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Luzzi Sabino,Gragnaniello Cristian,Marasco Stefano,Lucifero Alice Giotta,Del Maestro Mattia,Bellantoni Giuseppe,Galzio Renato 대한척추외과학회 2021 Asian Spine Journal Vol.15 No.3
Extrinsic compression of the subaxial vertebral artery (VA) may cause rotational occlusion syndrome (ROS) and contribute to vertebrobasilar insufficiency potentially leading to symptoms and in severe cases, to posterior circulation strokes. The present literature review aimed to report the main clinical findings, diagnostic work-up, and surgical management of the subaxial VA-ROS, the diagnosis of which can be difficult and is often underestimated. An illustrative case is also presented. A thorough literature search was conducted to retrieve manuscripts that have discussed the etiology, diagnosis, and treatment of ROS. Total 41 articles were selected based on the best match and relevance and mainly involved case reports and small cases series. The male/female ratio and average age were 2.6 and 55.6±11 years, respectively. Dizziness, visual disturbances, and syncope were the most frequent symptoms in order of frequency, while C5 and C6 were the most affected levels. Osteophytes were the cause in >46.2% of cases. Dynamic VA catheter-based angiography was the gold standard for diagnosis along with computed tomography angiography. Except in older patients and those with prohibitive comorbidities, anterior decompressive surgery was always performed, mostly with complete recovery, and zero morbidity and mortality. A careful neurological evaluation and dynamic angiographic studies are crucial for the diagnosis of subaxial VA-ROS. Anterior decompression of the VA is the cure of this syndrome in almost all cases.
Luzzi, L.,Barani, T.,Boer, B.,Cognini, L.,Nevo, A. Del,Lainet, M.,Lemehov, S.,Magni, A.,Marelle, V.,Michel, B.,Pizzocri, D.,Schubert, A.,Uffelen, P. Van,Bertolus, M. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.10
The design phase and safety assessment of Generation IV liquid metal-cooled fast reactors calls for the improvement of fuel pin performance codes, in particular the enhancement of their predictive capabilities towards uranium-plutonium mixed oxide fuels and stainless-steel cladding under irradiation in fast reactor environments. To this end, the current capabilities of fuel performance codes must be critically assessed against experimental data from available irradiation experiments. This work is devoted to the assessment of three European fuel performance codes, namely GERMINAL, MACROS and TRANSURANUS, against the irradiation of two fuel pins selected from the SUPERFACT-1 experimental campaign. The pins are characterized by a low enrichment (~ 2 wt.%) of minor actinides (neptunium and americium) in the fuel, and by plutonium content and cladding material in line with design choices envisaged for liquid metal-cooled Generation IV reactor fuels. The predictions of the codes are compared to several experimental measurements, allowing the identification of the current code capabilities in predicting fuel restructuring, cladding deformation, redistribution of actinides and volatile fission products. The integral assessment against experimental data is complemented by a code-to-code benchmark focused on the evolution of quantities of engineering interest over time. The benchmark analysis points out the differences in the code predictions of fuel central temperature, fuel-cladding gap width, cladding outer radius, pin internal pressure and fission gas release and suggests potential modelling development paths towards an improved description of the fuel pin behaviour in fast reactor irradiation conditions.
L. Luzzi,T. Barani,B. Boer,A. Del Nevo,M. Lainet,S. Lemehov,A. Magni,V. Marelle,B. Michel,D. Pizzocri,A. Schubert,P. Van Uffelen,M. Bertolus 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.3
Design and safety assessment of fuel pins for application in innovative Generation IV fast reactors calls for a dedicated nuclear fuel modelling and for the extension of the fuel performance code capabilities to the envisaged materials and irradiation conditions. In the INSPYRE Project, comprehensive and physicsbased models for the thermal-mechanical properties of UePu mixed-oxide (MOX) fuels and for fission gas behaviour were developed and implemented in the European fuel performance codes GERMINAL, MACROS and TRANSURANUS. As a follow-up to the assessment of the reference code versions (“pre- INSPYRE”, NET 53 (2021) 3367e3378), this work presents the integral validation and benchmark of the code versions extended in INSPYRE (“post-INSPYRE”) against two pins from the SUPERFACT-1 fast reactor irradiation experiment. The post-INSPYRE simulation results are compared to the available integral and local data from post-irradiation examinations, and benchmarked on the evolution during irradiation of quantities of engineering interest (e.g., fuel central temperature, fission gas release). The comparison with the pre-INSPYRE results is reported to evaluate the impact of the novel models on the predicted pin performance. The outcome represents a step forward towards the description of fuel behaviour in fast reactor irradiation conditions, and allows the identification of the main remaining gaps.
Magni A.,Pizzocri D.,Luzzi L.,Lainet M.,Michel B. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.7
The sodium-cooled fast reactor is among the innovative nuclear technologies selected in the framework of the development of Generation IV concepts, allowing the irradiation of uranium-plutonium mixed oxide fuels (MOX). A fundamental step for the safety assessment of MOX-fuelled pins for fast reactor applications is the evaluation, by means of fuel performance codes, of the integral thermal-mechanical behaviour under irradiation, involving the fission gas behaviour and release in the fuel-cladding gap. This work is dedicated to the performance analysis of an inner-core fuel pin representative of the ASTRID sodium-cooled concept design, selected as case study for the benchmark between the GERMINAL and TRANSURANUS fuel performance codes. The focus is on fission gas-related mechanisms and integral outcomes as predicted by means of the SCIANTIX module (allowing the physics-based treatment of inert gas behaviour and release) coupled to both fuel performance codes. The benchmark activity involves the application of both GERMINAL and TRANSURANUS in their “pre-INSPYRE” versions, i.e., adopting the state-of-the-art recommended correlations available in the codes, compared with the “post-INSPYRE” code results, obtained by implementing novel models for MOX fuel properties and phenomena (SCIANTIX included) developed in the framework of the INSPYRE H2020 Project. The SCIANTIX modelling includes the consideration of burst releases of the fission gas stored at the grain boundaries occurring during power transients of shutdown and start-up, whose effect on a fast reactor fuel concept is analysed. A clear need to further extend and validate the SCIANTIX module for application to fast reactor MOX emerges from this work; nevertheless, the GERMINAL-TRANSURANUS benchmark on the ASTRID case study highlights the achieved code capabilities for fast reactor conditions and paves the way towards the proper application of fuel performance codes to safety evaluations on Generation IV reactor concepts.
G. Zullo,D. Pizzocri,L. Luzzi 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.4
Recent developments on spectral diffusion algorithms, i.e., algorithms which exploit the projection of thesolution on the eigenfunctions of the Laplacian operator, demonstrated their effective applicability in fasttransient conditions. Nevertheless, the numerical error introduced by these algorithms, together with theuncertainties associated with model parameters, may impact the reliability of the predictions on shortlived volatile fission product release from nuclear fuel. In this work, we provide an upper bound on thenumerical error introduced by the presented spectral diffusion algorithm, in both constant and timevarying conditions, depending on the number of modes and on the time discretization. The definitionof this upper bound allows introducing a methodology to a priori bound the numerical error on shortlived volatile fission product retention.
M. Romano,D. Pizzocri,L. Luzzi 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.5
Besides recent progresses in the physics-based modelling of fission gas and helium behaviour, thescarcity of experimental data concerning their combined behaviour (i.e., cocktail) hinders further modeldevelopments. For this reason, in this work, we propose a modelling methodology aimed at providingrecommendations for accelerated experimental investigations. By exploring a wide range of annealingtemperatures and cocktail compositions with a physics-based modelling approach we identify the mostinteresting conditions to be targeted by future experiments. To corroborate the recommendations arisingfrom the proposed methodology, we include a sensitivity analysis quantifying the impact of the modelparameters on fission gas and helium release, in conditions representative of high and low burnup
A surrogate model for the helium production rate in fast reactor MOX fuels
Pizzocri D.,Katsampiris M.G.,Luzzi L.,Magni A.,Zullo G. 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8
Helium production in the nuclear fuel matrix during irradiation plays a critical role in the design and performance of Gen-IV reactor fuel, as it represents a life-limiting factor for the operation of fuel pins. In this work, a surrogate model for the helium production rate in fast reactor MOX fuels is developed, targeting its inclusion in engineering tools such as fuel performance codes. This surrogate model is based on synthetic datasets obtained via the SCIANTIX burnup module. Such datasets are generated using Latin hypercube sampling to cover the range of input parameters (e.g., fuel initial composition, fission rate density, and irradiation time) and exploiting the low computation requirement of the burnup module itself. The surrogate model is verified against the SCIANTIX burnup module results for helium production with satisfactory performance
Cognini, L.,Cechet, A.,Barani, T.,Pizzocri, D.,Van Uffelen, P.,Luzzi, L. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.2
In this work, we propose a new mechanistic model for the treatment of helium behaviour which includes the description of helium solubility in oxide fuel. The proposed model has been implemented in SCIANTIX and validated against annealing helium release experiments performed on small doped fuel samples. The overall agreement of the new model with the experimental data is satisfactory, and given the mechanistic formulation of the proposed model, it can be continuously and easily improved by directly including additional phenomena as related experimental data become available.
Zullo G.,Pizzocri D.,Magni A.,Van Uffelen P.,Schubert A.,Luzzi L. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.12
The behaviour of the fission gas plays an important role in the fuel rod performance. In a previous work, we presented a physics-based model describing intra- and inter-granular behaviour of radioactive fission gas. The model was implemented in SCIANTIX, a mesoscale module for fission gas behaviour, and assessed against the CONTACT 1 irradiation experiment. In this work, we present the multi-scale coupling between the TRANSURANUS fuel performance code and SCIANTIX, used as mechanistic module for stable and radioactive fission gas behaviour. We exploit the coupled code version to reproduce two integral irradiation experiments involving standard fuel rod segments in steady-state operation (CONTACT 1) and during successive power transients (HATAC C2). The simulation results demonstrate the predictive capabilities of the code coupling and contribute to the integral validation of the models implemented in SCIANTIX.