Small-scale Mock-ups Research Articles

Blanket manufacturing technologies: Thermomechanical tests on helium cooled lithium lead (HCLL) blanket mocks up

In the Helium Cooled Lithium Lead (HCLL) blanket concept, the lithium lead plays the double role of breeder and multiplier material, and the helium is used as coolant. The HCCL blanket modules are made of steel boxes reinforced by stiffening plates. These stiffening plates form cells in which the breeder is slowly flowing. The power deposited in the breeder material is recovered by the breeder cooling units constituted by parallel cooling plates. All the structures such as first wall, stiffening and cooling plates are cooled by helium. Due to the complex geometry of these parts and the high level of pressure and temperature loading, thermomechanical phenomena expected in the “HCLL blanket concept” have motivated the present study. The aim of this study, carried out in the frame of EFDA Workprogram, is to validate the manufacturing technologies of HCLL blanket module by testing small scale mock-up under representative operating conditions. The experimental program is carried out on the DIADEMO facility at CEA Cadarache. This experimental device allows the coupling of a PbLi test section and an He cooling loop (pressure of 80 bar, maximum temperature of 500 °C, mass flow rate of 150 g/s) taking advantage of synergies with the gas-cooled fission reactor R&D program. The first step of the test program aims at exposing a simplified HCLL cooling plate mock-up in a fusion blanket environment (i.e. in PbLi and cooled by pressurized Helium) to ITER relevant conditions with thermal transients simulating plasma shut down. Three thousands thermal transient cycles have been performed in about 3 months, without any external visible damages on the mock-up. Post tests analyses are underway in order to investigate the behaviour of the cooling plate mock-up.

Development of the plasma facing components for the dome-liner component of the ITER divertor

On the basis of the design and the specification of the dome-liner elaborated by EFDA, a manufacturing route based on high temperature brazing has been developed and proved by means of the fabrication and testing of several samples and mock-ups. The dome is protected with tungsten armour tiles joined onto heat sinks obtained from a bimetallic plate made of precipitation hardened copper–chromium–zirconium alloy and stainless steel realized by explosion bonding. The brazed joint between the tungsten tiles and the heat sink has been qualified by means of thermal fatigue tests on small-scale mock-ups in reactor relevant conditions. The properties of the explosion bonding joint between the front copper alloy plate to the rear steel backing has been assessed by means of an extensive metallurgical and mechanical test program according to the specification provided by EFDA. The dimensional stability during the fabrication route has been investigated by means of the realization of a relevant curved component that has been dimensionally tested after the completion of each step of the manufacturing route. The results of the experimental activity are presented and discussed in this paper.

Computation of a core disruptive accident in the MARS mock-up

A hypothetical core disruptive accident in a liquid metal fast breeder reactor (LMFBR) results from the interaction between molten fuel and liquid sodium, which creates a high-pressure bubble of gas in the core. The violent expansion of this bubble loads and deforms the vessel and the internal structures. The MARS experimental test simulates a HCDA in a small-scale mock-up containing all the significant internal components of a fast breeder reactor. The mock-up is filled with water, topped by an argon blanket, and the explosion is generated by an explosive charge. This paper presents a numerical simulation of the test with the EUROPLEXUS code. The top closure is represented by massive structures and the main internal structures are described by shells. The current numerical results are described and compared with the experimental ones, and previous computations with the CASTEM-PLEXUS code.

Thermal fatigue of HIPed W/Cr–bronze divertor small scale mock-ups

Abstract Thermal fatigue is one of the key factors governing the lifetime of the divertor plate. Tungsten is a promising candidate to cover the surface of the divertor plate in the design of the international thermonuclear experimental reactor (ITER). The W/Cr–bronze divertor small scale mock-ups were manufactured by hot isostatic pressing (HIPing) technique. Thermal fatigue tests of W/Cr–bronze divertor mock-ups have been carried out by an electron beam facility. The mock-ups were tested under a cyclic surface heat flux of 9 MW m−2 for 1000 cycles. The electron beam was loaded on the mock-up surface for 20 s and unloaded for 20 s, alternately. The flow rate of water coolant was 0.1 L s−1. The 0.3 mm diameter NiCr–NiSi thermocouples were used to monitor the temperature distribution of the mock-up. It was found that the maximum temperature of the tungsten surface was about 400 °C. The saturated temperature at the joint of tungsten and Cr–bronze was 160 °C. The surface and the W/Cr–bronze joint of the mock-up did not show any damage during the thermal fatigue test up to 1000 cycles. A critical cooling flow rate Lc exists under a certain heat flux for a certain cooling system. The agreement between the experimental results and calculated temperature distributions was good.

Progress on fatigue characterization of ITER primary first wall mock-ups

In 2001, EFDA has assigned to ENEA a contract for the thermomechanical testing of six mock-ups of the ITER primary wall module. These small scale mock-ups, reproducing representative portions of the reference ITER primary wall panels, were fabricated during ITER EDA phase by solid hot isostatic pressing (HIPping) of an AISI 316L stainless steel back structure to a alumina dispersion strengthened (DS)-Cu alloy heat sink armored with beryllium tiles. The experimental program, carried-out at ENEA Brasimone CEF 1–2 thermal hydraulic facility, was focused on the thermal mechanical testing of these mock-ups aiming at verifying which tile geometry and manufacturing procedure assures the required reliability of the beryllium/DS-Cu alloy/SS joints at high incident heat flux (>0.8 MW/m 2) both at steady state and under thermal fatigue tests. The paper presents the progress in the experimental activity of the first test campaign and the main thermomechanical FEM analyses after the detachment and rupture of Beryllium tiles from one mock-up.

Manufacturing of small scale W monoblock mockups by hot radial pressing

In the frame of the European Technology R&D programme for International thermonuclear experimental reactor (ITER) and in the area of high heat flux plasma facing components (HHFC), representative small-scale mock-ups were manufactured and tested to compare different concepts and joining technologies (i.e. active brazing, hot isostatic pressing (HIPping), diffusion bonding, etc.). On the basis of the results obtained by thermal fatigue tests, the monoblock concept resulted to be the most robust one, particularly when the HIPping manufacturing technology is used. Within this programme, ENEA developed an alternative technique for manufacturing plasma-facing components with a monoblock geometry of the ITER machine. The basic idea of this technique, named hot radial pressing (HRP), is to perform a radial diffusion bonding between the cooling tube and the armour tile by pressurising the internal tube only and by keeping the process parameters within the range in which the thermo-mechanical properties of the copper alloys are not yet degraded. The HRP is performed by a standard furnace, in which only a section of the canister is heated. The manufacturing procedure and the results of the screening and fatigue thermal tests performed on the ENEA mock-ups are reported in this paper.

ICONE11-36404 COMPARISON OF THE NUMERICAL RESULTS OF EUROPLEXUS WITH THE MARS EXPERIMENT

In case of a Hypothetical Core Disruptive Accident (HCDA) in a Liquid Metal Reactor, the interaction between fuel and liquid sodium creates a high pressure gas bubble in the core. The violent expansion of this bubble loads the vessel and the internal structures, whose deformation is important. The experimental test MARS simulates a HCDA in a small scale mock-up containing all the significant internal components of a Fast Breeder Reactor. The test-facility is filled with water topped by an argon blanket and the explosion is generated by an explosive charge. Owing to the symmetry of the mock-up, an axisymmetrical representation is chosen for the numerical simulation of the MARS test-facility with the EUROPLEXUS computer code. The external structures are modelled by shells or massive structures and the main internal structures were described with a classical shell model. The peripheral structures are homogenised with the coolant. The paper presents a synthesis of the results of the numerical simulation and a comparison with the experimental results and the ones obtained in previous numerical simulations.

Thermal–mechanical test on ITER primary first wall mock-ups

In 1998, in the frame of the ITER EDA phase, an European R&D Programme for the Blanket Design was implemented for developing and selecting the materials and the relevant fabrication procedures for manufacturing the shielding modules of the ITER Primary Wall. The fabrication of several Beryllium armored small scale mock-ups, reproducing representative portions of a Primary Wall panels, was also launched (Fusion Technol. (1998) 195). Further experimental activities were also programmed for investigating the thermal–mechanical behavior of these mock-ups at high heat flux and under thermal fatigue tests. In 2001, the ITER European Home Team decided to assign to ENEA a contract for the thermal fatigue testing of six mock-ups aiming at verifying the reliability of the Beryllium/Dispersion Strengthened Copper alloy/Stainless Steel and Beryllium/Precipitation hardened Copper alloy/Stainless Steel joints manufactured by solid Hot Isostatic Pressing (HIP) procedure (Technical Specification for the Thermal Fatigue Tests of Be protected EDA Mock-ups). The paper presents the results of the FEM thermal–mechanical analyses performed by ANSYS code and the progress of the first test campaign.

Manufacture and first wall joining for an ITER primary wall module prototype: R&D phase with small scale mock-ups

In the frame of the Primary Wall Module prototype manufacturing for ITER, a consistent R&D phase was conducted in order to identify the industrial allowable tolerances and manufacturing problems which would occur when joining pieces by HIPping process during the PW module manufacturing. The purpose of this development was to give as industrial as possible manufacturing routes for joining together large Stainless Steel or DS-Copper pieces with Stainless Steel tubes and for bonding Beryllium tiles onto a curved component surface. The study concerned surface preparations, allowable gaps and joint geometry, Beryllium tile geometry, Titanium interlayer thickness, … This R&D phase also allowed the development and validation of different ultrasonic inspection tools needed for plate-plate, tube-plate, edge to edge plate bonding.

Manufacturing and testing of monoblock tungsten small-scale mock-ups

In the frame of the European Technology R&D program for ITER, and in the area of High Heat Flux plasma facing Components (HHFC), representative small-scale mock-ups were manufactured and tested to compare different concepts and joining technologies (i.e. active brazing, Hot Isostatic Pressing (HIPping), diffusion bonding, etc.). On the basis of the results obtained by thermal fatigue tests, the monoblock concept resulted to be the most promising one, particularly when the HIPping manufacturing technology is used. Within this program, ENEA manufactured tungsten monoblock mock-ups by using the HIPping technology. The mock-ups were tested with respect to thermal fatigue and, upon screening tests, the best performance obtained was 15 MW/m 2 for 200 cycles. One of these mock-ups was enclosed in the ‘Paride’ neutron irradiation campaign. This campaign has the scope of enlarging the available database on the performance degradation of prototypical basic solutions of the ITER plasma facing components due to neutron irradiation. The manufacturing procedure and the results of the screening and fatigue thermal tests performed on the ENEA mock-ups are reported in this paper.

Manufacture and first wall joining for an ITER primary wall module prototype: results of a medium scale mock-up manufacturing

In the frame of the Blanket development programme for ITER, the design envisaged a blanket-shield constructed from modules. Primary Wall Modules consisted of a water-cooled austenitic stainless steel (S.S.) Shield Block and a First Wall, as an integral part of it. The Primary First Wall uses a DS-copper alloy as the heat sink material bonded to the shield block and a protection material such as Beryllium, to cope with the plasma/wall interaction. The module was designed to sustain a peak heat flux of 0.5 MW/m 2. A manufacturing program was implemented to demonstrate the feasibility for joining the Primary First Wall onto the Shield, which included the manufacture of small scale and medium scale mock-ups, before the manufacture of a prototype. The aim of the paper is to present the different steps and results of a Medium Scale Module manufacturing.

ITER-FEAT vacuum vessel and blanket design features and implications for the R&D programme

A configuration in which the vacuum vessel (VV) fits tightly to the plasma aids the passive plasma vertical stability, and ferromagnetic material in the VV reduces the toroidal field ripple. The blanket modules are supported directly by the VV. A full scale VV sector model has provided critical information related to fabrication technology and for testing the magnitude of welding distortions and achievable tolerances. This R&D validated the fundamental feasibility of the double wall VV design. The blanket module configuration consists of a shield bodyto which a separate first wall is mounted. The separate first wall has a facet geometry consisting of multiple flat panels, where 3-D machining will not be required. A configuration with deep slits minimizes the induced eddy currents and loads. The feasibility and robustness of solid hot isostatic pressing joining were demonstrated in the R&D by manufacturing and testing several small and medium scale mock-ups and finally two prototypes. Remote handling tests and assembly testsof a blanket module have demonstrated the basic feasibility of its installation and removal.

Main achievements of the EU HT test programme of ITER primary wall small scale mock ups

This paper presents the main achievements of the European Home Team (EU HT) test programme of ITER primary wall small scale mock ups. It describes briefly the fabrication method of the mock ups, the test conditions and the main results obtained with high heat flux and thermal fatigue tests of Cu alloy/stainless steel and beryllium/Cu alloy/stainless steel mock ups. The results obtained so far show very good thermal fatigue performance and operation margin of the ITER primary first wall concept.

Development of High-Z Plasma Facing Components for ITER

During the ITER EDA (Engineering Design Activity), the US Home Team developed improved methods for fabricating tungsten armored plasma facing components. Thermo-mechanical modeling indicated the desirability of using “brush-like” structures (clusters of small filaments or rods) as a means of reducing thermal stresses. The commercial availability of tungsten welding electrode rods (1.6 mm and 3.2 mm diameter) significantly reduced the raw material costs. Three approaches were developed: (1) Cu is plasma sprayed to the W brushes followed by diffusion bonding or e-beam welding the copper backing to the CuCrZr heat sink, (2) Molten Cu is cast directly on the tips of the W brushes followed by the diffusion bonding step, and (3) W rods are sputter-coated with a bonding aid and are directly bonded to the CuCrZr heat sink using HIP or vacuum hot pressing. High heat flux testing was performed up to 18 MW/m2 without damage to two small-scale divertor mockups.

ITER baffle module small-scale mock-ups: First Wall thermo-mechanical testing results

The EU-Home Team is in charge of the R&D related to the ITER Baffle First Wall. Five small-scale mock-ups, using Be, CFC and W tiles and different armour/heat-sink material joints under development, have been fabricated and thermomechanically tested in FE200 (Le Creusot) and JUDITH (Jülich) Electron Beam facilities. The small-scale mock-ups have been submitted to thermo-mechanical fatigue tests (up to failure using accelerating techniques). The objective was to determine the performances of the armour material joints under high heat flux cycles.

Overview of advanced techniques for fabrication and testing of ITER multilayer plasma facing walls

The design of the ITER primary first wall incorporates a multi-layered structure consisting of a layer of beryllium bonded to a layer of copper alloy with embedded stainless steel tubes which in turn is bonded to a stainless steel structure. In this configuration, the stainless steel provides structural support, the copper alloy improved resistance to high heat loads, and the beryllium layer a low Z metal interface with plasma. Fabrication, testing and control of this multi-layered structure, and indeed the entire blanket shield module, calls for advanced methods. Several associations in the four home teams and their industrial partners have been involved in various fabrication and joining tasks now grouped under L4 blanket project. In this paper, an overview of the work done so far for joining stainless steel to stainless steel, stainless steel to copper alloy, copper alloy to copper alloy, and copper alloy to beryllium is presented. Specialised papers dealing with most of the topics treated here are scheduled in this symposium. The fabrication and joining methods presented here, other than the conventional welding and brazing, follow four main routes. Two of them make extensive use of hot-isostatic pressing (HIP); (a) solid to solid; (b) solid or powder to powder, with or without a prior cold or hot isostatic pressing of one of the products. The third combines advantages of casting and HIPping for fabricating large and complex parts. The fourth investigates the possibility of using explosive welding for joining copper alloys to stainless steel. Other methods, including friction welding, are investigated for specific parts. After a brief recall of considerations leading to selection of individual materials, specifications derived for wrought and powder products are presented. Optimised conditions for bonding steel to steel, copper to copper and steel to copper are tabulated and preliminary results obtained from tests on joints are compared with the values obtained for parent materials. Also presented in the paper are the results obtained from high heat flux testing of small scale mock-ups. Throughout the paper the collaboration with industry in defining specifications for reference products, fabrication routes, and construction of large scale mock-ups and their testing are referenced.

Overview of the EU small scale mock-up tests for ITER high heat flux components

This task within the EU R&D for ITER was aimed at the development of basic manufacturing solutions for the high heat flux plasma facing components such as the divertor targets, the baffles and limiters. More than 50 representative small-scale mock-ups have been manufactured with beryllium, carbon and tungsten armour using various joining technologies. High heat flux testing of 20 of these mock-ups showed the carbon mono-blocks to be the most robust solution, surviving 2000 cycles at absorbed heat fluxes of up to 24 MW m −2. With flat armour tiles rapid joint failures occurred at 5–16 MW m −2 depending on joining technology and armour material. These test results serve as a basis for the selection of manufacturing options and materials for the prototypes now being ordered.

Optical Measurement of Cable and String Vibration

This paper describes a non contacting measurement technique for the transverse vibration of small cables and strings using an analog position sensing detector. On the one hand, the sensor is used to monitor the cable vibrations of a small scale mock‐up of a cable structure in order to validate the nonlinear cable dynamics model. On the other hand, the optical sensor is used to evaluate the performance of an active tendon control algorithm with guaranteed stability properties. It is demonstrated experimentally, that a force feedback control law based on a collocated force sensor measuring the tension in the cable is feasible and provides active damping in the cable.

Simulation of electromechanical and thermomechanical loads on first wall mock-ups

Abstract In order to study the boundary conditions for the occurrence of ratcheting, a testing rig was erected. In this rig, small-scale mock-ups of the first wall were tested under mechanical conditions similar to those expected during disruptions. These mock-ups were made of stainless steel AISI 316. They were heated on the surface and water cooled from inside. Disruption forces were simulated by a high-speed hydraulic bending system by impact loads. The mock-ups were heated by a high-frequency generator and cooled by water through two cooling channels. In addition to the experimental work, simplified analytical analysis and numerical calculations were carried out using the finite element program abaques . In these calculations, the temperature and stress fields in the mock-ups were investigated and the influence of the different constitutive equations was studied. The experimental results confirm the ratcheting behaviour predicted by the calculations. It has been demonstrated that the ratcheting behaviour for constant mechanical and cyclic thermal loads is much stronger than in the case when both loads are cyclic in nature.

Evaluation of Three Methods of Rendering Upholstery Fabrics Smolder Resistant

Three methods of rendering upholstery fabrics smolder resistant were evaluated by determining the rate and extent of percent weight loss of a small scale mock-up system when the fabrics, with and without treatment, were tested in combination with F.R. cotton batting, F.R. polyurethane foam and resinated polyester fiber batting. A lit cigarette was placed in the crevice formed by the abutment of vertical and horizontal panels. The three methods of treatment in cluded two types of backcoating and a methyl borate vapor phase treatment of the entire fabric.