| 1. |
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| 2. |
- 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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| 3. |
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| 4. |
- 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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| 5. |
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| 6. |
- 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
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Ingår i: Nuclear Technology. - 0029-5450 .- 1943-7471. ; 135:2, s. 146-153
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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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| 7. |
- 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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| 8. |
- 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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| 9. |
- Jacobsson Svärd, Staffan, 1970-, et al.
(författare)
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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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| 10. |
- 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
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Ingår i: Nuclear science and engineering. - 0029-5639 .- 1943-748X. ; 152:1, s. 76-86
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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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| 11. |
- Jansson, Peter, 1971-, et al.
(författare)
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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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| 12. |
- 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
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Ingår i: Waste Management Symposium 2001 (WM'01).
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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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| 13. |
- Jansson, Peter, 1971-, et al.
(författare)
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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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| 14. |
- 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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| 15. |
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| 16. |
- Jansson, Peter, 1971-, et al.
(författare)
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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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| 17. |
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