Steam flow closure

It is also important to note that the lowest design pressure of any section of the casing must be specified to be no lower than the pressure which it may be subjected to under the PR valve relieving conditions. This is necessary to recognize pressure drop within the casing. The PR valve should be sized to pass the normal steam flow to the turbine, but credit may be taken for steam flow which is withdrawn from an intermediate turbine stage if it would not be blocked by the same contingency as closure of the exhaust. 

Two systems had been provided to cope with this mechanical failure. The first system signalled to the operators in the control room the open status of the valve and, therefore, the lack of its re-closure. It consisted of an instrument, readable in the control room, which measured the temperature in the pipe connecting the relief valve to the steam condensation tank. When the valve was open, hot steam flowed into the pipe and the temperature indicated by the instrument is high. When the valve was closed, the pipe does not contain hot steam and the indicated temperature was low. 

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). 

Steam condensate removal is most commonly achieved by traps—devices that, in efFea, are very simple level controllers. Many plants have experienced the need for high maintenance with these. Sometimes enough steam leaks through to impair the accuracy of steam-consumption estimates based on steam flow metering. In addition, as pointed out by Mathur, a rapid closure of the steam valve may cause a vacuum in the shell and pull back condensate through the trap with possible hammering and vibration in the shell. As a result, some reboilers, particularly large ones, are now equipped with condensate seal pots. These pots then have conventional level controllers. 

Decrease in the main steam flow rate by 5% resulting from closure of the turbine control valves. 

Mass balance measurements for 41 elements have been made around the Thomas A. Allen Steam Plant in Memphis, Tenn. For one of the three independent cyclone boilers at the plant, the concentration and flow rates of each element were determined for coal, slag tank effluent, fly ash in the precipitator inlet and outlet (collected isokinetically), and fly ash in the stack gases (collected isokinetically). Measurements by neutron activation analysis, spark source mass spectroscopy (with isotope dilution for some elements), and atomic adsorption spectroscopy yielded an approximate balance (closure to within 30% or less) for many elements. Exceptions were those elements such as mercury, which form volatile compounds. For most elements in the fly ash, the newly installed electrostatic precipitator was extremely efficient. 

The pyrolysis experiments were conducted in an electrically heated, once-through tubular flow reactor, designed to simulate the time-temperature history experienced in commercial steam-cracking operations. Reactor effluent compositions were ascertained by gas chromatograph and mass spectrometer analyses. Material and hydrogen balances could always be effected, with typical closures of 98 2 wt %. 

The steam generated in the core r on is separated from the reactor coolant in the steam separators on top of the moderator tank cover, and its content of water droplets and moisture is lowered on the passage through the steam driers. The "dried" steam collects in the top portion of the RPV, from where it is conveyed to the turbine plant through four steam lines. The steam lines connect to nozzles with built in "flow limiters", evenly distributed along the vessel circumference own medium operated isolation valves are provided on the inside and outside of the containment wall, the outer valve is equipped also with a motor operated actuator to ensure leaktightness after closure. 

Steam generator blowdown radiation monitors. The presence of radioactive material in the steam generator blowdown indicates a leak between the primary and secondary side of die steam generator. The monitor initiates an alarm in the main control room, initiates closure of the steam generator blowdown containment isolation and flow control valves and diverts flow to the liquid radwaste system. 

Flow Paths in the Steam Closure Cave and Effluent Control Module (specific to FLHT-5 but representative of all FLHT tests)... 

The event tree of the transients with PCS available at the initial stage is shown in Figs. 6.77 and 6.78. It is assumed that the steam cannot be discharged from the core to the condenser due to the closure of the MSIVs or the turbine trip without turbine bypass. Thus, the SRVs need to be opened in order to protect the pressure boundary and also keep the coolant flow in the core. Since the safety valve functicHi of the SRVs (see Sect 6.3) is passively actuated, their failure to open is not considered for... 

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