Mitsubishi Heavy Industries, Ltd. (MHI) has received an order for pressurizer nozzle spool piece replacement work on the Ringhals 3 pressurized water reactor (PWR) in Sweden.
The project is scheduled for completion in 2016.
As well as replacement work, MHI's responsibilities include technical justification, qualification tests, equipment manufacturing and material procurement.
MHI will replace six nozzle welds, including the safety and relief valve lines. The project will entail work in "a narrow, enclosed workspace subject to high radiation doses," it says.
The joints in the new spool piece will be made of Alloy 690 material, which MHI says "ensures higher corrosion resistance in high-temperature and high-pressure environments than Alloy 600 material used in the current weld joints."
MHI has complete 20 pressurizer nozzle spool piece replacements at PWRs in Japan, however this contract represents the first on-site replacement work to be performed in Europe.
The work is being carried out to reduce the risks associated with stress-corrosion cracking (SCC) of ageing materials, and thereby enhance plant reliability and operational life, according to MHI. MHI said that in recent years, many nuclear power plant operators in Japan, the US and Europe, have started to replace steam generators, reactor vessel heads, pressurizers and other related components for this reason.
The 1069 MW Ringhals 3 PWR, which began operation in 1981, is one of four reactors located at the Ringhals nuclear power plant, around 60 kilometers south of Gothenburg, Sweden.
MHI said it has previously delivered three replacement reactor vessel closure heads (RRVCHs) and replacement control rod drive mechanisms (CRDM) to Ringhals AB, which is owned by Vattenfall (70.4%) and E.ON Kärnkraft Sverige AB (29.6%).
Photo: Pressurizer diagram showing nozzle welds to be replaced (Source: MHI)