Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Analysis of an Ex-Vessel Break in the ITER Divertor Cooling Loop

In the present work the integrated ECART code, developed for severe accident analysis in LWRs, is applied on the analysis of a large ex-vessel break in the divertor cooling loop of the international thermonuclear experimental reactor (ITER).Acomparison of the ECART results with those obtained by Studsvik Nuclear AB (S), utilizing the MELCOR code, was also performed in the general framework of the quality assurance program for the ITER accident analyses. This comparison gives a good agreement in the results, both for thermal-hydraulics and the environmental radioactive releases. Mainly these analyses, from the point of view of the ITER safety, confirm that the accidental overpressure inside the vacuum vessel and theTokamak coolingwater system (TWCS) Vault is always well below the design limits and that the radioactive releases are adequately confined below the ITER guidelines

Validation of the ECART code for the safety analysis of fusion reactors

Realistic calculation of the radiotoxic substances transport within a fusion facility requires a coupling among thermal–hydraulic, chemistry and aerosol-vapour models. The paper introduces the methodology adopted for the simulation of these phenomena with ECART, a code developed by a pool of Italian institutions with the support of European Union and EDF. In the past, this tool was successfully validated against the major source term tests applied to Light Water Reactor (LWR) safety and it is now employed in investigations about advanced LWRs and non-nuclear risk studies. It also contains information about chemical compounds involved in fusion reactor safety and simulates the related oxidation reactions. With regard to its application on fusion, a large validation activity was performed, mainly based on the analyses of experimental programs promoted inside the EURATOM Fusion Technology Programme. The correct simulation of main phenomena occurring in ICE and STARDUST facilities demonstrates the applicability of ECART in performing a realistic prediction of the whole sequence (thermal–hydraulics and dust transport) inside fusion plants

Analysis of the ICE Experimental Tests Using the ECART Code

In the present paper the work performed to validate the ENEL/EDF ECART code on the base of a series of experimental tests performed in the Japanese ICE facility is presented. This activity has been carried out in the general framework of the validation phase of the ECART code, initially developed for integrated analysis of severe accidents in LWRs, for its application on incidental sequences related to fusion plants. The ICE facility consists of the cylindrical vacuum vessel, at horizontal axis (900. mm of external diameter and 600. mm length), the boiler, the blow-down tank and the corresponding piping and valves. The vessel has heat plates to maintain the required wall temperatures and initially contains dry air at a sub-atmospheric pressure of about 100. Pa. The employed ECART code full-couples the aerosol-vapour transport phenomena with thermal-hydraulics and chemical equilibrium. For the present work purposes, due to the ICE tests characteristics, only the thermal-hydraulic code section was activated and the dry aerosol or the chemical equilibrium modules were not employed. Two different conclusions have been highlighted by the work. The first one, being the main goal of the work, is related to the assessment of the ECART code in experimental conditions relevant for the future fusion reactors, against the traditional LWRs assessment previously performed for this code. The second one is related to the evaluation of the ICE experimental tests

Simulation of cryogenic tests with steam or water and incondensable gas injection in vessels

The paper presents the results obtained by the CONSEN computer program for two post-test calculations of the EVITA facility (CEA) relating to the cryogenic experiments carried out in 2004 and 2005. EVITA experiment has the scope to test the cryogenic effects in case of water or steam inlet together with helium gas in volumes having initial vacuum conditions. It simulates the cryostat behaviour in the ITER plant during a loss of coolant accident due to the simultaneous ruptures of water and helium cooling pipes. The ice formation phenomenon is investigated. In the past years, several pre- and post- test analyses were carried out. A new model to evaluate ice porosity during formation and its influence on density and thermal conductivity has been implemented and is under testing in CONSEN 5.1. Some modifications in the iterative algorithms for the ice thickness evaluation and corrections have been introduced with respect to the previous CONSEN version. The comparison with the experimental data has been performed and the main agreement and differences remarked. The new version 5.1 of the CONSEN code has now been implemented to carry on post-test calculations, with satisfactory results