Cooling system, light water reactor

Or to use a design in which the core of a conventional pressurised water reactor (PWR) is enclosed within a vessel of boronated water that will flood the core if pressure is lost there is no barrier between the core and the pool of water, which in case pressure in the primary system is lost will shut the reactor down and continue to remove heat from the core by natural circulation. It is calculated that in an accident situation, replenishing of cooling fluid can be done at weekly intervals (in contrast to hours or less required for current light water reactor designs) (Harmerz, 1983 Klueh, 1986). 

Most commercial nuclear power plants in the United States are light water reactors, moderated and cooled by ordinary water. Figure 26-12 is a schematic diagram of a light water reactor plant. The reactor core at the left replaces the furnace in which coal, oil, or natural gas is burned in a fossil fuel plant. Such a fission reactor consists of five main components (1) fuel, (2) moderator, (3) control rods, (4) cooling system, and (5) shielding. 

Summary of Rule Changes, Section 50.46, Acceptance Criteria for Emergency Core Cooling Systems for Light Water Reactors,... 

The Chapter is organized as follows. First, some fuel cycle characteristics used in comparative analysis of energy systems with different reactors are introduced. Second, open fuel cycle features and support strategies are surveyed for the nearer-term concepts. Then, the several proposed fuel cycle features and support options for the closed cycle concepts are surveyed. After that, fuel and ore resource utilization efficiencies for small reactors with long refuelling interval are discussed and are compared to those of standard light water reactors (LWRs) and typically projected liquid metal cooled fast breeder reactors (LMFBRs). Implications on fuel cycle costs are discussed, and the notion of fuel leasing is presented. 

Blackout This is an event with a major contribution to core meltdown probability in a conventional light water reactor. In CAREM, extinction and cooling of the core and decay heat removal are guaranteed without electricity, by the passive safety systems. Loss of electrical power causes the interruption of feedwater supply to the hydraulically driven CRDs and results in the insertion of absorbing elements into the core. Nevertheless, in the case of failure of the first and second shutdown systems (both passive) in CAREM, feedback coefficients cause self-shutdown of the fission reaction without compromising safety related variables. The decay heat is removed by the RHRS with autonomy of several days. 

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