Oskarshamn 1 Nuclear Power Station.

At Sweden’s oldest nuclear power plant, Oskarshamn 1 (475 MWe), an extensive “MOD” modernization program was completed recently, enabling the 30-year-old BWR unit to operate economically for at least another 20 years.

Concept Developed by Framatome ANP

The goals of the modernization program originally defined in 1996 – namely, to extensively upgrade Oskarshamn 1 and thereby enhance plant safety – were implemented with great success. Framatome ANP developed a modernization concept whose key features included strict physical separation of redundant subsystems, greater diversity of equipment design, and independence of safety systems from those used for normal plant operation. These concepts were accepted, without changes, by the Swedish license authority and the operator. The work included the design and installation of a brand new two-train low-pressure emergency core cooling system (ECCS) and modifications to the high-pressure system for emergency core cooling to ensure consistent separation of the redundant trains as well as independence from the non-safety systems. In the future, four new bypass valves installed in parallel with the existing safety-relief valves will guarantee not only safe and reliable depressurization of the reactor but also diversity of equipment design for the reactor pressure limitation function.

Implementation of the new safety concept additionally required installation of new emergency power switchgear along with two new emergency diesel generators plus a completely new four-channel reactor protection system, provided by a different vendor based on Framatome ANP’s specifications.

Large Scope of Supply

In addition to the various system upgrades, Framatome ANP’s scope of supply also included design and erection of a new emergency control building to accommodate parts of the new ECCS, the new reactor protection system, the new emergency power switchgear and two new emergency diesels. The actual work on site took around 13 months to complete. Despite the fact that an additional order for backfitting a large pipe whip restraint – received shortly before the scheduled restart of the plant in November 2002 – led to postponement of the original restart date, Framatome ANP’s on-site personnel worked nights and weekends to ensure a return to criticality by Christmas 2002, getting the plant back on line by January 2, 2003.

Framatome ANP’s successful planning and execution of the Oskarshamn 1 modernization program further illustrates its extensive expertise for complex backfitting and modernization tasks. More than 120 engineers from various engineering disciplines were involved in the project, with team and project managers being supported by state-of-the-art project management tools and techniques.

Oskarshamn 1: A Major Energy Supplier

Oskarshamn 1 plays a major role in meeting the current high demand for electricity in Sweden and the interconnected Nordic power system. Extremely low temperatures in the region this winter created a demand for power that could not be met by hydropower plants due to below-average precipitation in the summer and fall of 2002.

Commissioning of new ECCS