More Tests Before Belgian Reactor Restart

Wednesday, February 6, 2013 @ 02:02 PM gHale


Belgian utility Electrabel now has a plan in place to conduct additional tests to determine whether they can start two of its reactors safely following the discovery of manufacturing defects in their reactor pressure vessels last year.

Officials used a new ultrasound measuring technique for the first time in June 2012 over the whole surface of the Doel 3 reactor vessel, rather than just around the weld zones. This test showed indications that “could be assimilated to potential cracks.” Additional tests confirmed the presence of these flaws, which could be manufacturing defects in the steel vessel.

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Another Belgian reactor, Tihange 2, shut down in August for a maintenance outage examinations found similar flaws as Doel 3.

The flaw indications are “little fat flakes,” with an average width of 10-15 mm and about 1 mm thick. They detected 8000 in the surface of the steel wall of the reactor vessels of Doel 3 and about 2000 in the vessel of Tihange 2. These flaws originate, officials said, from the casting and forging process when they manufactured the vessels. Both reactor pressure vessels came from the same manufacturer Rotterdam Drydock Company in the late 1970s. Investigations said these flaws have not worsened or been influenced by the subsequent operation of the units.

Prior to issuing its final decision on whether the reactors can restart, Belgium’s Federal Agency for Nuclear Control (FANC) requested Electrabel carry out additional tests and provide further information. It has asked Electrabel to perform a “load test” during which officials investigate the resistance of the reactor vessel under more severe conditions than normal operating conditions by increasing the pressure in the vessel. After these tests, they will do ultrasonic inspections to determine whether the flaw indications evolved. As well as tests on the actual reactor vessels, FANC requested tests on samples of similar steel components manufactured for the use in a nuclear power plant but never used to see if they present similar flaw indications. They will also check the mechanical strength of the samples.

Electrabel submitted a detailed action plan for conducting these tests to FANC for its approval. The company anticipates completing the tests by the end of March and will then submit the results to FANC.

The regulator said if the latest tests are conclusive, “we can recommend the government to decided in favor of a restart” of the reactors. The final restart decision, it said, rests with the government. FANC added, “It is not possible to make any predictions with regard to the timing in this respect.”

In a January 15 statement, FANC said that it “sees no elements that would have lead to a permanent shutdown of the nuclear power plants.” However, it noted, “Only when having examined all the data, FANC will be able to determine whether the safety margin is not impaired.”



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