Phenix (France)

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Phenix: 250 MW FBR

Facilities in Phenix

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The Phenix prototype breeder was switched back on May 27, after nearly three years off-line. A major rehabilitation of the 250-MW, Commissariat a l´Energie Atomique (CEA) unit is designed to allow it to run for up to 10 years, though the CEA most recently set the closure date at 2004. The CEA has permission to operate the reactor for only six months, after which it will be inspected and, if the CEA so decides, the last of three loops will be repaired to allow it to operate at full power. It is operating at 350 MW thermal.


The Commissariat a l´Energie Atomique (CEA) said that replacement of rupture disks protecting secondary sodium circuits would delay restart of the 250-MW Phenix by one to two weeks.
The incident was rated at Level 0 on INES because there were no real safety consequences and because in case of a real sodium-water reaction the second disk would have protected the installation. But the CEA said it was still considered significant because it affected part of the protection system.


Phenix had been down since April 1995, although it was being kept at a subcritical level in anticipation of restart. The CEA and co-owner EdF have invested some 400-million French francs (about $67-million) to refurbish Phenix, which is now France´s only fast reactor following the government´s decision to abandon the 1,240-MW Superphenix.


French nuclear safety agency DSIN issued an autorization for the plant to resume normal operation for about 100 fullpower days. Plant has been operating at a few MW during repairs to secondary soidium circuits and other austenitic steel components (corrosion & fatigue related cracking).


A crack over 350 mm long has been found under a weld in the secondary sodium curcuit. Cause: thermal fatigue induced by alternate flows of hotter and colder sodium at the weld. (crack is throughwall for 200 mm.)


Four days after the unit had restarted after maintenance another reactivity drop occured; due to probably another argon bubble problem, despite all the measures taken to guard against it.


Spurious scrams occured on 6.8.; 24.8 and 14.9. were found during tests to be caused by an argon bubble of 30-50 l in the core. The bubble was located in the periphery of the core where pressure is lower and void coefficient is negative. Utility tries to make sure that the bubble cannot pass into the center of the core, where the void coefficient is positive, A large enough bubble in the middle of the core could lead to a power excursion. The problem is more accute at the Superphenix , which because of its larger core has a positive void coeffficient. The argon bubble in the Phenix breeder was trapped in the core rather than being evacuated through purge assemblies located underneath the core. Investigations and experiments showed that the gas bubble is no risk for the Superphenix, said the CEA director in March 1990.