Cracks spark nuclear alarm

PUBLISHED : Sunday, 28 March, 1993, 12:00am
UPDATED : Sunday, 28 March, 1993, 12:00am

DANGEROUS cracks that could lead to a nuclear meltdown have been discovered in French nuclear powerplants identical to the reactors built at Daya Bay, according to an independent report commissioned by Greenpeace International.

Electricite de France (EDF), technical advisers to the Guangdong plant, have also admitted the material used for the tubes in pressurised water reactors (PWRs) in which cracks have appeared is ''posing problems'' at French reactors.

The EDF admission comes days after a seminar in the territory in which the French power company tried to reassure medical specialists that Hongkong residents need not evacuate the territory or even take shelter in a ''worst-case scenario'' accident.

Iconel 600, the alloy identified as problematic, is used to make the cover sleeves which hold the control rods responsible for safely shutting down the reactor.

The Greenpeace report, put together by a group of German nuclear engineers and a member of the Paris-based nuclear think-tank, said EDF scientists had discovered vertical and horizontal cracks in the tubes holding the control rods.

According to the report released yesterday, vertical cracks could lead to a leak that could be controlled but horizontal cracks could result in a catastrophic nuclear accident.

Laboratory tests conducted by metallurgists last December revealed horizontal cracking had begun back in 1991 when the first instance of vertical cracks were discovered.

But the EDF denied this and rejected Greenpeace claims that it had underestimated or ignored the problem of vertical cracks, which it said posed no threat to safety.

As of March 15, EDF inspections had identified problems in 13 of the 17 reactors they had examined. The vessel heads of at least 12 reactors had been replaced, and some cracked sleeves have been fitted with a system to detect future possible leaks.

The Greenpeace investigating team found Iconel 600 highly susceptible to cracking and an EDF spokesman Mr Jean Pierre Chaussade agreed the material had been identified as ''posing problems''.

''It is not a great problem. The cracks we have discovered are in plants that are about 12 years old. It is a very slow phenomenon, which we can monitor and check every year when we shut down the units for maintenance and inspection,'' he said.

Mr Chaussade said an alternative alloy, Iconel 690, was considered the strongest alternative by the international scientific community, but said it needed at least five years more development.

Mr Dominic Tai, spokesman for the Daya Bay Hongkong Nuclear Investment Co (HKNIC), said the findings by Greenpeace and the EDF were not urgent matters and said they would wait and see.

''All the cracks in France are vertical and this is a very important point. If they were horizontal, there might be a chance of possible ejaculation of the control rods which would leave a hole and lead to an accident, but there are no horizontal lines, so there is no danger,'' Mr Tai said.

He admitted there was a possibility the Daya Bay reactors could develop vertical cracking, but said the phenomenon also related to stress and temperature, and would take years.

''We are keeping ourselves briefed on the progress in France. The inspection and remedial action is continuing and we are closely monitoring the situation.

''We believe the situation in France is under control. There may or may not be similar cracking at Daya Bay. There is no reason for us to take drastic action because it is not a matter of urgency,'' Mr Tai said.

''France will have its inspection programme completed by the end of this year. We can learn from their experience and will basically follow French practice, and make changes if EDF advises us to.'' Legislator and environmentalist the Reverend Fung Chi-wood has expressed concern. ''It is because of these kinds of problems that we think the nuclear industry is inherently unsafe,'' he said.

''The cracking of tubes may cause an uncontrollable meltdown of nuclear core. If we cannot stop the plant opening, I would want the tubes to be changed whenever cracks are observed.

''That is the real worry. How do you know how fast the cracks are going to develop? No one knows when they might go too far. It does not matter how slight the danger is. It is too much.'' Mr Fung said reassurances were ''total nonsense'', adding that a US Government report said there would be deaths within a 70 km radius of an accident at a reactor like the one being built in Daya Bay.

A Greenpeace spokesman also accused the nuclear industry of a cover-up. ''Once again, the nuclear industry is misleading the public. This is an independent report commissioned by Greenpeace and put together by two reputable and respected bodies,'' he said.

''They would not have said horizontal cracking had begun if it had not.''