Systems Exam 3 - Excore Instrumentation

Question 1

SR SHTDN FLUX HI alarm

Answer 1

→annunciates if flux increases to 300 cps or 5x background
→can be blocked
→this alarm also activates containment evacuation alarm

Question 2

SR FLUX DBLG Alarm

Answer 2

→annunciates if SR flux doubles in 9 minutes

Question 3

Source Range Detector

Answer 3

→channels N31 & N32
→BF3 Proportional Detector
→Rx Trip at 10^5 cps (1/2 detectors, can block above P-6)
→Pulse Height Discriminator: Eliminates pulses due to gamma ionization

Note: high voltage switching operations (or lightning) can spike SR detectors, causing trips.

Question 4

Intermediate Range Detector

Answer 4

→channels N35 & N36
→Compensated Ion Chamber (gamma interactions in both chambers are cancelled out by adjusting voltage of gamma only detector (inner can)
→Rx Trip when detector current output = 25% Rx Power (1/2 detectors)
→Overcompensated (high compensation voltage) causes detector output to decrease (read lower than actual)
→Undercompensated (low compensation voltage) causes detector output to increase (read higher than actual)

Note: if one channel is undercompensated, you may not get the unblock of SR trips; can manually unblock SR trips at CB in this case

Question 5

Power Range Detector

Answer 5

→channels N41, N42, N43, & N44
→Uncompensated Ion Chamber
→amount of gammas compared to amount of neutrons is insignificant
→amount of background gammas is directly proportional to power level

Nuclear Engineering has estimated that the effect on PR NIS is approximately 0.8 % per degree at 100% power. The effect is decreased proportionally with power. For example at 50% power, the effect is halved or 0.4% per degree.

Question 6

Tech Spec 3.3.1 & 3.9.3 Source Range:

Answer 6

→Source Range Instrumentation is required in Mode 2 (below P6) through Mode 6
→in Mode 6, only visual count rate indication is required in the Control Room
→in Mode 3-5 the T.S. only applies if the Rod Control System is capable of withdrawal and one or more rods not fully inserted.

Question 7

Tech Spec 3.3.1 Intermediate Range:

Answer 7

The Intermediate Range Instrumentation is required in Mode 1 (below P-10) and Mode 2 (above P-6)

1 IR Channel inoperable, Mode 1 (<P-10) & 2 (>P-6):
→reduce THERMAL POWER to <P-6 in 24 hours, or
→increase power to >P-10 in 24 hours
→Mode 2 (<P-6) - Restore to operable prior to increasing power above the P-6 setpoint

Both IR channels inoperable Mode 1 (<P-10) & 2 (>P-6):
→suspend operations involving positive reactivity additions immediately, and
→reduce power to <P-6 in 2 hours

Question 8

Tech Spec 3.3.1 Power Range:

Answer 8

2 PR Channels Inoperable, enter LCO 3.0.3

Question 9

RX > 50% PWR UP PR DET FLUX DEV HI alarm:

Answer 9

any one detector deviating by > 5% of the average of all upper detectors

Question 10

RX > 50% PWR LWR PR DET FLUX DEV HI alarm:

Answer 10

any one detector deviating by > 5% of the average of all lower detectors

Question 11

Power Range Deviation alarm:

Answer 11

deviating by >5% of the average of all detectors

Question 12

From 100% power, approximately how long after a trip do we take to come down to where Source Range instruments are energized?

Answer 12

→approx. 15-18 minutes
→10^-10 cps
→Startup Rate = -1/3 dpm
→approx. 6 decades

Question 13

Where are the overlaps between SR, IR, and PR instruments?

Answer 13

→0% power on PR ≈ 10^-5 amps on IR
→4 x 10^4 cps on SR ≈ 10^-10 amps on IR

Question 14

Tech Spec 3.2.4 Quadrant Power Tilt Ratio (QPTR)

Answer 14

→action required once ≥1.02
→applicable in Mode 1, >50%
→For each 1% QPTR above 1.00, reduce power 3% (pay attention to power level)
→verify QPTR every 12 hrs
→perform evaluation to allow continued operation
→if completion time not met, reduce power to <50%

Note: this one is tricky. Action isn’t required until 1.02, but you must take the action based on the amount above 1.00

Question 15

Tech Spec 3.2.3 Axial Flux Difference (AFD)

Answer 15

→applicable in Mode 1 >50%
→Spec not met when two or more PR NIs indicate out of spec
→30 minutes to be <50% - no time for correction

Background Info:
→AFD = ΔI
→inside the doghouse = acceptable; outside the doghouse = unacceptable

“Half power, half hour”

Note: if AFD is high on one channel, then lower detector failed; if it’s low on one channel, upper detector failed

Question 16

Source Range and Level Trip Bypass Switch

Answer 16

Note: losing power has the same effect as pulling fuses.

Question 17

Intermediate Range and Level Trip Bypass Switch

Answer 17

Note: losing power has the same effect as pulling fuses.

Question 18

Gammametrics

Answer 18

→2 ranges: Low range (0.1 cps to 10^5 cps) and Wide range (10^-8 to 200% power)
→fission chamber detector
→designed to operate under accident conditions; PAM equipment
→indicates on MCB and RSP

Question 19

The Power Range Summing and Level Amp is used for:

Answer 19

→Gain Pot for Calorimetric Adjustment
→adds upper and lower detectors together before sending values out to be used by different logics