Nuclear reactors coolant types

Much of the recent research on stress-corrosion cracking of austenitic stainless steels has been stimulated by their use in nuclear reactor coolant circuits. The occurrence of stress-corrosion cracking in boiling water reactors (BWR) has been documented by Fox . A major cause for concern was the pipe cracking that occurred in the sensitised HAZ of the Type 304 pipework, which is reported to have been responsible for about 3% of all outages of more than 100 h from the period January 1971 to June 1977. 

The assessment method that is reviewed in this publication is directly applicable to existing light water and heavy water reactors, and to spent fuel transported or stored in the pools outside the nuclear reactor coolant system on the site of these reactors. With some minor modifications, the method can also be used for other types of reactor such as reactors cooled with gas or with liquid... 

A variety of nuclear reactor designs is possible using different combinations of components and process features for different purposes (see Nuclear REACTORS, reactor types). Two versions of the lightwater reactors were favored the pressurized water reactor (PWR) and the boiling water reactor (BWR). Each requites enrichment of uranium in U. To assure safety, careful control of coolant conditions is requited (see Nuclearreactors, water CHEMISTRY OF LIGHTWATER REACTORS NuCLEAR REACTORS, SAFETY IN NUCLEAR FACILITIES). 

Figure 31.2 Various types of nuclear reactor currently in use or being developed (F fuel E enrichment, expressed as present M moderator C coolant).

FIGURE 17.25 A schematic representation of one type of nuclear reactor in which water acts as a moderator for the nuclear reaction. In this pressurized water reactor (PWR), the coolant is water under pressure. The fission reactions produce heat, which hoi Is water in the steam generator the resulting steam turns the turbines that generate electricity. 

The basic design of most nuclear reactors is similar, but several types of reactors are used throughout the world. In the United States most reactors use plain water as the coolant. Reactors using ordinary water are called light water reactors. Light water reactors can be pressurized to approximately 150 atmospheres to keep the primary coolant in the liquid phase at temperatures of approximately 300°C. The heat from the pressurized water is used to heat secondary water to generate steam. In a boiling water reactor, water in the core is allowed to boil. The steam produced powers the turbines directly. Heavy water reactors use water in... 

Coolant -for molten steel [IRON BY DIRECT REDUCTION] (Vol 14) -for nuclear reactors [NUCLEARREACTORS - REACTOR TYPES] (Vol 17)... 

Boiling Water Reactor A type of nuclear power reactor that uses ordinary water for both the coolant and the neutron moderator. The steam is used to directly produce electricity through generators. 

A one degree rise in melting point to 97.6+l=98.6°C is accompanied by an increase of pressure of 134 atm, and so use of the liquid sodium at the suggested 100 atm and 100°C would give no problems. Liquid sodium is in fact used as a coolant in some types of nuclear reactor. 

In addition to classifying nuclear reactors as thermal or fast, they may be characterized by their purpose, by the type of moderator used to slow down neutrons, by the type of coolant, or by the type of fuel. The principal purposes for which reactors may be used are for research, testing, production of materials such as radioisotopes or plutonium, or power generation. This text is concerned mainly with power reactors. 

FIG. 2. "Arctica "-type icebreaker s nuclear power plant configuration 1-reactor, 2-steam generator, 3-reactor coolant pump, 4-auxiliary turbine generator (ATG),... 

Leardini, L, Cadeddu, M. and Schiavoni, M. (1961) Tests on a cavern for the determination of temperature and pressure transients in a case simulating a major Loss of Coolant-type reactor accident , Energia Nucleare, February. 

Computer code CALPER — a thermal hydraulic subchannel analysis code for the assessment of coolant local conditions in the fuel assemblies and in the core of PWRAVWER-type nuclear reactors... 

There are several different kinds of nuclear reactors that use diverse types of fuel (uranium compounds) that are placed in different sorts of fuel elements and these in turn are arranged in varions fuel assemblies. A detailed survey of these is beyond the scope of this book however an elementary understanding of nuclear fuel and its characterization is highly relevant. Figure 1.14 depicts the main nuclear reactor, types of fuel, moderator, and coolants in service. 

Pashevich, V. I. USSR experience in decontamination and water chemistry of VVER type nuclear reactors. Report IAEA TECDOC-667 Coolant Technology of Water Cooled Reactors. Vol. 3, Activity Transport Mechanisms in Water Cooled Reactors. Vienna 1992, p. 155-174... 

Deposition of corrosion products in a circulating AT liquid metal system is important for three reasons. First, the degradation of heat transfer perfonmance of heat exchangers must be predicted. Second, radiation exposure limits for maintenance in certain areas of nuclear reactor systems that transport and deposit radioactive species must be controlled. Third, the tendency for all deposits to become detached by thermal shock or flow perturbations must be known since there is concern that these types of debris could block critical coolant channels. It is therefore valuable, when possible, to monitor reactions involving deposition as well as dissolution. 

The Fixed Bed Nuclear Reactor (FBNR) concept assumes the use pressurized water reactor (PWR) technology, but incorporates hi temperature gas cooled reactor (HTGR) type fuel and the concept of a suspended fixed bed core. Spherical fuel elements are fixed in the suspended core by the flow of water coolant. Any accident signal will cut off the power to the coolant pump causing a stop in the flow. This would make the fuel elements fall out of the reactor core, driven by gravity, and enter a passively cooled fuel chamber where they would reside in a subcritical condition. The Fixed Bed Nuclear Reactor (FBNR) is a simplified version of the fluidized bed nuclear reactor concept [XII-1 to XII-9]. In the FBNR, spherical fuel elements are in a fixed position in the core therefore, there is no concern about the consequences of multiple collisions between them, an issue that may be raised about the fluidized bed concept. Relatively little work has been done for the fixed bed nuclear reactor so far, but the experiences gained from the development of a fluidized bed reactor can facilitate the development of the FBNR. 

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