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- 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
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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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- Matsson, Ingvar, et al.
(författare)
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LOKET - a gamma-ray spectroscopy system for in-pool measurements of thermal power distribution in irradiated nuclear fuel
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 569:3, s. 872-882
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Tidskriftsartikel (refereegranskat)abstract
- An important issue in the operations of nuclear power plants is the independent validation of core physics codes like e.g. Westinghouse PHOENIX-4/POLCA-7. Such codes are used to predict the thermal power distribution down to single node level in the core. In this paper, a dedicated measurement system (LOKET) is described and experimental results are discussed. The system is based on a submergible housing, containing a high-resolution germanium detector, allowing for measurements in-pool. The system can be transported to virtually any nuclear power plant's fuel storage pool for measurements in-pool during outage. The methodology utilises gamma radiation specific for La-140, whose decay is governed by the parent Ba-140, reflecting a weighted average power distribution, representative for the last weeks of operation of the core. Good agreements between measured power distribution and core physics calculations (Ba distribution) have been obtained during a series of experiments at Leibstadt NPP in Switzerland and Cofrentes NPP in Spain (BWRs) for both fuel assemblies and single fuel rods. The system has proven as a very useful tool for the experimental validation of core calculations also for the most complex fuel designs and challenging core configurations. Experimental errors (on the 1 - sigma level), has been demonstrated below +/- 2% on nodal level for assembly measurements.
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- Matsson, Ingvar, et al.
(författare)
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On-site Gamma-ray Spectroscopic Measurements of Fission Gas Release in Irradiated Nuclear Fuel
- 2007
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 65:1, s. 36-45
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Tidskriftsartikel (refereegranskat)abstract
- An experimental, non-destructive in-pool, method for measuring fission gas release (FGR) in irradiated nuclear fuel has been developed. Using the method, a significant number of experiments have been performed in-pool at several nuclear power plants of the BWR type. The method utilises the 514 keV gamma-radiation from the gaseous fission product Kr-85 captured in the fuel rod plenum volume. A submergible measuring device (LOKET) consisting of an HPGe-detector and a collimator system was utilised allowing for single rod measurements on virtually all types of BWR fuel. A FGR database covering a wide range of burn-ups (up to average rod burn-up well above 60 MWd/kgU), irradiation history, fuel rod position in cross section and fuel designs has been compiled and used for computer code benchmarking, fuel performance analysis and feedback to reactor operators. Measurements clearly indicate the low FGR in more modern fuel designs in comparison to older fuel types.
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- 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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