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The interaction between cooling fluid and solid structures (rods, tubes) in nuclear power plants may lead to flow-induced vibrations (FIV), causing material fatigue, fretting wear, and eventually loss of component integrity. This can cause further safety issues as well as substantial standstill costs due to longer or unplanned outages. With the growing computational power, the application of modern 3D numerical simulation tools for the accurate prediction of FIV phenomena is rapidly increasing. In 2022, the GO-VIKING (Gathering expertise On Vibration ImpaKt In Nuclear power Generation) project received a grant within the Horizon Europe research and innovation funding program. Sixteen European and two US partners started their collaboration in the field of FIV experiments and analysis. Over four years, the GO-VIKING project investigates FIV phenomena occurring in nuclear reactor cores and steam generators under single- and two-phase flow conditions. The project’s main objectives are to expand the expertise in the field of FIV through generation of new experimental and high-resolution numerical data; development, improvement, and validation of fluid-structure interaction (FSI) methods for FIV evaluation; training stakeholders in the application of these methods; and synthesizing guidelines for the prediction and assessment of FIV phenomena in nuclear reactors. This paper provides an overview of the GO-VIKING objectives, scientific program, as well as of the main scientific achievements in the first project year.

AbstractThe thermal-hydraulic challenges of a nuclear reactor are numerous and mastering them is crucial for the design and safety of new reactors. Numerical simulation through computational fluid dynamics (CFD) codes or system thermal-hydraulic codes can address a lot of the different questions, nevertheless the use of water modeling for the study of the thermal-hydraulic behavior of a new primary system and the validation of codes remains an extremely valuable tool. A water model of the pool-type PbBi-cooled MYRRHA reactor has been developed at the von Karman Institute in collaboration with SCK•CEN. It is a full plexiglass model at a geometrical scale 1/5 of MYRRHA. This transparent water model allows the application of optical measurement techniques like particle image velocimetry (PIV) for flow characterization. Local results of PIV measurements performed in the lower plenum at the entrance of the core are presented and compared with CFD results for nominal operating condition and a natural convection case simulating decay heat removal. Very good agreement has been found in the velocity field. The results also show the importance of the radial flow entering the core of the water model in natural convection.

AbstractThe Belgian Nuclear Research Centre (SCK•CEN) is at the forefront of heavy liquid-metal (HLM) nuclear technology worldwide with the development of the Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA) accelerator-driven system. MYRRHA is a flexible fast-spectrum pool-type research reactor cooled by lead bismuth eutectic (LBE) and has been identified as the European Technology Pilot Plant for the lead-cooled fast reactor. Given the innovative nature of MYRRHA, the project is currently going through a prelicensing phase. The MYRRHA research and development (R&D) program is driven by this prelicensing process and aims to fill the existing gaps in knowledge with respect to LBE chemistry, material behavior, fuel behavior, instrumentation, and HLM thermal hydraulics. In this critical review we present selected topics from the R&D program on HLM thermal hydraulics that are essential for the design, engineering, and safety analysis of MYRRHA and other HLM-cooled reactors. The topics addressed include turbulent heat transfer in HLM, fuel assembly thermal hydraulics and flow-induced vibrations, control rod hydrodynamics, primary heat exchanger pool and integral system thermal hydraulics, sloshing, and multiphysics modeling.

The production of new steel grades - such as dual phase and TRIP steels - requires improvements to both process and equipment of continuous galvanizing lines. In particular, progress has to be obtained in cooling technology in order to get the desired mechanical properties. This paper presents a study of design parameters allowing the optimization of fast gas multi-jet cooling systems. The thermal study involves the application of infrared thermography and three-dimensional numerical simulations. Furthermore, a dynamic study is performed in order to reduce steel strip vibration.

The production of new steel grades - such as dual phase and TRIP steels - requires improvements to both process and equipment of continuous galvanizing lines. In particular, progress has to be obtained in cooling technology in order to get the desired mechanical properties. This paper presents a study of design parameters allowing the optimization of fast gas multi-jet cooling systems. The thermal study involves the application of infrared thermography and three-dimensional numerical simulations. Furthermore, a dynamic study is performed in order to reduce steel strip vibration.

The increasing interest in Small Air Transportation (SAT), to enhance global connectivity, is highlighting the need for reducing take-off distance: lift coefficient has to be increased without penalizing the configuration drag, weight and complexity.

Clones encoding bovine preproelastases I and II were isolated from a pancreatic cDNA library and were sequenced in order to define the structural characteristics of these enzymes. The bovine 947- and 884- nucleotide preproelastase I and II cDNAs encode proteins containing a signal peptide of the same length (16 amino acids), but with a slightly different number of amino acids for the activation peptide (10 and 12, respectively) and the mature enzyme (240 and 241, respectively). Considering amino acid sequences, each enzyme shares a high degree of identity (76–86%) within species. In contrast, only 55.3% identity is found between bovine elastases I and II. This difference could explain partly their own specificity. Analysis of the expression of the elastases in various bovine tissues demonstrated that they are specifically expressed in high levels in the pancreatic gland. These two approaches (structure and expression) allowed us to characterize the bovine pancreatic elastases I and II.

Recombinant human gastric lipase (rHGL) (EC 3.1.1.3) was produced on a large scale (5–13 mg/liter) from recombinant baculovirus-infected insect cells using a bioreactor apparatus. Here an improved procedure is described for purifying rHGL involving the use of cation exchange chromatography followed by immunoaffinity column methods, which gives a total yield of 62% and a purification factor of 464, using 10% isopropanol in all the purification buffers. The presence of isopropanol was necessary to preserve the stability of the enzyme during the chromatographic separation steps. The specific activity of rHGL on tributyroylglycerol (700 U/mg) was lower than that of native HGL (nHGL) (1080 U/mg). The rHGL interfacial adsorption kinetics were studied by recording the changes in the surface pressure with time in the presence or absence of an egg phosphatidycholine monomolecular film spread at the air/water interface at various initial surface pressures. The surface behavior of rHGL was similar to that of nHGL. It can be concluded that the lipid binding affinity of rHGL is identical to that of the native lipase and, consequently, that the presence of detergents and lipids in the insect cell culture media did not affect the interfacial behavior of the purified rHGL. It will be therefore possible to specifically study the binding step of HGL mutants to a lipid monolayer.

The sequence of a rat pancreatic lipase mRNA was determined. The data have been assigned the following accession number, X61925, in the EMBL data library. The total length of the messenger is 1531 nucleotides, plus a poly(A) stretch of about 60 nucleotides. A 72-nucleotides 5′-noncoding region is followed by a 1419-nucleotides open reading frame which encodes a protein of 473 amino acids, including the 17 amino acid signal peptide. The mature enzyme (456 residues) has 6 additional C-terminal amino acids, as compared with the amino acid sequence of pig (direct amino acid sequence), dog, man and rat isoenzyme from Genbank, M58369 (all deduced from the nucleotide sequence). A higher degree of homology exists between the amino acid sequence of rat mature enzyme with those of dog (88%), pig (75%) and man (75%) than with that of rat isolipase (74%).

In order to characterize the biological functions coupled to cholecystokinin (CCK) A and B receptors, the effects of gastrin(2-17 ds) and caerulein were compared. An isolated cell model, the pancreatic acinar cell line AR4-2J, was used and the experiments were carried out in serum-free media. Caerulein was found to evoke no mitogenic effects either alone or in the presence of the CCK antagonists L364,718 and CR1409. Gastrin(2-17 ds) increased cell proliferation by 2-fold with an IC50 of 150 pM, corresponding to the occupancy of the CCK B receptors. CR1409, at concentrations that fully occupied CCK B receptors, inhibited the gastrin(2-17 ds) effects. Caerulein enhanced chymotrypsinogen biosynthesis by 100% and the corresponding mRNA level by 75%; amylase biosynthesis and mRNA level were enhanced by 40% only. Half-maximal increases in chymotrypsin activity and mRNA level were recorded in response to caerulein at concentrations of 100 pM and 50 pM respectively. Gastrin(2-17 ds) at 100 nM enhanced chymotrypsinogen biosynthesis by 26% and its mRNA level by 35%; these responses were lower than those evoked by 0.1 nM caerulein. Furthermore, CR1409 completely inhibited caerulein- and gastrin(2-17 ds)-stimulated chymotrypsinogen synthesis, with similar IC50 (4 microM). These results suggest that both peptides induced the synthesis of the secretory enzyme after occupancy of CCK A receptors.

The direct effects of dexamethasone and caerulein on two pancreatic enzymes, amylase and chymotrypsin, were determined in AR4-2J cells cultured under serum-free conditions at two glucose concentrations (1.0 and 4.5 g/l). In the absence of any hormone, the higher glucose concentration resulted in a 1.6-1.8-fold increase in the basal levels of amylase and chymotrypsinogen. Dexamethasone (50 nM) increased the biosynthesis and mRNA levels of both enzymes at both glucose concentrations. However, dexamethasone had a more pronounced effect on amylase biosynthesis (5-fold induction) than on chymotrypsinogen biosynthesis (1.8-fold induction). The parallel increases in mRNA and protein indicated the existence of pre-translational regulation. This is in contrast with what was observed in serum-containing media, where a translational regulation of amylase biosynthesis took place, probably under the control of both glucose and some serum factors. By contrast, caerulein (10 nM) exerted a more specific action on chymotrypsinogen. The increases in chymotrypsinogen mRNA were 2.2- and 2.1-fold, and increases in chymotrypsin activity were 1.6- and 2.9-fold at 1.0 and 4.5 g of glucose/litre respectively. Thus the regulation by caerulein occurred mainly through the enhancement of chymotrypsinogen transcription and/or mRNA stabilization.

The sequence of a rat pancreatic lipase mRNA was determined. The data have been assigned the following accession number, X61925, in the EMBL data library. The total length of the messenger is 1531 nucleotides, plus a poly(A) stretch of about 60 nucleotides. A 72‐nucleotides 5′‐noncoding region is followed by a 1419‐nucleotides open reading frame which encodes a protein of 473 amino acids, including the 17 amino acid signal peptide. The mature enzyme (456 residues) has 6 additional C‐terminal amino acids, as compared with the amino acid sequence of pig (direct amino acid sequence), dog, man and rat isoenzyme from Genbank, M58369 (all deduced from the nucleotide sequence). A higher degree of homology exists between the amino acid sequence of rat mature enzyme with those of dog (88%), pig (75%) and man (75%) than with that of rat isolipase (74%).

Using polyclonal antibodies raised against human pancreatic procarboxypeptidases, a full-length cDNA coding for an A-type proenzyme was isolated from a lambda gt11 human pancreatic library. This cDNA contains standard 3′ and 5′ flanking regions, a poly(A)+ tail and a central region of 1260 nucleotides coding for a protein of 419 amino acids. On the basis of sequence comparisons, the human protein was classified as a procarboxypeptidase A1 which is very similar to the previously described A1 forms from rat and bovine pancreatic glands. The presence of the amino acid sequences assumed to be of importance for the zymogen inhibition by its activation segment, primarily on the basis of the recently reported crystal structure of the B form, further supports the proposed classification.

Changes in the activities of three gastric and nine pancreatic enzymes plus colipase were determined during postnatal development and weaning in calves. In calves exclusively milk-fed for 2, 7, 28, 56, 70 and 119 d, the enzyme activities per kilogram of empty live weight increased with age for chymotrypsin, elastase, carboxypeptidases A and B, ribonuclease and α-amylase, decreased for chymosin, lysozyme and colipase but showed no change in the case of pepsin, trypsin, lipase and phospholipase A2 compared with animals at birth. The greatest increase was that in α-amylase activity (about 50-fold between d 2 and 119). In calves weaned between d 28 and 56, all the activities were higher than in milk-fed animals, except that of chymosin (which was slightly lower) and that of colipase (which did not change). At 119 d of age, chymotrypsin, carboxypeptidase A, α-amylase and lipase were 1.6- to fourfold higher in ruminants than in preruminants. Thus, most enzyme activities were modified first by colostrum and milk intake, and again upon weaning by development of the forestomachs and ingestion of solid food. These ontogenic patterns might be under the control of many gut regulatory peptides, the plasma concentrations of which changed simultaneously. Some gastric and pancreatic enzymes were correlated to plasma concentrations of these gut regulatory peptides.