Analysis of the SCWR Core with Water Rods

1
Analysis of the SCWR Core with Water Rods

• Cliff Davis, Jacopo Buongiorno, INEEL
• Larry Conway, Westinghouse

April 29, 2003 Madison, Wisconsin
2
Introduction

• Steady-state thermal-hydraulic and neutronic
  analyses were performed for a SCWR design with
  water rods
• Thermal-hydraulic analysis concentrated on
  determining the density distribution in the water
  rods
• Thermal-hydraulic calculations were made with
  RELAP5 and neutronic calculations with MCNP4B
• Economic calculations used to evaluate
  acceptability of thermal-hydraulic results

3
The core average density should exceed 500 kg/m3
for acceptable fuel cycle cost

• MCNP4B model

4
Heat transfer significantly affects fluid density
in the water rods

• Core average density
• 409 kg/m3
• 391 kg/m3
• 270 kg/m3

5
Results insensitive to the fraction of flow
diverted to the water rods
6
Water rod fluid density can be increased with
insulation

• Core average density
• 409 kg/m3
• 444 kg/m3
• 510 kg/m3 (Reference)
• 566 kg/m3
• 605 kg/m3

7
Water Rod Reactor Internals Feasibility

• Develop preliminary design of down-flow water rod
  RV internals (25x25 sq assembly with 36 water
  rods)
• Current Westinghouse concept uses calandria above
  fuel assemblies to connect upper head region to
  water rods in the fuel assemblies
• Feasibility issues are
• Minimum leakage calandria tube to water rod
  connection
• Minimum leakage seal between upper head and Thot
  fluid
• Thermal stresses

8
Conclusions

• Heat transfer across the bare water rods results
  in unacceptably low core average water density
• Core average water density insensitive to the
  fraction of flow diverted to the water rods
• Insulation needed for acceptable fuel cycle cost
  and thermal stability
• RPV internals being developed by Westinghouse