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Gamma-Neutron Detector

#2852


Development of a Dual Gamma-Neutron Detector Based on Xenon and He-3 Gas Mixture for Identification of Radioactive and Fissile Materials

Tech Area / Field

  • INS-DET/Detection Devices/Instrumentation
  • ENV-MIN/Monitoring and Instrumentation/Environment
  • INF-SOF/Software/Information and Communications

Status
3 Approved without Funding

Registration date
01.08.2003

Leading Institute
MIFI, Russia, Moscow

Supporting institutes

  • All-Russian Research Institute of Automatics, Russia, Moscow

Collaborators

  • Pacific Northwest National Laboratory / Battelle, Putting Technology to Work, USA, WA, Richland\nMirmar Sensor LLC, USA, CA, Santa Barbara\nLos Alamos National Laboratory / Nonproliferation and International Security Division, NIS-5, Safeguards Science & Technology, USA, NM, Los-Alamos\nLos-Alamos National Laboratory / Advaned Technology Group, NIS-6, USA, NM, Los-Alamos

Project summary

As a result of accomplishment of the ISTC project, gamma-neutron detecting equipment (GNDE) will be built. The basis is a gamma-neutron detector filled with mixture of compressed xenon and 3He. The equipment is intended for concurrent detection and reliable identification of gamma-neutron radiation of various objects exploited in nuclear research and nuclear power. It can also be used in technological monitoring of nuclear fuel processing, reactor diagnostics, customs and other kinds of neutron and gamma-radiation sources control, and in particular, of fissile materials.

At present, the task of radioactive and fissile material storage and transfer control is imperative. To successfully solve it, new detection equipment capable of effective gamma-neutron radiation detection should be built. First and foremost, such equipment must provide high resolution and allow gamma radiation registration in a wide energy range (50-5000 keV). It is due to high energy resolution that the gamma-neutron detector being built will be effectively used to identify radio nuclides, as well as to estimate them quantitatively. Along with gamma radiation registration, the measurement of neutron fluxes being emitted by fissile materials enables us to effectively detect and in some instances to identify them.

There are various types of gamma detectors today. The most prevalent among them are semiconductor detectors based on very pure germanium (HPG) and scintillation (NaI, CsI). The former have record-breaking energy resolution (2 keV for 662 keV line), but are only able to function at cryogenic temperatures. This circumstance limits essentially their range of application. Besides, HPG are costly because of the expensive process of growing very pure germanium crystals. As far as the scintillation detectors are concerned, they provide high efficiency of registering gamma-quanta; they have energy resolution of about 60-80 keV. This means that their spectrometric ability does not allow dependable identification of radionuclides.

In addition to the detectors mentioned above, there is one more class of gamma detectors, using compressed xenon as a working substance. With respect to energy resolution, they are in an intermediate position between HPG and NaI detectors and provide resolution about 13-16 keV. These detectors were designed at MEPhI and at present they are being employed at different laboratories and institutions using them for detection and identification of radioactive and fissile materials.

Up-to-date neutron detectors (3He – counters, plastic scintillators, fission chambers etc.) are capable of registering neutron radiation in various energy ranges. To define energy spectrum of neutron radiation, hybrid neutron detectors are being used. One such detector has also been designed at MEPhI. In order to measure spectrum, it employs the effect of neutron absorption, depending on neutron energy, in various media.

It should be noted that all of the detectors mentioned are intended for registration of either gamma-quanta or neutrons.

To date, there have not been detectors that could measure gamma radiation with good energy resolution and register neutron radiation at the same time. Detection devices of this kind would be extremely useful to execute fissile materials nonproliferation control, since simultaneous registration of radiation of both types increases reliability of fissile materials detection. Application of a single detector for this purpose, capable of registering both gamma quanta and neutrons, is envisioned to be effective and useful.

In the proposed project the development and creation of a gamma-neutron detector of a new type is planned. As a working substance, it will employ a mixture of compressed xenon and 3He isotope. This detector combines spectrometric properties of xenon detectors and neutron counters based on 3He, which will allow providing high-energy resolution registration of gamma radiation (13-16 keV), and, at the same time, measuring the neutron fluxes.

To make a gamma-neutron detector of the new type, first of all, it is necessary to develop a special system for gas mixture (xenon and 3He) purification, to produce a working substance for gamma-neutron detectors.

It is also necessary to create a system for filling gamma-neutron detectors with the working substance, involving special equipment that will provide gas purity verification relative to electronegative admixtures.

One of the major tasks of this work is to define the main physical parameters of the gamma-neutron detector by means of simulation of the interaction of the processes between gamma-neutron radiation and the working substance, as well as to optimize its constructs, the dimensions of which depend on many different factors.

On the basis of the completed calculations, a complete set of design documentation necessary to manufacture all the constituent parts of the gamma-neutron detector will be developed.

Compact electronic blocks, being part of the detector and providing its functioning, will be developed simultaneously.

One of the midpoints of the new gamma-neutron detector’s creation is the process of preparing the Xe-3He mixture.

When all the main constituent parts are made, the gamma-neutron detector will be filled with the working substance, and the assembly and adjustment of all the electronic blocks will be carried out.

At the final stage of this project, a considerable effort will be carried out. It will be concerned with determining the operating mode of the equipment and accomplishing a wide range of calibrations and tests of all kinds, including a demonstration of testing with radioactive and fissile materials. This testing will be conducted for the purpose of quantitative evaluation definition, which will, in turn, characterize the possibility of the new equipment’s application for the detection and identification of these materials.

It is essential to develop the necessary software for the specified equipment to function, as well as for the processing of the experimental data. A considerable portion of the software will be related to the analysis of the information with the purpose of increasing the reliability of identifying fissile materials and their quantitative determination.

Solving the tasks proposed in this project requires attracting qualified experts who have experience in mathematical and physical simulation, development and fabrication of detection devices, and systems of information gathering and processing, software engineering, and conducting physical experiments. For years, the project development staff has been doing research on registration principle development and high-sensitivity gamma-neutron radiation detector design, as well as elaborating systems of information gathering from recording gear, and writing programs for its processing.

Among Russian scientific groups, the participants of the project have leadership positions in their subjects. The comparison of their scientific results with similar foreign published results shows their lead in several scientific directions. The main results of their work were published in the leading journals (about 100 articles) and presented many times at international conferences.

The main purpose of the project is to develop, create and demonstrate the capabilities of the new gamma-neutron spectrometer for detection and identification of nuclear materials.

For realization of goals and objectives of the project, it is planned that the following tasks will be solved:


- Development and creation of a highly efficient Xe and 3He purification system;
- Development and creation of a gas system for filling the gamma-neutron detector;
- Definition of the main physical parameters of the gamma-neutron detector by means of simulation of interaction processes between gamma-neutron radiation and the working substance, as well as the optimization of its constructs;
- Development of design documents for making the gamma-neutron detector;
- Development of the low noise charge sensitive amplifier;
- Development of the compact high voltage power supply;
- Manufacture the main modules and units of the gamma-neutron detector;
- Vacuum preparation of the detection part of the detector and filling it with the work substance;
- Combining and set up of electronic modules of the gamma-neutron detector;
- Combining and set up of the gamma-neutron detector;
- Development of software for control of the gamma-neutron detector functioning;
- Development of algorithms and software for identification of radioactive and fissile materials;
- Development of typical fissile materials database for software of identification of fissile materials;
- Carrying out the calibration of the new detector by using gamma-neutron sources and measuring its main characteristics;
- Carrying out the demonstration tests of the gamma-neutron detector by using radioactive materials.


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