loading pattern optimisation - sfen · lp optimizer development at tractebel 28/06/2016 loading...

Confidential Restricted Public Internal

B. Vermeeren – 28 June 2016

Loading Pattern Optimization

Introduction

What is in-core fuel management?

What is loading pattern design?

What are the challenges?

LP Optimizer How does automated LP optimization work?

Development

at Tractebel How is LP Optimizer developed at Tractebel?

Outlook and

Conclusion

What will be improved?

What can we conclude?

CONTENTS

28/06/2016 LOADING PATTERN OPTIMIZATION 2

Majority of nuclear power plants are operated in cycles, requiring periodic refueling due to fuel

depletion

Cycles of a nuclear power plant are designed to…

— Maintain safety margins for controlling and shutting down the reactor (= technical requirement)

— Maximize energy production (= economical requirement)

In-core fuel management ≡ calculating core reactivity, power distribution and isotopic inventory in

order to meet these technical and economical requirements during subsequent cycles

IN-CORE FUEL MANAGEMENT Introduction


LOADING PATTERN DESIGN Introduction


Loading pattern design ≡ find a suitable

configuration of fresh and irradiated FA (= fuel

assemblies) in order to meet the needs put

forward by in-core fuel management

Conventional tool for loading pattern design

(e.g. PANACHE*): User shuffles around irradiated

and fresh FA and modifies burnable poison

content in an attempt to comply to key safety

parameters

Challenging! Multi-dimensional, time-

dependent, non-linear combinatorial problem

* distributed by ANSWERS services UK

Loading pattern optimizer ≡ tool for automated optimization of an initial LP

≡ fast scoping of large search space

Introduction





Development

at Tractebel

How is LP Optimizer developed at Tractebel?

What are the results?

Outlook and

Conclusion



CONTENTS


Loading Pattern Optimizer (LPO) is a tool associated with PANTHER* (3D diffusion code for

steady-state and transient core calculations)

Simplified geometry to reduce PANTHER* evaluation time (1/4th or 1/8th core geometry, originally

using 2D condensed neutronic data libraries)

Specialized algorithms that perform well for discrete non-linear problems with a high number of

possible combinations (simulated annealing and genetic algorithms)

Further developed by Tractebel Engie (company in charge of engineering support for Belgian utility

operator Electrabel)

LOADING PATTERN OPTIMIZER

28/06/2016 LOADING PATTERN OPTIMIZATION 6 * distributed by ANSWERS services UK

How? By using optimization algorithms (simulated annealing or genetic algorithms) that…

Move around FA in core and between core and spent fuel pool

Change burnable poison content of fresh FA

Rotate/mirror FA to optimize burnup gradients

…in an attempt to minimize the objective function ≡ function which maps the quality of a LP on a

single variable that is minimized during the optimization (e.g. max. peak power)

Loading patterns which don’t comply to user set criteria penalize the objective function:

Economical criteria (min. natural cycle length, max. number of fresh fuel FA)

Safety criteria (max. peak power, max. MTC, max. FA burnup, …)

Positional criteria (Westinghouse guidelines, no highly irradiated FA under control rod bank D, …)

AUTOMATED LOADING PATTERN EVALUATION


OBJECTIVE FUNCTION MINIMIZATION Max. peak power


1.40

1.45

1.50

1.55

1.60

0 2000 4000 6000 8000 10000 12000

Max. P

eak P

ow

er

[-]

Loading Pattern Index [-]

Introduction





Development

at Tractebel



Outlook and

Conclusion



CONTENTS


LP OPTIMIZER DEVELOPMENT AT TRACTEBEL


LP OPTIMIZER LP REPORTER

PANACHE

PANTHER

Doc, id, conversion

On-screen shuffles

Better / best LP ?

First LP ?

AUTUNITE

Simplify user experience to allow usage in a production environment

— Easy user configuration and basic means for post-processing (facilitate search queries, …)

— Tight integration in a series of computer-aided loading pattern design tools used at Tractebel Engie

Transfer from 2D condensed neutronic data libraries to 3D calculations improves accuracy



LP OPTIMIZER LP REPORTER

PANACHE

PANTHER

Doc, id, conversion

On-screen shuffles

Better / best LP ?

First LP ?

AUTUNITE



— Possible due to increased availability of high performing CPUs

— Improved reproduction of axial behavior as trade-off with respect to increased loading pattern evaluation time



Introduction of additional constraints to narrow down search space

— Limit maximum FA burnup

— Limit maximum peak power at Control Rod Insertion Limits

— Penalizing of objective function for specified combinations of FA positions and/or irradiation histories

— Accounting for Westinghouse guidelines for reshuffling of FA while optimizing burnup gradients (prevent

aggravation of in-core power tilt)





1.41

1.42

1.43

1.44

1.45

1.46

1.47

1.48

1.49

1.50

16200 16400 16600 16800 17000 17200 17400 17600 17800

Ob

jecti

ve F

un

cti

on

– M

ax.

Peak P

ow

er

[-]

Natural Length [MWd/tU]



1.41

1.42

1.43

1.44

1.45

1.46

1.47

1.48

1.49

1.50

16200 16400 16600 16800 17000 17200 17400 17600 17800

Ob

jecti

ve F

un

cti

on

– M

ax.

Peak P

ow

er

[-]

Natural Length [MWd/tU]

large variety of

suitable

loading pattern

candidates

Optimization constraints:

Max. peak power ≤ 1.46

Max. MTC ≤ −2 pcm/°C

Max. # fresh FA ≤ 56

Min. natural cycle length ≥ 16.8 GWd/tU

Max. FA burnup ≤ 55 GWd/tU

No violation of Westinghouse guidelines

No highly irradiated FA under control

bank D

Introduction





Development

at Tractebel



Outlook and

Conclusion



CONTENTS


Further improvement of user experience (e.g. library of preset configurations, direct visualization

of LPs)

Speed up optimization time (e.g. dynamic depletion scheme, parallel LP evaluation)

Multi-cycle optimization

Implementation of mechanical guidelines for Belgian loading pattern design (e.g. avoid

unfavorable FA orientations with respect to core baffle)

PLANNED DEVELOPMENT


Loading Pattern Optimizer is a valuable new component to a series of computer-aided loading

pattern design tools at Tractebel

Generates large variety of suitable loading pattern candidates

LP Optimizer accommodates an increased demand for flexibility regarding in-core fuel

management and atypical, short-term loading pattern design

Simplified user setup allows deployment in a production environment

LP Optimizer supported a faster determination of suitable core loading pattern candidates in the

recent research for optimized restart of some of the Belgian nuclear power plants

CONCLUSION


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