This paper presents the activities undertaken by Kozloduy NPP to operate the units 5 and 6 beyond an established
time frame defined by the licence and the original plant design – so called Long Term Operation /LTO/ which should be
justified by safety assessment. Among the topics covered by the safety assessment, specific consideration were given to
adequate management of the ageing processes that can affect the SSCs within the scope of the evaluation for long term
operation and to ensuring that those SSCs will retain their capability to perform their intended safety functions throughout
the planned period of long term operation.
The activities for units 5 and 6 plant life extension (PLEX) were allocated into two main stages:
Stage I: Comprehensive assessment (ageing management review) and residual lifetime evaluation of the equipment and
facilities of Kozloduy NPP units 5 and 6. This stage was completed in 2012–2014.
Stage II: Implementation of Preparatory Programmes for Kozloduy NPP Units 5&6 Lifetime Extension. Regarding unit 5,
this stage was completed in 2014-2016.
The Plant Life Extension (PLEX) project final reports justify the possibility of extending the operating life of unit 5 by 30
years, i.e. to 2047.
In November 2017, the plant operating licence for unit 5 was renewed. The licence renewal period of 10 years is the maximum
as per the Bulgarian legislation.
Keywords: Long Term Operation [LTO], Ageing Management Review [AMR], Repair and Maintenance [R&M], SSCs [Structure