[en] The ITER poloidal field (PF) coils are wound from a large cable-in-conduit-conductor, with a stainless steel (SS) jacket. Tapered bonded tails, consisting of shaped steel profiles welded to the conductor ends, are used in these PF coils to mechanically attach the conductor ends to the winding pack. Their main function is to transfer the tensile force from the end of the outermost turn to the adjacent turns by shear through an appropriate thickness of insulating material (glass epoxy). These tails are embedded in the winding pack thus avoiding any local protrusion. Similar tapered bonded tails have been extensively used in large copper coils. However, compared with a standard copper conductor, the tensile force to be transferred to the winding pack is larger in the ITER PF conductor because of the higher tensile stress experienced by the SS jacket (average tensile stress up to 200 MPa). This led to a new hollow tail design capable of transferring the large tensile force carried by the PF coil conductors over a length in the range 600-650 mm. Hollow tails, as opposed to solid tails, provide a larger bonded perimeter for the same effective tail cross section, which also contributes to limiting the peak shear stress in the insulation. As a first step, the geometry of the tail has been optimised through a 1-D analytical straight model that solves the force balance between shear in the insulation and tension in the tail along its length. In a second step, a FEA (finite element analysis) of the most promising configuration has been performed in order to validate the design

[en] There is a question of where the primary system of a pressurized water reactor (PWR) will fail in a high pressure severe accident scenario. The core heatup process involves a race between whether the hot leg or surge line will fail from power operated relief valve (PORV) flows or buoyancy driven convection of heat or whether the lower head fails from melting and draining away of the core. The Three Mile Island Unit 2 (TMI-2) accident constitutes an important data point in reaching a determination. Any explanation or model of the process must not be inconsistent with what happened at TMI-2. There is, however, the question of 'What did happen at TMI?' Given that nearly half the core was molten, why were temperatures not experienced sufficient to melt upper plenum structures or fail the hot leg? The initial studies of TMI-2 concentrated on developing an overall description of the events that took place. Also, the studies were carried out prior to the identification of the issue of failure of the surge line or hot leg prior to vessel failure in a high pressure severe accident scenario. Subsequent analyses have been primarily aimed at characterizing the state of core damage and not the thermal hydraulics of the accident. The TMI-2 accident sequence must, therefore, be examined in terms of energy distribution during the period of core uncovery

[en] In this paper, we report about the fatigue life assessment of the ITER central-solenoid (CS) together with the related stress analyses. Two design options for integrating the structural support into the conductor have been considered. Various sources of fatigue crack growth rate (FCGR) data (including the CS model coil) have been taken into account. R and D is still needed to confirm the various assumptions made about the material quality and inspection procedures that have not yet been justified by any trial production

[en] Nb₃Sn forced flow cooled cable in conduit superconductors for fusion applications can be optimized for combinations of field, peak operating temperature and coil winding layout (pancake or layer) to give either maximum cable space current density or minimum superconductor cost. Conductor design for ITER including design criteria, choice of conductor configurations and its optimization are discussed

[en] The problem of the high level dimensional to be obtained for the construction of these coils is a fundamentally important element in terms of the correct functioning of the whole magnet. In order to achieve this objective specific methodologies and tools for production and control were studied and applied to have the desired results with completely satisfactory results. With machining practically finished one can now synthesize the experience gained describing the more important results and the methods used, showing: the importance of the precision required in relation to operational functioning; the manufacturing solutions adopted and the operative measuring modalities; and the values and the deviations obtained

[en] Considerations on cost sensitive areas related to ITER magnet conductors such as the magnet operating conditions (heat deposition), the conductor design layout (design criteria and related margins), the conductor fabrication (material waste and achievable performance) as well as recent R and D development show that there is some potential to reduce the present ITER conductor cost. A review of the conductor requirements is used as a basis to set up an alternative design approach. (author)

[en] The general NRC research philosophy as given in the Five-Year Plan, is quoted so that one can better appreciate the activities in the specific research area of thermal hydraulics (T/H). These activities are then described as they exist in the current version of the Five-Year Plan. A historical perspective of T/H research is next presented, emphasizing the accomplishments leading to the revised ECCS rule and the role of cooperative research with both international and domestic institutions. A plan for increased use of assessed T/H computer codes by the NRC staff is discussed. The need for adequate documentation of completed codes is then described. The paper ends with a short description of future paths for T/H research. The contribution of Dr. S. Levy to the Advanced Code Review Group and the study on Code Scalability Accuracy and uncertainty is acknowledged. (orig.)

[en] Ongoing efforts to develop the technical basis for revising the pressurized thermal shock rule require a consistent treatment of uncertainties across engineering disciplines. Application of a few key principles for treating these uncertainties, based on a classification of the sources of uncertainty, has led to a number of changes in the analytical methods and tools being developed. (author)

[en] Within the research program on the International Thermonuclear Experimental Reactor (ITER) Poloidal Field (PF) coils, a full size conductor sample was tested in the SULTAN facility (CRPP Villigen, Switzerland). This sample is composed of two straight ITER-like cable-in-conduit conductors, using the same NbTi strand. The two conductors are identical except for one leg makes use of a cable containing steel wraps around the main sub-cables as in the ITER design, while the other has no wraps inside. The paper presents conductor DC tests results compared to predictions given by various models developed within ITER-associated laboratories. These models aim to predict the DC behaviour of the cable from the experimental performances of the single strand. They have to explain the observed voltage-current (V-I) or voltage-temperature (V-T) characteristics, including the thermal runaways. The lower experimental performances compared to all expectations have shown the necessity to revise the models and to introduce a possible uneven current distribution among the strands of the cables. (authors)

[en] The Westinghouse Electric Corporation has developed a new, advanced light water reactor, the AP600, and has submitted the design for U.S. Nuclear Regulatory Commission certification. Westinghouse conducted supporting testing programs to provide experimental data to validate its computer codes used to analyze the performance of the AP600 design. One of these facilities was a reduced-pressure, reduced-height (1:4) integral system test facility located at Oregon State University-the Advanced Plant Experiment (APEX). The governing objective of the testing program was to evaluate system depressurization, transition to in-containment refueling water storage tank (IRWST) injection, and long-term cooling. A key feature in the long-term cooling data from some of the APEX experiments is flow oscillations that begin upon return to saturated conditions at the core exit. In this paper, the mechanism for these oscillations is explained, their relevance to the AP600 is discussed, and conclusions about their safety significance are drawn