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Catawba Nuclear Station > Containment > Flashcards

Containment Flashcards

1
Q

What is the purpose of the Containment?

A

The purpose of the Containment System is to limit the potential offsite radiation dose from a Design Basis Accident(DBA) to less than the values of applicable federal regulations.

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2
Q

What are the barriers to Radioactive Release?

A
  1. Fuel pellet - ceramic uranium dioxide fuel pellets entrap most of the fission products.
  2. Fuel Cladding - zircalloy sheath surrounding the fuel pellets.
  3. Reactor Coolant System - Rx Vessel and associated piping that contain any fission products that escape through fuel cladding defects.
  4. Primary Containment System or Steel Containment Vessel - Steel structure surrounding the Reactor Coolant System that is the final barrier against a significant release.
  5. Secondary Containment System - Concrete Containment and Annulus Ventilation System used to collect and process radioactive leakage from the Primary Containment.
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3
Q

What is the design of the Steel Containment Vessel?

A
  1. Vertical steel cylinder with a hemispherical dome, and a flat circular base.
  2. The Steel Containment Vessel encloses the Reactor Coolant System, provides biological shielding, and is a pressure boundary between the various containment volumes.
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4
Q

What is the design of the Concrete Reactor Building and Annulus?

A
  1. Three Foot thick reinforced concrete cylindrical structure used to provide environmental and missile protection for the Steel Containment.
  2. A six foot annular space exists between the Steel and Concrete Containment to allow for collection and processing of any release using the Annulus Ventilation System.
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5
Q

What is the design of the Containment Divider Barrier?

A

The Containment Divider Barrier splits the inside of Containment into upper and lower compartments to ensure that steam from a high energy release is routed to through the Ice Condenser.

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6
Q

What are some components of the Containment Divider Barrier?

A
  1. Submarine Hatch
  2. The Lower Ice Condenser Personnel Access Door
  3. Pressurizer Hatch
  4. Steam Generator Enclosures
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7
Q

What is the design of the Equipment Hatch Penetration and Cover?

A
  1. The Equipment Hatch Penetration and Cover are components of Steel Containment Vessel wall.
  2. The Equipment Hatch seal is a double o-ring design that must be type B leak rate tested.
  3. The Equipment hatch must be able to be replaced without AC power available.
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8
Q

What are the Containment Leakage Requirements?

A
  1. Allowable leakage is the maximum allowed Containment leakage rate at the peak containment pressure(14.68psig) resulting from the Design Basis LOCA.
  2. Allowable leakage may not exceed the license limit allowed in the UFSAR.
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9
Q

What are the two categories of leakage from the Containment Building?

A
  1. Leakage into the Annulus volume
  2. Leakage directly to the environment atmosphere know as bypass leakage.

Bypass leakage is limited to no more than 7% of the UFSAR limit under Allowable leakage conditions. The remaining leakage into the Annulus is filtered and will constitute approximately 93% of Containment leakage.

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10
Q

What are the normal administrative, Technical Specification, and design limits for Containment pressure?

A
  1. Administrative Limits: -0.08psig to 0.25psig
  2. Tech Spec limits: greater than or equal to -0.1psig and less than or equal to 0.3psig.
  3. Design limit: 15psig internal pressure/ -1.5psig external pressure
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11
Q

What are the Containment temperature Technical Specification limits?

A
  1. Greater than or equal to 75F and less than or equal to 100F for the Containment Upper Compartment.
  2. Greater than or equal to 100F and less than or equal to 120F for the Containment Lower Compartment.
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12
Q

What are the Containment design temperature limits?

A
  1. 317F in Steam Generator Compartment
  2. 297F average in lower containment
  3. 250F average in Containment overall
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13
Q

In what MODES can we operate with a reduced Containment temperature?

A

In MODES 2, 3, and 4 temperature may be reduced to 60F due to a lesser amount of energy released from the pipe break in these MODES.

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14
Q

How many Airlocks are there?

A

There are two Personnel Airlocks

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15
Q

Which Airlock barrier is considered the “first” and the “redundant” barrier?

A
  1. The Reactor side bulkhead is considered the “first” barrier.
  2. The Auxiliary Building side is considered the “redundant” barrier.
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16
Q

How man seals does each Airlock Door have?

A

2 seals per door, each providing full redundant Containment Integrity.

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17
Q

What system supplies air to the Airlock Door Seals?

A

The Instrument Air System(VI)

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18
Q

What provides a backup air supply to the Airlock Door Seals?

A

There are air tanks mounted on the Airlock Doors to provide a backup air supply. These tanks ensure seal operation for at least 7 days if Instrument Air is lost.

19
Q

What is the fail position of the Instrument Air valves that supply air to the Airlock Door Seals if power is lost?

A

The valves will fail open to ensure air is supplied to the seals. The valves are actually safety related, but their power supply is not.

20
Q

How many Airlock Door Seals are required to maintain Containment Integrity?

A

Only one out of four is required

21
Q

What is the precaution associated with inflating the Airlock Door Seals?

A

The doors must be closed when inflating the seals or they will rupture.

22
Q

What type of interlock do the Airlock Doors have, and can it be bypassed?

A

There is an interlock that prevents opening both Airlock Doors at the same time. This interlock gets defeated in the outage sometimes.

23
Q

What is the NORMAL procedure for entering the Containment from the Auxiliary Building?

A
  1. Depress OPEN pushbutton on the Auxiliary Building side to deflate Door No.2 Seals.
  2. Enter the Airlock and depress the Door No. 2 STOP pushbutton.
  3. Close the Outer Airlock Door and depress the Door No.2 CLOSE pushbutton to engage the pins and inflate the seals on the outer door.
  4. Once the seals are inflated on Door No.2, depress the OPEN pushbutton(key required) to deflate Door No.1 Seals.
  5. Once the Door No.1 Seals are deflated, open the door and enter Containment.
  6. Depress Door No.1 STOP pushbutton, and then slowly close Door No.1.
  7. Depress the Door No.1 CLOSE pushbutton to engage pins and inflate the seals on the inner door.
    * *Exit is the reverse**
24
Q

What is the EMERGENCY procedure for entering and exiting through the Airlocks?

A
  1. Disassemble the PALs to allow emergency access.
  2. The door viewports and latching pins are removed.
  3. Manual air valves are used to deflate the seals.
  4. Containment Integrity or Closure will be lost.
  5. Containment Operability is lost.
25
Q

What type of testing is done on the Airlock Door Seals?

A
  1. A between the seals leakage test is done within seven days of the last Airlock entry. This test checks for leakage past the seals.
  2. A seal internal pressure test is done every six months to ensure the seals will remain inflated for 7 days on a loss of Instrument Air.
26
Q

What are the Containment Entry Requirements?

A
  1. All Containment Entries are made in accordance with Site Directive 3.1.2.
  2. During normal power operation only the Lower Airlock Inner Door will be locked. This door will be controlled by Radiation Protection since this is an Extra High Radiation Key. The other Airlock keys are controlled by the WCC SRO.
  3. Opening the Outer Airlock Door does not constitute a Containment Entry. The Inner Door must be opened for a Containment Entry to have been made.
  4. Opening the CAD door to enter the Airlock is considered an Annulus Entry.
27
Q

How is Containment defined by Site Directive 3.1.2, and what is the Reactor Building?

A
  1. Containment is defined as the steel structure accessed by a Personnel Airlock or the Equipment Hatch.
  2. The Reactor Building includes the Annulus and Containment Structure.
28
Q

What is the purpose of establishing Containment Closure?

A

Containment Closure is the action to secure Containment and its associated structures, systems, and components of radioactivity in the event of a fuel handling accident or loss of decay heat removal cooling. The overall concern is to prevent the spread of radioactivity.

29
Q

When is Containment Closure required?

A
  1. Containment Closure shall be established during various combinations of decay heat load and reactor coolant inventory.
  2. Closure is established prior to entering “loops not filled” in MODE 5 and maintained until “loops filled”, Mode 5, is re-established.
  3. Closure may be suspended during NO MODE.
30
Q

What is the definition of Thermal Margin?

A

The time to core boiling upon loss of decay heat removal.

31
Q

What is the significance of Thermal Margin as it pertains to Containment Closure?

A

All open Containment Penetrations must be capable of being closed with the time to core boiling on a loss of decay heat removal.

32
Q

Where can you find Thermal Margin data?

A
  1. Logged on the Defense in Depth sheet every shift

2. Curves in the Data Book

33
Q

What is the purpose of the Containment Valve Injection Water System(NW)?

A

The Containment Valve Injection Water System provides a liquid seal between the gates of Containment Isolation gate valves to prevent leakage out of Containment past the discs.

34
Q

What is the basic system design?

A
  1. There are two redundant trains.
  2. Each train contains a surge tank with normal makeup aligned manually from the demineralized water(YM) system, and pressurized with nitrogen.
  3. Surge tank pressure and level are indicated in the Control Room.
35
Q

What are the normal and emergency sources of makeup water for the NW System?

A
  1. Normal makeup is manually aligned from the Demineralized Water System(YM).
  2. Emergency Makeup is automatically aligned from the Nuclear Service Water System(RN).
36
Q

What conditions will automatically align the assured source of water to the NW System?

A
  1. Low-Low Surge Tank Level AND Phase ‘A’ Containment Isolation signal.
  2. Low-Low Surge Tank Pressure AND Phase ‘A’ Containment Isolation signal.
37
Q

How and when are the NW System valves tested?

A
  1. The NW system is tested during each outage to ensure the system out-leakage does not exceed system capacity.
  2. The double check valves on the NW system supply lines to each serviced valve are checked also.
38
Q

What is Type A Leak Rate Testing?

A

Type A LRT - Tests to measure the Reactor Primary Containment overall integrated leakage rate(ILRT).

39
Q

What is Type B Leak Rate Testing?

A

Type B LRT - Tests to detect and measure local leaks of Containment penetrations, hatches, and personnel airlocks.

40
Q

What is Type C Leak Rate Testing?

A

Type C LRT - Test to detect and measure Containment Isolation Valve leakage.

41
Q

How is Type A Leak Rate Testing performed?

A
  1. All of Containment is pressurized to design pressure using large air compressors.
  2. Many fluid penetrations are drained.
  3. Frequency prescribed by CNS Containment Leakage Rate Testing Program.
  4. Total leakage rate cannot exceed max leakage assumed in the UFSAR.
42
Q

How is Type B Leak Rate Testing performed?

A
  1. Local leak check of mechanical bellows, maintenance, and electrical penetrations.
  2. Airlocks and the Equipment Hatch are subject to Type B testing.
  3. Total leakage is summed with Type C leakage and cannot exceed a predetermined value.
43
Q

How is Type C Leak Rate Testing performed?

A
  1. Test to measure leakage through a specific Containment process penetration.
  2. This leakage is considered “bypass” leakage because it bypasses the Secondary Containment.
  3. Total leakage from all valves summed with Type B leakage cannot exceed a predetermined value.
  4. Max total Type C leakage cannot exceed 7% of UFSAR max total assumed leakage.

Catawba Nuclear Station (72 decks)

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