Summary of Research Project on Horizontal Heat Exchanger for PCCS

1
Summary of Research Project on Horizontal Heat
Exchanger for PCCS

• T. Yonomoto
• Japan Atomic Energy Research Institute
• IAEAs Second 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,
  Aug. 29 - Sep.2, 2005

2
Outline

• Introduction
• Single-tube test
• Bundle test
• Code validation and development
• BWR analysis
• Conclusion

3
PCCS Explored In This Project

• Planned for the use in ABWR-II using conventional
  ECCS
• Prevention of containment failure due to
  pressurization during SAs, practically
  eliminating necessity of containment venting
• No function of safety injection

PCCS heat exchanger
ESBWR
drywell
conden-sate
steamN/C gas
N/C gas
wetwell
Ref. ESBWR design, technology and program plan
overview, A.S. Rao, NRC staff-GE meeting 2002,
Rockville, Maryland
4
Reference Conditions for Design

• To prevent containment failure due to
  pressurization
• Pressure 0.7 MPa gt Design pressure
• Condensation capacity 1 of normal power
• To be functional during SAs with NC gas
  generation (generated by MCCI)
• NC gas quality up to 1

5
Advantages of Horizontal HEX

• Geometry (diameter, pitch, and length) can be
  optimized based solely on the heat transfer
  performance, which enables more compact HEX
• For vertical HEX, the water level in the pool and
  the function as support structure for the inlet
  header pipe affect geometry.
• Can be submerged in the pool with lower liquid
  level, which enables more efficient use of the
  pool water inventory.
• Maintenance and inspection can be much easier
  because the inlet and outlet plenums can be
  placed outside the PCCS pool.

6
Single-Tube Test

• To obtain data for HT models validation and
  development, and design

horizontal length4m
downward
atmosphere
diameter 20, 30, 45
secondary coolant
N2 gas tank
boiler
7
Single-Tube Test Results
Roll waves on liquid film
Validation of existing and developed correlations
Passing freq. vs. Nu
8
Bundle Test

• Halved HEX to represent one of four HEXs in
  ABWR-II

steam to atmosphere
steam
observation
window
condenser tubes
condensate
Front view
Side view
9
Code Validation and Development

• RELAP5/MOD3 Modification
• Developed heat transfer package incorporated
• Input deck developed (Single-tube model )
• RELAP5/ACE-3D Development
• RELAP5 for primary side calculation
• ACE-3D, JAERIs developed 3-D two-phase flow
  analysis code, for secondary side calculation
• Used to assess RELAP5/MOD3 results

10
Validation of RELAP5/ACE-3D using Bundle Test
Results
Void fractions in bundle
Qualities in tubes
11
Example of RELAP5/ACE-3D Cal.

• Void fraction in secondary side

12
BWR Severe Accident Analysis

• Transient without ECCS injection (TQUV)
• RELAP5 used (NC generation rate determined by
  MELCOR)

TQUV Transient with scram ADS actuation and
w/o ECCS injections
13
Conclusions

• A new heat transfer package developed
• consists of newly developed and validated
  existing correlations based on the tests.
• The performance was confirmed by the large-scale
  bundle experiments.
• Combined code RELAP5/ACE-3D was developed and
  validated with the data for detailed analysis,
  which was used to assess the RELAP5 SA
  calculations.
• The effectiveness of the PCCS was confirmed in
  the BWR SA analyses
• The containment is not damaged on a large scale
  by pressurization during SAs for at least one day
  even when all the active safety systems are
  failed.