What is the purpose of the Steam Dump System?
Assist rod control in returning Tavg to within the operating band following a load rejection.
Designed to pass 40% of the maximum calculated steam flow to the Condenser.
Combined with a 10% step load change capability of the Rod Control System, can accommodate a 50% step load rejection without a reactor trip, and without lifting the Main Steam Safety Valves.
Return Tavg to no-load value (557F) following a plant trip.
What is the purpose of the steam dump valves?
To assist smooth increase/decrease in steam flow and temperature, as the reactor plant approaches a final steady state condition
What order do the steam dump valves open in?
All valves in Bank 1 are fully open before the three valves in Bank 2 begin to leave their shut seats
What percentage of the total steam dump system capacity is each bank capable of handling?
33.3%
What happens in a rapid load reduction?
the setpoints of steam dump trip open bistables may be reached. These will direct banks of steam dump valves to go to the full open position with no modulation. Bank 1 valves trip open first, followed by Banks 2 & 3 tripping open simultaneously. This rapid opening allows the system to respond more quickly to a rapid decrease in load
DESCRIBE the function and location of the Steam dump valves (PV49A/B/C), (PV48A/B/C), (MSS-PV47A/B/C)
Each is an 8 inch pneumatic diaphragm, reverse acting, plug type valve
These valves are located on the 38’ level of the Turbine Building on the West side
DESCRIBE the function Steam dump valve I/P converters
Valve modulation
DESCRIBE the function and location of the Steam dump valve positioners
The valve positioner’s function is move the steam dump valve to the desired position
How does the RCS interact with the steam dump system (SDS)?
steam dump system acts as an artificial load on the main steam system
Why must caution be exercised when drawing steam?
to avoid a rate compensated Low Steam Line Pressure Safety Injection
What happens if the Steam Dump system fails to actuate on a load reject or plant trip?
RCS temperature and SG pressure will increase until the Atmospheric Dump valves actuate to limit any further increase.
Will a single failure to the steam dump control system cause all the steam dump valves to open?
no
If a steam dump fails to close after being opened will its max steam relieving capacity result in an excessive RCS cooldown?
no
Are there any tech specs associated with the steam dump system?
no
