Page 142 - Dynamics and Control of Nuclear Reactors

CHAPTER

12
Pressurized water reactors

12.1 Introduction
This chapter addresses generation II and III pressurized water reactors (PWRs). Pres-
surized water reactors are the most common type in the U.S. They are also used
extensively in other countries. Commercial PWR development followed successful
development of PWRs for naval applications. There has been little change in the
basic design of PWR power plants and their control systems since their initial imple-
mentation in the mid-twentieth century. The early designers knew what they
were doing.

12.2 PWR characteristics [1–3]
Three different PWR manufacturers in the U.S. supplied Generation II and III
nuclear power plants. Westinghouse Electric Company and Combustion Engineering
provided plants with U-tube steam generators (UTSG), and the Babcock and Wilcox
(B&W) Company provided plants with once through steam generators (OTSG). The
Russian VVER pressurized water reactor uses horizontal shell-and-tube steam
generators.
Fig. 12.1 shows the layout of a typical PWR plant. A PWR with U-tube steam
generators is chosen to show the components in a PWR plant.
The primary system consists of a reactor vessel, hot leg and cold leg piping, a
pressurizer, and reactor coolant pumps (RCP). The U-tube steam generator (UTSG)
connects the primary system with the secondary system or the balance-of-plant
(BOP) system. The BOP system includes the steam turbine, an electrical generator,
steam re-heaters, moisture separators, feedwater heaters, and a condenser. The reac-
tor vessel and the steam generators are located in a large containment building. The
turbine-generator system and the BOP components are located in a separate building.
Design parameters for a typical 1150 MWe four-loop PWR (Westinghouse PWR)
appear in Appendix A.
The primary water ( 550°F) from cold leg pipes enters the reactor vessel near
the top, flows down through an annular region between the inner wall of the reactor
vessel and a shroud around the core (called the core barrel) to the bottom of the ves-
sel, and then flows up through the core, thereby removing heat from the fuel.
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