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The investigation of time-dependent power requirements for a future nuclear fusion reactor is part of the systems integration task for the European Fusion Programme. A pulsed DEMO will require intermittent and continuous electrical power to operate the various plant systems. For example, the heating and current drive system will require power during I p start-up, heating, plasma burn and I p ramp-down phases. This paper presents the modelling of these power requirements over the whole pulse cycle for all plant systems in the systems code PROCESS. In the EUROfusion baseline case the continuous power requirements are −290 MW and are dominated by the primary coolant pumping requirements. The total intermittent power requirements range from −50 to −375 MW. The time between pulses strongly influences the average plant net electrical power production and for a power plant would have to be minimised to stay commercially viable. The EUROfusion DEMO baseline is estimated to produce enough electrical power to meet the machine's aims given the current burn time, time between pulses and power requirements. [ABSTRACT FROM AUTHOR]

Tritium production is of critical importance to prospective DT fusion power plants. Lithium ceramic and beryllium based solid-type breeder blankets are an option for supplying the tritium required to sustain the DT plasma. This research investigates the time-varying tritium production in solid breeder blankets with different compositions. The breeder fraction was varied in conjunction with the Li 6 enrichment. The parameter study considered 198 different blanket compositions for three blanket thicknesses. The cheapest configuration capable of meeting the tritium requirements were found. The cost of Li 4 SiO 4 (including Li 6 enrichment) and Be 12 Ti were considered. The time-varying tritium production of each blanket configuration was simulated using the interface code, FATI, that couples the radiation transport code MCNP 6 with the inventory code FISPACT-II. Economical blanket configurations capable of self-sufficiency were found. The cost of producing excess tritium for start-up inventories was found to be between $18,000 and $27,000 per g. Fitting functions to predict the time-averaged tritium breeding fraction and the tritium inventory at five years, were obtained for inclusion in the PROCESS systems code. PROCESS is now able to consider different breeding blanket compositions and thicknesses when assessing the engineering, physics and economic feasibility of reactor designs. [ABSTRACT FROM AUTHOR]

Abstract: We outline a speculative design for a photodetachment neutraliser for a negative ion neutral beam system, with neutralisation efficiency of 95% or more. The practical difficulties are enormous. The ion beam must pass through an optical cavity capable of reflecting the light many times. For 500 reflections, the laser optical power output ∼800kW, giving circulating power ∼400MW. All sources of light loss combined need to be kept to 0.2% or less per pass. The losses due to photodetachment itself, and due to Thomson scattering in the beam plasma are negligible. A key task is to maintain the reflectance of the mirrors above 99.97% for long periods of operation, protecting all the components from thermal and neutron damage, and from caesium, sputtered atoms and other contamination. A diode-pumped Nd-doped YAG laser can have overall electrical-to-light (“wall-plug”) efficiency up to 25%. A DEMO concept reactor such as the EU Power Plant Conceptual Study (PPCS) Model B requires 270MW heating power. If this is all provided by neutral beams, then a laser neutraliser might reduce the electrical power consumption for this from 900MW to 520MW. [ABSTRACT FROM AUTHOR]

Beryllium (Be) is a precious resource with many high value uses, the low energy threshold (n,2n) reaction makes Be an excellent neutron multiplier for use in fusion breeder blankets. Estimates of Be requirements and available resources suggest that this could represent a major supply difficulty for solid-type blanket concepts. Reducing the quantity of Be required by breeder blankets would help to alleviate the problem to some extent. In addition, it is important that the reduction in the Be quantity does not diminish the blanket's performance in key aspects such as the tritium breeding ratio (TBR), energy multiplication and peak nuclear heating. Mixed pebble bed designs allow for the multiplier fraction to be varied throughout the blanket. This neutronics study used MCNP 6 to investigate linear variations of the multiplier fraction in relation to blanket depth, in order to better utilise the important multiplying Be(n,2n) and breeding reactions. Blankets with a uniform multiplier fraction showed little scope for reduction in Be mass. Blankets with varying multiplier fractions were able to simultaneously use 10% less Be, increase the energy amplification by 1%, reduce the peak heating by 7% and maintaining a sufficient TBR when compared to the performance achievable using a uniform composition. [ABSTRACT FROM AUTHOR]

High energy neutrons produced in future fusion reactors will cause significant transmutation reactions in the breeder blanket, including the important tritium breeding reactions. The reaction rate for a given reaction type depends on the neutron spectrum and material properties. The inventory consequences for tritium production of a solid-type breeder blanket are discussed in this paper. A DEMO fusion reactor with 19 homogeneous breeder blanket modules made of Eurofer, helium, Be 12 Ti and Li 4 SiO 4 , with enriched Li 6 content. Each blanket module was segmented radially in order to analyse the time-dependent reaction rate as a function of depth. The resolution of radial segmentation was varied and 5 radial divisions were found to be sufficient to accurately model the tritium inventory. Time-dependent tritium production was simulated with the use of the interface code, FATI, which couples radiation transport code MCNP 6 with the inventory code FISPACT-II. The simulated results show how the tritium production varies over the expected lifetime of the blanket. The overall tritium production of the solid-type blanket decreases as the Li 6 and Li 7 are burnt up. The effect of Li 6 burn-up in the breeder zones nearest to the plasma is identified as the main contributing factor to the decreasing tritium production of the whole breeder blanket. [ABSTRACT FROM AUTHOR]