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Publications (10 of 12) Show all publications
Johnson, K. D., Wallenius, J., Jolkkonen, M. & Claisse, A. (2016). Spark plasma sintering and porosity studies of uranium nitride. Journal of Nuclear Materials, 473, 13-17
Open this publication in new window or tab >>Spark plasma sintering and porosity studies of uranium nitride
2016 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 473, p. 13-17Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Generation IV, Nuclear fuel, Pore closure, Sintering, SPS, Uranium nitride, Nitrides, Nuclear fuels, Porosity, Spark plasma sintering, Uranium, Uranium compounds, Number of samples, Relative density, Sintering parameters, Specific porosity, Theoretical density
National Category
Mineral and Mine Engineering Physical Sciences
Identifiers
urn:nbn:se:kth:diva-186981 (URN)10.1016/j.jnucmat.2016.01.037 (DOI)000373490700003 ()2-s2.0-84959376726 (Scopus ID)
Note

QC 20160518

Available from: 2016-05-18 Created: 2016-05-16 Last updated: 2017-11-30Bibliographically approved
Malkki, P., Jolkkonen, M., Hollmer, T. & Wallenius, J. (2014). Manufacture of fully dense uranium nitride pellets using hydride derived powders with spark plasma sintering. Journal of Nuclear Materials, 452(1-3), 548-551
Open this publication in new window or tab >>Manufacture of fully dense uranium nitride pellets using hydride derived powders with spark plasma sintering
2014 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 452, no 1-3, p. 548-551Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Porosity, Spark plasma sintering, Uranium compounds, Hydriding, Metallic uranium, Spark plasma sintering techniques, Uranium nitride pellets
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-161521 (URN)10.1016/j.jnucmat.2014.06.012 (DOI)000339657200078 ()2-s2.0-84903788189 (Scopus ID)
Funder
Swedish Research CouncilEU, FP7, Seventh Framework Programme
Note

QC 20150313

Available from: 2015-03-13 Created: 2015-03-12 Last updated: 2017-12-04Bibliographically approved
Zhang, Y., Wallenius, J. & Jolkkonen, M. (2013). Transmutation of americium in a large sized sodium-cooled fast reactor loaded with nitride fuel. Annals of Nuclear Energy, 53, 26-34
Open this publication in new window or tab >>Transmutation of americium in a large sized sodium-cooled fast reactor loaded with nitride fuel
2013 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 53, p. 26-34Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
BN1200, Nitride fuel, Americium transmutation, Transient analysis
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-120294 (URN)10.1016/j.anucene.2012.08.009 (DOI)000315550500004 ()2-s2.0-84870179549 (Scopus ID)
Note

QC 20130405

Available from: 2013-04-05 Created: 2013-04-04 Last updated: 2017-12-06Bibliographically approved
Tesinsky, M., Wallenius, J., Jolkkonen, M. & Zhang, Y. (2012). The impact of americium on transients in the European Lead-cooled SYstem ELSY loaded with nitride fuel. Annals of Nuclear Energy, 50, 56-62
Open this publication in new window or tab >>The impact of americium on transients in the European Lead-cooled SYstem ELSY loaded with nitride fuel
2012 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 50, p. 56-62Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
ELSY; UTOP; ULOF; Nitride
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-100196 (URN)10.1016/j.anucene.2012.07.007 (DOI)000312120600008 ()2-s2.0-84866522334 (Scopus ID)
Note

QC 20130118. Updated from submitted to published.

Available from: 2012-08-06 Created: 2012-08-06 Last updated: 2017-12-07Bibliographically approved
Tucek, K., Jolkkonen, M., Wallenius, J. & Gudowski, W. (2007). Studies of an accelerator-driven transuranium burner with hafnium-based inert matrix fuel. Nuclear Technology, 157(3), 277-298
Open this publication in new window or tab >>Studies of an accelerator-driven transuranium burner with hafnium-based inert matrix fuel
2007 (English)In: Nuclear Technology, ISSN 0029-5450, E-ISSN 1943-7471, Vol. 157, no 3, p. 277-298Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
accelerator-driven system, inert matrix, lead/bismuth, nitride fuels, minor-actinide, systems, transmutation, neutronics, reactors, design
National Category
Engineering and Technology
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-16406 (URN)000244428500005 ()2-s2.0-33947515064 (Scopus ID)
Funder
StandUp
Note

QC 20150727

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
Eriksson, M., Wallenius, J., Jolkkonen, M. & Cahalan, J. E. (2005). Inherent Safety of Fuels for Accelerator-driven Systems. Nuclear Technology, 151(3), 314-333
Open this publication in new window or tab >>Inherent Safety of Fuels for Accelerator-driven Systems
2005 (English)In: Nuclear Technology, ISSN 0029-5450, E-ISSN 1943-7471, Vol. 151, no 3, p. 314-333Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
accelerator-driven systems, accidents, minor actinide fuel
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-4980 (URN)000231203900010 ()2-s2.0-23844448469 (Scopus ID)
Note
QC 20101008. Uppdaterad från accepted till published (20101008).Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2017-12-05Bibliographically approved
Jolkkonen, M., Streit, M. & Wallenius, J. (2004). Thermo-chemical modelling of uranium-free nitride fuels. Journal of Nuclear Science and Technology, 41(4), 457-465
Open this publication in new window or tab >>Thermo-chemical modelling of uranium-free nitride fuels
2004 (English)In: Journal of Nuclear Science and Technology, ISSN 0022-3131, E-ISSN 1881-1248, Vol. 41, no 4, p. 457-465Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
thermo-chemical modelling, minor actinides, uranium-free nitride fuels, carbothermic nitridation, decarburisation, thermal stability, accelerator-driven systems, carbothermic synthesis, plutonium nitride, behavior, system, matrix
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-23506 (URN)000222102500008 ()2-s2.0-2942755880 (Scopus ID)
Note

QC 20100525 QC 20111028

Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
Jolkkonen, M., Oras, A., Toomela, T., Karlsson, E., Jarv, J. & Akerman, K. E. (2001). Kinetic evidence for different mechanisms of interaction of black mamba toxins MT alpha and MT beta with muscarinic receptors. Toxicon, 39(2-3), 377-382
Open this publication in new window or tab >>Kinetic evidence for different mechanisms of interaction of black mamba toxins MT alpha and MT beta with muscarinic receptors
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2001 (English)In: Toxicon, ISSN 0041-0101, E-ISSN 1879-3150, Vol. 39, no 2-3, p. 377-382Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
snake toxins (Dendroaspis polylepis), muscarinic acetylcholine, receptor, muscarinic toxin, binding mechanism, amino-acid-sequence, acetylcholine-receptors, binding, antagonist
Identifiers
urn:nbn:se:kth:diva-20049 (URN)000089441800026 ()
Note
QC 20100525Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
Nasman, J., Jolkkonen, M., Ammoun, S., Karlsson, E. & Akerman, K. E. (2000). Recombinant expression of a selective blocker of M-1 muscarinic receptors. Biochemical and Biophysical Research Communications - BBRC, 271(2), 435-439
Open this publication in new window or tab >>Recombinant expression of a selective blocker of M-1 muscarinic receptors
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2000 (English)In: Biochemical and Biophysical Research Communications - BBRC, ISSN 0006-291X, E-ISSN 1090-2104, Vol. 271, no 2, p. 435-439Article in journal (Refereed) Published
Abstract [en]

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,

Keywords
muscarinic receptor, toxin, baculovirus, Sf9 cells, protein expression, amino-acid-sequence, mamba dendroaspis-angusticeps, acetylcholine-receptors, toxin, purification, m1-toxin, binding, venom
Identifiers
urn:nbn:se:kth:diva-19748 (URN)000087000800029 ()
Note
QC 20100525Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
Karlsson, E., Jolkkonen, M., Mulugeta, E., Onali, P. & Adem, A. (2000). Snake toxins with high selectivity for subtypes of muscarinic acetylcholine receptors. Biochimie, 82(9-10), 793-806
Open this publication in new window or tab >>Snake toxins with high selectivity for subtypes of muscarinic acetylcholine receptors
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2000 (English)In: Biochimie, ISSN 0300-9084, E-ISSN 1638-6183, Vol. 82, no 9-10, p. 793-806Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
snake toxins, muscarinic receptor subtypes, selectivity, mamba dendroaspis-angusticeps, amino-acid-sequence, potassium channels, calcium-channel, smooth-muscle, messenger-rna, high-affinity, venom, binding, rat
Identifiers
urn:nbn:se:kth:diva-20213 (URN)000165789900002 ()
Note
QC 20100525Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6818-5724

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