LOCA Flashcards
When must Hydrogen Analyzers be placed in service?
Within 30 minutes of the LOCA
What must be verified prior to restoring Containment cooling, and why?
Why is restoration of Containment cooling desirable?
There is no water level in Containment.
This is due to the potential for submergence and eventual failure of NC and WC inside containment isolation valves.
Containment cooling should be restored to promote Hydrogen mixing and remove heat in order to stop CS sooner.
What are the SAIS Load Shed panels, and why should they be restored?
NHN-M71, NHN-M72, NHN-M19, NHN-M20, QBN-D90, QBN-D91.
Ensures OPERABILITY of AFN-P01, Essential Lighting, and Containment Cooling.
Why are Condenser Reheater trays levels checked?
What must be done if level cannot be verified to be within the indicating range?
If an MSIS has been actuated, AFA-P01 critical steam traps M23 and M24 are isolated.
Overriding and opening the isolations will help ensure OPERABILITY of AFA-P01.
If level is above the indicating range, the potential exists that water has backed up into the steam lines, which presents a water hammer concern.
If this is the case, manual blowdown of the steam lines per 40OP-9SG01 must be performed within 2 hours.
What is providing RCS Heat removal for both Large and Small Break LOCA?
Large Break: RCS break flow and ECCS flow cool the Reactor Vessel. SG are decoupled from RCS.
However, if SG is cooler than RCS they can act as a heat sink, therefore, SGs should be cooled down.
Small Break: Steam Generators maintain RCS heat removal and allow for depressurization of the RCS to allow for HPSI flow, therefore SG heat removal must be maintained.
What must be done for both of the following conditions:
a. P/T limits are exceeded?
b. 100F per hour limit is exceeded?
A. If a cooldown is in progress, stop the cooldown. Depressurize the RCS. Control CH, letdown, and SI flow if HPSI throttle criteria is met.
B. Stop the cooldown, maintain stable pressure and temperature, and recommence cooldown
What are some indications of RCS voiding?
∙LD flow > CH flow.
∙PZR level rising significantly more than expected while operating main spray.
∙RVLMS < 100%
∙HJTC unheated thermocouple indicated saturated conditions in RVUH.
How is Natural circulation verified? What is directed if natural circulation is not verified?
∙Loop DeltaT < 65F [65F]
∙Tc and Th stable or lowering
∙CET subcooling > 24F [44F]
∙<30F [30F] difference from Th and max CET
∙If Nat Cir not verified, ensure proper control of SG feeding and Steaming
What should be done following a RAS if any RAS sump isolation valve will not open?
Secure any running HPSI and CS pump in the associated train
If a RAS has actuated, what should be done if a loss of ECCS suction is occurring?
∙Stop CS pump on affected train.
∙Check that HPSI performance improves.
∙If it does not and 2 HPSIs are running, secure the affected HPSI pump.
∙If only 1 HPSI was inservice, throttle SI flow to achieve 250 gpm.
∙If no CS pumps are in service, GO TO FRP.
Why is Hot and Cold leg injection initiated for a large break LOCA but not a small break LOCA?
During a large break LOCA on one of the RCS cold legs, it is assumed that all of the SI flow from the injection point associated with that cold leg goes out the break. In addition, some of the fluid injected into the other legs is directed out the break such that the water flowing to the core is just enough to make up for boiloff. Over time, this boiling in the core could concentrate the boric acid to the point where it begins to plate out on the core surfaces and begins to interfere with adequate core heat removal. Therefore, the mode of SI flow is switched from cold leg only to simultaneous hot and cold leg injection sometime into the event.
In this mode of operation, the HPSI Pump discharge is aligned so that the total injection flow is divided equally between the hot and cold legs. Injecting to both sides of the reactor vessel will ensure that fluid from the reactor vessel (where the boric acid is being concentrated) flows out the break (regardless of the break location) and is replaced with the dilute solution of borated water from the other side of the reactor vessel.
Simultaneous hot and cold leg injection is not required for small break LOCAs because the buildup of boric acid is terminated when the RCS is refilled. Once the RCS is refilled, the boric acid is dispersed throughout the RCS via natural circulation.
