NNI Flashcards
What’s the purpose of Reg Guide 1.97 instruments?
Identifies the minimum set of instrumentation required to give control room indication during accident situations.
How many reg guide 1.97 types are there and what are they?
Type A: provide information required for operators to take specific manual actions which no automatic control is provided and required for safety function
Type B: Provide information to whether safety functions are being met. (Rx control, core cooling, RCS integrity, containment integrity)
Type C: Provide information to indicate potential for breach of fission product barriers
Type D & E are for operation of individual safety systems and determination of releases
How many reg guide 1.97 categories and what are they?
1) Category 1: most stringent requirements and is intended for key variables (Types A,B,C)
2) Category 2: less stringent requirements and applies to instrumentation designated for system operating status (Types D/E)
3) Category 3: Ensures high quality instrumentation is obtained and applies to backup and diagnostic instrumentation. (Backup variables)
What are the power supplies for NNI X and Y? How do the power supply monitor circuits work?
NNI X: RS-1 and Y-02
NNI Y: RS-4 and Y-01
Power supply monitors acre auctioneered to provide a (+) and (-) 24 volt signal. Loss of either the +/- 24 volts will cause both S-1 and S-2 breakers to trip and loss of power.
AC power is normal seeking with 10 minute time delay which provides instrument power.
Which parameters are SASS Selectable?
- RCS pressure
- RCS Tc
- RCS Th.
- RCS flow
- OTSG pressure
- Header pressure
- Main Feedwater Flow
- Main Feedwater Temperature
- OTSG S/U level
- OTSG Operate Level
- Reactor Power
Which instrument is normally selected to both NNI X and Y at all times?
Tcold instrument is aligned to both NNI X and Y instruments.
What function does the alarm bypass provide?
Placing the switch in bypass will defeat the mismatch signal from the associated channel to the annunciator which allows another channel to actuate the control room mismatch annunciator?
What indications are provided on the dasey panel?
Tcold
Wide range RCS pressure
OTSG Pressure
PZR Lvl
MU Tank Level
OTSG SU level
Source range
Int range
How does the Tave indication work?
Unit Tave is normally selected if RCS loops A and B flows are 100%. The signal is generated from the averages of A loop and B loop Tcold and Thot averages.
If A loop flow is < 95% (Example C RCP trip) then Tave will be selected to the B loop. Likewise for B loop.
If both loop flows are < 95%, then either loop is selectable.
Which RPS channels provide input to RCS flow instruments? Pressure instruments?
Pressure instruments are fed from A and C RPS channels
Flow instruments are provided from A and B instruments
What is the RCS pressure input to ERV LTOP setpoint?
PT-1020 (RCS wide range pressure)/ES channel 1 analog RCS pressure input
What is the NNI RCS pressure input for CV-1050/1410 decay heat suction valves?
ES analog channels 1 & 2 wide range RCS pressure instruments (PT-1020/PT-1022) input to 1050/1410.
Describe how the Reactor vessel level monitoring system works?
2 reactor vessel level probes monitor water level above the core from top of the fuel alignment plate to top of the dome of vessel head.
The level sensors consist of 2 thermocouples connected to provide a delta temp output. One thermocouple is heated by an internal heater wire and has a different heat transfer coefficient to the RCS. When steam surrounds the thermocouples, the heated ones temperature will increase resulting in an increased delta T between the 2. When this occurs the indicator will show that its dry.
What 4 things are selectable for pressurizer level?
PZR level control
HI/HI alarm
Dasey panel
LO/LO alarm (PZR Heater Interlock)
What is the range for narrow/wide range Thot? What does it provide temp compensation for?
Wide range: 50 - 700 degrees F
Narrow range: 520 - 620 degrees F
Narrow range Thot provides temperature compensation for RCS flow
What is the range for narrow/wide range Tcold? What does wide range supply? Narrow range?
Wide Range (50 - 700 degrees F) - Dasey panel, RCP Tcold interlock
Narrow Range (520 - 620 degrees F) - SASS, Tave input, delta T, Delta Tcold
Which RCS pressure instruments supply DROPS, SPDS and ICC?
Wide Range RCS Pressure (PT-1041/1042)
Explain the RCS pressure heater, spray, ERV circuit? What component is not affected by the 125# bias?
ERV not affected by 125# Bias.
PT-1021/1038 RPS Channel A and C pressure inputs supply RCS pressure control circuit which is NNI X only.
Describe components controlled by narrow/wide range RCS pressure
What indications can be read on ICCMDS screen?
RV Level
Hot leg Level
RV head temp
RCP status
CET AVG Temp
Operating Mode
SCM
RCS Pressure
