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LOIT 2024 > COLSS > Flashcards

COLSS Flashcards

1
Q

What is the purpose of Core Operating Limit Supervisory System (COLSS)?

A

Purpose:
* Assists in ensuring AOOs will not result in exceeding SAFDL’s and acceptable accident consequences, as long as CPCs trip as expected.
* COLSS provides alarms/indications. CPCs provide the trips.

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2
Q

What is the Linear Heat Rate Power Operating Limit (POL)? Why?

A

Linear Heat Rate LCO:
* Operating limit (POL) ensures 13.1 kW/ft Tech Spec limit is not exceeded.
* Ensures ≤ 2200°F peak fuel cladding temperature during a LOCA.
* Peak centerline temp safety limit (5080°F) based on preventing fuel centerline melt. (21 kW/ft Hi LPD trip bases)

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3
Q

What computers support COLSS?

A

Two computers / different Analog to Digital converters
* Core Monitoring Computer (CMC) - normally used to drive the output devices (meters).
* Plant Computer (PC) - back up to the CMC.
* Both part of Plant Monitoring System (PMS / RJ).
* If PMS is failed, COLSS is inoperable.
* Some inputs / input hardware is shared. Failures may affect both.

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4
Q

What is the purpose of the DNBR POL?

A

DNBR Margin LCO:
* Operating limit (POL) ensures the most rapid DNB Transient from an AOO does not result in **DNBR < 1.34. **

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5
Q

What does COLSS use CEA Positions for? How?

A

CEA Positions
* Radial Peaking Factor calculations
* Relative Power calculations (compensated for CEA Insertions and Fuel Burnup)

  • **COLSS uses the lowest CEA position in a group, and deviation between highest and lowest CEA in a group. **
  • Signal from pulse counters (demanded position).
    ** Dropped rod (DRC): pulse counter position is reset to zero. **
    o *COLSS thinks entire group is on the bottom     and affected group has a deviation. (Conservative)
    * If one rod slips or sticks (partial insertion): COLSS no longer knows the rod position.* (Non-conservative)
    o Position must be manually entered into PMS.
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6
Q

What does the Power Limit Margin Meter display?

A

Power Limit Margin Indicator (one for CMC / one for PC output)
* Displays the margin to most restrictive power limit.
* Smoothed plant power compared to license power, DNBR POL and KW/FT POL.
* Most restrictive value (smallest margin) is displayed.

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7
Q

What does the Reactor Power Meter display?

A

Reactor Power Meter
* Displays the unsmoothed value of Plant Power.
* **Displays the larger of Calibrated ∆T Power or Turbine Power ** if inputs to the power calculations are valid.

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8
Q

What is the equation for JSCALOR?

A

Calculated Secondary Calorimetric
JSCALOR = (hSTM) (FW flow-BD flow) + (hBD) BD flow - (hFW ) FW flow + energy losses – energy gains

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9
Q

How does changing blowdown flow affect JSCALOR?

A
  • Raising SGBD flowrate cause JSCALOR to drop. (COLSS sees some of FW entering the SG not being turned into steam.)
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10
Q

What is the equation for NKBDELT?

A

∆T Power Calculation
* COLSS uses Th, Tc, PPZR, and RCP mass flow rates for calculation of enthalpy difference. [Q = ṁ(Δh)]
* NKBDELT: uncalibrated ∆T power.
* ∆T power is then calibrated by the secondary calorimetric power (JSCALOR).
* Calibrated ∆T power then becomes JCPCAL.
(JCPCAL has a quicker response than JSCALOR).

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11
Q

What power calculation is normally used at steady state power operations?

A

JSCALOR: Used when steady state (more accurate)
* Not as accurate during a transient
* Used to calibrate excore NIs

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12
Q

How is turbine power calibrated?

A

COLSS correlates turbine first stage pressure (TFSP) to power.** It is calibrated to the secondary
calorimetric** (with the same time constants as for JCPCAL).
NKBTFSP = turbine power.
NKCBTFSP is NKBTFSP calibrated by the JSCALOR (secondary calorimetric) value.

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13
Q

What actions are required if JSCALOR is INOP? How long to complete?

A
  • If JSCALOR inoperable - operate on plant power for 12 hours while not raising power. **> 12 hours, lower power to < 96.6%. **
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14
Q

What is the concern with fuel cladding exceeding 2200 F?

A
  • Prevent fuel clad failure during a LOCA by maintain cladding ≤ 2200°F
    o **2200°F **causes severe cladding failure by oxidation (zirc-water reaction)
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15
Q

How does COLSS calculate Steam Generator Blowdown Constants?

A

Secondary Calculations vs Blowdown Constant
* SGBD is manually entered
* ↑ SGBD flow = ↓ FF = ↓ JSCALOR

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16
Q

If Steam Generator Blowdown actual flow stops and constants are not updated in COLSS, is displayed power conservative or non-conservative?

A
  • If actual SGBD flow stops and constants NOT updated, actual power will lower (less feed flow).
    o JSCALOR will read lower than actual (non-conservative) (updates fully in 1 hour
17
Q

How does COLSS respond to loss of pulse counters?

A

COLSS is INOP

Rod position (CEAs)
* If no rod position is available, COLSS is inoperable. (No substitution)
* Uses group position and group deviation is sent.
* Rod insertion will lower both POLs (radial peaking factors rise).

18
Q

How does COLSS respond to a loss of In-Core Instruments exceeding the TRM limit?

A

Incore instruments
* If < TRM number of incores, COLSS is inoperable. (No substitution)
* Any tilt will lower both POLs.
* ASI higher in core (-ASI) will lower DNBR POL. (higher flux in hotter part of the core)

19
Q

What input sensors can COLSS substitute?

A

Primary (RCS) sensors and Steam flow

20
Q

What’s the purpose of Tcold Compensation in COLSS?

A

Tcold Compensation
* Corrects measured Tcold for sensor dynamics and inlet plenum mixing delays.
o Makes COLSS more responsive during a transient.

21
Q

What is “Relative Power” in COLSS?

A

Relative Power
* Incore NI signal should represent the flux in its region in the core. May be affected by:
o CEA insertion in an instrumented F/A
o Instrumented F/A with a different exposure history than other F/As in its region. (higher flux for same power)
o Detector Burnup
* Compensated for by tracking the exposure of instrumented Fuel Assembly, by CEA position and exposure of detectors.
o Signal is modified based on assembly exposure (called the burnup file in COLSS).
o Rhodium decay and signal delay time.

22
Q

How does a change in Tcold affect COLSS?

A

T-cold
* If one T-cold fails, COLSS will substitute the other detector (no effect on COLSS).
* ↑ T-cold = ↓ DNBR POL (~ 1% per 2°F ↑)
* Deviation from 555°F causes radial peaking factors to rise (causes KW/FT POL ↓)

T-cold vs. Plant power
* Same as Thot, but opposite direction [↑Tc = ↓NKBDELT]

23
Q

If JSCALOR is reading less than actual reactor power, is this conservative or non-conservative?

A

Non-conservative

24
Q

If Feedwater temperature goes up (stays within range), how does JSCALOR respond?

A

Feedwater temperature vs. plant power calculations
* One fails - JSCALOR is BAD (COLSS still operable).
* **↑ FW Temp (hFW ↑) **= ↓ JSCALOR (PP will indicate lower in ~ 1 hour)

25
Q

How does COLSS select Plant Power (PP)?

A

Plant Power (PP)
* Larger of JCPCAL (calibrated 1° calorimetric power) or NKCBTFSP (calibrated Turb power) becomes plant power (PP)

26
Q

How does COLSS respond to lowering Pressurizer Pressure?

A

* ↓ pressure = ↓ DNBR POL. (~ 1% per 20 psi ↓)
* Pressure has minimal effect on LPD POL (no change).

27
Q

How does COLSS respond to Thot going up?

A

* ↑ Thot = ↑ NKBDELT
o Reflected in plant power (auctioneered high) until calibrated back down by JSCALOR (~ 1 hour).
* ↓ Thot = NKBDELT ↓ momentarily until calibrated up by JSCALOR

28
Q

How does COLSS respond to RCP ΔP going up?

A
  • ↑ RCP ΔP = power unaffected (NKCBTFSP would be higher)
  • ↑ ΔP = ↓ DNBR POL
  • Flow drops as you are closer to shutoff the head (↑ ΔP = ↓ flow)
29
Q

How does COLSS respond to RCP ΔP going down?

A
  • ↓ RCP ΔP = ↑ indicated power (until calibrated back down by JSCALOR)
30
Q

How does COLSS calculate Azimuthal Tilt (AZTILT)?

A

Azimuthal Tilt (AZTILT) Calculation
* Uses incores NIs
* Calculations are performed at 5 levels in the core and averaged to give core AZTILT
* If the number of calculations is less than the Tech Spec value, COLSS will set AZTILT to BAD (COLSS is inoperable).

31
Q

How will COLSS respond to a slipped CEA?

A
  • AZTILT would rise if a rod is slipped, due to ICI seeing flux shift
  • CEA NOT fully withdrawn will result in both POLs being lower (higher RPFs)
32
Q

How does COLSS calculate Planar Radial Peaking Factor?

A

Planar Radial Peaking Factors (RPFs) Calculation
* Peaking factor for each of 20 axial levels in the core is computed using:
o CEA data
o RCSVAV (average inlet moderator specific volume based on T-cold).
o For each level, the peaking factor is determined from lookup tables
o** Any Tcold deviation from 555°F **will cause radial flux distribution to get worse.
* Incore information is NOT used to determine radial flux distribution

33
Q

How does the DNBR POL change as ASI becomes more negative (power to the top of the core)?

A

DNBR POL will lower

  • ASI higher in core (-ASI) will lower DNBR POL. (higher flux in hotter part of the core)
34
Q

What mode of operation must COLSS be in to be OPERABLE

A

Scheduled

  • COLSS is not operable in any mode but SCHEDULED.
35
Q

How does COLSS respond to ASI becoming more positive (power moving down in the core)?

A

DNBR POL will rise (more margin)

LOIT 2024 (69 decks)

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