TRITON11™ – 11×11 BWR Fuel Design - ats-fns.fi

Westinghouse Non-Proprietary Class 3 © 2016 Westinghouse Electric Company LLC. All Rights Reserved.

1

November 2-3, 2016 Uffe Bergmann, Design Lead

Westinghouse Electric Company LLC

TRITON11™ – 11×11 BWR Fuel Design Improving Fuel Economy

TRITON11™ is a trademark or registered trademark of Westinghouse Electric Company LLC, its affiliates and/or its subsidiaries in the United States of America and may be registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited. Other names may be trademarks of their respective owners.

2


Outline • Introduction

• Westinghouse BWR Fuel Evolution

• TRITON11 Fuel Design – Nuclear & Thermal Hydraulic Performance

– Materials

– Mechanical Design Features

• Development Status

• Summary

3


Introduction • Today, low electricity prices and taxes on nuclear production

put strong economic pressure on the utilities • Reducing fuel cycle cost makes an important contribution to

the overall cost savings – Increased focus on back-end cost as solutions to final storage

are being investigated and realized. Limited storage and transport capacities make cost incremental per fuel assembly.

• In response, Westinghouse has developed a new 11×11 BWR fuel design called TRITON11 which allows – more efficient use of uranium through better thermal margins – fewer fresh assemblies loaded (improved back-end) – more operational flexibility (e.g. extended load follow, 12 vs 24

month cycles)

4


BWR Fuel Evolution • High fuel reliability is provided through long evolution of

robust materials and proven mechanical design solutions – Important reliability features of SVEA-96 Optima3 fuel are

maintained

SVEA-96 Optima2

2000 2008

SVEA-96 Optima3TRITON11

2018

Main driver: Economy EconomyReliability

5


Reasons for going to 11×11 • Significant gains in thermal margins enable more efficient core

designs with reduced bundle enrichments • Allow increased axial power peaking

– more efficient Pu-239 conversion and better reactivity control, hence reduced BA

– increasing bottom/top blankets to reduce axial neutron leakage

• Allow increased radial power peaking – fresh and once-burned assemblies to be

loaded further inside the core, reducing radial neutron leakage

• Allow more operational flexibility

6


Reasons for going to 11×11 • Conclusion: Further improving fuel efficiency requires better

thermal margins • This can only be achieved by increasing the number of fuel

rods, thereby reducing the linear heat generation rate (LHGR) and surface heat flux (CPR)

• An 11×11 design was found to be optimum when weighing performance benefits against added cost and complexity

Optimum found among many conceptual designs covering 10x10, 11x11, 12x12, non-square

7


Abandoning the SVEA Channel Concept • SVEA channel concept is abandoned when moving to 11×11

– Needed to overcome pressure drop restriction from requirement of thermal hydraulic stability, when adding more fuel rods

– A symmetric cross does not fit in the (uneven) 11×11 lattice • Transition to standard channel with features of enhanced performance

– Lower section of standard “thick-thin” type – Upper section uniformly “thin” with increased inner square dimension

• Reduces parasitic neutron absorption and 2-phase pressure drop – Insignificant channel bow and less creep deformation ensured by use of

Low Tin ZIRLO™ material

Low Tin ZIRLO™ is a trademark or registered trademark of Westinghouse Electric Company LLC, its affiliates and/or its subsidiaries in the United States of America and may be registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited. Other names may be trademarks of their respective owners.

Lower section Upper section

SVEA Channel TRITON11 Channel

8


Optimized Moderation Conditions • Varying number of Water Rods (WRs) studied: 1, 2, 3, 4, …

– Circular water tube preferred to square channel due to improved manufacturability and improved mechanical strength

• More than 4 (smaller) WRs excluded since WRs become transparent to neutrons • 4 WRs is optimum for hot condition (reactivity, power peaking) but cold reactivity

(Shutdown Margin - SDM) is too difficult to handle • 3 WRs is optimum for hot-cold reactivity swing when part-length rods (PLRs) are

clustered in the center – Dispersion of moderator away from center also reduces power peaking

• 2 WRs with sufficient area not feasible in 11×11 square lattice

3 WRs uniquely adapted to 11×11 lattice, leading to more

homogenous and more efficient moderation

9


TRITON11 Fuel Lattice Design • 11x11 Cartesian, 3 WRs • 109 fuel rods

– 10 short (1/3) PLRs – 8 longer (2/3) PLRs

• U weight increased – Ideal for power uprates, back-end capacity

limitations, and long cycle applications • SDM improved by clustering of 1/3 PLRs between

WRs to obtain over-moderation in cold condition – Efficient ”flux trap”

• Nuclear heating coefficient (ITC) late in cycle controlled (limited) by positions of 2/3 PLRs

• Pin power peaking / CPR optimized by positions of WRs and 2/3 PLRs

• 2-phase pressure drop (thermal hydraulic stability) optimized by number of PLRs of each type

• High flexibility in positioning of burnable absorber rods 2/3-length rod

1/3-length rod

Water rod

Full-length rod

Design parameters mutually optimized to give highest performance and flexibility under current and anticipated operational conditions

10


Nuclear and Thermal Hydraulic Performance Reference: SVEA-96 Optima3 • Similar parasitic neutron absorption

– Important benefit of light spacers maintained (worth ~0.04 wt% enr.) • Improved SDM

– Important for 24 month cycles and/or high burnup • Reduced pin power and burnup peaking

– Higher burnup can be reached (within 4.95 wt% enr. limit) • 10% reduction of LHGR

– Supports increased “spectral shift” operation • Significant improvement of Critical Power Ratio (CPR) expected

based on 5 scoping tests in FRIGG loop – Supports lower leakage core design

• Uranium weight significantly increased – Loading fewer fresh bundles gives more flexibility in core design and

reduces back-end cost

TRITON11 provides savings of $3-4M /reload (24 month cycle)

11


Materials • Known materials used • HiFi™ material for fuel rod cladding

– Reduced hydrogen uptake – Successful Westinghouse ZrSn-liner maintained to provide

additional PCI margin for increased operational flexibility • Low Tin ZIRLO material for channel and WR cladding

– High dimensional stability, low hydrogen pickup, corrosion resistant – Ensures predictably low differential growth between channel and

WRs and a robust load chain (via lift in WRs)

HiFi™ is a trademark or registered trademark of Westinghouse Electric Company LLC, its affiliates and/or its subsidiaries in the United States of America and may be registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited. Other names may be trademarks of their respective owners.

0

2

4

6

8

10

12

14

0 20 40 60 80

Chan

nel G

row

th [m

m]

Equivalent Channel Burnup [MWd/kgU]

Low Tin ZIRLO

Low Tin ZIRLO (2015)

-15

-10

-5

0

5

10

15

0 20 40 60 80

Chan

nel B

ow [m

m]

Equivalent Channel Burnup [MWd/kgU]

Low Tin ZIRLO

Low Tin ZIRLO (2015)

3 mm = 120 mills No acceleration

12


Mechanical Design Features • WRs are connected to top handle and bottom tie plate, hence

constituting the load bearing structure of the fuel bundle, and include features to prevent spacer grids from moving axially – Redundancy in load chain provided by safe lift in two WRs – Tie rods and spacer capture rods eliminated, hence no external

forces on fuel rods • Full-size Triple Wave+™ debris filter attached to inlet nozzle

Triple Wave+™ is a trademark or registered trademark of Westinghouse Electric Company LLC, its affiliates and/or its subsidiaries in the United States of America and may be registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited. Other names may be trademarks of their respective owners.

Bottom tie plate Top handle

Robust mechanical design

13


Mechanical Design Features • Same sleeve type spacer design as

SVEA-96 Optima3 – Enhanced debris failure resistance – Unmatched structural strength, proven by

lateral load cycling test (lower photo) – Unmatched neutron economy – Low pressure drop

• Spacer frame further optimized for enhanced debris resistance

• Mixing vane features further optimized for improved dryout performance

TRITON11 fuel can be transported inside channel

14


Development Status

• TRITON11 fuel product is in final stage of testing and validation prior to insertion of Lead Test Assemblies (LTAs) – T/H tests, Mechanical tests, manufacturing trails, field service

tests, transport qualification etc. ongoing

– LTA licensing package being prepared

– A rigorous design review process is followed, involving global Westinghouse and utility expertise

• Major upgrade of FRIGG loop hardware and software completed to serve full-scale dryout testing – First 11×11 test currently on-going

First LTAs to be inserted in 2018

15


Installation of 11×11 Test Bundle in FRIGG Loop

16


Summary • TRITON11 is designed to meet the growing demand for utility

cost reductions by being – the most efficient and most reliable BWR fuel of the future

• Potential savings of $3-4M /reload (24 month cycle) • SVEA channel concept abandoned • Huge effort spent in finding optimum fuel geometry to provide

maximum economic benefits and highest operating flexibility • Proven materials with known benefits utilized • Most assembly components already proven in previous

designs • LTAs scheduled for 2018

TRITON11 - worth waiting for!

Documents

TRITON11™ – 11×11 BWR Fuel Design - ats-fns.fi