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Catawba Nuclear Station > GAS > Flashcards

GAS Flashcards

1
Q

What is the purpose of the Hydrogen Bulk Storage System?

A

The Bulk Hydrogen Storage System supplies high purity hydrogen gas for cooling the turbine generator, for overpressure on the Volume Control Tanks(VCT), and Catalytic Hydrogen Recombiners(CHRs) purging operations in the Waste Gas System.

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2
Q

What is the purpose of the Hydrogen Blanket System?

A

The Hydrogen Blanket System supplies low pressure hydrogen or nitrogen to the Reactor Coolant Drain Tanks(NCDTs). Nitrogen is currently used to supply both NCDTs because it is more convenient.

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3
Q

What is the purpose of the Bulk Oxygen System?

A

The Bulk Oxygen System supplies high purity oxygen gas for the Catalytic Hydrogen Recombiners(CHRs) in the Waste Gas System. Oxygen is used in the CHRs to control hydrogen concentration in the Waste Gas Decay Tanks(WGDTs). In the CHRs the oxygen is combined with hydrogen to produce water.

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4
Q

What is the purpose of the Nitrogen System?

A

The Nitrogen System stores and supplies gaseous nitrogen to various plant components at the required pressure and flow rate.

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5
Q

How are valves positioned in high pressure gas systems?

A

Valves in the high pressure gas systems are back-seated to prevent the gas from leaking out of the system along valve stem.

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6
Q

What is the system designator for the Hydrogen Bulk Storage System?

A

GS

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7
Q

What is the system designator for the Hydrogen Blanket System?

A

GB

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8
Q

What is the system designator for the Bulk Oxygen System?

A

GO

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9
Q

What is the system designator for the Nitrogen System?

A

GN

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10
Q

How many cylinders are utilized in the Hydrogen Bulk Storage?

A

6 cylinders, located in the Hydrogen House outside the Unit 1 Turbine Building

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11
Q

What is the normal pressure of the Hydrogen Bulk Storage cylinders, and how are they refilled?

A

The cylinders are refilled from from a truck to a pressure of 2100psig

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12
Q

When is the WCC SRO notified based on Hydrogen Bulk Storage System cylinder pressure?

A

The WCC SRO is notified to order hydrogen whenever 4 of the 6 cylinders are less than or equal to 400psig

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13
Q

What is the setpoint of the of the cylinder relief valve and rupture disc for the Hydrogen Bulk Storage System?

A

2450 psig(2 relief valves)

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14
Q

What is the setpoint for the relief valves in the Hydrogen Bulk Storage System?

A

The system has two downstream reliefs set at 150psig

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15
Q

What types of monitors are used while refilling the Bulk Hydrogen Storage Cylinders?

A

Oxygen/Explosive Limit Gas Air Monitors

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16
Q

How are Hydrogen Bulk Storage System cylinders placed in service, and what is the precaution?

A
  1. The cylinders are placed in service alphabetically, in groups of twos when possible to create even cyclic wear on components
  2. Cylinder isolation valves are opened slowly to prevent rapid pressure equalization
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17
Q

How large is the exclusion area that’s established around the Hydrogen House when receiving a hydrogen delivery?

A

50 feet, no uninvolved personnel or ignition sources are allowed in the area

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18
Q

When would the Control Room be notified of a hydrogen leak while receiving a hydrogen delivery?

A

If leaks are found that cause the air monitor to indicate greater than 10% LEL/EXP

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19
Q

How are hydrogen cylinders placed in service when a pair are low?

A

The cylinders being removed from service are isolated first, then the new cylinders are placed in service.

Cylinders are removed from service when their pressure is 400psig

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20
Q

What is the major hazard associated with the Hydrogen Bulk Storage System?

A

Explosion/Fire Hazard

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21
Q

What are the PPE requirements for unloading hydrogen?

A

All personnel within 15 feet of the Hydrogen House are required to wear:

  1. Hard hat
  2. Safety glasses
  3. Leather gloves
  4. Face shield
22
Q

How many cylinders are utilized in the Hydrogen Blanket System?

A

There are two cylinders(nitrogen or hydrogen) for each unit’s Reactor Coolant Drain Tank(NCDT)

23
Q

What is the normal system alignment for the Hydrogen Blanket System?

A

One cylinder is placed in service while the other is maintained as a backup. The cylinders are manually realigned when pressure is low in the inservice cylinder.

24
Q

What pressure is maintained by the Hydrogen Blanket System?

A

A pressure regulating valve controls the supply pressure to the Reactor Coolant Drain Tank and is set to maintain downstream pressure of 2psig

25
Q

When will the Control Room receive an alarm based on cylinder pressure in the Hydrogen Blanket System?

A

1psig and decreasing in the inservice cylinder

26
Q

How many cylinders are used in the Bulk Oxygen System?

A

2 cylinders, each with a pressure regulator

27
Q

How do the pressure regulators in the Bulk Oxygen System operate to maintain system pressure?

A
  1. The “A” cylinder pressure regulator will open when manifold pressure is less than 60psig
  2. The “B” cylinder pressure regulator will open when manifold pressure is less than 55psig
28
Q

How is overpressure protection provided for the Bulk Oxygen System?

A
  1. The header is protected by a 2450psig relief, and the cylinders are protected by 2450psig rupture discs
  2. The oxygen supply lines are protected by a 150psig relief
29
Q

What is the normal system lineup for the Bulk Oxygen System?

A
  1. When catalytic recombination is not occurring the oxygen cylinders are isolated from the system
  2. When catalytic recombination is occurring normally one bulk storage cylinder is place in service, with one as a backup. Two cylinders can be placed in service at the same time.
30
Q

What are the precautions associated with the filling the Bulk Oxygen System?

A
  1. Keep oil and grease out of the oxygen system to prevent the possibility of combustion.
  2. Prevent sparks and open flame around the system
  3. Utilize a grounding strap, between the truck and the storage facility, to prevent issues associated with static electricity
31
Q

When are the Bulk Oxygen System cylinders changed out, and what notifications are required?

A
  1. The cylinders are changed out when pressure lowers to 95-105psig, this allows downstream pressure to be kept at 55-60psig
  2. When swapping cylinders open the regulator isolation for the oncoming cylinder before isolating the off going cylinder
  3. Notify the WCC SRO if oxygen needs to be ordered
32
Q

How many cylinders does the Nitrogen System utilize?

A

6 cylinders are utilized, located in the yard on the Unit 1 Turbine side inside of the Nitrogen House.

33
Q

How are the Nitrogen System cylinders categorized?

A
  1. E and F cylinders are the “normal” bank
  2. A and B cylinders are the “backup” bank
  3. C and D cylinders are the “emergency” nitrogen supply
34
Q

How are the Nitrogen Cylinders refilled?

A
  1. The cylinders are refilled normally from the onsite liquid nitrogen bulk storage tank
  2. The cylinders can be refilled directly from the from a nitrogen truck, but the trucks are normally at 3000 psig so filling must be performed with care
35
Q

What are the operating pressures of the two Nitrogen System headers?

A
  1. 100psig

2. 650psig

36
Q

What provides overpressure protection to the Nitrogen System?

A
  1. There are 2450psig rupture discs and reliefs for the supply
  2. The 100psig header has a 150psig relief
  3. The 650psig header has a 700psig relief
37
Q

How is pressure controlled in the Nitrogen System 100 header?

A
  1. The normal regulator will open to maintain the 100psig header at approximately 115psig
  2. The backup regulator will open to maintain the 100psig header at approximately 100psig
38
Q

How is pressure controlled in the Nitrogen System 650 header?

A
  1. The normal regulator will open to maintain the 650psig header at approximately 635psig
  2. The backup regulator will open to maintain the 650psig header at approximately 615psig
39
Q

How, and why, is the temperature of the nitrogen controlled in the Cold Leg Accumulators?

A
  1. The Cold Leg Accumulators have a nitrogen heater that remains energized
  2. The electric heaters heat the nitrogen in the supply line to the CLAs. This ensures that when the nitrogen expands in the tank through the inlet nozzle, the resulting drop in temperature does not cause thermal shock to the nozzle.
40
Q

What is the normal Nitrogen System alignment?

A

In the normal alignment the isolation valves for the “normal” cylinders and the “backup cylinders” are open so that the backup cylinders will automatically supply the system loads.

41
Q

What is the normal process for refilling the Nitrogen System cylinders?

A
  1. The nitrogen cylinders are normally filled from the onsite liquid nitrogen storage tank.
  2. The liquid nitrogen is pumped from the tank through a heat exchanger before it reaches the CLAs.
  3. The heat exchanger is used to ensure the liquid nitrogen is converted to a gas before it reaches the CLAs.
42
Q

When will the pump automatically stop when filling the Nitrogen System cylinders?

A

The pump will automatically stop when cylinder pressure is 2100psig The pump is not used when filling from the truck so the operator would have to be observant of pressure and manually stop the pump when pressure reaches 2100psig

43
Q

How are the Emergency Nitrogen cylinders placed in service?

A
  1. The normal and backup cylinders are isolated from the system.
  2. The emergency cylinders are place in service and the header isolation is opened so they can supply both the normal and backup headers.
44
Q

What are the safety precautions associated with the Nitrogen System?

A
  1. Extremely low temperatures

2. Asphyxiation

45
Q

What PPE is required while working near the Nitrogen Storage Tank?

A
  1. Face shield
  2. Gloves
  3. Rubber apron or equivalent
46
Q

What are the loads on the Hydrogen Bulk Storage System?

A
  1. Unit 1 Main Generator
  2. Unit 2 Main Generator
  3. Volume Control Tank
  4. Catalytic Hydrogen Recombiners(WGDTs)
47
Q

What are the loads on the Hydrogen Blanket System?

A

Nitrogen or Hydrogen to the Reactor Coolant Drain Tanks

48
Q

What are the loads on the Bulk Oxygen System?

A

Catalytic Hydrogen Recombiners

49
Q

What are the loads on the Nitrogen System 100psig header?

A
  1. Pressure Relief Tanks
  2. Volume Control Tanks
  3. Demineralizer Water Storage Tanks
  4. A and B Auxiliary Boilers
  5. Unit 1 and 2 Containment Valve Injection Water Surge Chambers
  6. Steam Generators
  7. Spent Resin Storage Tanks
  8. Waste Gas Decay Storage Tanks
  9. Drinking Water Tank
  10. Conventional Sampling Room
  11. WL and NB Evaporator Packages
  12. Cold Lab Furnace
  13. Unit 1 and 2 Gas Sample Panels
  14. Unit 1 Liquid Sample Panel
  15. Hydrazine Unloading System
50
Q

What are the loads on the Nitrogen System 650psig header?

A
  1. Unit 1 and 2 Cold Leg Accumulators

2. Fire Protection Pressurizer Tank(140psig)

Catawba Nuclear Station (72 decks)

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