Week 7: Simulator Morning Questions

Question 1

There are 3 transitions in the first 4 steps of E-0. What are they and where do they occur?

Answer 1

Transition to Failure to Trip, Step 1
Transition to Loss of All AC Power, Step 3
Transition to Trip Recovery with no SI, Step 4

Question 2

What are the 5 actions on the foldout page of E-0?

Answer 2

RCP Trip Criteria
Cold Leg Recirculation Criteria
Ruptured SG Criteria
Faulted SG Criteria
AFW Switchover Criteria

Question 3

Which of the 3 major events (LOCA, HELB, SGTR) is checked for first in E-0? Why?

Answer 3

HELB, Fairly unique indicators of this event, so it can be quickly determined if this is the event in question

Question 4

List the 6 critical safety functions in order of priority.

Answer 4

Subcriticality (S)
Core Cooling (C)
Heat Sink (H)
Integrity (P)
Containment (Z)
Inventory (I)

Question 5

Why do we trip RCPs at 1375 psig on LOCA?

Answer 5

If we don’t, the potential exists for the RCPs to pump more water out of the break (and out of the core) than assumed by the safety analysis.

Question 6

List the symptoms of a LOCA.

Answer 6

PZR level drops
PZR pressure drops
High containment pressure
Sump level increasing

Question 7

Differentiate between a leak, small LOCA, and a large LOCA.

Answer 7

Leak: 1 charging pump can maintain PZR level
LBLOCA: decay heat completely removed through break
SBLOCA: requires SG as heat sink

Question 8

How is energy removed from the RCS on a LOCA?

Answer 8

Out the break for LBLOCA
SGs first on SBLOCA

Question 9

What are the SI termination criteria?

Answer 9

At least 4% level in the PZR
RCS pressure stable or increasing
Either 260 MPPH or 4% level in at least 1 SG
Greater than 30 degrees of subcooling

Question 10

What are the T.S. allowable leak rates?

Answer 10

No pressure boundary leakage
1 gpm unidentified leakage
10 gpm identified leakage
150 gpd P-S leakage through any 1 SG

Question 11

Plant is at 100%. Loop 2 Thot fails high. Describe the plant response.

Answer 11

Rod control uses the auctioneered high Tavg signal, so the failed loop 2 Tavg indicates that the RCS is too hot. Rod control drives in rods in response.

Question 12

List the immediate actions of E-0, including the RNOs.

Answer 12

Verify Rx trip (DRPI at bottom, trip breakers open, IR current decreasing) - RNO manually trip reactor
Verify Turbine trip (Main stop valves closed) - RNO manually trip turbine, pull to lock EHS pumps
Verify power to NB busses - RNO start diesel generators
Verify SI actuation - RNO verify SI not required, if it is, manually initiate both trains

Question 13

List the 6 preempive actions.

Answer 13

Reduce AFW to SGs to limit cooldown
Isolate faulted SG
Mitigate Tavg heatup from SG dryout
Isolate ruptured SG
Switch steam dumps to pressure mode when RCPs tripped
Trip RCPs associated with stuck open PZR spray valves

Question 14

What is ES-0.0? When can you use it?

Answer 14

Re-diagnostic procedure, use when Rx is tripped with SI actuated or SI required

Question 15

What is the plant response to a failed high PZR level channel with no operator action?

Answer 15

CCP flow reduces, actual PZR level reduces, eventually PZR level reaches LTDN isolation setpoint, PZR level begins to rise through seal injection, PZR level rises to Rx trip setpoint

Question 16

Why is 4% level in ruptured SG required before isolating?

Answer 16

Need to ensure the U-Tubes are covered, such that some particulate is filtered out by the feedwater and so that the primary cooldown does not cool down the secondary system (so that we can equalize primary and secondary pressure).

Question 17

What are the operational challenges in dealing with a SLB?

Answer 17

Uncontrolled cooldown of RCS, followed by a heatup of the RCS that must be mitigated in order to avoid filling the PZR

Question 18

List three industry/operational changes that resulted from TMI.

Answer 18

Emergency procedures moved from Event-based to Symptom-based
Unified media response
Industry-wide emphasis on sharing and learning from OE

Question 19

What does AMSAC do? Explain how this mitigates an ATWS.

Answer 19

Mitigates transients in the event of a failure to trip.
Tripping the turbine and actuating AFW

Question 20

Is a SLB more severe at BOL or EOL? Why?

Answer 20

EOL; MTC is much more negative, resulting in a more extreme RCS cooldown