Mechanical properties of several newly produced RAFM steels with Tungsten content in the range of 2 wt%

The contribution of ENEA together with Rina-CSM to the Eurofusion programme \u201cWPMAT-Advanced Seels\u201d deals with the development of innovative RAFM steels able to withstand the critical temperatures typical of the different operational environments foreseen for the blanket of the first DEMO reactor. The optimization of the chemical composition and the Thermo Mechanical Treatment for these materials should be done according to the blanket operating temperatures that are related to two possible working conditions: the WCLL-BB (Water Cooled Lead Lithium Breeding Blanket) or the H(D)CLL-BB (Helium (Dual) Cooled Lead Lithium Breeding Blanket). On the one hand the \u201cwater-cooling\u201d option implies a minimum irradiation temperature for the blanket material in the range of 280\u2013350 \ub0C. On the other hand, the \u201chelium-cooled\u201d and the \u201cdual-coolant\u201d solutions imply an operating temperature for the blanket material in the range of 650 \ub0C. Therefore in the first case the target is the improvement of the toughness of the martensitic alloys; whilst concerning the second scenario the target is the development of more creep resistant martensitic steels, suitable to tolerate such a high operating temperature. In both the cases the Tungsten content plays a key role, both in terms of solid solution hardening and influence on the DBTT. Two alloys aimed at fulfilling the specifications for the two DEMO operating conditions, both with increased Tungsten content respect to Eurofer, have been produced and characterized. The mechanical properties of these two alloys are hereby reported and discussed

Grain size reduction strategies on Eurofer

One of the options currently taken into account for the realization of the first DEMO reactor is the "water-cooled blanket". This option implies a minimum irradiation temperature for the blanket material in the range of 280–350 °C. In addition to the DBTT (Ductile to Brittle Transition Temperature) shift due to the DPA (displacement per atom) damage under irradiation, also the issue of the increased embrittlement due to He production must be taken into account. This issue appears even more detrimental and less manageable because the DBBT shift due to the Helium production does not saturate with the dose, as it results from previous works reported in literature. The experimental results and the difference in behaviour between ODS (Oxide Dispersion Strengthened Steels) RAFM (Reduced Activation Ferritic Martensitic) and other FM (Ferritic Martensitic) alloys (EM10, P91) showed that it is possible to improve the resistance to He embrittlement by both intra-granular precipitation of Y-Ti oxides and by decreasing the grain size at the same time. Nevertheless, anyway, the multiplication of the grain boundaries increases the dilution of He on grain surface, delaying the formation of He bubbles on grain boundaries and, therefore, the susceptibility to the He embrittlement. Several grain size reduction strategies have then been investigated on EUROFER both at the austenitization stage, on the PAGS (Prior Austenite Grain Size), and at the tempering stage, on the tempered martensite. The microstructural observations have been carried out by means of SEM (Scanning Electron Microscopy). Also the effect of grain size reduction on the toughness of the material will be taken into account; The DBTTs resulting from impact tests on KLST specimens will be shown. The outcomes of the microstructural observations, as well as the preliminary mechanical characterization (impact tests) will be discussed in this paper. Keywords: EUROFER 97, RAFM steels, Microstructure, Multiple normalization, Asymmetric rolling, Recrystallization, KLS

Development of innovative materials and thermal treatments for DEMO water cooled blanket

One of the options currently taken into account for the realization of the first DEMO reactor is the "water-cooled lanket". This option implies an irradiation temperature for the blanket material in the range of 280–350 °C. Therefore, in light of the under irradiation behaviour of EUROFER, namely of the DBTT shift toward high temperature due to the low irradiation temperature embrittlement, the target of the hereby reported activities is the development of much tougher alloys, to try to tolerate the embrittlement due to the low irradiation temperature. We report in this paper the work done to optimize the toughness of Eurofer 97, increasing the normalizing temperature and maintaining a small grain size using multiple normalizing treatments. We report also the mechanical behaviour of two 9Cr1WTa type alloys, produced and tested with the same aim to find alloys more resistant to embrittlement at low irradiation temperature. Keywords: EUROFER 97, RAFM steels, Microstructure, Heat treatment, Tensile, Charpy, KLS

Development of innovative steels and thermo-mechanical treatments for DEMO high operating temperature blanket options

Among the options currently taken into account for the realization of the first DEMO reactor there are the "helium-cooled" and the "dual coolant" breeding blanket. Therefore the high temperature (650 °C) behavior of the proposed innovative martensitic alloys should be improved, namely the frame of the hereby reported activities is the development of martensitic alloys more resistant to creep, suitable to tolerate such a high operating temperature. In order to improve the high temperature mechanical properties, concerning the alloy design strategies, two alternative routes are proposed; the effect of Nitrogen and Tungsten increase are taken into account as well as the addition of carbo-nitride forming elements, like Vanadium, combined with the "ausforming" thermo-mechanical treatments. Two alloys have been designed and a special thermo-mechanical treatment on Eurofer 97-2 is proposed. The "ausforming" treatment, consisting in a sort of hot-working at a lower temperature with respect to the austenitization one after the austenitization stage, is aimed at the achievement of a beneficial dislocation "pinning" at high temperature due to carbide precipitation. Generally the improvement of tensile properties is associated to the hardening of the steel due to dislocation network and precipitation effects. This hardening is accompanied by a DBTT increase to markedly higher values with respect to Standard Eurofer. The proposed materials should be, in any case, at least room temperature ductile in order to undergo safe manufacturing and assembling processes. Therefore the issue of the DBTT increase has been taken into account by tuning the tempering temperature adequately. The two variations from chemical composition of Eurofer 97 have been casted and the thermo-mechanical treatments have been selected by means of SEM and hardness measurements to tune grain size and precipitation of carbides. The outcomes of the preliminary mechanical characterization (tensile, creep and impact tests) will be discussed in this paper. Keywords: EUROFER 97, RAFM steels, Thermo-mechanical treatment, Ausforming, Tensile, Creep, Charp

Adenosine receptor agonists: Synthesis and binding affinity of 2-(aryl)alkylthioadenosine derivatives

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Therapeutic vulnerability to PARP1,2 inhibition in RB1-mutant osteosarcoma

Loss-of-function mutations in the RB1 tumour suppressor are key drivers in cancer, including osteosarcoma. RB1 loss-of-function compromises genome-maintenance and hence could yield vulnerability to therapeutics targeting such processes. Here we demonstrate selective hypersensitivity to clinically-approved inhibitors of Poly-ADP-Polymerase1,2 inhibitors (PARPi) in RB1-defective cancer cells, including an extended panel of osteosarcoma-derived lines. PARPi treatment results in extensive cell death in RB1-defective backgrounds and prolongs survival of mice carrying human RB1-defective osteosarcoma grafts. PARPi sensitivity is not associated with canonical homologous recombination defect (HRd) signatures that predict PARPi sensitivity in cancers with BRCA1,2 loss, but is accompanied by rapid activation of DNA replication checkpoint signalling, and active DNA replication is a prerequisite for sensitivity. Importantly, sensitivity in backgrounds with natural or engineered RB1 loss surpasses that seen in BRCA-mutated backgrounds where PARPi have established clinical benefit. Our work provides evidence that PARPi sensitivity extends beyond cancers identifiable by HRd and advocates PARP1,2 inhibition as a personalised strategy for RB1-mutated osteosarcoma and other cancers

Test methodologies for determining high temperature material properties of thin walled tubes

This report presents briefly the test methods used, within the in the EERA JPNM Pilot Project TASTE, for defining the tensile and creep material properties relevant to the integrity of nuclear fuel claddings. These properties are challenging to extract from thin walled tubes since the standard test methods use test specimen that require minimum material thicknesses in the order of 10 mm or more. In consequence the thin walled material properties are acquired through a number of testing techniques and evaluation methodologies suitable for the thin walled product form. In this report the different test methods and their data assessment requirements are briefly described. The test methods evaluated here comprises of sub-size (curved specimen) tensile testing (ST) of the cladding tube, micro specimen (dog-bone) tensile testing (MT), Small Punch testing (SP), Segmented Expanding Cone Mandrel tests (SCM), the ring tension (RT) and ring compression (RC) tests and internal pressure testing (IP).JRC.G.I.4-Nuclear Reactor Safety and Emergency Preparednes

Determination of high temperature material properties of 15-15Ti steel by small specimen techniques

This report presents the final results from the round robin test program on thin-walled cladding tubes in the EERA-JPNM pilot project TASTE. The test methods and assessment procedures used for the assessment of 15-15Ti steel are presented in a previous TASTE report 1. In this report the test results from different test types are assessed, compared and evaluated. The collation of results, mainly on tensile properties shows good agreement between tests methods. An open question remains if there is some anisotropy between the axial and the hoop direction of the tubes. Results from ring tension indicate lower strength values than the test performed in the axial direction. However, the ring tension calculated estimates do not take bending and friction into account. Tensile strength estimates from miniature Small punch tests samples (3 mm in diameter and 0.25 mm thick) indicate no anisotropy whereas tests on the full wall thickness (0.45 mm) with larger puncher balls indicate a reduction towards the INR measured tensile strength (Ring Tension) in the hoop direction. The ring compression test estimates based on calibration at room temperature by ENEA showed surprisingly good performance in estimating the tensile strength at higher temperatures despite the complex stress distribution for this type of test. The few tests performed for determining creep properties, i.e. small punch creep tests, were not successful in describing the expected creep properties. The SPC specimen (as was the case for some SP "tensile test") showed premature cracking at a very early stage of the test for the cold worked material. As a whole it seems that the different types of tests complement each other and together gives an overall picture of the strength and ductility of the tube material. The classical tests such as the ring compression test and the ring tension test gave good estimates on the hoop strength whereas the small punch tests seemingly give an estimate for the weaker direction.JRC.G.I.4-Nuclear Reactor Safety and Emergency Preparednes