Pressurized water reactors fuel cycle

The Pressurized Water Reactor (PWR) reload core optimization problem, though easily stated, is far from easily solved. The designer s task is to identify the arrangement of fresh and partially burnt fuel (fissile material) and burnable poisons (BPs) (control material) within the core which optimizes the performance of the reactor over that operating cycle (until it again requires refueling), while ensuring that various operational (safety) constraints are always satisfied. 

Abstract The chapter is devoted to the practical application of the fission process, mainly in nuclear reactors. After a historical discussion covering the natural reactors at Oklo and the first attempts to build artificial reactors, the fimdamental principles of chain reactions are discussed. In this context chain reactions with fast and thermal neutrons are covered as well as the process of neutron moderation. Criticality concepts (fission factor 77, criticality factor k) are discussed as well as reactor kinetics and the role of delayed neutrons. Examples of specific nuclear reactor types are presented briefly research reactors (TRIGA and ILL High Flux Reactor), and some reactor types used to drive nuclear power stations (pressurized water reactor [PWR], boiling water reactor [BWR], Reaktor Bolshoi Moshchnosti Kanalny [RBMK], fast breeder reactor [FBR]). The new concept of the accelerator-driven systems (ADS) is presented. The principle of fission weapons is outlined. Finally, the nuclear fuel cycle is briefly covered from mining, chemical isolation of the fuel and preparation of the fuel elements to reprocessing the spent fuel and conditioning for deposit in a final repository. 

Kurka, G., Harrer, A., Chenebault, P Fission product release from a pressurized water reactor defective fuel rod Effect of thermal cycling. Nucl. Technology 46, 571-581 (1979) Leuthrot, C., Beslu, P Release of volatile fission products for commercial PWRs in transient conditions including load follow. Proc. 4. BNES Conf. Water Chemistry of Nuclear Reactor Systems, Bournemouth, UK, 1986, Vol. 2, p. 137-140 Lewis, B. J. Fission product release from nuclear fuel by recoil and knockout. J. Nucl. Materials 148, 28-42 (1987)... 

Reactivity changes and plutonium isotopic compositions were first examined for a commercial pressurized water reactor (PWR) operating on a low enrichment (3.2 wt% equilibrium fuel cycle. The results aided in understanding the significance of a number of approximations made in this assessment. The results also provided some perspective on the plutonium composition in spent conunercial reactor fuels. 

Pressurized Water Reactor. The PWR contains three coolant systems (1) the primary system, which removes heat from the reactor and partially controls nuclear criticality (2) the secondary system, which transfers the heat from the primary system via the steam generator to the turbine-driven electric generator (3) the service water system (the heat sink), which dumps the residual coolant energy from the turbine condenser to the environment. The service water is recirculated from a river, lake, ocean, or cooling tower. In the primary system (Fig. 31.21), dissolved boron is present to control nuclear criticality. Fixed-bed ion exchange units are used to maintain the water quality in both the primary and the secondary systems. In addition, the chemical and volume control system reduces boron concentration during the power cycle to compensate for fuel burnup. These operations are carried out continuously though bypass systems. A more complete... 

Eig. 8. Cost of electricity (COE) comparison where represents capital charges, Hoperation and maintenance charges, and D fuel charges for the reference cycles. A, steam, light water reactor (LWR), uranium B, steam, conventional furnace, scmbber coal C, gas turbine combined cycle, semiclean hquid D, gas turbine, semiclean Hquid, and advanced cycles E, steam atmospheric fluidized bed, coal E, gas turbine (water-cooled) combined low heating value (LHV) gas G, open cycle MHD coal H, steam, pressurized fluidized bed, coal I, closed cycle helium gas turbine, atmospheric fluidized bed (AEB), coal J, metal vapor topping cycle, pressurized fluidized bed (PEB), coal K, gas turbine (water-cooled) combined, semiclean Hquid L, gas turbine... 

It has been proposed that some of the natural uranium needed to fuel a pressurized-water nuclear power plant be obtained by extracting uranium from seawater used to cool the plant. If the seawater temperature rise is lO C and the reactor and fuel-cycle conditions are as given in Frg. 3.31, how many kilograms of uranium per year could be recovered at 80 percent yield from cooling water What fraction is this of the armual fuel requirement of the reactor ... 

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). 

The supercritical-water-cooled reactor (SCWR) ( Fig. 58.21) system features two fuel cycle options the first is an open cycle with a thermal neutron spectrum reactor the second is a closed cycle with a fast-neutron spectmm reactor and full actinide recycle. Both options use a high-temperature, high-pressure, water-cooled reactor that operates above the thermodynamic critical point of water (22.1 MPa, 374°C) to achieve a thermal efficiency approaching 44%. The fuel cycle for the thermal option is a once-through uranium cycle. The fast-spectrum option uses central fuel cycle facilities based on advanced aqueous processing for actinide recycle. The fast-spectrum option depends upon the materials R D success to support a fast-spectrum reactor. 

Most studies of the time evolution of the fuel cycle and the evolving mix of reactor types during future decades have been based on global (or national) nuclear energy demand scenario analyses which, up to now, have assumed the use of traditional reactor types, such as LWRs, pressurized heavy water reactors (PHWRs), and fast breeder reactors (FBRs). Possible implications of small reactors without on-site refuelling on the transition timing and strategy have not yet been assessed extensively. 

The heavy water reactor was developed in Canada and is known as the CANDU reactor. The D2O is used as both coolant and moderator. The relative moderating efficiency of various materials is given in Table 7.11. Because of the superior moderating property of D2O, it is possible to use natural uranium as the fuel in the form of UO2 pellets in zircaloy tubes. This makes the CANDU one of the best designed reactors in the world. The coolant cycle and the moderator are separate flow circuits shown in Fig. 7.6. The fuel elements in the pressure tubes and the D2O flow is shown in Fig. 7.7 where the coolant is at about 293°C and 100 atm pressure. The moderator is at lower temperature. The efficiency is rated at 29%. ... 

---