two phases;
  • determination of experimental model construction;
  • solving of main technological problems at its developing;
  • intercomparison of characteristics of the existing flat plastic scintillator and the developed device, and working out of possibility to improve technical characteristics of the device.

All these tasks are in close connection, and at the same time some of them will be performed concurrently.

Complexity and universality of project tasks caused the participation of three research teams from RFNC VNNIIEF (Sarov), NII AR (Dimitrovgrad) and GPI RAS (Moscow). Their common mutually complementing experience of previous researches enables to count on successful accomplishment of above tasks and achievement of declared aims.

Foreign collaborator’s participation in the project will promote the project successful accomplishment. Information exchange, consultations, joint symposia and seminars during project performance are scheduled.


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