1. Vattenfall’s use of FRAPCON for PWR cycle-specific verification
FRAPCON/FRAPTRAN User Group Mtg, Jeju, Korea
10 September 2017
Mattias Hemlin and David Schrire
Vattenfall Nuclear Fuel, SE Stockholm, Sweden
Confidentiality: None (C1)
Vattenfall’s use of FRAPCON | D Schrire |

2. Ringhals PWRs Overview
Reactor type
W 3-loop
Core design
15x15, 12’, 157 FAs
17x17, 12’, 157 FAs
Commercial operation
May 1975
Sept 1981
Nov 1983
MW Th
2652
2775 2992 3135
2775 3292
Exit temp. (loop) °C
321
324 323
321  319 324
Fuel Vendor
(Areva)/Westinghouse
Fuel Type
(previous/current)
AFA-type all-M5
15 Upgrade (Opt Zirlo clad)
HTP-type M5 clad
RFA-2 (Opt Zirlo clad)
Cycle Length
12 month
Chemistry Control
Constant pH (7.4)
Constant pH (7.4)*
SGR
* Lower before SGR
Vattenfall’s use of FRAPCON | D Schrire |

3. Outline Ringhals PWRs - Operating conditions
Cycle specific fuel rod design verification
Westinghouse RFA-2 mid-life case
Westinghouse RFA-2 EOL case
PIE verification scope and results so far
Conclusions
Vattenfall’s use of FRAPCON | D Schrire |

4. Cycle specific fuel rod design verification needs
Verification requirements
Vattenfall needs to confirm that all fuel rod design criteria are fulfilled for every core design (cycle)
Calculations are done for all fuel rods in the core (both with and w/o Gd) for
Rod internal pressure
Maximum centerline temperature
Permanent cladding strain
Oxide thickness (peak)
Cladding hydrogen content (peak)
 Now using FRAPCON for in-house verification
Verification in-house
Previously only performed by fuel vendors
Practical benefits of doing this in-house, e.g.
Short turnaround time (e.g. for quick core redesign due to fuel damage, etc)
Consistent methodology for all fuel types
Independent code/methods  additional robustness
 Vattenfall now started using FRAPCON for in-house verification
Vattenfall’s use of FRAPCON | D Schrire |

5. Cycle specific fuel rod design verification methodology
Core simulation data
The cycle specific input to FRAPCON is based on the 3-D core-follow and prediction calculations with Studsvik’s CMS system (CASMO-5/SIMULATE-3)
Time-dependent reactor conditions for
Linear heat generation rate (LHGR)
Coolant pressure
Coolant inlet temperature (for assembly)
Coolant mass flux
12 axial nodes (LHGR, burnup and fn) at each time step (~10 per cycle)
 Condensed to 3 axial profiles per cycle for FRAPCON (BOFP, MOC, EOFP)
Specific power vs fn (fast) from bundle-average value at each node/time step
Other input data
The fuel rod input is based on the reload reports from the fuel vendors
FRAPCON uses only 1 value per rod for enr. and Gd wt % for Gd rods
Default values are currently used for the model options
Vattenfall’s use of FRAPCON | D Schrire |

6. Case study – Westinghouse RFA-2 mid-life case
Background – selection of 2-cycle fuel rod
High peak surface heat flux (SHF) at BOC2 (high Li)
 Verify most aggressive conditions for Li-enhanced corrosion
2AH3 one of the hottest once-burnt assemblies in core at BOC
D12 2nd hottest rod in assembly
Selected for hot cell PIE
Vattenfall’s use of FRAPCON | D Schrire |

7. Case study – Westinghouse RFA-2 mid-life case
Vattenfall’s use of FRAPCON | D Schrire |

8. Case study – Westinghouse RFA-2 mid-life case
Metallography at fuel-stack gap, maybe unrepresentative
Vattenfall’s use of FRAPCON | D Schrire |

9. Case study – Westinghouse RFA-2 EOL benchmark
Assembly ID
0AH1
0AH3
0AH5
0AH8
EOL BU (4 cycles)
53.3
53.0
Vattenfall’s use of FRAPCON | D Schrire |

10. Case study – Westinghouse RFA-2 EOL benchmark
Vattenfall’s use of FRAPCON | D Schrire |

11. Case study – Westinghouse RFA-2 EOL benchmark
Rod selected for hot cell PIE
Fresh bundle in 3rd cycle
Vattenfall’s use of FRAPCON | D Schrire |

12. Case study – Westinghouse RFA-2 EOLbenchmark
3rd and 4th cycle well above Vitanza threshold
Vattenfall’s use of FRAPCON | D Schrire |

13. Results – calculated vs measured
FGR somewhat under-predicted
 Very sensitive to LHR when above Vitanza threshold
Spread in free volume
 May be due to as-manufactured uncertainty
Vattenfall’s use of FRAPCON | D Schrire |