Arkady Serikov

Critical design issues of the ITER ECH front steering upper launcher

Abstract The front steering (FS) launcher is one of two concepts that have been considered for the ITER electron cyclotron heating upper launcher by the European Union. During the development of a detailed conceptual design, the team involved with the FS launcher project listed all of the critical issues associated with installing an FS launcher in the ITER upper port, and then work was concentrated on providing a solution to each of the critical design issues. A similar procedure was performed for the alternative launcher option (remote steering launcher). These actions helped the ITER International Team evaluate the two systems and then choose a final optimum launcher. This evaluation occurred at the end of 2005, with both systems having equivalent reliability, but the FS offered significant enhancement in the physics performance. These differences led ITER-IT to select the FS launcher as the reference design. The goal of this paper is to provide a generalized review of the critical design issues and their solutions as they pertain to the FS launcher. In addition, the overall design and performance of the FS launcher is given along with a brief description of an extended performance launcher design that relaxes the engineering constraints, while increasing the physics capabilities.

Radiation Shielding Analyses for the ITER Upper Port ECRH Launcher

Abstract The International Thermonuclear Experimental Reactor (ITER) will use an electron cyclotron resonance heating (ECRH) system in the upper port of the device for plasma stabilization, heating, and current drive by injecting millimeter wave beams into the plasma chamber. The millimeter waves are transmitted to the plasma through long and narrow waveguide channels. The required plasma wall openings could result in enhanced neutron radiation loadings to the ECRH launcher and neighboring reactor components. The analyses aimed at proving that the shielding requirements and all related nuclear design limits specified by ITER can be met for the proposed ECRH launcher design concepts. The nuclear criteria included human safety issues, nuclear waste regulation aspects, and radiation shielding requirements. The proof was conducted by calculating the radiation loads to sensitive components such as the diamond window of the ECRH launcher, the vacuum vessel, and the superconducting magnets and assessing the potential radiation doses to work personnel during shutdown periods. Dedicated computational approaches were developed to handle the related neutron streaming and shielding problems on the basis of three-dimensional Monte Carlo calculations by the MCNP code. Suitable MCNP models of the launcher were generated by the automatic conversion of the underlying computer assisted design models using a newly developed interface program. The results of the analyses show that all radiation design limits can be safely met for the considered launcher and shield designs.

Nuclear-Safety-Related and Shielding Analyses of the ITER Quasi-Optical ECH Launcher

Nuclear-safety-related and shielding analyses were performed for the quasi-optical design of the electron-cyclotron-heating launcher installed in the ITER upper port. The critical nuclear responses, affecting the nuclear safety and technical performance of the launcher and nearby components, were calculated using the MCNP5 3-D radiation transport code. The computer-aided design (CAD) interface program McCad was applied for the conversion of the CAD model into MCNP geometry description. The radiation effects of the launchers halved internal shield were estimated on the chemical-vapor-deposit diamond windows, vacuum vessel, and toroidal field coils. It was revealed that the nuclear-safety requirements were satisfied.

Review and validation of shutdown dose rate estimation techniques for application to iter

Abstract Several methodologies have been developed for the calculation of shut-down dose rates based on the use of the Monte Carlo (MC) technique for particle transport simulations including the rigorous two-step (R2S) approach and its recent R2Smesh extension, the direct one-step (D1S) method which employs one single MC transport simulation both for neutrons and decay gammas, and a rough rule of thumb (RoT) approximation based on neutron flux-to-dose conversion factors. The paper discusses these approaches and their applications to ITER with focus on dose rate estimations for the equatorial Test Blanket and Diagnostic Ports. These applications are complemented by benchmark analyses on shut-down dose rate measurements performed on JET showing the validity of the R2S and D1S approaches.

Preliminary design of the ITER ECH upper launcher

The design of the ITER electron cyclotron launchers recently reached the preliminary design level -the last major step before design finalization. The ITER ECH system contains 24 installed gyrotrons providing a maximum ECH injected power of 20 MW through transmission lines towards the tokamak. There are two EC launcher types both using a front steering mirror; one Equatorial Launcher for plasma heating and four Upper Launchers (UL) for plasma mode stabilization (neoclassical tearing modes and the sawtooth instability). A wide steering angle of the ULs allows to focus on magnetic islands which are expected on the rational magnetic flux surfaces q = 1 (sawtooth instability), q = 3/2 and q = 2 (NTMs).

Neutronic Analyses for the Upper Ports in the Neutral Beam Cell of ITER

Abstract Neutronic analyses have been performed assessing the performance of the new radiation shielding design of the upper ports in the Neutral Beam (NB) cell of ITER. The scope of the work includes neutron and gamma spectra and nuclear heating calculations inside the port, as well as assessments of fluences, nuclear heating, and insulator radiation doses in the superconductive magnets in the vicinity of the upper port. For radiation transport calculations, the MCNP5 code has been applied with the Alite 4.1 standard 3D model of ITER, in which the inner structure of the upper port was converted from the underlying CAD (CATIA) data. The conversion has been accomplished by means of the McCad interface code. To address human safety issues, maps of shutdown dose rates have been produced using the Rigorous 2 Step (R2S) method enhanced with the mesh-tally capability. The mesh-based R2S approach couples the MCNP5 mesh-tallies with the radioactive inventory results calculated with the FISPACT-2007 activation code allowing automated calculations of shutdown doses including transport of decay gammas. All results satisfy the ITER radiation design requirements.

The ITER ECH & CD Upper Launcher: Steps towards final design of the first confinement system

The ITER Electron Cyclotron Heating and Current Drive (ECH&CD) Upper Launcher, whose preliminary design was approved in 2009, is on its way towards the final design. The design work is being done by a consortium of several European research institutes in tight collaboration with F4E. The main focus is the finalization of the design of all components for the First Confinement System (FCS), which forms the vacuum and Tritium barrier. The FCS comprises structural components as well as the external waveguide components in the port cell. Structural components of the FCS include the flange seal, backend frame and closure plate. The external waveguide components include the isolation valve, CVD diamond windows, miter bends and straight waveguides. Because finalizing of the design of these components is directly influenced by the layout of many in-vessel components, the design work includes also further development of the entire launcher. This paper summarizes the most recent status of the design work on the structural components of the launcher FCS, which are the support flange, the socket, the closure plate and feed-throughs for waveguides and cooling pipes. The design work includes the engineering layout of these components in accordance with system requirements, load specifications and Quality and Safety classification. An outline of the overall design of the launcher will be presented. The design progress was based on a set of related analyses, of which particular results are given. Also the integration of the associated mm-wave components, assembly strategies, neutronic aspects and the design of the shielding components will be described.

The ITER EC-H&CD Upper Launcher: FEM analyses of the blanket shield module with respect to surface and nuclear heat loads

In the frame of the new grant signed in November 2011 between Fusion for Energy (F4E) and the ECHUL-CA consortium, the development process of the Electron Cyclotron Heating and Current Drive (EC H&CD) Upper Launcher (UL) in ITER has moved a step towards the final design phase. The Blanket Shield Module (BSM) is a plasma facing component located at the tip of the launcher. The structure consists of a first wall panel (FWP) and a shell both with embedded cooling channels. A flange on the rear part allows the BSM to be connected by bolts to the main frame of the UL. Being a plasma facing component, the BSM is subjected to severe heat loads due to both thermal and nuclear irradiation. The current baseline value of surface heat load during normal plasma operation is 0.5 MW/m2, while the volumetric nuclear heating is responsible for a total generation of about 160 kW. The temperature gradients resulting from the abovementioned heat loads have been assessed by FEM analyses. The temperature distributions are then transferred to a structural model for calculation of the induced thermal stresses. The surface heat load is applied to the FWP as a constant flux. The nuclear loads, instead, were assessed by MCNP calculations and are provided by means of a mesh tally with a grid step of 1 cm. The results have shown that the temperature reaches 260 °C at the FWP and at the flange of the BSM. As a consequence of large temperature gradients, high stresses (in the order of 200 MPa) are also induced at the inner cooling channels of the BSMs structure.

Radiation In-Port Cross-Talks for ITER Port Diagnostics

Abstract This paper emphasizes the need of estimation of the mutual influence, called “cross-talk,” for neutronic analyses of neighboring diagnostics systems shared by the same ITER port. Using examples of several diagnostic systems inserted inside the ITER Equatorial and Upper Port Plugs, we have demonstrated this mutual influence. Cross-talk effects have been shown by examining the radiation environment inside the port plug in terms of neutron energy spectra and Shut-Down Dose Rate (SDDR) inside the Port Interspace (PI) area. In-port cross-talk was investigated for the diagnostic systems deployed in two Equatorial Port Plugs (EPP) #17 and #8, and for the components of Upper Port Plug (UPP) #3. One example of in-port cross-talks is a gamma shadow effect of the Tritium and Deposit Monitor (TDM) shield block, which affects the SDDR inside the PI of EPP#17. Where the gamma radiation originated from the dominant radioactive sources of the irradiated structures of Core-Imaging X-ray Spectrometer (CIXS) is blocked by the TDM shield. Another example is an influence of neutron streaming along the Fast Ion Loss Detector (FILD) channel on the neutron energy spectra calculated in the Tangential Neutron Spectrometer (TNS) in EPP#8. For the example of UPP#3 with Charge eXchange Recombination Spectroscopy (CXRS-core), performed neutronic analysis identified excessive neutron streaming along the CXRS shutter, which must be reduced by further design iterations.

DOSE RATE ANALYSES FOR THE HIGH ENERGY BEAM TRANSPORT SECTION OF IFMIF

Abstract This work presents neutronic analyses to support the layout of the high energy beam transport (HEBT) section of the IFMIF neutron source in the framework of the Broader Approach (BA) EVEDA activities. In the HEBT section, neutron back streaming from the lithium target can cause significant damage to accelerator components and result in their activation. In order to estimate the resulting radiation doses, detailed neutron and photon flux distributions inside the Target Interface Room (TIR) and the Radiation Isolation Room (RIR) during operation are evaluated by using the Monte Carlo code McDeLicious, which is an enhancement to MCNP5. The obtained results show that the major contribution to the TIR dose during operation will come from neutrons streaming from the target through the beam ducts and from secondary photons produced in these parts. It seems to be impossible to use any semiconductor devices inside TIR, while for mechanical devices there should be no problem. The dose after shutdown due to decay gammas was preliminarily estimated for the beam duct at the most activated place in TIR. In order to reduce the shutdown dose rate, the use of a low-Mn-content aluminium alloy is proposed.