Use of lead for the reduction of background gamma rays in underground experiments

In order to determine the effectiveness of lead for the reduction of gamma-rays at a site 1230 m underground, a sodium iodide crystal detector has been used to measure the gamma-ray spectrum up to 9 MeV emanating from a shield of lead that totally surrounded the detector. Below 3 MeV, the contribution to the gamma-ray spectrum was from long-lived radioactive trace elements in the shield itself. From these measurements it was possible to estimate the concentration of <sup>238</sup>U and <sup>232</sup>Th in the lead to be 1.9 × 10<sup>−7</sup> and 3.4 × 10<sup>−8</sup> gg<sup>−1</sup>, respectively, more than one order of magnitude less than what is observed in the environment. From 4 to 6 MeV the activity observed had to be internal to the detection system. The most probable source of these events is due to a combination of alpha and beta decays from daughter products of <sup>232</sup>Th. Above 6 MeV, the activity observed is predominantly due to (n,γ) interactions in the NaI crystal, in the lead shield, in the stainless-steel housing of the detector and in the materials that make up the photomultiplier tube, with a negligible contribution from <sup>238</sup>U fissions. In consequence, for most applications, a solitary shield of lead would not be sufficient to achieve a background-free environment, so it would be recommended that an additional neutron shield external to the lead would be needed to reduce the higher-energy gamma rays that originate from these (n,γ) reactions

Influence of inflammation on the efficacy of antibiotic treatment of experimental pyelonephritis.

An acute exudative Escherichia coli pyelonephritis rat model was used to study the influence of progressive pyelonephritis on the efficacy of antibiotic treatment. In this model, transient ureteral obstruction after E. coli bladder inoculation induces early bacterial multiplication in the kidney parenchyma, and the bacterial counts peak by 48 h. The inflammatory response (assessed by the increase in kidney weight) is somewhat delayed, starting 36 h after inoculation and peaking by 72 h. Groups of rats received 4 doses over 48 h of saline, ceftriaxone (100 mg/kg), or ceftriaxone (100 mg/kg) plus gentamicin (4 mg/kg). These treatments were initiated 24, 36, 48, or 72 h after bladder inoculation. Antibiotic treatment started at 24 h was significantly more effective in reducing bacterial counts in the kidney parenchyma than at any later therapy onset. Only when started 24 h after inoculation was the synergistic combination of ceftriaxone plus gentamicin more effective in reducing bacterial counts than ceftriaxone alone. Ceftriaxone and ceftriaxone plus gentamicin regimens started at 24 h reduced significantly (by 42 and 55%, respectively) the incidence of acute exudative pyelonephritis when compared with the incidence in saline-treated controls. Early therapy onset (24 h) strikingly reduced the development of the inflammatory response. This reduction was less marked when antibiotic therapy was started at 36 h and no longer apparent when therapy onset was delayed up to 48 or 72 h. In conclusion, the efficacy of antibiotics in eradicating bacteria from the kidney parenchyma and in preventing acute exudative pyelonephritis was markedly hampered by the development of pyelonephritis

Calculation of the core parameters measured during the commissioning of the OPAL Reactor.

The OPAL Research reactor is a multi-purpose open-pool type reactor. The nominal fission power of the reactor is 20 MW. It was commissioned during the second half of the year 2006. The reactor has several nuclear safety related design criteria that have to be experimentally verified during Stage B of the commissioning of the reactor. The present work presents the measurements carried out during the Stage B of the commissioning of the OPAL reactor, and the numerical verification of the calculated values using the design calculation methodology against these measured values. A brief description of the OPAL reactor, its commissioning plan, its nuclear safety related design criteria and the calculation and the experimental methodology are presented. The measured values and a comparison with the calculated is also given.Westinghouse Electric Company; FirstEnergy Nuclear Operation Company; Bettis Atomic Power Laboratory; Exelon Corporation; Pebble Bed Modular Reactor (Pty) Ltd; Idaho National Laborator

Etude de la variation interlaboratoire du test de dépistage prénatal des défauts de fermeture du tube neural

La détection précoce des défauts de fermeture du tube neural peut s'effectuer par le dosage de l'alphafoetoproteine (AFP) dans le sang maternel. 16'685 grossesses ont été examinées en Suisse. Trois méthodes de détermination du domaine d'anormalité sont étudiées. La première, proposée dans d'autres études semblables, utilise un multiple de la médiane. Les deux autres emploient des estimateurs robustes de location et d'échelle. Leur comparaison montre l'intérêt d'utiliser les méthodes robustes pour la réduction de la variabilité interlaboratoire. Early detection of neural-tude defects is possible by determining Alpha-fetoprotein (AFP) in maternal serum. 16'685 pregnant women were observed. Three methods for the determination of the "normal" range are compared. The first one, already used in similar studies, makes use of a constant multiple of the median. The other two ones make use of robust estimates of location and scale. Their comparison shows the interest of the robust methods to reduce the interlaboratory variability. Die Früherkennung von Neuralleistendefekten kann mit Hilfe der Bestimmung des Alphafoetoproteins (AFP) im mütterlichen Blut erfolgen. Diese Trennschärfe hängt von den Variabilitätsgrenzen der Normalweite ab. 16'685 Schwangerschaften wurden untersucht. Zur Bestimmung des Normalbereiches wurden drei Methoden verglichen. Die erste, angewandt in ähnlichen ausländischen Studien, beruht auf einem Konstanten Vielfachen des Medians. Die beiden anderen beruhen auf robusten Schätzungen von Lokation und Skala. Der Vergleich der Methoden zeigt, dass die robusten Verfahren besser geeignet sind, um die Variabilität zwischen den einzelnen Labors zu reduzieren

Analysis of dynamic reactivity by Monte Carlo methods: The impact of nuclear data

International audienceWe compute the dynamic reactivity of several reactor configurations by resorting to Monte Carlo simulation. The adjoint-weighted kinetics parameters are first determined by the Iterated Fission Probability (IFP) method, together with precursor decay constants, and the reactivity is then estimated by the inhour equation. When literature values are available for the reactivity as a function of the asymptotic reactor period, comparison with the Monte Carlo simulation findings allows validating the IFP algorithm and at the same time probing the accuracy of the nuclear data libraries used in numerical simulations. For our calculations we resort to the Tripoli-4 Monte Carlo code, developed at CEA, where IFP methods have been recently implemented. We perform a detailed analysis of the IPEN/MB-01 core, the SPERT III E-core, and the SPERT IV D-12/25 core, for which benchmark-quality reactor specifications have been published. We single out some systematic discrepancies between computed and measured core reactivity that might mirror possible inconsistencies in nuclear data libraries

Progress Report of the Sydney Underground Laboratory, SUNLAB

A 27 tonne tank of chilled and purified water has been operating in a preliminary fashion as an underground Cherenkov detector during 1989. The aim of this operation is to assess the feasibility of such a design for ultimate deployment as a solar neutrino detector. Into this tank are lowered various photon collection units; and results obtained with the arrangement are presented. Progress to date and future plans for this underground laboratory are discussed

On line neutron flux mapping in fuel coolant channels of a research reactor

Conference of 2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and Their Applications, ANIMMA 2013 ; Conference Code:102802International audienceThis work deals with the on-line neutron flux mapping of the OPAL research reactor. A specific irradiation device has been set up to investigate fuel coolant channels using subminiature fission chambers to get thermal neutron flux profiles. Experimental results are compared to first neutronic calculations and show good agreement (C/E ∼0.97)

Refereed Conference Publications

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