Commercial Power Reactors Research Articles

A thermonuclear fusion power program for Israel

Although lacking in financial and physical resources, Israel has a large base of scientific and technological talent that can be organized for the purpose of producing commercial fusion power reactors, thus allowing Israel to attain energy independence and acquiring a monetary inflow through royalties and reactor export. The limited partnership would be suitable for financing a significant portion of the project. Economic feasibility can be estimated through the use of one or more of the approaches supplied by the calculus of variations, cardinal utility theory, catastrophe theory, and noncooperative game theory.

New Directions in Tokamak Reactors

It has been five years or more since the last major studies were completed of the tokamak as a commercial power reactor. During that time there have been major physics and technology developments in magnetic fusion as well as programmatic and political changes. There exists a significant number of new ideas which can substantially improve the tokamak concept as a power reactor. This paper outlines some major goals and new directions for a series of scoping studies - Tokamak Power Systems Studies - which are currently in progress.

Fracture toughness characterization of irradiated, low upper shelf welds

A data base of J − R curve trends is being established for irradiated, light-water reactor pressure vessel steels of low upper shelf toughness. R-curve trends have been developed for several welds made with Linde 80 flux and containing a high copper impurity which enhances the sensitivity to irradiation embrittlement. Tests were conducted using compact toughness specimens of 12.5 mm to 100 mm thickness. These data provide the materials properties necessary for a tearing instability analysis of postulated accident conditions in certain commercial power reactors. Irradiation decreased the level of the R curve significantly in most cases. Furthermore, the average value of tearing modulus ( T avg) was a more discriminating indicator of toughness degradation than the crack initiation toughness ( J Ic). Temperature-dependent correlations between the R-curve parameters ( J Ic, T avg) and Charpy-V ( C v) upper shelf energy have been suggested here and in other programs. This finding could enhance the significance of C v reactor surveillance data with respect to structural integrity. However, J Ic and T avg have demonstrated an inverse relationship with temperature which is not reflected in C v upper shelf energy and this must be taken into account in the development of correlations.

Numerical analysis of electromagnetic stress induced in bellows for a magnetic fusion reactor

The use of bellows in a magnetic fusion reactor gives, in many cases, more efficient penetration of the poloidal electric field and very efficient plasma heating in the first phase of operation. This is because bellows sections lead to higher electrical resistance of the vacuum vessel. There are many examples of its application to tokamak type experimental devices such as TFTR, JT-60 and so on. In addition to its higher electrical resistance, the bellows has an ability to absorb large deformation due to thermal expansion and radiation creep, and thus has been applied to the design of a first wall configuration in some conceptual designs of a commercial power reactor. Its application to a vacuum vessel of the Reacting Plasma machine, which was proposed by the Institute of Plasma Physics of Nagoya University, was examined for circular plasmas. When applying the numerical analysis to the bellows, a computational difficulty occurs. Too many unknows appear in a mesh division with a general shell element and these are not easily handled. Therefore in the present paper a finite element code is made to consider an axisymmetric structure loaded by nonsymmetric forces. In the code various types of electromagnetic forces are taken into account. These include the diamagnetic electromagnetic force, the toroidal-current-induced-electromagnetic forces, the electromagnetic forces due to toroidal coil current change and saddle shaped electromagnetic forces. Aluminum is selected as bellows material because of its low activation nature but there are large induced currents because of its higher electrical conductivity. Results of stress analysis show that a leak of the saddle shaped current into the thick aluminum vacuum vessel generates maximum bending stress near a joint between the bellows and the vessel. Stress due to other types of electromagnetic force are significantly smaller.

External Initiators in Probabilistic Reactor Accident Analysis—Earthquakes, Fires, Floods, Winds

This article discusses the methodologies presently available for analyzing the contribution of “external initiators” to overall risks in the context of PRA (probabilistic risk assessment) of large commercial nuclear power reactors. “External initiators” include earthquakes, fires and floods inside the plant, external floods, high winds, aircraft, barge, and ship collisions, noxious or explosive gases offsite, and so on. These are in contrast to “internal initiators” such as active or passive plant equipment failures, human errors, and loss of electrical power. The ability to consider external initiators within PRA has undergone major advances in recent years. In general, uncertainties associated with the calculated risks from external initiators are much larger than those associated with internal initiators. The principal uncertainties lie with development of hazard curves (such as the frequency of occurrence of an event exceeding a given size: for example, the likelihood of a hurricane with winds exceeding 125 knots). For assessment of earthquakes, internal fires and floods, and high winds, the methodology is reasonably mature for qualitative assessment but not for quantitative application. The risks from other external initiators are generally considered to be low, either because of the very long recurrence time associated with the events or because the plants are judged to be well designed to withstand them.

Effects of acidification and complexation from radiolytic reactions on leach rates of SYNROC C and nuclear waste glass

Previous work1 has shown that γ-radiation induced enhancement of leach rates from high-level radioactive waste (HLW) solids can be attributed to radiolytic acidification of the aqueous solution and to radiolytic formation of organic complexing species, for example, (COOH)2, HCOOH. Barkatt et al.1 compared the leach resistance of three HLW glasses and SYNROC D (specifically designed for incorporation of US defence wastes2) and found that, at low pH and with complexing agents, higher alumina contents in the waste form gave large enhancement of leach rates. Specifically, in acid solution, the elemental leach rates for SYNROC D were increased relative to the glasses by factors between 20 and 1,200. The formulation of SYNROC C, designed by Ringwood2 for incorporation of reprocessed waste from commercial power reactors, was not tested in these conditions. We report here that SYNROC C is considerably more resistant than the standard HLW glass PNL 76–68 to acid attack and to possible complexation reactions between 90 and 150 °C, despite an alumina content in the formulation that is much higher than that for PNL 76–68. The Al content of SYNROC C is much lower than that of SYNROC D (Table 1) and it is largely present in the hollandite phase after hot pressing. No aluminosilicate phases are formed in SYNROC C and, for this reason, the pH dependence is much less marked. These results are significant in assessing the effects of changes induced by the ionizing radiation to which the HLW solid and solution will be exposed during geological isolation.

Bayesian Estimation of Core-Melt Probability

A very simple application of the canonical Bayesian algorithm is made to the problem of estimation of the probability of core melt in a commercial power reactor. An approximation to the results of the Rasmussen study on reactor safety is used as the prior distribution, and the observation that there has been no core melt yet is used as the single experiment. The result is a substantial decrease in the mean probability of core melt--factors of 2 to 4 for reasonable choices of parameters. The purpose is to illustrate the procedure, not to argue for the decrease.

The toroidal field coil support structure for a commercial power reactorII. Detailed design studies

The toroidal field coil support structure design for a commercial power reactor is described. The design, developed on the basis of techniques reported in a companion paper, has some novel features, such as serrated joints and a structure composed of welded forgings. Particular attention is paid to manufacturing and assembly procedures and only modest extrapolations from present techniques are envisaged. Finally, a simple eddy current analysis is reported and outstanding areas of uncertainty in the design are discussed.

The toroidal field coil support structure for a commercial power reactor: I: stress analysis

The stress analysis techniques necessary for developing a toroidal field coil support structure design for a commercial power reactor are described. Simple analytical techniques, beam element analysis and finite element modelling all have a part to play. The power of simple techniques in guiding a number of design choices is emphasized and its accuracy indicated by reference to a finite element analysis of the finally developed structure.

The toroidal field coil support structure for a commercial power reactorI: Stress analysis

The stress analysis techniques necessary for developing a toroidal field coil support structure design for a commercial power reactor are described. Simple analytical techniques, beam element analysis and finite element modelling all have a part to play. The power of simple techniques in guiding a number of design choices is emphasized and its accuracy indicated by reference to a finite element analysis of the finally developed structure.

The toroidal field coil support structure for a commercial power reactor: II. detailed design studies

The toroidal field coil support structure design for a commercial power reactor is described. The design, developed on the basis of techniques reported in a companion paper, has some novel features, such as serrated joints and a structure composed of welded forgings. Particular attention is paid to manufacturing and assembly procedures and only modest extrapolations from present techniques are envisaged. Finally, a simple eddy current analysis is reported and outstanding areas of uncertainty in the design are discussed.

Cs and I release source terms from irradiated LWR fuel

Knudsen cell experiments have been performed to investigate the status of fission cesium and iodine in irradiated UO 2. For those experiments UO 2 samples with a burnup = 33 GWd/t(U) are taken from PWR fuel rods unloaded from a commercial power reactor. The temperatures of a noticeable release decreases from 1800°C at very low burnup to 1400°C at 33 GWd/t(U). The time pattern of Cs and I exhalation is composed of a transient release depending on the accessible surface and temperature followed by a release which mainly depends on the temperature and the square root of time. The temperature dependence of the second release can be described by an Arrhenius function using an activation energy quite similar to that known for the fission gas release. The characteristic release over time pattern is nearly identical for Cs and I exhalation. Also the ratio of release over inventory is nearly the same for both fission products.

A Solid Breeder Blanket and Power Conversion System for the Mirror Advanced Reactor Study (MARS)

A solid-breeder blanket has been designed for a commercial fusion power reactor based on the tandem mirror concept (MARS). The design utilizes lithium oxide, cooled by helium which powers a conventional steam electric generating cycle. Maintenance and fabricability considerations led to a modular configuration 6 meters long which incorporates two magnets, shield, blanket and first wall. The modules are arranged to form the 150 meter long reactor central cell. Ferritic steel is used for the module primary structure. The lithium oxide is contained in thin-walled vanadium alloy tubes. A tritium breeding ratio of 1.25 and energy multiplication of 1.1 is predicted. The blanket design appears feasible with only a modest advance in current technology.

Environment and Safety Major Goals for MARS

The Mirror Advanced Reactor Study (MARS) is a conceptual design study for a commercial fusion power reactor. One of the major goals of MARS is to develop design guidance so that fusion reactors can meet reasonable expectations for environmental health and safety. One of the first steps in the assessment of health and safety requirements was to examine what the guidelines might be for health and safety in disposal of radioactive wastes from fusion reactors. Then, using these guidelines as criteria, the impact of materials selection upon generation of radioactive wastes through neutron activation of structural materials was investigated. A conclusion of this work is that fusion power systems may need substantial engineering effort in new materials development and selection to meet the probable publicly acceptable levels of radioactivity for waste disposal in the future.

Conceptual Study of a Lithium Lead Eutectic Blanket for a Power Reactor

In the frame of the recent CEA studies aiming at the evaluation and the comparison of various candidate blanket concepts in view of their possible extrapolation to the commercial power reactor, the present work examines the potential interest of a 15 MPa pressurized water cooled Li/sub 17/Pb/sub 83/ blanket. After a brief presentation of the main reactor parameters, the body of the paper is devoted to the engineering optimization of the blanket arrangement, in terms of tritium breeding (minimization of the water content), coolant manifolding (minimum coolant cross section, minimum number of connections and easy access for maintenance) and adaptation to the steep power and irradiation gradients, typical of Li/sub 17/Pb/sub 83/ and crucial for a power reactor. Poloidal cooling direction, long heated length and segmentation into the radial direction (breeder rows) provide some answers to these preoccupations and could be recommended for the next step liquid blanket studies, in order to anticipate the requirements of the commercial reactor.

Americas Finest

Americas finest 330 MW commercial nuclear power reactor stands in the plains beneath the Rockies at Fort St. Vrain, Colorado. Reprinted with permission from "Access to Energy," P.0. Box 2298 Boulder, CO 80306.

Proposal for a possible use of fusion power for hydrogen production within this century

The article describes the possibility of building a commercial fusion power reactor before the turn of the century. The main elements of the system proposed are known from the PACER Project which is based on the explosive DD-fusion process. Since practically, only existing technology has to be applied, it seems that PACER offers the quickest way to peacefully harnessing fusion energy on a large scale. The article shows how such reactors could be embedded in a series of energy parks, scattered all around the world, to meet the energy requirements of a “30 TW world” in the forthcoming non-fossil era. Furthermore, the article addresses the breeding of fissile materials and especially the production of electrolytic hydrogen. In the latter case, large amount of deuterium can be produced as a by-product in the electrolytic process. The original proposal here is that only a small part of this deuterium must be recycled to get enough fusion fuel for the DD-energy source. The system can be designed in such a way that either the heat alone, the bred fuel alone, or both together could be used. Reactors based on the described DD-fusion principle of delivering both bred fissile fuel and hydrogen gas are particularly well suited for remote sites. “If you look into the seeds of time and say which grain will grow and which will not, speak then to me” (William Shakespeare, Macbeth)

On the space dependence of neutron density noise and the problem of malfunction localization

The space dependence of neutron noise is investigated as a function of reactor size and frequency of excitation, with regard to malfunction localization. An analytical expression for the relative importance of the higher harmonics of the Greens function is given and evaluated for typical sizes of commercial power reactors. It is concluded that localization of thermal hydraulic excitations through neutron noise signals is practically impossible. The case of rod vibration excitations is examined in detail. A 3-dimensional analytical expression is derived for the neutron density response to rod vibrations; it is concluded that rod malfunction localization through neutron noise is not a practical proposition.

Safety related tritium research required to support commercial fusion power reactors

Safety related tritium research required to support commercial fusion power reactors

Structural design features for commercial fusion power reactor magnet systems

The evolution of structural design features for commercial fusion power reactor magnet systems is discussed. Changing concepts in plasma physics and impurity control, new data on radiation damage in materials and developments in the maintainability and repairability of the magnet systems are the driving influences in this evolution. Generic problems in the magnet designs are discussed for several proposed magnetic confinement system configurations, including tokamaks, tandem mirrors, the Elmo Bumpy Torus, and the reversed field theta pinch. These systems are compared on the basis of how efficiently the magnets make use of structural materials. A measure of the effectiveness of a magnet system is found by determining the ratio of net electric power output from the reactor to the stored energy in the magnetic fields produced by the magnet coils in a given system. The stored energy in the magnetic field can then be used to establish a minimum structural volume and mass by use of the virial theorem. Experience with coil types such as solenoids, toroids, Yin-Yang, etc. has established factors by which the minima must be multiplied to yield anticipated volumes and masses of realistic magnet systems. These initial, admittedly approximate, calculations allow designers to estimate early in the process the contribution of the magnet systems to the overall cost of a fusion reactor. As work progresses these estimates can be used to indicate the degree to which the designer is making effective use of the structural material. Basic rules for effective placement of structure, common to all magnet systems, are also discussed in detail. Factors are presented which make it possible to compare structural savings to the cost of researching the parameters involved in the stability of superconductors.