Moving sources detection system

Conference of 2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and Their Applications, ANIMMA 2013 ; Conference Code:102802International audienceTo monitor radioactivity passing through a pipe or in a given container such as a train or a truck, radiation detection systems are commonly employed. These detectors could be used in a network set along the source track to increase the overall detection efficiency. However detection methods are based on counting statistics analysis. The method usually implemented consists in trigging an alarm when an individual signal rises over a threshold initially estimated in regards to the natural background signal. The detection efficiency is then proportional to the number of detectors in use, due to the fact that each sensor is taken as a standalone sensor. A new approach is presented in this paper taking into account the temporal periodicity of the signals taken by all distributed sensors as a whole. This detection method is not based only on counting statistics but also on the temporal series analysis aspect. Therefore, a specific algorithm is then developed in our lab for this kind of applications and shows a significant improvement, especially in terms of detection efficiency and false alarms reduction. We also plan on extracting information from the source vector. This paper presents the theoretical approach and some preliminary results obtain in our laboratory

New monitoring system to detect a radioactive material in motion

Conference of 2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and Their Applications, ANIMMA 2013 ; Conference Code:102802International audienceIllegal radioactive material transportation detection, by terrorist for example, is problematic in urban public transportation. Academics and industrials systems include Radiation Portal Monitor (RPM) to detect radioactive matters transported in vehicles or carried by pedestrians. However, today's RPMs are not able to efficiently detect a radioactive material in movement. Due to count statistic and gamma background, false alarms may be triggered or at the contrary a radioactive material not detected. The statistical false alarm rate has to be as low as possible in order to limit useless intervention especially in urban mass transportation

An online change of activity in energy spectrum for detection on an early intervention robot

Conference of 4th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, ANIMMA 2015 ; Conference Code:121554International audienceWith the growth of industrial risks and the multiplication of CBRNe (Chemical Biological Radiological and explosive) attacks through toxic chemicals, biological or radiological threats, public services and military authorities face with increasingly critical situations, whose management is strongly conditioned by fast and reliable establishment of an informative diagnostic. Right after an attack, the five first minutes are crucial to define the various scenarii and the most dangerous for a human intervention. Therefore the use of robots is considered essential by all stakeholders of security. In this context, the SISPEO project (Système d'Intervention Sapeurs Pompiers Robotisé) aims to create/build/design a robust response through a robotic platform for early intervention services such as civil and military security in hostile environments. CEA LIST has proposed an adapted solution to detect and characterize nuclear and radiological risks online and in motion, using a miniature embedded CdZnTe (CZT) crystal Gamma-ray spectrometer. This paper presents experimental results for this miniature embedded CZT spectrometer and its associated mathematical method to detect and characterize radiological threats online and in motion

Hypothesis tests for the detection of constant speed radiation moving sources

Conference of 4th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, ANIMMA 2015 ; Conference Code:121554International audienceAs a complement to single and multichannel detection algorithms, inefficient under too low signal-to-noise ratios, temporal correlation algorithms have been introduced to detect radiological material in motion. Test hypothesis methods based on the mean and variance of the signals delivered by the different channels have shown significant gain in terms of a tradeoff between detection sensitivity and false alarm probability. This paper discloses the concept of a new hypothesis test for temporal product detection methods, taking advantage of the Poisson nature of the registered counting signals, and establishes a benchmark between this test and its empirical counterpart. The simulation study validates that in the two relevant configurations of a pedestrian source carrier under respectively high and low count rate radioactive backgrounds, the newly introduced hypothesis test ensures a significantly improved compromise between sensitivity and false alarm, while guaranteeing the stability of its optimization parameter regardless of signal-to-noise ratio variations between 2 to 0.8

A robust hypothesis test for the sensitive detection of constant speed radiation moving sources

International audienceRadiation Portal Monitors are deployed in linear networks to detect radiological material in motion. As a complement to single and multichannel detection algorithms, inefficient under too low signal-to-noise ratios, temporal correlation algorithms have been introduced. Test hypothesis methods based on empirically estimated mean and variance of the signals delivered by the different channels have shown significant gain in terms of a tradeoff between detection sensitivity and false alarm probability. This paper discloses the concept of a new hypothesis test for temporal correlation detection methods, taking advantage of the Poisson nature of the registered counting signals, and establishes a benchmark between this test and its empirical counterpart. The simulation study validates that in the four relevant configurations of a pedestrian source carrier under respectively high and low count rate radioactive backgrounds, and a vehicle source carrier under the same respectively high and low count rate radioactive backgrounds, the newly introduced hypothesis test ensures a significantly improved compromise between sensitivity and false alarm. It also guarantees that the optimal coverage factor for this compromise remains stable regardless of signal-to-noise ratio variations between 2 and 0.8, therefore allowing the final user to parametrize the test with the sole prior knowledge of background amplitude

Sodium Fast Reactor Power Monitoring and Clad Failure Detection using Adonis System

On sodium fast reactors, power is usually measured by heat balance on water to vapor heat exchangers which is correlated with the ex-core neutron flux measurements. The ex-core neutron power measurement is done by fission chambers (five on the French SFR Phnix reactor) with several activity ranges settled at the bottom of the primary vessel to cover the whole neutron flux range of more than 11 decades. This measurement instantly estimates the neutron power but induces some shift problems. The clad failure detection is done by gamma measurement on argon cover gas sampling and neutron measurement on primary sodium sample. This work deals with the use of gamma spectrometry for fourth generation SFR power monitoring and clad failure detection. Usually gamma spectrometers could not manage on-line application but recent improvements in this research field may improve it. The Adonis digital signal processing prototype gives a time function response and is able to do spectrometry measurement with metrological grade under high gamma flux impinging the HPGe detector, with also high and fast activity transient. Previous works on Pressurized Water Reactors (PWR) show that gamma emitter concentration in primary coolant is also directly correlated with reactor neutron power. On SFR, the use of short decay period gamma emitters as the 20F and 23Ne tagging agent will allow a very fast response system without thermal hydraulic distortion effects. The study is divided in two parts. First part deals with a simulation study based on physical calculations and MCNP simulations to predict sensor signal as a function of neutron power. The second part is an experimental test under preparation at the French SFR Phnix. Measuring activation and fission products contained in primary sodium, the adaptive Adonis system set on primary coolant sample could be an innovating neutron power monitoring and clad failure detection system for SFR

20F Power Measurement for Generation IV Sodium Fast Reactors

International audienceThe Phénix nuclear power plant has been a French Sodium Fast Reactor (SFR) prototype producing electrical power between 1973 and 2010. The power was monitored using ex-core neutron measurements. This kind of measurement instantly estimates the power but needs to be often calibrated with the heat balance thermodynamic measurement. Large safety and security margins have then been set not to derive above the nominal operating point. It is important for future SFR to reduce this margin and working closer to the nominal operating point. This work deals with the use of delayed gamma to measure the power. The main activation product contained in the primary sodium coolant is the 24Na which is not convenient for neutron flux measurement due to its long decay period. The experimental study done at the Phénix reactor shows that the use of 20F as power tagging agent gives a fast and accurate power measurement closed to the thermal balance measurement thanks to its high energy photon emission (1.634 MeV) and its short decay period (11 s)

Delayed gamma power measurement for sodium-cooled fast reactors

Previous works on pressurized water reactors show that the nitrogen 16 activation product can be used to measure thermal power. Power monitoring using a more stable indicator than ex-core neutron measurements is required for operational sodium-cooled fast reactors, in order to improve their economic efficiency at the nominal operating point. The fluorine 20 and neon 23 produced by (n,α) and (n,p) capture in the sodium coolant have this type of convenient characteristic, suitable for power measurements with low build-up effects and a potentially limited temperature, flow rate, burn-up and breeding dependence. This method was tested for the first time during the final tests program of the French Phénix sodium-cooled fast reactor at CEA Marcoule, using the ADONIS gamma pulse analyzer. Despite a non-optimal experimental configuration for this application, the delayed gamma power measurement was pre-validated, and found to provide promising results