Rx Start-Up Knowledge Flashcards
State the SDM requirements for the applicable Modes of Operation
> /= 1.3% delta K/K w Tavg > 200*F
> /= 1.0% detail K/K w Tavg = 200*F
What is the minimum temperature for criticality? And Why?
TS 3.4.2 Basis
> /= 541*F
- MTC in analyzed Range
- Protective instrument in normal operable range
- PZR is capable of being in an operable status w steam bubble
- Vessel > RTNDT
When will you transition from Mode 3 –> 2?
Just prior to control bank withdrawal (Admin)
When will you transition from Mode 2 –> 1?
> 5% NI’s (per TS)
Why do we perform an ICRR Plot?
- Backup to calculated ECP to ensure reactor is not brought critical with the control rods below the 0 power rod insertion limit.
- To provide the operator with another mechanism for evaluating / predicting the point at which criticality can be expected.
What parameters are being plotted while performing the ICRR Plot?
Control Bank Rod position vs. ICRR which is equal to initial counter rate over final count rate
What can effect the ECP?
- Changes in RCS Boron Concentration
- Changes in RCS T-avg
- Delay in Startup Xenon Effects
- Delay in Startup ECP validity
If Xenon is present, and a large delay occurs, what must be done?
A new calc must be made
What is Condition I and what must be done if you exceed the limits?
Critical below the Control Rod Lo-Lo Insertion Limit
- Emergency Borate
- Perform SDM
- Trip the Reactor and check rod bottom lights lit
What is condition II and what must be done if the limits are exceeded?
Critical at 1000 pcm below ECP / DIT provided value.
- Trip the reactor and check rod bottom lights lit
What is condition III and what must be done if the limits are exceeded?
Rod withdrawal to 500 pcm past ECP / Dit provided value
- Trip the reactor and check rod bottom lights lit
What does it mean when there is a doubling of counts?
The distance from the initial Keff to Keff = 1 is halved
What is the definition of SDM?
The amount of reactivity by which the reactor is sub critical
A doubling also means….
You added half the reactivity necessary to achieve criticality to the core.
How many doubling are expected before reaching criticality?
5-7 doubling
What does the High flux at shutdown alarm do?
Warns of reactivity increases when shutdown.
Sounds the containment Evacuation alarm.
What is the set point for the high flux at shutdown alarm?
1/2 decade above shutdown count rate.
What is subcritical multiplication?
The effect caused by the combination of a neutron source and a SUBCRITICAL reactor that produces a steady state neutron population greater than the population of source neutrons alone.
How long is the average neutron generation time?
About 0.1 seconds
As Keff gets closer to 1, the number of generations….
Increase significantly
When can criticality be expected?
** At any time
Approx 5-7 doublings
How can you determine if the reactor is critical?
Reactor is actually slightly super critical.
Indicated by a + SUR and a steadily increasing count rate with no rod movement.
When can you block the SR high flux trip?
At P-6
What is the set point for P-6?
1/2 IRS > 10 -10 amps
What is the SR high flux trip?
90,000 Counts
What should be verified before blocking P-6?
Nominal 1 decade of overlap between IR and SR
How many switches are required for blockingg SR trips?
Both
How many switched are required to unblock SR trips?
1
Why do we choose 10E-8 amps to collect critical data?
- Well above SR, so source neutron effects are negligible
2. Below POAH. Doppler and Moderator Temperature effects are not present.
What is the POAH?
Point where thermal output of the core exactly equals system losses.
What are the primary and secondary indications that the POAH has been reached?
- Lowering SUR
- T-avg Rising
- PZR Pressure and Level Rising
- SG Pressure and Level Rising
- Raise in steam dump demand
What happens to het MTC as T-avg increases?
MTC adds negative reactivity
What happens to het Doppler coefficient as power increases?
Ads negative reactivity
What happens to MTC as core ages?
It becomes more negative
With a more negative MTC, the same change in temperature will cause a ______
Larger reactivity insertion so effect on POAH indication is more rapid.
Why is the next power hold point at 4%?
The MDAFPs have a capacity of 450 gpm each, which is good for ~4% power
Why is the Reactor safer at 2% power than at 10E-8 amps?
above the POAH, the reactor is inherently stable and closer to Rd protection set points
What does 2% power correspond to on the IR?
~ 4E-6
When is P-10 made up?
2/4 PR NIs are > 10% power
What doe P-10 do?
Backup de-energization of SR
Allows ability to block the IR and PR low power high flux trips and the IR rod stop
Provides input into P-7, along w P-13
When is P-10 auto unblocked?
3/4 PR less than 10% power
What are the bases for rod insertion limits?
- Ensure acceptable power distribution limits are maintained
- SDM is maintained
- Limit potential effects of rod misalignment on associated accident analysis
How does the operator ensure hot channel factors are maintained during power ops?
By checking (within limits):
- AFD
- QPTR
- RIL
