FR-S Series

Question 1

What is the definition of a Condition II event?

Answer 1

• Faults that may occur with moderate frequency during the life of the plant.
• At most include a Rx S/D with the plant capable of returning to power.
• Shall not cause consequential loss of fuel cladding or RCS fission product barriers.

Question 2

List examples of Condition II events. (Anticipated Transients)

Answer 2

• Uncontrolled RCCA bank withdrawal from subcritical.
• Uncontrolled RCCA withdrawal at full power.
• RCCA misalignment.
• Uncontrolled dilution.
• Loss of flow.
• Cold water casualty.
• LOOP or turbine trip.
• Loss of feed.
• Excessive load increase.
• Turbine/Generator Overspeed.
• Accidental RCS depressurization.

Question 3

Define Anticipated Transient Without Scram, “ATWS”.

Answer 3

An unspecified common cause failure (either electrical or mechanical) which prevents the control rods from being inserted into the core in response to an anticipated transient. (Condition II event)

Question 4

What are the two Fission Product Barriers that could be challenged during an ATWS event?

Answer 4

• Fuel Cladding (DNBR)
• RCS System/Piping (Pressure)

Question 5

What is the design basis of the RPS (Reactor Protection System)?

Answer 5

• Maintain minimum DNBR.
• Maintain RCS pressure within design pressure.

Question 6

What is meant by “Imminent Nuclear Power Generation or Loss of Subcriticality”?

Answer 6

Condition in which the core should be shutdown by design, but does not meet the requirements of being shutdown. Ex:
- Not all control rods insert or control rods do not fully insert.
- RCS dilution.
- Excessive RCS cooldown.

Question 7

What is FR-S.1?

Answer 7

Response to Nuclear Power Generation/ATWS

Question 8

What are the entry conditions for FR-S.1?

Answer 8

• E-0 (Rx Trip or SI) step 1 when Rx Trip not verified and manual trip is not effective.
• F-0.1 (Subcriticality CSFST) Red or Orange path.

Question 9

What is FR-S.2?

Answer 9

Response to Loss of Core Shutdown

Question 10

What are the major action categories for FR-S.1?

Answer 10

• Verify auto actions or perform manual actions to reduce power.
• Emergency borate.
• Check for possible sources of positive reactivity and eliminate them.
• Verify subcriticality.

Question 11

What are the entry conditions for FR-S.2?

Answer 11

• F-0.1 (Subcriticality CSFST) Yellow path.

Question 12

What are the major action categories for FR-S.2?

Answer 12

• Check if loss of core shutdown is from core reactivity.
• Borate as necessary.
• Check for subcriticality.

Question 13

What is the order and means of boration during FR-S series actions?

Answer 13

• Emergency boration to suction of CCP’s as first option.
  -THEN-
• If SI not actuated, align CCP suction from RWST
  -OR-
• If SI not actuated, borate via normal flowpath.

Question 14

What must be initiated from the control room PRIOR to taking local actions for tripping the Rx and MT?

Answer 14

• Verify AFW pumps running.
• Emergency boration.
• Verify containment isolation.
• Check SI status.

Question 15

What challenges to fission product boundaries does an ATWS Loss of Load have?

Answer 15

• Most severe over-pressure transient (BOL is worst)
• No challenge to DNBR since pressure is so high.

Question 16

What challenges to fission product boundaries does an ATWS LOOP have?

Answer 16

• Moderate challenge to pressure.
• Severe challenge to DNBR since RCP’s (flow) is lost.

Question 17

Referencing CSFST Subcriticality, what is the basis for WR log power < 5%?

Answer 17

• Following a trip, Rx power should fall immediately to about 6% then quickly decay at -0.33 DPM.
• 5% was chosen because it’s clearly visible and ESF systems aren’t sized to remove that amount of decay heat.

Question 18

Referencing CSFST Subcriticality, what is the basis for WR power < 10^-5%

Answer 18

• This WR (gamma-metrics) is equivalent to P-6.
• Determines if power is shutdown in the IR or SR.

Question 19

Referencing CSFST Subcriticality, what is the basis for WR SUR negative or zero?

Answer 19

• If SUR is positive with power in the IR, the Rx will soon become critical.
• Severe challenge since there is no feedback to turn power in the IR.
• Power in the SR with a positive SUR is still a challenge, but not as severe since there is more time to criticality.

Question 20

Referencing CSFST Subcriticality, what is the basis for WR SUR more negative than -0.2 DPM?

Answer 20

• Following a normal shutdown, decay heat should reduce at -0.33 DPM or greater.
• SUR less negative than -0.2 DPM indicates that something is abnormal.

Question 21

What are the Immediate Actions for FR-S.1?

Answer 21

• Check Reactor Trip:
  
  • Rx Trip and Bypass Breakers Open
  • Rod Bottom Lights LIT
  • All rods < 10 steps
  • Lowering neutron flux
    RNO:
    
    • Manually trip Rx
    • If Rx will not trip, manually insert rods.
• Manually Actuate AMSAC
• Check Turbine Trip:
  
  • All turbine stop valve status lights LIT
    RNO:
    
    • Manually trip turbine
    • If manual trip did not work, actuate ATWS Runback
    • If load cannot be reduced, Trip all stop valves closed and verify stop valve
      dump valves closed.

Question 22

If rods are inserting in automatic at > 48 steps per minute during the immediate actions of FR-S.1, does the operator need to manually insert rods per the RNO?

Answer 22

NO
- If automatic is inserting >48 steps per minute, rods do NOT need to be placed in manual.

Question 23

While initiating emergency boration during FR-S.1, why is RCS pressure checked < 2335# and what actions are taken if it is?

Answer 23

• At or above this pressure, charging/SI flow is insufficient and therefore the boration is insufficient.
• If PZR PORV’s aren’t already open, they are opened manually to lower pressure < 2135#.

Question 24

What conditions are required to transition to SAG-1 (Severe Accident Management Guidance) from FR-S.1?

Answer 24

Five highest CETC’s are > 1200F
- Indicates that attempts to restore core cooling have failed AND core damage cannot be prevented.