Rx S/U

Question 1

What determines critical count rate?

Answer 1

Initial Count Rate X 5-7 doublings (initial CR X 2⁵ to 2⁷)

Question 2

Basis for 561°F

Answer 2

(1) the moderator temperature coefficient is within its analyzed temperature range,
(2) the trip instrumentation is within its normal operating range,
(3) the pressurizer is capable of being in an OPERABLE status with a steam bubble, and
(4) the reactor vessel is above its minimum RTNDT temperature.

Question 3

What determines critical rod height?

Answer 3

Reactivity balance such that it is the rod height where core total reactivity is 0, based on a constant temperature and equilibrium xenon and samarium and a critical boron concentration that we have established.

Question 4

Reasons for ECC < Critical Rod Height

Answer 4

Something added negative reactivity to the core that we have not accounted for.

Question 5

Why take critical data?

Answer 5

To verify that the reactor is behaving IAW with the predicted physics parameters.

Question 6

Are extended range NI’s required to be operable?

Answer 6

Yes in modes 3,4,5. 2 SR, 2 IR, 3 PR, 2XR

Question 7

What is your biggest concern when performing a RX S/U?

Answer 7

Criticality

Question 8

If S/U commences at 100 cps what would you expect it to be at criticality?

Answer 8

5 - 7 doublings 3200-12800 cps

Question 9

What would CB A rod position read when CB B starts to move out?

Answer 9

137 steps

Question 10

Reactor Trip Requirements

Answer 10

Not critical and < 561F, trip.

Critical and < 561F, 15 minutes to recover, if not, trip.

Question 11

IF both Source Range Channel count rates rise unexpectedly by a factor of two (doubles) or more during Reactor Startup, THEN ….

Answer 11

immediately INSERT all Control Rods fully into the core AND NOTIFY Reactor Engineering to evaluate the unexpected rise in counts.

Question 12

Let’s say you add enough reactivity to double counts, what would be the status of the reactor if you added the same amount of reactivity you added to double counts?

Answer 12

You would be slightly supercritical. CR1/1-keff2 = CR2/1-keff1

Question 13

What are the DRPI accuracy requirements?

Answer 13

±12 steps

Question 14

During the evaluations, do you expect everyone to call criticality at the same rod height?

Answer 14

No, because core reactivity could be different due to boron and temperature, changing CRH.

Question 15

When would we have rod withdrawal limits?

Answer 15

If the MTC had the possibility to be positive.

Question 16

Assume an initial count rate of 200 CPS. When do you expect the reactor to be critical?

Answer 16

6400 – 25600 cps

Question 17

What do you do if two control rods fall into the core?

Answer 17

Trip the reactor

Question 18

What do you do if the RX was predicted to go critical < C at 65 steps?

Answer 18

IF ICRR data from three consecutive rod withdrawals predict criticality below Rod Insertion Limit of 65 steps on Bank C, Immediately manually INSERT all Control Banks into core, AND NOTIFY Reactor Engineering to evaluate the unexpected situation, AND NOTIFY Unit Operations Manager.

Question 19

What power level would you be at if a S/G Safety fails open?

Answer 19

6% - the entire bank of safeties (20 valves) is rated for 120% steam flow. 120% / 20 = 6% per safety valve

Question 20

What power level would you be at if a Steam Dump fails open?

Answer 20

5.5% per Steam Dump

Question 21

What power level would you be at if a S/G PORV fails open?

Answer 21

6.3% per PORV

Question 22

What are the minimum NIS requirements for a reactor startup?

Answer 22

2 SR, 2 IR, 3 PR

Question 23

How do you determine when the reactor is critical?

Answer 23

Constant positive startup rate with no rod motion

Question 24

When is criticality anticipated?

Answer 24

Criticality SHALL be anticipated at any time during AND after positive reactivity is added to reactor using control rod movement, temperature changes, or boron dilution.

Question 25

What are the NIS overlap requirements?

Answer 25

One half decade SR to IR and IR to PR

Question 26

What will your actions be if the reactor is predicted to go critical before the minimum rod height is reached (>500 pcm below ECP)?

Answer 26

IF ICRR data from previous rod withdrawals consistently AND unexpectedly predicts criticality at a Control Bank position outside ECP - 500 pcm band AND above the Minimum Insertion limit of 65 steps on Control Bank C, THEN PERFORM the following:

STOP the Reactor Startup.

NOTIFY Unit Operations Manager.

Reactor Engineering and the Shift Manager SHALL evaluate and DETERMINE the cause of exceeding the -500 pcm position.

IF cause can NOT be determined within one hour, THEN manually INSERT all Control Banks into the core.

WHEN cause is determined AND resolved, THEN Reactor Startup may recommence.

Question 27

What will your actions be if the reactor is not critical when the ECP is reached?

Answer 27

Continue to criticality until the reactor is critical or the +500 pcm limit is reached.

Question 28

What will your actions be if the maximum rod height is reached (>500 pcm above ECP)?

Answer 28

IF ICRR data from previous rod withdrawals consistently AND unexpectedly predicts criticality at a Control Bank position outside ECP +500 pcm band OR All Rods Out condition WITHOUT attaining criticality as determined by the STA or Reactor Engineer, THEN PERFORM the following:

STOP the Reactor Startup.

NOTIFY Unit Operations Manager.

Reactor Engineering and the Shift Manager SHALL evaluate and DETERMINE the cause of exceeding the +500 pcm position.

IF cause can NOT be determined within one hour, THEN manually INSERT all Control Banks into the core.

WHEN cause is determined AND resolved, THEN Reactor Startup may recommence.

Question 29

Explain the basis for maximum and minimum rod heights.

Answer 29

Minimum rod height – (Group C at 65 steps) – Shutdown Margin Maximum rod height – positive MTC

Question 30

Why is the reactor leveled at 10-8 amps?

Answer 30

To record Critical Data. Date, Time, Unit, Rod Position, RCS Tave, RCS Boron

Question 31

How can you identify the POAH?

Answer 31

Lowering startup rate, rising temperature, rising pressurizer level,

Question 32

What if a Source Range Channel Fails during startup?

Answer 32

Applicable in Mode 2 below P-6 

With the number of OPERABLE channels one less than the Minimum Channels OPERABLE requirement, suspend all operations involving positive reactivity changes. Limited plant cooldown or boron dilution is allowed provided the change is accounted for in the calculated SHUTDOWN MARGIN.

Question 33

What if an Intermediate Range channel fails during startup?

Answer 33

Below the P-6 (Intermediate Range Neutron Flux Interlock) Setpoint:

restore the inoperable channel to OPERABLE status prior to increasing THERMAL POWER above the P-6 Setpoint.

Above the P-6 (Intermediate Range Neutron Flux Interlock) Setpoint but below 10% of RATED THERMAL POWER:

restore the inoperable channel to OPERABLE status prior to increasing THERMAL POWER above 10% of RATED THERMAL POWER.