Search

The accurate measurement of beta emitters is of utmost importance in various fields, including environmental monitoring, radiation protection and dismantling and decommissioning (D&D) operations. Nondestructive measurement techniques are crucial as they enable assessments of radioactivity without causing further harm or releasing additional hazardous materials. Due to the limited range of beta particles in matter, their characterization requires measurements in contact with the source term. In this paper, we present a study on the performance evaluation of a plastic scintillation detector designed for in-situ beta spectrometry measurements. The MCNP6.2 numerical model of the detector is detailed in the measurement configuration with beta, gamma and internal conversion electrons emitting sources. The calibration process and Gaussian Energy Broadening (GEB) parameters evaluation are discussed. Comparisons between the MCNP6.2 simulations and experimental measurements are exposed, both for gamma and beta spectra. While the gamma-ray detector response shows good agreement, greater discrepancies are observed in the beta ray response. To shed light on these discrepancies, a sensitivity analysis considering various sources of uncertainties is planned for future work.

For more than ten years the CEA has been using [gamma] imaging systems for radiological characterization purposes during decommissioning operations. This technology is very effective for detecting high-energy [gamma] emitters, but less so for characterizing actinides, which are mainly [alpha] emitters. In order to provide a full range of decommissioning tools, the [gamma]-cameras were supplemented by another imaging system capable of generating images directly from [alpha] emissions. This paper describes the initial laboratory and field test results obtained with a prototype camera capable of displaying [alpha] radioactivity. The system is based on the detection of ultraviolet radiation emitted by nitrogen when irradiated by alpha particles. The [alpha] contamination is localized by superimposing it on a visible-light image. All measurements must be carried out in complete darkness. Laboratory tests showed that the system is capable of detecting point sources and extended sources at levels as low as 430 Bq x [cm.sup.-2]. Profile measurements of point sources revealed a scintillation bubble with dimensions corresponding to the range of [alpha] particles in air. The device is also capable of detecting the phenomenon through translucent materials such as glove box panels. The camera has been implemented for in situ examination of various fuel cycle facilities, and under these conditions has revealed [alpha] contamination without any breach of containment through several millimeters of plexiglas. Index Terms--Alpha-particle detectors, back illuminated charge coupled devices, radioluminescence, remote imaging, ultraviolet emission.

The aim of this study was to assess the effect of vascular occlusion on radio-frequency (RF) lesion size and on potential associated biliary and portal lesions. Radio-frequency lesions using a 1-cm exposed-tip cooled electrode were created in pig liver. Liver perfusion was modified by arterial embolization (n=2), left portal clamping (n=2), and both (n=2). Two pigs were used as controls. Two weeks after, control portography was performed, animals were killed, and ex-vivo cholangiography was carried out. Pathological studies evaluated the lesion surface and associated portal and biliary damages. A mathematical regression model showed that portal occlusion increased by 43 mm2 (+40%) the surface of RF lesions, arterial occlusion by 135 mm2 (+126%), and associated occlusion by 466 mm2 (+435%). Biliary stenoses were found in 4 cases (two arterial occlusions, one portal occlusion, and one associated occlusion). One case of partial portal vein thrombosis was found in one case of portal occlusion and resolved at 2 weeks. Ischemic damages adjacent to RF lesions were found in cases of combined occlusions. The reduction of liver perfusion increases significantly the size of RF lesions but is associated with a risk of biliary, portal, or parenchymal complications. [ABSTRACT FROM AUTHOR]

Background: Genital ulcer disease (GUD) is documented as a significant risk factor for HIV acquisition. Its prompt recognition and effective treatment are important components of HIV control in sub-Saharan Africa.Goals: To determine the rate and risk factors for GUD, and to describe sexual and treatment-seeking behavior.Study Design: A longitudinal follow-up study of 525 individuals, both those infected with HIV and those uninfected, was conducted in a population-based, clinical cohort over 9 years.Results: The rate of GUD in this population was 16/100 person years, and 30% of the participants reported an episode during the follow-up period. The rates were almost four times higher in participants infected with HIV than in those who were HIV-negative. Half of the participants with a regular sexual partner reported engaging in sex while symptomatic, and only 16% informed their partner. Treatment was sought for only 12% of the genital ulcer disease episodes, despite open access to doctors at a free clinic. A self-diagnosis of genital herpes did not affect treatment-seeking or sexual behavior.Conclusions: Genital ulcer disease is very common in this rural population, especially among those infected with HIV. Few seek treatment, and many continue sexual activity despite symptoms without informing their partners. The implications of these findings for HIV control are a cause for concern. [ABSTRACT FROM AUTHOR]