Off Gas Flashcards
What is the purpose of the Offgas system?
Provide the means for removal and processing of non-condensing gases from the main condenser during startup and normal operation
What is the normal flowpath for Offgas?
Condenser, SJAE Suction Valves, SJAE, Preheater, catalytic recombiner, off gas condenser, water separator, 30 min holdup volume, cooler condenser, moisture separator, electric reheater, prefileter, charcoal adsorver, afterfilter, 310’ chimney
How many Offgas trains are there an how many are normally in service?
2 trains, 1 normally in serivce
What section of the condenser does Offgas take suction?
The cold end
What is the motive force for the SJAE Suction Valves? How do they fail?
Power supply?
Instrument Air - Fail as-is on loss of IA Instrument Bus (solenoid) fails closed
What happens to the SJAE Suction Valves on a circ water flow reversal?
They will auto reposition to take suction from cold end
What are teh limits for the SJAE Suction valves?
On low SJAE Steam Supply Pressure they will close:
1st and second stage <100psig
Booster Jet <90psig
What are teh SJAEs?
They are an Eductor and provide the motive force for teh Off-Gas System.
The driving force is 125# steam from throttle header
Which trains have a booster jet?
2A and 3B
What is the purpose of the Oxygen injection system and where does it inject?
Injects upstream of preheater to ensure it will heat up before recombiner
Used to recombine with H2 and reduce explosive mixture
Excess flow check valve limits flow to 300scfm
What is the purpose of the Preheater? Steam Supply
Superheats steam from SJAE to allow efficient recombination and remove water (drain to Main condenser)
Uses 250psig throttle Header Steam
What is the purpose of the Catalytic Recombiner?
Used to recombine H2 and O2 gases to water vapor and reduce H2 concentration to <1%
When must the Catalytic Recombiner be in operation?
Before Rx Pressure is >900psig
What is the normal termperature of teh Cat. Recombiner in Operation? Standby?
Operation: >900F
Standby: >250F
What is the Offgas Condenser?
Where does it drain?
Used to cool and condense superheated steam from recombiner using a U type Hx w/ condensate flow on tube side.
Drains to Main condenser
What are teh normal level control setpoints for teh offgas condenser and how is it maintained?
Normally kept at 30% using normal level control valve.
Emergnecy level control valve will keep below 50%
Locks up at 45psig IA
What is the purpose of the Water Separator? where does it drain to?
Removes moisture from off-gas condenser effluent using basket of metal shavings
Drains back to off-gas condenser via loop seal
What is the Hydrogen analyzer?
Used to measure the H2 concentration downstream of recombiner.
One analyzer REQUIRED to be on whenerver OG is running
What is the purpose of the 30 min hold-up volume?
Used to reduce downstream activity and provide time delay for decay of short lived Xe and Kr.
Actual holdup time is 6hr
What indications exist for Hold-up Volume?
Temp & Pressure indicate for fire
Rad Detectors: Flux Tilt and OG Rad Mon
What are teh alarms for the OG Rad Mon?
2 upscale OR 1 upscale and 1 downscale w/ 15 min time
What is the purpose of the Cooler Condenser?
Where does it drain?
To further cool the steam/gas mixture for moisture control prior to flow entering the charcoal adsorbers - cooled by glycol system
Drains to Pressurized Drain Tank via loop seal
What is the purpose of the OG Glycol System?
Provide cooling medium for the cooler condenser
What is the normal temperature setpoint for the glycol system? What is it’s power source?
What cools the glycol system?
Normally controls the glycol at 35F
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Glycol chillers cooled by Service Water
