"The Doel Nuclear Power Station is one of two nuclear power plants in Belgium. The plant is located on the bank of the Scheldt river, near the village of Doel in the Flemish province of East Flanders. The station is operated and majority-owned by vertically-integrated Belgian energy corporation Electrabel. EDF Luminus has a 10% stake in the two newest units. It employs 963 workers and covers an area of 80 hectares (200 acres). The plant represents about 15% of Belgium's total electricity production capacity and 30% of the total electricity generation. Nuclear energy typically provides half of Belgium's domestically-generated electricity and is the country's lowest-cost source of power.
The station is located in the most densely populated area for any power station in Europe, with 9 million inhabitants within a radius of 75 kilometres (47 mi).
The powerstation was built by a public utility Ebes which merged into Electrabel in 1990 together with Intercom and Unerg. The design of the plant was made by the Belgian engineering firm Tractebel. Doel 1 and 2 are twin units that entered commercial operation in 1975. Doel 3 entered commercial operation in 1982 and Doel 4 in 1985. Doel 1, 2 and 4 were delivered by the ACECOWEN (ACEC-Cockerill-Westinghouse) consortium. While Doel 3 was delivered by FRAMACEC (Framatome-ACEC-Cockerill).
Earthworks for Doel 5, a 1400MW reactor also known as N8 (8th nuclear reactor in Belgium), were stopped in 1988. The participation in the French twin plant in Chooz however was continued. The French industry was reimbursed for the already ordered components.
The design of the plants is reviewed completely every ten years. This so-called TJH (tienjaarlijkse herziening) is a legal obligation imposed by the Belgian state and the exploitation license of the plant. The purpose of the review is to update the plants to the most recent international safety standards.
Since the design of Doel 3 and 4 and the first TJH of Doel 1 and 2 the plants are designed to be subjected to earthquakes like the one in Zulzeke-Nukerke in 1938. With an intensity of 5.6 on the Richter scale and a distance of 75 km to the epicentre this is the most significant historic earthquake for Doel. This earthquake resulted in horizontal ground accelerations of up to 0.058g and formed the design base for Doel 1 and 2. Doel 3 and 4 were designed for peak ground accelerations of 0.1g. After the Fukushima Daiichi nuclear disaster probabilistic safety studies performed by the Royal Observatory of Belgium predicted earthquakes with peak ground acceleration of up to 0.081g every 10,000 years. The design was subsequently analysed for earthquakes up to 0.17g which is equivalent to a 1 in 100,000 year earthquake.
The Doel plant was originally designed for a 10,000 year flood of 9.13mTAW (Tweede Algemene Waterpassing). The highest measured level was 8.10mTAW during the North Sea flood of 1953. The site itself was hydraulically raised to 8,86mTAW during construction and fitted with Seadyke of 12.08mTAW. The other dykes around the site have a height of 11mTAW. Probabilistic studies performed after Fukushima showed the height of a 10,000 year flood had slightly increased to 9.35mTAW, 22 cm higher than the studies performed in the 1960s. The highest possible tsunami is lower than 0.5m. During post-Fukushima stress tests a dyke failure with a water level of 10.2m was simulated. Due to the presence of bulkheads and pedestals in the buildings no safety functions were endangered.
Besides regular primary level safety systems, in common with most nuclear power plants in the world, Doel has secondary level safety systems that can autonomously keep the power plant safe during large external accidents such as the crash of an aircraft, external explosions or loss of the primary level. The primary level systems have a redundancy of three or four times. The secondary level systems are 2x100% or 3x50%. and have their own heatsink separate from the primary heatsink, the Scheldt river. Doel 1 and 2 have aircoolers while Doel 3 and 4 have three separate artificial cooling ponds.
Nuclear plants are designed with multiple physical barriers to keep fission productions from escaping into the environment. In the case of a pressurized water reactor there are three barriers: the fuel cladding which surround the fuel pallets, the primary circuit which houses the fuel rods and finally the containment building in which the primary circuit is built. In Belgium it was decided to add an extra barrier, a so-called double containment. The primary containment, which is a steel sphere for Doel 1 and 2 and a pre-stressed concrete cylinder with steel liner for Doel 3 and 4, is surrounded by a secondary containment made of 1.2 to 1.3m thick reinforced concrete. The space between both containments is kept at sub-atmospheric pressure and filters are used to filter potential leaks of the primary containment.
Light and intermediate level waste, which represents 99% of the volume of waste, is treated on site in the WAB (water- en afvalbehandelingsgebouw) building. Category A waste with half lives of less than 30 years is transported to Belgoprocess in Dessel for surface disposal.
High level waste was originally recycled to MOX fuel, and re-used in the Doel 3 reactor. In 1993, the Belgian Federal government placed a moratorium on the reprocessing activities in order to research other options. Pending further decisions regarding this moratorium, spent fuel is stored on site in dry cask storage. Final disposal of the waste is being researched at the HADES underground laboratory 225m deep in the Boom Clay. Nuclear transmutation of the waste is also being researched with the MYRRHA project.
In October 2013, NIRAS suspended Electrabel's license to treat two types of waste, concentrate and resins, after foam was discovered on previously treated waste due to an alkali–silica reaction. Electrabel has started a licensing procedure to use the process used in Tihange to process future waste. This process can take up to two years and in the meantime the waste in question is stored on site."
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