Nabil Menaa

GAMPIX: A new gamma imaging system for radiological safety and Homeland Security Purposes

Localization of radioactive sources is a major issue for many applications in the nuclear industry. Gamma imaging is a powerful non-destructive technique, enabling to locate radioactive hot spots contained in a given area and well-adapted to this topic. Industrial gamma cameras have been commercialized by various companies for several years but present some limitations in terms of sensitivity, weight and ease of use in comparison with the requirements of end-users.

An evolution of technologies and applications of gamma imagers in the nuclear cycle industry

The tracking of radiation contamination and distribution has become a high priority in the nuclear cycle industry in order to respect the ALARA principle which is a main challenge during decontamination and dismantling activities. To support this need, AREVA/CANBERRA and CEA LIST have been actively carrying out research and development on a gamma-radiation imager. In this paper we will present the new generation of gamma camera, called GAMPIX. This system is based on the Timepix chip, hybridized with a CdTe substrate. A coded mask could be used in order to increase the sensitivity of the camera. Moreover, due to the USB connection with a standard computer, this gamma camera is immediately operational and user-friendly. The final system is a very compact gamma camera (global weight is less than 1 kg without any shielding) which could be used as a handheld device for radioprotection purposes. In this article, we present the main characteristics of this new generation of gamma camera and we expose experimental results obtained during in situ measurements. Even though we present preliminary results the final product is under industrialization phase to address various applications specifications.

Evaluation of the LANL hand held multiplicity register and Canberra JSR-15

Passive Neutron Coincidence Counting (PNCC) and Passive Neutron Multiplicity Counting (PNMC) techniques are important non destructive assay methods used in the quantification of plutonium and other spontaneously fissile materials across the fuel cycle. They are based on Multiplicity Shift Register (MSR) pulse train correlation analyzers such as the Canberra Multiplicity Shift Register (MSR) JSR-14. The JSR-14, although quite successful, is somewhat limited by a 4 MHz SR and has no front panel display. Los Alamos National Laboratory (LANL) has recently developed a hand-held multiplicity register (HHMR) that possesses a 50 MHz SR as well as an interactive front panel display with user settable parameters. Under CRADA (cooperative research and development agreement) guidelines, Canberra Industries will commercialize the product. The display and user interface allows for parameter entry and provides the user with feedback of the current operating parameters as well as the MSR results, e.g., multiplicity histograms. The higher MSR clock speed will provide functionality not previously possible under extreme counting conditions, e.g., waste assay with relatively high-gram quantities of heat source material. A prototype HHMR unit was obtained from LANL and has been tested. In this paper, we present the test results of the reliability of the unit, the user interface functionality, support for existing software, and the performance of the 50 MHz MSR. The reliability tests involved the integrity of the battery and voltage supplies, signal triggering performance, and the robustness of the PC USB/virtual COM port interface. The software compatibility tests were conducted using the latest available versions of the LANL INCC and Canberra NDA 2000 software packages. A 20 MHz de-randomizer board was installed into a Canberra neutron coincidence counter to examine the performance of the 50 MHz JSR-15 MSR as compared to the 4 MHz JSR-14 MSR The functionality of JSR-14 and HHMR at low instantaneous counting rates as well as high rates was tested using a random pulser, Am-Be and 252Cf sources. In this paper we report on the results for the tests conducted during the evaluation period.

Evaluation of the next generation gamma imager

Towards the end of their life-cycle, nuclear facilities are generally associated with high levels of radiation exposure. The implementation of the ALARA principle requires limiting the radiation exposure of the operating people during the different tasks of maintenance, decontamination and decommissioning. CANBERRAs latest involvement in the provision of nuclear measurement solutions has led, in the framework of a technology transfer agreement with CEA LIST, to the development of a new generation gamma imager. The latter, which is designed for an accurate localization of radioactive hotspots, consists of a pixilated chip hybridized to a 1 mm thick CdTe substrate to record photon pulses and a coded mask aperture allowing for background noise subtraction by means of a procedure called mask/anti-mask, which greatly contributes to the reduced size and weight of the gamma imager as gamma shielding around the detector is less required. The spatial radioactivity map is automatically superimposed onto a pre-recorded photographic (visible) image of the scene of interest. In an effort to evaluate the performances of the new gamma imager, several experimental tests have been performed on a industrial prototype to investigate its detection response, including photon sensitivity and angular resolution, over a wide energy range (at least from 59 keV to 1330 keV). The impact of the background noise was also evaluated together with some future features like energy discrimination and parallax correction. This paper presents and discusses the main results obtained in the above experimental study. A comparison with Monte Carlo simulations using the MCNP code is provided as well.

Performance of ADONIS-LYNX system for burn-up measurement applications at AREVA NC La Hague reprocessing plant

This work deals with the last measurement campaign done at the AREVA NC La Hague reprocessing plant with the new industrial ADONIS system called ADONIS LYNX. In this paper we briefly explain the ADONIS bimodal Kalman smoother. Next, we present the experimental set-up as well as the industrial approach for the ADONIS system. Results from measurement campaign are then discussed. Some ways of improvement are also explained.

BOOSTER: Development of a toolbox for triage of large group of individuals exposed to radioactive material

The effective management of an event involving the exposure of a large number of people to radioactive material requires a mechanism for fast triage of exposed people. BOOSTER is a project founded by the European Union under the Seventh Framework Programme, addressing this requirement. It is a capability project designed to provide an integrated system which could easily be deployed and used. For this purpose, the BOOSTER consortium, relying on the expertise of seven members, researches and develops new approaches to allow an effective and fast management of most kind of nuclear threats. BOOSTER System was designed to help first responders mitigating the crisis by providing the necessary information to quickly assess the radiological situation, to support triage staff in performing an efficient and fast categorization of the potentially affected victims, and to give medical staff crucial information for further treatment at medium or long term post-accident.

Mathematical efficiency calibration with uncertain source geometries using smart optimization

The In Situ Object Counting Software (ISOCS), a mathematical method developed by CANBERRA, is a well established technique for computing High Purity Germanium (HPGe) detector efficiencies for a wide variety of source shapes and sizes. In the ISOCS method, the user needs to input the geometry related parameters such as: the source dimensions, matrix composition and density, along with the source-to-detector distance. In many applications, the source dimensions, the matrix material and density may not be well known. Under such circumstances, the efficiencies may not be very accurate since the modeled source geometry may not be very representative of the measured geometry. CANBERRA developed an efficiency optimization software known as “Advanced ISOCS” that varies the not well known parameters within user specified intervals and determines the optimal efficiency shape and magnitude based on available benchmarks in the measured spectra. The benchmarks could be results from isotopic codes such as MGAU, MGA, IGA, or FRAM, activities from multi-line nuclides, and multiple counts of the same item taken in different geometries (from the side, bottom, top etc). The efficiency optimization is carried out using either a random search based on standard probability distributions, or using numerical techniques that carry out a more directed (referred to as “smart” in this paper) search. Measurements were carried out using representative source geometries and radionuclide distributions. The radionuclide activities were determined using the optimum efficiency and compared against the true activities. The “Advanced ISOCS” method has many applications among which are: Safeguards, Decommissioning and Decontamination, Non-Destructive Assay systems and Nuclear reactor outages maintenance.

Use of mathematical modeling in nuclear measurements projects

Mathematical modeling of nuclear measurement systems is not a new concept. The response of the measurement system is described using a pre-defined mathematical model that depends on a set of parameters. These parameters are determined using a limited set of experimental measurement points e.g. efficiency curve, dose rates… etc. The model that agrees with the few experimental points is called an experimentally validated model. Once these models have been validated, we use mathematical interpolation to find the parameters of interest. Sometimes, when measurements are not practical or are impossible extrapolation is implemented but with care. CANBERRA has been extensively using mathematical modeling for the design and calibration of large and sophisticated systems to create and optimize designs that would be prohibitively expensive with only experimental tools. The case studies that will be presented here are primarily performed with MCNP, CANBERRAs MERCURAD/PASCALYS and ISOCS (InSitu Object Counting Software). For benchmarking purposes, both Monte Carlo and ray-tracing based codes are inter-compared to show models consistency and add a degree of reliability to modeling results.

Latest expertise investigations in nuclear dismantling and industrial applications

During the last decades, CANBERRA has developed know-how, expertise and intervention strategies based on its feedback experiences in many countries. This document covers a wide range of applications involving nuclear characterization, for which CANBERRA is able to provide measurement set-up and results, activity characterization and radioactive source localization, as well as to guarantee safety or process thresholds corresponding to the customers needs. To improve processes best-in-class methodology, know-how and tools have been used in complex examples described in this paper. CANBERRA has demonstrated its ability to better and efficiently prepare for and execute decontamination and dismantling activities.