Reactor coolant systems, nuclear power

NR letter l 05-01228, Space Nuclear Power - Reactor Coolant and Power Conversion System Concept - Approval of, dated April 20,2005... 

A nuclear power plant is a system in which some of the energy released by nuclear fission is used to generate electricity. Every such plant contains four fundamental elements reactor, coolant system, electrical-power generating unit, and safety system. 

AR58 Design of the reactor coolant system and associated systems in nuclear power plants. Safety guide,... 

The International Atomic Energy Agency set up a program to give guidance to its member states on the many aspects of the safety of nuclear power reactors (NPP). The bubbler tower (BT) is the most importance structure in the case of the accident of the pipe coolant system in the Reactor hall (Fig.l). The extreme pressure and the steam radioactivity are eliminated in the space of BT. 

INTERNATIONAL ATOMIC ENERGY AGENCY, Design of the Reactor Coolant System and Associated Systems in Nuclear Power Plants, Safety Standards Series, IAEA, Vienna (in preparation). 

The accidental depressurisation transient is analysed by using LOFTRAN. For reactor coolant system depressurisation analyses that include a primary coolant flow coast down caused by a consequential loss of offsite power, a combination of three computer codes is used to perform the DNBR analyses. First LOFTRAN is used to perform the plant system transient. FACTRAN is then used to calculate the core heat flux based on nuclear power and reactor coolant flow from LOFTRAN. Finally, VIPRE-01 is used to calculate the DNBR using heat flux from FACTRAN and flow from LOFTRAN. 

Design of the Reactor Coolant System and Associated Systems in Nuclear Power Plants... 

DESIGN OF THE REACTOR COOLANT SYSTEM AND ASSOCIATED SYSTEMS IN NUCLEAR POWER PLANTS... 

Fig. 1. Pressurized water reactor (PWR) coolant system having U-tube steam generators typical of the 3—4 loops in nuclear power plants. PWR plants having once-through steam generators contain two reactor coolant pump-steam generator loops. CVCS = chemical and volume-control system.

Boric acid [B(OH)3] is employed in primary coolant systems as a soluble, core reactivity controlling agent (moderator). It has a high capture cross-section for neutrons and is typically present to the extent of perhaps 300 to 1,000 ppm (down from perhaps 500 to 2,500 ppm 25 years ago), depending on nuclear reactor plant design and the equilibrium concentration reached with lithium hydroxide. However, boric acid may be present to a maximum extent of 1,200 ppm product in hot power nuclear operations. 

Nuclear and magneto-hydrodynamic electric power generation systems have been produced on a scale which could lead to industrial production, but to-date technical problems, mainly connected with corrosion of the containing materials, has hampered full-scale development. In the case of nuclear power, the proposed fast reactor, which uses fast neutron fission in a small nuclear fuel element, by comparison with fuel rods in thermal neutron reactors, requires a more rapid heat removal than is possible by water cooling, and a liquid sodium-potassium alloy has been used in the development of a near-industrial generator. The fuel container is a vanadium sheath with a niobium outer cladding, since this has a low fast neutron capture cross-section and a low rate of corrosion by the liquid metal coolant. The liquid metal coolant is transported from the fuel to the turbine generating the electric power in stainless steel... 

Because early Canadian reactors used heavy water, and because it is also fundamentally the most efficient moderator, Canada naturally adopted the heavy water reactor for the development of a nuclear power system. By using heavy water both as moderator and as coolant, and by refuelling with the reactor at power, it was possible to develop the CANDU system to operate efficiently and economically with natural uranium fuel. This in turn resulted in the simplest possible fuel cycle. 

For the monitoring of the released liquid effluents the following methods are used. Samples of effluents are collected by simple dipping devices and analyzed before release. In the case of monitoring streams in the neighbourhood of installations, automatic samplers collecting samples over a 24-hour period are used. Samples are analyzed and records must be kept of results. The water effluent meter monitors water or coolants and may be connected to a rate meter, recorder or alarm system. On site and off-site environmental monitoring at and near nuclear power plants, nuclear reactors and other fuel cycle activities are shown in Tables 7.5 and 7.6. 

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