Excore NIs Flashcards
Which Detector is used for Source Range?
Boron Trifluoride (BF3) Proportional Counter
Which Detector is used for Intermediate Range?
Compensated Ion Chamber
Which Detector is used for Power Range?
Uncompensated Ion Chamber
Which Detector is used for Gammametrics? And which region does it operate in?
Fission Chamber (U235)
operates in proportional region
Where is gammametrics SR N-23 powered from?
Opposite Units CRID 3
What is the definition of QPTR?
Ratio of maximum upper (lower) excore detector calibrated output to the average of the upper (lower) detectors
Normalized Current
What do Instrument Power fuses power for excore NIs?
Power Instrument Power Supplies and Bistables
What do Control Power fuses power for excore NIs?
Powers the Bistables
If you are coming down in power and you are undercompensated on an Intermediate Range NI, what can happen?
- P-6 may not auto clear to re-energize SR (IR 6e-11 (2/2)).
- Will have to Unblock SR manually
How will the Instrument Power fuses output signal fail if the fuse is removed?
Output signal fails high
Given the following plant conditions:
* A Unit 1 startup is in progress
* The reactor is critical in the source range
* N41 Power Range channel is removed from service (all bistables placed in the trip condition) for surveillance testing
* A loss of power to the CRID 2 bus occurs
Which of the following actions will occur?
a. Reactor trips and BOTH source range channels are de-energized
b. The reactor is critical and BOTH source range channels are de-energized.
c. Reactor trips and N32 Source Range channel is de-energized. N31 Source Range channel is still in operation.
d. The reactor is critical and N32 Source Range channel is de-energized. N31 Source Range channel is still in operation.
a. Reactor trips and BOTH source range channels are de-energized
On a BF3 Source Range Detector, how are the gamma pulses sorted out from Neutron pulses?
Uses Pulse Height Discriminator
On a Compensated Ion Chamber IR Detector, how do Neutrons create pulses?
Boron gives neutron interactions in outer can.
On a Compensated Ion Chamber IR Detector, how are the gamma pulses sorted out from Neutron pulses?
The boron lined chamber is sensitive to neutron and gamma radiation, while the unlined chamber is sensitive to gamma only.
Net Pulse = Outside – Inside
On a Uncompensated Ion Chamber PR Detector, how are the gamma pulses sorted out from Neutron pulses?
Neutron to Gamma ratio is 1000:1 and are proportionally the same throughout the power range
Why are gammametrics used?
Used for post accident indication of power
What range of indications do gammametrics provide?
Source Range and Wide Range power indications
Where are Intermediate Range NIs (NI-35/36) powered from?
- IR N-35 CRID 1
- IR N-36 CRID 2
How does compensated voltages affect Power Range NIs?
Negligible
Unit 1 is conducting a reactor startup following a refueling outage.
The following conditions exist:
- Source Range Instrument N-31 indicates 2.1e4 cps.
- Source Range Instrument N-32 indicates 2.0e4 cps.
- IR Instrument N-35 indicates 2.5e-11 amps.
- IR Instrument N-36 indicates 1.0e-9 amps.
- Rods are in manual with no rod motion.
- Source Range and Intermediate Range Nuclear Instruments are slowly rising.
Which ONE of the following best explains the indications?
A. N-35 compensating voltage is set too high
B. N-35 compensating voltage is set too low
C. N-36 compensating voltage is set too high
D. N-36 compensating voltage is set too low
A. N-35 compensating voltage is set too high
What is powered by the Opposite Units CRID III?
- SR NI N-23
- Flux Panel log power
- SUR Meter
- LSI-4 Neutron Flux Meter
- NI Panel SR Neutron Flux Meter
What happens if the Audible count rate is lost? What should you do?
Isolate any dilution flowpath to the RCS immediately
- Prompt and definite indication of a boron dilution event is lost
- The boron dilution event may not be detected quickly enough to stop the dilution prior to the loss of SDM
What are the other power indications that NIs can be compared to?
- Thermal power
- RCS ΔT
- MPC-253
What cools the Excore NI detectors?
CRDM Fans
What happens if a control power fuse blows or is removed for the SR/IR NIs?
Always causes a trip to SSPS unless blocked for SR and IR NIs
What happens if an instrument power fuse blows or is removed for the SR/IR NIs?
Always causes a trip to SSPS unless bypassed OR blocked for SR and IR NIs
Would having an undercompensated IR NI have more of an effect going up in power or coming down in power?
Coming down in power
Would having an overcompensated IR NI have more of an effect going up in power or coming down in power?
Going up in power
What would be the effect if an IR NI was overcompensated?
Can cause IR current to decrease below P6 setpoint earlier than normal and cause SR detectors to energize at higher than normal flux level. Going up, P-6 bistable may become active later than it should.
How does an overcompensated IR NI indicate?
Gives false LOW indication
How does an undercompensated IR NI indicate?
Gives false HIGH indication
What must be done per TS 3.2.3 (AFD) if you are not within the target band for AFD above 90% Power? And, what if it’s not met?
NOT in target band and not within upper limit when above 90%, then restore within 15minutes.
IF ACTION/COMPLETION not met, then restore to within upper limit within 15 mins (you may need to be below upper limit of 90%) to get out of it.
What must be done per TS 3.2.3 (AFD) if Thermal Power is less than the upper limit specified in the COLR (90%) and ≥ 50% RTP with AFD not within the acceptable operation limits?
Reduce THERMAL POWER to < 50% RTP within 30 minutes
Per TS 3.9.2 (Nuclear Instrumentation), What is required to be operable?
2 SR Operable
(any combo of GM or SR)
with 1 Operable AUDIO that can be heard in the control room
When can Source Range NIs be blocked? What is the equivalent read out between the IR and SR NIs at the time of this blocking?
IRs allow blocking SRs at E-10 amps on 1/2 IR NIs. This is equivalent to E+3 SR Counts
(This is below 9E+4 cps SR trip)
At what reading on the SR counts does the Intermediate Range indication come on scale?
approximately E+2 SR Counts
What Intermediate Range amps reading is approximately equivalent to 100% thermal power?
E-3 amps
The Source Range NI High Flux trip is at 90,000 counts. What is the appoximate value of this trip as read on the IR NIs?
E-8 amps
A U2 Rx startup is in progress w source range counts at 2000 cps when the following alarms come in: Ann 210 Drop 7, “IR Detector Volt Failure. Ann 210 Drop 8, IR Compensate Volt Failure.” The Rx operator verifies that IR channel N35 level indicates offscale LOW. Assume no operator Action. Based on these indications, what is the status of the core?
All Rod Bottom Lights Should be Lit
Explain how to turn off the SR High Voltage.
The BLOCK switches on the control board can be used to turn off the SR High Voltage when 1 of 2 IR channels exceed P-6 Setpoint
Rx is critical at 8% power. Ann Panel 210 Drop 8, IR Compensate Volt Failure alarms. The BOP reports that IR N36 is affected instrument. This will result in N36 indicated power to _____. Upon a Rx trip or unit shutdown, this failure will cause both SR channels to _____.
Remain about the same; require a manual reset of P-6
It isn’t noticed until down lower in the IR NIs.
