| 1. |
- Berggren, Christian, 1950-, et al.
(författare)
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Inför EU-tull på koldioxid
- 2007
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Ingår i: Svenska dagbladet. - 1101-2412. ; 2007-04-10:Brännpunkt
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
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| 2. |
- Jacobsson, Staffan, 1951, et al.
(författare)
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Conceptual confusion - an analysis of the meaning of concepts in technological innovation systems and sociological functionalism
- 2014
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Ingår i: Technology Analysis and Strategic Management. - : Informa UK Limited. - 0953-7325 .- 1465-3990. ; 26:7, s. 811-823
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this paper is to illustrate how conceptual confusion may be a significant obstacle to cross-disciplinary dialogue. We focus on the relationship between the framework of technological innovation systems (TIS) and sociological functionalism (SF). The paper argues that while there are similarities between the two schools of thought, in particular in the use of the terms 'structure' and 'function', these are more linguistic than substantive. We demonstrate this by assessing the validity of the spillover to TIS of four main points of critique raised against SF. We conclude by stating some lessons for improving cross-disciplinary communication.
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| 3. |
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| 4. |
- Jacobsson, Staffan, 1951, et al.
(författare)
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Inför EU-tull på koldioxid
- 2007
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Ingår i: Svenska Dagbladet Brännpunkt. ; 10.4.2007
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
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| 6. |
- Wolniewicz, Peter, 1978-, et al.
(författare)
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Reactivity changes in lead-cooled fast reactors due to bubbles in the coolant
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The formation of bubbles in the coolant of a Lead-Cooled Fast Reactor (LFR) may originate from a leaking heat-exchanger and is a potential safety hazard. Small bubbles can travel with the coolant without escaping to the cover gas, causing an increasing effective voiding of the coolant in a homogeneous manner. If the small bubbles coalesce into a larger bubble located at a stagnation zone, the reactor core may eventually be exposed to a transient bubble travelling axially through the core with a resulting change in the reactivity of the system. This study is focused on the reactivity changes caused by bubbles of various sizes and for different vertical positions as the bubble rises through the core. Three different sizes of LFR’s; 50 MWth, 300 MWth and 1200 MWth,respectively were user for the study. The 300 MWth reactor design is based on the Advanced LFR European Demonstrator (ALFRED) and the two other reactors are scaled up and scaled down versions of it and these were simulated in order study the sensitivity to void as a function of reactor size. We show that LFR’s may have a positive reactivity response to transient bubbles and that the sensitivity to changes in reactivity is larger the smaller the reactor. For sufficiently large bubbles all reactors may reach prompt criticality.
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| 7. |
- Ahlin, Kristina, et al.
(författare)
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Antecedents and neuroimaging patterns in cerebral palsy with epilepsy and cognitive impairment: a population-based study in children born at term
- 2017
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Ingår i: Acta Obstetricia et Gynecologica Scandinavica. - : Wiley. - 1600-0412 .- 0001-6349. ; 96:7, s. 828-836
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Tidskriftsartikel (refereegranskat)abstract
- Introduction. Antecedents of accompanying impairments in cerebral palsy and their relation to neuroimaging patterns need to be explored. Material and methods. A population-based study of 309 children with cerebral palsy born at term between 1983 and 1994. Prepartum, intrapartum, and postpartum variables previously studied as antecedents of cerebral palsy type and motor severity were analyzed in children with cerebral palsy and cognitive impairment and/or epilepsy, and in children with cerebral palsy without these accompanying impairments. Neuroimaging patterns and their relation to identified antecedents were analyzed. Data were retrieved from the cerebral palsy register of western Sweden, and from obstetric and neonatal records. Results. Children with cerebral palsy and accompanying impairments more often had low birthweight (kg) (odds ratio 0.5, 95% confidence interval 0.3-0.8), brain maldevelopment known at birth (p = 0.007, odds ratio infinity) and neonatal infection (odds ratio 5.4, 95% confidence interval 1.04-28.4). Moreover, neuroimaging patterns of maldevelopment (odds ratio 7.2, 95% confidence interval 2.9-17.2), cortical/subcortical lesions (odds ratio 5.3, 95% confidence interval 2.3-12.2) and basal ganglia lesions (odds ratio 7.6, 95% confidence interval 1.4-41.3) were more common, wheras white matter injury was found significantly less often (odds ratio 0.2, 95% confidence interval 0.1-0.5). In most children with maldevelopment, the intrapartum and postpartum periods were uneventful (p
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| 8. |
- Ahlin, Kristina, et al.
(författare)
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Antecedents of cerebral palsy according to severity of motor impairment.
- 2016
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Ingår i: Acta Obstetricia et Gynecologica Scandinavica. - : Wiley. - 1600-0412 .- 0001-6349. ; 95:7, s. 793-802
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to determine whether antecedents and neuroimaging patterns vary according to the severity of motor impairment in children with cerebral palsy. Material and methods. A population-based study in which all 309 term-born children with spastic and dyskinetic cerebral palsy born between 1983 and 1994 and 618 matched controls were studied. Antecedents were retrieved from obstetric records. Information on neuroimaging was retrieved from the cerebral palsy Register of Western Sweden. Cases were grouped by severity of motor impairment: mild (walks without aids), moderate (walks with aids) or severe (dependent on wheelchair). Binary logistic regression, the Cochran-Armitage test for trends, interaction analyses and interrelationship analyses were performed. Results. Antecedents associated with mild motor impairment were antepartum (placental weight, maternal weight and antibiotic therapy) or intrapartum and postpartum adverse events (meconium-stained amniotic fluid, low Apgar score, admission to neonatal intensive care unit and neonatal encephalopathy). Antecedents associated with severe motor impairment were antepartum (congenital infection, small head circumference and brain maldevelopment) or intrapartum and postpartum (emergency cesarean section and maternal antibiotic therapy). Comparisons between mild and severe motor impairment revealed congenital infection, maldevelopment, neonatal encephalopathy and meconium aspiration syndrome significantly more often in the group with severe motor impairment (p
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| 9. |
- Alänge, Sverker, 1951, et al.
(författare)
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Evaluation of Industrial Policy: The Case of the Swedish Textile and Clothing Industry
- 1994
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Ingår i: Small Business Economics. - 1573-0913 .- 0921-898X. ; 6:6, s. 465-475
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Tidskriftsartikel (refereegranskat)abstract
- This paper evaluates the Swedish industrial policy for the textile and clothing industry and provides an interview-based method for assessing the rational for and the effects of state intervention. The rational for government intervention was analyzed based on the existence of possible sources of market failure, such as the function of the capital market; high risk aversion in firms; shortcomings in available information or in business/entrepreneurial competence; and finally, also positive external effects such as demonstration effects were considered. It was found that the Swedish industrial policy, in the period 1970-1990, was general and defensive in character. In the majority of firms interviewed, government policy had either no effect at all on firm behaviour or where effects were found there were no underlying market imperfections. Only in a minority of firms was it found that the policy alleviated market imperfections and changed firms' investment behaviour in a way which was judged to be beneficial for the firms' competitiveness. Therefore, the Swedish industrial policy for the textile and clothing industry was associated with very substantial inefficiencies in the use of sizeable resources.
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| 10. |
- Alänge, Sverker, 1951, et al.
(författare)
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From job-less growth to growth-with-less-jobs: Employment and equity impact of technical and organisational change
- 1996
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Ingår i: Science and Public Policy. - 1471-5430 .- 0302-3427. ; 23:1, s. 27-38
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Tidskriftsartikel (refereegranskat)abstract
- New technical innovations in the form of new production technologies are known to affect productivity, but organisational innovations and new ways of designing products have now been found to have a profound influence on productivity. These innovations have moved the industrialised countries into a stage in which industrial growth is accompanied by the continuous reduction in industrial employment. This development will greatly influence our society and put stringent demands on our political decision-making apparatus to avoid a growth in the 'wealth of nations' going hand-in-hand with a growth in poverty.
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| 11. |
- Alänge, Sverker, 1951, et al.
(författare)
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Some Aspects of An Analytical Framework for Studying the Diffusion of Organizational Innovations
- 1998
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Ingår i: Technology Analysis and Strategic Management. - 0953-7325 .- 1465-3990. ; 10:1, s. 3-21
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this paper is to explore the extent to which the more recent literature on innovation and diffusion, with a prime focus on technical innovations, can contribute to a useful analytical framework for studying the diffusion of organizational innovations. We review that literature, compare the intrinsic features of technical and organizational innovations, and explore what these differences may mean for an eventual analytical framework specifically developed for studying organizational innovations. We conclude that the received 'innovation' literature has a great deal to offer but that some modifications are required. In particular, we suggest that the role of factors 'inside' the firm and of non-market mechanisms for transfer of organizational innovations needs special emphasis.
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| 12. |
- Andersson, Björn A., 1968, et al.
(författare)
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Monitoring and assessing technology choice: the case of solar cells
- 2000
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Ingår i: Energy Policy. ; 28, s. 1037-1049
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this paper is to suggest a methodology that will help us to determine if the present rate and direction of technological change is compatible with the development of a sustainable society. We combine two perspectives on technology assessment. The first focuses on current techno-economic trends and the second on long-term resource and environmental constraints to the diffusion of a new technology. We apply our approach to the case of solar cells. Based on an analysis of technology, actor and market dynamics we suggest that thin-film solar cells are about to dominate the industry. Within the thin-film family, there is competition between alternative designs. The diffusion of three of these will, however, be limited by resource, and perhaps emission, constraints. One design (a-Si) fares much better in terms of these constraints but is less efficient. Three policy issues are identified. First, the diffusion of solar cells is not yet self-sustained and further policy intervention is required. Second, the problems of the current thin-film designs suggest that there is a need for policies both to sustain variety and to balance that requirement with the short-term requirement of cost reduction. Third, policy must ensure that a diffusion of solar cells containing scarce metals does not lead to an erosion of environmental constraints.
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| 13. |
- Andersson, Peter, 1981-, et al.
(författare)
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Correction for dynamic bias error in transmission measurements of void fraction
- 2012
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 83:12, s. 125110-
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic bias errors occur in transmission measurements, such as X-ray, gamma, or neutron radiography or tomography. This is observed when the properties of the object are not stationary in time and its average properties are assessed. The nonlinear measurement response to changes in transmission within the time scale of the measurement implies a bias, which can be difficult to correct for. A typical example is the tomographic or radiographic mapping of void content in dynamic two-phase flow systems. In this work, the dynamic bias error is described and a method to make a first-order correction is derived. A prerequisite for this method is variance estimates of the system dynamics, which can be obtained using high-speed, time-resolved data acquisition. However, in the absence of such acquisition, a priori knowledge might be used to substitute the time resolved data. Using synthetic data, a void fraction measurement case study has been simulated to demonstrate the performance of the suggested method. The transmission length of the radiation in the object under study and the type of fluctuation of the void fraction have been varied. Significant decreases in the dynamic bias error were achieved to the expense of marginal decreases in precision.
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| 14. |
- Andersson, Peter, 1981-, et al.
(författare)
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Design and initial 1D radiography tests of the FANTOM mobile fast-neutron radiography and tomography system
- 2014
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 756, s. 82-93
-
Tidskriftsartikel (refereegranskat)abstract
- The FANTOM system is a tabletop sized fast-neutron radiography and tomography system newly developed at the Applied Nuclear Physics Division of Uppsala University. The main purpose of the system is to provide time-averaged steam-and-water distribution measurement capability inside the metallic structures of two-phase test loops for Light Water Reactor thermal-hydraulic studies using a portable fusion neutron generator. The FANTOM system provides a set of 1D neutron transmission data, which may be inserted into tomographic reconstruction algorithms to achieve a 2D mapping of the steam-and-water distribution. In this paper, the selected design of FANTOM is described and motivated. The detector concept is based on plastic scintillator elements, separated for spatial resolution. Analysis of pulse heights on an event-to-event basis is used for energy discrimination. Although the concept allows for close stacking of a large number of detector elements, this demonstrator is equipped with only three elements in the detector and one additional element for monitoring the yield from the neutron generator. The first measured projections on test objects of known configurations are presented. These were collected using a Sodern Genie 16 neutron generator with an isotropic yield of about 1E8 neutrons per second, and allowed for characterization of the instrument’s capabilities. At an energy threshold of 10 MeV, the detector offered a count rate of about 500 cps per detector element. The performance in terms of spatial resolution was validated by fitting a Gaussian Line Spread Function to the experimental data, a procedure that revealed a spatial unsharpness in good agreement with the predicted FWHM of 0.5 mm.
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| 15. |
- Andersson, Peter, 1981-, et al.
(författare)
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Effects of proton escape on detection efficiency in thin scintillator elements and its consequences for optimization of fast-neutron imaging
- 2011
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 651:1, s. 110-116
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Tidskriftsartikel (refereegranskat)abstract
- Plastic scintillators are commonly used for neutron detection in the MeV energy range, based on n–p scattering and the subsequent deposition of recoil proton's kinetic energy in the detector material. This detection procedure gives a quasi-rectangular energy deposition distribution for mono-energetic neutrons, extending from zero to the neutron energy. However, if the detector sensitive element (DSE) is small, the energy deposition may be incomplete due to the recoil proton escape.In the application of neutron imaging, here exemplified by fast-neutron tomography, two conflicting requirements have been identified: (1) thin DSEs are required to obtain high spatial resolution and (2) energy discrimination may be required to reduce the influence of neutrons being scattered into the DSEs, which generally occurs at lower energies. However, at small DSE widths, the reduction of energy deposition due to recoil proton escape may cause a significant decrease in detection efficiency when energy discrimination is applied.In this work, energy deposition distributions in small-size DSEs have been simulated for Deuterium–Deuterium (DD; 2.5 MeV) and Deuterium–Tritium (DT; 14.1 MeV) fusion neutrons. The intrinsic efficiency has been analyzed as a function of energy discrimination level for various detector widths. The investigations show that proton recoil escape causes a significant drop in intrinsic detection efficiency for thin DSEs. For DT neutrons, the drop is 10% at a width of 3.2 mm and 50% at a width of 0.6 mm, assuming an energy threshold at half the incident neutron energy. The corresponding widths for a DD detector are 0.17 and 0.03 mm, respectively.Finally, implications of the proton escape effect on the design of a fast-neutron tomography device for void distribution measurements at Uppsala University are presented. It is shown that the selection of DSE width strongly affects the instrument design when optimizing for image unsharpness.
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| 16. |
- Andersson, Peter, 1981-
(författare)
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Fast-Neutron Tomography using a Mobile Neutron Generator for Assessment of Steam-Water Distributions in Two-Phase Flows
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes the measurement technique of fast-neutron tomography for assessing spatial distributions of steam and water in two-phase flows. This so-called void distribution is of importance both for safe operation and for efficient use of the fuel in light water reactors, which compose the majority of the world’s commercial nuclear reactors. The technique is aimed for usage at thermal-hydraulic test loops, where heated two-phase flows are being investigated under reactor-relevant conditions.By deploying portable neutron generators in transmission tomography, the technique becomes applicable to stationary objects, such as thermal-hydraulic test loops. Fast neutrons have the advantage of high transmission through metallic structures while simultaneously being relatively sensitive to the water/void content. However, there are also challenges, such as the relatively low yield of commercially available fast-neutron generators, the tendency of fast neutrons to scatter in the interactions with materials and the relatively low efficiency encountered in fast-neutron detection.The thesis describes the design of a prototype instrument, FANTOM, which has been assembled and demonstrated. The main design parameters have been optimized to achieve maximal signal count rate in the detector elements, while simultaneously reaching an image unsharpness of ≤0.5 mm. Radiographic projections recorded with the assembled instrument are presented, and the performance parameters of FANTOM are deduced.Furthermore, tomographic reconstruction methods for axially symmetric objects, which is relevant for some test loops, have been developed and demonstrated on measured data from three test objects. The attenuation distribution was reconstructed with a radial resolution of 0.5 mm and an RMS error of 0.02 cm-1, based on data recorded using an effective measurement time of 3.5 hours per object. For a thermal-hydraulic test loop, this can give a useful indication of the flow mode, but further development is desired to improve the precision of the measurements.Instrument upgrades are foreseen by introducing a more powerful neutron generator and by adding detector elements, speeding up the data collection by several orders of magnitude and allowing for higher precision data. The requirements and performance of an instrument for assessment of arbitrary non-symmetric test loops is discussed, based on simulations.
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| 17. |
- Andersson, Peter, 1981-, et al.
(författare)
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Neutron tomography for void distribution measurements
- 2010
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Ingår i: ENC 2010 Transactions. - 9789295064096 ; , s. 40-45
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Neutron tomography has previously been performed using large, stationary neutron sources such as reactors and spallation sources for applications where the object under study can be transported to the source. This paper accounts for the challenges met when applying neutron tomography using a portable accelerator driven neutron generator, which is required when studying non-transportable objects. In general, portable sources offer significantly lower neutron yields than stationary sources, implying the need for either longer measurement times or highly efficient measurement and/or analysis procedures.The particular application investigated here is the mapping of steam distributions in water (void distribution), which is of high importance for the performance of nuclear fuel assemblies in boiling water reactors (BWR). The void distribution cannot be measured directly in a reactor core, so instead various electrically-heated thermal-hydraulic test loops are used. In these loops, void correlations can be determined in full-size fuel-assembly models, such as FRIGG in Sweden and DESIRE in Holland, but measurements are also performed in smaller, less complicated geometries. Previously, gamma tomography has been used to measure the void distribution in the FRIGG loop. However, improved capabilities to map the void distribution can be expected using neutrons because of their higher sensitivity to water relative to metal structures, as compared to gamma rays. At the same time, neutrons as probe also give rise to some challenges, such as high background from scattering.This paper investigates the possibility to use neutron tomography at axially symmetric objects such as the HWAT test loop in Sweden, where an annular two-phase flow of water/void is confined and heated by a steel cylinder. Monte Carlo simulations of the HWAT geometry and a suggested measurement setup have been carried out, using the particle transport code MCNPX. A reconstruction technique which exploits the symmetries in the test loop has been developed, making it possible to reconstruct the internal void distribution from one single projection. A reconstruction is presented, which is based on simulated data corresponding to a 13-min measurement using a DT source emitting 2∙109 neutrons/s. The reconstruction offers a radial view of the local void fraction in 10 annular sections of HWAT, with uncertainties between 2 and 5 void percent units.
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| 18. |
- Andersson, Peter, 1981-, et al.
(författare)
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Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator
- 2014
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 85:8, s. 085109-
-
Tidskriftsartikel (refereegranskat)abstract
- In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the void distribution in these loops.Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed.In this article, three axially-symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper.Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020 and 0.022 cm-1, solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful indication on the flow mode, and a visualization of the radial material distribution can be obtained. A benefit of this system is its potential to be mounted at any axial height of a two-phase test section without requirements for pre-fabricated entrances or windows. This could mean a significant increase in flexibility of the void distribution assessment capability at many existing two-phase test loops.
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| 19. |
- Andersson, Peter, 1981-, et al.
(författare)
-
Neutron Tomography Using Mobile Neutron Generators for Assessment of Void Distributions in Thermal Hydraulic Test Loops
- 2015
-
Konferensbidrag (refereegranskat)abstract
- Detailed knowledge of the lateral distribution of steam (void) and water in a nuclear fuel assembly is of great value for nuclear reactor operators and fuel manufacturers, with consequences for both reactor safety and economy of operation. Therefore, nuclear relevant two-phase flows are being studied at dedicated thermal-hydraulic test loop, using twophase flow systems ranging from simplified geometries such as heated circular pipes to full scale mock-ups of nuclear fuel assemblies. Neutron tomography (NT) has been suggested for assessment of the lateral distribution of steam and water in such test loops, motivated by a good ability of neutrons to penetrate the metallic structures of metal pipes and nuclear fuel rod mock-ups, as compared to e. g. conventional X-rays, while the liquid water simultaneously gives comparatively good contrast. However, these stationary test loops require the measurement setup to be mobile, which is often not the case for NT setups. Here, it is acknowledged that fast neutrons of 14 MeV from mobile neutron generators constitute a viable option for a mobile NT system. We present details of the development of neutron tomography for this purpose at the division of Applied Nuclear Physics at Uppsala University. Our concept contains a portable neutron generator, exploiting the fusion reaction of deuterium and tritium, and a detector with plastic scintillator elements designed to achieve adequate spatial and energy resolution, all mounted in a light-weight frame without collimators or bulky moderation to allow for a mobile instrument that can be moved about the stationary thermal hydraulic test sections. The detector system stores event-to-event pulse-height information to allow for discrimination based on the energy deposition in the scintillator elements. Experimental results from the tomographic assessment of axially symmetric test objects are shown, as well as simulation results from a scaled up version of the instrument for nonsymmetrical objects in quarter fuel-bundle size objects. In conclusion, the application of tomography on inch-wide vertical pipes has been experimentally demonstrated and simulation results indicate that tomography of the void distribution in nonsymmetrical vertical flows in quarter BWR fuel bundles is also feasible.
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| 20. |
- Andersson, Peter, 1981-
(författare)
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Optimization of Equipment for Tomographic Measurements of Void Distributions using Fast Neutrons
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis describes a novel nondestructive measuring technique for determiningspatial distributions of two-phase water flows. In Boiling Water Reactors, which compose themajority of the world's commercial nuclear reactors, this so called void distribution is of importance for safe operation.The presented measurement technique relies on fast neutron transmission tomography using portable neutron generators. Varying hardware options for such an instrument based on this technique and a prototype instrument, which is under construction, are described. The main design parameters are detailed and motivated from a performance point of view. A Paretomultiple objective optimization of the count rate and image unsharpness is presented. The resulting instrument design comprises an array of plastic scintillators for neutron detection. Such detector elements allow for spectroscopic data acquisition and subsequent reduction of background events at low energy by means of introducing an energy threshold in the analysis.The thesis includes two papers: In paper I, the recoil proton energy deposition distribution resulting from the interaction of the incoming neutrons is investigated for thin plastic scintillator elements. It is shown that the recoil proton losses have a large effect on the pulse height distribution and the intrinsic neutron detection efficiency is calculated for varying energy thresholds.In paper II the performance of the planned FANTOM device is investigated using the particle transport code MCNP5. An axially symmetric phantom void distribution is modeled and there construction is compared with the correct solution. According to the solutions, the phantom model can be reconstructed with 10 equal size ring-shaped picture elements, with a precision of better than 5 void percent units using a deuterium-tritium neutron generator with a yield of 3 · 107 neutrons per second and a measurement time of 13 h. However, it should be noted that commercial neutron generators with a factor of 103 higher yields exist and that the measurement time could decrease to less than a minute if such a neutron generator would beutilized.
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| 21. |
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| 22. |
- Askling, Johan, et al.
(författare)
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Anti-TNF therapy in RA and risk of malignant lymphomas Relative risks and time-trends in the Swedish Biologics Register
- 2008
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Ingår i: Annals of the Rheumatic Diseases. - : BMJ Publishing Group Ltd. - 0003-4967 .- 1468-2060. ; 68:5, s. 648-653
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Tidskriftsartikel (refereegranskat)abstract
- Background: Tumour necrosis factor (TNF) antagonists have proved effective as treatment against rheumatoid arthritis (RA), but the unresolved issue of whether the use of anti-TNF therapy increases the already elevated risk of lymphoma in RA remains a concern.Methods: Using the Swedish Biologics Register (ARTIS), the Swedish Cancer Register, pre-existing RA cohorts and cross-linkage with other national health and census registers, a national RA cohort (n = 67 743) was assembled and patients who started anti-TNF therapy between 1998 and July 2006 (n = 6604) were identified. A general population comparator (n = 471 024) was also assembled and the incidence of lymphomas from 1999 to 31 December 2006 was assessed and compared in these individuals.Results: Among the 6604 anti-TNF-treated RA patients, 26 malignant lymphomas were observed during 26 981 person-years of follow-up, which corresponded to a relative risk (RR) of 1.35 (95% CI 0.82 to 2.11) versus anti-TNF-naive RA patients (336 lymphomas during 365 026 person-years) and 2.72 (95% CI 1.82 to 4.08) versus the general population comparator (1568 lymphomas during 3 355 849 person-years). RA patients starting anti-TNF therapy in 1998–2001 accounted for the entire increase in lymphoma risk versus the two comparators. By contrast, RR did not vary significantly by time since start of first treatment or with the accumulated duration of treatment, nor with the type of anti-TNF agent.Conclusion: Overall and as used in routine care against RA, TNF antagonists are not associated with any major further increase in the already elevated lymphoma occurrence in RA. Changes in the selection of patients for treatment may influence the observed risk.
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| 23. |
- Askling, Johan, et al.
(författare)
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Cancer risk in patients with rheumatoid arthritis treated with anti-tumor necrosis factor alpha therapies : does the risk change with the time since start of treatment?
- 2009
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Ingår i: Arthritis and Rheumatism. - : Wiley. - 0004-3591 .- 1529-0131. ; 60:11, s. 3180-3189
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE:To determine the short-term and medium-term risks of cancer in patients receiving anti-tumor necrosis factor alpha (anti-TNFalpha) therapies that have proven effective in the treatment of chronic inflammatory conditions.METHODS:By linking together data from the Swedish Biologics Register, Swedish registers of RA, and the Swedish Cancer Register, we identified and analyzed for cancer occurrence a national cohort of 6,366 patients with RA who first started anti-TNF therapy between January 1999 and July 2006. As comparators, we used a national biologics-naive RA cohort (n = 61,160), a cohort of RA patients newly starting methotrexate (n = 5,989), a cohort of RA patients newly starting disease-modifying antirheumatic drug combination therapy (n = 1,838), and the general population of Sweden. Relative risks (RRs) were estimated using Cox regression analyses, examining overall RR as well as RR by time since the first start of anti-TNF therapy, by the duration of active anti-TNF therapy, and by the anti-TNF agent received.RESULTS:During 25,693 person-years of followup in 6,366 patients newly starting anti-TNF, 240 first cancers occurred, yielding an RR of 1.00 (95% confidence interval 0.86-1.15) versus the biologics-naive RA cohort, and similar RRs versus the other 2 RA comparators. RRs did not increase with increasing time since the start of anti-TNF therapy, nor with the cumulative duration of active anti-TNF therapy. During the first year following the first treatment start, but not thereafter, dissimilar cancer risks for adalimumab, etanercept, and infliximab were observed.CONCLUSION:During the first 6 years after the start of anti-TNF therapy in routine care, no overall elevation of cancer risk and no increase with followup time were observed.
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| 24. |
- Askling, Johan, et al.
(författare)
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Risk and case characteristics of tuberculosis in rheumatoid arthritis associated with tumor necrosis factor antagonists in Sweden
- 2005
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Ingår i: Arthritis and Rheumatism. - : Wiley. - 0004-3591 .- 1529-0131. ; 52:7, s. 1986-1992
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE:Because treatment with tumor necrosis factor (TNF) antagonists may increase the risk of tuberculosis (TB), and because knowledge of the risk of TB in rheumatoid arthritis (RA) not treated with biologics is scarce and of uncertain generalizability to low-risk populations, this study sought to determine the risk of TB among Swedish patients with RA.METHODS:Using data from Swedish nationwide and population-based registers and data from an ongoing monitoring program of TNF antagonists, the relative risks of TB in patients with RA (versus the general population) and of TB associated with TNF antagonists (versus RA patients not treated with biologics) were determined by comparing the incidence of hospitalization for TB in 3 RA cohorts and 2 general population cohorts from 1999 to 2001. We also reviewed the characteristics of all reported cases of TB in RA patients treated with TNF antagonists in Sweden and calculated the incidence of TB per type of TNF antagonist between 1999 and 2004.RESULTS:During 1999-2001, RA patients who were not treated with TNF antagonists were at increased risk of TB versus the general population (relative risk 2.0, 95% confidence interval [95% CI] 1.2-3.4). RA patients treated with TNF antagonists had a 4-fold increased risk of TB (relative risk 4.0, 95% CI 1.3-12) versus RA patients not treated with TNF antagonists. The reported TB cases during 1999-2004 in RA patients exposed to TNF antagonists (9 infliximab, 4 etanercept, 2 both) were predominantly pulmonary. TB occurred up to 3 years following the start of treatment.CONCLUSION:Irrespective of whether TNF antagonists are administered, Swedish patients with RA are at increased risk of TB. During 1999-2001, TNF antagonists were associated with an increased risk of TB, up to 4-fold in magnitude. This increased risk may persist over time during treatment and is related to both infliximab and etanercept.
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| 25. |
- Askling, Johan, et al.
(författare)
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Time-dependent increase in risk of hospitalisation with infection among Swedish RA patients treated with TNF antagonists
- 2007
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Ingår i: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 66:10, s. 1339-1344
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES:The degree to which treatment with tumour necrosis factor (TNF) antagonists may be associated with increased risks for serious infections is unclear. An observational cohort study was performed using prospectively collected data from the Swedish Biologics Register (ARTIS) and other national Swedish registers.METHODS:First, in the ARTIS, all 4167 rheumatoid arthritis (RA) patients starting TNF antagonist treatment between 1999 and 2003 were identified. Secondly, in the Swedish Inpatient Register, all individuals hospitalised for any reason and who also carried a diagnosis of RA, between 1964 and 2003 (n = 44 946 of whom 2692 also occurred in ARTIS), were identified. Thirdly, in the Swedish Inpatient Register, all hospitalisations listing an infection between 1999 and 2003 were identified. By cross-referencing these three data sets, RRs for hospitalisation with infection associated with TNF antagonist treatment were calculated within the cohort of 44 946 RA patients, using Cox regression taking sex, age, geography, co-morbidity and use of inpatient care into account.RESULTS:Among the 4167 patients treated with TNF antagonists, 367 hospitalisations with infections occurred during 7776 person-years. Within the cohort of 44 496 RA patients, the RR for infection associated with TNF antagonists was 1.43 (95% CI 1.18 to 1.73) during the first year of treatment, 1.15 (95% CI 0.88 to 1.51) during the second year of treatment, and 0.82 (95% CI 0.62 to 1.08) for subjects remaining on their first TNF antagonist treatment after 2 years.CONCLUSION:Treatment with TNF antagonists may be associated with a small to moderate increase in risk of hospitalisation with infection, which disappears with increasing treatment duration.
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| 26. |
- Bacelis, Jonas, 1984, et al.
(författare)
-
Literature-Informed Analysis of a Genome-Wide Association Study of Gestational Age in Norwegian Women and Children Suggests Involvement of Inflammatory Pathways
- 2016
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:8
-
Tidskriftsartikel (refereegranskat)abstract
- Background Five-to-eighteen percent of pregnancies worldwide end in preterm birth, which is the major cause of neonatal death and morbidity. Approximately 30% of the variation in gestational age at birth can be attributed to genetic factors. Genome-wide association studies (GWAS) have not shown robust evidence of association with genomic loci yet. We separately investigated 1921 Norwegian mothers and 1199 children from pregnancies with spontaneous onset of delivery. Individuals were further divided based on the onset of delivery: initiated by labor or prelabor rupture of membranes. Genetic association with ultrasound- dated gestational age was evaluated using three genetic models and adaptive permutations. The top-ranked loci were tested for enrichment in 12 candidate gene-sets generated by text-mining PubMed abstracts containing pregnancy-related keywords. The six GWAS did not reveal significant associations, with the most extreme empirical p = 5.1 x 10(-7). The top loci from maternal GWAS with deliveries initiated by labor showed significant enrichment in 10 PubMed gene-sets, e.g., p = 0.001 and 0.005 for keywords "uterus" and "preterm" respectively. Enrichment signals were mainly caused by infection/inflammation-related genes TLR4, NFKB1, ABCA1, MMP9. Literature-informed analysis of top loci revealed further immunity genes: IL1A, IL1B, CAMP, TREM1, TFRC, NFKBIA, MEFV, IRF8, WNT5A. Our analyses support the role of inflammatory pathways in determining pregnancy duration and provide a list of 32 candidate genes for a follow-up work. We observed that the top regions from GWAS in mothers with labor-initiated deliveries significantly more often overlap with pregnancy-related genes than would be expected by chance, suggesting that increased sample size would benefit similar studies.
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| 27. |
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| 28. |
- Barman, Malin, 1983, et al.
(författare)
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Maternal dietary selenium intake is associated with increased gestational length and decreased risk of preterm delivery
- 2020
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Ingår i: British Journal of Nutrition. - 0007-1145 .- 1475-2662. ; 123:2, s. 209-219
-
Tidskriftsartikel (refereegranskat)abstract
- The first positive genome-wide association study on gestational length and preterm delivery showed associations with a gene involved in the selenium metabolism. In this study we examine the associations between maternal intake of selenium and selenium status with gestational length and preterm delivery in 72,025 women with singleton live births from the population based, prospective Norwegian Mother, Father and Child Cohort Study (MoBa). A self-reported, semi-quantitativ food-frequency questionnaire answered in pregnancy week 22 was used to estimate selenium intake during the first half of pregnancy. Associations were analysed with adjusted linear and cox regressions. Selenium status was assessed in whole blood collected in gestational week 17 (n=2,637). Median dietary selenium intake was 53 (IQR: 44-62) μg/day, supplements provided additionally 50 (30-75) μg/day for supplement-users (n=23,409). Maternal dietary selenium intake was significantly associated with prolonged gestational length (β per SD=0.25, 95% CI=0.07-0.43) and decreased risk for preterm delivery (n=3,618, HR per SD=0.92, 95% CI=0.87-0.98). Neither selenium intake from supplements nor maternal blood selenium status was associated with gestational length or preterm delivery. Hence, this study showed that maternal dietary selenium intake, but not intake of selenium containing supplements, during the first half of pregnancy was significantly associated with decreased risk for preterm delivery. Further investigations, preferably in the form of a large RCT, are needed to elucidate the impact of selenium on pregnancy duration.
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| 29. |
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| 30. |
- Bergek, Anna, 1973, et al.
(författare)
-
Analysing the Dynamics and Fucntionality of Sectoral Innovation Systems - a manual
- 2005
-
Ingår i: DRUID Tenth Anniversary Summer Conference 2005, Copenhagen Business School, Copenhagen, Denmark, June 27-29, 2005.
-
Konferensbidrag (refereegranskat)abstract
- Various researchers and policy analysts have experimented with empirical studies of sectoral innovation systems (SIS), in which attempts have been made to understand the current structure of various innovation systems and trace their dynamics. We have captured the dynamics in terms of not only the structural components of a SIS but also pioneered such an analysis in terms of functional patterns (as well as functionality). In a collaborative work with VINNOVA (the Swedish Agency for Innovation Systems), we have taken the analysis one step further and made explicit a scheme of analysis, or a manual for policy makers. The manual is based on the received literature, our prior experience in developing and applying functional thinking and three experimental case studies, conducted in collaboration with VINNOVA. The manual can be used by policy makers to identify not only the key policy issues but also to set policy goals and to assess the usefulness of various policy instruments.
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| 31. |
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| 32. |
- Bergek, Anna, et al.
(författare)
-
Analyzing the functional dynamics of technological innovation systems : A scheme of analysis
- 2008
-
Ingår i: Research Policy. - : Elsevier BV. - 0048-7333 .- 1873-7625. ; 37:3, s. 407-429
-
Tidskriftsartikel (refereegranskat)abstract
- Various researchers and policy analysts have made empirical studies of innovation systems in order to understand their current structure and trace their dynamics. However, policy makers often experience difficulties in extracting practical guidelines from studies of this kind. In this paper, we operationalize our previous work on a functional approach to analyzing innovation system dynamics into a practical scheme of analysis for policy makers. The scheme is based on previous literature and our own experience in developing and applying functional thinking. It can be used by policy makers not only to identify the key policy issues but also to set policy goals. © 2007 Elsevier B.V. All rights reserved.
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| 33. |
- Bergek, Anna, et al.
(författare)
-
Are tradable green certificates a cost-efficient policy driving technical change or a rent-generating machine? Lessons from Sweden 2003-2008
- 2010
-
Ingår i: Energy Policy. - : Elsevier BV. - 0301-4215. ; 38:3, s. 1255-1271
-
Tidskriftsartikel (refereegranskat)abstract
- In the European policy debate, tradable green certificates (TGC) have been suggested to be a superior regulatory framework for promoting the diffusion of renewable electricity technologies. The purpose of this paper is to assess the performance of the Swedish TGC system, contributing to the European debate on the suitability of different types of frameworks. The expectations of the TGC system were that it would: (a) be effective in terms of increasing the supply of "green" electricity; (b) do this in a cost effective manner (from both a social and a consumer perspective): (c) generate an equitable distribution of costs and benefits and (d) drive technical change. So far, it has performed adequately in terms of effectiveness and social cost effectiveness. However, consumer costs have been substantially higher than expected, very large rents are generated and, at best, it contributes marginally to technical change. Thus. a TGC framework should be selected if the overriding concern is to minimize short term social costs of reaching a certain goal with a high degree of predictability. However, it cannot be expected to also drive technical change, keep consumer costs down and be equitable. Such trade-offs need to be revealed and not obscured by analysts.
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| 34. |
- Bergek, Anna, 1973-, et al.
(författare)
-
Functionality of innovation systems as a rationale and guide in innovation policy
- 2010
-
Ingår i: The Theory and Practice of Innovation Policy.. - Cheltenham : Edward Elgar Publishing Ltd. - 184542848X - 9781845428488
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This comprehensive Handbook explores the interactions between the practice, policy, and theory of innovation. The goal is twofold: to increase insight into this dynamic process, searching for options to improve the effectiveness and efficiency of both policy and innovative practice, and to identify conceptual or empirical lacunae and questions that can guide future research. The Handbook is a joint project from 24 prominent scholars in the field, and although each chapter reveals the insights of its respective authors, two overarching theoretical perspectives provide unique coherence and consistency throughout. This original reference work will not only provide valuable insights for scholars and students on innovation studies, but also to policymakers and practitioners.
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| 35. |
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| 36. |
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| 37. |
- Bergek, Anna, 1973-, et al.
(författare)
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Functions in innovation systems : A framework for analysing energy system dynamics and identifying goals for system-building activities by entrepreneurs and policy makers
- 2008. - 1
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Ingår i: Innovation for a Low Carbon Economy: Economic, Institutional and Management Approaches. - Cheltenham : Edward Elgar. - 9781847203823 ; , s. 79-111
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This book shows that although innovations in energy systems represent a core contribution to achieving national and international energy policy goals, theoretical approaches to understanding innovation differ radically between separate disciplinary perspectives. The need for greater mutual learning between these approaches is met within this study as international academics from economic, institutional and management backgrounds share and analyse their respective approaches, knowledge and insights.
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| 38. |
- Bergek, Anna, 1973, et al.
(författare)
-
Functions in innovation systems: A framework for analysing energy system dynamics and identifying goals for system-building activities by entrepreneurs and policy makers
- 2008
-
Ingår i: Foxon, T., Köhler, J. and Oughton, C. (eds): Innovations for a Low Carbon Economy: Economic, Institutional and Management Approaches, Edward Elgar, Cheltenham, 2008. - 9781847203823 ; , s. 79-111
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 39. |
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| 40. |
- Bergek, Anna, 1973-, et al.
(författare)
-
'Legitimation' and 'development of positive externalities' : two key processes in the formation phase of technological innovation systems
- 2011
-
Ingår i: The Dynamics of Sustainable Innovation Journeys. - Abingdon : Routledge. - 9780415618663 ; , s. 55-72
-
Bokkapitel (refereegranskat)abstract
- Responding to the climate change challenge requires a massive development and diffusion of carbon neutral technologies and, thus, emergence and growth of new socio-technical systems. This paper contributes to an improved understanding of the formative phase of new technological innovation systems (TIS) by outlining a framework for analysing TIS dynamics in terms of structural growth and key innovation-related prodcesses ("functions") and by discussing two of these functions at some depth: "legitimation" and "development of positive externalities". Empirical examples are provided from case studies on renewable energy technologies. We highlight the problematic role of technology assessment studies in shaping legtimacy and the importance of early market formation for the emergence of "packs of entrepreneurs" that may contribute to legitimation, and discuss how exploitation of overlaps between different TISs may create positive externalities, opening up for a powerful "bottom-up" process of system growth. Associated poilcy and management challenges are identified.
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| 41. |
- Bergek, Anna, 1973-, et al.
(författare)
-
'Legitimation' and 'development of positive externalities' : Two key processes in the formation phase of technological innovation systems
- 2008
-
Ingår i: Technology Analysis & Strategic Management. - : Informa UK Limited. - 0953-7325 .- 1465-3990. ; 20:5, s. 575-592
-
Tidskriftsartikel (refereegranskat)abstract
- Responding to the climate change challenge requires a massive development and diffusion of carbon neutral technologies and, thus, emergence and growth of new socio-technical systems. This paper contributes to an improved understanding of the formative phase of new technological innovation systems (TIS) by outlining a framework for analysing TIS dynamics in terms of structural growth and key innovation-related processes ("functions") and by discussing two of these functions at some depth: "legitimation" and "development of positive externalities". Empirical examples are provided from case studies on renewable energy technologies. We highlight the problematic role of technology assessment studies in shaping legitimacy and the importance of early market formation for the emergence of "packs of entrepreneurs" that may contribute to legitimation, and discuss how exploitation of overlaps between different TISs may create positive externalities, opening up for a powerful "bottom-up" process of system growth. Associated policy and management challenges are identified.
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| 42. |
- Bergek, Anna, 1973, et al.
(författare)
-
Technological innovation systems in contexts: Conceptualizing contextual structures and interaction dynamics
- 2015
-
Ingår i: Environmental Innovation and Societal Transitions. - : Elsevier BV. - 2210-4224 .- 2210-4232. ; 16, s. 51-64
-
Tidskriftsartikel (refereegranskat)abstract
- This paper addresses interactions between technological innovation systems (TIS) and wider "context structures". While TIS studies have always considered various kinds of contextual influences, we suggest that the TIS framework can be further strengthened by a more elaborated conceptualization of TIS context structures and TIS-context interactions. For that purpose, we identify and discuss four especially important types of context structures: technological, sectorial, geographical and political. For each of these, we provide examples of different ways in which context structures can interact with a focal TIS and how our understanding of TIS dynamics is enhanced by considering them explicitly. Lessons for analysts are given and a research agenda is outlined.
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| 43. |
- Bergek, Anna, 1973-, et al.
(författare)
-
The emergence of a growth industry : a comparative analysis of the German, Dutch and Swedish wind turbine industries
- 2003. - 1
-
Ingår i: Change, Transformation and Development. - Heidelberg : Physica/Springer. - 9783790815450 - 3790815454 ; , s. 197-228
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This volume contains a collection of papers all concerned with the exploration of economic and social dynamics in relation to the innovation process and its outcomes. This theme is firmly rooted in the Schumpeterian tradition in which an economic perspective is mutually embedded in a wider awareness of the role of other disciplines. Indeed since Schumpeter's time, the degree of specialisation within the social sciences has risen many fold, new sub disciplines continue to emerge, highly specialised theoretical tools and empirical methods continue to be developed, and new fields for the study of management and business overlap with the more traditional social sciences. There is, consequently, a need for connecting principles to offset the dangers of intellectual fragmentation. Evolutionary economics and evolutionary analysis more generally, certainly provide some of these connecting principles. The various contributions to this volume reflect upon this research programme in a number of ways.
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| 44. |
- Bergek, Anna, 1973, et al.
(författare)
-
The emergence of a growth industry: a comparative analysis of the German, Dutch and Swedish wind turbine industries
- 2003
-
Ingår i: Metcalfe, S. & Cantner, U. (Eds): Change, Transformation and Development. Physica/Springer, Heidelberg. - Heidelberg : Physica-Verlag HD. - 9783790827200 ; , s. 197-228
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The objective of this paper is to compare the evolution of the wind turbine industry in Germany, the Netherlands and Sweden. Four factors stand out in explaining the relative success of the German industry: (1) creation of variety in an early phase, (2) establishment of legitimacy of wind energy, (3) the employment of advanced market creation policies in a later phase and (4) the use of industrial policy to favour the domestic industry. Implications for policy include fostering legitimacy for the new technology and creating powerful, predictable and persistent economic incentives.
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| 45. |
- Bergek, Anna, 1973-, et al.
(författare)
-
TIS dynamics in technological, sectoral, political and geographical context: lessons for analysts
- 2014
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper takes its departure in the criticism raised against the technological innovation system (TIS) literature in relation to the research field of socio-technical (sustainability) transitions for neglecting interactions between individual technologies and wider societal “contexts”. We first show that TIS studies have always considered various kinds of contextual systems, while also acknowledging that the TIS framework can be further strengthened by a more explicit conceptualization of TIS contexts and TIS-context interaction. We then propose a conceptual framework, which builds on the idea that TIS contexts could be seen as institutionally coherent structures that reside outside of the focal TIS. Four especially important types of context structures are identified and discussed: technological, sectoral, political and geographical. For each of these, we provide example of different ways in which each type of context can interact with a focal TIS and identify new questions that can be answered if analysts take the respective context more explicitly into account in TIS analyses. From the point of view of future research, this paper is a first step towards developing a framework for analyzing the interrelation between TIS dynamics and sectoral change and building a new TIS-based model of socio-technical transitions.
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| 46. |
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| 47. |
- Branger, Erik, 1988-, et al.
(författare)
-
Comparison of prediction models for Cherenkov light emissions from nuclear fuel assemblies
- 2017
-
Ingår i: Journal of Instrumentation. - 1748-0221. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a tool used by nuclear safeguards inspectors to verify irradiated nuclear fuel assemblies in wet storage based on the Cherenkov light produced by the assembly. Verification that no rods have been substituted in the fuel, so-called partial-defect verification, is made by comparing the intensity measured with a DCVD with a predicted intensity, based on operator fuel declaration. The prediction model currently used by inspectors is based on simulations of Cherenkov light production in a BWR 8x8 geometry. This work investigates prediction models based on simulated Cherenkov light production in a BWR 8x8 and a PWR 17x17 assembly, as well as a simplified model based on a single rod in water. Cherenkov light caused by both fission product gamma and beta decays were considered.The simulations reveal that there are systematic differences between the models, most noticeably with respect to the fuel assembly cooling time. Consequently, a prediction model that is based on another fuel assembly configuration than the fuel type being measured, will result in systematic over or underestimation of short-cooled fuel as opposed to long-cooled fuel. While a simplified model may be accurate enough for fuel assemblies with fairly homogeneous cooling times, the prediction models may differ by up to 18 \,\% for more heterogeneous fuel. Accordingly, these investigations indicate that the currently used model may need to be exchanged with a set of more detailed, fuel-type specific models, in order minimize the model dependant systematic deviations.
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| 48. |
- Branger, Erik, 1988-, et al.
(författare)
-
Experimental evaluation of models for predicting Cherenkov light intensities from short-cooled nuclear fuel assemblies
- 2018
-
Ingår i: Journal of Instrumentation. - 1748-0221. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a tool used by nuclear safeguards inspectors to verify irradiated nuclear fuel assemblies in wet storage based on the recording of Cherenkov light produced by the assemblies. One type of verification involves comparing the measured light intensity from an assembly with a predicted intensity, based on assembly declarations. Crucial for such analyses is the performance of the prediction model used, and recently new modelling methods have been introduced to allow for enhanced prediction capabilities by taking the irradiation history into account, and by including the cross-talk radiation from neighbouring assemblies in the predictions.In this work, the performance of three models for Cherenkov-light intensity prediction is evaluated by applying them to a set of short-cooled PWR 17x17 assemblies for which experimental DCVD measurements and operator-declared irradiation data was available; (1) a two-parameter model, based on total burnup and cooling time, previously used by the safeguards inspectors, (2) a newly introduced gamma-spectrum-based model, which incorporates cycle-wise burnup histories, and (3) the latter gamma-spectrum-based model with the addition to account for contributions from neighbouring assemblies.The results show that the two gamma-spectrum-based models provide significantly higher precision for the measured inventory compared to the two-parameter model, lowering the standard deviation between relative measured and predicted intensities from 15.2% to 8.1% respectively 7.8%.The results show some systematic differences between assemblies of different designs (produced by different manufacturers) in spite of their similar PWR 17x17 geometries, and possible ways are discussed to address such differences, which may allow for even higher prediction capabilities. Still, it is concluded that the gamma-spectrum-based models enable confident verification of the fuel assembly inventory at the currently used detection limit for partial defects, being a 30% discrepancy between measured and predicted intensities, while some false detection occurs with the two-parameter model. The results also indicate that the gamma-spectrum-based prediction methods are accurate enough that the 30% discrepancy limit could potentially be lowered.
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| 49. |
- Branger, Erik, 1988-, et al.
(författare)
-
Experimental study of background subtraction in Digital Cherenkov Viewing Device measurements
- 2018
-
Ingår i: Journal of Instrumentation. - 1748-0221. ; 13:8
-
Tidskriftsartikel (refereegranskat)abstract
- The Digital Cherenkov Viewing Device (DCVD) is an imaging tool used by authority inspectors for partial defect verification of nuclear fuel assemblies in wet storage, i.e. to verify that part of an assembly has not been diverted. One of the currently adopted verification procedures is based on quantitative measurements of the assembly's Cherenkov light emissions, and comparisons to an expected intensity, calculated based on operator declarations. A background subtraction of the intensity data in the recorded images is necessary for accurate quantitative measurements. The currently used background subtraction is aimed at removing an electronics-induced image-wide offset, but it is argued here that the currently adopted procedure may be insufficient.It is recommended that a standard dark-frame subtraction should be used, to remove systematic pixel-wise background due to the electronics, replacing the currently used offset procedure. Experimental analyses show that a dark-frame subtraction would further enhance the accuracy and reliability of DCVD measurements. Furthermore, should ageing of the CCD chip result in larger systematic pixel-wise deviations over time, a dark-frame subtraction can ensure reliable measurements regardless of the age of the CCD chip. It can also help in eliminating any adverse effects of malfunctioning pixels. In addition to the background from electronic noise, ways to compensate for background from neighbouring fuel assemblies and ambient light are also discussed.
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| 50. |
- Branger, Erik, 1988-, et al.
(författare)
-
Image analysis as a tool for improved use of the Digital Cherenkov Viewing Device for inspection of irradiated PWR fuel assemblies.
- 2014
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a tool used to measure the Cherenkov light emitted from irradiated nuclear fuel assemblies stored in water pools. It has been approved by the IAEA for attended gross defect verification, as well as for partial defect verification, where a fraction of the fuel material has been diverted. In this report, we have investigated the current procedures for recording images with the DCVD, and have looked into ways to improve these procedures. Using three different image sets of PWR fuel assemblies, we have analysed what information and results can be obtained using image analysis techniques. We have investigated several error sources that distort the images, and have shown how these errors affect the images. We have also described some of the errors mathematically, and have discussed how these error sources may be compensated for, if the character and magnitude of the errors are known. Resulting from our investigations are a few suggestions on how to improve the procedures and consequently the quality of the images recorded with the DCVD as well as suggestions on how to improve the analysis of collected images. Specifically, a few improvements that should be looked into in the short term are:• Images should be recorded with the fuel assembly perfectly centered in the image, and preferably without any tilt of the DCVD relative to the fuel in order to obtain accurate measurements of the light intensity. Image analysis procedures that may aid the alignment are presented.• To compensate for the distorting effect of the water surface and possible turbulence in the water, several images with short exposure time should be captured rather than one image with long exposure time. Using image analysis procedures, it is possible to sum the images resulting in a final image with less distortions and improved quality.• A reference image should be used to estimate device-related distortions, so that these distortions are compensated for. Ideally, this procedure can also be used to calibrate individual pixels.• The background should be carefully taken into account in order to separate the background level from diffuse signal components, allowing for the background to be subtracted. Accordingly, each measurement campaign should be accompanied by at least one background measurement, recorded from a section in the storage pool where no fuel assemblies are present. Furthermore, the background level should be determined from a larger region in the image and not from one individual pixel, as is currently done.• A database of measurements should be set up, containing DCVD images, information about the applied DCVD settings and the conditions that the DCVD was used in. Any partial defect verification procedure at any time could then be tested against as much data as possible. Accordingly, a database can aid in evaluating and improving partial defect verification methods using DCVD image analysis.Based on the findings and discussions in this report, some long-term improvements are also suggested.
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