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Water-Cooled Reactors
Published in William J. Nuttall, Nuclear Renaissance, 2022
The technology of boiling light water reactors (BWRs) illustrates well the success of research, development, and demonstration in the nuclear power field. From the earliest days of LWR research, it had been clear that the separation of the reactor coolant circuit from the steam (and feedwater) circuit passing through the turbines is a source of inefficiency. In the case of a PWR, both circuits are light water and the highly complex steam generators are simply there to transfer heat from the hot reactor coolant to produce steam to drive turbines. The reason that LWR designers did not immediately consider driving the turbines with light water steam directly from a coolant circuit was the worry that the light water in the coolant circuit should remain liquid at all times (as forced by the application of high pressure from the pressure vessel). Early LWR designers felt that it was vital to avoid steam voids in the reactor core (which would arise if boiling were to occur) as these would cause instabilities in the reactivity and that the reactor might become uncontrollable [61].
Crystal Defects and Nuclear Technology
Published in C. J. Humphreys, Understanding Materials, 2020
The first concerns thermal reactor pressure vessels where both the operating temperature and neutron fluxes are comparatively low. Nevertheless, vessel integrity must be assured throughout the reactor lifetime, which for a modern PWR could be up to 60 years. The key issue is the probability of unstable fracture of the vessel. Since they are manufactured from ferritic steels which undergo a ductile-to-brittle transition it is necessary to know the extent of hardening and embrittlement due to neutron irradiation in terms of both the shift in the ductile to brittle transition temperature (DBTT) and reduction in upper shelf toughness.
The Pressurized Water Reactor
Published in Robert E. Masterson, Nuclear Reactor Thermal Hydraulics, 2019
Just like the dimensions of the pressure vessel, the dimensions of the core tend to become larger as the power output of the plant is increased. A modern PWR has an average volumetric power generation rate of about 105 kW/L. This is about twice the volumetric power density of a modern boiling water reactor (BWR) which we will discuss in Chapter 3. The primary reason why the power density is higher in a PWR is the design of the core and the U-235 concentration in the fuel. Table 2.3 summarizes the core design parameters for two-loop, three-loop, and four-loop Westinghouse PWRs. The fuel assemblies in most PWRs use Zircaloy-4 for the cladding, and about 97.5% of the heat is generated in the fuel. The rest is deposited in the coolant and in the surrounding structural material. In a PWR with four primary loops, the mass flow rate can approach 20,000 kg/s. The mass flow rate in two-loop plants is about half that amount. In a two-loop plant, the uranium in the fuel can weigh about 50,000 kg, and in a four-loop plant, it can weigh about 82,000 kg. (The oxygen atoms attached to the uranium molecules weigh about 13% more.) A single fuel assembly will contain about 420 kg of enriched uranium. Thus, a four-loop PWR can contain about 82 metric tons of enriched uranium.
Economically Feasible Mobile Nuclear Power Plant for Merchant Ships and Remote Clients
Published in Nuclear Technology, 2018
Luciano Ondir Freire, Delvonei Alves de Andrade
There are many candidate technologies of nuclear reactors nowadays. This work assumes a pressurized water reactor (PWR) because it is the most successful design up to now due to a good compromise between safety, compactness, weight, and simplicity. Most military ships use a PWR and all merchant ships and icebreakers ever built adopted PWR plants. Compactness and light weight are important to give room for useful payload. With the advent of passive safety devices, PWR plants achieve safety levels far greater than older designs, and the construction and reduction of active (energy-powered) devices has reduced maintenance costs. The very fact that naval reactors are always at sea gives a readily available heat sink.
Experimental and analytical investigations on aerosol washout in a large vessel with high spray coverage ratio simulating PWR containment spray
Published in Journal of Nuclear Science and Technology, 2022
Haomin Sun, Yohan Leblois, Thomas Gelain, Emmanuel Porcheron
In the event of a severe accident of a pressurized water reactor (PWR), radioactive materials may be released. A large fraction of them will be in particulate forms, and a part of these will be transported to and dispersed in the reactor containment as aerosols [1]. As a mitigation strategy for radioactive materials, the containment spray systems can be used to remove (washout) the aerosols in the containment atmosphere and retain the radioactive materials in a sump. Therefore, it is crucial to correctly predict the removal efficiency of aerosols in the containment by spray for nuclear safety assessment.
Nuclear Forensics Methodology for Reactor-Type Attribution of Chemically Separated Plutonium
Published in Nuclear Technology, 2018
Jeremy M. Osborn, Evans D. Kitcher, Jonathan D. Burns, Charles M. Folden, Sunil S. Chirayath
PWR fuel typically reaches a higher average burnup of 45 GWd/MTU. Unlike PHWRs, PWRs cannot be refueled during reactor operation. The theorized situation in which a PWR would result in weapons-grade plutonium production would be an unplanned reactor shutdown during which low-burnup fuel assemblies may be diverted. A detailed AP1000 model8 was used to represent a PWR for fuel burnup simulations.