vuje.sk

www.vuje.sk

Reduction of Spent Fuel Volume by

Optimisation of VVER-440 Fuel Assembly

AER Meeting, Working Group F

Liblice, Czech RepublicApril 10 – 12, 2012

Pavol ČUDRNÁKPetr DAŘÍLEKRadoslav ZAJAC

2

ContentContent

- IntroductionIntroduction – – BriefBrief HistoryHistory- StartingStarting and and BorderBorder ConditionsConditions- ResultsResults- ConclusionConclusion

Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

3

Introduction

Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

• ASFEU project (2007 - 2013), part of program R&DTitle of project: Increasing of the Slovak Republic Energy SafetyCod ITMS: 26220220077Scientific activity: Space geometry discretisation of the Gd II VVER-440 fuel assembly and discretisation influence on neutron flux distribution and impact of Gd burnup

• The solution of one of the tasks is performed by HELIOS 1.10. This code is a commercial computer code and its usage by our partner FEI STU Bratislava has been questionable.

For this reason a common office of STU & VUJE has been established in VUJE, Inc. in Trnava.

4

IntroductionBrief History of the VVER-440 Fuel Assembly in

Slovakia

•Radial profiled VVER-440 fuel assemblies: used in Slovakia since 1999- increasing of enrichment from 3.6 % U-235 to 3.82 % U-235- four year fuel cycle•Change of the 2nd generation assemblies with Gd was performed in

2006- increasing of enrichment to 4.25 % U-235 + 3.35 % Gd2O3

•The last development step is using of the 2nd generation assembly called Gd-2R (4.87 % U-235 + 3.35 % Gd2O3)- loaded last year in NPP Mochovce in the 1st Unit- five year cycle

Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

5

Starting and Border Conditions

•Aim: Optimisation of Gd-2 assembly with burnable poisons

•Optimisation Basis: Gd-2 assemblies (4.25 % U-235 + 3.35 % Gd2O3) and Gd-2R (4.87 % U-235 + 3.35 % Gd2O3)

•All of the optimised assemblies included the same pin geometry, wrapper tube and also material composition of construction parts

•Pin enrichment and pin position in assembly was optimised only

Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

6

Starting and Border Conditions

VVER-440 Gd-2 Fuel Assembly(4.25 % U-235 + 3.35 % Gd2O3)

Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

7

Starting and Border Conditions

VVER-440 Gd-2 Fuel Assembly(4.87 % U-235 + 3.35 % Gd2O3)

Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

8

• Main Aim: optimised VVER-440 assembly without a radical construction change to find:- Assembly with maximal multiplication ability and acceptable pin power peaking

• Subjects of Calculation:1. Multiplication Coefficient for Infinite Lattice (kinf)2. Coefficient of Pin Power Peaking (kk)

Starting and Border Conditions

Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

9

Results• Several tens of fuel assembly variants have been designed:-18 of them have been chosen and analysed- Variants of assemblies have been divided into 6 groups according to composition and characteristics

Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

10

Results Achieved

Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

Burnup [MWd/tHM]

11

VVER-440 Gd-2 Fuel Assembly(4.924 % U-235 + 3.35 % Gd2O3)

Results Achieved

Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

20+

12 Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

Results Achieved

VVER-440 Gd-2 Fuel Assembly(4.792 % U-235 + 3.35 % Gd2O3)

32

13 Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

Results Achieved

VVER-440 Gd-2 Fuel Assembly(4.85 % U-235 + 3.35 % Gd2O3)

33b

14 Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly

Conclusion

• Up today: Fuel Assembly 4.792 % U-235 + 3.35 % Gd2O3

-the most flat pin power distribution-five year cycle only

• Otimisation of fuel assembly is proceeding slowly

• Six year cycle: enriched fuel >5 % U-235

• Growing burn-up reduces a spent fuel amount