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SUNRISE Publications

SUNRISE Mid-term Report


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The SUNRISE centre, established in 2021, is dedicated to preparing for the construction and operation of a Swedish lead-cooled research reactor scheduled start date in 2030. Although the work within SUNRISE itself will not lead to licensing and construction, it is a crucial part of a broader research and development program with substantial commercial impact potential. Collaborating with three universities (KTH, Uppsala, and Luleå) and various industrial stakeholders, the centre operates through five work packages aimed at advancing lead-cooled fast reactor technology in Sweden. Noteworthy achievements include four peer-reviewed publications, the recruitment of 45 individuals (19 seniors and 26 juniors), and successful funding acquisition for the program's second stage through the Solstice project and access to neutron beam facilities at ANSTO in Australia. The centre has also garnered additional funding for local research infrastructure, surpassing the initial SSF award. Impressively, SUNRISE has made a significant societal impact, featuring in numerous popular scientific appearances, including television and radio interviews, news articles, podcasts, a museum exhibition, and a highly successful YouTube channel operated by a SUNRISE PhD student. The centre's visibility and contributions extend beyond academic realms, marking it as a prominent player in both research and public engagement.

Microstructure and magnetization evolution in bcc iron via direct first-principles predictions of radiation effects

Physical Review Materials 7 (2023) 123604

Ebrahim Mansouri, Pär Olsson


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We here model the radiation-induced microstructure evolution in bcc iron using the creation-relaxation algorithm directly driven by density functional theory calculations and compare to interatomic potential simulations. The method is in essence a relatively simplified model without thermally driven diffusion. The microstructure evolution in this model is driven mostly by the stress field introduced by sequential direct damage insertions. The defect populations and the corresponding defect cluster characteristics have been analyzed as a function of irradiation dose. Different distribution functions have been investigated for the self-interstitial atom implantation, to make model predictions as close as possible to actual irradiation conditions under which defects are produced. The stability and magnetic characteristics of the defect structures that are formed are studied. Our first-principles simulations revealed that the C15 structure can be dynamically formed during the irradiation of the material and that the constituent atoms align antiferromagnetically to the lattice. For doses on the order of a fraction of 1 displacement per atom, the model material Fe experiences mechanical changes caused by continuous irradiation and approaches a saturation state of about 2% swelling. The radiation-induced change in the local magnetic moments as well as the charge density differences for some isolated and clustered defects have been investigated. The results revealed a net reduction in total magnetization per atom and a tendency for interstitial sites to have a spin polarization opposing the intrinsic atomic site spins when the coordination number was increased compared to that of the initial lattice structure. It is suggested that radiation-induced damage could be traced using nondestructive measures of bulk magnetization changes. 

Negative effect of bismuth in lead on liquid metal embrittlement of a ferritic steel

Journal of Nuclear Materials 588 (2024) 154829

Christopher Petersson, Peter Szakalos, Rachel Pettersson, Daniel Dietrich Stein


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Liquid metal embrittlement (LME) of a Fe-10Cr-4Al ferritic steel was studied at 375 °C in liquid Pb-Bi alloys. Slow strain rate testing (SSRT) in low oxygen conditions was used to evaluate the ductility as a function of Bi concentration. It was found that susceptibility to LME increased strongly with the Bi concentration. The steel showed a reduction in its total strain to failure, which started at 3–5 wt.% Bi. The alloying elements (Fe, Cr, and Al) have a higher solubility in Bi than pure lead (Pb), so they are expected to dissolve more readily when Bi is added to the Pb. This is believed to be part of the explanation for the observed increase of LME. Lead with up to 3 wt.% Bi induced no LME in the studied corrosion resistance FeCrAl alloy.

WC-Ni cemented carbides prepared from Ni nano-dot coated powders

International Journal of Refractory Metals and Hard Materials 117 (2023) 106375

Paul H. Gruber, Sarmad Naim Katea, Gunnar Westin, Farid Akhtar


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This study presents a novel approach for the synthesis of WC-Ni cemented carbides with enhanced mechanical properties. A low-cost solution-based route was used to coat WC powders with well-distributed metallic nickel dots measuring between 17 nm and 39 nm in diameter. Varying compositions with loadings of 2, 6, and 14 vol% Ni were consolidated using spark plasma sintering (SPS) at 1350 °C under 50 MPa of uniaxial pressure giving relative densities of 99 ± 1 %. The sintered WC-Ni cemented carbides had an even distribution of the Ni binder phase in all compositions, with retained ultrafine WC grain sizes of 0.5 ± 0.1 μm from the starting powder. The enhanced sinterability of the coated powders allowed for consolidation to near theoretical densities, with a binder content as low as 2 vol%. This is attributed to the uniform distribution of nickel and an extensive Ni-WC interface existing prior to sintering. The small size of the Ni dots likely also contributed to the solid-state sintering starting temperatures of as low as 800 °C. The mechanical performance of the resulting cemented carbides was evaluated by measuring the hardness at temperatures between 20 °C and 700 °C and estimating toughness at room temperature using Vickers indentations. These results showed that the mechanical properties of the WC-Ni cemented carbides synthesised by our method were comparable to conventionally prepared WC-Co cemented carbides with similar grain sizes and binder contents and superior to conventionally prepared WC-Ni cemented carbides. In particular, the 2 vol% Ni composition had excellent hardness at room temperature of up to 2210HV10, while still having an indentation fracture toughness of 7 MPa·m0.5. Therefore, WC-Ni cemented carbides processed by this novel approach are a promising alternative to conventional WC-Co cemented carbides for a wide range of applications.

Activation analysis of the lead coolant in SUNRISE-LFR

Nuclear Engineering and Design 414 (2023) 112503

Fredrik Dehlin, Janne Wallenius


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A lumped, zero-dimensional, mass transport model is combined with a depletion matrix solver to study the influence of coolant circulation on radionuclide build-up in a small lead-cooled fast reactor. It is shown that the addition of coolant circulation results in a lower activity for a minority of studied nuclides, and it is thus recommended to consider stagnant coolant when licensing a reactor. Activation analysis of three different lead qualities potentially used in SUNRISE-LFR is performed, and the result shows that a low silver content is desirable to simplify maintenance and decommissioning.

Slow strain rate testing of Fe-10Cr-4Al ferritic steel in liquid lead and lead-bismuth eutectic

Nuclear Materials and Energy 34 (2023) 101403

Christopher Petersson, Peter Szakalos, Daniel Stein


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The susceptibility of Fe-10Cr-4Al steel to liquid metal embrittlement (LME) in low oxygen liquid lead and lead–bismuth eutectic (LBE) environments has been investigated using a newly developed slow strain rate testing (SSRT) technique that can be employed at elevated temperatures. This study showed that the Fe-10Cr-4Al steel suffered embrittlement when exposed to LBE over a wide temperature range. The embrittlement, here measured as a reduction in fracture strain, was observed at the melting temperature of LBE and reached a maximum at approximately 375 °C. At temperatures above 425 °C, the material's ductility regained its original levels. The exposures in liquid lead showed no indications of embrittlement, but a ductile behavior over the entire temperature range studied (340–480 °C).

Potential accident tolerant fuel candidate: Investigation of physical properties of the ternary phase U2CrN3

Journal of Nuclear Materials 568 (2022) 153851

Yulia Mishchenko, Sobhan Patnaik, Elina Charatsidou, Janne Wallenius, Denise Adorno Lopes


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In the present study, physical properties of the ternary phase U2CrN3 are evaluated experimentally and by modeling methods. High density pellets containing the ternary phase were prepared by spark plasma sintering (SPS). The microstructural and crystallographic analyses of the composite pellets were performed using scanning electron microscopy (SEM), standardised energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD). Evaluation of the mechanical properties was performed by nanoindentation test. The impact of temperature on lattice properties was evaluated using high temperature X-ray diffraction (XRD) coupled with modeling. Progressive change in the lattice parameters was obtained from room temperature (RT) to 673 K, and the result was used to calculate average linear thermal expansion coefficients, as well as an input for the density functional theory (DFT) modeling to reassess the degradation of the mechanical properties. The ab-initio calculation provides an initial assessment of electronic configuration of this ternary phase in a direct comparison with one of UN phase. For this goal, modeling was also employed to evaluate point defect formation energies and electronic charge distribution in the ternary phase. Results indicate that the U2CrN3 phase has similar mechanical properties to UN (Young's, bulk, shear moduli, hardness). No preferential crystallographic orientation was observed in the composite pellet. However, charge electron density distribution highlights the significant directionality of chemical bonds, which is in agreement with the anisotropy and non-linear behaviour of the obtained thermal expansion ((aa) = 9.12×10⁻⁶/K, (ab) = 5.81×10⁻⁶/K and (ac) = 6.08×10⁻⁶/K). As a consequence, uranium was found to be more strongly bound in the ternary structure which may delay diffusion and vacancy formation, promising an acceptable performance as nuclear fuel.

An improved correlation for gas release from nitride fuels

Journal of Nuclear Materials 558 (2022) 153402

Janne Wallenius


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An improved correlation for gas release from nitride fuels is elaborated. Introducing empirical activation energies for migration of fission gases in presence of solid fission products and oxide impurities, it becomes possible to better reproduce existing experimental data sets for gas release in sodium and helium bonded rods. The suggested approach may assist in resolving the previously poorly understood dispersion in measured gas release for identical irradiation conditions.

An analytic approach to the design of passively safe lead-cooled reactors

Annals of Nuclear Energy 169 (2022) 108971

Fredrik Dehlin, Janne Wallenius, Sara Bortot


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A methodology to assist the design of liquid metal reactors, passively cooled by natural circulation during off-normal conditions, is derived from first principle physics. Based on this methodology, a preliminary design of a small LFR is accomplished and presented with accompanying neutronic and reactor dynamic characterizations. The benefit of using this methodology for reactor design compared to other available methods is discussed.

Page responsible:Elina Charatsidou
Belongs to: Nuclear Engineering
Last changed: Feb 06, 2024