Supercritical pressure reactor

From the beginning of the conceptual study on supercritical water cooled reactors, several plant transient analysis codes have been developed, modified, and applied to them [1-9]. The general name of these codes is Supercritical Pressure Reactor Accident and Transient analysis code (SPRAT). SPRAT mainly calculates mass and energy conservations, fuel rod heat conduction, and point kinetics. The relation among these calculations is shown in Fig. 4.1. SPRAT can deal with flow, pressure, and reactivity induced transients and accidents at supercritical pressure. The flow chart is shown in Fig. 4.2. 

In this appendix, a brief summary is provided on the design concepts of supercritical pressure reactors (SCRs), which are cooled either by water or steam, nuclear superheaters, and steam cooled fast reactors from the 1950s to the mid 1990s. 

Appendix B Review of High Temperature Water and Steam Cooled Reactor Concepts 623 Table B.l Characteristics of supercritical pressure reactors (Taken from ref. [3])... 

Supercritical pressure reactor concepts and nuclear superheaters were studied as reactor concepts by WH and GE in the 1950s and 1960s when LWR design and safety had not yet been established. New supercritical pressure reactor concepts emerged in the 1990s from Japan, Russia, and Canada as innovative water cooled reactors. Steam cooled FBRs were studied in the 1950s and 1960s as an alternative to liquid metal fast breeder reactors. These steam cooled FBRs require a... 

Oka, Y. Physics of supercritical-pressure light water cooled reactors. Proc. 1998 Frederic Joliot Summer School in Reactor Physics, Caderache, France, and references cited herein, 1998 240-259 pp. 

Figure 10.8 shows the effect of the reaction pressure on TOC in the liquid phase. The reaction pressure was estimated from the water density in the reactor. The water density was varied to give corresponding pressures from 22 to 35 MPa. In the supercritical pressure region, lower pressure favors a reduction of the TOC in the liquid phase. 

Figure 1. Supercritical flow reactor. Key (I) Mettler balance (2) flask with 1 0 (filtered and deaerated) (3) HPLC pump (4) bypass (three-way) valve (5) feed cylinder (6) weather balloon with feed solution (7) probe thermocouple (type K) (8) ceramic annulus (9) Hastelloy C-276 tube (10) entrance cooling jacket (11) entrance heater (12) furnace coils (13) quartz gold-plated IR mirror (14) window (no coils) (15) guard heater (16) outlet cooling jacket (17) ten-port dualloop sampling value (18) product accumulator (19) air compressor (20) back-pressure regulator and (21) outflow measuring assembly.

The pressure of the reactor must also be defined, and acronyms APCVD, LPCVD, and SCF-CVD are used to denote ambient, in vacuo, and supercritical pressure conditions within the deposition chamber, respectively. In general, the resultant... 

Figure C.2. Photograph of the supercritical fluid system used for nanoparticle synthesis. Shown is the 300-mL high-pressure reactor (A), with pressure/temperature controllers (B). The system is rated for safe operation at temperatures and pressures below 200°C and 10,000psi, respectively. The vessel may be slowly vented, or exposed to a dynamic CO2 flow, using a multiturn restrictor valve (C), which provides a sensitive control over system depressurization, allowing for the collection of C02-solvated species in the stainless steel collector (D). For deposition using the rapid expansion of tlie supercritical solution (RESS), nanoparticles were blown onto a TEM grid that was placed under the stopcock below D. Also shown is the cosolvent addition pump (E) used for the synthesis of aluminum oxide nanoparticles, capable of delivering liquids into the chamber against a back-pressure of <5,000 psi.

Prepare a 0.05 M copper solution using CuCl2-2H20 in absolute ethanol (200 proof), and transfer this to a clean 8-mL vial. Also prepare a 0.04 M aqueous solution of 1,4-phenylenediamine, and transfer to a second clean 8-mL vial. Position the vials within the supercritical fluid reactor, avoiding any contact between the solutions. With consultation with your instructor, allow the system to reach the desired pressure and temperature. Maintain these conditions for 45 min. 

Figure 1 is a schematic of one of the two supercritical flow reactors used in this work. The system is first brought up to the operating pressure by an air compressor. An HPLC pump forces the reactant solution through the reactor, the ten-port valve and dual-loop sampling system, and into the product accumulator, where the flow of products displaces air through a back-pressure regulator. The reactant inflow is rapidly heated to reaction temperature by an electric entry heater/water jacket combination, and maintained at isothermal conditions by a Transtemp Infrared furnace and an exit electric heater/water jacket combination. 

Most of the data available in the literature are for subcritical conditions. Corrosion studies of iron alloys in supercritical water have not been reported. For supercritical fluid extraction and corrosion studies, a supercritical fluid reactor system for temperatures up to 530 C and pressures up to 300 atm was constructed. This system was used to determine the electrochemical behavior of type 304 stainless steel (304 S.S.), 316 S.S., 1080 carbon steel (1080 C.S.), and pure iron in supercritical water. 

Power Production. Steam cycles for generation of electric power use various types of boilers, steam generators, and nuclear reactors operate at subcritical or supercritical pressures and use makeup and often also condensate water purification systems as well as chemical additives for feedwater and boiler-water treatment. These cycles are designed to maximize cycle efficiency and reliability. The fuel distribution of sources installed in the United States from 1990—1995 are as follow coal, 45% combined cycle, 27% miscellaneous, 14% nuclear, 11% solar, oil, and geothermal, 1% each and natural gas, 0.3%. The 1995 summer peak generation in the United States was 620 GW (26). The combined cycle plants are predominantly fired by natural gas. The miscellaneous sources include bagasse, black liquor from paper mills, landfill gas, and refuse (see Fuels frombiomass Fuels fromwaste). 

Because oxygen, carbon dioxide, methane, and other alkanes are completely miscible with dense supercritical water, combustion can occur in this fluid phase. Both flameless oxidation and flaming combustion can take place. This leads to an important application in the treatment of organic hazardous wastes. Nonpolar organic wastes such as polychlorinated biphenyls (PCBs) are miscible in all proportions in supercritical water and, in the presence of an oxidizer, react to produce primarily carbon dioxide, water, chloride salts, and other small molecules. The products can be selectively removed from solution by dropping the pressure or by cooling. Oxidation in supercritical water can transform more than 99.9 percent of hazardous organic materials into environmentally acceptable forms in just a few minutes. A supercritical water reactor is a closed system that has no emissions into the atmosphere, which is different from an incinerator. 

Ionic liquids are a new and remarkable class of designer solvents [9] with negligible vapor pressure for chemical syntheses because their properties such as solubility, density, refractive index, and viscosity can be tuned to suit specific requirements [10, 11], Water is a relatively more environmentally friendly alternative for organic synthesis, but its appHcation has been limited so far [6]. Supercritical carbon dioxide is yet another clean solvent but it generally requires a high-pressure reactor [12],... 

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