Turbine trip

Turbine trip 1 Turbine trip with turbine bypass valve failure... 

Loet of primary coolant flow LOB8 of feed water ricw Loae of steam Flow Turbine trip... 

It is important to note safety differences between the SRS reactors and LWRs. Since the SRS reactors are not for power production they operate at a maximum temperature of 90° C and about 200 psi pressure. Thus, there are no concerns with steam blowdown, turbine trip, or other scenarios related to the high temperature and pressure aspects of an LWR. On the of nd, uranium-aluminum alloy fuel clad with aluminum for the SRS reactors melts at a m ver... 

Problems witbin tbe polisher unit caused operators to respond by attempting to unblock a cboked condition using instrument air. The air was at a lower pressure than the condensate and this caused water to enter the air system. This was not a standard procedure and the commercially supplied polisher unit was not built to standards consistent with the plant. Water in the instrument air system caused several instruments to fail and ultimately initiated a turbine trip. This interrupted heat removal from the radioactive core. The heat generation within the reactor was halted automatically within a few minutes by dropping metal rods to absorb neutrons within the core. 

Although extruded ceramic honeycombs were extensively investigated in the earlier stages of development [6, 9], their use has been progressively abandoned, mainly due to inadequate resistance against thermal shocks. Most ceramics will fracture during the sudden temperature drop associated with fuel cut-off during turbine trips. 

Clearing any system with instrument air as a pressure source is a bad idea. Other pneumatic sources, such as utility air, plant air, or nitrogen, should be used instead. However, the Three Mile Island instrument air was at a lower pressure than the water stream on the resin polisher system. Despite the presence of check valves, there was a reverse flow water entered the instrument air system causing several instruments to fail, and the turbine tripped. Through a series of other errors, the water covering of the radioactive core was uncovered, allowing an escape of a small amount of radioactivity. Due to the widespread negative public reaction, the U.S. nuclear industry received a setback. If it were not for that improper hose connection or the erroneous one-minute modification,... 

The principal disadvantage of ceramic monoliths in gas turbine applications is their relatively low resistance to thermal shock. Most ceramics will fracture during the very rapid temperature drop that occurs after a turbine trip, when the turbine load is suddenly lost (see Section 3.2.2). 

U-15b Turbine trip with reactor trip (loss of main condenser or similar problem) 10... 

The water leak rate increases as the tubes break, but is limited by the feedwater pump capacity. After the water leak rate reaches the peak value, the main steam pressure decreases because the turbine trips due to the reduction of the main steam flow rate, and the feed water pump trips due to the reduction of its rotational firequency. Due to these quasipassive features, the water leak rate decreases and adverse consequences can be avoided by providing two pressure relief pipings with rupture disks at Ae bottom of the steam generator which operate at a pressure of 11 kg/cm. ... 

High level in steam generator, feedwater pumps stop, feedwater system valves shut-off, turbine trip 2... 

Loss of External Load Turbine Trip Loss of Condenser Vacuum Closure of Main Steam... 

PM EQA Continuing grid instability resulted in an automatic turbine trip. 

PM EQA The Reactor Protection System (RPS) initiated a reactor scram as aresult of the turbine trip. All MSIVs closed due to the loss of RPS power). 

Chapter 15 lists the assumptions used in the turbine trip e analysis. These assumptions are chosen so that they tend to maximize the required pressure relieving capacity of the primary and secondary valves. The analysis demonstrates that sufficient relieving capacity has been provided so that when acting in conjunction with the reactor protective system the safety valves will prevent the pressure from exceeding 110% of the design pressure. 

D. No credit is taken for letdown, charging, pressurizer spray, turbine bypass, or feedwater addition after the turbine trip in the loss-of-load analysis. Letdown and pressurizer spray both act to reduce primary pressure. By not taking credit for these systems the rate of pressurization is increased. By not taking credit for the addition of feedwater the steam generator secondary inventory will be depleted at a faster rate. This in turn reduces the capacity of the steam generator to remove heat from the primary loop and maximizes the rate of primary pressurization. 

Increase in reactor heat removal inadvertent opening of steam relief valves secondary pressure control malfunctions leading to an increase in steam flow rate feedwater system malfunctions leading to an increase in the heat removal rate. —Decrease in reactor heat removal feedwater pump trips reduction in the steam flow rate for various reasons (control malfunctions, main steam valve closure, turbine trip, loss of external load, loss of power, loss of condenser vacuum). 

The exhaust from the low pressure turbine cylinders flows to the main turbine condenser which has three shells, located under the exhaust hoods of the low pressure turbine cylinders. The condenser is designed to accept also the steam flow from the main steam bypass system on startup, hot standby and turbine trip. During normal power operation, the steam flow to the condenser amounts to about 60% of the total steam flow, but the condenser system is designed to accommodate the full steam flow for a limited time period the steam flow shall be reduced to 60% within 20 seconds to avoid a reactor trip due to too high condenser pressure. 

The condenser is cooled by the circulating water system which typically incorporates three electrically driven pumps loss of one pump will call for a power reduction, but will not yield a turbine trip in the short term. The condensate is pumped forward to the dearator (or the feedwater tank) through low pressure heaters and a condensate cleanup system with ion exchange filters by means of three 50% condensate pumps. The drmnage from the heaters is pumped forward through the cleanup system by means of a dedicated low pressure drain pump. 

Reactor pressure increase Several events may cause this e.g., inadvertent closure of one turbine control valve, pressure regulator downscale failure, generator load rejection, turbine trip MSIV closure, loss of condenser vacuum, loss of nonemergency AC power to station auxiliaries, loss of feedwater etc. All these have been analysed. Features are included in the instrumentation and control systems or redundancies to maintain reactor pressure through a combination of component automatic responses or operator actions, depending on the identified cause. 

The turbine exhaust flows to a condenser which has three shells, located under the low pressure turbine exhaust hoods. The condenser also accepts the exhaust flow from the feed pump turbines and, on startup, hot standby and turbine trip, flow from the main steam and bypass system. 

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