Objective

Background:
On August 18th, 1986, twelve metric tons of sodium escaped at 5 bar pressure in the solar plant of Almeria, Spain. The incineration, where temperatures higher than 1000 *C were reached, destroyed almost all the facility. The subsequent analysis and computations indicated that a critical factor in the extent of the damage was the sodium spraying into droplets, which amplified both the calorific power and the volume of the fire. After modelisation showed that the Creys-Malville NPP might not withstand the mixed pool/spray fire following the rupture of a large sodium pipe, in 1992 the French government ordered it to be modified.

The secondary sodium and steam-generator rooms underwent changes in order to open outlets for the highest pressure, protect the structures and supports against extreme temperature, and ascertain that the sodium would be drained quickly and that essential functions would not be lost.

Relation with Russian BN 600:
This project was set up to assess the suitability of the above mentioned approach to the BN-600 and BN-350 at NPP Beloyarsk.

Result

The suitability to the BN-600 and BN-350 NPPs of the Computer codes which have been developed to direct this work, has been verified.
For this purpose, the various steps of the project were:

• Assessing the layout of sodium circuits, sodium draining and cleaning measures, sodium leak detection system;
• Assessing fire protection systems;
• Assessing potential consequences of sodium fires in various plant rooms;
• Justification of safety aspects;
• Recommend concrete countermeasures to avoid a catastrophic scenario as in Alemeria or even worse.