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| 2. |
- Charpin, Laurent, et al.
(författare)
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Ageing and air leakage assessment of a nuclear reactor containment mock-up : VERCORS 2nd benchmark
- 2021
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Ingår i: Nuclear Engineering and Design. - : Elsevier BV. - 0029-5493. ; 377
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Tidskriftsartikel (refereegranskat)abstract
- Electricité de France (EDF) operates a large fleet of nuclear reactors and is responsible for demonstrating the safety of facilities, including concrete containment buildings (CCB), which are non-replaceable components. The leak-tightness of CCBs is assessed every 10 years during integrated leak-rate tests (IRLT). For double-wall containments, which have no metallic liners, the leak-tightness is strongly influenced by the degree of cracking of concrete and opening of the cracks, which mostly depends on (a) the prestress decrease due to the delayed strains of concrete and to a lesser extent due to relaxation of tendons steel, and (b) the saturation degree of the Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation concrete wall. Therefore, to optimize the maintenance programs on CCBs, it is important to predict the evolution of drying, creep and shrinkage strains of concrete to be able to correctly assess the pre-stress losses, and finally the air leak-tightness at a structural level during pressure tests or under accidental loadings. To improve our understanding and identify the best modelling practices on this issue, a large experimental program called VERCORS was launched in 2014. VERCORS is a 1/3 mock-up of a 1300 MWe nuclear reactor CCB. It has been widely instrumented, and its concrete thoroughly characterized. A specific attention has been paid to ensure it is consistent with real CBBs features in EDF's nuclear fleet. To complement its internal R&D efforts, EDF decided to associate external partners to this program. One of the means for this is the organization of benchmarks, where all teams are given data and information about the mock-up and are asked to quantitatively predict its behaviour. The present paper reports the organization and findings of the 2nd benchmark which was organized in 2018 and gathered several international teams around the same objective: improve the confidence in the modelling of structural behaviour as well as the leak-tightness of concrete in containment walls under pressure test loading. The benchmark has shown once again that predicting the mechanical and leakage behaviour of containment buildings is a difficult task. The benchmark also yielded interesting information about the possibility to use spatially reduced models to predict the mechanical behaviour and leakage and underlined the fact that more research must be done to better predict the localization of cracks and leakage. Some lessons have been learnt for the next benchmark: EDF will ask to clarify further the calibration methods, will give more data (including drying, creep and shrinkage at different temperatures and moisture measurements in the mock-up), and will help the participants using local leakage data by projecting the raw measurements on a regular grid, so that the local leakage models can be improved.
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| 3. |
- Dherbecourt, Jean Baptiste, et al.
(författare)
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Injection-Free and Cavity Free Parametric Sources for Future Spaceborne DIAL Based on Periodically Poled Nonlinear Materials
- 2024
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Ingår i: Springer Aerospace Technology. - : Springer Nature. ; , s. 363-371
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We present new parametric source architectures for future spaceborne Differential Absorption Lidar (DIAL). This work focalizes on the developments performed during LEMON H2020 project using periodically poled nonlinear crystals. Such phase matching configuration offers the possibility to go towards more simple and robust set-ups for future space operation. We investigated injection-free optical parametric oscillator OPO set-ups, such as the Nested Cavity OPO–which allows a broad tuning range and thus can address several gas species with a single OPO—and also propose an injection and cavity free OPO solution using the counter-propagating phase matching configuration (Backward wave OPO). Moreover, we studied the implementation of high efficiency optical parametric amplifiers, to investigate the possibility to scale the output energies to several tens of mJ in the 2 µm region, and performed radiation testing on the specifically developed, large aperture, periodically poled KTP crystals.
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| 4. |
- Mølster, Kjell Martin, 1992-, et al.
(författare)
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Highly efficient, high average power, narrowband, pump-tunable BWOPO
- 2023
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Ingår i: Optics Letters. - : Optica Publishing Group. - 0146-9592 .- 1539-4794. ; 48:24, s. 6484-6487
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a continuously tunable mid-infrared source that produces narrowband radiation at 1981 nm and 2145 nm based on a tunable Yb-based hybrid MOPA pump and a backward-wave optical parametric oscillator (BWOPO). The BWOPO employs a PPRKTP crystal with 580 nm domain periodicity. The BWOPO has a record-low oscillation threshold of 19.2 MW/cm2 and generates mJ level output with an overall efficiency exceeding 70%, reaching an average power of 5.65W at the repetition rate of 5 kHz. The system is mechanically robust and optical cavity-free, making it suitable for spectroscopic systems on mobile platforms. The mid-infrared signal frequency is tuned by pump tuning with a linear pump-to-signal frequency translation rate close to the predicted 1 to 1.001 Hz/Hz.
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| 5. |
- Mølster, Kjell Martin, 1992-, et al.
(författare)
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Low-threshold Highly Efficient Backward Wave OPO
- 2022
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Ingår i: Nonlinear Photonics, NP 2022. - : Optica Publishing Group (formerly OSA).
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Konferensbidrag (refereegranskat)abstract
- Cavity-free, precision-tunable source of a nanosecond, mJ-level, pulses consisting of backward optical parametric oscillator pumped by diode-seeded laser amplifier shows a record threshold of 19 MW/cm2 and an optical-to-optical efficiency exceeding 70%.
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| 7. |
- Mølster, Kjell Martin, 1992-, et al.
(författare)
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Pump Tunable Mirrorless OPO : an Innovative Concept for Future Space IPDA Emitters
- 2023
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Ingår i: International Conference on Space Optics, ICSO 2022. - : SPIE-Intl Soc Optical Eng.
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Konferensbidrag (refereegranskat)abstract
- A highly efficient mirrorless OPO tunable in the mid-infrared around 2 μm has been developed and characterized in an original pumping configuration comprising a tunable high power hybrid Ytterbium laser MOPA (Master Oscillator Power Amplifier) in the nanosecond regime. The hybrid pump laser is based on a fiber laser seeder continuously tunable over several GHz at 1030 nm, which is shaped in the time domain with acousto-optic modulators (AOM), and power amplified in a dual stage Ytterbium doped fiber amplifiers, followed by two Yb:YAG bulk amplifiers. The pump delivers up to 3.5 mJ of energy within narrowband 15 ns pulses with a 5 kHz repetition rate. The output was focused into Periodically Poled KTP (PPKTP) crystals with a quasi-Phase Matching (QPM) period of 580 nm, producing Backward Optical Parametric Oscillation (BWOPO), with a forward signal wave at 1981 nm and a backward traveling idler at 2145 nm. We report significant optical to optical efficiencies exceeding 70 % depending on crystal length and input power. As theoretically expected, the forward wave could be continuously tuned over 10 GHz following the pump frequency sweep, while the backward wave remains almost stable, both being free from mode hops. These properties obtained from an optical arrangement without free-space cavities are attractive for future space Integrated Path Differential Absorption (IPDA) Lidar applications, which require robust and efficient tunable frequency converters in the mid-infrared.
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