GRAVITY DRIVEN COOLING IN ISP42 PANDA PHASE B

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GRAVITY DRIVEN COOLING IN ISP-42 (PANDA) PHASE B
IAEAs 2nd Research Coordination Meeting on the
CRP on Natural Circulation Phenomena, Modelling,
and Reliability of Passive Safety Systems that
Utilize Natural Circulation, Oregon State
University, Corvallis, Oregon, USA,
29.08-02.09.2005

• Nusret Aksan

Paul Scherrer Institut (PSI), 5232 Villigen
PSI, Switzerland Tel. [phone], Fax.
41-56-310-4481, E-mail nusret.aksan_at_psi.ch
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OVERVIEW

• OBJECTIVES OF ISP-42 PHASE-B
• PANDA vs ESBWR
• EXPECTED AND OBSERVED PHENOMENA
• HISTORY OF EVENTS
• RESULTS
• REMARKS

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OBJECTIVES OF PHASE-B

• Investigation of the discharge of cold water into
  a saturated Reactor Pressure Vessel (RPV) and to
  observe induced phenomena and the resulting
  system behaviour.

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(No Transcript)
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EXPECTED AND OBSERVED PHENOMENA

• Gravity driven cooling system tank discharge
  which includes
• - Subcooled water injection into the downcomer
  of the RPV
• - Collapse of voids in RPV
• - Wetwell depressurization
• - Excess condensation in the system causes
  drywell pressure to decrease
• Non-condensable gas return from wetwell to
  drywell (due to vacuum breaker openings)
• Resumption of boiling in the RPV
• Passive containment cooler start-up

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Schematic of the Gravity Driven Cooling Test,
ISP-42 Phase B
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HISTORY OF EVENTS (I)

• 0 sec RPV power ON
• - Evaporation started, and at 29 sec, the two
  main steam valves were opened simultaneously
  as were the PCC feed valves to allow start-up of
  the three operational PCCs
• - Steam was injected into the two drywells and
  to the PCC primary sides where condensation
  of the steam started instantaneously

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HISTORY OF EVENTS (II)

• 48 sec GDCS drain line valve opening
• - Large amounts of cold water immediately
  flooded the lower part of the RPV causing
• collapse of voids
• condensation of steam
• suppression of boiling
• increase of of water level inside the RPV
• - For the next 300 to 400sec, the three PCCs
  were operational condensing additional steam
  out of the RPV/drywell gas space until air has
  been accumulated on the primary sides of
  the PCCs, terminating steam condensation
• - Decrease of steam content in the RPV/drywell
  gas space resulted in a decrease of the
  drywell pressure
• - Drywell pressure dropped well below wetwell
  pressure and vacuum breakers opened
  releasing additional air from the wetwell gas
  space into the drywells

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HISTORY OF EVENTS (III)

• 500 to 3000 sec Heat up of the RPV water
• - After all the cold water in the GDCS tank
  injected into the RPV, steam flow in the main
  steam line as well as PCC feed lines came to a
  halt
• - PCC powers are low
• - System pressure remained nearly constant
• Above 3000 sec Resumption of RPV boiling and
  PCC start-up
• - After resumption of boiling in the RPV, main
  steam line flows started again
• - Shortly afterwards, PCCs started condensing
  steam
• - For the short period between beginning of
  main steam line flow and
• start-up of the PCCs, system pressure
  slightly increased and remained constant
  afterward

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System Pressurization
GDCS drain??RPV-heat up??PCC start-up
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Gravity Driven Cooling System Tank Discharge
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Gravity Driven Cooling System Tank Discharge
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Vacuum Breaker Openings-- Pressure difference
between DW-WW
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PCC Performance Int. Mass flow in Feed Line
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PCC Performance Int. Mass Flow in Drain Line
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PCC Performance-- Power
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REMARKS

• The phenomena involved in the Gravity Driven
  Cooling has been
• presented
• As observed this phenomenon is composed of
  sub-phenomena
• Composition of the sub-phenomena depend on the
  type and the
• system of the nuclear plant design