| 1. |
- Charatsidou, Elina, et al.
(author)
-
Proton irradiation-induced cracking and microstructural defects in UN and (U,Zr)N composite fuels
- 2024
-
In: Journal of Materiomics. - : Elsevier. - 2352-8478 .- 2352-8486. ; 10:4, s. 906-918
-
Journal article (peer-reviewed)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.
|
|
| 2. |
- Ekberg, Christian, 1967, et al.
(author)
-
Nitride fuel for Gen IV nuclear power systems
- 2018
-
In: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 318:3, s. 1713-1725
-
Research review (peer-reviewed)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.
|
|
| 3. |
- Eriksson, Marcus, et al.
(author)
-
Inherent Safety of Fuels for Accelerator-driven Systems
- 2005
-
In: Nuclear Technology. - 0029-5450 .- 1943-7471. ; 151:3, s. 314-333
-
Journal article (peer-reviewed)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.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Johnson, Kyle D., et al.
(author)
-
Spark plasma sintering and porosity studies of uranium nitride
- 2016
-
In: Journal of Nuclear Materials. - : Elsevier. - 0022-3115 .- 1873-4820. ; 473, s. 13-17
-
Journal article (peer-reviewed)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.
|
|
| 7. |
|
|
| 8. |
- Jolkkonen, Mikael, et al.
(author)
-
Kinetic evidence for different mechanisms of interaction of black mamba toxins MT alpha and MT beta with muscarinic receptors
- 2001
-
In: Toxicon. - 0041-0101 .- 1879-3150. ; 39:2-3, s. 377-382
-
Journal article (peer-reviewed)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.
|
|
| 9. |
|
|
| 10. |
|
|
