Pressurized Water Reactor

Pressurized Water Reactor
NRC · Public domain · source
Name	Pressurized Water Reactor
Caption	Schematic diagram of a large commercial pressurized water reactor
Type	Light-water reactor
First crit	1950s
Developer	Westinghouse Electric Company, Babcock & Wilcox, Combustion Engineering
Status	Commercial deployment worldwide

Pressurized Water Reactor is a class of light‑water nuclear reactor that uses liquid water as both coolant and neutron moderator while maintaining the primary coolant under high pressure to prevent boiling. Developed in the mid‑20th century by companies such as Westinghouse Electric Company, Babcock & Wilcox, and Combustion Engineering, the design has been implemented in commercial fleets operated by utilities including EDF (Électricité de France), Exelon Corporation, and Tokyo Electric Power Company. The design underpins reactor types in countries like the United States, France, Russia, China, and South Korea and features prominently in regulatory frameworks managed by bodies such as the Nuclear Regulatory Commission and the International Atomic Energy Agency.

Overview

The reactor class traces lineage to experimental prototypes such as the Shippingport Atomic Power Station and military reactors aboard USS Nautilus (SSN-571) and USS Enterprise (CVN-65), and later commercial deployments in reactor models by Westinghouse Electric Company and Combustion Engineering. Global adoption accelerated following programs in France and Japan and designs evolved through collaborations involving AREVA and Mitsubishi Heavy Industries. The architecture centers on a high‑pressure primary loop, a steam generator interface with a secondary loop, and containment structures influenced by events like Three Mile Island accident and Chernobyl disaster, which drove regulatory changes across institutions including the Nuclear Regulatory Commission and the International Atomic Energy Agency.

Design and Components

Primary components include the reactor pressure vessel, fuel assemblies, control rod mechanisms, pressurizer, primary coolant pumps, steam generators, and containment building — elements standard in many plants built by Westinghouse Electric Company and Babcock & Wilcox. Fuel assemblies often derive from fuel vendors such as Westinghouse Electric Company and Areva NP and use enriched uranium in zirconium alloy cladding developed with metallurgical research institutions like Oak Ridge National Laboratory and Argonne National Laboratory. The pressurizer, a signature element in designs standardized by vendors like Combustion Engineering, maintains the primary loop pressure and interfaces with instrumentation certified under standards from organizations such as American Society of Mechanical Engineers. Steam generators transfer heat to a secondary loop feeding turbines manufactured by firms like General Electric and Siemens, with balance‑of‑plant components sourced from industrial partners including Hitachi and Mitsubishi Heavy Industries.

Operation and Thermodynamics

Normal operation maintains the primary coolant at pressures around 15–16 MPa to suppress boiling while core power is controlled via control rods and chemical shim using boron solutions developed by national laboratories such as Lawrence Livermore National Laboratory. Thermal power generated in the core is carried to steam generators where secondary water flashes to steam to drive turbines in plants operated by utilities like EDF (Électricité de France) and Kansai Electric Power Company. Thermodynamic cycles employ Rankine principles familiar to engineers trained at institutions such as Massachusetts Institute of Technology and Imperial College London, with heat transfer and neutron flux management guided by research from Brookhaven National Laboratory and Paul Scherrer Institute. Load following, grid synchronization, and transient behavior are analyzed using codes developed at organizations like Electric Power Research Institute and Nuclear Energy Agency.

Safety Systems and Regulation

Safety architecture incorporates multiple, redundant, and diverse systems influenced by lessons from Three Mile Island accident and regulatory frameworks enforced by agencies including the Nuclear Regulatory Commission and national authorities such as Autorité de sûreté nucléaire. Emergency core cooling systems, containment spray, and residual heat removal subsystems are designs often certified to standards from American Nuclear Society and international guidelines from the International Atomic Energy Agency. Defense‑in‑depth strategies and probabilistic risk assessments have been advanced by institutions such as Sandia National Laboratories and implemented in fleet modifications by operators like Entergy Corporation and EDF (Électricité de France). Post‑accident mitigation measures and regulatory reforms after incidents at facilities like Fukushima Daiichi Nuclear Power Plant led to stress tests coordinated by the European Commission and updated licensing processes with increased instrumentation and human‑factors training promoted by Institute of Nuclear Power Operations.

Fuel Cycle and Waste Management

Fuel for these reactors follows a cycle involving uranium mining operations in regions such as Niger and Australia, enrichment services provided by entities like Urenco and Russia’s Rosatom, fuel fabrication by companies including Westinghouse Electric Company and AREVA, and spent fuel handling at interim storage facilities exemplified by sites like Yucca Mountain (proposal) and dry cask solutions used by utilities including Exelon Corporation. Reprocessing options championed historically by governments such as France and institutions like CEA (Commissariat à l'énergie atomique) contrast with once‑through policies practiced in nations such as the United States. Geological disposal strategies are investigated at programs like Onkalo in Finland and studied by organizations such as the Nuclear Waste Management Organization.

Advantages and Limitations

Advantages include proven commercial deployment by firms such as Westinghouse Electric Company and Mitsubishi Heavy Industries, operational familiarity among utilities like EDF (Électricité de France) and Tokyo Electric Power Company, and integrated safety features standardized through bodies like the Nuclear Regulatory Commission. Limitations involve susceptibility to loss‑of‑coolant scenarios addressed in part by designs influenced by the Three Mile Island accident investigations, economic competitiveness against renewables promoted by policies in jurisdictions such as Germany and Denmark, and challenges in waste disposition debated in forums including the Nuclear Energy Agency and national parliaments.

Notable Reactors and Incidents

Notable commercial PWR stations and projects include Shippingport Atomic Power Station, fleets operated by EDF (Électricité de France), early naval reactors such as USS Nautilus (SSN-571), and modern deployments by ROK (Republic of Korea) manufacturers like Korea Electric Power Corporation. Incidents and operational milestones that shaped the class include the Three Mile Island accident, responses to the Fukushima Daiichi Nuclear Power Plant crisis, and international safety reviews coordinated by the International Atomic Energy Agency and the Nuclear Regulatory Commission. Research reactors and test facilities at Oak Ridge National Laboratory and Argonne National Laboratory contributed to technical validation and licensing foundations used by commercial vendors and operators worldwide.

Category:Nuclear reactors