Background

The C-BORD legacy

The ENTRANCE project is partly going to build on the findings and achievements of the C-BORD project. This H2020 project terminated in November 2018 and was concerned with developing and testing a comprehensive cost-effective TRL-7 solution for the generalised inspection of container and largC-BORD Passive Detection Features includede-volume freight in order to protect EU borders, coping with a large range of container non-intrusive inspection (NII) targets, including explosives, chemical warfare agents, illicit drugs, tobacco, stowaways and Special Nuclear Material (SNM).

As a reminder, the objectives pursued by C-BORD and the Toolbox which was designed and developed under the project are detailed below.

C-BORD objectives

High-level objectives

By developing, combining, trialling and assessing complementary NII technologies in a comprehensive cost-effective solution, C-BORD aimed to:

• Increase the efficiency in container non-intrusive inspection (NII).
• Reduce false negative and false positive alarms.
• Maximise effectiveness and reduce safety risks for custom agents when opening containers for inspection.
• Lay the groundwork for the standardisation of requirements and test procedures for evaporation-based detection systems used to inspect large volume freight.

Technical objectives

• Provision of a general and multi-disciplinary C-BORD Framework for building comprehensive container inspection solutions, allowing stakeholders (customs officials, terminal operators, freight forwarders) to analyse key issues, fine-tune their requirements, and design and develop holistic solutions by fitting and assessing user needs against a list of general criteria.
• Development of a C-BORD Toolbox of TRL-7 first-line & second-line devices employing different non-destructive passive and active techniques: Advanced Radiation Management / Next Generation Cargo X-Ray / Tagged Neutron Inspection / Photofission / Evaporation Based Detection
• Development of a unique Graphical User Interface (GUI), data fusion display, decision support software and common data format.
• Elaboration of recommendations and tools for standardised tests for the different C-BORD NII technologies.

C-BORD Toolbox

Advanced Radiation Management

Passive Neutron and Gamma Detection Sub-systems

In the C-BORD project, a new generation of Container Inspection Systems was developed which combined five technologies to provide advance inspection capabilities. Part of the project was dedicated to developing passive neutron and gamma detection sub-systems to be evaluated in use cases whose aims were to:

• Develop commodity and intelligence enhanced mobile / re-locatable passive detection systems with enhanced NORM classification, isotope identification (PVT and NaI versions) He-3 free neutron detection systems and advanced, intuitive visual detection information to integrate into C-BORD data-fusion systems.
• Demonstrate feasibility of using X-ray enhanced manifest data (automated X-ray generated intelligence e.g., tobacco detection algorithms) for enhanced tobacco detection, NORM classification and isotope identification.
• Demonstrate capabilities provided by reconstructed spectra using de-convolution enhancement on low and high energy photons and the quantitative nature of the technique for use in a range of applications.

C-BORD Passive Detection Features included:

• Fully stabilised crystal and PVT spectrometers providing very low false alarm rates and low nuisance alarm rates on Naturally Occurring Radioactive Materials (NORMs)
• High sensitivity He-3 free 6LiZnS detectors
• Integration of new scintillation materials which offer increased material discrimination
• Detection system adapted for non-stop, higher speed lorry transits with SNM specific and material discrimination capabilities
• Advanced passive gamma and neutron screening component technologies will be adapted and optimised to leverage the signal discrimination capabilities of other C-BORD sub-systems
• Targeted inspection for nuclear materials and decay chain verification in collaboration with X-ray inspection, rapidly re-locatable TNIS and Photofission

Next Generation Cargo X-Ray

In the C-BORD project, a new generation Container Inspection System was foreseen and resulted in an advanced system, combining X-ray techniques capable of localizing objects inside a large volume (cargo container) at a high rate, and additional techniques more sensitive to specific substances, such as the Passive Technologies, the Tagged Neutron Inspection Systems, the Photo-fission technologies, and sniffers.

The C-BORD project was also an opportunity to improve X-ray techniques, particularly with regard to the accuracy of the material discrimination and also to help the image interpretation (Assisted / Automatic Target Recognition)

C-BORD X-ray Techniques:

The issue at stake: the X-ray techniques have developed significantly over the past 20 years for cargo screening. They include an ability to classify materials and objects according to the atomic number Z. Like any radiographic technique used in medical diagnosis, industrial control or luggage screening, they allow visualizing the inside of a truck or container.

The strength of the X-ray techniques lies in their ability to provide and localize shapes and chemical information of objects in a cargo container at a rather high speed. However, it consists in the projection of a 3D volume (cargo container) on a 2D plane overlaying all the plans and all thicknesses. This results in a mixing of shapes and materials inevitably bringing, in some locations, a bit of confusion and ambiguities. Moreover these methods are thus poorly sensitive to specific substances.

Improvements brought by the C-BORD X-ray Technology: 

• Global X-ray image improvements
• Chemical separation of overlapping objects
• Improved material classification in the organic range
• Improvement of the accuracy of X-ray images in terms of transmission measurements (hardware and software means)
  • Attenuation corrected from the effects of the scattered radiation
  • Attenuation corrected from the effects of the variation of the dose and energy of the incident beam
   
• Improvement in material classification:
  • Solution to the problem of overlays
  • Increase of the number of discrimination classes (organic category)
  • Development of HEMD on low dose and low weight systems (less than 15 tons)

Tagged Neutron Inspection System

In the C-BORD project, focus was put on a new generation of Tagged Neutron Inspection System (TNIS) for cargo containers: the first Rapidly Relocatable Tagged Neutron Inspection System (RRTNIS). The RRTNIS was meant to be a second-line system to be used on sealed containers, enabling the detection of explosives, illicit drugs and chemical agents in a suspect voxel (elementary volume unit).

TNIS Measurement Technique:

The early system named Tagged Neutron Inspection System (TNIS) [1] uses an associated-particle sealed neutron generator to detect explosives or other threat materials concealed in cargo containers. The neutron generator, with a built-in segmented alpha particle detector, is used to produce a 14 MeV neutron and an alpha particle through the D+T fusion reaction. The position of the alpha particle defines the direction and time of the neutron emission, since the two particles are emitted simultaneously and almost back-to-back. Gamma rays induced by neutron inelastic scattering on the elements of the cargo material are detected in coincidence with the alpha particle. The time delay between alpha and gamma detection determines the depth in the container where the neutron interaction took place.

The TNIS New Generation Design:

The experience gained in past EU projects such as EURITRACK [2], ERITR@CK [3] and national projects such as SLIMPORT [4] and UNCOSS [5] had shown the capability to determine the type of material present in a given point inside the cargo by remotely measuring the elemental ratios in that point (i.e. gamma rays emitted in fast neutron reactions characterize carbon, oxygen and nitrogen, which are the major components of explosives or narcotics). Second generation TNIS advanced to the point where a rapidly relocatable system could be designed, taking advantage of recent electronics and neutron generator developments, especially in terms of compactness. Using the expertise gained with the previous projects, a high performance RRTNIS was designed with a high-level user-friendly interface.

C-BORD RRTNIS Expected Innovations included:

• The integration of a recent, miniaturized, high-performance associated particle neutron generator; 
• A newly designed compact and transportable shielding for radiation hazard, thus reducing the size of the restricted area;
• The optimisation of the duration of data-taking by using advanced information processing and state-of-the-art gamma detectors with enhanced energy resolution to improve identification of warfare agents and dangerous chemicals;
• The improvement of the analysis through enhanced de-convolution algorithms of the gamma spectra to enhance material identification algorithms;
• The embedding of a new visual user interface, which was crucial to improve TNIS capability in threat identification.

References

[1] S. Pesente et al. “Tagged neutron inspection system (TNIS) based on portable sealed generators, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 241, Issues 1–4, December 2005, Pages 743-747

[2] EURITRACK project: http://www.euritrack.org

[3] C. Carasco et al. “In-field tests of the EURITRACK tagged neutron inspection system”, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Volume 588, Issue 3, 11 April 2008, Pages 397–405.

[4] D. Cester, et al., “Special nuclear material detection with a mobile multi-detector system”, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Volume 663, Issue 1, 21 January 2012, Pages 55–63

[5] C. Eleon, B. Perot, C. Carasco, D. Sudac, J. Obhodas, V. Valkovic, “Experimental and MCNP simulated gamma-ray spectra for the UNCOSS neutron-based explosive detector”, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 629, Issue 1, 11 February 2011, Pages 220-229

Photofission

Context: the detection of SNM (Special Nuclear Material – mainly uranium and plutonium isotopes) is a crucial issue for homeland security applications in order to prevent illicit trafficking. Non-destructive techniques are well-suited to cargo container inspection particularly because they are non-intrusive and do not require opening the container, which is a time consuming and potentially dangerous process.

Non-destructive Methods

Non-destructive passive methods are based on the detection of particles spontaneously emitted by radionuclides of interest, mainly gamma and neutron emissions. However, these passive emissions can easily be impacted by the presence of shielding around nuclear material and by the poor passive emission of actinides (especially for uranium isotopes).

Non-destructive active methods dedicated to SNM detection are an efficient solution when non-destructive passive methods encounter this type of limitation.

The Photofission Techniques

These active techniques are two-step processes based on the fission reaction:

• Irradiation step in order to irradiate nuclear material and produce fission reactions; 
• Detection step dedicated to the measurement of prompt and delayed particles emitted by fission products.

Fission reactions are induced by high-energy photons (exceeding 6 MeV energy) delivered by a linear electron accelerator (LINAC) and identified under the technical term “photofission”. This highly penetrating incident photon beam is well adapted to the analysis of cargo containers. Several previous developments showed the potential of using photofission techniques for cargo container scanning in the context of homeland security applications. For example, the DEMIP project led by CEA LIST was a proof-of-concept step in order to demonstrate the experimental feasibility of this approach on mock-up containers.

Development of the First European Photofission Prototype by C-BORD:

Based on this background know-how, a main technical issue of the C-BORD project was related to the development of the first European photofission prototype able to be deployed in a harbor environment. The objectives of this development were the following:

• Design a photofission system based on a 9 MeV LINAC and combining several specific sub-systems (delayed neutrons, prompt neutrons, high-energy delayed gamma-rays, SNM identification features)
• Improve sub-systems enabling detection of prompt and delayed particles emitted by photofission reactions
• Provide strong association concerning coupling between high-energy imaging techniques and photofission measurements

Deployment of the Prototype

Within the C-BORD project the final purpose of these developments consisted in the deployment of this non-destructive active system in the Rotterdam harbor. A crucial step of this final demonstration was the integration of the photofission detection module in the current dual view X-ray imaging system set up in the Rotterdam harbor (two 9 MeV LINACs used for high-energy imaging purposes).

Evaporation-based detection

The C-BORD Technology Sub-System evaporation-based detector aimed to develop detection technologies for volatile chemicals that may be present in a container, giving warning of hazard or contraband. These were expected to complement X-ray imaging by enabling molecular specific detection (chemical information instead of physical properties), improving the discrimination power of the scanning system.

Previous sniffing approaches failed because of the complexity of the problem at hand:

C-BORD New Approach:

A new biomimetic approach to detection and identification of volatile chemicals was employed, coupling selective binding elements from biological systems – such as OBP (Odorant Binding Proteins) – with highly sensitive diamond microcantilever and machine learning. It also increased the selectivity of the detector by arranging the biosensors in an array.

Each individual sensor in the array was containing a specific OBP featuring a fairly broad selectivity to some chemicals or families of chemicals. The combination of the response of the sensors to a particular odour was translated into a pattern which is a fingerprint of the specific odour. A multiparametric software used a database built during an initial calibration phase of the system to recognise and classify the volatile chemicals.

Results:

• New OBPs were functionalized to detected analytes to cover the priority targets identified by customs.
• Sampling methods were developed to allow the use of the device in the context of cargo screening. With many targeted substances having very low volatility or being potentially in sealed packets, the detection of these substances was requiring the integration of a large scale pre-concentration and sampling system. COTS large volume sampling methods as well as evaporation based detection systems were therefore investigated.
• Test standards and procedures were designed to make them available for large cargo inspection. Reliability of sniffing detectors (not only the C-BORD ones) were increased by in-field evaluation and testing.
• A laboratory test-bed for the simulation of hidden illicit material in large volume cargo was built for the evaluation of sampling systems and evaporation based detector technologies.
• Based on information from users, emission sources with defined emission rates for a variety of explosives and narcotics which can be handled safely with reduced legal constraints were developed. This included point sources as well as large volume or area sources which could be placed into large volume freight to mimic the emission of contraband.