| 1. |
- Neimane, Aleksija, et al.
(författare)
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Emergence of the Zoonotic Biliary Trematode Pseudamphistomum truncatum in Grey Seals (Halichoerus grypus) in the Baltic Sea
- 2016
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:10, s. e0164782-
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Tidskriftsartikel (refereegranskat)abstract
- The biliary trematode Pseudamphistomum truncatum parasitizes a wide range of fish-eating mammals, including humans. Here we report the emergence of this parasite in grey seals (Halichoerus grypus) in the Baltic Sea. One hundred eighty-three of 1 554 grey seals (11.9%) examined from 2002–2013 had detectable hepatobiliary trematode infection. Parasite identification was confirmed as P. truncatum by sequencing the ITS2 region of a pool of five to 10 trematodes from each of ten seals collected off the coast of seven different Swedish counties. The proportion of seals parasitized by P. truncatum increased significantly over time and with increasing age of seals. Males were 3.1 times more likely to be parasitized than females and animals killed in fishery interactions were less likely to be parasitized than animals found dead or hunted. There was no significant difference in parasitism of seals examined from the Gulf of Bothnia versus those examined from the Baltic Proper. Although the majority of infections were mild, P. truncatum can cause severe hepatobiliary disease and resulted in liver failure in at least one seal. Because cyprinid fish are the second intermediate host for opisthorchiid trematodes, diets of grey seals from the Baltic Sea were analysed regarding presence of cyprinids. The proportion of gastrointestinal tracts containing cyprinid remains was ten times higher in seals examined from 2008 to 2013 (12.2%) than those examined from 2002 to 2007 (1.2%) and coincided with a general increase of trematode parasitism in the host population. The emergence and relatively common occurrence of P. truncatum in grey seals signals the presence of this parasite in the Baltic Sea ecosystem and demonstrates how aquatic mammals can serve as excellent sentinels of marine ecosystem change. Investigation of drivers behind P. truncatum emergence and infection risk for other mammals, including humans, is highly warranted.
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| 2. |
- Bignert, Anders, et al.
(författare)
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9. Contaminants and Health of Aquatic Wildlife
- 2012. - 1
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Ingår i: Ecology and Animal Health. - Uppsala : Baltic University Press. - 9789186189129 ; , s. 73-85
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Bokkapitel (populärvet., debatt m.m.)
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| 3. |
- Bredhult, Carolina, et al.
(författare)
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Study of the relation between the incidence of uterine leiomyomas and the concentrations of PCB and DDT in Baltic gray seals
- 2008
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Ingår i: Reproductive Toxicology. - : Elsevier BV. - 0890-6238 .- 1873-1708. ; 25:2, s. 247-255
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Tidskriftsartikel (refereegranskat)abstract
- Exposure to environmental contaminants is believed to be associated with the previously described decrease in the reproduction rate of Baltic gray seals. In the present study the prevalence of uterine leiomyomas was investigated in 257 Baltic gray seal females examined during 1973-2007, in relation to the levels of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) in Baltic biota, using an estimated exposure index. Additionally, the proliferative activity in leiomyomas, occurrence of corpora lutea, and blubber concentrations of PCB and DDT were investigated in a subset of females. Leiomyomas were only found in females 22-41 years old, at a prevalence of 65%. No differences in blubber concentrations of PCB or DDT were detected between the subset of leiomyoma-bearing females and reference females, but the estimated exposure index indicated that the PCB level in Baltic biota might be related to the leiomyoma prevalence in Baltic gray seal females.
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| 4. |
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| 5. |
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| 6. |
- Carlsson Almlöf, Jonas, et al.
(författare)
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Novel risk genes for systemic lupus erythematosus predicted by random forest classification
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- Genome-wide association studies have identified risk loci for SLE, but a large proportion of the genetic contribution to SLE still remains unexplained. To detect novel risk genes, and to predict an individual's SLE risk we designed a random forest classifier using SNP genotype data generated on the "Immunochip" from 1,160 patients with SLE and 2,711 controls. Using gene importance scores defined by the random forest classifier, we identified 15 potential novel risk genes for SLE. Of them 12 are associated with other autoimmune diseases than SLE, whereas three genes (ZNF804A, CDK1, and MANF) have not previously been associated with autoimmunity. Random forest classification also allowed prediction of patients at risk for lupus nephritis with an area under the curve of 0.94. By allele-specific gene expression analysis we detected cis-regulatory SNPs that affect the expression levels of six of the top 40 genes designed by the random forest analysis, indicating a regulatory role for the identified risk variants. The 40 top genes from the prediction were overrepresented for differential expression in B and T cells according to RNA-sequencing of samples from five healthy donors, with more frequent over-expression in B cells compared to T cells.
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| 7. |
- Claesson, Åsa, et al.
(författare)
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Novel design for diode-pumped miniature lasers using microstructured silicon carriers
- 2000
-
Ingår i: Advanced Solid State Lasers. - : Optica Publishing Group.
-
Konferensbidrag (refereegranskat)abstract
- A new design concept for compact diode-pumped solid-state lasers is presented. The design is based on a microstructured silicon carrier with etched v-grooves. This silicon microbench provides efficient thermal management at 10W pumping level, as well as compact integration and alignment of all active and passive optical components of compact diode-pumped solid-state lasers. In initial experiments, a Nd:YAG laser built on the microbench delivered a continuous-wave output of 3W.
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| 8. |
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| 9. |
- Håkansson, Ane, 1959-, et al.
(författare)
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An experimental study of the neutron emission from spent PWR fuel
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Measurements of the thermal and epithermal neutron emission from eleven 15x15 and fourteen 17x17 PWR fuel assemblies have been performed. In the measurements a FORK detector supplied by Euroatom was utilised. The neutron flux was observed to depend on the burnup to approximately the fourth power. Also the strong dependence on initial enrichment could be verified. The latter dependency suggests a possible method to determine the initial enrichment. Such a method is considered as an important feature of safeguard as well as in fuel processing at the planned encapsulation plant for spent nuclear fuel.
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Jacobsson, Staffan, 1972-, et al.
(författare)
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A Tomographic Method for Verification of the Integrity of Spent Nuclear Fuel
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A tomographic method for experimental investigation of the integrity of usedLWR fuel has been developed. It is based on measurements of the gamma radiation fromthe fission products in the fuel rods. A reconstruction code of the algebraic type has beenwritten. The potential of the technique has been examined in extensive simulationsassuming a gamma-ray energy of either 0.66 MeV (137Cs) or 1.27 MeV (154Eu).The resultsof the simulations for BWR fuel indicate that single fuel rods or groups of rods replacedwith water or fresh fuel can be reliably detected independent of their position in the fuelassembly using 137Cs radiation. For PWR fuel the same result is obtained with the exceptionof the most central positions. Here the more penetrable radiation from 154Eu must be used inorder to allow a water channel to be distinguished from a fuel rod.The results of the simulations have been verified experimentally for a 8x8 BWRfuel assembly. Special equipment has been constructed and installed at the interim storageCLAB. The equipment allows the mapping of the radiation field around a fuel assemblywith the aid of a germanium detector fitted with a collimator with a vertical slit. Theintensities measured in 2 520 detector positions were used as input for the reconstructioncode used in the simulations. The results agreed very well with the simulations and revealedsignificantly a position containing a water channel in the central part of the assembly.
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| 14. |
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| 15. |
- Jacobsson, Staffan, et al.
(författare)
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A Tomographic Method for Verification of the Integrity of Spent Nuclear Fuel Assemblies - I: Simulation Studies
- 2001
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Ingår i: Nuclear Technology. - 0029-5450. ; 135:2, s. 131-145
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Tidskriftsartikel (refereegranskat)abstract
- A tomographic method for experimental investigation of the integrity of used light water reactor fuel assemblies has been developed. It is based on spectroscopic measurements of the gamma radiation from fission products in fuel rods. The method utilizes beforehand information about the nominal geometry of both the measured fuel assembly and the measurement equipment. A reconstruction code of the algebraic type has been written. The potential of the technique has been examined in extensive simulations, assuming a gamma-ray energy of either 662 keV (137Cs) or 1274 keV (154Eu). The ability of detecting various configurations of manipulated rods, both single and in groups, has been investigated. Two main types of manipulations have been simulated. First, there is the removal of rods without replacement. The results indicate that all investigated configurations of removed rods in boiling water reactor (BWR) fuel can be reliably detected using 137Cs radiation. For pressurized water reactor (PWR) fuel, the same result is obtained, with the exception of the most central positions. Here, the more penetrating radiation from 154Eu may have to be used. Second, there is the replacement of rods with fresh fuel or fuel-like material. The results clearly indicate that all simulated cases of such manipulation can be most confidently detected. The simulations include various configurations of replaced rods in both BWR and PWR fuel, using both gamma-ray energies.
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| 16. |
- Jacobsson, Staffan, et al.
(författare)
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A Tomographic Method for Verification of the Integrity of Spent Nuclear Fuel Assemblies - II: Experimental Investigation
- 2001
-
Ingår i: Nuclear Technology. - 0029-5450 .- 1943-7471. ; 135:2, s. 146-153
-
Tidskriftsartikel (refereegranskat)abstract
- A tomographic method for verification of the integrity of used light water reactor fuel has been experimentally investigated. The method utilizes emitted gamma rays from fission products in the fuel rods. The radiation field is recorded in a large number of positions relative to the assembly, whereby the source distribution is reconstructed using a special-purpose reconstruction code.An 8 × 8 boiling water reactor fuel assembly has been measured at the Swedish interim storage (CLAB), using installed gamma-scanning equipment modified for the purpose of tomography. The equipment allows the mapping of the radiation field around a fuel assembly with the aid of a germanium detector fitted with a collimator with a vertical slit. Two gamma-ray energies were recorded: 662 keV (137Cs) and 1274 keV (154Eu). The intensities measured in 2520 detector positions were used as input for the tomographic reconstruction code. The results agreed very well with simulations and significantly revealed a position containing a water channel in the central part of the assembly.
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| 17. |
- Jacobsson, Staffan, 1970-, et al.
(författare)
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Tomographic measurements of thermal power in nuclear fuel rods : Stage 2 progress report December 1999
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents recent progress in a project on tomographic measurements of thermal power in nuclear fuel rods, carried out at Uppsala University and funded via the Swedish Centre for Nuclear Technology, KTC. The project is executed in three stages, of which this report describes a set of studies made during the second stage.Experimental studies have been performed using a laboratory mock-up, modelling a fuel assembly of the BWR8x8 type, in which tomographic data collection is made using BGO scintillator detectors and a data-acquisition system based on single-channel analysers. Gamma-ray scattering has been identified as a major contributor to systematic errors in the measurement of relative activity contents in the 63 rods of the mock-up assembly. Since scattering causes build-up of radiation at lower energies, it may be taken into account in the tomographic analyses by introducing a so-called effective attenuation coefficient in the reconstruction models, being slightly lower than the theoretical coefficient. Studies show that this approach may enhance the precision in the measurement of relative rod-activity contents from about 3‑4% down to about 1.2‑1.4%.Data collection has also been performed using a separate, spectroscopic data-acquisition system, in a set of measurements where inactive rods have been used to introduce scattering in order to analyse its effects on the collected data. The results indicate that most of the adverse effects of scattering may be eliminated by deploying a spectroscopic system with peak analysis including background subtraction. Consequently, such a system should be considered for Stage 3 of this project.Simulation studies have also been executed to analyse the measurement uncertainties introduced by geometric deviations from the nominal positions of the four sections of a SVEA‑64 fuel assembly. It was found that the standard deviation of relative rod activities caused by the largest displacements allowed by the nominal gaps enclosing each section was about 0.5%, which may be considered acceptable.
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| 18. |
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| 19. |
- Jacobsson Svärd, Staffan, 1970-
(författare)
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A Tomographic Measurement Technique for Irradiated Nuclear Fuel Assemblies
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The fuel assemblies used at the Swedish nuclear power plants contain typically between 100 and 300 fuel rods. An experimental technique has been demanded for determining the relative activities of specific isotopes in individual fuel rods without dismantling the assemblies. The purpose is to validate production codes, which requires an experimental relative accuracy of <2 % (1 σ).Therefore, a new, non-destructive tomographic measurement technique for irradiated nuclear fuel assemblies has been developed. The technique includes two main steps: (1) the gamma-ray flux distribution around the assembly is recorded, and (2) the interior gamma-ray source distribution in the assembly is reconstructed. The use of detailed gamma-ray transport calculations in the reconstruction procedure enables accurate determination of the relative rod-by-rod source distribution.To investigate the accuracy achievable, laboratory equipment has been constructed, including a fuel model with a well-known distribution of 137Cs. Furthermore, an instrument has been constructed and built for in-pool measurements on irradiated fuel assemblies at nuclear power plants.Using the laboratory equipment, a relative accuracy of 1.2 % was obtained (1 σ). The measurements on irradiated fuel resulted in a repeatability of 0.8 %, showing the accuracy that can be achieved using this instrument. The agreement between rod-by-rod data obtained in calculations using the POLCA–7 production code and measured data was 3.1 % (1 σ).Additionally, there is a safeguards interest in the tomographic technique for verifying that no fissile material has been diverted from fuel assemblies, i.e. that no fuel rods have been removed or replaced. The applicability has been demonstrated in a measurement on a spent fuel assembly. Furthermore, detection of both the removal of a rod as well as the replacement with a non-active rod has been investigated in detail and quantitatively established using the laboratory equipment.
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| 20. |
- Jacobsson Svärd, Staffan, 1970-, et al.
(författare)
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Detection of Dislocated Individual Fuel Rods in a Nuclear Fuel Assembly using Tomographic Measurements
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A method is suggested for identifying and quantifying possible dislocations of individual fuel rods in an irradiated nuclear fuel assembly. The method is designed for application in tomographic measurements of nuclear fuel assemblies. The source distribution of gamma radiation is reconstructed using a tomographic algorithm, in which the pixel pattern is adapted to the assembly geometry. By comparing the reconstructed source concentration in opposite parts of each fuel rod in the assembly, quantitative information may be obtained about possible dislocations.Theoretical considerations have been applied and data from simulations of a nuclear fuel assembly with single dislocated rods have been used in tomographic reconstructions. The investigations indicate that the method should be applicable for identification of dislocations larger than a few tenths of a mm.
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| 21. |
- Jacobsson Svärd, Staffan, et al.
(författare)
-
Non-destructive experimental determination of the pin-power distribution in nuclear fuel
- 2003
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A need for validation of modern core-analysis codes with respect to the calculated pin-power distribution has been recognized. A non-destructive experimental method for such validation has been developed, based on a tomographic technique. Each axial node of the fuel assembly is measured separately and the relative pin-by-pin content of the direct fission product Ba-140 is determined. Investigations performed so far indicate that 1-2% (1 σ) accuracy can be obtained.A measuring device has been constructed which, when fully equipped, is designed to measure a complete BWR assembly in 25 axial nodes within an eight-hour work shift. The applicability of the constructed device has been demonstrated in measurements at the Swedish BWR Forsmark 2 on irradiated fuel with a cooling time of 4-5 weeks. Data from the core-analysis code POLCA-7 have been compared to measured pin-by-pin contents of Ba-140. An agreement of 3.1% (1 σ) has been demonstrated.As compared to the conventional method, involving gamma scanning of individual fuel pins, this method does not require the fuel to be disassembled. Neither does the fuel channel have to be removed. The cost per measured fuel pin is in the order of 20 times lower than the conventional method.
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| 22. |
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| 23. |
- Jacobsson Svärd, Staffan, et al.
(författare)
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Nondestructive Experimental Determination of the Pin-Power Distribution in Nuclear Fuel Assemblies
- 2005
-
Ingår i: Nuclear Technology. - 0029-5450. ; 151:1, s. 70-76
-
Tidskriftsartikel (refereegranskat)abstract
- A need for validation of modern production codes with respect to the calculated pin-power distribution has been recognized. A nondestructive experimental method for such validation has been developed based on a tomographic technique. The gamma-ray flux distribution is recorded in each axial node of the fuel assembly separately, whereby the relative rod-by-rod content of the fission product 140Ba is determined. Measurements indicate that 1 to 2% accuracy (1 sigma) is achievable.A device has been constructed for in-pool measurements at reactor sites. The applicability has been demonstrated in measurements at the Swedish boiling water reactor (BWR) Forsmark 2 on irradiated fuel with a cooling time of 4 to 5 weeks. Data from the production code POLCA-7 have been compared to measured rod-by-rod contents of 140Ba. An agreement of 3.1% (1 sigma) has been demonstrated.It is estimated that measurements can be performed on a complete BWR assembly in 25 axial nodes within an 8-h work shift. As compared to the conventional method, involving gamma scanning of individual fuel rods, this method does not require the fuel to be disassembled nor does the fuel channel have to be removed. The cost per measured fuel rod is estimated to be an order of magnitude lower than the conventional method.
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| 24. |
- Jacobsson Svärd, Staffan, 1970-, et al.
(författare)
-
Tomografisk bestämning av termisk effekt i kärnbränslestavar - Förstudie
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna rapport redovisar en förstudie av möjligheterna att med tomografisk mätning bestämma effektfördelningen i ett bränsleelement. Förstudien avses vara en första fas i en serie av tre, som, om utfallet successivt bedöms tillräckligt lovande, skall leda till en utprovad prototyp för tomografisk effektmätning.
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| 25. |
- Jacobsson Svärd, Staffan, et al.
(författare)
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Tomography for partial-defect verification : experiences from measurements using different devices
- 2006
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Ingår i: ESARDA Bulletin. - 0392-3029. ; 33, s. 15-25
-
Tidskriftsartikel (refereegranskat)abstract
- Three devices of different types have been used in tomographic measurements for the purpose of partial-defect verification on the single-rod level. The devices range from a laboratory device used in measurements on a fuel model to an in-pool device used in measurements on irradiated fuel in a fuel-handling pool.The tomographic technique accounted for in this paper involves measurements of the gamma-ray flux distribution around a fuel assembly followed by computer-aided reconstruction of the internal source distribution. The results are rod-by-rod values of the relative concentrations of selected gamma-emitting isotopes. Also cross-sectional images are obtained.The tomographic technique presented here has proven to be robust and reliable. In laboratory experiments on a fuel model, reconstructions of relative rod-by-rod activities have been obtained with 1.5 % accuracy (1 σ). Using an in-pool device in measurements on fuel with a cooling time of about 4 weeks, data on fuel rods have been obtained in agreement with production-code calculations. Furthermore, tomographic images of good quality have been acquired.The applicability of the tomographic technique for partial-defect verification on the single-rod level has been investigated and demonstrated. The gamma-ray source concentration reconstructed in a position corresponding to a removed or replaced rod has been significantly lower than that of normal rods.Finally, requirements and properties of a device for tomographic measurements on nuclear fuel are discussed. It is argued that the use of a detector system with high energy resolution and high peak efficiency in connection to spectroscopic peak analysis is beneficial.
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| 26. |
- Jansson, Peter, 1971-, et al.
(författare)
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A Device for Nondestructive Experimental Determination of the Power Distribution in a Nuclear Fuel Assembly
- 2006
-
Ingår i: Nuclear science and engineering. - 0029-5639 .- 1943-748X. ; 152:1, s. 76-86
-
Tidskriftsartikel (refereegranskat)abstract
- There is a general interest in experimentally determining the power distribution in nuclear fuel. The prevalent method is to measure the distribution of the fission product 140Ba, which represents the power distribution over the last few weeks. In order to obtain the rod-by-rod power distribution, the fuel assemblies have to be dismantled.In this paper, a device for experimental nondestructive determination of the thermal rod-by-rod power distribution in boiling water reactor and pressurized water reactor fuel assemblies is described. It is based on measurements of the 1.6-MeV gamma radiation from the decay of 140Ba/La and utilizes a tomographic method to reconstruct the rod-by-rod source distribution. No dismantling of the fuel assembly is required.The device is designed to measure an axial node in 20 min with a precision of >2% (1). It is primarily planned to be used for validation of production codes for core simulation but may also be used for safeguards purposes.
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| 27. |
- Jansson, Peter, 1971-, et al.
(författare)
-
A Feasibility Study of BGO Scintillation Detectors for Tomographic Measurements on Nuclear Fuel
- 2000
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A study of BGO detectors has been performed. The purpose of the study was to determine geometrical shape of the scintillator crystals in order to be suited for use in tomographic measurements on nuclear fuel. Computer calculations using Monte Carlo techniques were used. High count-rate experiments were performed on three nuclear fuel assemblies with the shapes of the crystals determined by the calculations. The resulting characteristics of the detectors show that they are suitable in a tomographic measurement.
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| 28. |
- Jansson, Peter, 1971-, et al.
(författare)
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A Method of Measuring Decay Heat in Spent Nuclear Fuel using Gamma-ray Spectroscopy
- 2001
-
Ingår i: Waste Management Symposium 2001 (WM'01).
-
Konferensbidrag (refereegranskat)abstract
- In this paper, a method is presented for determining the decay heat in spent nuclear fuel by using gamma-ray spectroscopy. Using this method, the decay heat may be determined within ten minutes per assembly i.e. it is well suited for industrial applications in, for example, an encapsulation facility. The method has been tested and evaluated in the wet Swedish Central Storage for Spent Fuel, CLAB. Although only tested in a wet storage, the method should also be applicable for dry storage.The objective of developing the method was primarily to investigate possibilities to achieve a fast, robust and reasonable accurate determination of decay heat by gamma-ray measurements on fuel assemblies. Such a method could also be for verification of burnup and cooling time, for safeguard purposes prior to encapsulation, (1).So far, measurements and calculations on 35 BWR- and 34 PWR-assemblies, with various nuclear data, have been performed. The test measurements, using preliminary measuring equipment, have shown that the decay heat may be determined within an uncertainty of 3%.
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| 29. |
- Jansson, Peter, 1971-, et al.
(författare)
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Calculations of the Neutron Flux Outside BWR 8×8 Spent-Fuel Assemblies and the Sensitivity to Fuel Pin Diversion
- 2004
-
Ingår i: Nuclear Technology. - 0029-5450 .- 1943-7471. ; 146:1, s. 58-64
-
Tidskriftsartikel (refereegranskat)abstract
- The possibility of detecting replaced fuel rods in a spent-fuel assembly by means of measurement of the emitted neutron- and gamma-ray radiation has been investigated by computer simulations. The radiation field outside a boiling water reactor 8 × 8 fuel assembly with varying patterns of fuel rods replaced with lead dummies was calculated using a simple model for the source distribution and the Monte Carlo code MCNP-4C for the radiation field. In particular, the sensitivity of the thermal neutron field as measured in a Fork detector to various replacement patterns was investigated. The results suggest a detection limit of 5% of the fuel mass replaced, i.e., 3 out of 63 rods, independently of the pattern of the replaced rods.
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| 30. |
- Jansson, Peter, 1971-, et al.
(författare)
-
Detection of Partial Defects in irradiated BWR fuel assemblies. A Preliminary Study.
- 2002
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Konferensbidrag (refereegranskat)abstract
- The possibility of detecting partial defects in spent BWR fuel assemblies by means of measurements of the emitted neutron and gamma-ray radiation has been the subject in a preliminary study. Computer simulations have been made both for the case of removed rods and the case of replacement by dummy rods. The focus was put on the replacement scenario in which verication by using weighing techniques is not possible. Using the Origen-S code, the source strength for a typical 8x8 BWR fuel assembly was calculated. For various geometrical patterns of the replaced rods, the radiation eld outside the fuel assembly was calculated with the Monte Carlo code MCNP-4C.The results suggest that neutron measurements alone, signicantly can reveal if 3 % or more of the total ssile material has been replaced. In a case where operator-declared data are unavailable or assumed incorrect, an anomalous neutron signal will indicate erroneously stated burnup and/or replaced fuel rods. An inspector is then either forced to use an indirect method such as gamma scanning to verify the burnup or tomography in order to directly verify a possible partial defect.
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| 31. |
- Jansson, Peter, 1971-, et al.
(författare)
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Gamma-ray measurements of spent PWR fuel and determination of residual power
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The method for determining residual thermal power in spent BWR fuel described in ISV-4/97 have been used in an extended study where spent PWR fuel assemblies have been considered. The experimental work has been carried out at the interim storage CLAB. By using the 137Cs radiation it is shown in the present study that it is possible to experimentally determine the residual thermal power within 3%.
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| 32. |
- Jansson, Peter, 1971-, et al.
(författare)
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Gamma-Ray Spectroscopy Measurements of Decay Heat in Spent Nuclear Fuel
- 2002
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Ingår i: Nuclear Science and Engineering. - 0029-5639. ; 141:2, s. 129-139
-
Tidskriftsartikel (refereegranskat)abstract
- A method for determining the residual thermal power in spent nuclear fuel using gamma-ray spectroscopy is suggested. It is based on the correlation between the residual power and the 137Cs activity, which is nearly linear for fuel with cooling times between 10 and 50 yr. Using available data of calorimetrically measured values of the decay heat in 69 boiling water reactor and pressurized water reactor spent-fuel assemblies resulted in agreement with a standard deviation of 3%.
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| 33. |
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| 34. |
- Jansson, Peter, 1971-, et al.
(författare)
-
Tomographic measurement of thermal power in nuclear fuel : Stage 1 - Final report
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report summarises the results obtained in the first stage of a three-stage project on “Tomographic measurement of thermal power in nuclear fuel”, carried out at Uppsala University and funded via the Swedish Centre for Nuclear Technology, KTC. The goal of the three-stage project is to build a tomographic device and use it for non-destructive measurement of the pin-wise thermal power in nuclear fuel assemblies at a Swedish nuclear power plant.Covered in the report are descriptions of the algorithms and software for tomographic reconstruction developed for the purpose, results of sensitivity studies for geometric uncertainties, tests of detector systems in a laboratory environment as well as on nuclear fuel at a reactor site, descriptions of a laboratory mock-up intended to be used in the second step of the project and estimations of the achievable uncertainty in measured relative pin-wise power using the suggested methods.
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| 35. |
- Lundqvist Saleh, Tobias, et al.
(författare)
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Recent Progress in the Design of a Tomographic Device for Measurements of the Three-Dimensional Pin-Power Distribution in Irradiated Nuclear Fuel Assemblies
- 2010
-
Ingår i: Nuclear science and engineering. - 0029-5639 .- 1943-748X. ; 165:2, s. 232-239
-
Tidskriftsartikel (refereegranskat)abstract
- A tomographic technique for determination of the thermal power distribution in nuclear fuel assemblies is under development. The purpose is to provide an experimental validation tool for core simulation codes. Such codes are essential for the operation of nuclear power reactors, and validation is important in the process of improving and developing the codes as well as the fuel. The tomographic method is nonintrusive and offers large amounts of data within a normal revision shutdown. In earlier experimental investigations using a test platform, the method proved useful, demonstrating results of satisfying quality. However, the measuring setup also revealed nonfeasible properties related to transport, decontamination, and background radiation shielding. In this paper, the design of a new measuring device is presented. It is based on experiences from the test platform, but its size and weight make it advantageous regarding transports and decontamination. Moreover, the design inherently allows for more efficient background shielding. The latter has been investigated in a detailed study using the MCNP simulation code. The results confirm the high levels of background radiation observed in the test platform. It is also concluded that the shielding properties in the new design are sufficient.
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| 36. |
- Matsson, Ingvar, et al.
(författare)
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Fission Gas Release Determination Using an Anti-Compton Shield Detector
- 1998
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Ingår i: Nuclear Technology. - 0029-5450. ; 122:3, s. 276-283
-
Tidskriftsartikel (refereegranskat)abstract
- Poolside measurements of fission gas release (FGR) in fuel pins have been made using gamma-ray spectroscopy with a Ge detector, measuring 85Kr activity in the fuel rod plenum. The gamma-ray energy spectra from irradiated nuclear fuel are characterized by prominent Compton distributions that can obscure the weak 514-keV 85Kr peak. To improve the sensitivity, the detector has been provided with an anti-Compton shield of six Bi3Ge4O12 detectors. Laboratory tests of the detector system showed that the maximum peak-to-Compton (p/c) ratio was improved by a factor of ~6. The results of the poolside measurement p/c ratio showed a somewhat smaller improvement (a factor of ~4) because of scattered gamma radiation from the surrounding material. However, the precision in the poolside FGR measurements was improved substantially utilizing the Compton shield.
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| 37. |
- Matsson, Ingvar, 1963-
(författare)
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Studies of Nuclear Fuel Performance Using On-site Gamma-ray Spectroscopy and In-pile Measurements
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Presently there is a clear trend of increasing demands on in-pile performance of nuclear fuel. Higher target burnups, part length rods and various fuel additives are some examples of this trend. Together with an increasing demand from the public for even safer nuclear power utilisation, this implies an increased focus on various experimental, preferably non-destructive, methods to characterise the fuel.This thesis focuses on the development and experimental evaluation of such methods. In its first part, the thesis presents a method based on gamma-ray spectroscopy with germanium detectors that have been used at various power reactors in Europe. The aim with these measurements is to provide information about the thermal power distribution within fuel assemblies in order to validate core physics production codes. The early closure of the Barsebäck 1 BWR offered a unique opportunity to perform such validations before complete depletion of burnable absorbers in Gd-rods had taken place. To facilitate the measurements, a completely submersible measuring system, LOKET, was developed allowing for convenient in-pool measurements to be performed.In its second part, the thesis describes methods that utilise in-pile measurements. These methods have been used in the Halden test-reactor for determination of fission gas release, pellet-cladding interaction studies and fuel development studies.Apart from the power measurements, the LOKET device has been used for fission gas release (FGR) measurements on single fuel rods. The significant reduction in fission gas release in the modern fuel designs, in comparison with older designs, has been demonstrated in a series of experiments. A FGR database covering a wide range of burnup, power histories and fuel designs has been compiled and used for fuel performance analysis. The fission gas release has been measured on fuel rods with average burnups well above 60 MWd/kgU. The comparison between core physics calculations (PHOENIX-4/POLCA-7) and the in-pool measurements of thermal power indicates that the nodal power can generally be predicted with an accuracy within 4% and the bundle power with an accuracy better than 2%, expressed as rms errors.In-pile experiments have successfully simulated the conditions that occur in a fuel rod following a primary debris failure, being secondary fuel degradation. It was concluded that massive hydrogen pick-up takes place during the first few days following the primary failure and that a pre-oxidized layer does not function as a barrier towards hydriding in an environment with a very high partial pressure of hydrogen. Another series of in-pile experiments clearly indicate that increased UO2 grain size is an effective way of suppressing fission gas release in LWR fuel up to the burnup level covered (55 MWd/kgUO2).
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| 38. |
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| 39. |
- Osifo, Otasowie, et al.
(författare)
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Verification and determination of the decay heat in spent PWR fuel by means of gamma scanning
- 2008
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Ingår i: Nuclear science and engineering. - 0029-5639 .- 1943-748X. ; 160:1, s. 129-143
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Tidskriftsartikel (refereegranskat)abstract
- Decay heat is an important design parameter at the future Swedish spent nuclear fuel repository. It will be calculated for each fuel assembly using dedicated depletion codes, based on the operator-declared irradiation history. However, experimental verification of the calculated decay heat is also anticipated. Such verification may, be obtained by, gamma scanning using the established correlation between the decay heat and the emitted gamma-ray intensity from Cs-137. In this procedure, the correctness of the operator-declared fuel parameters can be verified. Recent achievements of the gamma-scanning technique include the development of a dedicated spectroscopic data-acquisition system and the use of an advanced calorimeter for calibration. Using this system, the operator-declared burnup and cooling time of 31 pressurized water reactor fuel assemblies was verified experimentally, to within 2.2% (1 sigma) and 1.9% (1 sigma), respectively. The measured decay heat agreed with calorimetric data within 2.3% (1 sigma). whereby the calculated decay, heat was verified within 2.3% (1 sigma). The measuring time per fuel assembly was similar to 15 min. In case reliable operator-declared data are not available, the gamma-scanning technique also provides a means to independently measure the decay, heat. The results obtained in this procedure agreed with calorimetric data within 2.7% (1 sigma).
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| 40. |
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| 41. |
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| 42. |
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| 43. |
- Willman, Christofer, et al.
(författare)
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A nondestructive method for discriminating MOX fuel from LEU fuel for safeguards purposes
- 2006
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 33:9, s. 766-773
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Tidskriftsartikel (refereegranskat)abstract
- Plutonium-rich mixed oxide fuel (MOX) is increasingly used in thermal reactors. However, spent MOX fuel could be a potential source of nuclear weapons material and a safeguards issue is therefore to determine whether a spent nuclear fuel assembly is of MOX type or of LEU (Low Enriched Uranium) type. In this paper, we present theoretical and experimental results of a study that aims to investigate the possibilities of using gamma-ray spectroscopy to determine whether a nuclear fuel assembly is of MOX or of LEU type. Simulations with the computer code ORIGEN-ARP have been performed where LEU and MOX fuel types with varying enrichment and burnup as well as different irradiation histories have been modelled. The simulations indicate that the fuel type determination may be achieved by using the intensity ratio Cs-134/Eu-154. An experimental study of MOX fuel of 14 x 14 PWR type and LEU fuel of both 15 x 15 and 17 x 17 type is also reported in this paper. The outcome of the experimental study support the conclusion that MOX fuel may be discriminated from LEU fuel by measuring the suggested isotopic ratio.
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| 44. |
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| 45. |
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| 46. |
- Willman, Christofer, et al.
(författare)
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Nondestructive assay of spent nuclear fuel with gamma-ray spectroscopy
- 2006
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Ingår i: Annals of Nuclear Energy. - 0306-4549. ; 33:5, s. 427-438
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Tidskriftsartikel (refereegranskat)abstract
- An important issue in nuclear safeguards is to verify operator-declared data of spent nuclear fuel. Various techniques have therefore been assigned for this purpose. A nondestructive approach is to measure the gamma radiation from spent nuclear fuel assemblies. Using this technique, parameters such as burnup and cooling time can be calculated or verified. In this paper, we propose the utilization of gamma rays from 137Cs, 134Cs and 154Eu to determine the consistency of operator-declared information. Specifically, we have investigated to what extent irradiation histories can be verified. Computer simulations were used in order to determine limits for detecting small deviations from declared data. In addition, the technique has been experimentally demonstrated on 12 PWR fuel assemblies. A technique for determining burnup and cooling time for fuel assemblies where no operator-declared information is available is also presented. In such a case, the burnup could be determined with 1.6% relative standard deviation and the cooling time with 1.5%.
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