Partial-load heating loss

Exposed Hot Liquid Surfaces. Other partial-load heating losses may occur by radiation and convection from exposed liquid surfaces, as salt and lead baths (chap. 4), or from water baths (table 4.23 of reference 51). 

Heat losses affect the fuel processor efficiency, especially at partial system load. This becomes obvious when taking into consideration that the reactors of the fuel processor require an elevated operating temperature. This temperature will not decrease at partial load. Therefore heat losses remain constant and become dominant at partial load of the system. Smaller system size has similar effects. 

The covering of all major abnormal transients by these proposed models are confirmed by comparing the results obtained by them with results obtained from detailed fuel rod analyses modeling each abnormal transient event. The following eight abnormal transient events are analyzed for confirmation inadvertent startup of the auxiliary feedwater system (AFS) loss of feedwater heating loss of load without turbine bypass withdrawal of control rods at normal operation main coolant flow control system failure pressure control system failure partial loss of reactor coolant flow and loss of offsite power. 

One is the secondary- coolant reduction test by partial secondary loss of coolant flow in order to simulate the load change of the nuclear heat utilization system. This test will demonstrate that the both of negative reactivity feedback effect and the reactor power control system brings the reactor power safely to a stable level without a reactor scram, and that the temperature transient of the reactor core is slow in a decrease of the secondary coolant flow rate. The test will be perfonned at a rated operation and parallel-loaded operation mode. The maximum reactor power during the test will limit within 30 MW (100%). In this test, the rotation rate of the secondary helium circulator will be changed to simulate a temperature transient of the heat utilisation system in addition to cutting off the reactor-inlet temperature control system. This test will be performed under anticipated transients without reactor scram (ATWS). 

High-surface-area titania aerogels can stabilize dispersed vanadia species at higher vanadia loadings than conventional titania supports. Their full potential however, cannot be materialized because at vanadia loadings above 10 weight % a partial collapse of the gel structure and a subsequent loss of surface area take place upon heat treatment. 

The first category (flibe return temperature increase) results from partial loss of heat sink two plausible partial loss of heat sink cases have been examined - loss of chemical plant heat sink (LOCP) and loss of Brayton cycle heat sink (LOBC). The resulting clad and fuel temperatures are shown in Figure XXIV-10c. When the flibe return temperature increases due to partial loss of load, the reactor power self adjusts downward to match the decreased load under action of the coolant average reactivity coefficient. Clad and fuel temperatures decrease and the reactor passively adjusts to a safe operating state. 

The mechanical loads on the reactor vessel support structure include the dead weight and seismic loads. The thermal loads include the differential thermal expansion loads for the normal reactor operation as well as the temperature response of the support structure for a number of postulated thermal transients. These include the reactor closure head heating system overpower, full and partial loss of closure head heaters and reactor vessel heat-up and cool-down events. 

Abnormal transients Decrease in core coolant flow rate Partial loss of reactor coolant flow Loss of offsite power Abnormality in reactor pressure Loss of turbine load Isolation of main steam line Pressure control system failure Abnormality in reactivity Loss of feedwater heating Inadvertent startup of AFS Reactor coolant flow control system failure Uncontrolled CR withdrawal at normal operation Uncontrolled CR withdrawal at startup Accidents... 

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