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TAA-MCD Flashcards

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1
Q

Define undermoderated

A

MTC is negative

resonance escape probability is dominate over thermal utilization factor

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2
Q

Define overmoderated

A

MTC is positive

Thermal utilization factor is dominate over resonance escape probability

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3
Q

Describe core power effects of FTC

A

At higher fuel temps doppler broadening lessens per degree F

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4
Q

Why does FTC become more negative over core life

A

build in of Pu-240

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5
Q

State ECCS acceptance criteria

A 
Cladding temp <2200F
Cladding oxidation <17% of thickness
Hydrogen generation <1%
Coolable geometry
Long-term cooling
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6
Q

what is Critical Heat flux

A

the heat transfer per unit area to cause DNB

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7
Q

discuss how CHF change over core height

A

CHF decreases from the bottom to the top of the core

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8
Q

Define departure from nucleate boiling ratio

A

CHF divided by AHF at any point along a fuel rod

T.S. limit >/= 1.14

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9
Q

Discuss what the concern is with RCS hot leg becoming saturated

A

Delta-T is no longer representative of reactor power output

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10
Q

State the basis for heat flux hot channel factor

A

Fuel temp <4700F
Maintain cladding temp <2200F
Maintain DNBR >/=1.14

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11
Q

Define FqZ (Heat flux Hot Channel Factor)

A

the ratio of highest linear power density at core height Z along any fuel rod to the core average fuel rod linear power density

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12
Q

State the Kw/ft that would cause fuel melt and cladding ocidation

A

21 Kw/Ft = 4700F (fuel melt)

18 Kw/Ft = 2200F (cladding Oxidation)

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13
Q

Define FnDelta-H (Nuclear Enthalpy rise Hot Channel Factor)

A

Ratio of the total power produced by the highest power fuel rod to the total power produced by the average fuel rod power

  • is a measure of a maximum total power produced in a fuel rod
  • basis: DNBR
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14
Q

Define Axial Flux DIfference

A

AFD = Ptop - Pbottom

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15
Q

Define Axial Offset

A

Ptop-Pbottom/Ptop+Pbottom

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16
Q

State the T.S. for AFD

A

If unacceptable:
restore to within limits within 15 min
OR
restore power to <50% within 30 min

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17
Q

Summarize guidance for AFD control

A 
Inside admin band: do NOTHING
Outside band (ARO): push-pull-drift
Outside band: push-pull
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18
Q

State acceptance criteria for rod control

A

+/- 10% load change
+/- 5% per minute load ramp rate
50% step load rejection with auto steam dumps

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19
Q

State the function of the Setpoint Study

A

A setpoint study which defines NSSS control system setpoints and time constants to be used for initial plant start up and subsequent operation as verified by startup testing

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20
Q

State Reactor response to a SLOW reactivity addition accident

A

No power overshoot before RPS trip

Core protected by OTDT trip

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21
Q

State Reactor response to a FAST reactivity addition accident

A

power overshoots before rods insert
Core protected by FTC
- High Flux/ high rate trips

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22
Q

State Reactor response to a PROMPT reactivity addition accident

A

Large power overshoot
FTC limits power rise
RX eventually trips from PR flux trip

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23
Q

State why single rod withdrawal is worse than a bank withdrawal

A

A single rod withdrawal causes significant localized hot channel factor peeking

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24
Q

State RCS response to a Rod drop accident with rods in manual

A

Tave decreases adding negative reactivity

Decrease is not enough to restore power to original level

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25
State plant response to a Rod drop accident with rods in AUTO
Rods withdraw due to PMM (if no C-11) | slight power overshoot causing rods to drive back in
26
Describe the analyzed rod ejection accident
LOCA and reactivity addition accident FTC required to terminate power rise RX trip on high flux rate BOL full power would result in 10% fuel melt
27
During an increased Secondary Heat removal accident why is BOL with auto rods is most limiting
Less negative MTC Temp and pressure are more stable power is higher and dominant so DNBR decreases
28
State design features that minimize the consequences of steam line breaks
``` Flow restrictor in outlet of SG nozzle MSI actuation SI actuation ASME class 1 piping Various RX trips ```
29
State most limiting factor in MSLB accident
Most reactive RCCA is assumed to be stuck fully withdrawn after reactor trip - allows possible re-criticality - results in higher peaking factors
30
Explain why HZP and EOL for MSLB is severe
HZP: maximum SG water inventory EOL: MTC is most negative
31
State DNB parameters of concern
Tave = 595.1F PZR press >/= 2185# - restore within 2hrs
32
For a Decreased Secondary heat load removal accident state why a low-low SG water level with a LOP is severe
Minimizes the SG heat transfer capability and increase the amount of RCS stored energy at the time of RX trip
33
State how RCS Bleed and Feed is accomplished
Used during loss of all feed event (loss of heat sink) | - Both PORVs and one CCP + SI
34
Explain why it is important that the initiation of bleed and feed be delayed criteria is met
``` WR level in and 3 SG < 30% PZR pressure > 2385# - SG mass still available for cooling - Cooling helps repressurization - lower RCS pressure allows more ECCS flow ```
35
List stages for Large Break LOCA
Blowdown Refill Reflood Recirculation
36
Discuss SBLOCA worse case and location
Cold leg 4" SBLOCA is the worse case due to loop seal and that steam is prevented from being vented from the core
37
State the UFSAR worse case LBLOCA
Loss of one train of ECCS | Both trains of CBS work
38
Explain why for SBLOCAs the core can become uncovered
A loop seal forms in the intermediate leg which slowly depletes inventory and causes core uncovery - once level is low enough the loop seal is broken and reflood can commence
39
Describe how to determine a SGTR from a LOCA
an uncontrolled SG NR level increase
40
Describe major actions in E-3 that are required to recover from a SGTR
Identify and Isolate the ruptured SG Cooldown RCS Depressurize RCS Terminate SI
41
Explain my stopping an RCP is not desirable during a SGTR
CDR for natural circ is slower | normal sprays are not available for depressurization
42
For a SGTR state the UFSAR major assumptions
1 intact ASDV fails to open Ruptured SG ASDV fails open LOP Normal plant parameters
43
For a SGTR state the consequences for not meeting the TCAs
Water may relieve out of the SG safeties, radiological mess
44
For loss of flow accidents that the core safety limit of concern
DNBR >/= 1.14
45
Explain RCP under voltage trip reasoning
this is an anticipatory trip that senses flow maybe too low
46
Explain RCP under frequency trip reasoning
The RCP flywheel won't have enough inertia for adequate coast down
47
State relationship between loss of flow and OTDT trips
OTDT is a DNB trip | OTDT assumes nominal flow
48
Explain why a seized RCP rotor is the most severe low flow accident
There is no flywheel coast down | significant DNB occurs
49
State the most significant post-LOCA H2 contributor
zirc water reaction
50
State why transfer to hot leg recirc is desired
Prevents boron precipitation | condenses any steam in the outlet plenum
51
List the 5 indications of natural circulation
``` Subcooling >40f Hot leg temps - stable or decreasing Core exit thermocouples - stable or decreasing SG pressures - stable or decreasing Cold leg temps - at Tsat for SG pressure ```
52
Discuss why Delta-T can not be relied upon in natural circulation
Delta-T is only valid for forced flow
53
State limits on subcooling if natural circ is being used
this allows vessel head to cooldown - >50F with 2 CRDMs running - 100 and 130F if CRDMs fans are not funning
54
State how to enhance natural circ
``` PZR level at 25% RCS subcooling at 50f SG NR at 50% CDR at 50F/hr ALL CRDM fans on ```
55
State the two factors that determine the severity of a SBO
Duration of the event | Response of the RCP seals
56
Discuss why the RCP seals are the most susceptible in a SBO
If cooling is lost then seals will degrade >550F | This will cause a LOCA and core uncovery if power is not restored
57
Describe two corrective measures that must be taken to minimize a SBO
Cool down RCS | Depressurize the RCP
58
Describe UFSAR SBO conclusions
4 HR duration 4 HR battery capacity CST required volume: 137,000gallon Core is not expected to become uncovered
59
State worse case ATWS event
Loss of secondary heat sink | - loss of load (2959#) RCS pressure
60
State assumed RX power after ATWS
after 10 min RX power is 5% due to steam demand and EFW capacity
61
Discuss how to limit an ATWS event
Trip the turbine w/in 30 seconds (preserves SG inventory) | Initiate SG flow w/in 60 second
62
List the operator actions to mitigate ATWS event
Insert negative reactivity trip turbine w/in 30 seconds EFW actuation within 60 seconds Verify PORVS and safeties open when required
63
State the temp for inadequate core cooling
CETC >1100F, assumes core damage will happen
64
State conditions for inadequate core cooling
No CCPs or SIPs
65
State in order of preference inadequate core cooling recovery methods
ECCS actuation Secondary Depressurization RCP restart RCS depressurization
66
Explain response of normal response of NI following a reactor trip
Prompt drop to 6% stable -1/3 SUR SR detectors should reenergize at 5e-11 about 15 to 20 min
67
Explain what determines equilibrium fission rate in a shut down RX
Directly proportional to source strength (higher at EOL) | Inversely proportional to SDM
68
Why does SR counts increase as voiding increases with RCPs running
RCS is saturated and progressively voiding Indicated SR level rises as a much larger fraction of the neutron population reaches the NIs (less shielding from coolant)
69
Why does SR counts change as voiding increases without RCPs
SR counts increases as core uncovers and downcomer empties | SR counts then decrease as level drops further and source strength drops
70
Explain the response of incore NI as the core is uncoverd
During uncovery the outputs above the water level rise significantly The outputs below the water level will read lower and show more variation
71
State how to calculate Subcooling margin
Use WR RCS pressure (PT-403,405) Determine Tsat for pressure Subtract highest average CETC quadrant temperature
72
What does a negative subcooling margin mean
Indication of superheat at core exit
73
What does 40F subcooling margin mean
Saturation temperatures at core exit
74
Discuss why CDR is more restrictive
CDR is more restrictive due to the tensile stress on the inner vessel wall causing the vessel to be closer to max allowed stress
75
State the four conditions that must be present for Pressurized thermal shock
Severe cooling and high rate High internal pressure High NDT Critical flaw
76
State the three things as an operator that can be done to reduce PTS
Stop the cooldown Terminate SI Soak the RCS
77
State the Containment design basis for a LBLOCA
LBLOCA in the intermediate leg | Combines effect of high core reflood rate plus SG heat addition
78
State issue with FR-Z.1 versus other FRPs
FR-Z.1 there is no alternate recovery actions can be provided because CBS is the only ESF system that will mitigate a rise in containment pressure
79
State parameters for entry into Containment status tree
pressure >52# OR Pressure >18# and Phase A and B isolations not isolated
80
List the four major classifications on post accident fuel conditions
Undamaged fuel Failed cladding Overheated fuel Core Melt
81
Describe the fission products unique to each type of post accident fuel conditions
Failed cladding - Xenon, Krypton, Iodine Overheated Fuel - Xenon, Krypton, Iodine and CESIUM Core Melt - Strontium and Barium
82
State auxiliary parameters to asses core damage
Containment H2 CETCs RVLIS Containment radiation level
83
Describe how Iodine spiking occurs
Iodine transfuses through a cladding defect into the RCS
84
Describe where Post accident samples can be drawn from
``` Chemistry samples from Loops 1 or 3 OR RHR pump discharge all through the PASS System Radiation on sample can be very high ```
85
State which Radiation monitor is most useful to the plant to determine containment rad levels
Post LOCA Containment area radiation monitors
86
State how to estimate radiation doses in containment
Take external dose rates at the hatch and solve for internal dose
87
Describe how the operator determines the dose to the public
Raddose V is used to calculate
88
State what must be done to use CSF for EAL entry
Conditions must be evaluated and verified via hardwire indications

TAA/MCD (1 decks)

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