Fissures in the reactor vessel of the Doel 3 reactor in Belgium were discovered using ultra-sound during inspections in June and July. The cracks possibly date back to the reactor's construction some 40 years ago by Dutch RDM (Rotterdamse Droogdok Maatschappij), which is no longer in business. Restart of the reactor after the regular scheduled inspections has been delayed. The shutdown for outage (with fuel discharged from the reactor) has been extended.
Every 12 to 18 months Belgian nuclear power stations are subjected to an inspection of their installations and repair and maintenance operations. During this outage the reactor is shut down and the core is partially refuelled. During these outage periods the so-called ‘operating’ inspections are conducted to check the good condition of the reactor vessel (mainly weld zones between vessel elements). Non-destructive ultrasound measuring techniques are used. These inspections are carried out in accordance with standards developed for metallurgy by the American Society of Mechanical Engineers (known under the name of Standards ASME XI).
At Doel 3 this outage began in June 2012. A new ultrasound measuring technique was used for the first time during that inspection over the whole surface of the Doel 3 reactor vessel. This inspection was conducted
by a specialist French firm on behalf of Electrabel. This is the first time in Belgium that the basic material of the reactor vessel was tested (elsewhere than in the weld zones). The whole wall of the reactor vessel was also inspec-ted, although the ASME XI standards only recommend inspection on sensitive components.
These first measurements revealed that further examination was necessary, which began on July 16. Numerous flaw indications (some reports say 8,000) in the basic steel material of the reactor vessel were detected in late June, in particular in the bottommost ring. These are "laminar" flaws parallel with the surface of the walls and, as such, theoretically not dangerous as they are normally not subject to stress.
Any repair to the vessel is practically impossible and, according to the FANC (Belgium’s Federal Agency for Nuclear Control) is not the option to take, because it is feared that such an operation would create new stress in the ves-sel walls, which must absolutely be avoided. A replacement of the vessel is extremely difficult (high radiation dose, etc.) and has never been done anywhere in the world.
FANC expects the following actions from the licensee:
• In-depth investigation of the original reactor vessel construction file to check whether it is a matter of design flaw.
• Metallurgical investigation to detect the cause and explanation of any potential production flaws.
• Drafting of a complete justification file in the context of a restart. It will be submitted to the competent authority for approval. This file will attempt to demonstrate that the detected flaw indications do not represent any danger for the structural integrity of the reactor vessel.
Until these issues have been satisfactorily solved no restart will be allowed, according to FANC, which has also stated that it is questionable if Doel 3 will ever be restarted.
Furthermore, the Tihange 2 reactor has been shut down on August 16 for its planned outage. It will undergo the same kind of inspections as those conducted at Doel 3, since its reactor vessel was forged by the same manufacturer (RDM) in the 1970s.
The nuclear safety authorities met on Thursday 16 August in Brussels on the initiative of the FANC. Beside delegates from the FANC, this technical meeting was attended by experts from the USA, France, Switzerland, the Netherlands, Germany, Spain, Sweden and United Kingdom. This meeting was aimed at taking stock of the situation at Doel 3. The attending safety authorities were also informed on the additional inspections asked by the FANC and its technical subsidiary Bel V. Furthermore, this international contact made it possible to share expertise on reactor vessel integrity and inspections. The purpose of the technical meeting was to give in-formation on the situation at Doel 3 and not to make a decision about its future, according to the FANC press release. A second meeting of the nuclear safety authorities will be held in October, to discuss the outcome of the additional investigations at Doel 3, which will be completed at the end of September.
Meanwhile, the Belgium government anticipated a longer shutdown of both Doel 3 and Tihange 2 and promised there will be no blackouts if the stay shut during the winter. Just a few weeks earlier a new phase-out plan was confirmed (see Nuclear Monitor 753, 3 August). According to that schedule Doel 1 and 2 will be closed in 2015, Doel 3 is planned to be closed in 2022 and Tihange 2 in 2023.
As said, RDM built (or took part in the construction of) a total of 22 reactor vessels (see box) during 1960-1984 when it ceased operations. Van Veen, a manager during that time admitted later, RDM had no clue how to built reactor vessels and it was a process of learning while doing: quality control, for instance was an unknown concept in submarine construction, their core-business at the time.
But press reports from that time show that cracks were not an unfamiliar phenomena. The reactor vessel of the Dutch Borssele reactor was found to have cracks and delivery was delayed in 1971. Now, the Dutch nuclear safety authority (KFD) state that there are no cracks at the Borssele reactor vessel, for many reasons, but that they will look further into it. In 1979, three years before startup, cracks were found at the Doel 3 and Tihange 2 vessels, according to press reports at the time. The cracks are confirmed during additional examinations in 1981, but reactors are allowed to start up in 1982. Striking detail: head of Doel 3 construction at Electrabel at the time was De Roovere, now head of FANC.
NPPs with RDM reactor vessel (type, start-up date)
Argentina: Atucha-1* (PWR; 3-1974)
Belgium: Doel-3 (PWR, 6-1982); Tihange-2 (PWR, 10-1982)
Germany: Brunsbuettel** (BWR, 7-1976), Philippsburg-1** (BWR, 5-1979)
Netherlands: Borssele (PWR, 7-1973), Dodewaard** (BWR, 10-1968)
Spain: Santa Maria de Garona (BWR, 10-1971), Cofrentes (BWR, 10-1984)
Sweden: Ringhals-2 (PWR, 8-1974)
Switzerland: Leibstadt (BWR, 5-1984), Muehleberg (BWR, 7-1971)
United States: Catawba-1 (PWR, 1-1985), McGuire-2 (PWR, 5-1983), North Anna-1 (PWR, 4-1978), North Anna-2 (PWR, 8-1980), Quad Cities-1 (BWR, 4-1972), Sequoyah-1 (PWR, 7-1980), Sequoyah-2 (PWR, 12-1981), Surry-1 (PWR, 7-1972), Surry-2 (PWR, 3-1973), Watts Bar-1 (PWR, 2-1996)
* There is some uncertainty about the Atucha-1 RPV, it is removed from the OECD-list on August 26, after a denial that it was constructed at RDM by the nuclear regulatory commission of Argentina. However, other sources (like the German Jahrbuch der Atomwirtschaft, edition 1971 and 1972, available at the Laka library) state clearly some involvement of RDM.
** NPP Dodewaard, Bruensbuttel en Philippsburg are in permanent shut down
Sources: OECD/NEA, press release 16 August, updated 26 August 2012 / own research Laka Foundation.
Sources: Atoomenergie, Juli/August 1972 in Dutch, available at: www.laka.org/rdm/atoomenergie1972.pdf / Interview Van Veen RDM, in: Republiek der Kerngeleerden, CD. Andriesse 1997, in Dutch, availabe
/ FANC, Infofiche, August (updated), English version available at: www.fanc. be/nl/page/infofiche-over-de-reactor-en-het-reactorvat/1460.aspx / FANC, Press release, 16 August 2012: Doel 3: Safety Authorities Meet in Brussels / De Morgen, 23 August 2012,
Contact: Eloi Glorieux, energy campaigner Greenpeace Belgium