Sodium Fire at Cadarache
WISE-Paris, MP, MS 1 October 1998
A large sodium fire occurred on Friday 25 September 1998 in a non nuclear
installation of the Nuclear Research Center of the Commissariat à
l'Energie Atomique (CEA) at Cadarache, in the South of France.
The facility in question, operated by CEA's Institut de Protection
et de Sûreté Nucléaire (IPSN), is a test facility
where sodium is normally voluntarily ignited in order to study burning
characteristics and fire fighting options. Sodium is a solid metal which
ignites in air and reacts violently with water. Molten sodium is used
as a coolant in fast-breeder reactors. The 250 MWe demonstration Phénix
reactor is the only fast-breeder reactor currently operated in France.
The 1,200 MWe Superphénix reactor has been shut down for good.
However, the core is still in the reactor tank and the primary coolant
pumps are operated to remove residual heat and to keep the primary sodium
It is during the transfer of sodium through a test facility that the
fire started. Instead of trying to turn the fire out, IPSN staff instead
decided to let the fire burn out alone, since the fire happened in a
facility which is designed to withhold such fires. Or is it that they
realized that they would not have any chance of putting the fire out
? The building is said to be designed to withstand fires involving 70
tons of sodium ("sheet" or "layer" types of fires of sodium, which are
less violent than the "spray" types of fires).
According to IPSN, the fire is believed to be due to a non-totally
inert atmosphere in a container.
The sodium which reacted was destined to be destroyed, since the fast-breeder
technology is not to be developed anymore in France, and IPSN has now
put an end to its safety programs on the burning of sodium. IPSN still
has more than 30 tons of sodium from the testing programs to be converted
into stable soda, a slow controlled reaction between water and sodium.
According to IPSN's Gonzalez at Cadarache, only 10 to 15 kg out of
the 2 tons of sodium involved actually burnt, according to the quantity
of aerosols which were generated during the burning of the sodium. On
1 October 1998, IPSN transferred the sodium which had not burnt and
the ashes into inert storage containers.
Cadarache already had a deadly accident, on 31 March 1994, when during
the decommissioning of the demonstration fast-breeder Rapsodie, a chemical
reaction with 100 kg of sodium remaining from the cooling circuit of
the reactor led to a violent explosion. The explosion destroyed a building
and killed one operator. Four other workers were injured.
With these two accidents in mind, NERSA, owner-"operator"
of the shut-down Superphénix reactor, will have to demonstrate
particular caution during the destruction of some 6,000 tons of sodium
from the reactor, which is in this case radioactive.