[en] As part of an international collaboration, the Stanford Linear Accelerator Center (SLAC) klystron group has designed, fabricated, and tested a 60-Hz, 3-μs, 150-MW S-band klystron built for Deutsches Elektronen Synchrotron (DESY). A test diode with a 535-kV, 700-A electron beam was constructed to verify the gun operation. The first klystron was built and successfully met design specifications. The 375-MW electron beam represents a new record for SLAC accelerator klystrons in terms of voltage, current, energy, and ruggedness of design. The rf output power is a 150% increase over the S-band tubes currently used in the two-mile-long linear accelerator at SLAC. This paper discusses design issues and experimental results of the diode and klystron

[en] Short communication. Published in summary form only

[en] Since the first landmark by Bekefi announcing a 900MW relativistic magnetron, substantial improvements accomplished peak power levels of several gigawatts. However, pragmatic considerations emphasized repetitive mode of operation and longer pulse duration (i.e., higher average power) at the expense of peak power. Repetition rate of about 200pps with peak power levels around 600-300MW and pulse lengths 30-70ns (∼) 20J/pulse) were achieved . It seems that pulse duration, at these power density levels, is restrained by universal, not fully understood, mechanisms. At Rafael, we initiated a relativistic magnetron research program aiming for rep- rated generation of 150 - 200ns long pulses with peak power of about 100MW. Our magnetron design (Patent pending) is fundamentally different from those that led to the achievements mentioned above. The cathode is grounded and the positive H.V. pulse is injected to the anode block (essentially, an A6 resonator) through an external cavity, that serves as a buffer cavity between the anode-cathode interaction region and the output waveguide. In this grounded cathode geometry the axial current is eliminated (improving efficiency). For the cathode, we conceived o special scheme of alternating metal/ dielectric disks, employing the principle of triple point plasma initiation . At present, the magnetron is driven by a rep-rated (≥20pps), 120Ω, Marx-PFN generator. Pulse trains of 50MW peak power and 150ns duration at 10Hz were measured with Vgenerator=300kV, Vdiode=180kV, Idiode=kA, and η=28%. At higher charging voltage, improved vacuum conditions, and lower rep-rate, 100MW pulses have been measured with Vgenerator=360kV, Vdiode=180kV, Idiode=1.5kA, and η=37%. However, these pulses tend to be shorter, about 70ns long. We present detailed studies of the emitted pulse shape, the temporal evolution of its spectral power density and diode impedance, which suggest some physical insight to the relativistic magnetron's operation. We also show some preliminary 2-D computer simulations to support our understanding of the power transfer density. (authors)

[en] Summary only

[en] Small reactors are likely to be less economic than large reactors, but the lower financial exposure with small reactors may be attractive to utilities contemplating a restart to a nuclear programme. New nuclear plant can be economic, but success will depend more on how the plant are built, rather than what type or size is built. A target for new plant for operation early in the next century should be a generation cost of 3p to 3.5 p/kWh. This corresponds to an overnight capital cost of Pound 1000/kWh to Pound 1100/kWh. (author)

[en] The increase in the number of small reactor design concepts which have been announced is a clear indication of vendor's increased interest and their commitment to the development of smaller nuclear power plants. These concepts include the Candu 3 pressurised heavy water reactor. Many of the concepts are based on earlier designs, but updated and modified to include: emphasis on reduced or minimal duration construction schedules; utilisation of systems, components, and concepts which have been proven by commercial operation; simplifications are made possible by taking advantage of particular inherent small reactor characteristics; high levels of prefabrication and modularisation; and recognition of site conditions applicable to a variety of typical developing country sites are additional important modifications. The CANDU 3 is a small reactor design which includes all of the above small and medium sized nuclear power plant design trends. The ways in which these as well as other specific design features help in establishing the advantage of small nuclear power plants relative to larger plants, is discussed. However since the reactor is used to illustrate these arguments, a brief overview of its design is first given. (3 figures, 2 tables). (Author)

[en] Annual and cumulative (lifetime) load factors to the end of December 1990 are listed for reactors of 150 MWe gross and above. Compared with the previous year, 1990 has seen a modest improvement in the average performance of PWRs, BWRs and Magnox reactors in terms of average annual load factors. Interestingly, the four units with the highest load factors in 1990 were all Japanese, with the top three reactors -namely Mihama 3, Genkai 2 and Ikata 2 - recording load factors of 100%. However in 1990 far fewer reactors achieved load factors of over 90% than in 1989: some 20 in 1990 compared with 33 in 1989. (author)

[en] Load factors for reactors of 150MWe gross and above for the 12 month period up to the end of March 1991, and over their lifetimes, are tabulated. (author)

[en] Annual and lifetime load factors to the end of December 1996 are listed for reactors of 150MWe and above. These are based on regular monthly data and do not cover China, Armenia and Kazakhstan. The lifetime data are also presented in terms of country averages and reactor types. (7 figures; 8 tables). (UK)

[en] The purpose of the meeting was to provide an opportunity for various vendors of small power reactors (under 1MW) to present their ideas and designs, and to subsequently respond to comments and criticisms from an informed audience. Two contrasting papers were presented on the economics of small plant. The perceived view within Nuclear Electric of the economic targets for small PWR reactor designs within the United Kingdom was outlined. The designs under consideration are AP600 and SIR. The presentation concentrated on the various factors making up the overall generating cost, in particular the capital charges, stressing the need to account for the design and launch costs and additional risk of the first-of-a-kind plant. The main conclusion was that small plant were likely to be less economic than large, although utilities may be attracted by this option as a method of restarting a nuclear programme, and that the UK targets would be around Pound 1100/kW installed and 3-3.5 p/kW h. The SIR plant was then used to show how these goals could be achievable, taking series-order factors into account, even if the overnight installed cost for a single plant is more expensive compared with a large plant. In another paper the application of passive safety features within designs was considered given the present UK safety licensing framework regarding diversity, redundancy, the single failure criterion, and past precedent. Aspects suggested to require special attention were deliberate depressurization of the primary circuit, secureness of hot shutdown, and the adequacy of natural circulation for containment cooling. The rest of the papers dealt with various aspects of the AP600 and SIR designs. (author)