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Advanced Systems > Nuclear Instrumentation > Flashcards

Nuclear Instrumentation Flashcards

1
Q

LCO 2.1.1 “Reactor Core Safety Limits” requirement

A
  • DNBR shall be maintained at or above the following correlation safety limits: XNB - 1.17, ANFP - 1.154, and HTP - 1.141
  • LHR shall be maintained <= 21.0 kW/ft
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2
Q

LCO 2.1.1 “Reactor Core Safety Limits” applicability

A

Modes 1-2

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3
Q

LCO 2.1.1 “Reactor Core Safety Limits” required action if DNBR or LHR not within safety limits

A

WITHIN 1 HOUR restore compliance and be in Mode 3

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4
Q

LCO 3.2.1 “Linear Heat Rate” requirement

A

LHR shall be within limits specified in the COLR, and the incore alarm system or excore monitoring system shall be operable to monitor LHR

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5
Q

LCO 3.2.1 “Linear Heat Rate” applicability

A

Mode 1 with thermal power > 25% RTP

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6
Q

LCO 3.2.1 “Linear Heat Rate” required actions if LHR not within limits specified in the COLR, as determined by 4 or more coincident incore channels, excore monitoring system, or manual incore readings

A

WITHIN 1 HOUR restore LHR to within limits

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7
Q

LCO 3.2.2 “Total Radial Peaking Factor” requirement

A

Total Radial Peaking Factor shall be within the limits specified in the COLR

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8
Q

LCO 3.2.2 “Total Radial Peaking Factor” applicability

A

Mode 1 with thermal power > 25% RTP

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9
Q

LCO 3.2.3 “Quadrant Power Tilt” requirement

A

Quadrant Power Tilt shall be <= 0.05

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10
Q

LCO 3.2.3 “Quadrant Power Tilt” applicability

A

Mode 1 with thermal power > 25% RTP

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11
Q

LCO 3.2.4 “Axial Shape Index” requirement

A

The ASI shall be within limits specified in the COLR

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12
Q

LCO 3.2.4 “Axial Shape Index” applicability

A

Mode 1 with thermal power > 25% RTP

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13
Q

LCO 3.3.1 “Reactor Protective System Instrumentation” requirement

A

4 RPS trip units, associated instrument channels, and associated ZPM bypass removal channels shall be operable for each RPS trip function

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14
Q

LCO 3.3.1 “Reactor Protective System Instrumentation” applicability

A
  • High Startup Rate Trip - Modes 1-2
  • Loss of Load Trip - Mode 1 when thermal power >= 17% RTP
  • All others - Modes 1-2, and Modes 3-5 with more than 1 full-length control rod capable of being withdrawn and PCS boron concentration less than refueling boron concentration
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15
Q

LCO 3.3.1 “Reactor Protective System Instrumentation” allows bypass of which trips, and when?

A
  • High Startup Rate - when wide range power < 1E-4% RTP or > 13% RTP
  • Low PCS Flow, Low S/G A Pressure Trip, Low S/G B Pressure Trip, and TM/LP Trip - when wide range power < 1E-4% RTP. Bypass shall be automatically removed when wide range power is >= 1E-4% RTP
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16
Q

LCO 3.3.1 “Reactor Protective System Instrumentation” required action if 1 or more ZPM bypass removal channels inoperable

A

IMMEDIATELY remove the affected ZPM bypasses or declare the affected trip units inoperable

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17
Q

LCO 3.3.1 “Reactor Protective System Instrumentation” required action if 1 or more functions with 2 RPS trip units or associated instrument channels inoperable

A
  • WITHIN 1 HOUR place 1 trip unit in trip

- Not applicable to ZPM bypass removal function

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18
Q

LCO 3.3.7 “PAM Instrumentation” requirement

A

The PAM instrumentation for wide range flux and CETs (all 4 quadrants) shall be operable

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19
Q

LCO 3.3.7 “PAM Instrumentation” applicability

A

Modes 1-3

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20
Q

LCO 3.3.8 “Alternate Shutdown System” requirement

A

The alternate shutdown system function for 1 source range channel on C-150 shall be operable

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21
Q

LCO 3.3.8 “Alternate Shutdown System” applicability

A

Modes 1-3

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22
Q

LCO 3.3.9 “Neutron Flux Monitoring Channels” requirement

A

2 channels of neutron flux monitoring instrumentation shall be operable

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23
Q

LCO 3.3.9 “Neutron Flux Monitoring Channels” applicability

A

Modes 3-5

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24
Q

LCO 3.3.9 “Neutron Flux Monitoring Channels” required action if 1 or more required channel(s) inoperable

A

IMMEDIATELY suspend all operations involving positive reactivity additions

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25
Q

LCO 3.9.2 “Nuclear Instrumentation” requirement

A

2 source range channels shall be operable

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26
Q

LCO 3.9.2 “Nuclear Instrumentation” applicability

A

Mode 6

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27
Q

LCO 3.9.2 “Nuclear Instrumentation” required action if 1 source range channel inoperable

A

IMMEDIATELY suspend core alterations and suspend positive reactivity additions

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28
Q

LCO 3.9.2 “Nuclear Instrumentation” required action if 2 source range channels inoperable

A

IMMEDIATELY initiate action to restore 1 source range channel to operable status

29
Q

How many excore NIs do we have, and what are there functions?

A

2 source range, 2 wide range, and 4 power range NIs to monitor neutron flux from the source range through 125% power

30
Q

What is the purpose of the excore NIs channel range overlap?

A

To ensure flux is continually monitored

31
Q

What are the excore NIs signals used for?

A

Used to process a reactor trip on SUR, VHPT, and TM/LP

32
Q

How do the source range NIs function?

A
  • Dual fission chamber detectors

- Output pulses are amplified, discriminated, and summed, then sent to the control room, C-150A, and containment

33
Q

Which NIs go to C-150A through an optical isolator?

A

NI-1/3, SR/WR detector

34
Q

What range is covered by the source range detectors?

A

6 decades from 0.1 to 10^5 CPS

35
Q

What range is covered by the wide range detectors?

A

10^-8 to 200% power

36
Q

When source range detectors read 3 CPS, what will the wide range detectors read?

A

10^-7

37
Q

What are the power supplies for the source range/wide range NIs?

A

NI-1/3A - Y-30

NI-2/4A - Y-40

38
Q

How does pulse discrimination work?

A

Neutron pulses are bigger than gammas, so the threshold voltage (bias) is set to pass only neutron pulses.

39
Q

What is the function of campelling mode for the wide range detectors?

A

Between 0.05% and 0.1% power, wide range swaps from pulse mode to campbelling mode, which swaps from counting pulses to measuring current flow. When this swap occurs, SR/WR will indicate a step change of approximately 0.04% power.

40
Q

What are the power supplies for the power range detectors?

A

NI-5/6/7/8 from Y-10/20/30/40 respectively

41
Q

How are the power range detectors used in the rod drop alarm circuitry?

A

A summer sums the output of the upper and lower amplifiers and sends an output to the rod drop detection circuit. Upon detection of an 8% power drop in < 8 seconds, a relay activates a rod drop alarm

42
Q

What is the function of the incore NIs?

A
  • provide measured data that may be used in evaluating the neutron flux distribution in the core
  • thermocouples at the top of each incore provide input the the PPC (CET)
43
Q

Why aren’t incores used for control or safety function?

A
  • self-powered rhodium detectors
  • rhodium has a long half-life (41.8 seconds), so the effects of a step change in reactivity won’t be fully seen by the incores for 3-5 minutes
44
Q

What is cold leg temperature shadowing?

A

As water surrounding the core lowers in temperature, it becomes more dense, which reflects more neutrons back into the core. This causes excores to read lower than actual power. Typically 0.5% power per degree F

45
Q

How do we compensate for cold leg temperature shadowing?

A

Periodic calibration of the excores to match calorimetric power (heat balance)

46
Q

What is control rod shadowing?

A

Excores only see neutron leakage from the core periphery. Anything that causes peripheral fuel assemblies to indicate a power level not representative of core average power will cause erroneous power level to be seen by the excores.

47
Q

How do we compensate for control rod shadowing?

A

We operate with all rods full out at full power, and we periodically calibrate the excores to match calorimetric power

48
Q

How does fuel burnout affect indicated power?

A

Fuel burnout causes flux to shift towards the outside of the core over core life. This causes power to indicate higher than actual if not adjusted for.

49
Q

How do boron concentration changes affect NIs?

A

Boron concentration changes can result in rod movement, which changes axial neutron flux, ASI, local power densities, LHR, and cause xenon oscillations.

50
Q

How do reactor poisons affect NIs?

A

Reactor poisons can shift core power, and thus neutron flux density, both axially and radially

51
Q

What does the “High Voltage” light indicate on the power range drawers?

A

When lit, indicates a loss of high voltage (675 VDC) to the detector

52
Q

What does the “15% Bypass” light indicate on the power range drawers?

A

When lit, indicates “Loss of Load” trip is bypassed for this channel (automatically bypassed < 15% power, and automatically removed > 15% power and rising).

53
Q

What does the “Rod Drop” light indicate on the power range drawers?

A

When lit, indicates rod drop bistable has tripped, due to a sudden drop in power (>= 8% in <= 8 seconds)

54
Q

What does the “Channel Deviation Level 1 (5%)” light indicated on the power range drawers?

A

When lit, indicates a 5% deviation between this channel’s power and the 4 channel’s average power.

55
Q

What does the “Channel Deviation Level 1 (10%)” light indicated on the power range drawers?

A

When lit, indicates a 10% deviation between this channel’s power and the 4 channel’s average power.

56
Q

What causes a rod withdraw prohibit?

A
  • VHP Pre-Trip (2/4 13.5% above reset power level)
  • High Power Rate Pre-Trip (1/4 1.5 DPM, between 10^-4% and 15% power)
  • EM OFF
  • Loss of Y-40 above 15% power
57
Q

How do we enable/disable the ZPM Bypass?

A
  • Key switch (1/4 with wide range NI < 10^-4% power)

- Automatically removed above 10^-4% power

58
Q

What trips are removed when in ZPM Bypass?

A
  • Low PCS Flow
  • Low Pressure S/G 1
  • Low Pressure S/G 2
  • TM/LP
59
Q

What is the system interrelationship between NIs and RPS?

A
  • Power range instruments provide inputs for VHPT, TM/LP, disabling “Loss of Load”, and generator coastdown trip
  • Wide range instruments provide input for high rate of change trip, and disabling ZPM bypasses > 10^-4%power
60
Q

What is the system interrelationship between NIs and SPI Node/Host Computer?

A
  • If SPI Node/Host Computer inoperable in Mode 1 > 25% power, then Excores shall be used to monitor LHR
  • If SPI Node/Host Computer inoperable in Mode 1 > 25% power and exocore monitoring isn’t available, then manually reading incores shall be performed to monitor LHR
61
Q

What is the system interrelationship between NIs and Heat Balance Calculation?

A

Heat Balance is used to check and calibrate power range NIs

62
Q

When is a heat balance verification required to be performed?

A

If heat balance differs by more than 2% from any indicated nuclear power or delta T power channel on TMMs

63
Q

When is it required to calibrate the power range NIs?

A

If heat balance differs by more than 1% from any indicated power channel on TMMs digital meters or status screen, or if desired

64
Q

When is it required to calibrate the delta T power indication channels?

A

If heat balance differs by more than 1% from any indicated delta T power channel or TMM primary screen, or if desired

65
Q

How is calibration of delta T power indication channels performed?

A
  • (Heat Balance Power - Delta-T Power) x 0.01 = change in bias.
  • If calculation results in a positive value, then the bias needs to be raised by that much, and vice versa for a negative value.
66
Q

What trips must be bypassed prior to entering new bias terms in the TMM when calibrating Delta-T Power indication?

A
  • VHPT

- TM/LP

67
Q

How do you remove a source range/wide range NI from service?

A
  • Place in bypass 1 affected channel High SUR Trip

- Place in trip any other affected channel High SUR Trip

68
Q

How do you remove a power range NI from service?

A

Place in bypass 1 affected channel, and place in trip any other affected channel of TM/LP, Loss of Load, VHPT, and High Power Rate

Advanced Systems (36 decks)

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