STUK requests further clarification of the automation system design for the Olkiluoto 3 project


The Radiation and Nuclear Safety Authority Finland (STUK) has asked Teollisuuden Voima Oyj for further clarification of the overall design of automation systems for the Olkiluoto 3 nuclear power plant by 31 July 2009. This request for further clarification is related to the decision made in summer last year by STUK, in which it demanded that TVO revise the architecture of the plant’s automation systems.

In its inspections early last year, STUK observed several deficiencies in the automation system design of the Olkiluoto 3 nuclear power plant. From a safety point of view, the most significant deficiencies concerned the mutual independence of automation system components that back each other up. In July 2008, STUK issued a decision, in which it presented comments on the automation system design and demanded that TVO revise the documentation. STUK particularly emphasised the significance of the overall architecture of the automation systems.

TVO submitted a revised plan for the inspection of STUK in December 2008. Although the plan had been improved, the documents still contained weaknesses and contradictions with earlier documents. STUK asked for further clarification and, through a separate decision, presented demands for a protection system for the reactor. The reactor’s protection system is part of the key section of the automation system, the protection automation system, the function of which is to start up the plant’s safety systems in case of accident or malfunction.

In March 2009, TVO submitted a new version of the plan concerning automation system architecture. Both the automation system design and its related documentation had been improved, but they still contained deficiencies, resulting in STUK having to request for a third time greater precision and revisions. STUK is now requiring TVO for updated documents by the end of July. In addition to the documents in question, STUK has also asked TVO for further clarification concerning the validation of individual automation systems and devices.

Additional information:
Director, Lasse Reiman, tel. +358 (0)9 759 88 379
Assistant Director, Keijo Valtonen, tel. +358 (0)9 759 88 331
Information Officer, Leena Hietanen, tel. +358 (0)9 759 88 215

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