Pest management and biodiversity in organic fruit production: the case of apple orchards

Numerous pesticide applications are required for orchard protection, regardless of the guidelines. Organic fruit production (OFP) mainly relies on the use of mineral fungicides and microbiological or naturally-occurring insecticides. The environmental impact of this type of production does not significantly differ from that of conventional production when assessed in terms of synthetic indicators. However, the abundance of earthworms, as well as the abundance and specific richness of arthropod pests and beneficials in the orchards and surrounding hedges, is greater in OFP than in conventional orchards. Generalist predators are usually less affected by OFP compounds than by the chemical pesticides applied in conventional orchards. OFP also benefits avian communities, and above all, insectivorous birds, for which organic orchards offer a suitable habitat similar to that of undisturbed natural areas. In addition to this general trend, discrepancies may be observed in the protection responses of different insect groups. The abundance of hymenopteran parasitoids is the lowest in organic orchards in which outbreaks of phytophagous mites are also recorded in relation to the intensive use of sulphur for scab protection. Biological insecticides often act in ways that are similar to those of chemical ones, and the restricted choice of available compounds is likely to induce resistance selection in insect pests. Although maintaining biodiversity is not a direct result of the implementation of OFP guidelines, it seems to be widely considered as an option by organic growers, both alone and as a complementary tool for pest regulation

Gamma-ray spectroscopy measurements and simulations for uranium mining

AREVA Mines and the Nuclear Measurement Laboratory of CEA Cadarache are collaborating to improve the sensitivity and precision of uranium concentration evaluation by means of gamma measurements. This paper reports gamma-ray spectra, recorded with a high-purity coaxial germanium detector, on standard cement blocks with increasing uranium content, and the corresponding MCNP simulations. The detailed MCNP model of the detector and experimental setup has been validated by calculation vs. experiment comparisons. An optimization of the detector MCNP model is presented in this paper, as well as a comparison of different nuclear data libraries to explain missing or exceeding peaks in the simulation. Energy shifts observed between the fluorescence X-rays produced by MCNP and atomic data are also investigated. The qualified numerical model will be used in further studies to develop new gamma spectroscopy approaches aiming at reducing acquisition times, especially for ore samples with low uranium content

Electronics and ³He Counter Acquisition Tests During the Pulses of a D-T Neutron Generator

International audienceNuclear logging industry uses Active Neutron Interrogation devices for geological prospection and exploitation. Modern neutron logging tools uses a pulsed neutron generator emitting fast neutrons (2.5 or 14.1 MeV) with an average emission in the 108s-1range. Some measurement techniques rely on nonfully thermalized neutrons, called epithermal neutrons, which are less sensitive to neutron absorbers than thermal neutrons. The signal due to generator neutrons backscattered towards helium 3 proportional counter is used to assess hydrogen porosity. It decays within hundreds of microseconds. Historically, epithermal neutron measurements, with a cadmium layer around the detector, suffered of insufficient counting statistics. To parry this drawback, our goal is to perform the measurement during the neutron generator burst. Therefore, the detector and acquisition chain must be able to handle a high flux of neutrons. This work investigates the behavior of 3He counters with different gas additives, adapted either to charge or to current amplifiers, located close to a D-T neutron generator, with the same total detection efficiency we have in a logging tool. We tested instantaneous neutron emissions between 107and 2.5∙109s-1during generator pulses with a duration ranging from 40 to 800 µs. It appears that the throughput of the acquisition chain does not only depend on the generator instantaneous emission rate, but also on burst duration. Unexpectedly the maximum output count rate 4.4∙106s-1is thus reached with short generator pulses of 40 µs length and a very high instantaneous neutron emission 8.4∙109s-1, using a 30NH15CS 3He counter adapted to G-ADSF10 current amplifier

Modelling codling moth damage as a function of adult monitoring and crop protection: A survival generalized linear mixed model approach with time varying covariates

The codling moth (Cydia pomonella) is responsible for most insecticide treatments in pear and apple orchards. In a context of reduction in pesticide use, we aim at better understanding factors that affect codling moth damage intensity. We modelled the link between the proportion of damaged fruits and both constant covariables (type of orchard: pear or apple, organic or not, with or without mating disruption) and time-varying covariables (weekly counts of adults and number of insecticide treatments). Observations were collected in 40 orchards in south-eastern France. We found that damage intensity increased with the number of adults trapped. An analysis of the random orchard effect indicated a certain temporal stability in the risk probability of orchards and a lower risk probability in orchards surrounded by numerous pome fruit orchards and windbreak hedgerows

Development of a neutron probe to perform a combined measurement of uranium concentration and hydrogen porosity for mining applications

International audienceThis work reports the development of a new neutron probe for mining prospection and exploitation. It allows a combined measurement of hydrogen porosity, based on the detection of neutrons backscattered by the geological formation, and of uranium concentration based on induced-fission prompt neutrons, with the Differential Die-away Technique. The probe includes a pulsed neutron generator and a single neutron counter embedded in a polyethylene block wrapped with cadmium, saving the place for a gamma-ray detector compared to usual porosity probes with two 3He counters. We first report design and feasibility studies using MCNP 6.2 simulations, showing the significant effect of hydrogen porosity on the uranium signal and the need for a combined interpretation. Then, we report laboratory experiments that validate the simulation methods of both the porosity and uranium useful signals, but also the active background due to 17O activation. Taking into account neutron absorbers in the sand of our testing system, like boron, lithium and gadolinium measured by ICP-MS, the simulated and experimental signals of prompt fission neutrons agree within +20 %. The relative effect of water, introduced in the central hole of our experimental system, is about 30 % on the backscattered neutron signal, in both simulation and experiment. Finally, the spatial sensitivity of the tool, which is maximal in front of the detector and extends to approximately 20 cm (FWHM) in the vertical axis, is well reproduced with MCNP

Improving gross count gamma-ray logging in uranium mining with the NGRS probe

AREVA Mines and the Nuclear Measurement Laboratory of CEA Cadarache are collaborating to improve the sensitivity and precision of uranium concentration measurement by means of gamma ray logging. The determination of uranium concentration in boreholes is performed with the Natural Gamma Ray Sonde (NGRS) based on a NaI(Tl) scintillation detector. The total gamma count rate is converted into uranium concentration using a calibration coefficient measured in concrete blocks with known uranium concentration in the AREVA Mines calibration facility located in Bessines, France. Until now, to take into account gamma attenuation in a variety of boreholes diameters, tubing materials, diameters and thicknesses, filling fluid densities and compositions, a semi-empirical formula was used to correct the calibration coefficient measured in Bessines facility. In this work, we propose to use Monte Carlo simulations to improve gamma attenuation corrections. To this purpose, the NGRS probe and the calibration measurements in the standard concrete blocks have been modeled with MCNP computer code. The calibration coefficient determined by simulation, 5.3 s-1.ppmU-1 ± 10%, is in good agreement with the one measured in Bessines, 5.2 s-1.ppmU-1. Based on the validated MCNP model, several parametric studies have been performed. For instance, the rock density and chemical composition proved to have a limited impact on the calibration coefficient. However, gamma self-absorption in uranium leads to a nonlinear relationship between count rate and uranium concentration beyond approximately 1% of uranium weight fraction, the underestimation of the uranium content reaching more than a factor 2.5 for a 50 % uranium weight fraction. Next steps will concern parametric studies with different tubing materials, diameters and thicknesses, as well as different borehole filling fluids representative of real measurement conditions

Development of a neutron probe to perform a combined measurement of uranium concentration and hydrogen porosity for mining applications

International audienceThis work reports the development of a new neutron probe for mining prospection and exploitation. It allows a combined measurement of hydrogen porosity, based on the detection of neutrons backscattered by the geological formation, and of uranium concentration based on induced-fission prompt neutrons, with the Differential Die-away Technique. The probe includes a pulsed neutron generator and a single neutron counter embedded in a polyethylene block wrapped with cadmium, saving the place for a gamma-ray detector compared to usual porosity probes with two 3He counters. We first report design and feasibility studies using MCNP 6.2 simulations, showing the significant effect of hydrogen porosity on the uranium signal and the need for a combined interpretation. Then, we report laboratory experiments that validate the simulation methods of both the porosity and uranium useful signals, but also the active background due to 17O activation. Taking into account neutron absorbers in the sand of our testing system, like boron, lithium and gadolinium measured by ICP-MS, the simulated and experimental signals of prompt fission neutrons agree within +20 %. The relative effect of water, introduced in the central hole of our experimental system, is about 30 % on the backscattered neutron signal, in both simulation and experiment. Finally, the spatial sensitivity of the tool, which is maximal in front of the detector and extends to approximately 20 cm (FWHM) in the vertical axis, is well reproduced with MCNP

Improving gross count gamma-ray logging in uranium mining with the NGRS probe

AREVA Mines and the Nuclear Measurement Laboratory of CEA Cadarache are collaborating to improve the sensitivity and precision of uranium concentration measurement by means of gamma ray logging. The determination of uranium concentration in boreholes is performed with the Natural Gamma Ray Sonde (NGRS) based on a NaI(Tl) scintillation detector. The total gamma count rate is converted into uranium concentration using a calibration coefficient measured in concrete blocks with known uranium concentration in the AREVA Mines calibration facility located in Bessines, France. Until now, to take into account gamma attenuation in a variety of boreholes diameters, tubing materials, diameters and thicknesses, filling fluid densities and compositions, a semi-empirical formula was used to correct the calibration coefficient measured in Bessines facility. In this work, we propose to use Monte Carlo simulations to improve gamma attenuation corrections. To this purpose, the NGRS probe and the calibration measurements in the standard concrete blocks have been modeled with MCNP computer code. The calibration coefficient determined by simulation, 5.3 s-1.ppmU-1 ± 10%, is in good agreement with the one measured in Bessines, 5.2 s-1.ppmU-1. Based on the validated MCNP model, several parametric studies have been performed. For instance, the rock density and chemical composition proved to have a limited impact on the calibration coefficient. However, gamma self-absorption in uranium leads to a nonlinear relationship between count rate and uranium concentration beyond approximately 1% of uranium weight fraction, the underestimation of the uranium content reaching more than a factor 2.5 for a 50 % uranium weight fraction. Next steps will concern parametric studies with different tubing materials, diameters and thicknesses, as well as different borehole filling fluids representative of real measurement conditions

Improving gross count gamma-ray logging in uranium mining with the NGRS probe

International audienceAREVA Mines and the Nuclear Measurement Laboratory of CEA Cadarache are collaborating to improve the sensitivity and precision of uranium concentration measurement by means of gamma ray logging. The determination of uranium concentration in boreholes is performed with the Natural Gamma Ray Sonde (NGRS) based on a NaI(Tl) scintillation detector. The total gamma count rate is converted into uranium concentration using a calibration coefficient measured in concrete blocks with known uranium concentration in the AREVA Mines calibration facility located in Bessines, France. Until now, to take into account gamma attenuation in a variety of boreholes diameters, tubing materials, diameters and thicknesses, filling fluid densities and compositions, a semi-empirical formula was used to correct the calibration coefficient measured in Bessines facility. In this work, we propose to use Monte Carlo simulations to improve gamma attenuation corrections. To this purpose, the NGRS probe and the calibration measurements in the standard concrete blocks have been modeled with MCNP computer code. The calibration coefficient determined by simulation, 5.3 s-1.ppmU-1 ± 10%, is in good agreement with the one measured in Bessines, 5.2 s-1.ppmU-1. Based on the validated MCNP model, several parametric studies have been performed. For instance, the rock density and chemical composition proved to have a limited impact on the calibration coefficient. However, gamma self-absorption in uranium leads to a nonlinear relationship between count rate and uranium concentration beyond approximately 1% of uranium weight fraction, the underestimation of the uranium content reaching more than a factor 2.5 for a 50 % uranium weight fraction. Next steps will concern parametric studies with different tubing materials, diameters and thicknesses, as well as different borehole filling fluids representative of real measurement conditions

Gamma-ray spectroscopy measurements and simulations for uranium mining

AREVA Mines and the Nuclear Measurement Laboratory of CEA Cadarache are collaborating to improve the sensitivity and precision of uranium concentration evaluation by means of gamma measurements. This paper reports gamma-ray spectra, recorded with a high-purity coaxial germanium detector, on standard cement blocks with increasing uranium content, and the corresponding MCNP simulations. The detailed MCNP model of the detector and experimental setup has been validated by calculation vs. experiment comparisons. An optimization of the detector MCNP model is presented in this paper, as well as a comparison of different nuclear data libraries to explain missing or exceeding peaks in the simulation. Energy shifts observed between the fluorescence X-rays produced by MCNP and atomic data are also investigated. The qualified numerical model will be used in further studies to develop new gamma spectroscopy approaches aiming at reducing acquisition times, especially for ore samples with low uranium content