System for passively dissipating heat from the interior of a nuclear reactor containment structure

A system (10) for passively dissipating heat from the interior space (50) of a nuclear reactor (2) containment structure (3,6), wherein said containment structure (3,6) comprises a basement (70), side walls (71,73) and at least one top wall (4,7), the system comprising a first heat exchanger (15,15') placed outside the containment structure (3,6), a second heat exchanger (25) placed inside said reactor containment structure (3,6), said first and second heat exchangers (15,25) being fluid connected to each other in a closed loop circuit (28) by pipes (23,24) containing a thermal carrier fluid and being passed through said containment structure (3,6), and a chimney (14) the top whereof is in communication with the external atmosphere, characterized in that,

• said system (10) includes a pool (11) filled with water to a predetermined level (9), being associated with said containment structure (3,6), and positioned close to its top wall (4,7);
• said first heat exchanger (15,15') is submerged under the water in the pool (11) and extends vertically from a base (75), adjacent to the bottom (74) of the pool (11), to a top portion (76) to divide it into two fluid interconnected regions (11a,11b);
• said pool is provided with a covering (90) defining first (12) and second (13) ducts, each overlying a respective one of the regions (11a,11b) formed by the first vertical heat exchanger (15,15') and being only connected to said respective region (11a,11b);
• one (12) of the ducts being communicated to an outside air intake (81), and the other (13) being communicated to said chimney (14);
• and
• the interconnection of said ducts (12,13) being inhibited by the water present in the pool (11) when filled to said predetermined level (9).