Multimodular System Research Articles

Considerations in the control of PWR-type multimodular reactor plants

Issues in the control of PWR-type multimodular reactor plants are discussed with emphasis on the need for operation under conditions of unbalanced loads, operating strategies for both single- and multireactor systems, and the coordinated adjustment of power and temperature. One defining characteristic of a multimodular plant is that each unit will probably be loaded differently so as to compensate for the effects of varying maintenance outages and, if desired, to stagger refuelings. A second characteristic is interdependency in that, with several reactors connected to a common turbine, a change in any one unit will propagate to the others. The combination of these two factors makes operation of a multimodular plant differ from that of existing single-reactor ones. For example, conventional sliding-T/sub ave/ load maps cannot be applied directly to a multimodular system because, with the exception of the highest-powered unit, each reactor's temperature will be a function of not only its power level but also that of the most heavily loaded one. Similarly, withdrawal of the control rods in a fully loaded PWR will, in the presence of a large negative temperature coefficient, cause hot and cold leg temperatures to rise but leave power and core /spl Delta/T unchanged. In a multimodular system, there will be a shift in power to the affected reactor. These and other differences in the behavior of multimodular and single-reactor systems are delineated. The paper concludes with some practical suggestions on the operation of PWR-type multimodular plants. >

Effect of time-of-flight bunching on efficiency of light-ion-beam inertial-confinement-fusion transport schemes

The Laboratory Microfusion Facility (LMF) has been proposed for the study of high-gain, high-yield inertial-confinement-fusion targets. The light-ion LMF approach uses a multimodular system with applied-B extraction diodes as ion sources. A number of ion-beam transport and focusing schemes are being considered to deliver the beams from the diodes to the target. These include ballistic transport with solenoidal lens focusing, z-discharge channel transport, and wire-guided transport. The energy transport efficiency ηt has been defined and calculated as a function of various system parameters so that point designs can be developed for each scheme. The analysis takes into account target requirements and realistic constraints on diode operation, beam transport, and packing. The effect on ηt of voltage ramping for time-of-flight beam bunching during transport is considered here. Although only 5 mrad microdivergence calculations are presented here, results for bunching factors of ≤3 show that transport efficiencies of ≳50% can be obtained for all three systems within a range of system parameters which seem achievable (i.e., for diode microdivergence within 5–10 mrad, for diode radius within 10–15 cm, and for diode-ion-current density within 2–10 kA/cm2). In particular, the point design for the baseline LMF system using ballistic transport with solenoidal lens focusing and a bunching factor of 2 was calculated to have ηt=84%. Other factors affecting the overall system efficiency, but not included in the analysis, are also identified and estimated.