| 1. |
- Charatsidou, Elina, et al.
(författare)
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Proton irradiation-induced cracking and microstructural defects in UN and (U,Zr)N composite fuels
- 2024
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Ingår i: Journal of Materiomics. - : Elsevier. - 2352-8478 .- 2352-8486. ; 10:4, s. 906-918
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Tidskriftsartikel (refereegranskat)abstract
- Proton irradiation with a primary ion energy of 2 MeV was used to simulate radiation damage in UN and (U,Zr)N fuel pellets. The pellets, nominally at room temperature, were irradiated to peak levels of 0.1, 1, 10 dpa and 100.0 dpa resulting in a peak hydrogen concentration of at most 90 at. %. Microstructure and mechanical properties of the samples were investigated and compared before and after irradiation. The irradiation induced an increase in hardness, whereas a decrease in Young’s modulus was observed for both samples. Microstructural characterization revealed irradiation-induced cracking, initiated in the bulk of the material, where the peak damage was deposited, propagating towards the surface. Additionally, transmission electron microscopy was used to study irradiation defects. Dislocation loops and fringes were identified and observed to increase in density with increasing dose levels. The high density of irradiation defects and hydrogen implanted are proposed as the main cause of swelling and consequent sample cracking, leading simultaneously to increased hardening and a decrease in Young's modulus.
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| 2. |
- Ekberg, Christian, 1967, et al.
(författare)
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Nitride fuel for Gen IV nuclear power systems
- 2018
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 318:3, s. 1713-1725
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Forskningsöversikt (refereegranskat)abstract
- Nuclear energy has been a part of the energy mix in many countries for decades. Today in principle all power producing reactors use the same techniqe. Either PWR or BWR fuelled with oxide fuels. This choice of fuel is not self evident and today there are suggestions to change to fuels which may be safer and more economical and also used in e.g. Gen IV nuclear power systems. One such fuel type is the nitrides. The nitrides have a better thermal conductivity than the oxides and a similar melting point and are thus have larger safety margins to melting during operation. In addition they are between 30 and 40% more dense with respect to fissile material. Drawbacks include instability with respect to water and a sometimes complicated fabrication route. The former is not really an issue with Gen IV systems but for use in the present fleet. In this paper we discuss both production and recycling potential of nitride fuels.
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| 3. |
- Eriksson, Marcus, et al.
(författare)
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Inherent Safety of Fuels for Accelerator-driven Systems
- 2005
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Ingår i: Nuclear Technology. - 0029-5450 .- 1943-7471. ; 151:3, s. 314-333
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Tidskriftsartikel (refereegranskat)abstract
- Transient safety characteristics of accelerator-driven systems using advanced minor actinide fuels have been investigated. Results for a molybdenum-based Ceramic-Metal (CerMet) fuel, a magnesia-based Ceramic-Ceramic fuel, and a zirconium-nitride-based fuel are reported. The focus is on the inherent safety aspects of core design. Accident analyses are carried out for the response to unprotected loss-of-flow and accelerator beam-overpower transients and coolant voiding scenarios. An attempt is made to establish basic design limits for the fuel and cladding. Maximum temperatures during transients are determined and compared with design limits. Reactivity effects associated with coolant void, fuel and structural expansion, and cladding relocation are investigated. Design studies encompass variations in lattice pitch and pin diameter. Critical mass studies are performed. The studies indicate favorable inherent safety features of the CerMet fuel. Major consideration is given to the potential threat of coolant voiding in accelerator-driven design proposals. Results for a transient test case study of a postulated steam generator tube rupture event leading to extensive coolant voiding are presented. The study underlines the importance of having a low coolant void reactivity value in a lead-bismuth system despite the high boiling temperature of the coolant. It was found that the power rise following a voiding transient increases dramatically near the critical state. The studies suggest that a reactivity margin of a few dollars in the voided state is sufficient to permit significant reactivity insertions.
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| 4. |
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| 5. |
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| 6. |
- Johnson, Kyle D., et al.
(författare)
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Spark plasma sintering and porosity studies of uranium nitride
- 2016
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Ingår i: Journal of Nuclear Materials. - : Elsevier. - 0022-3115 .- 1873-4820. ; 473, s. 13-17
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a number of samples of UN sintered by the SPS method have been fabricated, and highly pure samples ranging in density from 68% to 99.8%TD-corresponding to an absolute density of 14.25 g/cm3 out of a theoretical density of 14.28 g/cm3-have been fabricated. By careful adjustment of the sintering parameters of temperature and applied pressure, the production of pellets of specific porosity may now be achieved between these ranges. The pore closure behaviour of the material has also been documented and compared to previous studies of similar materials, which demonstrates that full pore closure using these methods occurs near 97.5% of relative density.
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| 7. |
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| 8. |
- Jolkkonen, Mikael, et al.
(författare)
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Kinetic evidence for different mechanisms of interaction of black mamba toxins MT alpha and MT beta with muscarinic receptors
- 2001
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Ingår i: Toxicon. - 0041-0101 .- 1879-3150. ; 39:2-3, s. 377-382
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Tidskriftsartikel (refereegranskat)abstract
- By studying the influence of two toxins from the black mamba Dendroaspis polylepis on the kinetics of [H-3]-N-methylscopolamine binding to muscarinic acetylcholine receptors from rat cerebral cortex, it was revealed that these toxins, MT alpha and MT beta, interact with the receptors via kinetically distinct mechanisms. MT beta bound to receptors in a one-step, readily reversible process with the dissociation constant K-d = 5.3 mu M. The binding mechanism of MT alpha was more complex, involving at least two consecutive steps. A fast receptor-toxin complex formation (K-T = 3.8 mu M) was followed by a slow process of isomerisation of this complex (k(i) = 1.8 x 10(-2) s(-1), half-time 39 s). A similar two-step interaction mechanism has been established for a related toxin, MT2 from the green mamba D. angusticeps (K-T = 1.4 mu M, k(i) = 8.3 x 10(-4) s(-1), half-time 840 s). The slow isomerisation process delays the effect of MT alpha and MT2, but increases their apparent potency compared to toxins unable to induce the isomerisation process.
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| 9. |
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| 10. |
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| 11. |
- Jolkkonen, Mikael, et al.
(författare)
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Thermo-chemical modelling of uranium-free nitride fuels
- 2004
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Ingår i: Journal of Nuclear Science and Technology. - : Informa UK Limited. - 0022-3131 .- 1881-1248. ; 41:4, s. 457-465
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Tidskriftsartikel (refereegranskat)abstract
- A production process for americium-bearing, uranium-free nitride fuels was modelled using the newly developed ALCHYMY thermochemical database. The results suggested that the practical difficulties with yield and purity are of a kinetic rather than a thermodynamical nature. We predict that the immediate product of the typical decarburisation step is not methane, but hydrogen cyanide. HCN may then undergo further reactions upon cooling, explaining the difficulty in observing any carbophoric molecules in the gaseous off stream. The thermal stability of nitride fuels in different environments was also estimated. We show that sintering of nitride compounds containing americium should be performed under nitrogen atmosphere in order to the avoid the excessive losses of americium reported from sintering under inert gas. Addition of nitrogen in small amounts to fuel pin filling gas also appears to significantly improve the in-pile stability of transuranium nitride fuels.
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| 12. |
- Jolkkonen, Mikael, et al.
(författare)
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Uranium nitride fuels in superheated steam
- 2017
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Ingår i: Journal of Nuclear Science and Technology. - : Informa UK Limited. - 0022-3131 .- 1881-1248.
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Tidskriftsartikel (refereegranskat)abstract
- Uranium mononitride (UN) pellets of different densities were subjected to a superheatedsteam/argon mixture at atmospheric pressure to evaluate their resistance to hydrolysis. Completedegradation of pure UN pellets was obtained within 1 hour in 0.50 bar steam at 500 °C. Theidentified reaction products were uranium dioxide, ammonia and hydrogen gas, with no detectableamounts of nitrogen oxides formed. However, the reaction could not be carried to completion, andthe presence of uranium sesquinitride and higher uranium oxides or uranium oxynitrides in the solidresidue is indicated. Evolution of elemental nitrogen was seen in connection with very high reactionrates. The porosity of the pellets was identified as the most important factor determining reactionrates at 400 – 425 °C, and it is suggested that in dense pellets, cracking due to internal volumeincrease initiates a transition from slow surface corrosion to pellet disintegration. The implicationsfor the use of nitride fuels in light water reactors are discussed, with some observations concerninghydrolysis as a method for 15N recovery from isotopically enriched spent nitride fuel.
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| 13. |
- Karlsson, E., et al.
(författare)
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Snake toxins with high selectivity for subtypes of muscarinic acetylcholine receptors
- 2000
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Ingår i: Biochimie. - 0300-9084 .- 1638-6183. ; 82:9-10, s. 793-806
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Tidskriftsartikel (refereegranskat)abstract
- There are five subtypes of muscarinic acetylcholine receptors (M-1 to M-5) which control a large number of physiological processes, such as the function of heart and smooth muscles, glandular secretion, release of neurotransmitters, gene expression and cognitive functions as learning and memory. A selective ligand is very useful for studying the function of a subtype in presence of other subtypes, which is the most common situation, since a cell or an organ usually has several subtypes. There are many non-selective muscarinic ligands, but only few selective ones. Mambas, African snakes of genus Dendroaspis have toxins, muscarinic toxins, that are selective for M-1, M-2 and M-4 receptors. They consist of 63-66 amino acids and four disulfides which form four loops. They are members of a large group of snake toxins, three-finger toxins; three loops are extended like the middle fingers of a hand and the disulfides and the shortest loop are in the palm of the hand. Some of the toxins target the allosteric site which is located in a cleft of the receptor molecule close to its extracellular part. A possible explanation to the good selectivity is that the toxins bind to the allosteric site, but because of their size they probably also bind to extracellular parts of the receptors which are rather different in the various subtypes. Some other allosteric ligands also have good selectivity, the alkaloid brucine and derivatives are selective for M-1, M-3 and M-4 receptors. Muscarinic toxins have been used in several types of experiments. For instance radioactively labeled M-1 and M-4 selective toxins were used in autoradiography of hippocampus from Alzheimer patients. One significant change in the receptor content was detected in one region of the hippocampus, dentate gyrus, where M-4 receptors were reduced by 50% in patients as compared to age-matched controls. Hippocampus is essential for memory consolidation. M-4 receptors in dentate gyrus may play a role, since they decreased in Alzheimers disease which destroys the memory. Another indication of the role of M-4 receptors for memory is that injection of the M-4 selective antagonist muscarinic toxin 3 (M-4-toxin 1) into rat hippocampus produced amnesia.
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| 14. |
- Malkki, Pertti, et al.
(författare)
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Manufacture of fully dense uranium nitride pellets using hydride derived powders with spark plasma sintering
- 2014
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 452:1-3, s. 548-551
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Tidskriftsartikel (refereegranskat)abstract
- Applying a combination of hydriding/nitriding of metallic uranium with the spark plasma sintering technique, we show that uranium nitride pellets with an average porosity of 0.2% may be manufactured. This is considerably smaller than the lowest porosity previously reported in the literature. The high density is attained by sintering at 1650 °C for only three minutes.
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| 15. |
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| 16. |
- Nasman, J., et al.
(författare)
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Recombinant expression of a selective blocker of M-1 muscarinic receptors
- 2000
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 271:2, s. 435-439
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Tidskriftsartikel (refereegranskat)abstract
- Mamba venoms contain peptides with high selectivity for muscarinic receptors, Due to the limited availability of the M-1 muscarinic receptor-selective MT7 or ml-toxin 1, the peptide was expressed in Sf9 cells using a synthetic cDNA and purified, The isolated peptide had over four orders of magnitude higher affinity for the M-1 compared to M-2-M-5 muscarinic receptors, The peptide strongly inhibited Ca2+ mobilisation ;through recombinant and endogenously expressed M-1 receptors, having no effect on the function of the other subtypes. The MT7 peptide provides a unique tool for identification and functional characterisation of M-1 receptors in cells and tissues,
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| 17. |
- Neuhausen, J., et al.
(författare)
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Properties of irradiated LBE and Pb
- 2015
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Ingår i: Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Materials Compatibility, Thermal-hydraulics and Technologies - 2015 Edition (NEA-7268). - : Nuclear Energy Agency of the OECD (NEA).
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 18. |
- Tesinsky, Milan, et al.
(författare)
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The impact of americium on transients in the European Lead-cooled SYstem ELSY loaded with nitride fuel
- 2012
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 50, s. 56-62
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Tidskriftsartikel (refereegranskat)abstract
- The Unprotected Loss-of-Flow transient (ULOF) and the Unprotected Transient-Over-Power (UTOP) have been evaluated for a modified design of the European Lead-cooled SYstem (ELSY) using nitride fuel. Additional americium has been added to the core in concentrations of 0%, 4% and 8%. During ULOF, fuel and clad asymptotic temperatures stabilize below limits. For UTOP, however, the maximum allowed cladding temperature limit is exceeded at EOC and introduction of a power penalty is necessary for Am transmutation. The power penalty is higher than that reported for SFR.
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| 19. |
- Tucek, Kamil, et al.
(författare)
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Studies of an accelerator-driven transuranium burner with hafnium-based inert matrix fuel
- 2007
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Ingår i: Nuclear Technology. - 0029-5450 .- 1943-7471. ; 157:3, s. 277-298
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Tidskriftsartikel (refereegranskat)abstract
- Neutronic and burnup characteristics of an accelerator-driven transuranium burner in a startup mode were studied. Different inert and absorbing matrices as well as lattice configurations were assessed in order to identify suitable fuel and core design configurations. Monte Carlo transport and burnup codes were used in the analyses. The lattice pin pitch was varied to optimize the source efficiency and coolant void worth while respecting key thermal and material-related design constraints posed by fuel and cladding. A HfN matrix appeared to provide a good combination of neutronic, burnup, and safety characteristics: maintaining a hard neutron spectrum, yielding acceptable coolant void reactivity and source efficiency, and alleviating the burnup reactivity swing. A conceptual design of a (TRU,Hf)N fueled, lead-bismuth eutectic-cooled accelerator-driven system was developed. Twice higher neutron fission-to absorption probabilities in Am isotopes were achieved compared to reactor designs relying on ZrN or YN inert matrix fuel. The production of higher actinides in the fuel cycle is hence limited, with a Cm fraction in the equilibrium fuel being similar to 40% lower than for cores with ZrN matrix-based fuel. The burnup reactivity swing and associated power peaking in the core are managed by an appropriate choice of cycle length (100 days) and by core enrichment zoning. A safety analysis shows that the system is protected from instant damage during unprotected beam overpower transient.
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| 20. |
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| 21. |
- Wallenius, Janne, et al.
(författare)
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Towards industrial-scale manufacture of UN fuel for water-cooled reactors
- 2020
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Ingår i: GLOBAL 2019 - International Nuclear Fuel Cycle Conference and TOP FUEL 2019 - Light Water Reactor Fuel Performance Conference. - : American Nuclear Society. ; , s. 1144-1146
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Konferensbidrag (refereegranskat)abstract
- The use of U15N fuel in water cooled reactors permits to increase the fuel average residence time by 40-60%1,2. This corresponds to a reduced cost for manufacture of fuel assemblies and waste packages, as well as a reduced cost for refuelling. The industrial application of UN fuels requires to improve the resistance of the fuel to steam corrosion and to develop methods for manufacture that are commercially competitive. In this contribution we describe the activities carried out at LeadCold, KTH and Promation Nuclear towards these goals.
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| 22. |
- Zhang, Youpeng, et al.
(författare)
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Transmutation of americium in a large sized sodium-cooled fast reactor loaded with nitride fuel
- 2013
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 53, s. 26-34
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Tidskriftsartikel (refereegranskat)abstract
- We have performed the transient analysis of a large sized sodium-cooled reactor loaded with nitride fuel modified by different fractions of americium. Unprotected loss-of-offsite power, unprotected loss-of-flow and unprotected transient-over-power accidents were considered as the postulated transient and simulated with the SAS4A/SASSYS code based on the geometrical model of a BN1200 type sodium-cooled fast reactor (SFR) with the rated power of 2900 MWth. Safety parameters used in the transient simulation model were obtained from the SERPENT Monte Carlo calculations. If 100 K margin to fuel melting was maintained, 2 wt.% and 6 wt.% Am content could be permitted for the nitride fuel loaded BN1200 operating with the maximum linear power rating of 37 kW/m and 33 kW/m respectively, providing Am transmutation rates of 3.9 kg/TW h(th) and 13.7 kg/TW h(th). These transmutation rates are more than 6 times higher than the ones previously reported for oxide fuel loaded BN600 operating with the maximum linear power ratings of 37 kW/m and metallic fuel loaded Integral Fast Reactor (IFR) operating with the maximum linear power rating of 33 kW/m respectively, being their reference cases with permitting 1 wt.% Am content.
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| 23. |
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