Using ADLAS® and Apros® successfully in licensing of large scale I&C modernisation at Loviisa Nuclear Power Plant

Loviisa NPP

Fortum’s Loviisa Nuclear Power Plant is located on the Southern coast of Finland. It has two Russian designed VVER-440 reactors, which have been in operation since 1977 and 1980.

While the major components of the plant are Russian, the I&C systems were mainly based on Siemens technologies (Simatic and Teleperm), for normal operation and safety related systems, and Russian technologies for reactor trip, rod control and neutron flux monitoring.

Description of the problem

Fortum started I&C modernisation to improve licensability and maintainability of the plant in terms of new safety I&C concept.

The goals of the project were:

1. To ensure remaining lifetime of the plant units by:

• Modernizing Reactor Trip (RT) system and Neutron Flux Measurement system based on outdated Russian relay technology and implementing backup systems for RT
• Strengthening defence in depth principle by adding backup systems and preventive protection
• Improving concept for accident management

2. To allow extension of lifetime of the plant from I&C perspective by:

• Building new sophisticated I&C concept on top plant safety architecture grounding

How it was done

Key success factors of the project:

Extensive task specification for I&C functions is based on plant-wide safety architecture created by using a comprehensive licensing approach (ADLAS®, Advanced Nuclear Licensing and Safety Design Method of Nuclear Facilities) which takes into account the features of the specific plant.

The task specification was implemented by means of a well-prepared project lifecycle model, which started with a comprehensive pre-engineering phase. Design requirements cover not only the radiation safety authority’s Nuclear specific requirements but also selected references from international standards.

Using ADLAS® also in steering the engineering and licensing activities of the project lifecycle and in the approval process with radiation safety authorities.

Comprehensive safety I&C architecture was created, but the modernization mainly concentrated on Finnish I&C Safety classes 2 and 3 (equivalent to IAEA Safety Category 1 and 2, ICE Category A and B or EUR F1A and F1B).

Using Fortum’s advanced process simulator (APROS®) in addition to normal I&C test procedure for evidence in the validation of safety I&C architecture.

Implement and validate respective changes in the control rooms and find solutions for the interface between the new digital I&C system and the old analogue actuation prioritization and switchgear.