Load Rejection

Question 1

State the entry conditions associated with the Load Rejection AOP.

Answer 1

RPCB, Turb Bypass demand and/or MT Trip alarms or indications.

Question 2

State the exit conditions for Load Rejection AOP.

Answer 2

4 conditions:

1: Decision made to s/d, Rx pwr ~ 20 % and directed entry into SPTAs
2. Rx pwr 2-12% and MGMT has directed MT restoration.
3. Rx pwr 2-12 %, CEAs positioned to support stable plant conditions, decision made to stay put.
4. Rx pwr 2-12% and decision made to shutdown.

Question 3

How is a RPCB manually actuated?

Answer 3

Press LLR and Drop Subgroup simultaneously.

Question 4

State the rx trip criteria associated with section 3 MT Tripped of RPCB.

Answer 4

• Power was ≥ 74%: auto and manual RPCB fails.
• CEA deviates from its subgroup > 6.6”, and any CEA Reg Groups are below the Transient Insertion Limits.
• S/G level trip setpoints (Hi or low) are challenged.
• CEA RG 3 inserts to < 60” withdrawn
• Power > 12% and SBCS Condenser Interlock actuated and can NOT be reset
• CPC ASI (Point ID 187) trip setpoints challenged (> ± .45 and trending to ± .5)
• Unit shutdown is desired while performing unit repairs.

Question 5

State the Rx trip criteria associated with section 4 PLR MT not tripped of RPCB.

Answer 5

• Generator load can NOT be stabilized AND RPCB is NOT in service
  
  • Trip turbine IF RPCB is in-service.
• CEA deviates from its subgroup > 6.6”, and any CEA Reg Groups are below the Transient Insertion Limits.
• CEA RG 3 inserts to < 60” withdrawn.
• S/G level trip setpoints (Hi or low) are challenged.
• CPC ASI (Point ID 187) trip setpoints challenged (> ± .45 and trending to ± .5)
• < 410 MWe: vacuum is between 4” and 5” HgA for > 1 hr or vacuum is > 5” HgA.

Question 6

State when breaking vacuum is desired for a Load Rejection.

Answer 6

The note and step in the AOP state that breaking vacuum may be desired if a rapid slowing of the MT is necessary for events such as a loss of Lube oil or lube oil fire.

Question 7

State the issues concerning placing SBCS in Local Auto or Individual SBCVs in manual.

Answer 7

Placing SBCS in Local Auto or individual SBCVs in manual will remove the ability for SBCS to generate an AMI signal. With CEAs in Auto Sequential, this will result in unwanted CEA insertion and a reduction in Rx power.

Question 8

Determine at what power the plant will be stabilized follwing a main turbine trip, why that power level and how the reduction is performed.

Answer 8

The plant will be stabilized at 12% power.

The reason for 12% is to

• allow canned CPC ASI values to be used,
• reduce condenser tube erosion,
• feed SGs using downcomers only,
• place FWCS in 1E,
• and place plant below LCO 3.2.3 Tq requirements. and 3.2.5 ASI.

The goal is to reduce power to < 12% within 90 minutes in a carefully controlled and deliberate manner. Only the boration amount needed for the downpower and the effectes of Xenon should be considered. DO NOT include boration adjustments for RG 4 restoration.

Question 9

Desribe the application of TS 3.1.7 CEA alignment.

Answer 9

3.1.7 does not apply for 2 hrs following a RPCB(LLR or LOFP).

Question 10

Describe the strategy for achieving a smooth downpower to 12%.

Answer 10

Borate to start the downpower accounting for only the amount needed to go to 12%.

Restore CEA RG 4 during the downpower (RG3 - 95” = RG4)

Stop borating at ~17% and allow Xe to continue (-) reactivity effects.

Stabilize ~10-12% by CEA withdawal or dilution.

Restore CEA limits

LCO 3.1.7 conditions would be entered at the 2 hr point if CEAs were still below.

Time below insertion limits is still tracked.