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Materials, instrumentation and techniques for the detection of Special Nuclear Material and Radioactive Sources: EU project MODES SNM
Full text linkMODES SNM project is part of the European Union effort to promote research and innovation in strategic topics; it includes seven participants from five different countries. The project aimed to carry out technical research in order to develop a prototype for a mobile, modular detection system for radioactive sources and Special Nuclear Materials (SNM). The project’s main goal was to deliver a tested prototype of a modular mobile system capable of passively detecting weak or shielded radioactive sources with accuracy higher than that of currently available systems.
The R&D involved in the project aimed at designing, constructing and testing robust, safe, and lightweight high pressure cells with an advanced read-out system, to be used as
basic components of the modular mobile system. These innovative cells use 4He and Xe as scintillation materials, exploiting the potential of noble gases in the field of radiation detection. Furthermore, a patented technology enabled the simultaneous detection of fast and thermal neutrons in the same detector, providing additional information on the possible presence of shielding around neutron sources. The final detector configuration for MODES SNM prototype includes 8 4He fast neutron tubes, 2 4He thermal neutron tubes, 1 xenon gamma ray tube and 1 NaI(Tl) gamma ray crystal.
A suitable Information System has been developed at Università degli Studi di Padova to manage the detectors, integrate and analyze the data, and provide to the user simple informations about the results of the inspections. The prototype was commissioned under laboratory conditions at NCBJ, a renowned European research establishment, then the detectors and the front-end electronics were mounted inside a van. Finally, a series of demonstrations took place in an on-field campaign driven by the end-user group established in the project.
Project MODES SNM concluded with full success on June 30th, 2014. Not only all the project milestones were achieved, but the prototype was completed on time and showed good performances. The technical requirements defined at the beginning of the project have been fulfilled, and during the demonstration tour the end users showed great appreciation to the final result of the work, to the satisfaction of all the Consortium partners. The project has been positively evaluated by EU officials, from the point of view of both the organization and the results. The prototype is now being developed at an industrial level by one of the project participants; an agreement has been signed with Universit`a di Padova for licensing the software written within the project.Il progetto MODES SNM è parte dello sforzo da parte dell’Unione Europea per promuovere la ricerca e l’innovazione in settori considerati strategici; include sette partecipanti da cinque diversi paesi. Il progetto punta a sviluppare una attivit`a di ricerca per lo sviluppo di un sistema mobile e modulare per la rivelazione di sorgenti radioattive e materiale speciale nucleare (SNM). L’obiettivo principale è la realizzazione di un prototipo funzionante capace di rivelare in modo passivo sorgenti deboli o schermate con precisione maggiore dei sistemi attualmente disponibili.
La ricerca e sviluppo svolta all’interno del progetto mirava alla costruzione di celle ad alta pressione robuste e leggere con un sistema di read-out avanzato, da usarsi come componenti di base del sistema mobile modulare. Queste celle innovative usano 4He e Xe come scintillatori, sfruttando il potenziale dei gas nobili nel campo della rivelazione di radiazione. Inoltre una tecnologia brevettata consente la rivelazione simultanea dei neutroni veloci e termici, fornendo così informazioni aggiuntive sulla possibile presenza di schermi intorno alle sorgenti. La configurazione finale dei rivelatori del prototipo di MODES SNM include 8 tubi ad 4He per neutroni veloci, 2 tubi ad 4He per neutroni termici, 1 tubo a xenon ed 1 cristallo NaI(Tl) per radiazione gamma.
Un apposito Sistema Informatico (IS) è stato sviluppato presso l’Università degli Studi di Padova per la gestione dei rivelatori, l’aggregazione e l’analisi dei dati, e per fornire all’operatore semplici informazioni riguardo i risultati delle ispezioni. Il prototipo è stato collaudato persso il centro NCBJ, una installazione di ricerca conosciuta in tutta Europa, quindi i rivelatori e l’elettronica sono stati installati dentro un van. Infine, una serie di dimostrazioni ha avuto luogo durante una campagna "sul campo" gestita dal gruppo di utilizzatori finali costituito all’interno del progetto.
Il progetto MODES SNM si è concluso con pieno successo il 30 giugno 2014. Non solo ha raggiunto tutti gli obiettivi, ma il prototipo è stato completato per tempo ed ha mostrato delle buone prestazioni. I requisiti tecnici definiti inizialmente sono stati rispettati, e durante le dimostrazioni gli utenti finali hanno espresso grande apprezzamento per il risultato finale del nostro lavoro, con soddisfazione di tutti i partecipanti del Consorzio. Il progetto è anche stato valutato positivamente dai funzionari europei incaricati della valutazione, sia sotto il punto di vista della gestione che dei risultati. Attualmente il prototipo sta venendo sviluppato a livello industrial da uno dei partecipanti; è stato raggiunto un accordo con l’Università di Padova per la licenza del software scritto durante il progetto
Experimental tests of the new plastic scintillator with pulse shape discrimination capabilities EJ-299-33
No full textWe have studied the prototype of a new plastic scintillator material (EJ-299-33) engineered for gamma-neutron discrimination. Energy and time resolutions as well as pulse shape discrimination capability have been compared with those of standard plastic and liquid scintillators. EJ-299-33 characteristics are somewhat poorer compared to standard scintillators. However, results obtained with the new plastic material suggest its possible use in basic research (time-of-flight measurements) as well as in Homeland Security applications (neutron/gamma monitoring device)
Neutron detection in a high gamma-ray background with EJ-301 and EJ-309 liquid scintillators
No full textUsing a fast digitizer, the neutron–gamma discrimination capability of the new liquid scintillator EJ-309 is compared with that obtained using standard EJ-301. Moreover the capability of both the scintillation detectors to identify a weak neutron source in a high gamma-ray background is demonstrated. The probability of neutron detection is PD=95% at 95% confidence level for a gamma-ray background corresponding to a dose rate of 100 uSv/h
Neutron detection in a high gamma ray background with liquid scintillators
No full textThe capability of liquid scintillator (namely 2” x 2” cells of EJ301 and EJ309) of detecting neutrons in a very high gamma ray background is explored. A weak 252-Cf source has been detected in a high 137-Cs gamma ray background corresponding to a dose rate of 100 uSv/h with probability of detection in compliance with IEC requirements for hand held instruments. Tests were performed with new generation of CAEN digitizers, in particular the V1720 (8 Channel 12bit 250 MS/s) one
Digital front-end electronics for a tagged neutron inspection system
No full textIn this paper, we shall present a simple VME front-end system that employs the FADC CAEN V1720 8- channel 12-bit 250-MS/s digitizer. This system produces coincidence spectra between the trigger particle and other detectors and it replaces the traditional technique of chaining analog electronics. Tests have been performed using a pulser working at different frequencies as well as employing a 252Cf source in concert with an array of detectors
Characterization of a Large Area ZnS(Ag) Detector for Gross Alpha and Beta Activity Measurements in Tap Water Plants
No full textIn this work we present the characterization of a large area 200 mm ×200 mm EJ-444 scintillation detector to be used for monitoring gross alpha and beta activity in tap water plants. Specific tests were performed in order to determine the best setup to read-out the light from the detector side. The possibility to stack many detectors and get a compact device with total active area of the order of 1 m2 has been explored. Alpha/beta discrimination, efficiency and homogeneity tests were carried out with alpha and beta sources. Background from ambient radioactivity was measured as well. Alpha/beta real-time monitoring in drinking water is a goal of the EU project TAWARA_RTM
Study of the thermal neutron detector ZnS(Ag)/LiF response using digital pulse processing
No full textA compact neutron–gamma spectrometer
No full textA compact neutron/gamma detector has been developed using a liquid scintillator cell coupled to a Flat Panel PMT; performances have been compared with a second cell coupled to a traditional linearly-focused 12 dynodes PMT. Energy resolution and pulse shape discrimination (PSD) measured by using a fast digitizer are very similar for the two detectors with the time resolution of the Flat Panel PMT slightly worse. The new detector results to be weakly affected by the influence of a moderate magnetic field while the traditional PMT exhibits strong pulse reduction. The compact size and the low power consumption obtained by using the Flat Panel PMT are very useful in portable neutron/gamma spectrometers
Study of the thermal neutron detector ZnS(Ag)/LiF response using digital pulse processing
No full textThe neutron and gamma responses of a commercial 6Li loaded ZnS(Ag) detector
(EJ-420) have been studied using a moderated 252Cf source and a set of pure gamma ray sources
(137Cs and 241Am). Digital pulse processing was used to implement the pulse shape
discrimination technique in order to well-separate neutrons from gamma-induced events. It was
found that in case of a mixed neutron/gamma radiation field (252Cf) pulse-height discrimination
technique works quite good for the measurement of the neutron field, but if one desires to reach
a gamma-to-neutron sensitivity ratio lower than 0.7 % pulse shape discrimination technique
must be implemented. Also, the decay times of the scintillation components of ZnS(Ag)/6LiF
were determined by following the so called “peeling method”. The results were compared with
some reported values. In order to better understand the shape of the neutron-induced pulses
produced by the EJ-420 detector, a measurement with an EJ-440 detector of an alpha source
(210Po) was performed. The response of both detectors must be very similar because these are
based in ZnS(Ag) scintillator. It seems that for neutron detection with the EJ-420, the
scintillation produced by the tritium is most important than the one produced by the alpha
particle. Finally, the neutron efficiency and some experimental features of the EJ-420 detector
were determined and reproduced respectively by Monte Carlo simulations (GEANT4 9.6)
Detecting fast and thermal neutrons with a boron loaded liquid scintillator, EJ-339A
No full textA commercial boron-loaded liquid scintillator EJ-339 A was studied, using a 252Cf source with/without polyethylene moderator, to examine the possibility of discriminating slow-neutron induced events in 10B from fast-neutron events, resulting from proton recoils, and gamma-ray events. Despite the strong light quenching associated with neutron induced events in 10B, correct classification of these events is shown to be possible with the aid of digital signal processing
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