Off Gas

Question 1

What is the purpose of the Offgas system?

Answer 1

Provide the means for removal and processing of non-condensing gases from the main condenser during startup and normal operation

Question 2

What is the normal flowpath for Offgas?

Answer 2

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

Question 3

How many Offgas trains are there an how many are normally in service?

Answer 3

2 trains, 1 normally in serivce

Question 4

What section of the condenser does Offgas take suction?

Answer 4

The cold end

Question 5

What is the motive force for the SJAE Suction Valves? How do they fail?
Power supply?

Answer 5

Instrument Air - Fail as-is on loss of IA
Instrument Bus (solenoid) fails closed

Question 6

What happens to the SJAE Suction Valves on a circ water flow reversal?

Answer 6

They will auto reposition to take suction from cold end

Question 7

What are teh limits for the SJAE Suction valves?

Answer 7

On low SJAE Steam Supply Pressure they will close:
1st and second stage <100psig
Booster Jet <90psig

Question 8

What are teh SJAEs?

Answer 8

They are an Eductor and provide the motive force for teh Off-Gas System.
The driving force is 125# steam from throttle header

Question 9

Which trains have a booster jet?

Answer 9

2A and 3B

Question 10

What is the purpose of the Oxygen injection system and where does it inject?

Answer 10

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

Question 11

What is the purpose of the Preheater? Steam Supply

Answer 11

Superheats steam from SJAE to allow efficient recombination and remove water (drain to Main condenser)
Uses 250psig throttle Header Steam

Question 12

What is the purpose of the Catalytic Recombiner?

Answer 12

Used to recombine H2 and O2 gases to water vapor and reduce H2 concentration to <1%

Question 13

When must the Catalytic Recombiner be in operation?

Answer 13

Before Rx Pressure is >900psig

Question 14

What is the normal termperature of teh Cat. Recombiner in Operation? Standby?

Answer 14

Operation: >900F
Standby: >250F

Question 15

What is the Offgas Condenser?

Where does it drain?

Answer 15

Used to cool and condense superheated steam from recombiner using a U type Hx w/ condensate flow on tube side.
Drains to Main condenser

Question 16

What are teh normal level control setpoints for teh offgas condenser and how is it maintained?

Answer 16

Normally kept at 30% using normal level control valve.
Emergnecy level control valve will keep below 50%
Locks up at 45psig IA

Question 17

What is the purpose of the Water Separator? where does it drain to?

Answer 17

Removes moisture from off-gas condenser effluent using basket of metal shavings
Drains back to off-gas condenser via loop seal

Question 18

What is the Hydrogen analyzer?

Answer 18

Used to measure the H2 concentration downstream of recombiner.
One analyzer REQUIRED to be on whenerver OG is running

Question 19

What is the purpose of the 30 min hold-up volume?

Answer 19

Used to reduce downstream activity and provide time delay for decay of short lived Xe and Kr.
Actual holdup time is 6hr

Question 20

What indications exist for Hold-up Volume?

Answer 20

Temp & Pressure indicate for fire

Rad Detectors: Flux Tilt and OG Rad Mon

Question 21

What are teh alarms for the OG Rad Mon?

Answer 21

2 upscale OR 1 upscale and 1 downscale w/ 15 min time

Question 22

What is the purpose of the Cooler Condenser?

Where does it drain?

Answer 22

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

Question 23

What is the purpose of the OG Glycol System?

Answer 23

Provide cooling medium for the cooler condenser

Question 24

What is the normal temperature setpoint for the glycol system? What is it’s power source?
What cools the glycol system?

Answer 24

Normally controls the glycol at 35F
Powered by 20-1/30-1
Glycol chillers cooled by Service Water

Question 25

What is the purpose of the OGFB Moisture Separator? Where does it drain to?

Answer 25

To remove moisture from cooled gas on discharge of cooler condenser.
drains to pressurized drain tank

Question 26

What is the purpose of the Pressurized Drain Tank?

Answer 26

Collects moisture drains from cooler condenser and moisture separator. Drain pumps pump condents to Radwaste

Question 27

What impact does OG Hi Rad Levels have?

Answer 27

After 15 minute time delay
Pressurized drain tank pump suction vales close if chimney isolation valve closes
Suction valve closure will trip the drain pumps to prevent pumping hi rad materials to radwast

Question 28

What is the function of the OGFB Reheater? P/S?

Answer 28

Heats gas to 77F for charcoal Adsorber. De-energizes at 200F

Powered from 20-1(30-1)

Question 29

What is the purpose of the Charcoal Adsorbers?

When MUST they be in service?

Answer 29

Delay noble gases by adsorption allowing greater decay time for long lived nuclides
Must be in service when Rx Power >30% per ODCM

Question 30

What is the purpose of the OGFB After Filter?

Answer 30

To filter out radioactive fines and daughter products which escape the charcoal

Question 31

What is purpose of Chimney Isolation Vlaves?

Answer 31

AOV isolates Offgas to Chimney

Auto closes on holdup volume Hi-Hi Rad after 15 minute delay time (2 up or 1up/1down

Question 32

How does Chimney Isolation Valve fail on loss of power or Air? what supplies power and air?

Answer 32

Fails AS IS on either loss of air or power.
Air from Instrument Air.
Power from ESS

Question 33

What is the purpose of the Chimney?

Answer 33

Receives input from DW Purge Fan, OG, RW Vent, TB Vent, OG Ven, SBGT, Gland Seal, Mech Vac. Pump, and HRSS and provides maximum dispersion of fission gasses

Question 34

How is decay time provided for gaseous systems that do not go to OGFB?

Answer 34

Gland Exhauster and Mech Vacuum Pump Discharge go to Holdup Volume in base of chimney - 5 cell

Question 35

What is the OG Rad Timer? Power Supply? Signal?

Answer 35

This is the 15 minute timer for Hi-Hi Rads in the OG Rad Monitor.
Powered by 24/48VDC. Monitors powered by RPS A&B

On signal of 2 upscale OR 1 upscale and 1 downscale, timer initiates
After timeout:
Alarm;
Chimney Isolation Valve CLOSES
When this closes, Pressurized Drain Tank valves to RW close;
When Drain Tank valves close, PDT Pump Trips
Closes 30 min holdup drains to RW

Question 36

What is the function of the Mechanical Vacuum Pump? Power source?
Interlock?

Answer 36

Designed to remvoe air from main condenser and establish vacuum for condenser operation at 20-25inHg
Powered by 26/36
Cannot Be run when Mode Switch in in RUN

Question 37

What will trip the Mechanical Vacuum Pump?

Answer 37

MSL Hi-Hi Rad
Hi Disch Temp ~200F
Low Oil Pressure
Discharge Valve not fully open
Suction Valve not full open