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Ops > T&AA and MCD > Flashcards

T&AA and MCD Flashcards

1
Q

Intro TAA & MCD

What is Transient and Accident Analysis based upon?

What is Mitigating Core Damage based upon?

A

analyzed events in FSAR Ch. 15 (accident analysis)

unlikley but possible core-damaging events analyzed in WCAP documents (westinghouse comercial atomic power)

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2
Q

MCD, inst

What is transmission ratio?

How does transmission ratio explain what happens to source counts when voiding occurs in core?

A

the ratio of nuetrons detected vs. nuetrons produced in core

As voiding rises in core (void fraction) the source counts rise. Even though to total amount of neutrons produced is lowering the ratio of nuetrons detected goes up and overpowers the lower total neutrons produced.

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3
Q

MCD, inst.

What is the highest the SR counts should reach during coolant voiding?

core uncovery?

should count ever go into IR?

A

voiding - 40 x normal

uncovery - 100 x normal

counts should never go into IR

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4
Q

MCD, inst.

Describe mechanism by which abnormal CNMT atmosphere (high temp) will cause level instrumentation to read abnormal?

A
  • hi temp heats wet reference leg
  • wet reference leg density goes down (expands)
  • ref leg spills over
  • d/p between ref leg and var leg goes down
  • level indicates higher than actual
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5
Q

MCD, cooling

What are the mitigation actions/ strategys for inadequate core cooling (in order of preference)?

A
  1. restore ECCS (HPSI, re-cover core, restore inventory)
  2. secondary depressurization (cools RCS, depress RCS, establish low head injection)
  3. RCP reactivation (need cooling, trash RCPs, get two phase cooling)
  4. RCS depressurization (make loca bigger, lose inventory, drop press, establish low head injection)
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6
Q

MCD, cooling

What are the stages of LOCA?

A

Blowdown break -> Prcs = Pcnmt

Refill b/d -> Lcore = bottom of fuel (accum done inj)

Reflood refill -> eccs covers core, temp rise stops

long term cooling cold leg/ hot leg recirc

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7
Q

MCD, cooling

What are the major differences for indications for:

steam space LOCA?

vs.

liquid space LOCA?

A

steam space - inventory maintain, Press lowering

liquid space - press maintained, level lowering

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8
Q

TAA intro

What is the relationship between Frequency and Severity when regarding risk?

What must be done, post trip, within 30 min to prevent core damage?

A

if frequency of event goes up severity of event goes down

if frequency of event goes down, severity goes up

remove decay heat

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9
Q

TAA intro

Describe the following, include frequency & severity of event.

Condition I

Condition II

Condition III

Condition IV

A

I - normal ops

II - moderate frequency (once per cycle)

III - once per lifetime of plant

IV - never

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10
Q

TAA intro

What is the major determination that a LBIE (licensing basis impact evaluation) is making?

What are the 3 sections of a LBIE

A

if NRC approval is required prior to making proposed change.

  • Applicability determination
  • 50.59 screen
  • 50.59 evaluation
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11
Q

MCD core damage

What indications are used to asses core damage in EP RB-14?

What are the restrictions for each?

A
  • Ltdn Hx rad monitor
  • MSL rad monitors (RM-71-74)
  • Cnmt Hi range rad monitors (RM-30 & 31)
  • ltdn must be in service
  • tube rupture, 5 min wait for MSL, allow N-16 decay away
  • LOCA
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12
Q

MCD core damage

Briefly describe the following concerning fuel condition, include temperature ranges:

Undamaged

Clad failure

fuel overheat

Core melt

A

undamaged - ……duh (< 1300 deg F)

clad failure - clad break, radionuclieds in “gap” escape into RCS, includes nobel gases, Kr, Xe, I (1300-2000 deg)

fuel overheat - pellet degrades, nobel gases released and Cesium (2000-3450 deg)

Core melt - pellet dissolves/liquifies, rapid release additional nobel gases and cesium, plus strontium and barium-lanthanum isotopes (> 3450 deg)

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13
Q

MCD rad aspect

Define the following:

Exclusion Area

Low population Zone

A

Exclusion - if person inside for 2 hours they wont exceed 25 rem total dose and 300 rem to thyroid

Low pop - if person located outer boundry for entire plume wont exceed 25 rem total dose and 300 rem to thyroid

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14
Q

MCD rad aspect

what is main difference for material located in….

10CFR20

vs.

10CFR100

A

20 - has legal limits for rad workers and public

100 - has criteria for postulated accidents and resultant exposure to public

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15
Q

TAA SGTR

What are the “Unique Concerns” regarding a SGTR?

A
  • Rad release
    • contaminate secondary
    • if 10% or safety pop => dose public
  • S/G overfill
    • pass water thru 10% or safety => not reseat
    • stm pipe not rated for weight of water
  • H2 accumulation
    • H2 in RCS -> S/G
    • 02 in RWST -> S/G (SI flow)
    • => explosive hazzard
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16
Q

TAA SGTR

What are the major causes of steam generator “Tube Degradation”?

A
  • Impurities
    • FME
    • chemical (Cl-, SO4 -, etc)
  • Flow induced vibrations
    • design
  • Hi D/P
    • faulted S/G
17
Q

TAA SGTR

During a tube rupture, if no operator actions are taken what will most likely cause a Rx trip?

SI?

A

OT delta T (variable setpoint)

Low Ppzr (1950 psig)

Low Ppzr (1850 psig)

18
Q

TAA SGTR

When combating a SGTR concurrent with a loss of offsite power what major actions are changed?

A

No 12 bus =>

  • no CW => no condensor
  • no 40% stm dumps, all cooldown used with 10%’ers

No 12 bus =>

  • no RCP => no spray
  • RCS depresurization done with PORV
19
Q

TAA SGTR

What are the major TCOA’s associated with SGTR?

A
  • Identify and isolate 10 min (from rupture)
  • initiate cooldown 5 min (from isolation)
  • initate depress 4 min (complete c/d)
  • terminate SI 2 min (complete depress)
20
Q

MCD - integrity

What are the four conditions required for PTS?

A
  • Hi press = Hi pressure
  • Lo temp = temp < NDT (less ductile)
  • pre-exist flaw = 1/4 T (0.25 RV thickness)
  • stress = thermal shock
21
Q

MCD - integrity

What are the worst case scenarios for PTS?

A
  • SBLOCA (H L)
  • SGTR w/ operator error (30 min delay sec SI)
22
Q

MCD - integrity

What are the major actions for FR-P.1?

What is only action that credit is taken in Safety Analysis?

A
  • stop C/D
  • terminate SI (if meet conditions)
  • depressurize RCS
  • Soak

SOAK

Ops (27 decks)

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