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Reduction of Spent
Fuel Volume by
Optimisation of VVER440 Fuel Assembly
Pavol ČUDRNÁK
Petr DAŘÍLEK
Radoslav ZAJAC
AER Meeting, Working
Group F
Liblice, Czech Republic
April 10 – 12, 2012
www.vuje.sk
Content
-
Introduction – Brief History
Starting and Border Conditions
Results
Conclusion
2
Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly
Introduction
• ASFEU project (2007 - 2013), part of program R&D
Title of project: Increasing of the Slovak Republic Energy Safety
Cod ITMS: 26220220077
Scientific 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.
3
Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly
Introduction
Brief 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
4
Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly
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
5
Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly
Starting and Border Conditions
VVER-440 Gd-2 Fuel Assembly
(4.25 % U-235 + 3.35 % Gd2O3)
6
Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly
Starting and Border Conditions
VVER-440 Gd-2 Fuel Assembly
(4.87 % U-235 + 3.35 % Gd2O3)
7
Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly
Starting and Border Conditions
• 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)
8
Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly
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
9
Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly
Results Achieved
Burnup [MWd/tHM]
10
Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly
Results Achieved
20+
VVER-440 Gd-2 Fuel Assembly
(4.924 % U-235 + 3.35 % Gd2O3)
11
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
12
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
13
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
14
Reduction of Spent Fuel Volume by Optimisation of VVER-440 Fuel Assembly
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