Evalvacija metod za kalibracijo moči velikih tokamakov

Fusion reactors based on the fusion of deuterium (D) and tritium (T) emit large amounts of 14 MeV neutrons. As exactly one neutron is emitted per such fusion reaction, neutron yield measurements are the most direct way for the determination of the released energy. Accurate measurements of neutron output will be important in fusion power plants for the determination of a reactor’s power output, tritium accountability in the system, the assessment of neutron damage of components, and for the assessments of the dose rates in the humanaccessible parts of the machine. Additionally, reliable information on a reactor’s neutron emission is important for fusion plasma analyses. The dissertation consists of an introduction and three chapters describing the author’s work related to the calibration of neutron yield detectors at Joint European Torus (JET). Whereas most of the work was performed for the DD and DT calibrations of the tokamak JET, the lessons learned are relevant for other machines as well. The focus of the work are thus the calculations performed in support of the absolute calibrations of the neutron detectors in large fusion reactors. The details of the neutron source properties of the neutron generator used in the calibration of JET’s neutron detectors to 14 MeV neutrons were simulated. This neutron source description of the neutron generator was then used in calculations in support of the calibration experiments. Together with measurements, these calculations resulted in the calibration factors for JET’s main neutron detectors. Additionally, the use of a newly released variance reduction tool ADVANTG was tested for the speed-up of the simulations of the fission chamber responses in JET-relevant geometry. These analyses showed that the computational intensity of these simulations can be significantly reduced. The author’s main contributions presented in this dissertation are the detailed reproduction of the neutron emission properties of a neutron generator, computational quantification of corrections applied to the measured calibration factors, and one of the first independent tests of the ADVANTG code on the model of the tokamak.Fuzijski reaktorji, ki delujejo na osnovi zlivanja jeder devterija (D) in tritija (T), sprostijo velike količine nevtronov z energijo 14 MeV. Pri vsaki reakciji zlivanja devterija in tritija se sprosti en nevtron, zato so meritve števila sproščenih nevtronov, oziroma meritve pridelka nevtronov, najbolj neposreden način za merjenje sproščene energije. V bodočih fuzijskih elektrarnah bodo meritve izseva nevtronov pomembne za meritve fuzijske moči med obratovanjem, spremljanje in nadzor količine tritija v sistemu, ocene poškodb komponent kot posledice interakcije z nevtroni ter ocene hitrosti doz v delih naprave, kjer je predviden dostop delavcev. Poleg tega je natančno poznavanje nevtronskega izseva pomembno tudi pri analizi fuzijske plazme. Disertacija vsebuje uvod v problematiko in tri poglavja, ki opisujejo avtorjevo delo povezano s kalibracijo detektorjev nevtronov tokamaka JET. Čeprav je bila večina dela opravljenega v podporo kalibraciji detektorjev nevtronov tokamaka JET na nevtrone sproščene v DD in DT fuzijskih reakcijah, so rezultati in izkušnje relevantne tudi za druge velike fuzijske reaktorje. Delo se tako osredotoča na izračune v podporo kalibracijam detektorjev nevtronov velikih fuzijskih naprav. Predstavljeno je simuliranje produkcije nevtronov v generatorju DT nevtronov, izračuni v podporo kalibracijskim eksperimentom in testiranje relativno novega programa ADVANTG za pospeševanje simulacij Monte Carlo na geometrijah relevantnih za JET, ki lahko bistveno zmanjša računsko zahtevnost simulacij v podporo kalibraciji detektorjev nevtronov. Avtorjevi glavni prispevki, predstavljeni v disertaciji, pa so reprodukcija lastnosti generatorja nevtronov v nevtronskih simulacijah, računska kvantifikacija popravkov izmerjenih kalibracijskih faktorjev in eno od prvih neodvisnih testiranj programa ADVANTG na modelu tokamaka

Modelling of the neutron production in a mixed beam DT neutron generator

Peer reviewe

ASUSD nuclear data sensitivity and uncertainty program package: Validation on fusion and fission benchmark experiments

Nuclear data (ND) sensitivity and uncertainty (S/U) quantification in shielding applications is performed using deterministic and probabilistic approaches. In this paper the validation of the newly developed deterministic program package ASUSD (ADVANTG + SUSD3D) is presented. ASUSD was developed with the aim of automating the process of ND S/U while retaining the computational efficiency of the deterministic approach to ND S/U analysis. The paper includes a detailed description of each of the programs contained within ASUSD, the computational workflow and validation results.ASUSD was validated on two shielding benchmark experiments from the Shielding Integral Benchmark Archive and Database (SINBAD) - the fission relevant ASPIS Iron 88 experiment and the fusion relevant Frascati Neutron Generator (FNG) Helium Cooled Pebble Bed (HCPB) Test Blanket Module (TBM) mock-up experiment. The validation process was performed in two stages. Firstly, the Denovo discrete ordinates transport solver was validated as a standalone solver. Secondly, the ASUSD program package as a whole was validated as a ND S/U analysis tool. Both stages of the validation process yielded excellent results, with a maximum difference of 17% in final uncertainties due to ND between ASUSD and the stochastic ND S/U approach. Based on these results, ASUSD has proven to be a user friendly and computationally efficient tool for deterministic ND S/U analysis of shielding geometries

Detailed reproduction of the neutron emission from the compact DT neutron generator used as an in-situ 14 MeV calibration neutron source at JET

A compact DT neutron generator (NG) based on the mixed-beam operation was used as a calibration neutron source in the latest in-situ calibration of neutron detectors at the Joint European Torus (JET). In order to meet the requirement for the total uncertainty of the neutron detector calibration below ±10 %, the neutron emission properties had to be experimentally characterized and reproduced through detailed modelling of the neutron source characteristics and geometry of the neutron generator. The detailed neutronics simulations were an essential part of both NG characterization and JET neutron detector calibration. The complex neutron emission properties of the NG were reproduced through a combination of simulations and highresolution neutron spectroscopy measurements. This meant that six different DT neutron source components resulting from NG's mixed beam operation were explicitly simulated and their relative intensities scaled based on experimentally obtained neutron spectrum measurements. Furthermore, the detailed model of the NG's geometry was produced based on information from the supplier of the NG and images from a computer tomography (CT) scan. Finally, the positioning of the neutron source inside the JET tokamak during in-situ calibration was reproduced based on the information from the remote handling system (RHS) at JET, the system responsible for the positioning of the source during the calibration experiment. The extensive effort presented in the paper significantly contributed to the total uncertainties of the calibration factors well within the target value of ±10 %

Detailed reproduction of the neutron emission from the compact DT neutron generator used as an in-situ 14 MeV calibration neutron source at JET

A compact DT neutron generator (NG) based on the mixed-beam operation was used as a calibration neutron source in the latest in-situ calibration of neutron detectors at the Joint European Torus (JET). In order to meet the requirement for the total uncertainty of the neutron detector calibration below ±10 %, the neutron emission properties had to be experimentally characterized and reproduced through detailed modelling of the neutron source characteristics and geometry of the neutron generator. The detailed neutronics simulations were an essential part of both NG characterization and JET neutron detector calibration. The complex neutron emission properties of the NG were reproduced through a combination of simulations and highresolution neutron spectroscopy measurements. This meant that six different DT neutron source components resulting from NG's mixed beam operation were explicitly simulated and their relative intensities scaled based on experimentally obtained neutron spectrum measurements. Furthermore, the detailed model of the NG's geometry was produced based on information from the supplier of the NG and images from a computer tomography (CT) scan. Finally, the positioning of the neutron source inside the JET tokamak during in-situ calibration was reproduced based on the information from the remote handling system (RHS) at JET, the system responsible for the positioning of the source during the calibration experiment. The extensive effort presented in the paper significantly contributed to the total uncertainties of the calibration factors well within the target value of ±10 %

EU DEMO EC equatorial launcher pre-conceptual performance studies

The preliminary conceptual design for the Electron Cyclotron (EC) system of the future European DEMOnstration fusion power plant is ongoing in the EUROfusion Consortium. This represents one of the key aspects in order to assess the performances and the integration capabilities of such a system in EU DEMO as well as in the alternative reactor configuration Flexi-DEMO. Different options for the antenna, namely remote steering antenna (RSA), open ended waveguides (OEWG) and the front steering antenna (FSA) later on renamed in mid steering antenna (MSA) to notify that the MSA is protected behind the breeding blanket (BB) in DEMO, are investigated, analyzing their performance for several injection angles and launch points. This activity considers the constraints given by physics and engineering requirements, as for example the maximum power per port and the necessary local current drive to stabilize neo-classical tearing modes (NTMs) with a proper deposition width. The beam tracing calculations have been performed on different scenarios, providing information on plasma accessibility and deposited power. The microwave design and initial ideas about the ex-vessel EC transmission lines routing will be shown