Reactor physics design

The scope of this subject is here limited to a comparison of the values of the ckling B and the excess infinite multiplication factor kx,- , which are variously derived from critical and subcritical experiments. These two Integral parameters can be measured more or less directly. They are about equally Important to the reactor physics design of low-enrichment graphite reactors, since the real question is the size of the assembly which gives a sufficient margin of excess effective k to allow the reactor to reach the planned operating conditions. 

The reactor physics design of the PFPWR50 has been optimized to achieve the following objectives ... 

The reactor physics design of the CHTR has been performed with the main objectives of achieving high bum-up and a long refueling interval. The reactor fuel consists of... 

Reactors are designed to be inherently safe based on physical principles, supplemented by redundant equipment and special procedures. Nuclear power benefits from the appHcation of the concept of defense in depth, ie, by using fuel form, reactor vessel, building containment, and emergency backup procedures to ensure safety. 

Several of the reactor physics parameters are both measurable and calculable from more fundamental properties such as the energy-dependent neutron cross sections and atom number densities. An extensive database. Evaluated Nuclear Data Files (ENDF), has been maintained over several decades. There is an interplay between theory and experiment to guide design of a reactor, as in other engineering systems. 

The large physical size of the later Magnox stations, such as Wylfa, led to the development of the more compact advanced gas-cooled reactor (AGR) design [31] that could utilize the standard turbine generator units available in the UK, Stainless-steel clad, enriched uranium oxide fuel can tolerate higher temperatures... 

The reactor volume is taken as the volume of the reactor physically occupied by the reacting fluids. It does not include the volume occupied by agitation devices, heat exchange equipment, or head-room above liquids. One may arbitrarily select the temperature, pressure, and even the state of aggregation (gas or liquid) at which the volumetric flow rate to the reactor will be measured. For design calculations it is usually convenient to choose the reference conditions as those that prevail at the the inlet to the reactor. However, it is easy to convert to any other basis if the pressure-volume-temperature behavior of the system is known. Since the reference volumetric flow rate is arbitrary, care must be taken to specify precisely the reference conditions in order to allow for proper interpretation of the resultant space time. Unless an explicit statement is made to the contrary, we will choose our reference state as that prevailing at the reactor inlet and emphasize this choice by the use of the subscript zero. Henceforth,... 

The RC1 is an automated laboratory batch/semi-batch reactor for calorimetric studies which has proven precision. The calorimetric principle used and the physical design of the system are sound. The application of the RC1 extends from process safety assessments including calorimetric measurements, to chemical research, to process development, and to optimization. The ability of the RC1 to generate accurate and reproducible data under simulated plant scale operating conditions may result in considerably reduced testing time and fewer small scale pilot plant runs. 

In practice, every chemical reaction carried out on a commercial scale involves the transfer of reactants and products of reaction, and the absorption or evolution of heat. Physical design of the reactor depends on the required structure and dimensions of the reactor, which must take into account the temperature and pressure distribution and the rate of chemical reaction. In this chapter, after describing the methods of formulating optimization problems for reactors and the tools for their solution, we will illustrate the techniques involved for several different processes. 

While all pyrolysis oil production reactor systems produce similar materials, each reactor produces a unique compound slate. The first decision, especially for a potential chemical or fuel producer, rather than a reactor developer, is to determine what products to make and which reactor system to use. The operating parameters of any reactor system designed to produce pyrolysis oil, especially temperature, can be altered to change the pyrolysis oil product composition and yield. Different feedstocks will produce different pyrolysis oil compositions and by-products, e.g. amorphous silica from rice hulls or rice straw, fatty acids from pine. Finally, feedstock pretreatment and/or catalysis, or reactor-bed catalysis can be used to improve specific product yields (7). Reactor system developers need to examine what they can produce and make this information available to chemical manufacturers and suppliers/owners of biomass feedstocks. This assumes that analysis of die entire liquid product from thermal conversion can be made, including quantitative analysis for any compounds that are being considered for recoveiy. Physical characterization - pH, viscosity, solids content, etc.is also needed. However, what can be produced is of no value, if it cannot be recovered or used economically. This involves examining the trade-offs between yield and current commercial value, recovery costs, and potential commercial value,... 

The selection and design of a reactor for bench-scale kinetic experiments should be considered case by case. It is important to stress, however, that one should not try to build a bench-scale replica of what is believed to be or is the industrial reactor. Industrial reactors are designed to operate a process in a profitable way, which is not the case for experimental reactors. In industrial reactors heat, mass and momentum transport has to occur in an economically justifiable way, leading in general to temperature, concentration and/or pressure gradients inside the reactor. Also, the hydrodynamics can be rather complicated. Fluidized beds, bubble columns and trickle-flow reactors require model equations that involve several physical parameters, besides the intrinsic kinetic parameters. Empirical... 

Hamilton, David P, EDITOR "A Fusion First", Science Scope, Science, Vol. 254, No. 5034, November 15,1991, Page 927 Sweet, William, Super Powers Promote Design Effort for Fusion Demonstration Reactor", Physics Today, January 1988, Page 75 Thon en, D. E., "Charging Their Way Toward Fusion , Science News, December 21, 1985, Page 389... 

The explosion of the nuclear reactor at Chernobyl (spelling changed recently to Chornobyl) in the Ukraine on April 26, 1986 sent radioactive material as far away as Sweden.90 The current death toll is 45. There has been a huge increase in childhood thyroid cancer, with cases as far as 500 km away 91 (U. S. bomb tests have also increased the incidence of thyroid cancers in the western United States.92) There is a 30-km exclusion zone around the plant where no one is allowed to live. This was created by the evacuation of 135,000 people 93 The accident is said to have happened because of combination of the physical characteristics of the reactor, the design of the control rods, human error and management shortcomings in the design, and implementation of the safety experiment. ... 

Thus the constant of proportionality has decreased by about 30% over the life of the core. More accurate relationships between thermal power density and neutron density at different stages of the reactor run may be available from the design calculations or from plant-specific reactor physics data. 

We shall be interested in estimating the fuel-cycle performance of this reactor during a steady-state cycle, in which fresh fuel has a enrichment of 3.2 w/o and spent fuel has a enrichment of around 1.0 w/o and also contains around 0.6 w/o fissile plutonium. The reference design condition used to evaluate effective neutron cross sections and other reactor physics parameters during irradiation is taken to be 2.7 w/o This value, slightly hi er than the arithmetic mean of the fissile content of fuel at the begiiming and end of irradiation, is intended to reflect the hl er cross section of fissile plutonium compared with... 

Nuclear reactors are designed for production of heat, mechanical and electric power, radioactive nuclides, weapons material, research in nuclear physics and chemistry, etc. The design depends on the purposes, e.g. in the case of electric power production the design is chosen to provide the cheapest electricity taking long term reliability in consideration. This may be modified by the availability and economy of national resources such as raw material, manpower and skill, safety reasons, etc. Also the risk for proliferation of reactor materials for weapons use may influence the choice of reactor type. Many dozois of varying reactor concepts have been formulated, so we must limit the discussion in this chapter to a summary of the main variables, and the most common research and power reactors. Fast reactors and some other designs are discussed in Chapter 20. 

We continue with a description of major design features and then a more detailed comparison of cooling circuits and reactor stability. We finish with accounts of resonance, Doppler and xenon poisoning effects and some aspects of reactor physics at Chernobyl as more technical appendices. 

The line between reactor physics and reactor engineering is not very distinct, and Wigner laid much of the foundation for both fields. Thus during that extraordinary three years at Chicago (1942 to 1945), and the year at Clinton (1946-47), Wigner invented many of the techniques that we now teach in textbooks of reactor design. (Papers 27, 28, 29, 30)... 

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