NNI Flashcards
NNI system function
Provides alarms, indications, and control signals for system variable such as temp, press, flow, and level.
Encompasses all instrumentation other than Nuclear Instrumentation.
discuss a Type A variable
provides info req’d to allow operators to take manual actions for which no auto control is provided AND
are req’d for a safety system to do its safety function
Discuss Type B Variable
provide info to indicate whether plant safety functions are being accomplished such as:
- reactivity control
- core cooling
- maintain RCS integrity
- maintain containment integrity
Discuss Type C Variable
Provide info to indicate potential for breach of barriers to fission product release.
Discuss Type D variables
provide info to indicate the operations of ind. safety systems
Discuss Type E variables
provide info req’d to determine the magnitude of the release of radioactive materials and for continuously assessing such releases
Which variables are category 1? the most stringent cat.
A, B, & C
Which variables fall into category 2?
Type D & E
Which variables fall into category 3?
all backup variables fall into this cat.
What is a key variable?
single variable that most directly indicates the accomplishment of a safety function or indication of radioactive release
What is a backup variable?
additional variables to provide info to backup the key variables and allow diagnosis
NNI X is powered from ____.
NNI Y is powered from ____.
RS-1 or Y-02
RS-4 or Y-01
each channel has normal seeking ABT
Power supply monitor will trip the S-1 and S-2 switches when any DC power is lost for ____ seconds.
> 0.5 seconds
Smart Automatic Signal Selector (SASS) System does what?
SASS transfers to a redundant input when a rapid signal failure is detected.
Placing the mismatch alarm bypass switch to ON has ___ effect on auto transfer capabilities.
no effect
Ranges for RCS hot leg instruments and systems that use them.
3 dual element RTDs on each hot leg
Narrow range (520F-620F) -> remote shutdown, SASS, RCS Flow, Plant Computer
Wide Range (50-700F) -> SPDS
What does green dot (snake eyes) on a gauge mean?
This denotes a Reg Guide 1.97 instrument.
This instrumentation is acceptable to NRC for complying with regulations to provide instrumentation to monitor plant variables following an accident.
Ranges for RCS cold leg instruments and systems that use them.
Wide rang (50-700F) -> dasey panel and SPDS --also inputs to RCP I/L for 4th pump >465F
Narrow Range (520-620) -> Tave, Tdelta, cold leg Tdelta
Tave calculation and NNIs
NNI X calculates Loop ‘A’ average temp
NNI Y calculates Loop ‘B’ average temp
Unit Tave is calculated from the average Thot and Tcold signals
Tave, RCS Flow: which loop controls and when
Normally Unit Tave is in control
EITHER loop flow <95%, opposite loop auto selected for Tave control
BOTH loops <95% flow = either may be selected for Tave control
How is deltaT cold calculated?
Loop ‘A’ cold leg temp - Loop ‘B’ cold leg temp
Range is +-10F
How many RCS pressure instruments and where?
- 10 pressure transmitters
- Located on instrument racks 1 and 2 inside RB
- Tap into the hot legs on vertical piping leading to OTSGs
How many RCS pressure instruments feed into what.
- 4 supply the 4 RPS channels
- 3 supply the 3 ES channels
- 2 supply EFIC
Alarms for PZR hihi lolo and cv-1235 are on what paneL.
dasey panel
Interaction with RPS
RPS sense flow for input to the flux/delta flux/flow trip
RPS channel ‘A’ supplies Loop A/B flow to NNIX
RPS ‘B’ supplies RCS loop A/B flow to NNI Y
Purpose of ICCMDS (inadequate Core Cooling Monitor and Display System)
- advance warning and annunciation of approach to ICC
- tracking coolant inventory
- CET indication
- RCS level
- SCM calculation
- RV head fluid temp and level
what constitutes operability for hot leg level sensors?
1 wide range
2 narrow range
Each channel of ICCMDS uses what to calculate subcooling margin?
RCS pressure input AND
the average CET temp
Core Exit Thermocouples Tech Spec requirements
2 CET per core quadrant to be operable
4 modes of ICCMDS
- Maintenance = applicable train is considered inop
- Normal
- Shutdown = operator can adjust setpoints and disable points
- Refueling = used when reactor head is to be removed
what is the purpose of current buffer in the NNI system?
converts signal to usable range.
