Nuclear reactors coolant loss

Transient two-phase flow in rod bundles. In analyzing transient two-phase flows in rod bundles, such as the case resulting from a postulated loss-of-coolant or flow accident in a nuclear reactor, Ishii and Chawla (1978) developed a multi-... 

Rewetting of hot surface. In this case, the liquid phase contacts a hot surface and rewets it, with the accompanying formation of vapor. Examples here are the quenching of hot metal objects in metal forming processes and the rewetting of hot fuel elements in a nuclear reactor following a loss-of-coolant accident. 

The CVI SiC/SiC composites are also promising for nuclear applications because of the radiation resistance of the p phase of SiC, their excellent high-temperature fracture, creep, corrosion and thermal shock resistances. Studies on the P phase properties suggest that CVI SiC/SiC composites have the potential for excellent radiation stability [5]. Furthermore, because of excellent thermal fatigue resistance, start-up and shut-down cycles and coolant loss scenarii should not induce significant stmctural damage [5]. The CVI SiC/SiC are also considered for applications as stmctural materials in fusion power reactors, because of their low neutron-induced activation characteristics coupled with excellent mechanical properties at high temperature [6-8]. 

The principle of modular design of nuclear steam-supply systems (NSSSs) is most economically effective for the reactors in which inherent safety features against severe accidents have been realized to the maximum possible extent. Primarily, this should be attributed to accidents with coolant loss, such as LOCA. To cope with these accidents in light water reactors, many safety systems are needed that are not necessary for the SVBR-75/100. This considerably simplifies the technology of construction and assembly and reduces the scope of construction for the reactor compartment. 

Several events at nuclear facilities in the United States have resulted in dual-unit transients. The causes were due primarily to electrical disturbances (usually lightning strikes) which resulted in the loss of power to reactor coolant pumps or rod control systems. In one case a plant runback occurred when air compressors were lost due to the loss of electrical control equipment in the control air system. 

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. 

Event trees are based on distinction between success and failure. The root of the tree is an initiating event and the subsequent layers down to the leaves correspond to the functions or subsystems which are activated in the case of success or Mlure of the subsystem (function) that corresponds to the higher Ir rer. An example event tree is shown in Fig.2 ([2]). In the example, the initiating event is a loss-of-coolant accident (L(XA) type event for an imaginary nuclear reactor em. In particular, the initiating event A is a pipe break in the primary system. 

Pressure Behavior in a Nuclear Reactor Containment following a Loss of Coolant Accident", by M.S. Khattab, N.A. Ibrahim and S.D. Bedrose, AEA Cairo... 

Babcock Wilcox claimed that, had there been auxiliary feedwater, the temperature of the reactor coolant might have remained relatively stable until the problem of the condensate pumps was corrected and normal feedwater was reinstated. This view has been contested not only by the NRC but also by the utility-sponsored Nuclear Safety Analysis Center, an investigative arm of the Electric Power Research Institute. Their investigations indicate that, except for adding another dimension to the areas of concern within the main control room, the early unavailability of auxiliary feedwater did not significantly affect the progression of the accident, which was dominated by the uncompensated loss of reactor coolant. 

An "anticipated transient" is an event that is expected to occur one or more times during the life of a nuclear power plant. There are a number of anticipated transients, some quite trivial and others that are more significant in terms of the demands imposed on plant equipment. Anticipated transients include such events as a loss of electrical load that leads to closing of the turbine stop valves, a load increase such as opening of a condenser bypass valve, a loss of feedwater flow, and a loss of reactor coolant flow. 

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