Investigation and analysis on ITER in-vessel coils’ raw-materials

The ITER in-vessel coils (IVCs) consist of 27 coils edge localized modes (ELM) and 2 coils vertical stabilization (VS) which are all mounted on the vacuum vessel wall behind the shield modules. The IVCs design and manufacturing work is being conducted in between Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) and Princeton Plasma Physics Laboratory (PPPL). Because the position of ELM and VS coils is close and face to the plasma, the IVCs must undergo a severe environment, such as the high dose of radiation and high operation temperature, thus the conventional electrical insulation materials cannot be used. And the technology of “Stainless Steel Jacketed Mineral Insulated Conductor” (SSMIC) is deemed as the best choice to provide the necessary radiation resistance and compatibility strength in ITER's vacuum vessel. While mineral insulated conductor technology is not new, and is similar to the mineral insulated cable used in industrial. Some difficulties still need to be solved, such as searching for the proper raw-materials to make sure that the conductor have the properties of high current carrying capability, the necessary radiation resistance, the proper strength, at the same time, it must be come true in manufacture technology. This paper described the analysis of the materials for VS and ELM coil conductor.     

HVPTF—The high voltage laboratory for the ITER Neutral Beam test facility

In the MITICA research program for the construction of the ITER Neutral Beam Injector prototype, a Laboratory for the investigation on high voltage holding in vacuum has been set up. This Laboratory - HVPTF: High Voltage Padova Test Facility - is presently capable of experiments up to 300 kV dc, and planned for the upgrade to 800 kV. The specific mission for this ancillary lab is the support to the electrostatic design and construction of the MITICA accelerator and the development and testing of HV components to be installed inside the MITICA accelerator during its operation.The paper describes the structure of the lab, characterized by a high degree of automation and reports the results of the commissioning at 300 kV and the first results of voltage holding between test electrodes.     

Conceptual design of spherical torus with TF–CS hybrid coils based on virial theorem

A conceptual design of a spherical torus (ST) device with a new type of toroidal field (TF) coils and a central solenoid (CS) whose stress is reduced to a theoretical limit determined by the virial theorem is proposed. A virial-limit coil (VLC), which is a helical-type hybrid coil of TF coils and CS, and its winding is modulated so that its winding direction is nearly vertical and more horizontal in the outer and inner sides of torus, respectively. Thus, the configuration of VLC is similar to that of CS and TF coil systems in conventional tokamaks. Recently, we have developed a VLC concept with a non-circular cross-section, and reduce the maximum stress to 30% of that of TF coils in a two-dimensional analysis. Moreover, the VLC configuration is remarkably similar to that of a ST with a low aspect ratio and a strongly elongated cross-section with a triangularity. In this work, we analyze three dimensional stress distributions, and propose a design of VLC ST.     

How accurately can we predict synthesis cross sections of superheavy elements?

Synthesis of superheavy elements beyond oganesson is facing new challenges as new target–projectile combinations are necessary. Guidance from models is thus expected for future experiments. However, hindered fusion models are not well established and predictions in the fission barriers span few MeVs. Consequently, predictions are not reliable. Strategies to constrain both fusion hindrance and fission barriers are necessary to improve the predictive power of the models. But, there is no hope to get an accuracy better than one order of magnitude in fusion–evaporation reactions leading to superheavy elements synthesis.     

When is a crush test not a crush test? or What constitutes a valid crush test?

Abstract

Recent discussions at the international level are elaborated regarding the intent and method for clarifying acceptable package/drop mass orientations for the dynamic crush test that is required for some Type B and some Type A fissile radioactive material packages. Coverage includes part of the discussions that occurred at an International Atomic Energy Agency Consultants Services Meeting convened to discuss this issue in September 2008.     

Strain Measurement on the Toroidal Field （TF） Coil Cases

The stress-strain state of the structure is a matter of interest to designer. The strain measurement of superconducting magnets at cryogenic temperature is a specific technique. Based on strain measurement of TF coil case for EAST, this paper presents a measuring technique at cryogenic temperature and on intense magnetic field. The compensation methods for both temperature and magnetic field effects of the gauges, together with the measured results are involved, and the discussions of the measured results are given in the paper.     

Towards the development of technical specifications for the production of lithium–lead alloys for the ITER HCLL TMB

The ITER and DEMO projects are developing new Test Blanket Modules (TBM), where the Pb–Li alloy plays a key role in the new commercial fusion reactors functionality. The Breeding Blanket (BB) has to perform several functions which are essential for the reactor operation. The HCLL TBM is one of the Breeding Blanket concepts to be tested in ITER. It is cooled by He and uses the eutectic liquid metal LLE (Lithium–Lead Eutectic) as breeder material (enriched at 90% in ⁶Li).Pb–Li eutectic alloy has no known uses outside of fusion technology, so the available databases of this material are currently incomplete. It is very important, within the material specifications, to have a complete characterization in order to define their chemical and physical properties, because any variation in the alloy composition has significant consequences in their behaviour, and therefore in their regenerative function inside the blanket.The chemical characterization methodology developed and presented in this paper (useful for both Pb–Li alloys as any Pb alloy) is a key tool that allows performing standard quality control procedures for base material and/or monitoring the alloy during the reactor operation. This report provides a procedure to perform a wide material chemical characterization, assessing the concentrations of major elements, as well as a review of trace level elements that can be found both in the eutectic alloy and in starting materials. In this determination plays an important role the ICP-MS technique because, as a highly sensitive technique, allows very low detection limits.     

Results of Predictive Fokker?CPlanck Modelling of NBI Deuterons in ITER

First an analytical formalism is presented for calculating the source distribution of ions generated by neutral beam injection (NBI) in tokamak plasmas. A general NBI ion source term, applicable to studies in the phase space up to 6 dimensions, is provided for neutral beams with finite thickness and divergence. Further, using this source term for the envisaged NBI in ITER, we carry out 3D Fokker?CPlanck modelling of the steady-state deuteron distribution function of NBI produced fast deuterons relaxing on bulk plasma components. For two basic ITER scenarios we demonstrate the poloidal profiles of the beam deuteron density, of the NBI generated current as well as of the NBI power deposition to bulk electrons and ions. Further, we evaluate the capability of gamma and NPA diagnostics of NBI ions in ITER and demonstrate the sensitivity of the distributions of NBI generated ions to different ITER operation scenarios.     

How tightly is the nuclear symmetry energy constrained by a unitary Fermi gas?

We examine critically how tightly the density dependence of nuclear symmetry energy E_(sym)(q) is constrained by the universal equation of state of the unitary Fermi gas EUG(q) considering currently known uncertainties of higher order parameters describing the density dependence of the equation of state of isospin asymmetric nuclear matter. We found that E_(UG)(q) does provide a useful lower boundary for the E_(sym)(q). However, it doesnot tightly constrain the correlation between the magnitude E_(sym)(q_0) and slope L unless the curvature K_(sym)of the symmetry energy at saturation density q_0 is more precisely known. The large uncertainty in the skewness parameters affects the E_(sym)(q_0) versus L correlation by the same almost as significantly as the uncertainty in K_(sym).     

How crystal configuration affects the position detection accuracy in pixelated molecular SPECT imaging systems?

It is well known that inter-crystal scattering and penetration(ICS-P) are major spatial resolution limiting parameters in dedicated SPECT scanners with pixelated crystal.In this study,the effect of ICS-P on crystal identification in different crystal configurations was evaluated using GATE Monte Carlo simulation.A ~(99m)Tc pencil-beam toward central crystal element was utilized.Beam incident angle was assumed to vary from 0° to 45° in 5° steps.The effects of various crystal configurations such as pixel-size,pixel-gap,and crystal material were studied.The influence of photon energy on the crystal identification(CI) was also investigated.Position detection accuracy(PDA) was defined as a factor indicating performance of the crystal.Furthermore,a set of ~(99m)Tc point-source simulations was performed in order to calculate peak-to-valley(PVR) ratio for each configuration.The results show that the CsI(Na)manifests higher PDA than NaI(TI) and YAP(Ce).In addition,as the incident angle increases,the crystal becomes less accurate in positioning of the events.Beyond a crystal-dependent critical angle,the PDA monotonically reduces.The PDA reaches 0.44 for the CsI(Na) at 45° beam angle.The PDAs obtained by the point-source evaluation also behave the same as for the pencil-beam irradiations.In addition,the PVRs derived from flood images linearly correlate their corresponding PDAs.In conclusion,quantitative assessment of ICS-P is mandatory for scanner design and modeling the system matrix during iterative reconstruction algorithms for the purpose of resolution modeling in ultra-high-resolution SPECT.     

Secondary hydriding during LOCA – Results from the QUENCH-L0 test

A shortened loss of coolant scenario was simulated experimentally at fuel rod bundle scale in the QUENCH-L0 test. All pressurized specimens burst at temperatures between 790 and 855 °C. The hydrogen distribution in the cladding of chosen fuel rod simulators was studied by neutron radiography and tomography. As the results of these investigations show, the inner oxidation level, depending on time between burst and cooling and the temperatures occurring during this time, are important parameters for the hydrogen uptake. No hydrogen uptake was measured for the specimen with less than 50 s between burst and quenching. For longer time intervals, hydrogen enriched bands were formed. These bended bands are oriented non-symmetrically to the tube axis. The width of the bands and the maximal hydrogen concentrations seem to increase with time between burst and quenching and with the temperatures during this period.     

On monitoring the tritium breeder in a lead–lithium cooled ceramic breeder (LLCB) module of the ITER

The operation of a tritium breeder is a most process among engineering problems of DEMO. In this study, a design for monitoring tritium-breeding in the reactor is discussed. Additionally, a system for the experimental estimation of the tritium-breeding ratio (TBR) and the tritium-breeding dynamics in a lead–lithium cooled ceramic breeder (LLCB) test module used in the ITER is proposed. The systems are based on tritium and neutron-flux measurements under the ITER plasma D–T experiments and the use of lithium ortho-silicate and lithium carbonate samples and neutron detectors. Different lithum-6 and lithium-7 isotope contents in the samples are used to measure neutron spectrum. The samples and detectors are delivered in containers to the test breeder module (TBM) on a monitor channel connecting the TBM to an operating zone of the ITER. The tritium content in the samples is measured in a laboratory by the liquid scintillation method.Pneumatic control is used to deliver the samples to the TBM and to extract the samples using the channel during plasma-operational pauses. Neutron calculation is performed to estimate the tritium content in the samples and the heat distribution in the materials of the channel under reactor irradiation. A measurement accuracy of the tritium content in the carbonate and orthosilicate samples can attain a level of 7% and 10%, respectively. The results of the channel-cooling calculation performed under the nominal operating conditions of the TBM (a plasma pulse) are presented in the paper.     

How Comprehensive Should a Transport System Be?

Abstract

This paper considers the different levels at which a transport operation and/or system can be pelformed and looks at the consequences for consignors and their organisation. There are several levels of service at which to organise the shipment of radioactive materials: A basic one where a truck and a properly trained driver will be the main system. Quality assurance, security and radiation protection must be adequately handled. Intermediate levels, where the transport company also provides loading and unloading assistance, and/or training for the operators at both ends of the transport chain. Supplying information concerning the most appropriate packaging and the compatibility of the expected contents, and a certificate of licence for the packaging. Pelforming a regulatory and legal watch on potentially significant changes. Providing a full transport service, including everything from training to transport operation, programming of packaging procurement and maintenance, anticipation of licence renewals, route studies, real-time tracking, emergency response, support for consignor compliance and technical and paper work. The paper will also show how the different levels of service affect the shipper and receiver organisation.     

How does a change in the control room design affect diagnostic strategies in nuclear power plants?

Recently, main control rooms have been considerably changed by modern computer techniques. Some of the features that distinguish digital control rooms from conventional, analog rooms in nuclear power plants include advanced alarm systems, graphic information display systems, computerized procedure systems, and soft control. These features can bring changes in operator tasks, changing the characteristics of tasks or creating new tasks for operators. It is especially expected that these features may bring out changes in the operator's diagnostic tasks and strategies in a digital control room as compared with an analog control room. This study investigates the differences in the operator's diagnostic tasks and strategies in analog and digital control rooms. This study also attempts to evaluate how new systems in a digital control room affect diagnostic strategies. Three different approaches, which are complementary, are used to identify diagnostic strategies in the digital control room and in the analog control room: (1) observation in the simulator, (2) interview with operators, and (3) a literature review. The results show that the digital control room introduces new diagnosis strategies compared with the analog control room while also changing the characteristics of the strategies, mostly by gaining more support from the computerized system.     

Design of the Control System of Toroidal Field （TF） Power Supply for J-TEXT Tokamak

J-TEXT, formerly TEXT-U at the University of Texas at Austin in USA, is a medium-sized tokamak at the Huazhong University of Science and Technology. The toroidal field （TF） power supply of this tokamak should provide a current of 160 kA and a flat duration of 500 ms for the toroidal field coils to generate a maximum toroidal field of 3 T at the geometric center of the vaccum vessel. This paper presents a design of a new control system which takes the real-time feedback control option for the TF power supply operation. The system was tested successfully during the commissioning. In the first experimental campaign of J-TEXT, the system effectively controlled the power supply to provide a fiat current up to 92.5 kA and therein the TF produced reached 1.74 T, which enabled the machine to generate the first plasma successfully.     

Electromagnetic–thermal–structural coupling analysis of the ITER edge localized mode coil with flexible supports

In a fusion reactor, the edge localized mode(ELM) coil has a mitigating effect on the ELMs of the plasma. The coil is placed close to the plasma between the vacuum vessel and the blanket to reduce its design power and improve its mitigating ability. The coil works in a high-temperature,high-nuclear-heat and high-magnetic-field environment. Due to the existence of outer superconducting coils, the coil is subjected to an alternating electromagnetic force induced by its own alternating current and the outer magnetic field. The design goal for the ELM coil is to maintain its structural integrity in the multi-physical field. Taking as an example the middle ELM coil(with flexible supports) of ITER(the International Thermonuclear Fusion Reactor), an electromagnetic–thermal–structural coupling analysis is carried out using ANSYS. The results show that the flexible supports help the three-layer casing meet the static and fatigue design requirements. The structural design of the middle ELM coil is reasonable and feasible. The work described in this paper provides the theoretical basis and method for ELM coil design.     

Engineering-scale test on the thermal–hydro–mechanical behaviors in the clay barrier of a HLW repository

The thermo–hydro–mechanical (T–H–M) behaviors of a clay barrier are of importance from a performance and safety viewpoint of the engineered barrier system (EBS) for a high-level waste (HLW) repository. An engineering-scale test was carried out to investigate the T–H–M behaviors in the buffer of the Korean reference disposal system (KRS). The test started on May 31, 2005 and is still in operation. The experimental data obtained allowed a preliminary and qualitative interpretation of the T–H–M behavior in bentonite blocks. The temperature was higher as it became closer to the heater, while it became lower as it was farther away from the heater. The water content had a higher value in the part close to the hydration surface than that in the heater part. The relative humidity data suggested that a hydration of the bentonite blocks might occur by different drying–wetting processes, depending on their position. The total pressure was continuously increased by the evolution of the saturation front in the bentonite blocks and thereby the swelling pressure. There was also a contribution of the thermal expansion of the bentonite blocks near the heater and the capillary force in the dry bentonite blocks which the water did not reach from the hydration surface.     

The control and monitor system for the BESⅢ ETOF/MRPC beam test

A test system is developed for the BESIII ETOF/MRPC beam tests of data acquisition, environment monitoring and automatic control. The software framework is based on the CAMAC bus, VME bus and Serial Port,which are responsible for communications with the detectors. The monitor system works well in the beam test.