TMMs
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Effects of loss of Y10/20/30/40 on TMMs
 if power is lost you will lose TMM channel and associated RPS channel will trip
 if only lose power to the TMM w/ associated RPS channel still energized, the associated TM/LP trip setpoint fails low, and the VHPT and ASI alarm will trip

Function of the power peaking function generator in the TMM?
generates the power portion of the DNB penalty calculation for the TM/LP trip setpoint

Purpose of the thermal margin/ low pressure (TM/LP) trip
 ensures fuel protection during slow reactivity addition transients starting at low reactor power
 allows S/G tube plugging while maintaining 100% power
 MDNBR safety limit is 1.17(xnb fuel), 1.154(anfp) or 1.141(HTP fuel)

How many times and why do you press the "clr" key prior to taking the TMM to the "Data Modify" mode?
 6 times minimum
 this clears the buffer
 when any TMM constant has been changed you must verify all other constants prior to exiting "Data Modify" mode

When is it not allowed to reset the VHPT setpoints?
during plant transients

EK06D3/D4/D7/D8 "Nuclear (delta) T power deviation/ Tinlet off normal/calculator trouble channel A,B,C,D"
 8 second time delay
 NucleardeltaT: 3% deviation
 Tc Max543.5F
 Tc Min525F
 calculator trouble

Delta T power (B) signal generation
 Inputs from Tc and Thave used to generate delta T power
 Bias term set in TMM adjusts for heat balance
 only TMM parameter we adjust

When do you reset the VHPT setpoints during power escalation?
prior to escalations above 28.5% and prior to reaching the pretrip setpoint (</= to 13.5% delta T power) during power escalation

Qdnb
penalty in the Pvar formula that causes the trip setpoint to rise due to an abnormal ASI

LOCA peaking function generator
 takes higher of delta T power or summed NI power via the LPD (low power density) block
 provides for adjustments to the ASI alarm setpoint based on LOCA considerations
 LOCA peaking function not used

What defines the operating envelope for the cores Axial Shape Index?
local power density function generator

Purpose of Axial Shape Index (ASI) alarm
 alerts operator that core axial flux shape is approaching the limits assumed in the safety analysis for Tinlet LCO technical
 assures core axial shape is maintained w/in the boundaries of the safety analysis

What criteria must be met to reset the VHPT setpoints during stable plant conditions?
 Rx power has not changed more than 1/2% for 10 minutes following a transient
 all control rods are withdrawn above PDIL
 PZR press is between 20102100 psia, is controlled, and is approaching NOP of 2060 psia
 Tave is within 3F of Tref and is controlled
 PZR level is controlled between 4060% and is approaching normal programmed level
 Both S/G levels are between 6070%

Purpose of the Thermal Margin Monitors?
 provides thermal margin/low pressure (TM/LP) trip setpoint to RPS
 prvides the Variable High Power trip (VHPT) signal to RPS
 provides an alarm when ASI is unacceptable prior to exceeding tech specs
 provides and alarm if any of the following exist:
 delta Tnuclear power deviation
 TMM calculator trouble
 Tc alarm

When may calibration of TMM deltaT power be required?
 if heat balance differs by more than +/ 1% from indicated deltaT power on any TMM "primary screen" OR
 calibration of deltaT power indication channels is desired

ASI alarm development
 TMM provides an alarm prior to the ASI exceeding TS limits
 uses excores to calculate ASI
 converts it over to an axial offset signal through the ASI function
 compares to the operating box created by the local power density function which takes the higher of NI/deltaT power

How does the VHPT setpoint change w/ power changes?
 Qtr follows power going down
 Qtr must be manually reset on power going up
 resetting VHPT setpoint
 pushing VHPT reset ( 1for each channel) on C02
 can reset on each channel drawer
 TMM only recognizes reset once every 10 seconds

Pvar
 Pvar is the low pressure trip limit
 Pvar calculated using Tc and Qdnb penalty
 higher of Pvar and Pmin (1760 psia) auctioneered to give you Ptrip

TM/LP trip and pretrip alarm
 Ptrip
 higher of Pvar and Pmin(1760 psia)
 setpoint displayed on C12
 Ppretrip=Ptrip + 50psia
 TM/LP setpoint low alarm is generated if the TM/LP setpoint drops to 1720 psia indicating a circuit failure

Axial Function Generator
 for a given ASI (Yi) the axial function will calculate Qa, which is used as a factor in computing the penalty factor Qdnb
 Qa
 ASI penalty portion of Qdnb
 a negative ASI will produce a greater DNB penalty into the Pvar equation than a positive ASI

Inputs for VHPT operation of VHP function generator
 takes higher of deltaT power and summed NI power
 Q is measured against 2 setpoints
 Qptrpretrip alarm=Q + 13.5%
 Qtrtrip level=Q + 15%
 Qtrmin=30%
 Qtrmax=106.5%
 Qptrmin=28.5%
 Qptrmax=105%

Local Power Density Function Generator
 computes the maximum allowable ASIs(+/) for the existing power level (QR2)
 QR2 takes higher of deltaT power and NI summed power through LOCA peaking function generator
 trip alarm is generated if ASI, Yi exeeds Yp or Yn
 not a CR annunciator
 reported on "status" screen of TMM
 pretrip alrm is not used

Power Peaking Function (QR1)
 input is Q1, which is higher of deltaT power(B) or summed NI power
 power peaking function is shorted therefore Q1=QR1
 power portion of the DNB penalty

Where is deltaT power sent?
 to determine Tcal
 has no effect because it is multiplied by a constant Kc=0
 sent to determine power peaking function which determines Qr1 for TM/LP setpoint calculation
 deltaT also sent to VHPT and ASI alarm calculation
 deltaT power indications on C02 and C27

Tc max and Tc min Alarm Setpoints
 Tc max=543.5F
 Tc min= 525F
 brings in alarms EK06D3,4,7,8 annunciators
 alarms also brought in by a TMM calculator trouble alarm override (internal error logic)

Inputs for TM/LP trip portion of the TMM?
 higher of the 2 Tc signals
 provides input to Pvar setpoint calculation
 provides input to calculate deltaT power (B)
 2 Th are measured and averaged
 average signal sent to determine deltaT power (B) signal

Power supplies for the Thermal Margin Monitors?
 Y10,20,30,40
 2 battery backup systems

Inputs to the Thermal Margin Monitors?
 Tcold X2
 Thot X2
 NI power range
 upper
 lower
 combined

Purpose of Variable High Power Trip (VHPT)?
 provides capability to limit transients quickly beginning @ low power levels, w/out operator action
 functions to trip the reactor when the greater of NI power or deltaT power exceeds a preset high power trip value

What must be done to enter new bias terms into the TMM?
 bypass VHPT
 bypass TM/LP
 record date and time in SOP35 att 4
 press clear on TMM at least 6 times to clear out the numbers in the memory

Outputs from the Thermal Margin Monitors
 nuclear power/ VHPT setpoint and pretrip alarm
 TM/LP pretrip alarm setpoint
 TM/LP setpoint and VHP trips to RPS channels
 TM/LP setpoint low alarms (1720 psia)
 multifunction alarms on EK06D

ASI function generator
 provides relationship between Ye (input) and Yi (output) using the shape annealing factor S.A.F.
 S.A.F. corrects for bleedover or shine on the excore NIs
 output of ASI function is sent to the axial function generator and to the ASI alarm comparators (via LPD block)
 function of LPD block is to disable the ASI alarm (15% ascending, 14.5% descending)