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- 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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- Håkansson, Ane, et al.
(författare)
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Digital behandling av linjärpulser från en CdTe-detektor : en förstudie
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The neccesary treatment of the linear pulses from a CdTe detector in order to improve the energy resolution for gamma-ray spectroscopy is normally performed by using analogue technique. In this paper we suggest two methods based on digital treatment of the detector pulses. Significant features of the methods are the improvement of the energy resolution, the fact that virtually no dead time is introduced in the detector system and the simpler handling of such systems. The paper describes the underlying idea of the methods, computer simulations of detector system and actual measurements. Preliminary results show that an improvement of the energy resolution of a factor of 2 to 5, depending on the method, used is achieved.
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- Isaksson, Anneli, et al.
(författare)
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Bacterial grazing by phagotrophic phytoflagellates in a deep humic lake in northern Sweden
- 1999
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 21:2, s. 247-268
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial grazing was measured from June to August 1995 in Lake Örträsket, a deep brown-water lake in northern Sweden. Mixotrophic chrysophytes were the dominating bacterivores at all times, grazing 3-14% of bacterial standing stock daily. The effects of altered nutrient supply and light availability on grazing activity and growth were studied in two mesocosm experiments. Incubation in the dark did not stimulate phagotrophy, which would otherwise be expected if bacteria were mainly being used as an energy source. Furthermore, clearance rates were not reduced after alleviation of nutrient limitation conditions. Rather, phagotrophy may work as a relatively fixed attribute of the mixotrophic community in this lake. When availability of dissolved nutrients is restricted, phagotrophy permits the mixotrophs to outcompete other phytoplankton, but they become less competitive at high nutrient concentrations. The relative share of mixotrophs in relation to total phytoplankton decreased considerably after enrichment with nitrogen + phosphorus.
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- 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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