00214 Overview of the spallation neutron source (SNS) with emphasis on target systems

05

Nuclear

fuels

(scientific,

compounds) under fast neutron carried out together with other ations, such as ASTE, JESSICA,

technical) irradiation. Most of these efforts are projects within international collaborLiSoR, STIP, URAM and others.

04/00211 Materials research and development for the spallation neutron source mercury target Mansur, L. K. Journal of Nuclear Materials, 2003, 318, 14-25. In the spallation neutron source target, the structural material will be exposed to intense pulsed fluxes of high-energy protons and neutrons, which produce radiation damage. These pulsed fluxes also lead to pressure pulses created by beam heating. In turn, the pressure pulses give rise to fluctuating stresses in the 316 LN austenitic stainless steel target vessel, and to cavitation in the liquid mercury spallation target. Corrosion reactions and related changes in mechanical properties also may occur through contact with flowing mercury. In this report the materials research and development programme for the spallation target is described. It covers the areas of cavitation erosion, radiation effects, and compatibility. Cavitation erosion work includes pressure wave tests at the LANSCE proton accelerator, as well as laboratory tests that simulate aspects of the actual in-beam exposures. Materials irradiations are being carried out in spallation environments at highenergy and high-power proton accelerators. Other experiments are conducted at irradiation facilities that simulate aspects of spallation conditions. Extensive radiation damage and transmutation calculations supplement these experiments. Compatibility work includes both thermal convection and pumped flow loop tests to examine temperature gradient mass transfer, as well as fatigue and tensile tests in contact with Hg. Based on the information developed for radiation effects and compatibility with mercury, the analysis indicates that the target will meet its intended service requirements. Over the last 18 months of the study the new issue of cavitation erosion has been included in the programme. Both in-beam and laboratory experiments indicate that cavitation erosion may occur in the target. The highest priority activity is now to determine whether cavitation erosion will limit target lifetime to a level below the lifetime limit set by radiation effects. 04/00212 Next step spherical torus design studies Neumeyer, C. et al. Fusion Engineering and Design, 2003, 66-68, 139145. Studies are underway to identify and characterize a design point for a next step spherical torus (NSST) experiment. This would be a ‘proof of performance’ device which would follow and build upon the successes of the national spherical torus experiment (NSTX) ‘proof of principle’ device which has operated at PPPL since 1999. With the decontamination and decommissioning (D&D) of the tokamak fusion test reactor (TFTR) nearly completed, the TFTR test cell and facility will soon be available for a device such as NSST. By utilizing the TFTR test cell, NSST can be constructed for a relatively low cost on a short time scale. In addition, while furthering spherical torus (ST) research, this device could achieve modest fusion power gain for short pulse lengths, a significant step toward future large burning plasma devices now under discussion in the fusion community. The selected design point is Q = 2 at HH = 1.4, Pfuslon = 60 MW, 5-s pulse, with Ra = 1.5 m, A = 1.6, Ip = 10 MA, Bt = 2.6 T, CS FLUX = 16 weber. Most of the research would be conducted in DD, with a limited DT campaign during the last years of the programme. 04/00213 Next-generation plasma control in the DIII-D tokamak Walker, M. L. et al. Fusion Engineering and Design, 2003, 66-68, 149153. The advanced tokamak (AT) operating mode, which is the principal focus of the DIII-D tokamak requires highly integrated and complex plasma control. This paper describes progress towards the DIII-D AT mission goal through both improvements in real-time computational hardware and control algorithm capability. A number of device constraints, some unique to DIII-D, and their impact on operational shape and position control are discussed. Some partial solutions are described. 04/00214 Overview of the spallation neutron source (SNS) with emphasis on target systems Gabriel, T. A. et al. Journal of Nuclear Materials, 2003, 318, 1-13. The status of the spallation neutron source (SNS) is discussed. In addition, a more detailed overview is given of the Target Systems’ part of the SNS with emphasis given to the technology issues that present the greatest scientific challenges. At present, SNS is within budget and schedule limits and excellent progress is being made on all fronts design, fabrication, installation, and testing. First beam on the Hg target system is expected in December 2005. The project, as of June 2002, was 42% complete. 04/00215 Overview Bibet, Ph. et al. Fusion 26

Fuel

and

Energy

of the ITER-FEAT LH system Engineering and Design, 2003, 66-68, Abstracts

January

2004

525-529.

LH is considered to be used in ITER-FEAT steady-state scenario thanks to its highest current drive efficiency in the plasma outer part. The design of a 5 GHz, 20 MW CW LH system has been realized. That relies on a transmitter of 24 l-MW klystrons, and a circular oversized 60-m long transmission line feeding an antenna, based on the passive active multi-junction concept. In order to have a high reliability, the power density is limited to 33 MWlm’. After the system description, the results of different studies are given: RF computation, launcher coupling properties, thermal analysis, mechanical stress caused by disruption, neutron activation, acceleration of electrons in the antenna near field. 04/00216 Oxidation of spent UOp fuel stored in moist environment Leenaers, A. et al. Journal of Nuclear Materials, 2003, 317, (2-3), 2266 233. Spent fuel remnants, cut from BWR fuel rods were retrieved for microscopic investigations after 25 years of storage at ambient temperature. The storage atmosphere of the samples studied here was dry air for 10 years and a moist environment for the remaining 1.5 years. The comparison with earlier experiments conducted on samples that were stored in dry air for the full period demonstrates that moisture accelerates the oxidation process also at the low temperatures considered here. The composition of the atmosphere in contact with the fuel has been analysed by mass spectrometry and the microstructure of the samples has been investigated by optical and scanning electron microscopy. The microscopic observations evidence that grain boundaries are affected and different stages in grain boundary alteration could be evidenced. Oxidation first induces a weakened intergranular bond followed by increased sensitization to chemical attack and finally decohesion and onset of bulk oxidation. 04/00217 Plans for a new ECRH system at ASDEX upgrade Leuterer, F. et al. Fusion Engineering and Design, 2003, 66-68, 537-542. A new ECRH system is being constructed for ASDEX Upgrade with a total power of 4 MW, generated by four gyrotrons, and a pulse duration of 10 s. Particular features are the use of gyrotrons which can work at various frequencies in the range 104-140 GHz and correspondingly broad band transmission components. The transmission will be at normal air pressure, and at the torus there will be a tunable double disk vacuum window. A further aim is the installation of fast moveable mirrors for a feedback controlled localized power deposition. 04/00216 Preliminary results and lessons learned from upgrading the Tore Supra actively cooled plasma facing components (CIEL project) Cordier, J. J. Fusion Engineering and Design, 2003, 66-68, 59-67. The design and fabrication of large areas of actively cooled plasma facing components (PFCs) is a major issue for the next generation of tokamaks. Tore Supra is currently the only large fusion device which has implemented actively cooled PFCs from the beginning of operation in 1988, while maintaining continuous development activities to improve their performances and reliability. High heat flux PFCs based on copper alloy heat sink structures have been developed in order to enable a large increase of power extraction capacity. The result is an actively cooled high heat flux ‘finger’ element (capable of removing up to 10 MW/m’ in normal steady state operation). It has been used first for the RF antennas edge limiters (200 fingers) and then for the toroidal pump limiter (TPL), which is the main part of the Tore Supra upgrade of in-vessel components (CIEL project). The active part of the TPL structure is made of -600 actively cooled elements. Problems appeared during series manufacturing of such a large number of high heat flux elements that finally led to the development of a tile attachment repair process in order to allow the achievement of the manufacturing. The whole limiter was installed inside the Tore Supra inner vessel at the beginning of 2002. Very promising first results have been recently obtained (600 MJ of injected and removed power during 3 min 30 s discharge). Monitoring and technical lessons for future realizations from these more-than-lo-year developments, in particular for ITER, are discussed. 04100219 Progress on fatigue characterization of ITER primary first wall mock-ups Dell’Orco, G. et al. Fusion Engineering and Design, 2003, 66-68, 3 1 l316. In 2001! EFDA has assigned to ENEA a contract for the’ thermomechamcal 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 programme, carried-out at ENEA Brasimone CEF l-2 thermal hydraulic facility, was focused on the thermal mechanical testing of these mock-ups aiming at verifying which tile geometry and manu-