Experience of TVSA fuel implementation at Kozloduy NPP
21st Symposium of AER on VVER Reactor Physics and Reactor Safety (2011, Dresden, Germany)
Core design, monitoring and fuel management
Abstract
The base design of the Russian fuel assemblies TVSA have been under operation at
Kozloduy NPP WWER-1000 reactors since 2004. The old type fuel assemblies TVS-M were
gradually substituted till 2008. The TVSA assembly distinguishes itself with much stronger construction. As a burnable absorber it has a mixture of uranium and uniformly distributed Gd in 6 or
more fuel rods. This enables to increase the safety and effectiveness of fuel cycles.
The experience gained during TVSA fuel implementation on units 5 and 6 and KASKAD
code package validation was presented at the 8th International Conference on WWER Fuel Performance, Modelling and Experimental Support in 2009.
Additional information about TVSA fuel implementation at Kozloduy NPP WWER-1000
units in a 4-year fuel cycle with 42 and 48 fresh fuel assemblies reloading scheme is presented in
the paper.
1. INTRODUCTION
At the end of 2008 the transition process from the old Russian designed TVS-M fuel assemblies to the advanced TVSA fuel type was accomplished at Kozloduy NPP. The old fuel type
had to be changed because of a distortion tendency observed several years ago. The TVSA assembly distinguishes itself with much stronger construction. As a burnable absorber it has a mixture of
uranium and uniformly distributed Gd in 6 or more fuel rods. This enables to increase the safety and
effectiveness of fuel cycles. In the last few years the operational strategy for WWER-1000 units is
about 320 days in full power operation and ~ 45 days of annual outage.
The experience gained during TVSA fuel implementation at Kozloduy NPP units 5 and 6
was presented at the 8th International Conference on WWER Fuel Performance, Modelling and Experimental Support in 2009. The paper presented there mainly paid attention on the KASKAD code
package validation process against the relevant experimental data 1.
Additional information about TVSA fuel implementation at Kozloduy NPP WWER-1000
units in a 4-year fuel cycle with 42 and 48 fresh fuel assemblies reloading scheme is presented in
the paper.
2. TVSA FUEL CYCLES AT KOZLODUY NPP
2.1. Codes used
The modified Russian code package KASKAD 2 mainly consists of the 3D nodal diffusion code BIPR-7A and the 2D pin-by-pin diffusion code PERMAK-A. It has been used for core
design and neutron-physics calculations of WWER-1000 reactors since 2009 at Kozloduy NPP. Its