A New Concept to Secure Food Safety Standards against Fusarium Species and Aspergillus Flavus and Their Toxins in Maize

Commercial maize hybrids are exposed to different degrees of ear infection by toxigenic fungal species and toxin contamination. Their resistance to different fungi and toxin relationships are largely unknown. Without this knowledge, screening and breeding are not possible for these pathogens. Seven- to tenfold differences were found in resistance to Fusarium spp., and there was a five-fold difference in ear coverage (%) in response to A. flavus. Three hybrids of the twenty entries had lower infection severity compared with the general means for toxigenic species. Three were highly susceptible to each, and 14 hybrids reacted differently to the different fungi. Differences were also observed in the toxin content. Again, three hybrids had lower toxin content in response to all toxigenic species, one had higher values for all, and 16 had variable resistance levels. Correlations between infection severity and deoxynivalenol (DON) content were 0.95 and 0.82 (p = 0.001) for F. graminearum and F. culmorum, respectively. For fumonisin and F. verticillioides ear rot, the Pearson correlation coefficient (r) was 0.45 (p = 0.05). Two independent isolates with different aggressiveness were used, and their mean X values better described the resistance levels. This increased the reliability of the data. With the introduction of this methodological concept (testing the resistance levels separately for different fungi and with two isolates independently), highly significant resistance differences were found. The resistance to different fungal species correlated only in certain cases; thus, each should be tested separately. This is very useful in registration tests and post-registration screening and breeding. This would allow a rapid increase in food and feed safety

Detection of fissile material using cold neutron interrogation combined with neutron coincidence counting

A variety of neutron interrogation techniques exists for the identification and characterization of fissile materials. Typically the sample is irradiated continuously or in pulses, and the neutron or gamma response is used to for the characterization. Active neutron coincidence counting is one of these techniques, based on the detection of correlated prompt neutrons from induced fission in 235U, in order to quantify uranium. Typically AmLi neutron sources are used for the interrogation so far. In this study we used for the first time a guided cold neutron beam for interrogation, which is a far more intense source of uncorrelated neutrons. A pilot neutron coincidence setup was installed at a neutron beam of the Budapest Neutron Centre, and samples of small volumes and various uranium contents were measured. It was proven that the detection of fission events (Doubles) is feasible even for micrograms of 235U and the detector response is proportional to the fissile content of the sample.JRC.E.8-Nuclear securit

Absolute determination of small samples of Pu and Am by calorimetry

An extensive measurement campaign has been carried in order to recalibrate and assess the performance of the small sample calorimeter (SSCAL) that was recently upgraded. The measurements have been performed in the Performance Laboratory of the Joint Research Centre’s (JRC) Nuclear Security Unit in Ispra (Italy) using calibrated electric heat sources and standard reference nuclear materials. The SSCAL is a heat flow calorimeter which works by measuring the voltage generated by a heat-emitting sample across a thermal gap based on a thermopile cup technology. Results of calorimetry measurements carried out, both inside and outside a well-controlled environment of a climatic chamber, on reference PuGa samples and well-characterised 241Am samples are presented and discussed. The latter samples were produced at the JRC-ITU to be used by the JRC-IRMM for various cross-section measurements (total, neutron capture and 241Am(n,2n) 240Am).JRC.E.8-Nuclear securit

Calibration, characterisation and Monte Carlo modelling of a fast-UNCL

This paper describes the calibration, characterization and Monte Carlo modeling of a new IAEA Uranium Neutron Collar for LWR fuel (UNCL), which can be operated in both Passive and Active mode and employs up to 44 3He tubes at 10 atm pressure (in passive mode). Thus it can be operated in fast mode due its higher efficiency than the standard UNCL. Furthermore, it has an adjustable internal cavity which allows the measurement of varying sizes of fuel assemblies such as WWER-1000, WWER440, PWR, BWR. It is intended to be used (in active and fast modes) by the inspectorate for the determination of the 235U content in fresh fuel assemblies especially in cases where high concentrations of burnable poisons cause problems with accurate assays. A campaign of measurements has been carried out at the JRC-Ispra Performance Laboratories (PERLA) using various radionuclide neutron sources (252Cf, 241AmLi and PuGa) and our BWR and PWR reference assemblies, in order to calibrate and characterise the counter as well as assess its performance and determine its optimum operational parameters. Furthermore, the fast-UNCL has been extensively modelled at JRC using the Monte Carlo code, MCNP-PTA, which simulates both the neutron transport and the coincidence electronics. The model has been well validated using our measurements which agreed well with calculations. The WWER1000 fuel assembly for which there are no representative reference materials for an adequate calibration of the counter, has also been modelled and the response of the UNCL to these fuel assemblies has been simulated. Subsequently numerical calibrations curves have been obtained for the above fuel assemblies in various modes (fast and thermal), the sensitivity of the counter to fuel rods substitution as well as other important aspects and the parameters of the fast-UNCL performance have been investigated and assessed.JRC.E.8-Nuclear securit

Calibration and Monte Carlo Modelling of a fast-UNCL for the IAEA

A campaign of measurements has been carried in the JRC PERLA laboratories in order to calibrate and characterise a fast-UNCL counter recently acquired by the IAEA. Various radionuclide neutron sources (252Cf, 241AmLi), BWR and PWR reference assemblies were used. Furthermore, the counter has been extensively modelled using the Monte Carlo code, MCNP-PTA, which simulates both the neutron transport and the coincidence electronics. The models have been validated using measurements, the results of which agree generally very well with the simulations. The WWER1000 fuel magazine for which there are no representative reference materials for an adequate classical calibration of the counter, has also been modelled using MCNP-PTA. The response of the fast-UNCL to these fuel assemblies has been simulated and numerical calibrations curves were obtained for the above fuel assemblies in various modes (fast and thermal). They are compared to a standard UNCL II from LANL. Preliminary results are given as further work including, sensitivity analysis, model validation for WWER10000 fuel, efficiency optimization for BWR etc. is in progress.JRC.E.8-Nuclear securit

Using FRAM to determine enrichment of shielded uranium by portable electrically cooled HPGe detectors

The capability of the FRAM software to accurately determine the enrichment of shielded uranium by portable electrically cooled HPGe detectors was studied. This can have applications in the future, e.g., for the verification of aged uranium-bearing products, scrap, and waste materials, especially during short notice random or unannounced inspections, when detector cooling with liquid nitrogen is not feasible. More than 7000 high-resolution gamma spectra of certified reference materials were taken by the ORTEC "Detective" detector under well-defined measurement conditions. Up to 16 mm of steel was used for shielding. The 235U enrichment of the reference materials varied from 0.31% to 4.46%. The settings of an existing FRAM parameter set were optimized and all the collected spectra were analysed using the default and the optimized parameter sets. The results obtained with these parameter sets are compared in this paper.JRC.G.II.6-Nuclear Safeguards and Forensic

A methodfortheestimationoffissilemassbymeasuringthenumber of neutronsignalswithinaspecifictimeinterval

The purpose of this paper is to present a new method for the estimation of fissile mass by a measurement of the number of neutron signals in time intervals. The method uses the stochastic transport equation to express the first three central moments (mean, variance and skewness) of the number of neutron detections in a time interval in terms of the fissile mass, the (alpha,n) rate and the multiplicity factor. Solving the three equations allows estimation of the fissile mass. The first to use the stochastic transport equation to characterize nuclear systems was Feynmann in his work in 1946. The two main advantages of the proposed method, compared to the multiplicity method, are the simplicity of implementation and the higher eciency thus requires relatively shorter measurement time. The method was implemented for severalfissile mass measurements, which were conducted by the Nuclear Security Unit of the JRC in Italy and by the Institute of Isotopes, Hungary.JRC.E.8-Nuclear securit

Characterization of PuBe nuetron sources by calorimetry and neutron assay

In order to support and refine in-field NDA methods developed for the assay of PuBe sources the heat power of a set of such sources is measured by a heat-flow calorimeter. The Pu isotopic composition of the sources was determined by gamma spectrometry. By combining these two measurements the Pu mass of the sources was determined. In addition, the actual neutron output of the sources was also measured using a calibrated neutron coincidence counter. The measurement campaign resulted in a set of well-characterized PuBe sources, which can be used as secondary standard calibration sources.JRC.E.8-Nuclear securit

Construction of a NDA-Safeguards Training Facility at the ITU Karlsruhe

In this paper the newly constructed NDA-Training facility at the Karlsruhe site of the Institute for Transuranium Elements (ITU) is presented. Training courses for nuclear Safeguards inspectors from EURATOM and IAEA will be provided. They comprise NDA-techniques for safeguards measurements involving fissile material, e.g. active and passive neutron measurements as well as techniques based on gamma measurements. The laboratory was built as part of the European Nuclear Security Training Centre project (EUSECTRA) which aims at providing security training to prevent the misuse of nuclear material. Nuclear safeguards trainings take place in a specifically dedicated separate lab of this new EUSECTRA facility, where exclusively encapsulated radioactive material is handled. The training courses are embedded in the European Nuclear Safety and Security School (EN3S) of the European Commission, Joint Research Centre and complement NDA safeguards training held at the Ispra site of ITU.JRC.E.7-Nuclear Safeguards and Forensic